WO2015179962A1 - Displacement devices and methods for fabrication, use and control of same - Google Patents
Displacement devices and methods for fabrication, use and control of same Download PDFInfo
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- WO2015179962A1 WO2015179962A1 PCT/CA2015/050157 CA2015050157W WO2015179962A1 WO 2015179962 A1 WO2015179962 A1 WO 2015179962A1 CA 2015050157 W CA2015050157 W CA 2015050157W WO 2015179962 A1 WO2015179962 A1 WO 2015179962A1
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- stator
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- currents
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
- H02K41/02—Linear motors; Sectional motors
- H02K41/03—Synchronous motors; Motors moving step by step; Reluctance motors
- H02K41/031—Synchronous motors; Motors moving step by step; Reluctance motors of the permanent magnet type
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
- H02K41/02—Linear motors; Sectional motors
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
- H02K41/02—Linear motors; Sectional motors
- H02K41/03—Synchronous motors; Motors moving step by step; Reluctance motors
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N15/00—Holding or levitation devices using magnetic attraction or repulsion, not otherwise provided for
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/06—Linear motors
- H02P25/064—Linear motors of the synchronous type
- H02P25/066—Linear motors of the synchronous type of the stepping type
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P8/00—Arrangements for controlling dynamo-electric motors rotating step by step
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/24—Pc safety
- G05B2219/24092—Warning display lights, lamps, leds on module
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/31—From computer integrated manufacturing till monitoring
- G05B2219/31469—Graphical display of process as function of detected alarm signals
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- G—PHYSICS
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- H—ELECTRICITY
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- H02K2201/00—Specific aspects not provided for in the other groups of this subclass relating to the magnetic circuits
- H02K2201/18—Machines moving with multiple degrees of freedom
Definitions
- the invention relates to displacement devices.
- Particular non-limiting embodiments provide displacement devices for use in the semi-conductor fabrication industry and for use in sample transfer for automated in-vitro diagnostics.
- Displacement devices typically comprise moveable stages which move relative to a stator and/or relative to an environment in which they are located. Displacement devices are widely used in various manufacturing, inspection, sample/part transfer, and assembly processes.
- a common solution currently in use achieves XY (i.e. planar) motion of the moveable stage using a toothed belt chain transfer system.
- Another common solution currently in uses achieves XY motion of the moveable stage by stacking two linearly moveable stages (i.e. an X-stage and a Y-stage) together via connecting bearings.
- Some generally more desirable solutions involve having one or more moveable stages capable of XY (i.e. planar) motion and, where a displacement device comprises more than one moveable stage, allowing more than one of such moveable stages to share a common working region and/or a common stator. It might be desirable for such a moveable stage to be able to provide two-dimensional programmable motion. Attempts have been made to design such displacement devices using the interaction between current-carrying coils and permanent magnets. Examples of efforts in this regard include the following: US patent No. 6,003,230; US patent No. 6,097,114; US patent No. 6,208,045; US patent No.6,441,514; US patent No. 6,847,134; US patent No.
- Figure 1 A is a schematic top view of a displacement device according to a particular embodiment.
- Figure IB is an exploded side view of a portion of the Figure 1 A a displacement device.
- Figure 2 is a top view of a displacement device which comprises a plurality of moveable stages.
- Figure 3 is a exploded partial schematic side view of a displacement device according to a particular embodiment of the invention.
- Figure 4A-4D are each a schematic top view of a 2D magnet array assembly comprising a 2D magnet array according to a particular embodiment.
- Figure 4E is a schematic top view of a displacement device incorporating a pair of moveable stages, each moveable stage comprising one of the Figure 4A magnet arrays.
- Figures 5A and 5B are each a schematic top view of a magnet array assembly comprising a plurality of ID magnet arrays according to a particular embodiment.
- Figure 5C is a cross-sectional view of an exemplary y-magnet array which is used in Figure 5A magnet array assembly and which could be used for the magnet array assemblies of Figure 5B or any of the other ID magnet array assemblies described herein.
- Figure 5D is a cross-sectional view of an exemplary y-magnet array which is used in Figure 5B magnet array assembly and which could be used for the magnet array assemblies of Figures 5A or any of the other ID magnet array assemblies described herein.
- Figures 6A-6T are cross-sectional views of exemplary y-magnet arrays which may be used in the magnet array assemblies of Figures 5A, 5B or any of the other ID magnet array assemblies described herein.
- Figure 7 is a top cross-sectional view of the Figure 3 moveable stage according to a particular embodiment showing its non- magnetic bumpers.
- Figure 8A shows a schematic top view of a stator coil assembly according to a particular embodiment which may be used in any of the displacement devices described herein.
- Figure 8B shows a schematic top view of a single layer of the Figure 8A stator coil assembly according to a particular embodiment, where the individually controllable coil traces in each excitation region all have the same orientation.
- Figure 8C shows a schematic top view of a single layer of the Figure 8A stator coil assembly according to a particular embodiment, where the individually controllable coil traces in each excitation region have different orientations.
- Figures 9A-9D each show schematic depictions of portions of coil traces in a corresponding excitation region according to a particular embodiment.
- Figure 10 is a schematic depiction of an excitation region which forms part of a working region associated with a stator coil assembly according to an example embodiment.
- Figures 11 A and 1 IB respectively depict cross-sectional views of the same magnet array assembly supported by a non-magnetic stage support structure and an iron-based stage support structure.
- Figure 12 is a schematic partial cross-sectional view of a stator bearing layer which comprises a restrictor layer and can be used to create an air bearing according to a particular embodiment.
- Figure 13 A shows a schematic block diagram of a control system suitable for use in controlling any of the displacement devices described herein according to a particular embodiment.
- Figure 13B shows one possible connection scheme to connect a plurality of y- coil traces in one coil trace layer within an excitation region according to a particular embodiment.
- Figures 13C and 13D respectively schematically depict an x-trace layout in a first layer and a y-trace layout in a second layer of an exemplary excitation region according to a particular embodiment.
- Figures 13E and 13F show a pair of stator-z direction configurations for coil layers according to a pair of exemplary embodiments.
- Figure 13G shows a number of first control signals according to a particular embodiment.
- Figure 14A shows a partial schematic illustration of a n p -phase coil layout in an x- trace layer of an excitation region according to a particular embodiment.
- Figure 14B shows the current waveforms x , ij x as a function of desired stator-y location y r for a moveable stage according to particular embodiment.
- Figure 15 A shows amplitude A x and phase ⁇ ⁇ impulses for an x-current phase h x according to a particular embodiment.
- Figure 15B shows a series of amplitude A x and phase ⁇ ⁇ impulses for an x-current phase 3 ⁇ 4 according to a particular embodiment.
- Figure 15C shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse is applied to the x-current phases 3 ⁇ 4 before a second amplitude impulse is applied to the y-current phases i jy .
- Figure 15D shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse is applied to the x-current phases 3 ⁇ 4 before a second amplitude impulse is applied to the y-current phases i jy .
- Figure 16A is a schematic depiction of how a one-by-one initialization process may be used to determine an initial location of a moveable stage in a displacement device according to a particular embodiment.
- Figure 16B depicts an alignment device according to another embodiment which may be used with the displacement device and the one -by-one initialization process of Figure 16A.
- Figure 16C schematically depicts a displacement device comprising a stator and a plurality of moveable stages which uses a group initialization technique for determining the initial positions of the moveable stages according to a particular embodiment.
- Figure 17A schematically depicts shows the working region of a stator divided into a plurality of excitation regions according to an example embodiment.
- Figure 17B
- FIG. 17A schematically depicts a moveable stage suitable for use with the Figure 17A stator.
- Figures 17C-17H depict schematic top views of motion patterns of a plurality of moveable stages (like the one of Figure 17B) relative to a stator (like the one of Figure 17A) according to particular embodiments.
- Figures 18A-18F schematically illustrate one exemplary embodiment of a process of a number of the Figure 17B moveable stages 10 ungrouping from one another.
- Figures 19A-19G schematically depict a technique for implementing rotational motion of a moveable stage about a stator-z oriented axis according to a particular embodiment.
- Figures 20A and 20B respectively depict the generation of y-current phases ij y and x- current phases which may be used to achieve controllable 360° rotation about a stator-z oriented axis according to a particular embodiment.
- Figure 21 A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment.
- Figures 21B-21K illustrate possible coil traces and corresponding current phases ij y driven therein to operate the Figure 21 A magnet array assembly to achieve controllable rotation.
- Figure 22A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment.
- Figures 22B-22F illustrate possible coil traces and corresponding current phases ij y driven therein to operate the Figure 22A magnet array assembly to achieve controllable rotation.
- Figure 23A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment.
- Figures 23B-23F illustrate possible coil traces and corresponding current phases ij y driven therein to operate the Figure 23A magnet array assembly to achieve controllable rotation.
- Figure 24 depicts another exemplary embodiment showing a displacement device of any of the types described herein used for another particular application.
- the stator comprises a plurality of electrically conductive coils shaped to provide pluralities of generally linearly elongated coil traces.
- the electrically conductive coils may be shaped to provide a first plurality of coil traces which are generally elongated in a stator-x direction and a second plurality of coil traces generally elongated in a stator-y direction which may be generally orthogonal to, or otherwise non-parallel to the stator-x direction.
- the first and second pluralities of coil traces may be provided in portions of first and second layers. The portions of the first and second layers may be located at the same stator-z location or at different stator-z locations. Portions of layers at different stator z- locations may overlap each other in the stator-z direction.
- a first portion of a first layer comprises a plurality of coil traces generally elongated in the stator-x direction and a stator-z direction overlapping first portion of a second layer comprises a plurality of coil traces generally elongated in the stator-y direction; and a second portion of the first layer comprises a plurality of coil traces generally elongated in the stator-y direction and a stator-z direction overlapping second portion of the second layer comprises a plurality of coil traces generally elongated in the stator-x direction.
- the moveable stage may be controllably moveable relative to the stator within two-dimensional working region.
- Each moveable stage may comprise one or more magnet arrays. In some embodiments,
- each magnet array comprises a plurality of magnetization segments, where each magnetization segment has a corresponding magnetization direction.
- Each magnet array may comprise at least two magnetization segments with different magnetization directions.
- One or more amplifiers may be connected to drive a plurality of currents in the plurality of electrically conductive coils.
- a controller may be connected to deliver signals to the one or more amplifiers. The signals may be used to control current driven by the one or more amplifiers into at least some of the plurality of coil traces and to thereby cause the moveable stage to track a desired position in the working region - e.g.
- x r is a desired position of the moveable stage in the stator-x direction
- y r is a desired position of the moveable stage in the stator-y direction.
- the desired position (x r ,y r ) is a function of time, t, and represents where a moveable stage should be ideally located at each time, t.
- the currents controllably driven into the at least some of the plurality of coil traces create magnetic fields which cause
- the magnetic forces associated with the interaction between the magnetic fields created by the currents in the at least some of the coil traces and the magnetic fields associated with the magnet arrays may attract the moveable stage toward the stator at all times when the controller is controlling the currents driven by the one or more amplifiers.
- the magnetic fields associated with the magnet arrays may push the moveable stage away from the stator to balance gravitational forces with an air gap at all times when the controller is controlling the currents driven by the one or more amplifiers.
- a pair of coordinate systems - a stator coordinate system which is fixed to the stator (e.g. to stator 30 of Figure 1 A); and a stage coordinate system which is fixed to the moveable stage (e.g. moveable stage 10 of Figure 1 A) and moves with the moveable stage relative to the stator and the stator coordinate system.
- This description may use conventional Cartesian coordinates (x, y, z) to describe these coordinate systems, although, it will be appreciated that other coordinate systems could be used.
- the directions e.g.
- stator-x, y, z directions in the stator coordinate system and the directions in the stage coordinate system may be shown and described as being coincident with one another - i.e. the stator-x, stator-y and stator-z directions may be shown as coincident with stage-x, stage-y and stage-z directions, respectively. Accordingly, this description and the associated drawings may refer to directions (e.g. x, y, and/or z) to refer to directions in both or either of the stator and stage coordinate systems.
- the moveable stage e.g. moveable stage 10
- the stator e.g. moveable stage
- stator 30 such that these stator and stage directions are no longer coincident with one another.
- this disclosure may adopt the convention of using the terms stator-x, stator-y and stator-z to refer to directions in the stator coordinate system and the terms stage- x, stage-y and stage-z to refer to directions in the stage coordinate system.
- the symbols Xm, Ym and Zm may be used to refer respectively to the stage-x, stage-y and stage-z directions
- the symbols Xs, Ys and Zs may be used to refer respectively to the stator-x, stator-y and stator-z directions
- the symbols X, Y and Z may be used to refer respectively to either or both of the stage-x, stage-y and stage-z and/or stator- x, stator-y and stator-z directions.
- the stage-z and stator-z directions are approximately in the same direction (e.g. within ⁇ 30° in some embodiments; within ⁇ 10° in some embodiments; and within ⁇ 2° in some embodiments).
- stator-x and stator-y directions are non-parallel. In particular embodiments, the stator-x and stator-y directions are orthogonal. In some embodiments, the stage-x and stage-y directions are non-parallel. In particular embodiments, the stage-x and stage-y directions are orthogonal.
- Figures 1A and IB respectively depict a schematic partially cutaway top view and side cross-sectional views of a displacement device 50 according to a particular embodiment of the invention.
- Displacement device 50 comprises a stator 30, a moveable stage 10, a controller 60 and one or more amplifiers 70.
- Stator 30 comprises a stator coil assembly 35 which comprises at least the traces of a plurality of electrically conductive coils 31.
- Electrically conductive coils 31 may be shaped to provide a first plurality of coil traces 32A, 32B, 32C (collectively, first coil traces 32).
- Coil traces 32 may be distributed over at least a portion of a first layer 40 at a corresponding first stator-z location and generally elongated in the stator-x direction.
- Electrically conductive coils may also be shaped to provide a second plurality of coil traces 34A, 34B, 34C
- second coil traces 34 distributed over at least a portion of a second layer 42 at a corresponding second stator-z location and generally elongated in a stator-y direction.
- first coil traces 32 may be referred to herein as x-coil traces 32 or x- traces 32 and second coil traces 34 may be referred to as y-coil traces 34 or y-traces 34.
- stator-x elongation direction of first coil traces 32 is orthogonal to the stator-y elongation direction of second coil traces 34. This is not necessary.
- first coil traces 32 are merely non-parallel to second coil traces 34.
- stator 30 comprises a pair of layers and corresponding first and second pluralities of coil traces 32. 34.
- stator 30 may comprise additional layers and corresponding additional pluralities of coil traces which may be elongated in the stator-x direction, the stator y- direction or other suitable directions.
- the two dimensional space over which coil traces 32, 34 overlap one another in the stator-z direction may define a working region 36 over which moveable stage 10 is moveable relative to stator 30.
- the span of working region 36 in the stator-x and stator-y directions may be larger than moveable stage 10 (and may be much larger than moveable stage 10) to permit moveable stage 10 to move within working region 36, although this is not necessary.
- FIG. 1 shows only portions of a relatively small number of traces 32, 34 and it is understood that coil traces 32, 34 in each corresponding layer 40, 42 may be distributed throughout their respective layers 40, 42 so that coil traces 32, 34 and/or layers 40, 42 may overlap in the stator-z direction at all locations in working region 36.
- Some of coil traces 32, 34 may be connected at their ends to form a two-phase, three-phase, or multiple -phase winding configuration as described in more detail below.
- working region 36 is a two-dimensional space, this description may describe working region 36 as a feature of stator 30, for convenience.
- Moveable stage 10 comprises a magnet array assembly 16 which comprises one or more magnet arrays 12.
- Magnet array assembly 16 should be understood to comprise the combination of the one or more individual magnet arrays 12.
- Each magnet array 12 may comprise a corresponding plurality of magnetization segments 14A, 14B, 14C, 14D ...
- moveable stage 10 comprises a first magnet array 12 having a plurality of corresponding first magnetization segments 14.
- Moveable stage 10 may be located immediately adjacent to and may bear against stator 30.
- moveable stage 10 comprises a stage bearing surface 24 that is generally planar (with a normal in the stage-z direction) and which bears against a generally planar stator bearing surface 26 (with a normal in the stator-z direction). Accordingly, when operating with this configuration, stage bearing surface 24 is generally parallel to the planes of stator layers 40, 42 in which coil traces 32, 34 are located.
- Displacement device 50 comprises one or more amplifiers 70 which are connected (e.g. with suitable electrical connections (not expressly shown in Figure 1)) to drive a plurality of currents into coil traces 32, 34.
- Amplifier(s) 70 are controlled by controller 60.
- Controller 60 (and components thereof) may comprise hardware, software, firmware or any combination thereof.
- controller 60 may be implemented on a programmed computer system comprising one or more processors, user input apparatus, displays and/or the like.
- Controller 60 may be implemented as an embedded system with a suitable user interface comprising one or more processors, user input apparatus, displays and/or the like.
- Processors may comprise microprocessors, digital signal processors, graphics processors, field programmable gate arrays, and/or the like.
- Controller 60 may be connected (e.g. with suitable electrical connections (not expressly shown in Figure 1)) to deliver signals to amplifier(s) 70. Controller 60 may be configured (e.g. using suitable software, logic configuration and/or the like) to use those signals to control the currents driven by amplifier(s) 70 into at least some of first coil traces 32 and at least some of second coil traces 34 to thereby cause moveable stage 10 to track a desired position within working region 36 - e.g.
- x r is a desired position of moveable stage 10 in the stator-x direction
- y r is a desired position of moveable stage 10 in the stator-y direction.
- displacement device 50 is shown with a single moveable stage 10.
- displacement device 50 may comprise a plurality of moveable stages, each of which may be similar to moveable stage 10 and each of which may be controlled by controller 60 using amplifier(s) 70 to drive currents in coil traces 32, 34 as described herein.
- Figure 2 shows a top view of displacement device 50', which comprises a plurality (e.g. two) moveable stages 10A, 10B.
- displacement device 50' may be substantially similar to the Figure 1 displacement device 50.
- Figure 2 also shows that moveable stages 10A, 10B need not be aligned with one another and so each moveable stage 10A, 10B may be described using its own corresponding stage coordinate system.
- the stage directions X m i/Y m i/Z m i define the stage coordinate system for moveable stage 10A and the stage directions Xm2 Ym2 Zm2 define the stage coordinate system for moveable stage 10B.
- Displacement device 50' can be built to operate with any suitable number of moveable stages 10. In some embodiments, displacement device 50' comprises three moveable stages. In some embodiments, displacement device 50' may comprise dozens to hundreds of moveable stages. In some embodiments still, displacement device 50' may comprise thousands of moveable stages.
- Figure 1 provides a general embodiment of displacement device 50.
- displacement device 150 is a particular embodiment of displacement device 50.
- Displacement device 150 comprises a moveable stage 110, which is a particular embodiment of moveable stage 10, a stator 130, which is a particular embodiment of stator 30 and so on.
- displacement device 250 is a particular embodiment of displacement device 50 that comprises a moveable stage 210, which is a particular embodiment of moveable stage 10, a stator 230 which is a particular embodiment of stator 30 and so on.
- FIG 3 is an exploded partial schematic side view of a displacement device 150 according to a particular embodiment of the invention.
- Displacement device 150 comprises a moveable stage 110 and a stator 130.
- moveable stage 110 is shown exploded (i.e. spaced apart) from stator 130. In general, however, moveable stage 110 will be located immediately adjacent to and may bear on stator 130.
- moveable stage 110 comprises a stage bearing surface 124 which may be generally planar and which is parallel with and adjacent to (and may bear against) stator bearing surface 126 of stator 130, which also may be generally planar.
- displacement device may comprise more than one moveable stage 110.
- moveable stage 10 comprises a magnet array assembly 16 comprising one or more magnet arrays 12.
- Each magnet array comprises a plurality of magnetization segments 14 having corresponding magnetization directions.
- the magnetization directions of at least two magnetization segments 14 are different from one another.
- moveable stage 110 of displacement device 150 comprises a magnet array assembly 116 comprising one or more magnet arrays (not expressly shown in Figure 3) having the features of the magnet arrays 12 described herein.
- Moveable stage 110 of the Figure 3 embodiment also includes a number of optional features comprising one or more bumpers 117, stage bearing layer 118 (which provides stage bearing surface 124), one or more part holders 119, and a stage support structure 120.
- Each part holder 119 may be configured to hold a part 119A. In some applications, each part holder 119 may hold a plurality of parts 119A.
- part 119A may comprise one or more glass/plastic tubes containing biological samples.
- Stage support structure 120 may function to provide a framework to which other components of moveable stage 110 may be mounted or otherwise supported.
- Stage bearing layer 118 can be located between magnet array assembly 116 and stator 130 to provide stage bearing surface 124, which may be generally planar.
- Displacement device 50 may comprise any one or more of a variety of embodiments of magnet array assembly 16. Unless otherwise specified, embodiments of magnet array assemblies 16 shown in this document are illustrative rather than restrictive. There are many other possible permutations for each embodiment of magnet array assemblies 16. For example, the magnetization directions of the permanent magnet pieces/elements/segments (e.g. magnetization segments 14) in a magnet array assembly 16 may all be inverted (i.e. 180° changes in magnetization direction), in which case the resulting magnet array assembly 16 could still be used in a corresponding displacement device to achieve the desired motion by suitable adjustment of the corresponding currents in coil traces 32, 34 (e.g. by suitable configuration of controller 60 and/or amplifier(s) 70). Two general types of magnet array assemblies 16 are described herein for use with displacement device 50. These types of magnet array assemblies may be referred to as 2D magnet array assemblies and ID magnet array assemblies.
- a 2D magnet array assembly 16 comprises one or more 2D magnet arrays 12.
- 2D magnet arrays 12 may comprise one or more sub-arrays 21.
- Figure 4A is a schematic top view of a 2D magnet array assembly 216 A comprising a 2D magnet array 212A according to a particular embodiment.
- magnet array 212A comprises a single sub-array 221, which in turn comprises a plurality (e.g. five) magnetization segments 214A, 214B, 214C, 214D, 214E.
- Each sub-array 221 may comprise a central magnetization segment (e.g. central magnetization segment 214E in the Figure 4A embodiment) and a plurality of additional magnetization segments (e.g. additional magnetization segments 214A, 214B, 214C, 214D in the Figure 4A embodiment).
- Each additional magnetization segment 214A, 214B, 214C, 214D comprises an edge which abuts against a corresponding peripheral edge of central magnetization segment 214E.
- edge 214D-1 of additional magnetization segment 214D abuts against peripheral edge 214E-1 of central magnetization segment 214E.
- Each of magnetization segments 214A, 214B, 214C, 214D, 214E comprises a corresponding magnetization direction.
- Central magnetization segment 214E may have a first magnetization direction opposed to a second magnetization direction of additional magnetization segments 214A, 214B, 214C, 214D.
- the letter N indicates that central magnetization segment 214E has its magnetic north pole facing out of the page (and magnetization direction in the positive Zm direction) and the letters S indicates that additional magnetization segments 214A, 214B, 214C, 214D have their magnetic south pole facing out of the page (and magnetization direction in the negative Zm direction). Note that this convention is used throughout this description and the accompanying drawings.
- the magnetization directions of each of the magnetization segments 214 in the Figure 4A sub-arrays 221 could be reversed (i.e. have its magnetization direction changed by 180°) with suitable adjustment of controller signals and/or control algorithm(s).
- a stage-x dimension (i.e. a length in a stage-x direction) of sub-array 221 may be generally equal to a spatial period ⁇ 3 ⁇ 4 and a stage-y dimension of sub-array 221 may be generally equal to a spatial period ⁇ ⁇ .
- the significance of spatial periods ⁇ ⁇ ⁇ ⁇ is explained in more detail below.
- These spatial periods ⁇ ⁇ ⁇ ⁇ may be the same as the spatial periods of the currents driven in coil traces 32, 34.
- the stage-x and stage y-dimensions (e.g. ⁇ ⁇ and ⁇ ⁇ ) of sub-array 221 are generally equal to one another. This is not necessary. In general, the stage-x and stage y-dimensions (e.g. ⁇ 3 ⁇ 4 and Xy) of sub-array 221 may be different from one another.
- Figure 4B is a schematic top view of a 2D magnet array assembly 216B comprising a 2D magnet array 212B according to a particular embodiment.
- magnet array 212B comprises a plurality (e.g. four) of sub-arrays 221A, 221B, 221C, 221D (collectively sub-arrays 221).
- Each of sub-arrays 221 is substantially similar to sub-array 221 of Figure 4A.
- each of sub-arrays 221 comprises at least one edge (e.g. one or a pair of edges), each of which abuts against a corresponding edge of a different one of sub-arrays 221.
- each sub-array 221 may comprise a single edge which abuts against a corresponding edge of another sub-array 221.
- sub-arrays 221 may not have abutting edges.
- each sub- array 221 and its corresponding magnetization segments 214 may be separately fabricated. This is the case in the illustrated embodiment of Figure 4B.
- magnetization segments 214 having a unitary construction may be shared between sub-arrays 221.
- magnetization segments 214AC (of sub- array 221 A), 214BB (of sub-array 221B), 214CA (of sub-array 221C) and 214DD (of sub- array 22 ID) may be fabricated from a single unitary magnet.
- the magnetization directions of each of the magnetization segments 214 in the Figure 4B sub- arrays 221 could be reversed (i.e. have its magnetization direction changed by 180°).
- the stage-x dimension of each sub-array 221 in magnet array 212B may be generally equal to the spatial period ⁇ ⁇ and the stage-y dimension of each sub-array 221 in magnet array 212B may be generally equal to the spatial period ⁇ ⁇ .
- the overall stage-x and stage-y dimensions of magnet array 212B are generally equal to 2 ⁇ , 2Xy respectively.
- the spatial periods ⁇ , ⁇ ⁇ of magnet array 212B are generally equal to one another, but this is not necessary.
- Figure 4C is a schematic top view of a 2D magnet array assembly 216C comprising a 2D magnet array 212C according to a particular embodiment.
- magnet array 212C comprises a single sub-array 22 ⁇ which may be substantially similar to sub-arrays 221 described herein except that the stage-x and stage-y dimensions (spatial periods ⁇ ⁇ , Xy) are different from one another.
- X x >Xy.
- a magnet array could comprise a plurality of such sub-arrays 22 ⁇ with different stage-x and stage-y dimensions (spatial periods ⁇ ⁇ , ⁇ ⁇ ).
- Figure 4D is a schematic top view of a 2D magnet array assembly 316D comprising a
- magnet array 312D according to a particular embodiment.
- magnet array 312D comprises one or more sub-arrays 321 (one of which is shown in Figure
- Each sub-array comprises a plurality (e.g. nine) magnetization segments 314A-314I and each magnetization segment has a corresponding magnetization direction.
- each sub-array 321 comprises a central magnetization segment (e.g. central magnetization segment 314E in the Figure 4D embodiment), a plurality of additional magnetization segments (e.g. additional magnetization segments 314F, 314G, 314H, 3141 in the Figure 4D embodiment) and a plurality of peripheral magnetization segments (e.g.
- each additional magnetization segment 314F, 314G, 314H, 3141 comprises an edge which abuts against a corresponding peripheral edge of central magnetization segment 314E.
- edge 314G-1 of additional magnetization segment 314G abuts against peripheral edge 314E-1 of central magnetization segment 314E.
- each peripheral magnetization segment 314A, 314B, 314C, 314D comprises an edge which abuts against a corresponding peripheral edge of a corresponding additional magnetization segment 314F, 314G, 314H, 3141.
- edge 314C-1 of peripheral magnetization segment 314C abuts against peripheral edge 314H-1 of additional magnetization segment 314H.
- each peripheral magnetization segment 314A, 314B, 314C, 314D has a corresponding peripheral magnetization direction which is opposite to the first magnetization direction of the central magnetization segment 314E and is generally orthogonal to the magnetization direction of the additional magnetization segments 314F, 314G, 314H, 3141.
- central magnetization segment 314E is magnetized in the positive stage-z direction (i.e. with its magnetic north pole facing out of the Figure 4D page)
- peripheral magnetization segments 314A, 314B, 314C, 314D are magnetized in the negative stage-z direction (i.e.
- additional magnetization segments 314F, 314G, 314H, 3141 are magnetized in directions orthogonal to the stage-z direction (i.e. in the plane of the Figure 4D page) as shown by the arrows in additional magnetization segments 314F, 314G, 314H, 3141.
- the magnetization directions of each of the magnetization segments 314 in the Figure 4D sub-array 321 could be reversed (i.e. have its magnetization direction changed by 180°).
- a stage-x dimension i.e.
- a length in a stage-x direction) of sub-array 321 may be set to be generally equal to a spatial period ⁇ ⁇ and a stage-y dimension of sub-array 321 may be set to be generally equal to a spatial period ⁇ ⁇ .
- the significance of spatial periods ⁇ ⁇ , ⁇ ⁇ is explained in more detail below.
- These spatial periods ⁇ , ⁇ ⁇ may be the same as the spatial periods of the current phases driven in coil traces 32, 34.
- the stage-x and stage y-dimensions (e.g. ⁇ ⁇ and ⁇ ⁇ ) of sub-array 321 are generally equal to one another. This is not necessary. In general, the stage-x and stage y-dimensions (e.g. ⁇ ⁇ and ⁇ ⁇ ) of sub-array 321 may be different from one another.
- the stage-x and stage-y directions may be the principal directions of magnet array 312D. Principal directions are described in more detail below.
- line AA is located in the stage-x/stage-y plane and intersects with a notional stage-z axis (not expressly shown) at the stage-x-stage-y plane geometric center of sub-array 21, magnet array 12 and/or magnet array assembly 16.
- Line AA is shown at an angle a with respect to the stage-x direction.
- the force generally orthogonal to the stage-z direction) on moveable stage 10 resulting from the interaction of the magnetic field of magnet array 12 and the magnetic field induced by the current in the notional coil trace will vary with the angle a.
- the magnitude of this force will have minimum values at approximately
- each magnet array 12 and of each sub-array 21
- This feature of the 2D magnet arrays 12 (and sub-arrays 21 of Figures 4A-4D (i.e. sub-arrays having additional/peripheral magnetization segments with peripheral edges aligned with principal directions) may be referred to as principal- aligned outlines.
- This principal-aligned outlines feature allows efficient use of working region 36 and permits a displacement device to operate with a relatively large number of moveable stages 10 compared to displacement devices having moveable stages without principal-aligned outlines.
- the central magnetization segments of the embodiments of Figures 4A-4D may be shaped to have principal direction dimensions x, y which are in a range of ⁇ 2 ⁇ 2 ⁇ and y ⁇ i ⁇ 2y. In some embodiments, the central
- magnetization segments of the embodiments of Figures 4A-4D may be shaped to have principal direction dimensions x, y which are in a range of 0.5 ⁇ 2 ⁇ 3 ⁇ and 0.5y ⁇ j ⁇ 3y.
- Figure 4E is a schematic top view of a displacement device 50 comprising a pair of moveable stages 10 each having a magnet array 212A of the type shown in Figure 4A and a stator 30 comprising x-traces 32 and y-traces 34.
- the Figure 4E displacement device 50 can achieve maximum force or maximum efficiency, when each magnet array 212A has one of its principal axes (Xm, Ym) aligned with either the stator-x direction (Xs) or the stator-y direction (Ys).
- Xm, Ym principal axes aligned with either the stator-x direction (Xs) or the stator-y direction (Ys).
- These are the preferred orientations of magnet arrays 212A (and the other 2D magnet arrays 12 of Figure 4A-4D) about the stage-z axis for each moveable stage 10, especially during relatively fast motion (e.g.
- magnet arrays 12 with principal-aligned outlines can help maximize the utilization of working region 36 and thus increase moveable stage density per unit stator area in the Xs -Ys plane.
- FIG. 4A, 4B and 4D Another property shared by the 2D magnet arrays 12 (and sub-arrays 21) depicted in Figures 4A, 4B and 4D is 90° degree rotational symmetry (e.g. after a magnet array assembly 16 oe magnet array 12 rotates by 90° about a stage-z axis (centrally located with respect to the stage-x-stage-y dimensions of the corresponding magnet array assembly 16 or magnet array 12, as the case may be), it has the same magnetic configuration as it had before the rotation).
- This property can simplify the control procedures associated with the movement of moveable stage 10, by minimizing the possible number of orientations of each magnet array 12. Otherwise, there will be two or more possible states for moveable stages 10 even when one of the principal axes (Xm, Ym) of their magnet arrays 12 is aligned with stator-x and/or stator-y directions.
- a second general type of magnet array assembly that can be used with any of the displacement devices disclosed herein is referred to as a ID magnet array assembly 16.
- a ID magnet array assembly 16 comprises one or more magnet arrays 12 and each such magnet array 12 comprises plurality of linearly elongated magnetization segments 14 (e.g. elongated in a stage-x direction or a stage-y direction), with each magnetization segment 14 having a corresponding magnetization direction that is generally orthogonal to its elongation direction. At least two of the magnetization segments 14 in each magnet array 12 may have
- a moveable stage 10 comprise a first magnet array 12 comprising a plurality of linearly elongated first magnetization segments 14 (e.g. elongated in a stage-x direction), with each first magnetization segment 14 having a corresponding magnetization direction that is generally orthogonal to the stage-x direction. At least two of the first magnetization segments 14 may have magnetization directions that are different from one another. The first magnetization directions of the first magnetization segments 14 may exhibit a first spatial period ⁇ 1 over a stage-y direction width of the first magnet array 12.
- the stage-y direction width of the first magnet array 12 is generally equal to ⁇ , so that the first magnetization directions of the first magnetization segments 14 exhibit a single first spatial period ⁇ 1 over the stage-y direction width of the first magnet array 12.
- the first magnetization directions of the first magnetization segments 14 exhibit multiple first spatial periods ⁇ 1 which repeat over the stage-y direction width of the first magnet array 12 such that the period of repetition is equal to the first spatial period ⁇ 1 .
- a moveable stage 10 comprises two magnet arrays 12. Similar to the first magnet array 12, the second magnet array 13 may comprise a plurality of linearly elongated second magnetization segments 14. However, the second magnetization segments 14 may be linearly elongated in the stage-y direction (e.g. non-parallel to the stage-x direction or generally orthogonal to the stage-x direction). Each second magnetization segment 14 has a corresponding second magnetization direction that is generally orthogonal to the stage-y direction and at least two of the second magnetization segments 14 have second magnetization directions that are different from one another. The second magnetization directions of the second magnetization segments 14 may exhibit a second spatial period ⁇ 2 over a stage-x direction width of the second magnet array 12.
- the stage-x direction width of the second magnet array 12 is generally equal to ⁇ 2 , so that the second magnetization directions of the second magnetization segments 14 exhibit a single second spatial period ⁇ 2 over the stage-x direction width.
- the second magnetization directions of the second magnetization segments 14 exhibit multiple second spatial periods ⁇ 2 which repeat over the stage-x direction width such that the period of repetition is equal to the second spatial period ⁇ 2 .
- the first spatial period ⁇ 1 is equal to the second spatial period ⁇ 2 and they may both be referred to as the spatial period ⁇ .
- a moveable stage 10 comprises four magnet arrays 12. Similar to the first magnet array 12, the third magnet array 12 may comprise a plurality of third magnetization segments 14 linearly elongated in the stage-x direction, where each third magnetization segment 14 has a corresponding third magnetization direction that is generally orthogonal to the stage-x direction and at least two of the third magnetization segments 14 have third magnetization directions that are different from one another.
- the fourth magnet array 12 may comprise a plurality of fourth magnetization segments 14 linearly elongated in the stage-y direction, where each fourth magnetization segment 14 has a corresponding fourth magnetization direction that is generally orthogonal to the stage-y direction and at least two of the fourth magnetization segments 14 have fourth magnetization directions that are different from one another.
- the third magnetization directions of the third magnetization segments 14 may exhibit the first spatial period ⁇ 1 (or a unique third spatial period ⁇ 3 ) over a stage-y direction width of the third magnet array 12.
- the stage-y direction width of the third magnet array 12 is generally equal to ⁇ 1 (or ⁇ 3 ), so that the third magnetization directions of the third magnetization segments 14 exhibit a single first spatial period ⁇ 1 (or single third spatial period ⁇ 3 ) over the stage-y direction width.
- the third magnetization directions of the third magnetization segments 14 exhibit multiple first spatial periods ⁇ 1 (or multiple third spatial periods ⁇ 3 ) which repeat over the stage-y direction width such that the period of repetition is equal to the first spatial period ⁇ 1 (or third spatial period ⁇ 3 ).
- the fourth magnetization directions of the fourth magnetization segments 14 may exhibit the second spatial period ⁇ 2 (or a unique fourth spatial period ⁇ 4) over a stage-x direction width of the fourth magnet array 12.
- the stage-x direction width of the fourth magnet array 12 is generally equal to ⁇ 2 (or ⁇ 4 ), so that the fourth magnetization directions of the fourth magnetization segments 14 exhibit a single second spatial period ⁇ 2 (or singles spatial period ⁇ ) over the stage-x direction width.
- the fourth magnetization directions of the fourth magnetization segments 14 exhibit multiple second spatial periods ⁇ 2 (or multiple fourth spatial periods ⁇ 4) which repeat over the stage-x direction width such that the period of repetition is equal to the second spatial period ⁇ 2 (or fourth spatial period ⁇ 4 ).
- the first spatial period ⁇ 1 is equal to the second spatial period ⁇ 2 and they may both be referred to as the spatial period ⁇ .
- Figures 5A and 5B respectively depict schematic top views of moveable stages 410A
- each of magnet array assemblies 416A, 416B comprise four ID magnet arrays 412A, 412B, 412C,
- magnet array assemblies 412 which include a first magnet array 412A comprising magnetization segments 414A elongated in the stage-x direction, second magnet array 412B comprising magnetization segments 414B elongated in the stage-y direction, third magnet array 412C comprising magnetization segments 414C elongated in the stage-x direction and fourth magnet array 412D comprising magnetization segments 414D elongated in the stage-y direction. Because of their elongation directions, first and third magnet arrays
- any of magnet arrays 412 in any one of magnet array assemblies 416A, 416B and/or in any one of moveable stages 410A, 41 OB may be substantially similar to one another.
- magnet array assemblies 416A, 416B and moveable stages 410A, 410B may be 90° rotationally symmetric about a stage-z oriented axis located at the stage-x-stage-y center of magnet array assemblies 416A, 416B and moveable stages 410A, 410B.
- magnet array assemblies 416A, 416B and moveable stages 410A, 410B of the Figure 4A and 4B embodiments have layouts which are similar to one another in some respects and differ from one another in other respects.
- a stage-x oriented edge of first magnet array 412A abuts against a stage-x oriented edge of second magnet array 412B (at abutment 455A)
- a stage-y oriented edge of the first magnet array 412A abuts against a stage-y oriented edge of the fourth magnet array 412D (at abutment 455B)
- a stage-x oriented edge of third magnet array 412C abuts against a stage-x oriented edge of the fourth magnet array 412D (at abutment 455C)
- a stage-y oriented edge of the third magnet array 412C abuts against a stage-y oriented edge of the second magnet array 412B (at abutment 455D).
- the peripheral edges of magnet arrays 412 are aligned with one another to provide magnet array assemblies 416A, 416B with a generally rectangular peripheral shape.
- the stage-y oriented peripheral edges of first and second magnet arrays 412 A, 412B and the stage-y oriented peripheral edges of third and fourth magnet arrays 412C, 412D are aligned with one another in the stage-y direction.
- the stage-x oriented peripheral edges of the first and fourth magnet arrays 412 A, 412D and the stage-x oriented peripheral edges of second and third magnet arrays 412B, 412C are aligned with one another in the stage-x direction.
- magnet array assemblies 16 may comprise as few as one ID magnet array 12 or a plurality of ID magnet arrays 412 which are spaced apart from one another (i.e. non- abutting), which have non-aligned peripheral edges and/or which abut one another with different abutment and/or alignment relationships.
- the stage-y oriented peripheral edges of first and second magnet arrays 412 A, 412B and the stage-y oriented peripheral edges of third and fourth magnet arrays 412C, 412D are not aligned with one another in the stage-y direction; and in some embodiments, the stage-x oriented peripheral edges of the first and fourth magnet arrays 412 A, 412D and the stage-x oriented peripheral edges of second and third magnet arrays 412B, 412C are not aligned with one another in the stage-x direction.
- the layout of magnet array assembly 416B differs from the layout of magnet array assembly 416A in that for magnet array assembly 416B, corresponding stage-y oriented edges 457A, 457C of first and third magnet arrays 412A, 412C are offset from one another in the stage-x direction (by an offset Ox) and adjacent stage-x oriented edges 459A, 459C of first and third magnet arrays 412A, 412C are spaced apart from one another in the stage-y direction (by a first space Sy) and corresponding stage-x oriented edges 457B, 457D of second and fourth magnet arrays 412B, 412D are offset from one another in the stage-y direction (by an offset Oy) and adjacent stage-y oriented edges 459B, 459D of second and fourth magnet arrays 412B, 412D are spaced apart from one another in the stage-x direction (by a second space Sx).
- the layout of magnet array assembly 416B may be advantageous (relative to the layout of magnet array assembly 416 A) because active coil traces interacting closely with magnet array 412A may generate relatively little coupling force on the magnet array 412C, and vice versa in magnet array assembly 416B as compared to magnet array assembly 416A; and active coil traces interacting closely with magnet array 412B generates little coupling force on the magnet array 412D, and vice versa in magnet array assembly 416B as compared to magnet array assembly 416A.
- the layout of magnet array assembly 416A differs from the layout of magnet array assembly 416B in that: the stage-x oriented edges of the first and second magnet arrays 412A, 412B (i.e. the stage-x oriented edges that provide abutment 455 A) have the same stage-x dimension; the stage-y-oriented edges of the first and fourth magnet arrays 412A, 412D (i.e. the stage-y oriented edges that provide abutment 455B) have the same stage-y dimension; the stage-x oriented edges of the third and fourth magnet arrays 412C, 412D (i.e.
- magnet array assembly 416A does not have a space that is analogous to space 451 of magnet array assembly 416B.
- the layout of magnet array assembly 416A may be advantageous (relative to the layout of magnet array 416B) because the magnet array assembly footprint (in the stage-x and stage-y directions) is fully utilized for magnetic field generation.
- magnet array assembly 416A the magnet array 412A that is furthest in the positive stage-x direction and furthest in the positive stage-y direction comprises magnetization segments 414A which are elongated in the stage-x direction and the other magnet arrays 412B, 412C, 412D alternate between having magnetization segments 414B, 414C, 414D elongated in the stage-y and stage-x directions.
- the magnet array 412D that is furthest in the positive stage-x direction and furthest in the positive stage-y direction comprises magnetization segments 414D which are elongated in the stage-y direction and the other magnet arrays 412 A, 412B, 412C alternate between having magnetization segments 414A, 414B, 414C elongated in the stage-x and stage-y directions.
- magnet array assemblies like magnet array assembly 416A of Figure 5 A, which have a magnet array that is furthest in the positive stage-x direction and furthest in the positive stage-y direction and which comprises magnetization segments which are elongated in the stage-x direction may be referred to as right-handed magnet array assemblies; and magnet array assemblies, like magnet array assembly 416B of Figure 5B, which have a magnet array that is furthest in the positive stage-x direction and furthest in the positive stage-y direction and which comprises magnetization segments which are elongated in the stage-y direction may be referred to as left-handed magnet array assemblies. It should be understood that many variations to magnet array assemblies 416 A, 416B can be used in moveable stages 410A, 410B. In one example, magnet array assembly 416A of Figure 5A can be changed from a right-handed to a left-handed variation. In another example, magnet array assembly 416B of Figure 5B can be changed from a left handed to a right handled variation.
- the magnet arrays 412 in magnet array assemblies 416A, 416B and moveable stages 410A, 410B may be substantially similar to one another.
- the magnet arrays 412 in magnet array assemblies 416A, 416B may have a wide variety of patterns of magnetization segments 414 (and their corresponding magnetization directions).
- This disclosure describes a number of different embodiments of 1- D magnet arrays 412, each of which could be used for magnet arrays 412 in any of the 1-D magnet array assemblies described herein (e.g. magnet arrays assemblies 416A, 416B). For brevity and convenience, except where otherwise dictated by the context, this disclosure refers to each of these ID magnet arrays using reference number 412.
- Figure 5C is a cross- sectional view of an exemplary y-magnet array 412 (e.g. array 412B) which is used in Figure 5 A magnet array assembly 416A and which could be used for the Figure 5B magnet array assembly 416B or any of the other ID magnet array assemblies described herein.
- Figure 5D is a cross-sectional view of an exemplary y-magnet array 412 (e.g. array 412B) which is used in Figure 5B magnet array assembly 416B and which could be used for the Figure 5 A magnet array assembly 416A or any of the other ID magnet array assemblies described herein.
- each magnet array 412 comprises a plurality of magnetization segments 414, each of which has a corresponding magnetization direction (where the magnetization directions of magnetization segments 414 are indicated by arrows). While the magnet arrays 412 of Figures 5C and 5D are y-magnet arrays, it will be appreciated that x-magnet arrays may be provided by merely altering the orientations of the illustrated magnet arrays and that the description of magnet arrays 412 described herein should be understood to apply to y-magnet arrays 412 or x-magnet arrays 412 with adjustment of orientation, as appropriate.
- magnet arrays 412 shown in Figures 5A and 5B exhibit a number of similar properties.
- the magnetization directions of magnetization segments 414 are orthogonal to the elongation directions of magnetization segments 414. At least two of magnetization segments 414 of each magnet array 412 are different from one another.
- the magnetization directions of magnetization segments 414 exhibit a spatial period ⁇ ⁇ over the stage-x width of magnet arrays 412.
- the spatial periods ⁇ ⁇ are shown as ⁇ without loss of generality.
- the stage-x direction width (W mx ) of magnet array 412 is generally equal to ⁇ ⁇ , so that the magnetization directions of magnetization segments 414 exhibit a single spatial period ⁇ ⁇ over the stage-x direction width of magnet array 412.
- the magnetization directions of magnetization segments 414 are mirror symmetric relative to a plane of symmetry (extending in the stage-y and stage z-directions and passing through the stage-x direction center of magnet array 412 indicated by lines 441 shown in Figures 5C and 5D).
- the stage-x direction widths of each magnetic segment 414 is generally equal to one of— or— .
- the stage-x direction widths of each magnetic segment 414 is generally equal to one of— or— .
- the edge magnetization segments 414' i.e. magnetization segments 414' at the edges of arrays 412 have stage-x direction widths (— ) that are half of the stage-x
- the stage-x direction widths of each magnetic segment 414 may be generally equal to one of ⁇ or 1 ⁇ 2 where N is any positive integer.
- edge magnetization segments 414' may have stage-x direction widths that are half of the stage-x direction widths ) of the other (interior) magnetization segments 414.
- N N t (i.e. the number of different magnetization directions), as is the case in the illustrated embodiments of Figures 5C and 5D.
- the edge magnetization segments 414' have magnetization directions that are oriented in the stage-z direction (in the positive stage-z direction in the case of the illustrated embodiments).
- the stage-z directions of the magnetization segments 414 may be inverted from those shown and/or described herein.
- magnetization directions of the magnetization segments 414 are mirror-symmetric about a middle plane extending in the stage-z direction and in direction of elongation of these magnetization segments 414 and coinciding with a stage-x-stage-y center of the magnet array assembly 416.
- magnet array assemblies 416E, 416F of Figures 5A and 5B two magnet arrays 412D and 412B are elongated in the stage-y direction; in the split cross- sectional view along the line Y-Y, the magnetization patterns of magnet arrays 412B, 412D are mirror symmetric about a middle plane extending in the stage-y-stage-z directions and coinciding with a stage-x-stage-y center of the magnet array assembly 416.
- Magnet arrays 412 of Figures 5C, 5D represent examples of magnet arrays 412 which may be used to implement magnet arrays 412 of magnet array assemblies 416A, 416B of Figures 5A, 5B or any of the other ID magnet array assemblies described herein.
- Figures 6A- 6T are cross-sectional views of exemplary y-magnet arrays 412 which may be used in magnet array assemblies 416A, 416B of Figures 5A, 5B or any of the other ID magnet array assemblies described herein.
- each magnet array 412 comprises a plurality of magnetization segments 414, each of which has a corresponding magnetization direction (where the magnetization directions of magnetization segments 414 are indicated by arrows).
- the magnetization directions of magnetization segments 414 of the magnet arrays exhibit a spatial period ⁇ ⁇ over the stage-x width of magnet arrays 412. To avoid complicating the illustrations of Figures 6A-6T, the spatial periods ⁇ ⁇ are shown as ⁇ without loss of generality. While the magnet arrays 412 of Figures 6A-6T are y-magnet arrays, it will be appreciated that x- magnet arrays may be provided by merely altering the orientations of the illustrated magnet arrays and that the description of magnet arrays 412 described herein should be understood to apply to y-magnet arrays 412 or x-magnet arrays 412 with adjustment of orientation, as appropriate.
- Figure 6A shows a magnet array 412 according to an example embodiment that is substantially similar to magnet array 412 shown in Figure 5D.
- Figure 6B shows a magnet array 412 according to an example embodiment that is substantially similar to magnet array 412 shown in Figure 5C.
- the magnet array 412 shown in Figure 6C can be used to make the right handed magnet array assembly 416 shown in Figure 5A, by putting the Figure 6C magnet array 412 at the location of magnet array 412B in the Figure 5 A array assembly 416 and by putting a magnet array similar to the Figure 6C magnet array, but with the magnetization directions of each of its magnetization segments 414 inverted by 180° at the location of magnet array 412D in the Figure 5A array assembly 416.
- the magnet array 412 shown in Figure 6D can be used to make the right handed magnet array assembly 416 shown in Figure 5 A, by putting the Figure 6D magnet array 412 at the location of magnet array 412B in the Figure 5A array assembly 416 and by putting a magnet array similar to the Figure 6D magnet array, but with the magnetization directions of each of its magnetization segments 414 inverted by 180° at the location of magnet array 412D in the Figure 5A array assembly 416.
- the edge magnetization segments 414' have magnetization directions that are generally oriented in the same stage-x directions (where N m is an even integer ( Figures 6F, 6H)) and in opposing stage-x directions (where N m is an odd integer ( Figures 6E, 6G)). Further, in the embodiments of Figures 6E-6H, edge magnetization segments 414' of magnet arrays 412 have stage-x direction widths (e.g. ⁇ where N is a positive integer) that are half that (e.g. of interior magnetization segments 414. In the embodiments of Figures 6I-6L, the edge magnetization segments 414' are of the same stage-x direction width (e.g.
- N is a positive integer
- the interior magnetization segments 414 and comprise one edge magnetization segment 414' that is oriented along the stage-z direction (positive stage-z or negative stage-z) and one edge magnetization segment 414' that is oriented along the stage-x direction (positive stage-x or negative stage-x).
- edge magnetization segments 414' have magnetization directions that are either in the positive or negative stage-z direction. Further, edge magnetization segments 414' of the embodiments of 6M-6P have stage-x direction widths
- Figure 6M-6P are either mirror symmetric about a stage- y-stage-z oriented central plane 441 (where N m is an even integer ( Figures 6 ⁇ , 6P)) or mirror anti-symmetric about a stage-y-stage-z oriented central plane 441 (where N m is an odd integer ( Figures 6M, 60)).
- the characteristics of the embodiments of Figures 6M-6P allow these magnet arrays 412 to be used to construct magnet array assemblies 416 that are 90° rotationally symmetric about a stage-z oriented axis located at a stage-x-stage-y center of the magnet array assemblies 416.
- stage-x directions widths W mx Nn x (where N m is a positive integer and ⁇ ⁇ is the spatial periodicity); and (iii) edge magnetization segments 414' have stage-x direction widths ( ⁇ , where N is a positive integer) that are half of the stage-x direction widths of the other
- suitable magnet arrays 412 may comprise one or more of these 90° rotationally symmetric characteristics, but need not have all of them.
- the edge magnetization segments 414' have magnetization directions that are generally oriented in the same (e.g. positive) stage-z directions (where N m is an even integer ( Figures 6R, 6T)) and in opposing stage-z directions (where N m is an odd integer ( Figures 6Q, 6S)). Further, edge magnetization segments 414' of the embodiments of
- stage-x direction widths e.g. ⁇ where N is a positive integer
- inventions of Figure 6Q-6T are either mirror symmetric about central plane 441 (where N m is an even integer ( Figures 6R, 6T) or mirror anti-symmetric about central plane 441 (where N m is an odd integer ( Figures 6Q, 6S)).
- N m is an even integer
- Figures 6Q, 6S mirror anti-symmetric about central plane 441
- Figures 6M-6P allow these magnet arrays 412 to be used to construct magnet array assemblies 416 that are 90° rotationally symmetric about a stage-z oriented axis located at a stage-x-stage-y center of the magnet array assemblies 416.
- stage-x directions widths W mx Nm ⁇ x (where N m is a positive integer and ⁇ ⁇ is the spatial periodicity); and (iii) edge magnetization segments 414' have stage-x direction widths ( ⁇ , where N is a positive integer) that are half of the stage-x direction widths (1 ⁇ 2) of the other
- a suitable magnet array 412 may comprise one or more of these 90° rotationally symmetric characteristics, but need not have all of them.
- magnet arrays 412 which may be used in the magnet array assemblies 416A, 416B of Figure 5A, 5B or any of the other ID magnet array assemblies described herein, with potential adjustments to the individual magnet arrays 412 of such magnet array assemblies 416.
- the exemplary embodiments described in Figures 6A-6T are exemplary and non-limiting in nature and that magnet arrays 412 may be provided with other features not explicitly described herein.
- magnet arrays 412 could comprise different parameters W ⁇ , N, N m , N t and/or N z .
- magnet arrays 412 could comprise centralized non-magnetic spacers like those described in PCT publication No.
- moveable stage 110 of displacement device 150 comprises optional bumpers 117 which may protect moveable stage 110 from other moveable stages and other objects that may be introduced onto stator 30 or into working region 36.
- Bumpers 117 may be made of non-magnetic materials to protect moveable stage 110 and its magnet array assembly 116. Further bumpers 117 may prevent two or more moveable stages 110 from getting too close to one another (e.g. to a vicinity where their respective magnetization segments might attract one another and might overcome the forces caused by current controllably driven into coil traces 34). Bumpers 117 may also serve to prevent other objects with high magnetic permeability from getting too close to magnet array assembly 116. For example, in the absence of non-magnetic bumpers 117, an iron or steel washer/screw/nuts dropped onto working region 36 can be attached to magnet array assembly 116 and cause system failure.
- Figure 7 shows a top cross-sectional view of the Figure 3 moveable stage 110 according to a particular embodiment showing non-magnetic bumpers 117.
- Bumper 117 comprises four bumper elements 117A, 117B, 117C, 117D abutting respective peripheral edges of magnet array assembly 116.
- the lateral width WB of a bumper element 117A, 117B, 117C, 117D may be defined to be the narrower one of its stage-x or stage-y dimension.
- this lateral width W B is set to be generally equal to 0.45 ⁇ .
- stage support structure 20 may be fabricated from highly magnetically permeable material (e.g. with relative magnetic permeability greater than 100), such as iron, ferrite, cobalt, combinations of these materials and/or the like.
- Highly magnetic permeability helps enhance the magnetic field below (e.g. in the negative stator-z direction relative to) magnet array assembly 16, which is where the coil traces of stator 30 are located during operation.
- Figures 11 A and 1 IB respectively depict cross-sectional views of the same magnet array assembly 16 supported by a non-magnetic stage support structure 20A and an iron-based stage support structure 20B.
- Stage support structure 20B of the Figure 11B embodiment is iron-based, but other magnetically permeable materials could be used to provide this stage support structure 20B (as discussed above).
- such magnetically permeable materials may be referred to herein as back iron.
- Figures 11 A and 1 IB that the magnetic field in the case where support structure 20B comprises back iron ( Figure 1 IB) is relatively strong below (e.g. in the negative stator-z direction relative to) magnet array assembly 16 when compared to the case where support structure 20A does not include back iron.
- a stronger magnetic field generated by the permanent magnets in magnet array assembly 16 can help increase the force on moveable stage 10 under the same coil trace current conditions.
- stage support structure 20A without back iron. Such embodiments may be desirable to minimize the weight of moveable stage 10, for example.
- stage support structures 20A can be fabricated from aluminum, ceramic, carbon-fiber reinforced composite materials, combinations of these materials and/or the like. Reducing the weight of stage support layer 20A may help to minimize moveable stage inertia. Stator coil assembly
- stator 30 comprises a stator coil assembly 35 which comprises at least the traces of a plurality of electrically conductive coils 31.
- Coils 31 are shaped to provide first and second pluralities of coil traces32, 34 which are respectively elongated in non-parallel directions.
- the first plurality of coil traces 32 is orthogonal to the second plurality of coil traces 34.
- first plurality of coil traces 32 is distributed over at least a portion of a first layer 40 and generally elongated in a stator-x direction; and second plurality of coil traces 34 is distributed over at least a portion of a second layer 42 and generally elongated in a stator-y direction.
- first and second layers 40, 42 over which first and second pluralities of coil traces 32, 34 are respectively distributed may be located at different (e.g. first and second) stator-z locations, although this is not necessary and, in some embodiments, first and second layers 40, 42 may be provided in different excitation regions (described in more detail below), but at the same stator-z location.
- stator 30 may comprise additional pluralities of coil traces which may be distributed over portions of additional layers at corresponding additional stator-z direction locations.
- stator 30 may comprise a first additional plurality of coil traces (not shown) distributed over at least a portion of a first additional layer at a corresponding first additional stator-z location and generally elongated in a stator-x direction; and a second additional plurality of coil traces (not shown) distributed over at least a portion of a second additional layer at a corresponding second additional stator-z location and generally elongated in a stator-y direction.
- Additional pluralities of coil traces are not limited to being elongated in the stator-x or stator-y directions.
- stator 30 may comprise one or both of: a first additional angular plurality of coil traces (not shown) distributed over at least a portion of a first additional angular layer at a corresponding first additional angular stator-z location and generally elongated in a direction split between the positive stator-x and positive stator-y directions (e.g.
- a second additional angular plurality of coil traces (not shown) distributed over at least a portion of a second additional angular layer at a corresponding second additional angular stator-z location and generally elongated in a direction split between the negative stator-x and positive stator-y directions (e.g. at 45° clockwise around a stator-z axis from the negative stator-x direction in some embodiments).
- coil traces 32, 34 in layers 40, 42 at different stator-z locations may overlap one another in the stator-z direction.
- the two dimensional space over which coil traces 32, 34 overlap one another in the stator-z direction may define a working region 36 over which moveable stage 10 is moveable relative to stator 30.
- coil traces 32, 34 in each corresponding layer 40, 42 may be distributed throughout their respective layers 40, 42, so that coil traces 32, 34 and/or layers 40, 42 may overlap in the stator-z direction at all locations in working region 36. This is not necessary.
- coil traces 32, 34 may occupy particular excitation regions (described in more detail below) that occupy less than an entirety of a corresponding layer 40, 42. Some of coil traces 32, 34 may be connected at their ends to form a two-phase, three-phase, or multiple- phase winding configuration as described in more detail below. While working region 36 is a two-dimensional space, this description may describe working region 36 as a feature of stator 30, for convenience.
- FIG. 3 shows another embodiment of a displacement device 150 which comprises a stator 130 according to a particular embodiment.
- Stator 130 of the Figure 3 embodiment comprises a stator bearing layer 145, stator coil assembly 135, coil supporting layer 137, power electronics layer 138, and cooling layer 139.
- Stator coil assembly 135 may comprise the aforementioned coils 31 and/or coil traces 32, 34.
- Stator bearing layer 145 may overlap with stator coil assembly 135 in stator-z direction over the stator- x/stator-y span of working region 36 (not shown in Figure 3).
- stator bearing layer 145 comprises a generally planar stator bearing surface 126 which may be parallel and adjacent to (and may bear against) generally planar stage bearing surface 124 of moveable stage 110 during operation.
- stage bearing surface 124 faces the negative stator-z direction and stator bearing surface 126 faces the positive stator-z direction.
- Bearing layers 118, 145 may support moveable stage 10 in the stator-z direction, may constrain moveable stage 10 rotation about stator-x and stator-y oriented axes, may minimize friction forces in lateral (stator-x and stator-y) directions, and may minimize friction torque around axes oriented in the stator-z direction.
- Bearing layers 118, 145 may be fabricated from materials with a low coefficient of sliding friction.
- the coefficient of sliding friction (the ratio of the stator-x or stator-y direction friction force over their normal (stator-z direction) contact force) between bearing layers 118, 145 and their respective bearing surfaces 124, 126 is less than 0.2. In some embodiments, this coefficient of sliding friction is less than 0.15 and in some embodiments this coefficient of sliding friction is less than 0.06.
- one of stage bearing layer 118 and stator bearing layer 145 is fabricated from PTFE (Polytetrafluoroethylene) or PTFE doped materials, and the other of stage bearing layer 118 and stator bearing layer 145 is fabricated from metal-based material, such as stainless steel. Such combination of bearing materials results in their coefficient of friction as low as 0.04.
- both bearing layers 118, 145 are made of PTFE or PTFE doped plastic material. Bearing layers 118, 145 may be provided in the shape of film, sheet, pad, a thin layer of coating and/or the like.
- stage bearing layer 118 may comprise a very flat bearing surface 124 which may be provided using manufacturing processes such as grinding, polishing and/or the like and stator bearing layer 145 may comprise or provide a restrictor layer which may be used to create an air bearing between stage bearing layer 118 and stator bearing layer 145.
- a restrictor layer may be fabricated from porous material with a large number of small holes.
- materials which may be used to fabricate a restrictor layer include porous carbon, porous bronze, porous steel and/or the like.
- a restrictor layer may comprise a hard solid material with small holes (e.g. created by a laser drilling process) that may be used to guide high pressure air. The diameter of the pores or holes in such restrictor layers may range between less than 100 nm to a few hundreds of microns, for example.
- FIG. 12 depicts a stator bearing layer 545 which comprises a restrictor layer 553.
- Stator bearing layer 545 may be used to provide an air bearing between the stator 30 and moveable stage 10 of any of the displacement devices 50 described herein.
- Stator bearing layer 545 comprises multiple sub-layers, which define a plurality of air distribution chambers 554 and holes 555.
- the stator coil assembly 535 may be located between air distribution chambers 554 and a spacing layer 557. Holes 555 through stator coil assembly 535 may be provided by PCB vias, for example.
- High pressure air may be supplied to air chambers 554 via a suitably configured conduit 556. The high pressure air is forced out of chambers 554 via holes 555 and impinges on restrictor layer 553.
- restrictor layer 553 is porous and air flowing through its pores can create an air bearing above (in the positive stator-z direction relative to) stator bearing layer 545. As shown in the Figure 12
- stator bearing layer 545 may optionally comprise a spacing layer 557 between holes 555 and restrictor layer 553. Spacing layer 557 may provide through holes with cross- sectional areas that are larger than holes 555 for directing air from holes 555 to restrictor layer 553.
- Coil supporting layer 137 may provide mechanical support to stator coil assembly 135.
- Stator coil assembly 135 of the Figure 3 embodiment may be substantially similar to stator coil assembly 35 of the Figure 1 embodiment and may comprise coils 31 shaped to provide coil traces 32, 34 (and any additional coil traces) having features similar to those of the Figure 1 embodiment.
- Controller 60 may be connected to deliver control signals to one or more amplifiers 70 and controller 60 may be configured to use those signals to control the currents driven by amplifier(s) 70 into at least some of first coil traces 32 and at least some of second coil traces 34 to thereby cause moveable stage 10 to track a desired position within working region 36 - e.g.
- x r is a desired position of moveable stage 10 in the stator-x direction
- y r is a desired position of moveable stage 10 in the stator-y direction.
- moveable stage bearing surface 124 When in operation, moveable stage bearing surface 124 is in close proximity with (e.g. adjacent to) and generally parallel to stator bearing surface 126.
- the stator-z direction gap between moveable stage 110 and stator 130 is less than 10mm, and is typically less than lmm.
- stage bearing surface 124 of moveable stage 110 is always in contact and bears against stator bearing surface 126 of stator 30.
- the magnetic forces generated by the interaction of currents driven into coil traces 32, 34 and magnet array(s) 12 of moveable stage 30 may be controlled (e.g. by controller 60), such that moveable stage 110 is attracted toward stator 30 whenever the currents are being controllably driven into coil traces 32, 34.
- Figure 8A shows a schematic top view of a stator coil assembly 35 according to a particular embodiment which may be used in displacement device 50 (Figure 1),
- Stator coil assembly 35 comprises a plurality of excitation regions 43 A- 431 (collectively, excitation regions 43).
- excitation regions 43 are rectangular in shape.
- excitation regions 43 may have other shapes (e.g. triangular, hexagonal and/or the like).
- Each location in each of excitation regions 43 may overlap corresponding coil trace layers 40, 42 at different stator-z locations and corresponding coil traces 32, 34 (and any additional layers and additional coil traces) in the stator-z direction.
- Coil traces 32, 34 that overlap a particular one of excitation regions 43 in the stator-z direction may be said to be coil traces 32, 34 in, of, associated with or corresponding to the particular one of excitation regions 43.
- Each coil trace 32, 34 in each excitation region 43 can be excited with a controllable current, where such current may be controlled by controller 60 which may use control signals to control amplifier(s) 70 which in turn drive current into coil traces 32, 34.
- Each of excitation regions 43 may be connected to a corresponding amplifier module, which may be located in power electronics layer 138 (see Figure 3) or may be spatially separated from stator 30 and connected to coil traces 32, 34 in its excitation region 43 using suitable electrical connections.
- each excitation region 43 Currents driven into the coil traces 32, 34 in each excitation region 43 can be independently controlled. In some embodiments, two or more excitation regions 43 may share a common amplifier by connecting their corresponding coil traces in parallel or serially. It is not necessary that a particular stator coil assembly 35 comprise a plurality of excitation regions. In some embodiments, it is sufficient for a stator coil assembly 35 to have a single excitation region that spans the entire working region.
- Figure 8B shows a schematic top view of a single layer 40 of the Figure 8A stator coil assembly 35 according to a particular embodiment, where the individually controllable coil traces 32 corresponding to each excitation region 43 have the same orientation in the illustrated layer 40.
- layer 40 comprises individually controllable coil traces 32 which are elongated in the stator-x direction corresponding to each excitation region 43.
- the Figure 8 A stator coil assembly 35 may also comprise another layer 42 (not expressly shown) at another stator-z location wherein the other layer 42 comprises individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to each excitation region 43.
- the Figure 8A stator assembly could comprise additional layers similar to layers 40, 42 described above.
- Figure 8C shows a schematic top view of a single layer 40 of the Figure 8A stator coil assembly 35 according to another particular embodiment, where the individually controllable coil traces 32, 34 corresponding to each excitation region 43 have different orientations.
- layer 40 comprises individually controllable coil traces 32 which are elongated in the stator-x direction corresponding to excitation regions 43A, 43C, 43E, 43G, 431 and layer 40 comprises individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to excitation regions 43B, 43D, 43F and 43H.
- the Figure 8A stator coil assembly 35 may also comprise another layer 42 (not expressly shown) at another stator-z location wherein the orientations of the coil traces 32, 34 in each excitation region 43 are reversed.
- layer 42 may comprise individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to excitation regions 43A, 43C, 43E, 43G, 431 and layer 42 may comprise individually controllable coil traces 32 which are elongated in the stator-x direction corresponding to excitation regions 43B, 43D, 43F and 43H.
- the Figure 8A stator assembly could comprise additional layers similar to layers 40, 42 described above.
- the Figure 8A stator assembly could comprise combinations of layers of the type described with reference to Figure 8B and layers of the type described with reference to Figure 8C.
- Figures 9A-9D each show schematic depictions of portions of coil traces in one corresponding excitation region 43.
- Figure 9 A is a cross-sectional view (along a stator- x/stator-z plane) of one excitation region 43 of stator coil assembly 35 comprising a plurality of coil trace layers 40 A, 40B, 42 A, 42B (collectively, coil trace layers, 40, 42).
- each coil trace layer 40, 42 is separated from adjacent coil trace layers 42, 40 by an insulation layer 47. Insulation layer 47 prevents electrical conduction between coil trace layers 40, 42.
- Each coil trace layer 40, 42 extends in the stator-x and stator-y directions with its normal direction generally parallel to the stator-z direction.
- each coil trace layer 40, 42 comprises a plurality of coil traces which may be distributed over at least a portion of the layer and which extend in a particular stator direction (e.g. in the stator- x direction or the stator-y direction).
- Figure 9B is a schematic cross-sectional view (along a stator-x/stator-y plane) of a first coil trace layer 40A according to a particular embodiment.
- Coil trace layer 40B may have characteristics similar to coil trace layer 40A.
- Coil trace layer 40A of the Figure 9B embodiment comprises a plurality of coil traces 32A, 32B, 32C, 32A', 32B', 32C
- coil traces 32 (collectively, coil traces 32), with each coil trace 32 linearly elongated in the stator-x direction. Due to their elongation in the stator-x direction, coil traces 32 may be referred to herein as x-traces 32 and coil trace layer 40 A may be referred to as an x-trace layer 40 or an x-layer 40.
- Figure 9C is a schematic cross-sectional view (along a stator-x/stator-y plane) of a second coil trace layer 42A according to a particular embodiment. Coil trace layer 42B may have characteristics similar to coil trace layer 42A. Coil trace layer 42A of the Figure 9C embodiment comprises a plurality of coil traces 34A, 34B, 34C, 34A', 34B', 34C
- coil traces 34 (collectively, coil traces 34), with each coil trace 34 linearly elongated in the stator-y direction. Due to their elongation in the stator-y direction, coil traces 34 may be referred to herein as y-traces 34 and coil trace layer 42A may be referred to as an y-trace layer 42 or a y- layer 42.
- each x-trace 32 has a stator-y direction width W ax and adjacent pairs of x-traces 32 are spatially offset by a stator-y direction spatial pitch P cx and each y-trace 34 has a stator-x direction width of W cy and adjacent pairs of y-traces 34 are spatially offset by a stator-x direction spatial pitch P cy .
- ⁇ 2 ⁇ ⁇ is a second spatial period in a stage-x direction (as explained in more detail below) and m p is an effective number of phases in the second currents (as explained in more detail below).
- m p is an effective number of phases in the second currents (as explained in more detail below).
- the trace widths W cx and W cy are each less than the respective trace pitches P cx and P cy to avoid electric conduction between two adjacent traces.
- these differences may be relatively small (e.g. on the order of 100-400 microns in some embodiments) and may depend on the thickness of corresponding traces 32, 34 in the stator-z direction).
- x-trace layers 40 and y-trace layers 42 may be located at different stator-z locations.
- X-traces 32 in different x-trace layers 40 of one excitation region 43 may be connected in parallel or be connected in serial or be each independently driven with different power amplifier channels.
- y-traces 34 in different y-trace layers 42 of one excitation region 43 may be connected in parallel or be connected in serial or be each independently driven with different power amplifier channels.
- Figure 9D shows an embodiment of coil trace layer 49 having coil traces 33 A, 33B, 33C, 33A', 33B', 33C (collectively, coil traces 33).
- Each trace 33 of the Figure 9D coil trace layer 49 is linearly elongated along a stator direction XE, which is oriented at an angle a relative to the stator-x direction. Due to its elongation direction at an angle a relative to the stator-x axis, coil traces 33 in the Figure 7D coil trace layer 49 may be referred to as a-traces
- a-trace layer 49 may be referred to as an a-trace layer 49.
- Typical values of angle a in some embodiments are 45° and 135°, although other angles may be used.
- the trace pitch and trace width of traces 33 in a-layer 49 may have features similar to those of coil traces 32,
- current driven through the coil traces 32, 33, 34 is used to propel moveable stage 10 to a desired position.
- current driven in x- traces 32 may be used to propel moveable stage 10 along a stator-y direction to track a desired stator-y position y r ;
- current driven in y-coil traces 34 may be used to propel moveable stage 10 along a stator-x direction to track a desired stator-x position x r ;
- current driven in oc-traces 33 may be used to rotate moveable stage 10 around a stator-z oriented axis, as explained below.
- coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction may comprise coil traces 32, 34, 33 that are non-parallel with respect to one another.
- coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction may comprise coil traces that are orthogonally oriented with respect to one another. It will be appreciated that the number of coil trace layers 40, 42, 49 in stator 30 need not be limited to the four traces shown in the illustrative embodiment of Figure 9A.
- stator 30 may comprise any suitable number of coil trace layers 40, 42, 49. Further, it is not a requirement that the orientations of coil traces 32, 34, 33 in coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction be different from one another.
- One excitation region 43 may comprise one or a plurality of x-trace layers 40 and one or a plurality of y-trace layers 42. In some embodiments, it may be desired that one excitation region 43 comprises one or a plurality of x-trace layers 40, one or a plurality of y-trace layers 42, and one or a plurality of oc-trace layers 49. Coil trace layers 40, 42, 49 (and their respective coils 32, 34, 33) in one excitation region 43 may overlap with each other in the stator-z direction throughout the excitation region 43.
- one coil excitation region 43 may comprise one or more oci-coil trace layers, one or more oc 2 -trace layers, one or more 0C3- trace layers ... one or more oc r trace layers, where t is any positive integer, oci, oc 2 ... (3 ⁇ 4 are greater than or equal to 0° and less than 180°, but not equal to each other.
- FIG 10 is a schematic depiction of an excitation region 43 which forms part of a working region 36 associated with a stator coil assembly 35 according to an example embodiment.
- stator coil assembly 35 comprises an x-trace layer 40 comprising x-traces 32, a y-trace layer 42 comprising y-traces 34, an oci-trace layer 49A comprising oci-traces 33 A and an oc 2 -trace layer 49B comprising oc 2 -traces 33B.
- 0Ci is generally equal to 45° and (3 ⁇ 4 is generally equal to 135°.
- coil traces 32, 34, 33 in each coil trace layer 40, 42, 49 may be distributed throughout at least a portion of their corresponding excitation region 43 and may extend (in their corresponding extension direction) across at least a portion of their corresponding excitation region 43.
- Coil traces in coil-trace layers 40, 42, 49 of an excitation region 43 may be electrically connected at their ends to form multiple -phase (e.g. two phase, three phase or more) winding configurations.
- stator 130 comprises a coil support layer 137 for supporting coil assembly 135 and a power electronics layer 138.
- Power electronics layer 138 may comprise one or more amplifier(s) 70 connected by suitable electrical connections (not shown) to the coil traces of coil assembly 135 to provide excitation currents to the coil traces.
- amplifier(s) 70 it is not necessary that amplifier(s) 70 be located in power electronics layer 138 and amplifier(s) 70 may be located in any suitable location which can facilitate the electrical connection of amplifier(s) 70 to the coil traces in coil trace assembly 135. This configuration is shown in dashed lines in Figure 3.
- Stator 130 and/or displacement device 150 may comprise a signal interface (and
- controller 60 may comprise any suitable form of signal interface, such as a real-time network interface, fieldbus and/or the like.
- this interface between controller 60 and amplifier(s) 70 comprises an EtherCAT interface.
- Coil support layer 137 may be fabricated using highly magnetically permeable material (e.g. with relative magnetic permeability greater than 100), such as iron, ferrite, cobalt combinations of these materials and/or the like. Fabricating coil support layer 137 using magnetically permeable materials may help to increase the magnetic flux density at stator coil traces 32, 33, 34 and may thereby enhance the lateral (stator-x and stator-y) direction interaction forces associated with the interaction of the magnetic fields generated by stator 30 and by moveable stage 10. In some embodiments, coil support layer 137 may be fabricated using non-conductive materials to minimize eddy currents induced by motion of moveable stages. Non-limiting examples of non-conductive materials include plastics, ceramics, mineral-based materials, composite materials and/or the like. In some
- coil support layer 137 may be fabricated using materials with low magnetic permeability, such as aluminum, ceramics, plastic, and/or the like.
- Heat can be generated in displacement device 150.
- Such heat can come from a number of sources which may include: the currents driven into the traces of stator coil assembly 135, friction between stage bearing layer 118 and stator bearing layer 145, eddy currents in stator 30 induced by motion of moveable stage 110, electronic
- stator 130 comprises a cooling layer 139.
- Cooling layer 139 may comprise one or more cooling devices.
- Non- limiting examples of cooling devices include fans, surface area increasing heat sinks to allow air flow to carry heat away from stator 30, fluid-based cooling devices which may comprise cooling channels through which fluid coolant may flow and/or the like.
- Stator 30 and coil assembly 35 may be fabricated using one or more printed-circuit boards (PCBs).
- PCBs can be manufactured using standard PCB fabrication, flat-panel display lithography, lithography and/or similar technology known in the art to provide coils 31 and coil traces 32, 34, 33 in their respective layers 40, 42, 49.
- Insulator layers 47 may comprise FR4 core, prepreg, ceramic material and/or the like and may be fabricated or otherwise inserted between coil layers 40, 42, 49.
- One or more coil layers 40, 42, 49 may be stacked together (i.e. adjacent to one another in the stator-z direction) in a single PCB board.
- coil traces 32, 34, 33 generally elongated in the same direction (e.g.
- coil traces 32, 33, 34 generally elongated in the same direction (e.g. at different coil trace layers 40, 42, 49) are not electrically connected to one another.
- Coil traces 32, 34, 33 fabricated using PCB technology can accommodate sufficient current for controlling the motion of moveable stage 10.
- each coil trace 32, 34, 33 can be fabricated from 6 oz copper (about 200-220 ⁇ thick) or more.
- in the portions of coil trace layers 40, 42, 49 that overlap with working region 36 may comprise coil traces 32, 34, 33 which are shaped in the form of flattened strips.
- Coil traces 32, 34, 33 having such flattened strip shapes may provide good thermal conductivity.
- the inventors have confirmed (via testing) that laminated copper can carry a sustained current density of 10 A/mm with a 50°C temperature rise above ambient without using an active heat sink.
- planar layers 40, 42, 49 of coil traces 32, 34, 33 Another advantage of planar layers 40, 42, 49 of coil traces 32, 34, 33 is that the naturally stratified conductors that provide coil traces 32, 34, 33 make them ideally suitable for carrying AC current, because the self-generated alternating magnetic field can easily penetrate the conductor through top and bottom (stator-z direction facing) surfaces but generates only relatively low self-induced eddy currents.
- PCBs may be aligned side by side (e.g. in one or both of the stator-x and stator-y directions) to provide the desired stator-x and stator-y dimensions for working region 36.
- Board-to-board lateral connections (in the stator-x and/or stator-y directions) may be made at the edges by connecting pads, through-holes of edge-adjacent boards, copper wires and/or using other suitable bridging components of the like for electrically connecting conductors on adjacent PCB boards.
- bridging components may be located underneath the PCB boards (e.g.
- such bridging components may be additionally or alternatively located above the PCB boards (e.g. on the same stator-z side as moveable stage 10) or on the side(s) of the PCB boards.
- the end terminals (not shown) of coils 32, 33, 34 may be located at or near the perimeter of stator 30 for ease of wiring to amplifier(s) 70. Connecting PCBs to one another in this manner allows displacement device 50 to be easily extended in both stator-x and stator-y dimensions for various applications.
- coil traces 32, 34, 33 on stator x-y adjacent PCB boards may be serially connected to one another to reduce the number of amplifier(s) 70 for driving current through coil traces 32, 33, 34.
- coil traces 32, 33, 34 on any particular PCB board may be driven by one or more independent amplifier(s) 70 - e.g. coils 32, 33, 34 on one PCB board may be driven by amplifier(s) 70 that are different from amplifier(s) 70 which drive coils 32, 33, 34 on a stator x-y adjacent PCB board.
- independent amplifier(s) in this manner may increase the flexibility for multi-stage actuation and to reduce heat generation.
- a single PCB board may be fabricated to have a thickness (in the stator-Z direction) of up to 5 mm (or more) using available PCB technology.
- a thickness in the stator-Z direction
- multiple PCBs can be stacked together in the stator-Z direction.
- Another benefit of using PCB technology to fabricate coil assembly 35 is the possibility of deploying large numbers of low-profile sensors (such as Hall-effect position sensor, capacitive position sensors and/or the like) directly on the board.
- FIG. 13A shows a schematic block diagram of a control system 58 suitable for use in controlling any of the displacement devices 50 described herein according to a particular embodiment. Although they may be described as different embodiments, except where otherwise specifically note, control system 58 and any of the control techniques,
- Control system 58 of the Figure 13A embodiment comprises controller 60, one or more amplifier(s) 70 and stator coil assembly 35.
- Controller 60 may comprise any suitably programmed controller capable of implementing control system 58.
- Such a controller 60 (and components thereof) may comprise hardware, software, firmware or any combination thereof.
- a controller 60 may be implemented on a programmed computer system comprising one or more processors, user input apparatus, displays and/or the like.
- Such a controller 60 may be implemented as an embedded system with a suitable user interface comprising one or more processors, user input apparatus, displays and/or the like.
- Processors may comprise microprocessors, digital signal processors, graphics processors, field programmable gate arrays, and/or the like. Components of controller 60 may be combined or subdivided, and components of controller 60 may comprise sub-components shared with other components of controller 60.
- Components of controller 60 may be physically remote from one another.
- Controller 60 may be configured to control one or more amplifiers 70 (illustrated, in Figure 13 A, as power amplifier 70) to drive currents into the plurality of coil traces in coil trace assembly 35 and to thereby controllably move moveable stage 10 relative to stator 30.
- the currents in the plurality of coil traces create magnetic fields which interact with the magnetic fields of the magnet array assembly on moveable stage 10 and cause corresponding forces on moveable stage 10.
- the currents may be controlled by controller 60 such that these magnetic forces on moveable stage 10 may attract moveable stage 10 toward stator 30 (e.g. in the negative stator-z direction in the case of the illustrated embodiments) at all times when controller 60 is controlling the currents driven by the one or more amplifiers 70.
- controller 60 is shown as comprising a trajectory generator 62 which generates desired or reference positions for each moveable stage 10.
- Such reference positions may include a desired or reference stator-x position x r of moveable stage 10, a desired or reference stator-y position y r of moveable stage and, optionally, a desired rotational orientation rz r of moveable stage 10 about a stage-z oriented axis (e.g. a stage-z oriented axis through the stage-x/stage-y center of moveables stage 10).
- controller 60 also comprises a current command generator 64.
- the desired position (x r ,y r ,rz r ) of moveable stage 10 will vary over time, such that each of the reference positions x r ,y r ,rz r is a function of time and may be described herein as x r (t),y r (t),rz r (t) at a particular time, t.
- each moveable stage 10 has a unique reference trajectory.
- this description will focus on the trajectory and corresponding control of one moveable stage 10, it being understood that trajectories and control of other moveable stages 10 may be similarly implemented.
- Current command generator 64 receives the desired positions x r , y r , rz r from trajectory generator 62 and creates corresponding current control signals i r which are provided to amplifier(s) 70. It will be appreciated that current control signals i r may comprise a plurality of control signals. In response to these current control signals i r , amplifier(s) 70 drive currents i x , i y into at least some of the coil traces of stator coil assembly 35. In some embodiments, first currents i x may be driven into a first plurality of coil traces and second currents i y may be driven into a second plurality of coil traces.
- i x represents the currents driven into stator-x oriented coil traces 32 and i y represents the currents driven into stator-y oriented coil traces 34. Accordingly, the currents i x may be referred to herein as x-currents and the currents i y may be referred to herein as y-currents.
- stator coil assembly may also comprise a-oriented coil traces 33 and amplifier(s) 70 may additionally or alternatively drive currents i a into these traces 33. However, except where otherwise dictated by the context, discussion of drive currents i a is omitted for brevity from the description of motion control.
- Figure 13B schematically depicts one possible connection scheme to connect a plurality of y-coil traces 34 in one coil trace layer 42 within an excitation region 43 according to a particular embodiment.
- x- traces 32 in layer 40 may have characteristics analogous to those of y-traces 34 in layer 42.
- traces 34 shown in Figure 13B are generally elongated in the stator-y direction, there may be some terminal connections near the edges of one excitation region 43 which connect different traces 34 together. Trace terminating connections sometimes extend through one or more other layer (e.g. another layer in the stator-z direction), as shown by the dashed lines in Figure 13B.
- the current phases i jy return in the opposite direction, they effectively provide opposite waveforms, as compared to when they flow in the first direction.
- the waveforms of current phases i jy may be spatially periodic as a function of x r with spatial periods ⁇ ⁇ (also referred to herein as ⁇ 2 ) in the stator-x direction.
- the current phases i jy which are driven into adjacent traces 34 (e.g.
- the current in trace 34A has the same amplitude as the current in trace 34A', but is flowing in an opposite direction; therefore, the currents in traces 34A, 34A' are not independent and are considered as one effective current phase.
- the currents i x may be referred to as first currents i x and their corresponding current phases ikx may be referred to as first current phases ikx.
- the currents i y may be referred to as second currents i y and their corresponding current phases ij y may be referred to as second current phases ij y .
- the first currents i x comprise a plurality of first current phases, ikx, where k is an integer from 0 to n p -l representing a first phase index.
- the first phase index k may be represented as a letter, where the letter represents an integer from 0 to n p -l (e.g. A may represent 0, B may represent 1 , C may represent 2, etc.).
- the first current phases ikx may each be driven into a corresponding one of a first plurality of stage-x oriented coil traces (e.g. coil traces 32A, 32B, 32C, etc.) and may return along another corresponding one of the stage-x oriented coil traces (e.g. coil traces 32A', 32B', 32C, etc.). Phase-adjacent first current phases ikx are driven into spatially adjacent ones of at least some of the first plurality of stator-x oriented coil traces 32.
- a first plurality of stage-x oriented coil traces e.g. coil traces 32A, 32B, 32C, etc.
- Phase-adjacent first current phases ikx are driven into spatially adjacent ones of at least some of the first plurality of stator-x oriented coil traces 32.
- embodiments may be described has having n p effective first current phases ikx.
- the second currents i y comprise a plurality of second current phases, ij y , where j is an integer from 0 to m p -l representing a second phase index, where m p is the effective number of second current phases.
- the second phase index j may be represented as a letter, where the letter represents an integer from 0 to m p -l (e.g. A may represent 0, B may represent 1, C may represent 2, etc.).
- the second current phases ij y may each be driven into a corresponding one of a second plurality of stage-y oriented coil traces (e.g.
- phase- adjacent second current phases ij y are driven into spatially adjacent ones of at least some of the second plurality of stator-y oriented coil traces 34.
- Figures 13C and 13D respectively schematically depict an x-trace layout in a first layer 40 and a y-trace layout in a second layer 42 of an exemplary excitation region 43 according to a particular embodiment.
- Excitation region 43 of the illustrated embodiment of Figures 13C, 13D has a stator-x dimension of 2 ⁇ and a stator-y dimensions of 2A y . In the illustrated embodiment of Figures 13C, 13D, although this is not necessary.
- an excitation region 43 may have a stator-x dimension of ⁇ ⁇ ⁇ ⁇ and a stator-y dimension of N y y , where N x and N y can be arbitrary positive integer numbers and ⁇ may be, but need not be, the same as y .
- Stator x-trace layer 40 of the Figure 13C embodiment comprises twelve x-traces 32 with a stator-y direction pitch P cx of ⁇ ⁇ /6.
- these twelve x-traces can be driven by one three-phase amplifier; in some embodiments, these twelve x-traces can be driven by two three-phase amplifiers, for example, with each group of six adjacent x-traces independently driven by one three phase amplifier.
- Stator y-trace layer 42 of the Figure 13D embodiment comprises twelve y-traces 34 with a stator-x direction pitch P C y of ⁇ /6.
- these twelve y-traces can be driven by one three-phase amplifier; in some embodiments, these twelve y-traces can be driven by two three-phase amplifiers, for example, with each group of six adjacent y traces independently driven by one three phase amplifier.
- the x-traces 32 of layer 40 ( Figure 13B) and the y- traces 34 of layer 42 may overlap one another in the stator-z direction.
- Figures 13E and 13F show a pair of stator-z direction configurations for coil layers 40, 42 according to a pair of exemplary embodiments.
- Figure 13E depicts four trace layers alternating between x-trace layers 40A, 40B and y-trace layers 42A, 42B.
- Figure 13F depicts four trace layers in which two x-trace layers 40A, 40B are adjacent one another in the stator-z direction and two y-trace layers 42 A, 42B are adjacent one another in the stator-z direction.
- x-trace layers 40 and y-trace layers 42 may be layered in any pattern and any number of x-trace layers 40 and y-trace layers 42 may be provided. It should be noted that different excitation regions 43 may be independently driven or share common multiple phase currents.
- control system 58 may generate first and second coil trace currents i x , i y based on reference trajectory information (x r ,y r ,rz r ) and position feedback signals related to the current position of moveable stages 10.
- control system 58 may generate first and second coil trace currents i x , i y based on reference trajectory information (x r ,y r ,rz r ) without using real-time position feedback signals related to the current position of moveable stages 10.
- the first and second coil trace currents i x , i y may create corresponding traveling magnetic field waves which are locked with corresponding ones of reference trajectories y r , x r .
- a reference variable e.g.
- current command generator 64 may use reference trajectory information (x r ,y r ,rz r ) to generate three effective control signals io xr , ii xr , hxr for the first current phases h x and three effective control signals io yr , ii yr , h yr for the second current phases i jy .
- control signals (referred to generally as control signals i r ) may then be used to cause amplifier(s) 70 to generate the first and second current phases x , ij x , and y , ij y , i2y (referred to generally as current phases i j y).
- control signals i xr , i yr may have functional forms similar to first and second current phases h x , i jy or, in some embodiments, may have digitally encoded formats which otherwise specify the functional forms of first and second current phases h x , i jy . Accordingly, unless the context dictates otherwise, control signals i xr , i yr may be referred to herein interchangeably with first and second current phases h x , ij y .
- each first current phase 3 ⁇ 4 is determined based on a function F(y r ), where y r is the desired position of a moveable stage 10 in the stator-y direction in a working region 36.
- the function F(y r ) may be a spatially periodic function of y r in the stator- y direction.
- the function, F(y r ) may have the first spatial period in the stator-y direction.
- the arbitrary position o is in a first interior portion of working region 36 (i.e. more than a stator-y distance ⁇ 1 from the stator-x oriented edges of working region 36).
- F(y r ) may be a sinusoidal function of y r although F(y r ) may be another periodic function of y r .
- Figure 13G shows the three waveforms of the control signals i 0xr , ii xr , xr as a function of y r .
- control signals xr , iixr, hxr are periodic functions of y r with a spatial period of is the first magnetic spatial period in the stator-y direction, as discussed above. It should be noted that to avoid obscuring the drawing, Figure 13G refers to without loss of generality.
- Control signals xr , iixr, hxr are fed to amplifier(s) 70 and result in a corresponding current phases kx, ij x , hx, where each of current phases x , ij x , hx is driven into a spatially adjacent one of the first (e.g. stator-x oriented) coil traces.
- current phases x , ij x , hx are driven into x-coil traces 32, they may be referred to as first current phases x , ij x , hx or x-current phases.
- first current phases x , ij x , hx or x-current phases.
- a kx is the amplitude of the k phase control signal waveform in an excitation region and ⁇ ⁇ is an arbitrary offset.
- the control signals io xr , ii xr , h xr are sinusoidally periodic, a full spatial period is equivalent to 2 ⁇ radians in electrical phase angle (where the electrical phase angle ⁇ is related to a spatial distance d 2 in a second direction
- the amplitude At x is equal for all of the
- control signals i jxr and can be referred to as A x , X-current phases x , ij x , driven into at least some of the first (e.g. stator-x oriented) coil traces 32 may be amplified versions of control signals xr , ij xr , h xr and may have the same functional form as control signals xr , ij xr , h xr - In some cases the amplitudes of the x-current phases x , ij x , i2 % may be different than those of the control signals i 0xr , ii xr , i2 Xr -
- the x-current phases x , ij x may be connected to be driven into x- traces traces 32 in a manner similar to the connection of the current phases to the stator-y oriented traces shown in Figure 13B, for example.
- x-current phases x , ij x , i2 % may be driven into several spatially adjacent (e.g. in the stator-y direction) sets of x-traces 32.
- x-current phases x , ij x , i2 % may be driven into all of the x-traces 32 in this manner.
- x-current phases x , ij x , i2 % may be driven into at least some of x-traces 32. It will be appreciated from Figure 13G that these x-current phases x , ij x , i 2x will generate a stator-y direction traveling magnet field wave. This traveling magnetic field wave will move with reference trajectory signal y r . At a particular y r , the magnetic fields created by the x-current phases x , ij x , i2 % will interact with the magnetic fields associated with the magnet array assembly 16 of moveable stage 10, to create a potential energy profile (e.g.
- the minimum potential energy location (the minimum potential energy location may also be referred to as the bottom of a potential energy well or potential well).
- similar y-current phases i jy can be generated in stator-y oriented coil traces 34 to control the location of moveable stage 10 to a desired location (x r ,y r )- [0128]
- the multi-phase current phases h x are not limited to three effective phases.
- the number of effective phases n p for x-current phases h x may be any integer greater than one.
- the corresponding current phases can be sinusoidally periodic functions of y r and can have a functional form
- phase shift between adjacent current phases h x takes the general form
- Figure 14A shows a partial schematic illustration of a n p -phase coil layout in an x- trace layer 40 of an excitation region 43, with stator-x direction width of ⁇ ⁇ ⁇ ⁇ , and a stator-y direction width of N y y according to a particular embodiment. It can be seen from Figure
- phase-adjacent ones of current phases h x may be driven into spatially adjacent x- traces 32 and this pattern can be repeated for several spatially adjacent (e.g. in the stator-y direction) sets of x-traces 32.
- spatially adjacent sets of x-traces (2n p traces) can be driven with the same current phases h x .
- each set of x- traces (2n p traces) in one excitation region 43 can be independently driven with current phases 3 ⁇ 4 to allow the control of multiple moveable stages 10 independently.
- phases k x may generally have any waveform that is a spatially periodic function of y r , sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution.
- Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like.
- each second current phase i jy is determined based on a function G(x r ), where x r is the desired position of a moveable stage 10 in the stator-x direction in a working region 36.
- the function G(x r ) may be a spatially periodic function of x r in the stator-x direction.
- the function, G(x r ) may have the second spatial period in the stator-x direction.
- the arbitrary position Xo is in a second interior portion of working region 36 (i.e. more than a stator-x distance ⁇ 2 from the stator-y oriented edges of working region 36).
- G(x r ) may be a sinusoidal function of x r although G(x r ) may be another type of periodic function of x r .
- the waveforms for the control signals z, and the corresponding current phases i jy driven into y-traces 34 may be periodic signals of x r with a spatial period of where is the second magnet spatial period in the stator-x direction, as discussed above.
- Control signals z,y are fed to amplifier(s) 70 and result in a corresponding current phases i jy , where each of current phases i jy is driven into a spatially adjacent one of the second (e.g. stator-y oriented) coil traces. Because current phases i jy are driven into y-coil traces 34, they may be referred to as second current phases i jy or y-current phases.
- hyr A 2y sin ⁇ -T- 2n -— + ⁇ p y ) (3c)
- a jy is the amplitude of the /* phase control signal waveform in an excitation region and (p y is an arbitrary offset.
- p y is an arbitrary offset.
- the control signals io yr , ii yr , h yr are sinusoidally periodic, a full spatial period is equivalent to 2 ⁇ radians in electrical phase angle (where the electrical phase angle ⁇ is related to a spatial distance d- ⁇ in a first direction
- the amplitude A jy is equal for all of the control signals z,y and can be referred to as A y , Y-current phases k y , ij y , h y driven into at least some of the second (e.g.
- stator-y oriented) coil traces 34 may be amplified versions of control signals io yr , h yr , h yr and may have the same functional form as control signals io yr , h yr , h yr - In some cases the amplitudes of the y-current phases k y , ij y , h y may be different than those of the control signals k yr , h yr , h yr -
- the number of effective phases m p for y-current phases i jy may be any integer greater than one.
- the corresponding current phases can be sinusoidally periodic functions of x r and can have a functional form
- i jy A jy sin (3 ⁇ 4 27r - ; ⁇ + ⁇ p y ) (4)
- j is a phase index that varies from 0 to m p - ⁇
- a jy is the amplitude of the /* current phase waveform
- y-traces
- the y-current phases i jy may be connected to be driven into y-traces traces 34 in a manner similar to that shown in Figure 13B, for example.
- y-current phases i jy may be driven into several spatially adjacent (e.g. in the stator-x direction) sets of y-traces 34.
- y-current phases i jy may be driven into all of the y-traces 34 in this manner.
- y-current phases i jy may be driven into at least some of y-traces 34.
- spatially adjacent sets of y-traces (2m p traces) can be driven with the same current phases i jy .
- each set of y-traces can be driven with the same current phases i jy .
- (2m p traces) in one excitation region 43 can be independently driven with current phases i jy to allow the control of multiple moveable stages 10 independently.
- These y-current phases i jy will generate a stator-x direction traveling magnet field wave. This traveling wave will move with reference trajectory signal x r .
- the magnetic fields created by the y- current phases i jy will interact with the magnetic fields associated with the magnet array assembly 16 of moveable stage 10, to create a potential energy profile (e.g. a well) which has a local minimum when stage 10 is located at the stator-x location x r , thereby trapping moveable stage 10 at the desired stator-x location x r .
- the spatially periodic functions F p (y r ) and G p (x r ) are angularly periodic functions with first and second angular periods equal to 2 ⁇ (e.g. sinusoidal functions) such that, as a function of y r , each x-current phase, in a particular one of x- traces 32 is out of phase with one or more adjacent x-current phases h x in one or more spatially adjacent ones of x-traces 32 by a first electrical angular phase difference 2 ⁇ ⁇ and, as a function of x r , each second current phase, 3 ⁇ 4, in a particular one of the y-traces 34 is out of phase with one or more adjacent y-current phases i jy in one or more spatially adjacent y- traces 34 by a second electrical angular phase difference 2n/m p .
- 2 ⁇ e.g. sinusoidal functions
- the x-current phases and y-current phases i jy are driven into corresponding coil traces 32, 34 over at least a portion of the working region 36.
- the x- and y-current phases ij y are driven into
- the x- and y-current phases 3 ⁇ 4 are driven into corresponding traces 32, 34 over a portion of an excitation region 43 or over more than one excitation region 43.
- the x- and y-current phases ij y are driven into as few as two x-traces 32 and two y-traces 34.
- the amplitudes A kx of x-current phases h x controls the strength or magnitude of the magnetic field corresponding to the k th x-current phase 3 ⁇ 4 driven into its corresponding x-trace 32 - i.e. the magnetic field strength increases with the amplitude A kx .
- the amplitude A kx increases with the amplitude A kx .
- a stronger magnetic field creates a corresponding steeper potential energy well having a more pronounced local minimum, which in turn more strongly traps/locks moveable stage 10 and permits improved motion tracking error of moveable stage 10, but at the expense of greater energy consumption
- motion tracking error in Y means the difference between the actual stator-y direction location of stage 10 in and its desired stator-y direction location y r
- motion tracking error in X means the difference between the actual stator-x direction location of stage 10 and its desired stator-x location x r
- the actual stator-x direction location of stage 10 can be the actual stator-x direction location of the geometric center of the stator 10 magnetic assembly 16.
- the actual stator-y direction location of stage 10 can be the actual stator-y direction location of the geometric center of the stator 10 magnetic assembly 16.
- the amplitude A x may be varied based on reference trajectory acceleration (i.e. the 2 nd time derivative (acceleration) of y r ).
- the amplitude A x may be positively correlated with the acceleration of y r - e.g. A x may be increased when the acceleration of y r is relatively high (i.e. there is a desire to change the velocity of moveable stage 10 relatively quickly in the stator-y direction) and decreased when the acceleration of y r is relatively low (i.e.
- a 0 represents a minimum current amplitude
- a is a positive design parameter
- y r (t) is the desired acceleration of moveable stage 10.
- Other relationships between amplitude A x and y r (t) may provide suitable results, as long as A x increases with
- the system can move moveable stage 10 with a low tracking error in the stator-y direction and high acceleration rates during acceleration, and minimize power consumption during relatively stationary states and relatively low acceleration (constant speed) states (i.e. zero acceleration states).
- the amplitudes A jy (or A y with the above-discussed assumption) of the y-current phases i jy can be varied with the desired acceleration of moveable stage 10 in the stage-x direction (i.e. ⁇ x r (t)
- acceleration compensation techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
- control system 54 ( Figure 13 A) operates without using real-time position based feedback. Consequently, to minimize tracking errors arising from friction, some embodiments make use of a dynamic lubrication method.
- dynamic lubrication involves modulating current phase amplitudes Ax and/or modulating current phase phase angles ⁇ ⁇ at temporal frequencies - e.g. at temporal frequencies in a range of 50Hz to 40kHz in some embodiments.
- the amplitude A x and phase ⁇ ⁇ can be generated in the following way:
- a d is dynamic lubrication modulation amplitude for the current phase amplitude A x
- ⁇ ⁇ is the temporal modulation frequency for the current phase amplitude A x
- ⁇ ⁇ is the above discussed phase parameter
- ⁇ 0 is an constant phase angle
- ⁇ p d is modulation amplitude for the current phase phase ⁇ ⁇
- ⁇ ⁇ is modulation frequency for the current phase phase ⁇ ⁇
- ⁇ ⁇ and ⁇ ⁇ are arbitrary constant modulation phase angles for amplitude modulation and phase modulation, respectively.
- High frequency amplitude and/or phase modulation of x-current phases 3 ⁇ 4 can generate high frequency vibration in the stator-z and stator-y directions and such vibration can help attenuate normal direction (stator-z direction) contact force between bearing surfaces 124, 126 of moveable stage 10 and stator 30 and thus attenuate friction force which tends to inhibit motion in in the stator-y direction. Consequently, this effect can help reduce moveable stage tracking errors.
- this dynamic lubrication modulation is used only in particular circumstances. For example, in some embodiments, dynamic lubrication modulation may be used when moveable stage 10 is in a relatively stationary state or when moveable stage 10 is moving at a relatively constant speed (i.e. when the desired acceleration parameter
- the modulation frequencies ⁇ ⁇ and ⁇ ⁇ can be identical or can be set at different values.
- one or both of modulation frequencies ⁇ ⁇ and ⁇ ⁇ are set at or near one resonant frequency of moveable stage 10 in the stator-z direction dynamics.
- the phrase at or near a resonant frequency should be understood to mean at the resonant frequency +/-10%. Due to resonance, the modulation-induced vibration can achieve maximum vibration amplitude.
- Q and R may be any positive or negative integer numbers.
- the amplitudes A jy (or A y with the above-discussed assumption) and/or phases ⁇ p y of the y-current phases i jy , can be similarly modulated at temporal frequencies - e.g. at temporal frequencies in a range of 50Hz to 40kHz in some embodiments.
- the amplitude A y and phase ⁇ p y can be generated in the following way:
- ⁇ P ⁇ Po + ⁇ ⁇ $ ⁇ ( ⁇ ⁇ ⁇ + ⁇ ⁇ )
- a d is dynamic lubrication modulation amplitude for the current phase amplitude A y
- ⁇ ⁇ is the temporal modulation frequency for the current phase amplitude A y
- ⁇ p y is the above discussed phase parameter
- ⁇ 0 is an constant phase angle
- ⁇ ⁇ is modulation amplitude for the current phase phase
- p y is modulation frequency for the current phase phase
- p y , ⁇ ⁇ and ⁇ ⁇ are arbitrary constant modulation phase angles for amplitude modulation and phase modulation, respectively.
- the dynamic lubrication parameters A 0 , ⁇ 0 , A d , ⁇ , ⁇ ⁇ , ⁇ ⁇ , ⁇ ⁇ and ⁇ ⁇ are the same for x-current phases and y-current phases i jy , but this is not necessary and these parameters may be different for x-current phases 3 ⁇ 4 and y- current phases i jy .
- fine position control of moveable stage 10 may involve application of impulse signals to an initial amplitude and/or initial phase.
- Impulses may be used to finely adjust the moveable stage when the desired position (x r , y r ) remains static.
- Increasing the amplitudes of current phases i jy can minimize tracking error caused by friction forces - i.e. moveable stage 10 may be brought closer to the minimum magnetic potential energy location (x r ,y r ) at higher amplitudes of current phases i jy .
- moveable stage 10 Once a moveable stage 10 moves close to its minimum energy location (x r ,y r ), moveable stage 10 will be latched there by friction force and the amplitudes of current phases 3 ⁇ 4, can be decreased to reduce power consumption.
- the fine position of moveable stage 10 can be controlled using impulse control as described in more detail below.
- Figure 15 A shows amplitude A x and phase ⁇ ⁇ impulses for an x-current phase h x according to a particular embodiment. Similar impulses can be provided to the amplitudes A x and phases ⁇ ⁇ for other x-current phases h x .
- the amplitude A x which is at an initial level of A 0 prior to i;, suddenly increases to a first impulse amplitude Ao+Aj at time i; for a first temporal period At and then, at time t 2 , decreases to a lower level.
- the lower level (after ti) is Ao, while in other embodiments it may be a different amplitude.
- the phase ⁇ ⁇ which is at an initial level of ⁇ 0 prior to i;, suddenly increases to a first impulse amplitude ⁇ 0 + ⁇ at time i; for a first temporal period At and then, at time t 2 , decreases to a lower level.
- the lower level (after ti) is ⁇ 0 , while in other embodiments it may be a different from ⁇ 0 .
- the phase impulse strength ⁇ may be positive or negative.
- ⁇ can be + ⁇ /2 or — ⁇ /2 or other values.
- phase impulses having similar characteristics may be applied to the amplitude A y and phase ⁇ p y of y-current phases i jy .
- phase impulses in x-traces can also help achieve stator-y acceleration of moveable stage 10.
- the impulse duration is in a range of 0 ⁇ At ⁇ 10 minutes. In some embodiments, the impulse duration is in a range of 0 ⁇ At ⁇ l minute. In some embodiments, the impulse duration is in a range of 0 ⁇ At ⁇ l second. In some embodiments, the impulse duration is in a range of 0 ⁇ At ⁇ 0.1 second.
- the impulses in the amplitudes and phases of x-current phases 4 * will create impact forces on moveable stage 10 in the stator-y direction and stator-z direction; and impulses in the amplitudes and phases of y-current phases i jy will create impact forces on moveable stage 10 in the stator-x direction and stator-z direction. The resulting impact forces may create small amounts of motion which can help with the fine position of moveable stage 10.
- FIG. 15 A shows a rectangular impulse waveform, this is not necessary.
- impulses of any arbitrary waveform shapes can additionally or alternatively be used.
- impulses having triangular, rounded or other waveform shapes may be used.
- FIG. 15B shows a series of amplitude A x and phase ⁇ ⁇ impulses for an x-current phase * according to a particular embodiment.
- Each impulse in the Figure 15B series may have parameters similar to the impulses described above in connection with Figure 15 A.
- moveable stage 10 can experience a series of impact forces.
- the impact strength of the series of impulses (e.g. the parameter Aj) can vary from one impulse to another (e.g.
- Figure 15C shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse 61 A is applied to the x-current phases 4 * at a time and lasts for a period of time At before a second amplitude impulse 61B is applied to the y-current phases i jy at a time t 2 .
- Each impulse 61 A, 61B may have features similar to the amplitude impulse described above in Figure 15A.
- First impulse 61 A may be applied to all of the x-current phases h x and second impulse 6 IB may be applied to all of the y-current phases i jy .
- impulses 61A, 61B may overlap temporally. That is, the start time t 2 of impulse 61B may occur at a time less than ti+At and the finish time t 2 +At may occur at a time after tj+At.
- the start time of impulse 61B may be one of before and after the start time of impulse 61 A and the finish time of impulse 6 IB may be the one of before and after the finish time of impulse 61 A.
- the duration Atj of impulse 61 A may be different that the duration At 2 of impulse 61B.
- Figure 15C shows only amplitude impulses 61A, 61B.
- one or both of amplitude impulses 61 A, 6 IB could be accompanied by phase impulses having
- Figure 15D shows an exemplary moveable stage fine positioning process in which a first amplitude impulse 61 A is applied to the x-current phases 3 ⁇ 4 at a time i; and lasts for a period of time At before a second amplitude impulse 61B is applied to the y-current phases i jy at a time t 2 .
- the fine positioning process of the Figure 15D embodiment differs from the fine positioning process of the Figure 15C embodiment in that during first impulse 61A applied to the x-current phases h x (i.e. from the time i; to tj+At in the illustrated embodiment), the amplitudes A y of the y-current phases i jy are reduced to a low level (e.g.
- phase impulse excitation may have properties similar to that of amplitude impulse excitation described herein.
- impulse excitation fine positioning techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
- displacement device 50 and its control system 58 operate without real-time position feedback (i.e. control system 58 does not require real-time positions of moveable stage(s) 10).
- control system 58 it may be beneficial for control system 58 to know initial location(s) of moveable stage(s) 10 (e.g. on startup). The initial location of a moveable stage 10 is useful for determining the coil traces 32, 34 into which current phases i jy should be driven to control the position of the moveable stage 10.
- initial position(s) of moveable stage(s) 10 are described herein.
- One example way to determine initial position of moveable stage(s) 10 involves using one-by-one initialization.
- One-by-one initialization comprises positioning a moveable stage 10 at a specific well-defined start location by other means, such as manually or by a robotic arm/hand.
- Figure 16A is a schematic depiction of how a one-by-one initialization process may be used to determine an initial location of a moveable stage in a displacement device 550 according to a particular embodiment.
- displacement device 550 a predefined region 563 is defined for placing a moveable stage 510 upon startup.
- placing moveable stage 510 in start region 563 may comprise abutting moveable stage 510 against alignment device 565.
- coil traces 32, 34 overlapping start region 563 in the stator-z direction may be switched off (i.e. may not be driven with current phases i ⁇ , i jy ) during the process of locating moveable stage 510 in start region 563 - i.e. to minimize interacting forces between moveable stage 510 and stator 530.
- moveable stage 510 By placing moveable stage 510 in region 563 and, optionally, pushing or otherwise abutting moveable stage 510 against alignment device 565, moveable stage 510 will be positioned at start region 563.
- control system 58 may drive current phases ij y into coil traces 32, 34 in region 563 and may move moveable stage 510 away to other locations in working region 536, whereupon moveable stage 510 is fully controlled by control system 58 and its corresponding current phases ij y .
- the initialization procedure can be repeated for a next moveable stage 10.
- FIG. 16B depicts an alignment device 565' according to another embodiment which may be used with displacement device 550 and the one-by-one initialization technique of Figure 16A.
- Alignment device 565' comprises one or more alignment features 566, which may interact physically with complementary alignment features (not shown) in moveable stages 510 to assign with one-by-one initialization as described above.
- alignment features 566 each comprise a corresponding protrusion that may be received in a complementary recess in moveable stage 510.
- complementary pairs of alignment features 566 in alignment device 565' and moveable stage 510 could have a variety of other shapes.
- moveable stage 510 may additionally or alternatively comprise one or more beveled surfaces and/or protrusions and alignment features 566 may additionally or alternatively comprise one or more complementary shaped beveled surfaces and/or recesses.
- Figure 16C schematically depicts a displacement device 550" comprising a stator 530" and a plurality of moveable stages 510" according to another embodiment.
- Figure 16C illustrates a group initialization technique for determining the initial positions of moveable stages 510".
- Moveable stages 510" are organized side by side to form a pattern either manually or with the aid of a robot device.
- An optional alignment device 565" (having features similar to alignment devices 565, 656') may be provided and used to facilitate organizing these moveable stages 510".
- Moveable stages 510" can be organized into a rectangular matrix pattern, for example. In the exemplary embodiment of Figure 16C, eleven moveable stages 510 are organized into three rows, with the third row not completely filled.
- control system 58 e.g. controller 60
- a graphical user interface 567 or by any other suitable input interface.
- control system 58 will roughly know the positions of each moveable stage 510" with an accuracy to within a small fraction of spatial periods ( ⁇ ⁇ , ⁇ ).
- control system 58 can drive moveable stages 510" and separate moveable stages 510" from each other with an appropriate algorithm.
- Alignment devices 565, 565', 565" are optional. For example, when a robot device is used to initialize the positions of moveable stages, alignment devices 565, 565', 565" may not be needed as positional feedback from the robot device (such as positional feedback related to the position of a robot arm/hand) may be sufficient to position each moveable stage accurately. Initialization may occur only once (e.g. when a displacement device is first powered on). In some embodiments, before powering off the displacement device, control system 58 can drive the moveable stages back to their initialization locations. As a result, when the displacement device is powered on again, the moveable stages should be very close to the desired pattern with minimum requirement from an operator. In this sense, only the very first initialization needs some effort to organize the moveable stages to form a matrix pattern, although these methods can be used for adding additional moveable stages or in other situations.
- Displacement devices provide flexibility with respect to the motion paths over which moveable stages can be controllably moved, especially when compared to conventional belt-based conveyor or track systems, where the one-dimensional track location and sizes are fixed after manufacturing.
- Figure 17A For the purpose of illustrating a number of exemplary motion paths of moveable stages, Figure 17A
- FIG. 17B shows one exemplary moveable stage 10, which may be used with the Figure 17A stator 30.
- Moveable stage 10 of the Figure 17B embodiment comprises a magnet array assembly 16 and bumper 17, which surrounds magnet array assembly 16. It will be understood that although moveable stage 10 of the Figure 17B embodiment is depicted as being square with a bumper surrounding the perimeter, it may be of any suitable shape or form, such as any of at least the moveable stages described herein.
- Figure 17C shows one motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30.
- the Figure 17C embodiment provides a path 69A (e.g. an oval shaped path 69A), along which a plurality (e.g. nine) moveable stages 10 can move bi-directionally.
- the Figure 17C embodiment also provides two entry/exit paths 69B (shown in dashed lines). Moveable stages 10 moving along path 69 A can exit via either one of entry/exit paths 69B. Similarly, moveable stages 10 outside path 69 A can enter path 69 A via one of entry/exit paths 69B.
- the exact size of the oval shaped path 90 can be dynamically changed by control software to meet certain application needs.
- the numbers, sizes and/or locations of exit/entry paths 69B can also be dynamically changed by control software as desired.
- Figure 17D shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30.
- Moveable stages 10 move along two paths 69A' and 69 A" (e.g. circular paths 69A', 69A").
- One moveable stage 10 can transition from one path 69 A' to another path 69A", or vice versa.
- a moveable stage 10 can move out of both circular paths 69A', 69A”.
- Figure 17E shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30 which mimics a conventional oval shaped conveyer system by moving moveable stages 10 along a path 69 A.
- Figure 17F shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17 A stator 30.
- Figure 17F is similar to Figure 17D in that moveable stages 10 move along two paths 69A' and 69 A", except that the Figure 17F paths 69A', 69A" have different shapes than the Figure 17D paths.
- Figure 17G shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30.
- Figure 17G shows that groups of moveable stages 10 can move together very closely. Different groups of moveable stages 10 can pass each other in opposite directions. Different groups of moveable stages 10 can have individual moveable stages 10 spaced apart by varying distances. Groups of moveable stages 10 can comprise any suitable number of available moveable stages 10. Individual moveable stages 10 can switch between groups or form new groups.
- Figure 17H shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30.
- Figure 17H shows that a matrix group of moveable stages 10 (e.g.
- moveable stages 10 in a 3 by 3 matrix group can also move together and have independent motion from another linear group of moveable stages 10, and two groups can pass each other.
- Moveable stages 10 can form into linear (ID) groups, or matrix (2D) groups as shown in Figure 17H. Each moveable stage 10 may have completely independent motion from all other moveable stages 10.
- a plurality of moveable stages 10 can form into groups and a group of moveable stages 10 can also ungroup themselves to allow independent motion for each moveable stage 10.
- each moveable stage 10 can achieve independent motion control, can flexibly move out of the moving queue
- FIGs 18A-18F schematically illustrate one exemplary embodiment of a process of a number of the Figure 17B moveable stages 10 ungrouping from one another.
- nine moveable stages 1 OA- 101 form a group to move together relative to a stator 30 (e.g. the Figure 17A stator 30, in the illustrated embodiment).
- Stator 30 includes a plurality of independently driven current excitation regions 43 shown in dashed outline, each pair of excitation regions separated by a corresponding boundary plane. These boundary planes may be oriented in stator- x-stator-z planes or stator-y-stator-z planes.
- One technique for ungrouping the Figure 18A moveable stages 10 comprises: (a) the group moves in a first stator-x direction as shown in Figure 18A until the group reaches the location shown in Figure 18B, where moveable stages 10A, 10D and 10G are located in excitation regions 43 decoupled from the rest of the group; (b) moveable stages 10A, 10D, 10G may then be driven in the first stator-x direction away from the other moveable stages 10 using suitable y-current phases ij y (which may be the same for each of moveable stages 10A, 10D, 10G).
- the rest of the moveable stages (10B, IOC, 10E, 10F, 10H, 101) in the group may be held stationary or may be driven in the second (i.e. opposite to the first) stator-x direction by suitable y-current phases i jy .
- stages 10A, 10D, 10G are independently driven from the rest of the group; (c) moveable stages 10A, 10D, 10G are then driven in a first stator-y direction (as shown in Figure 18D) using suitable x-current phases 3 ⁇ 4 until stage 10G is located in an excitation region 43 that is decoupled from stages 10A and 10D; (d) As shown in Figure 18E, during this time, stage 10G is further driven in the first stator-y direction using suitable x-current phases while the rest of moveable stages 10A, 10B, IOC, 10D, 10E, 10F, 10H and 101 may be held stationary or may be driven in the second (i.e.
- moveable stage 10G separates from moveable stages 1 OA, 10D (as shown in Figure 18E); and (e) as shown in Figure 18F, moveable stage 10G can now achieve independent motion in stator-x and stator-y directions.
- the other moveable stages 10 can be ungrouped to achieve independent motion in the stator-x and stator-y directions.
- a plurality of moveable stages 10 can form into linear (1 -dimensional) group(s) or a matrix (2-dimensional) group(s). This is useful in queuing for saving space or in high speed movement of a relatively large number of moveable stages 10.
- the currents in different excitation regions may be controllably driven to cause a first group of one or more moveable stages to separate from a second group of one or more moveable stages by: driving the currents to position the plurality of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages (e.g.
- the first boundary plane between the first and second excitation regions may be in either a stator-x-stator-z plane or a stator-y-stator-
- a second plurality of currents in different excitation regions may be controllably driven to cause a first sub-group of the first group of moveable stages to separate from a second sub-group of the first plurality of moveable stages by: driving the second plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a second boundary plane extending in a stator-z direction between a third excitation region of the plurality of excitation regions and a fourth excitation region of the plurality of excitation regions divides the first sub-group and the second sub-group of the first group of moveable stages (e.g.
- magnet assemblies of the first and second sub-groups are on opposite sides of the second boundary plane); and driving the second plurality of currents in at least some of the coil traces of the third excitation region to at least one of: move the first sub-group of moveable stages in a third direction away from the second boundary plane; and move the first sub-group of moveable stages in a third direction away from the second sub-group of moveable stages, the third direction parallel with the surface of the second boundary plane; while driving the second plurality of currents in at least some of the coil traces of the fourth excitation region to at least one of: maintain the location of the second sub-group of moveable stages within the working region; and move the second sub-group of moveable stages in a fourth direction away from the second boundary plane; move the second sub-group of the moveable stages in a fourth direction away from the first sub-group of moveable stages, the fourth direction paralle with the surface of the second boundary plane.
- the second boundary plane may be in one of a stator- x-stator-z plane and a stator-y-stator-z plane and may be orthogonal to the first boundary plane.
- the third excitation region may be one of the first excitation region and the second excitation region.
- the fourth excitation region may be one of the first excitation region and the second excitation region, but is different than the third excitation region.
- Some aspects of the invention provide methods for controlling the movement of a plurality of moveable stages relative to a stator to separate a first group of one or more moveable stages from a second group of one or more moveable stages.
- Each moveable stage among the first and second groups of moveable stages may be similarly constructed with one or more magnet arrays, the one or more magnet arrays comprising at least one magnet array comprising a plurality of magnetization segments, each magnetization segment having a corresponding magnetization direction.
- the methods comprise: providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide a plurality of stator-z-direction-non-overlapping excitation regions, each excitation region comprising: a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer; and a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction.
- the first and second portions of the first and second layers may overlap one another in a stator-z direction throughout the excitation region.
- the stator-z direction may be generally orthogonal to both the stator-x direction and the stator-y direction.
- the method may also comprise controllably driving a plurality of currents into the plurality of electrical coils to thereby cause a first group of one or more of the plurality of moveable stages to separate from a second group of one or more of the plurality of moveable stages.
- Controllable driving the plurality of currents into the plurality of electrical coils may comprise: driving the plurality of currents into the plurality of electrical coils to position the plurality of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages; driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: move the first group of moveable stages in a first direction away from the first boundary plane; and move the first group of moveable stages in a first direction away from the second group of moveable stages, the first direction parallel with the first boundary plane surface; while driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region, driving at least some of the plurality of currents in at least some of the coil traces of the second excitation region to at least one of: maintain
- the method may comprise controllably driving a second plurality of currents into the plurality of electrical coils to thereby cause a first sub-group of the first group of moveable stages to separate from a second sub-group of the first group of moveable stages.
- Controllably driving the second plurality of currents into the plurality of electrical coils may comprise: driving the second plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a second boundary plane extending in the stator-z direction between a third excitation region of the plurality of excitation regions and a fourth excitation region of the plurality of excitation regions divides the first sub-group and the second sub-group of the first group of moveable stages; and driving at least some of the second plurality of currents in at least some of the coil traces of the third excitation region to at least one of: move the first sub-group of the first group of moveable stages in a third direction away from the second boundary plane; and move the first sub-group of the first group moveable stages in a direction away from the second sub-group of the first group of moveable stages, the third direction parallel with the second boundary plane surface; while driving at least some of the second plurality of currents in at least some of the coil traces of the third ex
- the second boundary plane may be in one of a stator-x-stator-z plane and a stator-y-stator-z plane and may be orthogonal to the first boundary plane.
- the third direction may be orthogonal to the first direction.
- the third excitation region may be one of the first excitation region and the second excitation region.
- the fourth excitation region may be one of the first excitation region and the second excitation region, but may be different than the third excitation region.
- a stator-z location of the third layer may be the same as one of: a stator-z location of the first layer; and a stator-z location of the second layer.
- a stator-x dimension of the first excitation region is greater than a stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage; a stator-y dimension of the first excitation region is greater than a stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage; a stator- x dimension of the second excitation region is greater than the stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage; a stator-y dimension of the second excitation region is greater than the stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage.
- Driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region may comprise driving currents with similar periodicity but with different phases into the first plurality of coil traces. In some embodiments, driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region may comprise driving currents with similar periodicity but with different phases into the second plurality of coil traces.
- the process may be reversed and the currents in different excitation regions may be controllably driven to cause a first group of one or more moveable stages to abut against, or be close (e.g. within a distancel.5 i or 1.5 ⁇ 2 ) to, a second group of one or more moveable stages by: driving the plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions, divides the first and second groups of moveable stages (e.g.
- magnet assemblies of the first group of moveable stages and magnet assemblies of the second group of moveable stages are on opposite sides of the first boundary plane); and driving the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: maintain the location of the first group of moveable stages within the working region; and move the first group of moveable stages in a first direction toward the first boundary plane; move the first group of moveable stages in a first direction toward the second group of moveable stages, the first direction parallel to the surface of the first boundary plane; while driving the plurality of currents in at least some of the coil traces in the second excitation region to at least one of: move the second group of moveable stages in a second direction toward the first boundary plane; and move the second group of moveable stages in a second direction toward the first group of moveable stages, the second direction parallel with the surface of the first boundary plane.
- Some aspects of the invention provide methods for controlling the movement of a plurality of moveable stages relative to a stator to bring the moveable stages into close proximity to one another.
- the method comprises: providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide a plurality of excitation regions, each excitation region comprising: a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer; a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction.
- the first and second portions of the first and second layers may overlap one another in a stator-z direction throughout the excitation region, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction.
- the method may comprise: providing a plurality of moveable stages moveable relative to the stator within a two-dimensional working region, each moveable stage comprising one or more magnet arrays, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction; and controllably driving a plurality of currents into the plurality of electrical coils to thereby cause a first group of one or more of the plurality of moveable stages within one magnet array dimension to a second group of one or more of the plurality of moveable stages.
- Controllably driving the plurality of currents into the plurality of electrical coils may comprise: driving the plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages; and driving the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: maintain the location of the first group of moveable stages within the working region; move the first group of moveable stages in a first direction toward the first boundary plane; move the first group of moveable stages in a first direction towards the second group of moveable stages, the first direction parallel to the surface of the first boundary plane; while driving the plurality of currents in at least some of the coil traces in the second excitation region to at least one of: move the second group of moveable stages toward the first boundary plane; move the second group of moveable
- Figures 19A-19G schematically depict a technique for implementing rotational motion of a moveable stage 610 about a stator-z oriented axis according to a particular embodiment.
- the technique of Figures 19A-19G is shown for a displacement device incorporating a magnet array assembly 616 and a coil trace assembly 635 according to specific embodiments, but by suitable modification which will be understood to those skilled in the art after the following explanation, the technique of Figures 19A-19G can be applied to other displacement devices described herein.
- Figure 19A shows a magnet array assembly 616 of a moveable stage 610 according to a particular embodiment which is used to facilitate the illustration of Figures 19A-19G.
- stator 630 comprises a-coil traces 633 distributed over at least a portion of a a-trace layer 649 which are oriented at an angle a° relative to the positive stator-x axis.
- a may be any angle between 0°-90°.
- Current phases k a may be driven into a-coil traces 633.
- Such current phases k a may have properties similar to the x-current phases 3 ⁇ 4 and/or the y-current phases i jy , except that there may be a different (or the same) spatial period ⁇ ⁇ .
- the traveling magnetic field wave generated by the current phases driven into coil traces 633 is generated such that moveable stage 610 will have a local minimum potential energy when magnet array assembly 616 is in the 45°-orientation shown in Figure 19D.
- moveable stage 10 will tend to rotate around a stator-z oriented axis 671 from the 0° orientation shown in Figure 19B, through the orientation in Figure 19C to reach the 45°- orientation illustrated in Figure 19D.
- the position of the center of moveable stage 610 (through which stator-z oriented axis 671 extends) may remain nearly unchanged in the stator-x, stator-y coordinate system.
- 135°-current phases could be driven into 135°-traces 633' in 135°-trace layer 649' to effect the rotation of moveable stage 610 between the 0° ( Figure 19B) orientation and the 45° ( Figure 19D) orientation.
- y-current phases ij y may be driven into y-traces 634 in y-trace layer 642 ( Figure 19E) to achieve further rotation about stator-z oriented axis 671.
- y-current phases ij y are driven into y-traces 634, the traveling magnetic field wave generated by y-current phases ij y is generated such that moveable stage 610 will have a local minimum potential energy when magnet array assembly 616 is in the 90°-orientation shown in Figure 19G.
- moveable stage 10 will tend to rotate around stator-z oriented axis 671 from the 45° orientation shown in Figure 19E, through the orientation in Figure 19F to reach the 90°- orientation illustrated in Figure 19G.
- the position of the center of moveable stage 610 (through which stator-z oriented axis 671 extends) may remain nearly unchanged in the stator-x, stator-y coordinate system.
- x-current phases 3 ⁇ 4 could be driven into x- traces 632 in x- trace layer 640 to effect the rotation of moveable stage 610 between the 45° ( Figure 19E) orientation and the 90° ( Figure 19G) orientation.
- magnet array assembly 616 is 90° rotationally symmetric about stator-z oriented axis 671
- the Figure 19G orientation is magnetically equivalent to the Figure 19B orientation. Consequently, further rotation about axis 671 can be achieved by suitable repetition of the above-described procedures using 45°-current phases and/or 135°-current phases and x- current phases and/or y-current phases ij y .
- FIG. 19A-19G The rotation techniques and coil trace assemblies described in Figures 19A-19G are described with application to magnet array assembly 616. It will be appreciated that magnet array assembly 616 has a layout similar to magnet array assembly 416A ( Figure 5A). Any of the rotation techniques and coil trace assemblies described in Figures 19A-19G may be used with magnet array assembly 416A (or a left-handed version thereof - see description of left- handed versus right-handed magnet arrays above) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE.
- Figure 5B shows a left-handed magnet array assembly 416B that is different than magnet array assembly 416 A ( Figure 5 A) in that the individual magnet arrays of magnet array assembly 416B are offset and spaced apart from one another as described above.
- any of the rotation techniques and coil trace assemblies described in Figures 19A-19G may be used with magnet array assembly 416B (or a right-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A
- moveable stages 10 comprising ID magnet array assemblies 16 may be capable of fully controllable 360° rotation about a stator-z oriented axis using current phases driven into coil traces having any two or more directions (e.g. x-current phases 3 ⁇ 4 driven into x-traces 32 and y-current phases i jy driven into y-traces 34).
- Figures 20A and 20B
- the top portion of Figure 20 A shows the generation of three y-current phases y , ij y , according to:
- a current, a current trace and/or its associated magnetic field is described as traveling with a reference variable (e.g. with a reference trajectory variable x r , y r , d r ), it should be understood to mean that such current, current trace and/or magnetic field varies spatially as the reference variables vary over time (e.g. the magnetic field generated by the y-current phases travel in the stator-x direction with x r — d r as reference trajectory variables x r , d r vary over time).
- phase shift between adjacent y-current phases i 0y , i ly , i 2y is (in electrical angle radians) or 1 ⁇ 2 (in spatial phase).
- Phase-adjacent ones of y-current phases i 0y , ii y , 3 ⁇ 4 can be driven into spatially adjacent y-traces 34, such the phase difference between the y-current phases y , ij y , i2 y driven into spatially adjacent y-traces 34 is
- This technique for generating y-current phases i jy can be generalized for a different number m p of effective y-current phases, where m p is an integer greater than 1.
- FIG. 20A The bottom portion of Figure 20A shows the generation of three y-current phases io y , ii y , h y which vary with x r + d r in the stator-x direction according to:
- equation (9) may be generalized to:
- equation (10) have the same meanings as those of equation (8a).
- equations (10) that the currents generated by the bottom portion of Figure 20A generate magnetic fields which travel with x r + d r in the stator-x direction.
- y-traces 34 in stator 30 can be designed to have a stator-y coil trace pitch
- current phases i jy may generally have any waveform that is a spatially periodic function of x r -d r (in the top portion of Figure 20A) or x r +d r (in the bottom portion of Figure 20 A), sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution.
- Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like.
- Y-current phases i jy that generate magnetic fields that travel with x r +d r may be referred to herein collectively as second positive rotational currents and individually as second positive rotational current phases.
- y-current phases i jy that generate magnetic fields that travel with x r -d r may be referred to herein collectively as second negative rotational currents and individually as second negative rotational current phases.
- FIG. 20B shows the generation of three x-current phases x , ij x , i2 % which vary with y r — d r in the stator-y direction which, for the general case with n p effective x-current phases, may be generalized to:
- FIG. 20B shows the generation of three x-current phases x , ii x , i2x which vary with y r + d r in the stator-y direction which, for the general case with n p effective x-current phases,
- the phase shift between adjacent x-current phases ikx takes the general form
- x-traces 32 in stator 30 can be designed to
- While current phases ikx may generally have any waveform that is a spatially periodic function of y r -d r (in the top portion of Figure 20B) or y r +d r (in the bottom portion of Figure
- sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution.
- Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like.
- X-current phases ikx that generate magnetic fields that travel with y r +d r may be referred to herein collectively as first positive rotational currents and individually as first positive rotational current phases.
- x-current phases 3 ⁇ 4 that generate magnetic fields that travel with y r -d r may be referred to herein collectively as first negative rotational currents and individually as first negative rotational current phases.
- differential variable d r described above in connection with equation (7)-(12) and in the description of the embodiments in Figures 20A and 20B may be the same variable; in general, however, the differential variable d r used in the embodiment of Figure 20A (equations (7)-(10)) may be different than, and independent from, the differential variable d r used in the embodiment of Figure 20B (equations (11)-(12)).
- FIG. 21 A shows one non-limiting example of magnet array assembly 716 which may be used for controllable 360° rotation according to a particular embodiment.
- Magnet array assembly 716 comprises four ID magnet arrays 712A-712D.
- Magnet arrays 712B, 712D are linearly elongated in stage-y direction
- magnet array 712A, 712C are linearly elongated in stage-x direction.
- Each magnet array 712 comprises a plurality of linearly elongated magnetization segments 714 with corresponding magnetization directions generally orthogonal to its elongation direction.
- any ID magnet array assembly 16 described herein can be used for the controllable 360° rotation operation, by applying the operational methods and control algorithms described herein with appropriate modification where desired.
- Magnet array assemblies having the 90° rotational symmetric property (about a z- oriented axis (e.g. axis 771 at the center stage-x-stage-y center of magnet array assembly 16 and/or moveable stage 10)) are currently preferred.
- Figures 21B-2 IK illustrate possible coil traces 732, 734 and corresponding current phases driven therein to operate the Figure 21A magnet array assembly 716 to achieve controllable rotation.
- Figure 21B shows a top view of a displacement device 750 including a moveable stage 710 comprising the Figure 21A magnet array assembly 716 which is moveable relative to a stator 730 comprising coil assembly 735.
- a stator-z oriented axis 771 extends through the stage-x-stage-y center 771A of moveable stage 710 and/or magnet array assembly 716 and coincides with a notional dividing plane CC, which extends in the stator-y and stator-z directions.
- first and second pluralities i.e.
- first and second groups) of y-traces 734 that are elongated in the stator-y direction traces 734- (shown in solid lines) and traces 734+ (shown in broken lines), where traces 734- represent the y-traces located on the negative stator-x side of a boundary that coincides with dividing plane CC and traces 734+ represent the y-traces located on the positive stator-x side of the boundary that coincides with dividing plane CC.
- First and second pluralities of coil traces 734+, 734- may be located on the same or different layers (e.g. at the same or different stator-z locations).
- Coil traces 734+ are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r (i.e. coil traces 734+ are driven with second positive rotational current phases) and coil traces 734- are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r (i.e. coil traces 734- are driven with second negative rotational current phases).
- the first and second pluralities of y-current phases i jy can be driven into y-traces 734 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43.
- first and second pluralities of y-current phases i jy can be independently driven into two pluralities of y-traces 734 inside one excitation region 43.
- x r may be fixed or there may be no commanded translation motion along the stator-x axis.
- the two types of traveling magnetic field waves i.e. those generated by the current phases driven in traces 734- and those generated by the current phases driven in traces 734+) will move in opposite directions.
- d r is positively ramping up (i.e.
- magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction as shown in Figure 21C. For example, when d r increases by ⁇ , magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°.
- magnet array assembly 716 Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 816 will rotate around central stator-z oriented axis 771 in a clockwise direction.
- Figure 21D illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using x-current phases ikx driven into first and second pluralities (i.e. first and second groups) of x-traces 732+, 732-.
- First and second pluralities of x-traces 732+, 732- may be located on the same or different layers (e.g. at the same or different stator-z locations).
- the Figure 21D illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 771 at the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710).
- first plurality 732- and second plurality 732+ of x-traces 732 that are elongated in the stator-x direction, where traces 732- represent the x-traces located on the negative stator-y side of a boundary that coincides with dividing plane DD and traces 732+ represent the x-traces located on the positive stator-y side of the boundary that coincides with dividing plane DD.
- Coil traces 732+ are driven with x- current phases (and generate corresponding magnetic fields) which travel with y r +d r (i.e.
- first and second pluralities of x-current phases ikx can be driven into x-traces 732 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases ikx can be independently driven into two pluralities (i.e. groups) of x-traces 732 inside one excitation region 43.
- y r may be fixed or there may be no commanded translation motion along the stator-y axis.
- the two types of traveling magnetic field waves i.e. those generated by the current phases driven in traces 732- and those generated by the current phases driven in traces 732+) will move in opposite directions.
- d r is positively ramping up (i.e.
- magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when d r increases by ⁇ , magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°.
- magnet array assembly 716 Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
- Figure 21 E illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using x-current phases * driven into first and second pluralities of x-traces 732+', 732-'.
- First and second pluralities of x-traces 732+', 732-' may be located on the same or different layers (e.g. at the same or different stator-z locations).
- the Figure 21E illustration shows a notional dividing plane CC which extends in the stator-y and stator-z directions and coincides with stator-z oriented axis 771 in the stage- x-stage-y center 771A of magnet array 716 and/or moveable stage 710.
- first plurality 732-' and second plurality 732+' of x-traces 732 that are elongated in the stator-x direction, where traces 732-' represent x-traces located on the negative stator-x side of a boundary that coincides with dividing plane CC and traces 732+' represent x-traces located on the positive stator-x side of the boundary that coincides with dividing plane CC.
- Coil traces 732+' are driven with x- current phases 4 * (and generate corresponding magnetic fields) which travel with y r +d r (i.e.
- first and second pluralities of x-current phases ikx can be independently driven into x- traces 732 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases i kX can be independently driven into two pluralities (i.e. groups) of x-traces 732 inside one excitation region 43.
- y r is not necessarily fixed in which case the techniques illustrated in Figure 2 IE permit moveable stage 710 to achieve simultaneous stator-y oriented translation and rotation about central stator-z oriented axis 771.
- the two types of traveling magnetic field waves i.e. those generated by the current phases driven in traces 732-' and those generated by the current phases driven in traces 732+'
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in coil traces 732+' will pull ID magnet array 712A in the positive stator-y direction relative to stage-x-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 732-' will pull ID magnet array 712C in the negative stator-y direction relative to stage-x-stage-y center 771 A of magnet arrays 716 and/or moveable stage 710. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction.
- magnet array assembly 716 when d r increases by ⁇ , magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
- Figure 21F illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using y-current phases ij y driven into first and second pluralities of y-traces 734+', 734-'.
- First and second pluralities of y-traces 734+', 734-' may be located on the same or different layers (e.g. at the same or different stator-z locations).
- the Figure 21F illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771A of magnet array 716 and/or moveable stage 710.
- first plurality 734-' and second plurality 734+' of y-traces 734 that are elongated in the stator-y direction, where traces 734-' represent y-traces located on the positive stator-y side of a boundary which coincides with dividing plane DD and traces 734+' represent y-traces located on the negative stator-y side of the boundary which coincides with dividing plane DD.
- Coil traces 734+' are driven with y- current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r (i.e.
- first and second pluralities of y-current phases 3 ⁇ 4 can be independently driven into y- traces 734 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43.
- first and second pluralities of y-current phases i jy can be independently driven into two pluralities (i.e. groups) of y-traces 734 inside one excitation region 43.
- x r is not necessarily fixed in which case the techniques illustrated in Figure 2 IF permit moveable stage 710 to achieve simultaneous stator-x oriented translation and rotation about stator-z oriented axis 771.
- the two types of traveling magnetic field waves i.e. those generated by the current phases driven in traces 734-' and those generated by the current phases driven in traces 734+'
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in coil traces 734+' will pull ID magnet array 712D in the positive stator-x direction relative to the stage-z-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 734-' will pull ID magnet array 712B in the negative stator-x direction relative to the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction.
- magnet array assembly 716 when d r increases by ⁇ , magnet array assembly 716 will rotate around the stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
- some embodiments comprise combining the techniques shown in Figures 21B and 21E by driving x-current phases 3 ⁇ 4 in traces 732-', 732+' and y- current phases i jy in traces 734-, 734+ to achieve greater torque during rotation.
- the rotation of magnet array assembly 716 is operated along the plane CC that extends in the stator-y direction and stator-z direction.
- Boundary plane CC may be at the boundary between a pair of excitation regions 43A, 43B.
- the Figure 21G technique allows rotation of moveable stage 710 while the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710 translates along CC (i.e. in the stator-y direction).
- some embodiments comprise combining the techniques shown in Figures 21D and 21F by driving y-current phases i jy in traces 734-', 734+' and x- current phases in traces 732-, 732+ to achieve larger torque during rotation.
- the rotation of magnet array assembly 716 is operated along the plane DD that extends in the stator-x direction and stator-z direction.
- Boundary plane DD may be the boundary between a pair of excitation regions 43A, 43B.
- the Figure 21H technique allows rotation of moveable stage 710 while the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710 translates along DD (i.e. in the stator-x direction).
- some embodiments comprise combining the techniques shown in Figures 21C and 21D by driving y-current phases i jy in traces 734-, 734+ and x- current phases in traces 732-, 732+ to achieve larger torque during rotation.
- FIG. 21 J some embodiments comprise rotating magnet array assembly 716 and its corresponding moveable stage 710 at the intersection point of four independently driven current excitation regions 43A-43D.
- the Figure 21 J illustration shows notional dividing boundary planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of boundary planes CC and DD coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710.
- Stator-z oriented axis 771 coincides with the intersection of excitation regions 43A-43D - i.e.
- x-traces 732A in excitation region 43A are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r +d r
- y-traces 734B in excitation region 43B are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 732C in excitation regions 43C are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 734D in excitation region 43D are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r .
- coil traces 732A, 734B, 732C, 734D may be distributed throughout at least a portion of their respective excitation regions 43A-43D.
- the current phases driven into the coil traces in each of excitation regions 43 A- 43D create traveling magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in x-coil traces 732A will pull ID magnet array 712A in the positive stator-y direction
- the magnetic field traveling wave generated by current phases driven in y-coil traces 734B will pull ID magnet array 712B in the negative stator-x direction
- the magnetic field traveling wave generated by current phases drive in x-coil traces 732C region 43C
- the magnetic field traveling wave generated by current phases driven in y-coil traces 734D will pull ID magnet array 712D in the positive stator-x direction.
- magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when d r increases by ⁇ , magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90° counter-clockwise. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e.
- Figure 21 K shows another embodiment which comprises rotating magnet array assembly 716 and its corresponding moveable stage 710 at the intersection point of four independently driven current excitation regions 43A-43D.
- the Figure 21 K embodiment may be considered to be a combination of techniques shown in Figures 21 E and 2 IF.
- FIG. 21 K illustration shows notional boundary dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator-x stator-z directions and the intersection of boundary planes CC, DD coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710.
- Stator-z oriented axis 771 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 771.
- x-traces 732A in excitation region 43 A are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r + d r
- y-traces 734A in excitation region 43A are driven with y-current phases ij y (and generate
- x-traces 732B in excitation region 43B are driven with x-current phases h x (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 734B in excitation region 43B are driven with y-current phases ij y (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 732C in excitation regions 43C are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 734C in excitation region 43C are driven with y-current phases ij y (and generate corresponding magnetic fields) which travel with Xr+dr
- x-traces 732D in excitation regions 43D are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r + d r
- y-traces 732B in excitation regions 43D are driven with x-current phases 3
- coil traces 732A-732D, 734A-734D may be distributed over corresponding layers throughout at least a portion of their respective excitation regions 43A-43D.
- the current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in x-coil traces 732A will pull ID magnet array 712A in the positive stator-y direction
- the magnetic field traveling wave generated by current phases driven in y-coil traces 734B will pull ID magnet array 712B in the negative stator-x direction
- the magnetic field traveling wave generated by current phases drive in x-coil traces 732C region 43C
- the magnetic field traveling wave generated by current phases driven in y-coil traces 734D will pull ID magnet array 712D in the positive stator-x direction.
- stage 710 when stage 710 is in the configuration shown in Figure 2 IK, the y-current phases in traces 734A (region 43A), the x-current phases in traces 732B (region 43B), the y- current phases in traces 734C (region 43C) and the x-current phases in traces 732D (region 43D) will have minimal effect on stage 710, as their trace elongation directions are orthogonal to the elongation directions of the magnetization segments in their corresponding magnet arrays 712A, 712B, 712C, 712D.
- stage 710 starts to rotate in the counterclockwise direction (with d r ramping upwardly): the y-current phases in traces 734A (region 43 A) will start to pull magnet array 712A in the negative stator-x direction; the x- current phases in traces 732B (region 43B) will start to pull magnet array 712B in the negative stator-y direction; the y-current phases in traces 734C (region 43C) will start to pull magnet array 712C in the positive stator-x direction; and the x-current phases in traces 732D (region 43D) will start to pull magnet array 712D in the positive stator-y direction.
- magnet array assembly 716 will rotate counter-clockwise about its central z-oriented axis 771 in a counter-clockwise direction.
- magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of ⁇ in d r will result in a further 90° rotation around stator-z oriented axis 771.
- any controllable amount of rotation can be achieved. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
- Figure 22A shows another non-limiting example of magnet array assembly 816 which may be used for controllable 360° rotation according to a particular embodiment. Comparing Figure 22A to Figure 21A, it can be seen that magnet array assembly 816 of Figure 22A is similar to magnet array 716 of Figure 21 A, except that the relative orientation of magnet arrays 812A-812D in magnet array 816 is different than that of magnet arrays 712A-712D in magnet arrays 716.
- magnet array assembly 716 ( Figure 21 A) is a right-handed magnet array assembly and magnet array assembly 816 ( Figure 22 A) is a left-handed magnet array assembly (see descriptions of left-handed and right handed magnet array assemblies described above in connection with Figures 5 A and 5B).
- each magnet array 812A-812D has a stage-x dimension of 1 ⁇ and a stage-y dimension of 1 ⁇ , where it is assumed (for each of explanation and without loss of generality) that
- magnet array assembly 816 of Figure 22A can be controllably rotated by appropriate modification of the techniques described in Figures 20A, 20B and 21B-21J. Such techniques will be appreciated by those skilled in the art having regard to the teachings of this disclosure. A number of non- limiting examples of such techniques are shown in Figures 22B-22F.
- a displacement device 850 having a moveable stage 810 comprising the Figure 22A magnet array assembly 816 can be rotated about z-oriented axis 871 located at the stage-x/stage-y center 871 of magnet array 816.1n a manner analogous to Fi gure 21B described above, rotating magnet array 816 comprises driving y-current phases ijy into y-traces 834+ and into y-traces 834-.
- magnet array assembly 816 due to the left-handed pattern of magnet array assembly 816 (as compared to the right-handed pattern of magnet array 716), the same y-current phases ij y driven into the same y-traces (and the corresponding same magnetic field traveling waves) will result in rotation of magnet array assembly 816 (and its moveable stage 810) in opposite rotational directions than magnet array assembly 716 (and its moveable stage 710).
- Figure 22C shows a current driving method modified from 21 G to accommodate the left-handed magnet array assembly 816.
- magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises first and second pluralities of x-traces 832-', 832+' and first and second pluralities of y-traces 834-, 834+, similar to the system described in Figure 21G.
- First and second pluralities of x-traces 832+, 832- may be located on the same or different layers (e.g. at the same or different stator-z locations).
- First and second pluralities of y-traces 834+, 834- may be located on the same or different layers (e.g. at the same or different stator-z locations). However, for the left-handed magnet array assembly 816, the current driven into these traces is different than in Figure 21 G. More particularly, in Figure 22C, y-traces 834- are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel wit x r +d r and y-traces 834+ are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r .
- the x-current phases 3 ⁇ 4 driven into coil traces 832-' and 832+' may be similar to those driven into coil traces 732-' and 732+' for the Figure 21 G described above.
- magnet array assembly 816 will rotate counter-clockwise (in the view of Figure 22C), when d r is ramping up and clockwise when d r is ramping down.
- Figure 22D shows a current driving method modified from Figure 21 H to accommodate the left-handed magnet array assembly 816.
- magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises first and second pluralities of x- traces 832-, 832+ and first and second pluralities of y-traces 834-', 834+', similar to the system described in Figure 21H.
- First and second pluralities of x-traces 832+, 832- may be located on the same or different layers (e.g. at the same or different stator-z locations).
- First and second pluralities of y-traces 834+', 834-' may be located on the same or different layers (e.g. at the same or different stator-z locations). However, for the left-handed magnet array assembly 816, the current driven into these traces is different than in Figure 21H. More particularly, in Figure 22C, x-traces 832- are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r +d r and x-traces 832+ are driven with x- current phases (and generate corresponding magnetic fields) which travel with y r -d r .
- the y-current phases i jy driven into coil traces 834-' and 834+' may be similar to those driven into coil traces 734-' and 734+' for the Figure 21H described above.
- magnet array assembly 816 will rotate counter-clockwise (in the view of Figure 22D), when d r is ramping up and clockwise when d r is ramping down.
- Figure 22E shows a current driving method modified from Figure 21 J to
- magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises four independently driven current excitation regions 43A-43D.
- the Figure 22E illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of planes CC/DD coincides with stator-z oriented axis 871 in the stage-x-stage-y center 871 A of magnet array assembly 816 and/or moveable stage 810.
- Stator-z oriented axis 871 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 871.
- y-traces 834A in excitation region 43A are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -dr
- x-traces 832B in excitation region 43B are driven with x-current phases h x (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 834C in excitation regions 43 C are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r
- x-traces 732D in excitation region 43D are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r +d r .
- coil traces 834A, 832B, 834C, 832D may be distributed throughout at least a portion of their respective excitation regions 43A-43D.
- the current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in y-coil traces 834A will pull ID magnet array 812A in the negative stator-x direction
- the magnetic field traveling wave generated by current phases driven in x- coil traces 832B will pull ID magnet array 812B in the negative stator-y direction
- the magnetic field traveling wave generated by current phases drive in y-coil traces 834C will pull ID magnet array 812C in the positive stator-x direction
- the magnetic field traveling wave generated by current phases driven in x-coil traces 832D will pull ID magnet array 812D in the positive stator-y direction.
- magnet array assembly 816 will rotate around its central z-oriented axis 871 in a counterclockwise direction. For example, when d r increases by ⁇ , magnet array assembly 816 will rotate around the stator-z oriented axis 871 by 90°. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 816 will rotate around the stator-z oriented axis 871 in a clockwise direction.
- Figure 22F shows a current driving method similar to Figure 21 K for left-handed magnet array assembly 816.
- magnet array assembly 816 (and its
- stator 830 comprising a coil assembly 835, which comprises four independently driven current excitation regions 43A-43D having features similar to those of Figure 22E.
- y-traces 834A in excitation region 43A are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r , x-traces 832A in excitation region 43 A are driven with x-current phases h x (and generate
- x-traces 832B in excitation region 43B are driven with x-current phases h x (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 834B in excitation region 43B are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- y-traces 834C in excitation regions 43C are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r
- x-traces 832C in excitation region 43 C are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r - d r
- x-traces 732D in excitation region 43D are driven with x-current phases (and generate corresponding magnetic fields) which travel with y r +d r and y-traces 834
- coil traces 834A, 832B, 834C, 832D may be distributed throughout at least a portion of their respective excitation regions 43A-43D.
- the coil traces 832A-832D and 834A-834D in excitation regions 43A-43D and their corresponding drive current phases i jy are the same as coil traces 732A-732D and 734A-734D in excitation regions 43A-43D and corresponding drive current phases i jy of the Figure 21 K embodiment.
- magnet array assembly 816 and its corresponding moveable stage 810 will rotate counter-clockwise and when d r is negatively ramping down, magnet array assembly 816 and its corresponding moveable stage 810 will rotate clockwise.
- magnet array assembly 716 has a layout similar to magnet array assembly 416 A ( Figure 5 A) and that magnet array assembly 816 has a layout similar to a left-handed version of magnet array assembly 416A ( Figure 5 A).
- Any of the rotation techniques and coil trace assemblies 735, 835 described in Figures 20, 21 and 22 may be used with magnet array assembly 416A (or a left-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE.
- Figure 5B shows a left-handed magnet array assembly 416B that is different than magnet array assemblies 716 and 816 in that the individual magnet arrays of magnet array assembly 416B are offset and spaced apart from one another as described above.
- any of the rotation techniques and coil trace assemblies 735, 835 described in Figures 20, 21 and 22 may be used with magnet array assembly 416B (or a right-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE, by applying the operational methods and control algorithms described herein with appropriate modification.
- moveable stages 10 comprising 2D magnet array assemblies 16 may be capable of fully controllable 360° rotation about a stator-z oriented axis using current phases driven into coil traces having any two or more directions (e.g. x-current phases 3 ⁇ 4 driven into x-traces 32 and y-current phases i jy driven into y-traces 34).
- Such x-current phases 3 ⁇ 4 and y- current phases i jy could be similar to, and have any of the characteristics of, the current phases described above which vary with y r ⁇ d r and x r ⁇ d r - see Figures 20A, 20B and the
- FIG 23A shows one non- limiting example of magnet array assembly 916 comprising a magnet array 912 which may be used for controllable 360° rotation according to a particular embodiment.
- Magnet array assembly 916 and magnet array 912 of the Figure 23 A embodiment comprise a plurality of sub-arrays 921.
- each of sub-arrays 921 A, 921B, 921C, 921D may be similar to sub-array 321 of the embodiment shown in Figure 4D.
- each of sub- arrays 921 of magnet array assembly 916 may be similar to any of the other 2D sub-arrays 21 described herein.
- any 2D magnet array assembly 16 described herein can be used for the controllable 360° rotation operation, by applying the operational methods and control algorithms described herein with appropriate modification where desired.
- Magnet array assemblies 916 with 90° rotational symmetric property (about a z-oriented axis (e.g. axis 971)) are currently preferred.
- Magnet array assembly 916 of the Figure 23 A embodiment comprises a stage-x direction dimension of 2 ⁇ and a stage-y direction dimension of 2 y.
- the stage-x and stage-y direction dimensions of magnet array assembly 916 may comprise any positive integer number of its magnetic spatial period ⁇ and magnet array assembly 916 may comprise any positive integer number of sub-arrays 921.
- the magnetization directions of each magnetization segment in the Figure 23A illustration are shown with the conventional field direction annotations. In some embodiments, the magnetization directions of each of the magnetization segments in the Figure 23 A sub-arrays 921 could be reversed (i.e. have its magnetization direction changed by 180° for each magnetization segment).
- Figures 23B-23F illustrate possible coil traces 932, 934 and corresponding current phases ikx, ij y driven therein to operate the Figure 23 A magnet array assembly 916 to achieve controllable rotation.
- Figure 23B shows a top view of a displacement device 950 including a moveable stage 910 comprising the Figure 23 A magnet array assembly 916 which is moveable relative to a stator 930 comprising coil assembly 935.
- a stator-z oriented axis 971 extends through the stage-x-stagey center 971 A of magnet array assembly 916 and/or moveable stage 910 and coincides with a notional dividing plane CC, which extends in the stator-y and stator-z directions.
- first plurality 932- and second plurality 932+ of x-traces 932 that are elongated in the stator-x direction, where traces 932- represent the x-traces located on the negative stator-x side of dividing plane CC and traces 932+ represent the x-traces located on the positive stator-x side of dividing plane CC.
- Coil traces 932+ are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with y r +d r and coil traces 932- are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with y r -d r .
- first and second pluralities of x-current phases ikx can be independently driven into x-traces 932 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases ikx can be independently driven into two pluralities (i.e. groups) of x-traces 932 inside one excitation region 43.
- y r is not necessarily fixed in which case the techniques illustrated in Figure 23B permit moveable stage 910 to achieve simultaneous stator-y oriented translation and rotation about central stator-z oriented axis 971.
- the two types of traveling magnetic field waves i.e.
- those generated by the current phases driven in traces 932- and those generated by the current phases driven in traces 932+) will move with different characteristics: one moves ahead of y r by a distance d r and the other moves behind y r by a distance d r .
- the magnetic field traveling wave generated by current driven in coil traces 932+ will tend to pull the portion of magnet array 912 that is on the positive stage-x side of plane CC toward the positive stator-y direction relative to the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910; at the same time the magnetic field traveling wave generated by current driven in coil traces 932- will pull the portion of magnet array 912 that is on the negative stage-x side of plane CC toward the negative stator-y direction relative to stage-x-stage-y center 971 A of magnet array assembly 916.
- magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a counter-clockwise direction. If d r is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
- Figure 23C illustrates a method of controllably rotating magnet array assembly 916 and its corresponding moveable stage 910 using y-current phases i jy driven into first and second pluralities of y-traces 934+, 934-.
- the Figure 23C illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable sage 910.
- first plurality 934- and second plurality 934+ of y-traces 934 that are elongated in the stator-y direction, where traces 934+ represent the y-traces located on the negative stator-y side of dividing plane DD and traces 934- represent the y-traces located on the positive stator-y side of dividing plane DD.
- Coil traces 934+ are driven with y-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with x r +d r and coil traces 934- are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r .
- first and second pluralities of y-current phases i jy can be independently driven into y-traces 934 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of y-current phases i ky can be independently driven into two pluralities (i.e. groups) of y-traces 934 inside one excitation region 43.
- x r is not necessarily fixed in which case the techniques illustrated in Figure 23C permit moveable stage 910 to achieve simultaneous stator-x oriented translation and rotation about central stator-z oriented axis 971.
- the two types of traveling magnetic field waves i.e.
- those generated by the current phases driven in traces 934- and those generated by the current phases driven in traces 934+) will move with different characteristics: one moves ahead of x r by a distance d r and the other moves behind x r by a distance d r .
- the magnetic field traveling wave generated by current driven in coil traces 934+ will tend to pull the portion of magnet array assembly 916 that is on the negative stage-y side of plane DD toward the positive stator-x direction relative to the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910; at the same time the magnetic field traveling wave generated by current driven in coil traces 934- will tend to pull the portion of magnet array assembly 916 that is on the positive stage-y side of plane DD toward the negative stator-x direction relative to stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910.
- magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a counter-clockwise direction. If d r is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around central stator- z oriented axis 971 in a clockwise direction.
- some embodiments comprise rotating magnet array assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D.
- the Figure 23D illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator- x/stator-z directions and the intersection of panes CC/DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971A of magnet array assembly 916 and/or moveable stage 910.
- Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e.
- a corner of each of excitation regions 43A-43D is located at axis 971.
- x-traces 932A in excitation region 43A are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r + d r
- y-traces 934B in excitation region 43B are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 932C in excitation regions 43C are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 934D in excitation region 43D are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r .
- coil traces 932A, 934B, 932C, 934D may be distributed throughout at least a portion of their respective excitation regions 43A-43D.
- the current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932A (region 43 A) will pull the portion of magnet array assembly 916 located on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the positive stator-y direction;
- the magnetic field traveling wave generated by current phases driven in y-coil traces 934B (region 43B) will pull the portion of magnet array assembly 916 located on the negative stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-x direction;
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932C (region 43C) will pull the portion of magnet array assembly 916 located on the negative stage-x side of plane CC and the negative stage-y side of plane DD in the negative stator-y direction;
- the magnetic field traveling wave generated by current phases driven in y-coil traces 934D (region 43D) will pull the portion of magnet array assembly 916 located on the positive stage-x
- magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If d r is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around the stator-z oriented axis 971 in a clockwise direction.
- Figure 23E shows another technique for rotating magnet array assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D.
- the Figure 23E illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator- x/stator-z directions and the intersection of planes CC, DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971A of magnet array assembly 916 and/or moveable stage 910.
- Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e.
- y-traces 934A in excitation region 43A are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 932B in excitation region 43B are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r - d r
- y-traces 934C in excitation regions 43C are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r +d r
- x-traces 932D in excitation region 43D are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with y r +d r .
- coil traces 934A, 932B, 934C, 932D may be distributed throughout at least a portion of their respective excitation regions 43A-43D.
- the current phases driven into the coil traces in each of excitation regions 43 A- 43D create magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in y-coil traces 934A (region 43A) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and on the positive stage-y side of plane DD in the negative stator-x direction;
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932B (region 43B) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and on the positive stage-y side of plane DD in the negative stator-y direction;
- the magnetic field traveling wave generated by current phases drive in y-coil traces 934C (region 43C) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and on the negative stage-y side of plane DD in the positive stator-x direction;
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932D (region 43D) will pull the portion of magnet array assembly 916 on the positive stage-x side
- magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
- Figure 23F shows another embodiment which comprises rotating magnet array assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D.
- the Figure 23F embodiment may be considered to be a combination of techniques shown in Figures 23D and 23E.
- the Figure 23F illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of the planes CC, DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910.
- Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 971.
- x-traces 932A in excitation region 43A are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r + d r
- y-traces 934A in excitation region 43A are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 932B in excitation region 43B are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r -d r
- y-traces 934B in excitation region 43B are driven with y-current phases i jy (and generate corresponding magnetic fields) which travel with x r -d r
- x-traces 932C in excitation regions 43C are driven with x-current phases 3 ⁇ 4 (and generate corresponding magnetic fields) which travel with y r - d r
- y-traces 934C in excitation regions 43C are driven with x-
- coil traces 932A-932D, 934A-934D may be distributed over corresponding layers throughout at least a portion of their respective excitation regions 43 A- 43D.
- the current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions.
- d r is positively ramping up (i.e.
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932 A will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the positive stator-y direction and the magnetic field traveling wave generated by current phases driven in y-coil traces 934A (region 43A) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-x direction;
- the magnetic field traveling wave generated by current phases driven in x-coil traces 932B region 43B will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-y direction and the magnetic field traveling wave generated by current phases driven in y-coil traces 934B (region 43B) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC
- magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If d r is negatively ramping (i.e. decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
- displacement device 150 of the Figure 3 embodiment may be used for a particular application, wherein part holder 119 carries a glass or plastic tube 119 A, which may contain biological samples 119B, for example.
- Moveable stage 110 may, for example, carry biological samples 119B to travel between different biological sample analyzers for biological content analysis.
- Figure 24 depicts another exemplary embodiment showing a displacement device 1050 of any of the types described herein used for another particular application.
- On stator 1030 there are many moveable stages 1010. Each moveable stage 1010 may carry a particular biological sample. Samples can be sent to different analyzers 1075 based on user input, such as a doctor's recommendation.
- Moveable stages 1010 may carry samples in or out of an analyzer 1075.
- a moveable stage 1010 may carry samples and have a full 360° controllable rotation so that, for example, a sample label on tube 119A ( Figure 3) can be scanned (e.g. by a barcode reader, a RFID reader and/or the like) to verify its identification.
- Arrows in Figure 24 show possible motion directions of each moveable stage 1010. The flexibility of moving in the stator-x and stator-y directions and rotating around a stator-z direction axis of this displacement devices make it very suitable for many applications, such as this application.
- Certain implementations of the invention comprise controllers, computers and/or computer processors which execute software instructions which cause the controllers, computers and/or processors to perform a method of the invention.
- one or more processors in a controller or computer may implement data processing steps in the methods described herein by executing software instructions retrieved from a program memory accessible to the processors.
- the invention may also be provided in the form of a program product.
- the program product may comprise any medium which carries a set of computer- readable signals comprising instructions which, when executed by a data processor, cause the data processor to execute a method of the invention.
- Program products according to the invention may be in any of a wide variety of forms.
- the program product may comprise, for example, physical (non-transitory) media such as magnetic data storage media including floppy diskettes, hard disk drives, optical data storage media including CD ROMs, DVDs, electronic data storage media including ROMs, flash RAM, or the like.
- the instructions may be present on the program product in encrypted and/or compressed formats.
- a component e.g. a software module, controller, processor, assembly, device, component, circuit, etc.
- reference to that component should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.
- a combination of skewed coil traces and slanted magnet arrays may also be usefully implemented to eliminate internal stresses in the magnetic arrays while reducing or minimizing the effects of the interaction of current carrying coil traces with higher order harmonics of the magnetic fields of the magnet arrays.
- Coil traces may be fabricated using techniques other than PCB technology. Any
- conductor that is or may be shaped to be generally linearly elongated may be used to provide coil traces.
- stator and stage bearing surfaces are generally flat (e.g. planar). This is not necessary.
- stator and stage bearing surfaces may comprise complementarily curved surfaces.
- stage-z and stator-z may be understood to be oriented parallel to the direction of the normal of such curved bearing surfaces.
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Abstract
A displacement device comprise a stator having a plurality of electrically conductive coils shaped to provide: a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer; a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer. The first and second portions of the first and second layers overlapping one another in a stator-z direction. The displacement device also comprises a moveable stage having one or more magnet arrays. The moveable stage is moveable relative to the stator within a two-dimensional working region. The one or more magnet arrays include a first magnet array comprising a plurality of first magnetization segments, each having a corresponding first magnetization direction. The displacement device comprises one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils; and a controller configured to control the currents driven by the one or more amplifiers and to thereby cause the moveable stage to track a desired position, (x
r
,y
r ), within the working region.
Description
DISPLACEMENT DEVICES AND METHODS FOR FABRICATION, USE AND
CONTROL OF SAME
Related Applications
[0001] This application claims the benefit of the priority of US application No. 62/004907 filed 30 May 2014, which is hereby incorporated herein by reference.
Technical Field
[0002] The invention relates to displacement devices. Particular non-limiting embodiments provide displacement devices for use in the semi-conductor fabrication industry and for use in sample transfer for automated in-vitro diagnostics.
Background
[0003] Displacement devices typically comprise moveable stages which move relative to a stator and/or relative to an environment in which they are located. Displacement devices are widely used in various manufacturing, inspection, sample/part transfer, and assembly processes. A common solution currently in use achieves XY (i.e. planar) motion of the moveable stage using a toothed belt chain transfer system. Another common solution currently in uses achieves XY motion of the moveable stage by stacking two linearly moveable stages (i.e. an X-stage and a Y-stage) together via connecting bearings.
[0004] Some generally more desirable solutions involve having one or more moveable stages capable of XY (i.e. planar) motion and, where a displacement device comprises more than one moveable stage, allowing more than one of such moveable stages to share a common working region and/or a common stator. It might be desirable for such a moveable stage to be able to provide two-dimensional programmable motion. Attempts have been made to design such displacement devices using the interaction between current-carrying coils and permanent magnets. Examples of efforts in this regard include the following: US patent No. 6,003,230; US patent No. 6,097,114; US patent No. 6,208,045; US patent No.6,441,514; US patent No. 6,847,134; US patent No. 6,987,335; US patent No. 7,436,135; US patent No. 7,948,122; US Patent No. 8,593,016; US Patent No. 8,686,602; US patent publication No. 2008/0203828; W.J. Kim and D.L. Trumper, High-precision magnetic levitation stage for
photolithography. Precision Eng. 22 2 (1998), pp. 66-77; D.L. Trumper, et al, "Magnet arrays for synchronous machines", IEEE Industry Applications Society Annual Meeting, vol.1 , pp. 9 - 18, 1993; and J.W. Jansen, C.M.M. van Lierop, E.A. Lomonova, A.J.A.
Vandenput, "Magnetically Levitated Planar Actuator with Moving Magnets", IEEE Tran. Ind. App.,Vol 44, No 4, 2008.
[0005] There is a general desire to provide displacement devices having characteristics that improve upon those known in the prior art.
[0006] The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
Brief Description of the Drawings
[0007] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.
[0008] Figure 1 A is a schematic top view of a displacement device according to a particular embodiment.
[0009] Figure IB is an exploded side view of a portion of the Figure 1 A a displacement device.
[0010] Figure 2 is a top view of a displacement device which comprises a plurality of moveable stages.
[0011] Figure 3 is a exploded partial schematic side view of a displacement device according to a particular embodiment of the invention.
[0012] Figure 4A-4D are each a schematic top view of a 2D magnet array assembly comprising a 2D magnet array according to a particular embodiment.
[0013] Figure 4E is a schematic top view of a displacement device incorporating a pair of moveable stages, each moveable stage comprising one of the Figure 4A magnet arrays.
[0014] Figures 5A and 5B are each a schematic top view of a magnet array assembly comprising a plurality of ID magnet arrays according to a particular embodiment. Figure 5C is a cross-sectional view of an exemplary y-magnet array which is used in Figure 5A magnet array assembly and which could be used for the magnet array assemblies of Figure 5B or any
of the other ID magnet array assemblies described herein. Figure 5D is a cross-sectional view of an exemplary y-magnet array which is used in Figure 5B magnet array assembly and which could be used for the magnet array assemblies of Figures 5A or any of the other ID magnet array assemblies described herein.
[0015] Figures 6A-6T are cross-sectional views of exemplary y-magnet arrays which may be used in the magnet array assemblies of Figures 5A, 5B or any of the other ID magnet array assemblies described herein.
[0016] Figure 7 is a top cross-sectional view of the Figure 3 moveable stage according to a particular embodiment showing its non- magnetic bumpers.
[0017] Figure 8A shows a schematic top view of a stator coil assembly according to a particular embodiment which may be used in any of the displacement devices described herein. Figure 8B shows a schematic top view of a single layer of the Figure 8A stator coil assembly according to a particular embodiment, where the individually controllable coil traces in each excitation region all have the same orientation. Figure 8C shows a schematic top view of a single layer of the Figure 8A stator coil assembly according to a particular embodiment, where the individually controllable coil traces in each excitation region have different orientations.
[0018] Figures 9A-9D each show schematic depictions of portions of coil traces in a corresponding excitation region according to a particular embodiment.
[0019] Figure 10 is a schematic depiction of an excitation region which forms part of a working region associated with a stator coil assembly according to an example embodiment.
[0020] Figures 11 A and 1 IB respectively depict cross-sectional views of the same magnet array assembly supported by a non-magnetic stage support structure and an iron-based stage support structure.
[0021] Figure 12 is a schematic partial cross-sectional view of a stator bearing layer which comprises a restrictor layer and can be used to create an air bearing according to a particular embodiment.
[0022] Figure 13 A shows a schematic block diagram of a control system suitable for use in controlling any of the displacement devices described herein according to a particular embodiment. Figure 13B shows one possible connection scheme to connect a plurality of y- coil traces in one coil trace layer within an excitation region according to a particular
embodiment. Figures 13C and 13D respectively schematically depict an x-trace layout in a first layer and a y-trace layout in a second layer of an exemplary excitation region according to a particular embodiment. Figures 13E and 13F show a pair of stator-z direction configurations for coil layers according to a pair of exemplary embodiments. Figure 13G shows a number of first control signals according to a particular embodiment.
[0023] Figure 14A shows a partial schematic illustration of a np -phase coil layout in an x- trace layer of an excitation region according to a particular embodiment. Figure 14B shows the current waveforms x, ijx as a function of desired stator-y location yr for a moveable stage according to particular embodiment.
[0024] Figure 15 A shows amplitude Ax and phase ψχ impulses for an x-current phase hx according to a particular embodiment. Figure 15B shows a series of amplitude Ax and phase ψχ impulses for an x-current phase ¾ according to a particular embodiment. Figure 15C shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse is applied to the x-current phases ¾ before a second amplitude impulse is applied to the y-current phases ijy. Figure 15D shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse is applied to the x-current phases ¾ before a second amplitude impulse is applied to the y-current phases ijy.
[0025] Figure 16A is a schematic depiction of how a one-by-one initialization process may be used to determine an initial location of a moveable stage in a displacement device according to a particular embodiment. Figure 16B depicts an alignment device according to another embodiment which may be used with the displacement device and the one -by-one initialization process of Figure 16A. Figure 16C schematically depicts a displacement device comprising a stator and a plurality of moveable stages which uses a group initialization technique for determining the initial positions of the moveable stages according to a particular embodiment.
[0026] Figure 17A schematically depicts shows the working region of a stator divided into a plurality of excitation regions according to an example embodiment. Figure 17B
schematically depicts a moveable stage suitable for use with the Figure 17A stator. Figures 17C-17H depict schematic top views of motion patterns of a plurality of moveable stages (like the one of Figure 17B) relative to a stator (like the one of Figure 17A) according to
particular embodiments.
[0027] Figures 18A-18F schematically illustrate one exemplary embodiment of a process of a number of the Figure 17B moveable stages 10 ungrouping from one another.
[0028] Figures 19A-19G schematically depict a technique for implementing rotational motion of a moveable stage about a stator-z oriented axis according to a particular embodiment.
[0029] Figures 20A and 20B respectively depict the generation of y-current phases ijy and x- current phases which may be used to achieve controllable 360° rotation about a stator-z oriented axis according to a particular embodiment.
[0030] Figure 21 A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment. Figures 21B-21K illustrate possible coil traces and corresponding current phases ijy driven therein to operate the Figure 21 A magnet array assembly to achieve controllable rotation.
[0031] Figure 22A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment. Figures 22B-22F illustrate possible coil traces and corresponding current phases ijy driven therein to operate the Figure 22A magnet array assembly to achieve controllable rotation.
[0032] Figure 23A shows one non-limiting example of magnet array assembly which may be used for controllable 360° rotation according to a particular embodiment. Figures 23B-23F illustrate possible coil traces and corresponding current phases ijy driven therein to operate the Figure 23A magnet array assembly to achieve controllable rotation.
[0033] Figure 24 depicts another exemplary embodiment showing a displacement device of any of the types described herein used for another particular application.
Description
[0034] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
[0035] Aspects of the invention provided displacement devices which comprise a stator and
one or more moveable stages. The stator comprises a plurality of electrically conductive coils shaped to provide pluralities of generally linearly elongated coil traces. In some
embodiments, the electrically conductive coils may be shaped to provide a first plurality of coil traces which are generally elongated in a stator-x direction and a second plurality of coil traces generally elongated in a stator-y direction which may be generally orthogonal to, or otherwise non-parallel to the stator-x direction. The first and second pluralities of coil traces may be provided in portions of first and second layers. The portions of the first and second layers may be located at the same stator-z location or at different stator-z locations. Portions of layers at different stator z- locations may overlap each other in the stator-z direction. In some embodiments, a first portion of a first layer comprises a plurality of coil traces generally elongated in the stator-x direction and a stator-z direction overlapping first portion of a second layer comprises a plurality of coil traces generally elongated in the stator-y direction; and a second portion of the first layer comprises a plurality of coil traces generally elongated in the stator-y direction and a stator-z direction overlapping second portion of the second layer comprises a plurality of coil traces generally elongated in the stator-x direction. The moveable stage may be controllably moveable relative to the stator within two-dimensional working region.
[0036] Each moveable stage may comprise one or more magnet arrays. In some
embodiments, each magnet array comprises a plurality of magnetization segments, where each magnetization segment has a corresponding magnetization direction. Each magnet array may comprise at least two magnetization segments with different magnetization directions. One or more amplifiers may be connected to drive a plurality of currents in the plurality of electrically conductive coils. A controller may be connected to deliver signals to the one or more amplifiers. The signals may be used to control current driven by the one or more amplifiers into at least some of the plurality of coil traces and to thereby cause the moveable stage to track a desired position in the working region - e.g. a desired position, (xr,yr), within the working region, where xr is a desired position of the moveable stage in the stator-x direction and yr is a desired position of the moveable stage in the stator-y direction. Unless the context dictates otherwise, throughout this disclosure and the accompanying claims, when referring to a position of the moveable stage, a location of the moveable stage, movement of the moveable stage generally within the working region and/or the like, such position,
location, movement and/or the like should be understood to refer to the position, location, movement and/or the like of a reference point on the moveable stage. Such reference point may be, but is not limited to, a point at the center of the magnet array assembly of the moveable stage. Such reference point could be some other location on the moveable stage. Generally, the desired position (xr,yr) is a function of time, t, and represents where a moveable stage should be ideally located at each time, t. The currents controllably driven into the at least some of the plurality of coil traces create magnetic fields which cause
corresponding magnetic forces on the one or more magnet arrays of the moveable stage. In some embodiments, the magnetic forces associated with the interaction between the magnetic fields created by the currents in the at least some of the coil traces and the magnetic fields associated with the magnet arrays may attract the moveable stage toward the stator at all times when the controller is controlling the currents driven by the one or more amplifiers. In some embodiments, the magnetic fields associated with the magnet arrays may push the moveable stage away from the stator to balance gravitational forces with an air gap at all times when the controller is controlling the currents driven by the one or more amplifiers.
[0037] For purposes of describing the displacement devices disclosed herein, it can be useful to define a pair of coordinate systems - a stator coordinate system which is fixed to the stator (e.g. to stator 30 of Figure 1 A); and a stage coordinate system which is fixed to the moveable stage (e.g. moveable stage 10 of Figure 1 A) and moves with the moveable stage relative to the stator and the stator coordinate system. This description may use conventional Cartesian coordinates (x, y, z) to describe these coordinate systems, although, it will be appreciated that other coordinate systems could be used. For convenience and brevity, in this description and the associated drawings, the directions (e.g. x, y, z directions) in the stator coordinate system and the directions in the stage coordinate system may be shown and described as being coincident with one another - i.e. the stator-x, stator-y and stator-z directions may be shown as coincident with stage-x, stage-y and stage-z directions, respectively. Accordingly, this description and the associated drawings may refer to directions (e.g. x, y, and/or z) to refer to directions in both or either of the stator and stage coordinate systems. However, it will be appreciated from the context of the description herein that in some embodiments and/or circumstances, the moveable stage (e.g. moveable stage 10) may move relative to the stator (e.g. stator 30) such that these stator and stage directions are no longer coincident with one
another. In such cases, this disclosure may adopt the convention of using the terms stator-x, stator-y and stator-z to refer to directions in the stator coordinate system and the terms stage- x, stage-y and stage-z to refer to directions in the stage coordinate system. In this description and the associated drawings, the symbols Xm, Ym and Zm may be used to refer respectively to the stage-x, stage-y and stage-z directions, the symbols Xs, Ys and Zs may be used to refer respectively to the stator-x, stator-y and stator-z directions and the symbols X, Y and Z may be used to refer respectively to either or both of the stage-x, stage-y and stage-z and/or stator- x, stator-y and stator-z directions. In some embodiments, during normal operation, the stage-z and stator-z directions are approximately in the same direction (e.g. within ±30° in some embodiments; within ±10° in some embodiments; and within ±2° in some embodiments).
[0038] In some embodiments, the stator-x and stator-y directions are non-parallel. In particular embodiments, the stator-x and stator-y directions are orthogonal. In some embodiments, the stage-x and stage-y directions are non-parallel. In particular embodiments, the stage-x and stage-y directions are orthogonal.
[0039] Figures 1A and IB (together, Figure 1) respectively depict a schematic partially cutaway top view and side cross-sectional views of a displacement device 50 according to a particular embodiment of the invention. Displacement device 50 comprises a stator 30, a moveable stage 10, a controller 60 and one or more amplifiers 70.
[0040] Stator 30 comprises a stator coil assembly 35 which comprises at least the traces of a plurality of electrically conductive coils 31. Electrically conductive coils 31 may be shaped to provide a first plurality of coil traces 32A, 32B, 32C (collectively, first coil traces 32). Coil traces 32 may be distributed over at least a portion of a first layer 40 at a corresponding first stator-z location and generally elongated in the stator-x direction. Electrically conductive coils may also be shaped to provide a second plurality of coil traces 34A, 34B, 34C
(collectively, second coil traces 34) distributed over at least a portion of a second layer 42 at a corresponding second stator-z location and generally elongated in a stator-y direction.
Because of their respective elongation directions, first coil traces 32 may be referred to herein as x-coil traces 32 or x- traces 32 and second coil traces 34 may be referred to as y-coil traces 34 or y-traces 34. In particular embodiments, such as depicted in Figure 1, the stator-x elongation direction of first coil traces 32 is orthogonal to the stator-y elongation direction of second coil traces 34. This is not necessary. In some embodiments, first coil traces 32 are
merely non-parallel to second coil traces 34. In the particular case of Figure 1, stator 30 comprises a pair of layers and corresponding first and second pluralities of coil traces 32. 34. In some embodiments, stator 30 may comprise additional layers and corresponding additional pluralities of coil traces which may be elongated in the stator-x direction, the stator y- direction or other suitable directions.
[0041] Coil traces 32, 34 in layers 40, 42 overlap one another in the stator-z direction. The two dimensional space over which coil traces 32, 34 overlap one another in the stator-z direction may define a working region 36 over which moveable stage 10 is moveable relative to stator 30. In some embodiments, the span of working region 36 (in the stator-x and stator-y directions) may be larger than moveable stage 10 (and may be much larger than moveable stage 10) to permit moveable stage 10 to move within working region 36, although this is not necessary. It should be noted that the schematic illustrations of Figure 1 show only portions of a relatively small number of traces 32, 34 and it is understood that coil traces 32, 34 in each corresponding layer 40, 42 may be distributed throughout their respective layers 40, 42 so that coil traces 32, 34 and/or layers 40, 42 may overlap in the stator-z direction at all locations in working region 36. Some of coil traces 32, 34 may be connected at their ends to form a two-phase, three-phase, or multiple -phase winding configuration as described in more detail below. While working region 36 is a two-dimensional space, this description may describe working region 36 as a feature of stator 30, for convenience.
[0042] Moveable stage 10 comprises a magnet array assembly 16 which comprises one or more magnet arrays 12. Magnet array assembly 16 should be understood to comprise the combination of the one or more individual magnet arrays 12. Each magnet array 12 may comprise a corresponding plurality of magnetization segments 14A, 14B, 14C, 14D ...
(collectively, magnetization segments 14), each magnetization segment 14 having a corresponding magnetization direction. In some embodiments, the magnetization segments 14 of a particular magnet array 12 have at least two magnetization directions that are different from one another. In the Figure 1 embodiment, moveable stage 10 comprises a first magnet array 12 having a plurality of corresponding first magnetization segments 14. Moveable stage 10 may be located immediately adjacent to and may bear against stator 30. In the illustrated embodiment, moveable stage 10 comprises a stage bearing surface 24 that is generally planar (with a normal in the stage-z direction) and which bears against a generally planar stator
bearing surface 26 (with a normal in the stator-z direction). Accordingly, when operating with this configuration, stage bearing surface 24 is generally parallel to the planes of stator layers 40, 42 in which coil traces 32, 34 are located.
[0043] Displacement device 50 comprises one or more amplifiers 70 which are connected (e.g. with suitable electrical connections (not expressly shown in Figure 1)) to drive a plurality of currents into coil traces 32, 34. Amplifier(s) 70 are controlled by controller 60. Controller 60 (and components thereof) may comprise hardware, software, firmware or any combination thereof. For example, controller 60 may be implemented on a programmed computer system comprising one or more processors, user input apparatus, displays and/or the like. Controller 60 may be implemented as an embedded system with a suitable user interface comprising one or more processors, user input apparatus, displays and/or the like. Processors may comprise microprocessors, digital signal processors, graphics processors, field programmable gate arrays, and/or the like. Components of controller 60 may be combined or subdivided, and components of controller 60 may comprise sub-components shared with other components of controller 60. Components of controller 60, may be physically remote from one another. Controller 60 may be connected (e.g. with suitable electrical connections (not expressly shown in Figure 1)) to deliver signals to amplifier(s) 70. Controller 60 may be configured (e.g. using suitable software, logic configuration and/or the like) to use those signals to control the currents driven by amplifier(s) 70 into at least some of first coil traces 32 and at least some of second coil traces 34 to thereby cause moveable stage 10 to track a desired position within working region 36 - e.g. a desired position, (xr,yr), within working region 36, where xr is a desired position of moveable stage 10 in the stator-x direction and yr is a desired position of moveable stage 10 in the stator-y direction.
[0044] In the Figure 1 embodiment, displacement device 50 is shown with a single moveable stage 10. In general, however, displacement device 50 may comprise a plurality of moveable stages, each of which may be similar to moveable stage 10 and each of which may be controlled by controller 60 using amplifier(s) 70 to drive currents in coil traces 32, 34 as described herein. Figure 2 shows a top view of displacement device 50', which comprises a plurality (e.g. two) moveable stages 10A, 10B. In other respects, displacement device 50' may be substantially similar to the Figure 1 displacement device 50. Figure 2 also shows that moveable stages 10A, 10B need not be aligned with one another and so each moveable stage
10A, 10B may be described using its own corresponding stage coordinate system. In the case shown in Figure 2, the stage directions Xmi/Ymi/Zmi define the stage coordinate system for moveable stage 10A and the stage directions Xm2 Ym2 Zm2 define the stage coordinate system for moveable stage 10B. Displacement device 50' can be built to operate with any suitable number of moveable stages 10. In some embodiments, displacement device 50' comprises three moveable stages. In some embodiments, displacement device 50' may comprise dozens to hundreds of moveable stages. In some embodiments still, displacement device 50' may comprise thousands of moveable stages.
[0045] It should be understood that Figure 1 provides a general embodiment of displacement device 50. Unless the context dictates otherwise, further embodiments described herein (e.g. displacement devices 150, 250, 350, etc.) may use like numbering to show that they are particular embodiments of displacement device 50. For example, displacement device 150 is a particular embodiment of displacement device 50. Displacement device 150 comprises a moveable stage 110, which is a particular embodiment of moveable stage 10, a stator 130, which is a particular embodiment of stator 30 and so on. Similarly, displacement device 250 is a particular embodiment of displacement device 50 that comprises a moveable stage 210, which is a particular embodiment of moveable stage 10, a stator 230 which is a particular embodiment of stator 30 and so on. Further, unless the context dictates otherwise, it should also be understood that when referring to generic displacement device 50 or a part thereof (e.g. moveable stage 10, stator 30 and/or the like.), the corresponding description should be understood to apply to any of the particular embodiments of displacement devices 150, 250, 350, etc. and parts thereof (e.g. moveable stages 110, 210, 310 etc., stators 130, 230, 330 etc. and/or the like).
[0046] Figure 3 is an exploded partial schematic side view of a displacement device 150 according to a particular embodiment of the invention. Displacement device 150 comprises a moveable stage 110 and a stator 130. In the Figure 3 depiction, moveable stage 110 is shown exploded (i.e. spaced apart) from stator 130. In general, however, moveable stage 110 will be located immediately adjacent to and may bear on stator 130. In the Figure 3 embodiment, moveable stage 110 comprises a stage bearing surface 124 which may be generally planar and which is parallel with and adjacent to (and may bear against) stator bearing surface 126 of stator 130, which also may be generally planar. In some embodiments, displacement
device may comprise more than one moveable stage 110.
Moveable Stage
[0047] As discussed above, moveable stage 10 comprises a magnet array assembly 16 comprising one or more magnet arrays 12. Each magnet array comprises a plurality of magnetization segments 14 having corresponding magnetization directions. In some embodiments, the magnetization directions of at least two magnetization segments 14 are different from one another.
[0048] In the Figure 3 embodiment, moveable stage 110 of displacement device 150 comprises a magnet array assembly 116 comprising one or more magnet arrays (not expressly shown in Figure 3) having the features of the magnet arrays 12 described herein. Moveable stage 110 of the Figure 3 embodiment also includes a number of optional features comprising one or more bumpers 117, stage bearing layer 118 (which provides stage bearing surface 124), one or more part holders 119, and a stage support structure 120. Each part holder 119 may be configured to hold a part 119A. In some applications, each part holder 119 may hold a plurality of parts 119A. By way of non- limiting example, part 119A may comprise one or more glass/plastic tubes containing biological samples. Stage support structure 120 may function to provide a framework to which other components of moveable stage 110 may be mounted or otherwise supported. Stage bearing layer 118 can be located between magnet array assembly 116 and stator 130 to provide stage bearing surface 124, which may be generally planar.
Magnet Arrays
[0049] Displacement device 50 may comprise any one or more of a variety of embodiments of magnet array assembly 16. Unless otherwise specified, embodiments of magnet array assemblies 16 shown in this document are illustrative rather than restrictive. There are many other possible permutations for each embodiment of magnet array assemblies 16. For example, the magnetization directions of the permanent magnet pieces/elements/segments (e.g. magnetization segments 14) in a magnet array assembly 16 may all be inverted (i.e. 180° changes in magnetization direction), in which case the resulting magnet array assembly 16 could still be used in a corresponding displacement device to achieve the desired motion by
suitable adjustment of the corresponding currents in coil traces 32, 34 (e.g. by suitable configuration of controller 60 and/or amplifier(s) 70). Two general types of magnet array assemblies 16 are described herein for use with displacement device 50. These types of magnet array assemblies may be referred to as 2D magnet array assemblies and ID magnet array assemblies.
2D Magnet Array Assemblies
[0050] One type of magnet array assembly that can be used with any of the displacement devices disclosed herein is referred to as a 2D magnet array assembly 16. A 2D magnet array assembly 16 comprises one or more 2D magnet arrays 12. In some embodiments, 2D magnet arrays 12 may comprise one or more sub-arrays 21. Figure 4A is a schematic top view of a 2D magnet array assembly 216 A comprising a 2D magnet array 212A according to a particular embodiment. In the Figure 4A embodiment, magnet array 212A comprises a single sub-array 221, which in turn comprises a plurality (e.g. five) magnetization segments 214A, 214B, 214C, 214D, 214E. Each sub-array 221 may comprise a central magnetization segment (e.g. central magnetization segment 214E in the Figure 4A embodiment) and a plurality of additional magnetization segments (e.g. additional magnetization segments 214A, 214B, 214C, 214D in the Figure 4A embodiment). Each additional magnetization segment 214A, 214B, 214C, 214D comprises an edge which abuts against a corresponding peripheral edge of central magnetization segment 214E. For example, in the illustrated embodiment of Figure 4A, edge 214D-1 of additional magnetization segment 214D abuts against peripheral edge 214E-1 of central magnetization segment 214E.
[0051] Each of magnetization segments 214A, 214B, 214C, 214D, 214E comprises a corresponding magnetization direction. Central magnetization segment 214E may have a first magnetization direction opposed to a second magnetization direction of additional magnetization segments 214A, 214B, 214C, 214D. For example, in the illustrated embodiment of Figure 4A, the letter N indicates that central magnetization segment 214E has its magnetic north pole facing out of the page (and magnetization direction in the positive Zm direction) and the letters S indicates that additional magnetization segments 214A, 214B, 214C, 214D have their magnetic south pole facing out of the page (and magnetization direction in the negative Zm direction). Note that this convention is used throughout this
description and the accompanying drawings. In some embodiments, the magnetization directions of each of the magnetization segments 214 in the Figure 4A sub-arrays 221 could be reversed (i.e. have its magnetization direction changed by 180°) with suitable adjustment of controller signals and/or control algorithm(s).
[0052] A stage-x dimension (i.e. a length in a stage-x direction) of sub-array 221 may be generally equal to a spatial period λ¾ and a stage-y dimension of sub-array 221 may be generally equal to a spatial period λγ. The stage-x and stage-y spatial periods λΧι λγ may also be referred to as λ2, λι (i.e. λχ = λ2 and Xy = λ^. The significance of spatial periods λΧι λγ is explained in more detail below. These spatial periods λΧι λγ may be the same as the spatial periods of the currents driven in coil traces 32, 34. In some embodiments, such as is illustrated in the Figure 4A embodiment, the stage-x and stage y-dimensions (e.g. λχ and λγ) of sub-array 221 are generally equal to one another. This is not necessary. In general, the stage-x and stage y-dimensions (e.g. λ¾ and Xy) of sub-array 221 may be different from one another.
[0053] Figure 4B is a schematic top view of a 2D magnet array assembly 216B comprising a 2D magnet array 212B according to a particular embodiment. In the Figure 4B embodiment, magnet array 212B comprises a plurality (e.g. four) of sub-arrays 221A, 221B, 221C, 221D (collectively sub-arrays 221). Each of sub-arrays 221 is substantially similar to sub-array 221 of Figure 4A. In the Figure 4B embodiment, each of sub-arrays 221 comprises at least one edge (e.g. one or a pair of edges), each of which abuts against a corresponding edge of a different one of sub-arrays 221. For example, edge 221 A' of sub-array 221 A abuts against corresponding edge 221B' of sub-array 221B and edge 221A" of sub-array 221A abuts against corresponding edge 221D" of sub-array 221D, as illustrated in Figure 3B. Such edge abutment is not generally necessary. In some embodiments, each sub-array 221 may comprise a single edge which abuts against a corresponding edge of another sub-array 221. In some embodiments, sub-arrays 221 may not have abutting edges. In some embodiments, each sub- array 221 and its corresponding magnetization segments 214 may be separately fabricated. This is the case in the illustrated embodiment of Figure 4B. In some embodiments, magnetization segments 214 having a unitary construction may be shared between sub-arrays 221. For example, in the Figure 4B embodiment, magnetization segments 214AC (of sub- array 221 A), 214BB (of sub-array 221B), 214CA (of sub-array 221C) and 214DD (of sub-
array 22 ID) may be fabricated from a single unitary magnet. In some embodiments, the magnetization directions of each of the magnetization segments 214 in the Figure 4B sub- arrays 221 could be reversed (i.e. have its magnetization direction changed by 180°).
[0054] As was the case with magnet array 212A (Figure 4A), the stage-x dimension of each sub-array 221 in magnet array 212B may be generally equal to the spatial period λχ and the stage-y dimension of each sub-array 221 in magnet array 212B may be generally equal to the spatial period λγ. In the Figure 4B embodiment, because magnet array 212B comprises four identical sub-arrays 221 located such that pairs of sub-arrays 221 are aligned with and abut against each other in the stage-x and stage-y directions, the overall stage-x and stage-y dimensions of magnet array 212B are generally equal to 2λχ, 2Xy respectively. The significance of the dimensions λΧι λγ as spatial periods is more discernable from the Figure 4B embodiment, where it can be seen that the magnetization direction of magnet array 212A is periodic in the stage-x direction with the spatial period λχ and in the stage-y direction with the spatial period λγ.
[0055] As was the case with magnet array 212A, in some embodiments, the spatial periods λχ, λγ of magnet array 212B are generally equal to one another, but this is not necessary.
Figure 4C is a schematic top view of a 2D magnet array assembly 216C comprising a 2D magnet array 212C according to a particular embodiment. In the Figure 4C embodiment, magnet array 212C comprises a single sub-array 22Γ which may be substantially similar to sub-arrays 221 described herein except that the stage-x and stage-y dimensions (spatial periods λχ, Xy) are different from one another. In the illustrated embodiment, Xx>Xy. In some embodiments, a magnet array could comprise a plurality of such sub-arrays 22Γ with different stage-x and stage-y dimensions (spatial periods λχ, λγ). In some embodiments, the magnetization directions of each of the magnetization segments in the Figure 4C sub-array
221 could be reversed (i.e. have its magnetization direction changed by 180°).
[0056] Figure 4D is a schematic top view of a 2D magnet array assembly 316D comprising a
2D magnet array 312D according to a particular embodiment. In the Figure 4D embodiment, magnet array 312D comprises one or more sub-arrays 321 (one of which is shown in Figure
4D). Each sub-array comprises a plurality (e.g. nine) magnetization segments 314A-314I and each magnetization segment has a corresponding magnetization direction. In the Figure 4D embodiments, each sub-array 321 comprises a central magnetization segment (e.g. central
magnetization segment 314E in the Figure 4D embodiment), a plurality of additional magnetization segments (e.g. additional magnetization segments 314F, 314G, 314H, 3141 in the Figure 4D embodiment) and a plurality of peripheral magnetization segments (e.g.
peripheral magnetization segments 314A, 314B, 314C, 314D in the Figure 4D embodiment). Like sub-array 221 described above, each additional magnetization segment 314F, 314G, 314H, 3141 comprises an edge which abuts against a corresponding peripheral edge of central magnetization segment 314E. For example, in the illustrated embodiment of Figure 4D, edge 314G-1 of additional magnetization segment 314G abuts against peripheral edge 314E-1 of central magnetization segment 314E. Also, each peripheral magnetization segment 314A, 314B, 314C, 314D comprises an edge which abuts against a corresponding peripheral edge of a corresponding additional magnetization segment 314F, 314G, 314H, 3141. For example, in the illustrated embodiment of Figure 4D, edge 314C-1 of peripheral magnetization segment 314C abuts against peripheral edge 314H-1 of additional magnetization segment 314H.
[0057] In the Figure 4D embodiment, each peripheral magnetization segment 314A, 314B, 314C, 314D has a corresponding peripheral magnetization direction which is opposite to the first magnetization direction of the central magnetization segment 314E and is generally orthogonal to the magnetization direction of the additional magnetization segments 314F, 314G, 314H, 3141. For example, in the Figure 3D embodiment, central magnetization segment 314E is magnetized in the positive stage-z direction (i.e. with its magnetic north pole facing out of the Figure 4D page), peripheral magnetization segments 314A, 314B, 314C, 314D are magnetized in the negative stage-z direction (i.e. with their magnetic south poles facing out of the Figure 4D page) and additional magnetization segments 314F, 314G, 314H, 3141 are magnetized in directions orthogonal to the stage-z direction (i.e. in the plane of the Figure 4D page) as shown by the arrows in additional magnetization segments 314F, 314G, 314H, 3141. In some embodiments, the magnetization directions of each of the magnetization segments 314 in the Figure 4D sub-array 321 could be reversed (i.e. have its magnetization direction changed by 180°). In some embodiments, a stage-x dimension (i.e. a length in a stage-x direction) of sub-array 321 may be set to be generally equal to a spatial period λχ and a stage-y dimension of sub-array 321 may be set to be generally equal to a spatial period λγ. These y spatial periods λχ, λγ may also be referred to as λ2, λ1 (i.e. λχ=λ2 and λγ=λι). The significance of spatial periods λχ, λγ is explained in more detail below. These spatial periods
λχ, λγ may be the same as the spatial periods of the current phases driven in coil traces 32, 34. In some embodiments, such as is illustrated in the Figure 4D embodiment, the stage-x and stage y-dimensions (e.g. λχ and λγ) of sub-array 321 are generally equal to one another. This is not necessary. In general, the stage-x and stage y-dimensions (e.g. λχ and λγ) of sub-array 321 may be different from one another. The stage-x and stage-y directions may be the principal directions of magnet array 312D. Principal directions are described in more detail below.
[0058] Referring back to Figure 4A, line AA is located in the stage-x/stage-y plane and intersects with a notional stage-z axis (not expressly shown) at the stage-x-stage-y plane geometric center of sub-array 21, magnet array 12 and/or magnet array assembly 16. Line AA is shown at an angle a with respect to the stage-x direction. When a notional single linear wire of infinite length and infinitesimal cross-section (not shown) is aligned with line AA and a constant current flows through this wire, the lateral force (i.e. the force generally orthogonal to the stage-z direction) on moveable stage 10 resulting from the interaction of the magnetic field of magnet array 12 and the magnetic field induced by the current in the notional coil trace will vary with the angle a. For the magnet arrays 12 of Figures 4A, 4B and 4D, the magnitude of this force will have maximum values at oc=0° (i.e. line AA is parallel to the stage-x axis) and oc=90° (i.e. line AA is parallel to the stage y-axis) and will have minimum values at oc=45°, and oc=135°. Based on these maxima of the force profile at oc=0° and oc=90°, the stage-x (oc=0°) and stage-y (oc=90°) directions may be referred to as the principal directions of the 2D magnet arrays shown in Figures 4A, 4B and 4D. For the magnet array 12 the magnitude of this force will have minimum values at approximately
[0059] For the 2D magnet arrays 12 of Figures 4A-4D, the peripheral edges of each magnet array 12 (and of each sub-array 21) are parallel with one of the principal (stage-x and stage-y directions) directions. More particularly, the peripheral edges of additional magnetization segments 214A, 214B, 214C and 214D of magnet array 12 (Figure 4A) and sub-arrays 221 (Figure 4B) are aligned with the principal directions (oc=0° and oc=90°) of magnet array 212 and sub-arrays 221. Similarly, the peripheral edges of peripheral magnetization segments 314A, 314B, 314C and 314D are aligned with the principal directions (oc=0° and oc=90°) of
magnet array 312 and sub-array 321. This feature of the 2D magnet arrays 12 (and sub-arrays 21 of Figures 4A-4D (i.e. sub-arrays having additional/peripheral magnetization segments with peripheral edges aligned with principal directions) may be referred to as principal- aligned outlines. This principal-aligned outlines feature allows efficient use of working region 36 and permits a displacement device to operate with a relatively large number of moveable stages 10 compared to displacement devices having moveable stages without principal-aligned outlines. In some embodiments, the central magnetization segments of the embodiments of Figures 4A-4D may be shaped to have principal direction dimensions x, y which are in a range of χ<λ2<2χ and y< i<2y. In some embodiments, the central
magnetization segments of the embodiments of Figures 4A-4D may be shaped to have principal direction dimensions x, y which are in a range of 0.5χ<λ2<3χ and 0.5y< j<3y.
[0060] Figure 4E is a schematic top view of a displacement device 50 comprising a pair of moveable stages 10 each having a magnet array 212A of the type shown in Figure 4A and a stator 30 comprising x-traces 32 and y-traces 34. The Figure 4E displacement device 50 can achieve maximum force or maximum efficiency, when each magnet array 212A has one of its principal axes (Xm, Ym) aligned with either the stator-x direction (Xs) or the stator-y direction (Ys). These are the preferred orientations of magnet arrays 212A (and the other 2D magnet arrays 12 of Figure 4A-4D) about the stage-z axis for each moveable stage 10, especially during relatively fast motion (e.g. for motion above 75% of the top speed of moveable stage(s) 10) and/or for relatively long distances of travel (e.g. for distances above 75% of a distance across working region 36). Therefore, given a minimum gap between two adjacent moveable stages 10, magnet arrays 12 with principal-aligned outlines can help maximize the utilization of working region 36 and thus increase moveable stage density per unit stator area in the Xs -Ys plane.
[0061] Another property shared by the 2D magnet arrays 12 (and sub-arrays 21) depicted in Figures 4A, 4B and 4D is 90° degree rotational symmetry (e.g. after a magnet array assembly 16 oe magnet array 12 rotates by 90° about a stage-z axis (centrally located with respect to the stage-x-stage-y dimensions of the corresponding magnet array assembly 16 or magnet array 12, as the case may be), it has the same magnetic configuration as it had before the rotation). This property can simplify the control procedures associated with the movement of moveable stage 10, by minimizing the possible number of orientations of each magnet array 12.
Otherwise, there will be two or more possible states for moveable stages 10 even when one of the principal axes (Xm, Ym) of their magnet arrays 12 is aligned with stator-x and/or stator-y directions.
ID Magnet Array Assemblies
[0062] A second general type of magnet array assembly that can be used with any of the displacement devices disclosed herein is referred to as a ID magnet array assembly 16. A ID magnet array assembly 16 comprises one or more magnet arrays 12 and each such magnet array 12 comprises plurality of linearly elongated magnetization segments 14 (e.g. elongated in a stage-x direction or a stage-y direction), with each magnetization segment 14 having a corresponding magnetization direction that is generally orthogonal to its elongation direction. At least two of the magnetization segments 14 in each magnet array 12 may have
magnetization directions that are different from one another.
[0063] In some embodiments, a moveable stage 10 comprise a first magnet array 12 comprising a plurality of linearly elongated first magnetization segments 14 (e.g. elongated in a stage-x direction), with each first magnetization segment 14 having a corresponding magnetization direction that is generally orthogonal to the stage-x direction. At least two of the first magnetization segments 14 may have magnetization directions that are different from one another. The first magnetization directions of the first magnetization segments 14 may exhibit a first spatial period λ1 over a stage-y direction width of the first magnet array 12. In some embodiments, the stage-y direction width of the first magnet array 12 is generally equal to λι, so that the first magnetization directions of the first magnetization segments 14 exhibit a single first spatial period λ1 over the stage-y direction width of the first magnet array 12. In some embodiments, the first magnetization directions of the first magnetization segments 14 exhibit multiple first spatial periods λ1 which repeat over the stage-y direction width of the first magnet array 12 such that the period of repetition is equal to the first spatial period λ1. In some embodiments, the stage-y direction width Wmy of the first magnet array is related to the first spatial period λ1 according to Wmy = a where a is a positive integer.
[0064] In some embodiments, a moveable stage 10 comprises two magnet arrays 12. Similar to the first magnet array 12, the second magnet array 13 may comprise a plurality of linearly elongated second magnetization segments 14. However, the second magnetization segments
14 may be linearly elongated in the stage-y direction (e.g. non-parallel to the stage-x direction or generally orthogonal to the stage-x direction). Each second magnetization segment 14 has a corresponding second magnetization direction that is generally orthogonal to the stage-y direction and at least two of the second magnetization segments 14 have second magnetization directions that are different from one another. The second magnetization directions of the second magnetization segments 14 may exhibit a second spatial period λ2 over a stage-x direction width of the second magnet array 12. In some embodiments, the stage-x direction width of the second magnet array 12 is generally equal to λ2, so that the second magnetization directions of the second magnetization segments 14 exhibit a single second spatial period λ2 over the stage-x direction width. In other embodiments, the second magnetization directions of the second magnetization segments 14 exhibit multiple second spatial periods λ2 which repeat over the stage-x direction width such that the period of repetition is equal to the second spatial period λ2. In some embodiments, the stage-x direction width of the second magnet array is related to the second spatial period λ2 according to Wmx = b where b is a positive integer. In some embodiments, the first spatial period λ1 is equal to the second spatial period λ2 and they may both be referred to as the spatial period λ.
[0065] In some embodiments, a moveable stage 10 comprises four magnet arrays 12. Similar to the first magnet array 12, the third magnet array 12 may comprise a plurality of third magnetization segments 14 linearly elongated in the stage-x direction, where each third magnetization segment 14 has a corresponding third magnetization direction that is generally orthogonal to the stage-x direction and at least two of the third magnetization segments 14 have third magnetization directions that are different from one another. Similar to the second magnet array 12, the fourth magnet array 12 may comprise a plurality of fourth magnetization segments 14 linearly elongated in the stage-y direction, where each fourth magnetization segment 14 has a corresponding fourth magnetization direction that is generally orthogonal to the stage-y direction and at least two of the fourth magnetization segments 14 have fourth magnetization directions that are different from one another. The third magnetization directions of the third magnetization segments 14 may exhibit the first spatial period λ1 (or a unique third spatial period λ3) over a stage-y direction width of the third magnet array 12. In some embodiments, the stage-y direction width of the third magnet array 12 is generally equal to λ1 (or λ3), so that the third magnetization directions of the third magnetization
segments 14 exhibit a single first spatial period λ1 (or single third spatial period λ3) over the stage-y direction width. In other embodiments, the third magnetization directions of the third magnetization segments 14 exhibit multiple first spatial periods λ1 (or multiple third spatial periods λ3) which repeat over the stage-y direction width such that the period of repetition is equal to the first spatial period λ1 (or third spatial period λ3). In some embodiments, the stage- y direction width Wmy of the third magnet array is related to the first spatial period λ1 according to Wmy = where a is a positive integer. The fourth magnetization directions of the fourth magnetization segments 14 may exhibit the second spatial period λ2 (or a unique fourth spatial period λ4) over a stage-x direction width of the fourth magnet array 12. In some embodiments, the stage-x direction width of the fourth magnet array 12 is generally equal to λ2 (or λ4), so that the fourth magnetization directions of the fourth magnetization segments 14 exhibit a single second spatial period λ2 (or singles spatial period λ ) over the stage-x direction width. In other embodiments, the fourth magnetization directions of the fourth magnetization segments 14 exhibit multiple second spatial periods λ2 (or multiple fourth spatial periods λ4) which repeat over the stage-x direction width such that the period of repetition is equal to the second spatial period λ2 (or fourth spatial period λ4). In some embodiments, the stage-x direction width of the fourth magnet array is related to the second spatial period λ2 according to Wmx = b where b is a positive integer. In some embodiments, the first spatial period λ1 is equal to the second spatial period λ2 and they may both be referred to as the spatial period λ.
[0066] Figures 5A and 5B respectively depict schematic top views of moveable stages 410A,
410B incorporating magnet array assemblies 416A, 416B comprising a plurality of ID magnet arrays 412 according to particular embodiments. In the illustrated embodiment, each of magnet array assemblies 416A, 416B comprise four ID magnet arrays 412A, 412B, 412C,
412D (collectively, magnet array assemblies 412) which include a first magnet array 412A comprising magnetization segments 414A elongated in the stage-x direction, second magnet array 412B comprising magnetization segments 414B elongated in the stage-y direction, third magnet array 412C comprising magnetization segments 414C elongated in the stage-x direction and fourth magnet array 412D comprising magnetization segments 414D elongated in the stage-y direction. Because of their elongation directions, first and third magnet arrays
412 A, 412C may be referred to as x- magnet arrays and their corresponding magnetization
segments 414A, 414C may be referred to herein as x-magnetization segments and second and fourth magnet arrays 412B, 412D may be referred to as y-magnet arrays and their corresponding magnetization segments 414B, 414D may be referred to herein as y- magnetization segments. Other than for their locations and/or orientations, any of magnet arrays 412 in any one of magnet array assemblies 416A, 416B and/or in any one of moveable stages 410A, 41 OB may be substantially similar to one another. In this way, magnet array assemblies 416A, 416B and moveable stages 410A, 410B may be 90° rotationally symmetric about a stage-z oriented axis located at the stage-x-stage-y center of magnet array assemblies 416A, 416B and moveable stages 410A, 410B.
[0067] Although their individual magnet arrays 412 may be similar to one another, magnet array assemblies 416A, 416B and moveable stages 410A, 410B of the Figure 4A and 4B embodiments have layouts which are similar to one another in some respects and differ from one another in other respects. In the case of both magnet array assemblies 416A, 416B, a stage-x oriented edge of first magnet array 412A abuts against a stage-x oriented edge of second magnet array 412B (at abutment 455A), a stage-y oriented edge of the first magnet array 412A abuts against a stage-y oriented edge of the fourth magnet array 412D (at abutment 455B), a stage-x oriented edge of third magnet array 412C abuts against a stage-x oriented edge of the fourth magnet array 412D (at abutment 455C), and a stage-y oriented edge of the third magnet array 412C abuts against a stage-y oriented edge of the second magnet array 412B (at abutment 455D). Further, in the case of both magnet array assemblies 416 A, 416B, the peripheral edges of magnet arrays 412 are aligned with one another to provide magnet array assemblies 416A, 416B with a generally rectangular peripheral shape. In particular, the stage-y oriented peripheral edges of first and second magnet arrays 412 A, 412B and the stage-y oriented peripheral edges of third and fourth magnet arrays 412C, 412D are aligned with one another in the stage-y direction. Further, the stage-x oriented peripheral edges of the first and fourth magnet arrays 412 A, 412D and the stage-x oriented peripheral edges of second and third magnet arrays 412B, 412C are aligned with one another in the stage-x direction.
[0068] In some embodiments, these abutments and/or peripheral edge alignments are not necessary and magnet array assemblies 16 may comprise as few as one ID magnet array 12 or a plurality of ID magnet arrays 412 which are spaced apart from one another (i.e. non-
abutting), which have non-aligned peripheral edges and/or which abut one another with different abutment and/or alignment relationships. For example, in some embodiments, the stage-y oriented peripheral edges of first and second magnet arrays 412 A, 412B and the stage-y oriented peripheral edges of third and fourth magnet arrays 412C, 412D are not aligned with one another in the stage-y direction; and in some embodiments, the stage-x oriented peripheral edges of the first and fourth magnet arrays 412 A, 412D and the stage-x oriented peripheral edges of second and third magnet arrays 412B, 412C are not aligned with one another in the stage-x direction.
[0069] The layout of magnet array assembly 416B differs from the layout of magnet array assembly 416A in that for magnet array assembly 416B, corresponding stage-y oriented edges 457A, 457C of first and third magnet arrays 412A, 412C are offset from one another in the stage-x direction (by an offset Ox) and adjacent stage-x oriented edges 459A, 459C of first and third magnet arrays 412A, 412C are spaced apart from one another in the stage-y direction (by a first space Sy) and corresponding stage-x oriented edges 457B, 457D of second and fourth magnet arrays 412B, 412D are offset from one another in the stage-y direction (by an offset Oy) and adjacent stage-y oriented edges 459B, 459D of second and fourth magnet arrays 412B, 412D are spaced apart from one another in the stage-x direction (by a second space Sx). It can be seen from Figure 5B, that for magnet array assembly 416B, the stage-x dimensions of the first and third magnet arrays 412A, 412C are larger than their corresponding stage-y dimensions, while the stage-y dimensions of the second and fourth magnet arrays 412B, 412D are larger than their corresponding stage-x dimensions. These offsets Ox, Oy and spaces Sx, Sy give rise to a non- magnetized space 451 in the center of magnet arrays assembly 416B. The layout of magnet array assembly 416B may be advantageous (relative to the layout of magnet array assembly 416 A) because active coil traces interacting closely with magnet array 412A may generate relatively little coupling force on the magnet array 412C, and vice versa in magnet array assembly 416B as compared to magnet array assembly 416A; and active coil traces interacting closely with magnet array 412B generates little coupling force on the magnet array 412D, and vice versa in magnet array assembly 416B as compared to magnet array assembly 416A.
[0070] The layout of magnet array assembly 416A differs from the layout of magnet array assembly 416B in that: the stage-x oriented edges of the first and second magnet arrays 412A,
412B (i.e. the stage-x oriented edges that provide abutment 455 A) have the same stage-x dimension; the stage-y-oriented edges of the first and fourth magnet arrays 412A, 412D (i.e. the stage-y oriented edges that provide abutment 455B) have the same stage-y dimension; the stage-x oriented edges of the third and fourth magnet arrays 412C, 412D (i.e. the stage-x oriented edges that provide abutment 455C) have the same stage-x dimension; and the stagey-oriented edges of the second and third magnet arrays 412B, 412C (i.e. the stage-y oriented edges that provide abutment 455D) have the same stage-y dimension. Further, with these dimensions (and the above-described abutment and peripheral edge alignment features) magnet array assembly 416A does not have a space that is analogous to space 451 of magnet array assembly 416B. The layout of magnet array assembly 416A may be advantageous (relative to the layout of magnet array 416B) because the magnet array assembly footprint (in the stage-x and stage-y directions) is fully utilized for magnetic field generation.
[0071] Another difference between magnet array assemblies 416A, 416B is that for magnet array assembly 416A, the magnet array 412A that is furthest in the positive stage-x direction and furthest in the positive stage-y direction comprises magnetization segments 414A which are elongated in the stage-x direction and the other magnet arrays 412B, 412C, 412D alternate between having magnetization segments 414B, 414C, 414D elongated in the stage-y and stage-x directions. In contrasts, for magnet array assembly 416B, the magnet array 412D that is furthest in the positive stage-x direction and furthest in the positive stage-y direction comprises magnetization segments 414D which are elongated in the stage-y direction and the other magnet arrays 412 A, 412B, 412C alternate between having magnetization segments 414A, 414B, 414C elongated in the stage-x and stage-y directions. In this description: magnet array assemblies, like magnet array assembly 416A of Figure 5 A, which have a magnet array that is furthest in the positive stage-x direction and furthest in the positive stage-y direction and which comprises magnetization segments which are elongated in the stage-x direction may be referred to as right-handed magnet array assemblies; and magnet array assemblies, like magnet array assembly 416B of Figure 5B, which have a magnet array that is furthest in the positive stage-x direction and furthest in the positive stage-y direction and which comprises magnetization segments which are elongated in the stage-y direction may be referred to as left-handed magnet array assemblies. It should be understood that many variations to magnet array assemblies 416 A, 416B can be used in moveable stages 410A,
410B. In one example, magnet array assembly 416A of Figure 5A can be changed from a right-handed to a left-handed variation. In another example, magnet array assembly 416B of Figure 5B can be changed from a left handed to a right handled variation.
[0072] As discussed above, other than for their orientations, the magnet arrays 412 in magnet array assemblies 416A, 416B and moveable stages 410A, 410B may be substantially similar to one another. However, the magnet arrays 412 in magnet array assemblies 416A, 416B may have a wide variety of patterns of magnetization segments 414 (and their corresponding magnetization directions). This disclosure describes a number of different embodiments of 1- D magnet arrays 412, each of which could be used for magnet arrays 412 in any of the 1-D magnet array assemblies described herein (e.g. magnet arrays assemblies 416A, 416B). For brevity and convenience, except where otherwise dictated by the context, this disclosure refers to each of these ID magnet arrays using reference number 412. Figure 5C is a cross- sectional view of an exemplary y-magnet array 412 (e.g. array 412B) which is used in Figure 5 A magnet array assembly 416A and which could be used for the Figure 5B magnet array assembly 416B or any of the other ID magnet array assemblies described herein. Figure 5D is a cross-sectional view of an exemplary y-magnet array 412 (e.g. array 412B) which is used in Figure 5B magnet array assembly 416B and which could be used for the Figure 5 A magnet array assembly 416A or any of the other ID magnet array assemblies described herein. In the illustrated cross-sectional views of Figures 5C and 5D, each magnet array 412 comprises a plurality of magnetization segments 414, each of which has a corresponding magnetization direction (where the magnetization directions of magnetization segments 414 are indicated by arrows). While the magnet arrays 412 of Figures 5C and 5D are y-magnet arrays, it will be appreciated that x-magnet arrays may be provided by merely altering the orientations of the illustrated magnet arrays and that the description of magnet arrays 412 described herein should be understood to apply to y-magnet arrays 412 or x-magnet arrays 412 with adjustment of orientation, as appropriate.
[0073] As can be seen from Figures 5A and 5B, magnet arrays 412 shown in Figures 5A and 5B exhibit a number of similar properties. The magnetization directions of magnetization segments 414 are orthogonal to the elongation directions of magnetization segments 414. At least two of magnetization segments 414 of each magnet array 412 are different from one another. In general, magnet arrays 412 may comprise magnetization segments 414 with any
suitable integer number Nt (Nt>2) of magnetization directions. In the illustrated embodiments of Figures 5C and 5D, Nt=4. The magnetization directions of magnetization segments 414 exhibit a spatial period λχ over the stage-x width of magnet arrays 412. To avoid complicating the illustrations of Figures 5C and 5D, the spatial periods λχ are shown as λ without loss of generality. In the Figure 5C embodiment, the stage-x direction width (Wmx) of magnet array 412 is generally equal to λχ, so that the magnetization directions of magnetization segments 414 exhibit a single spatial period λχ over the stage-x direction width of magnet array 412. In the Figure 5D embodiment, the magnetization directions of magnetization segments 414 exhibit two spatial periods λχ which repeat over the stage-x direction width ((Wmx=2 x) of magnet array 412. In general, the magnetization directions of first magnetization segments 214 may exhibit any positive integer number Nm spatial periods λχ which repeat over the stage-x direction width ((Wmx=Nm x) of magnet array 412. In the illustrated embodiments of Figures 5C and 5D, the magnetization directions of magnetization segments 414 are mirror symmetric relative to a plane of symmetry (extending in the stage-y and stage z-directions and passing through the stage-x direction center of magnet array 412 indicated by lines 441 shown in Figures 5C and 5D).
[0074] In the illustrated embodiments of Figures 5C and 5D, the stage-x direction widths of each magnetic segment 414 is generally equal to one of— or— . In the case of the Figure 5 A
4 8
and 5B embodiments, the edge magnetization segments 414' (i.e. magnetization segments 414' at the edges of arrays 412) have stage-x direction widths (— ) that are half of the stage-x
8
direction widths (— ) of the other (interior) magnetization segments 414. In some
embodiments, the stage-x direction widths of each magnetic segment 414 may be generally equal to one of ^ or ½ where N is any positive integer. In some embodiments, edge magnetization segments 414' may have stage-x direction widths that are half of the stage-x direction widths ) of the other (interior) magnetization segments 414. In some embodiments, N=Nt (i.e. the number of different magnetization directions), as is the case in the illustrated embodiments of Figures 5C and 5D. In the illustrated embodiments of Figures 5C and 5D, the edge magnetization segments 414' have magnetization directions that are oriented in the stage-z direction (in the positive stage-z direction in the case of the illustrated
embodiments). For any of the embodiments of magnet arrays 412 shown and/or described herein, the stage-z directions of the magnetization segments 414 may be inverted from those shown and/or described herein.
[0075] The characteristics of the embodiments of Figures 5A-5J allow these magnet array assemblies 416 to be 90° rotationally symmetric about a stage-z oriented axis located at a stage-x-stage-y center of these magnet array assemblies 416. These characteristics include: in the cross-sectional (or split cross-sectional) view of two magnet arrays 412 having magnetization segments 414 elongated in the same directions, the patterns of the
magnetization directions of the magnetization segments 414 are mirror-symmetric about a middle plane extending in the stage-z direction and in direction of elongation of these magnetization segments 414 and coinciding with a stage-x-stage-y center of the magnet array assembly 416. For example, in magnet array assemblies 416E, 416F of Figures 5A and 5B, two magnet arrays 412D and 412B are elongated in the stage-y direction; in the split cross- sectional view along the line Y-Y, the magnetization patterns of magnet arrays 412B, 412D are mirror symmetric about a middle plane extending in the stage-y-stage-z directions and coinciding with a stage-x-stage-y center of the magnet array assembly 416.
[0076] Magnet arrays 412 of Figures 5C, 5D represent examples of magnet arrays 412 which may be used to implement magnet arrays 412 of magnet array assemblies 416A, 416B of Figures 5A, 5B or any of the other ID magnet array assemblies described herein. Figures 6A- 6T are cross-sectional views of exemplary y-magnet arrays 412 which may be used in magnet array assemblies 416A, 416B of Figures 5A, 5B or any of the other ID magnet array assemblies described herein. In the illustrated cross-sectional views of Figures 6A-6T, each magnet array 412 comprises a plurality of magnetization segments 414, each of which has a corresponding magnetization direction (where the magnetization directions of magnetization segments 414 are indicated by arrows). The magnetization directions of magnetization segments 414 of the magnet arrays exhibit a spatial period λχ over the stage-x width of magnet arrays 412. To avoid complicating the illustrations of Figures 6A-6T, the spatial periods λχ are shown as λ without loss of generality. While the magnet arrays 412 of Figures 6A-6T are y-magnet arrays, it will be appreciated that x- magnet arrays may be provided by merely altering the orientations of the illustrated magnet arrays and that the description of magnet arrays 412 described herein should be understood to apply to y-magnet arrays 412 or
x-magnet arrays 412 with adjustment of orientation, as appropriate.
[0077] For the sake of brevity, only the differences between the magnet arrays 412 of Figures 6A-6T (relative to magnet arrays 412 of Figures 5C and 5D, described above) are described in detail here. Figure 6A shows a magnet array 412 according to an example embodiment that is substantially similar to magnet array 412 shown in Figure 5D. Figure 6B shows a magnet array 412 according to an example embodiment that is substantially similar to magnet array 412 shown in Figure 5C. Figures 6C and 6D show particular embodiments of magnet arrays 412 which differ from magnet arrays 412 of Figures 5C and 5D in that: magnet arrays 412 of Figures 6C and 6D have magnetization directions which are anti-symmetric about their central planes 441 extending in the stage-x-stage-z directions and passing through their stage- z-dimension centers; and have stage-x widths Wmx given generally by Wmx=(Nm-0.5)Ax where Nm is a positive integer and λχ is the spatial periodicity. It can be observed that Nm=l for the embodiment of Figure 6C and Nm=2 for the embodiment of Figure 6D. In the Figure 6C embodiment, the total number of magnetization directions Ni=3 and in the Figure 6D embodiment, the total number of magnetization directions Nt=4. Any of the magnet array embodiments of Figures 6A-6D can be used to create a magnet array assembly 16 that is 90° rotationally symmetric about its central stage-z axis. By way of non-limiting example, the magnet array 412 shown in Figure 6C can be used to make the right handed magnet array assembly 416 shown in Figure 5A, by putting the Figure 6C magnet array 412 at the location of magnet array 412B in the Figure 5 A array assembly 416 and by putting a magnet array similar to the Figure 6C magnet array, but with the magnetization directions of each of its magnetization segments 414 inverted by 180° at the location of magnet array 412D in the Figure 5A array assembly 416. As another non-limiting example, the magnet array 412 shown in Figure 6D can be used to make the right handed magnet array assembly 416 shown in Figure 5 A, by putting the Figure 6D magnet array 412 at the location of magnet array 412B in the Figure 5A array assembly 416 and by putting a magnet array similar to the Figure 6D magnet array, but with the magnetization directions of each of its magnetization segments 414 inverted by 180° at the location of magnet array 412D in the Figure 5A array assembly 416.
[0078] In the embodiments of Figures 6E-6T, magnet arrays 412 have stage-x widths Wmx given generally by Wmx = Nn x (where Nm is a positive integer and λχ is the spatial
periodicity). It can be observed that: Nm=l for the embodiments of Figures 6E, 61, 6M, 6Q; Nm=2 for the embodiments of Figures 6F, 6J, 6Ν, 6R; Nm=3 for the embodiments of Figures 6G, 6K, 60, 6S; and Nm=4 for the embodiments of Figures 6H, 6L, 6P, 6T. In the case of the embodiments of Figures 6E and 6Q, the total number of magnetization directions Ni=3; in the case of the embodiments of Figures 61, 6M, 6Ν, 60, 6P, the total number of magnetization directions Nt=2; and, in the case of the embodiments of Figures 6F, 6G, 6H, 6J, 6K, 6L, 6R, 6S, 6T, the total number of magnetization directions Nt= . In the embodiments of Figure 6E- 6H, the edge magnetization segments 414' have magnetization directions that are generally oriented in the same stage-x directions (where Nm is an even integer (Figures 6F, 6H)) and in opposing stage-x directions (where Nm is an odd integer (Figures 6E, 6G)). Further, in the embodiments of Figures 6E-6H, edge magnetization segments 414' of magnet arrays 412 have stage-x direction widths (e.g. ^ where N is a positive integer) that are half that (e.g. of interior magnetization segments 414. In the embodiments of Figures 6I-6L, the edge magnetization segments 414' are of the same stage-x direction width (e.g. ½ where N is a positive integer) as the interior magnetization segments 414 and comprise one edge magnetization segment 414' that is oriented along the stage-z direction (positive stage-z or negative stage-z) and one edge magnetization segment 414' that is oriented along the stage-x direction (positive stage-x or negative stage-x).
[0079] In the embodiments of Figures 6M-6P, the total number of magnetization directions Nt=2 and these two magnetization directions are in the positive stage-z direction and the negative stage-z direction, so that edge magnetization segments414' have magnetization directions that are either in the positive or negative stage-z direction. Further, edge magnetization segments 414' of the embodiments of 6M-6P have stage-x direction widths
(e.g. where N is a positive integer) that are half that (e.g. of interior magnetization segments 414. The embodiments of Figure 6M-6P are either mirror symmetric about a stage- y-stage-z oriented central plane 441 (where Nm is an even integer (Figures 6Ν, 6P)) or mirror anti-symmetric about a stage-y-stage-z oriented central plane 441 (where Nm is an odd integer (Figures 6M, 60)). Like the embodiments of Figures 6A-6D, the characteristics of the embodiments of Figures 6M-6P allow these magnet arrays 412 to be used to construct magnet array assemblies 416 that are 90° rotationally symmetric about a stage-z oriented axis located
at a stage-x-stage-y center of the magnet array assemblies 416. These characteristics include: (i) either mirror symmetry or mirror anti-symmetry about stage-z-y plane 441 ; (ii) stage-x directions widths Wmx = Nn x (where Nm is a positive integer and λχ is the spatial periodicity); and (iii) edge magnetization segments 414' have stage-x direction widths (^, where N is a positive integer) that are half of the stage-x direction widths of the other
(interior) magnetization segments 414. It should be noted that suitable magnet arrays 412 may comprise one or more of these 90° rotationally symmetric characteristics, but need not have all of them.
[0080] In the embodiments of Figures 6Q-6T, the total number of magnetization directions N,=3 (Figure 6Q) or N,=4 (Figures 6R-6T) and these magnetization directions are in the positive and negative stage-z directions and the positive and negative stage-x directions. In the embodiments of Figure 6Q-6T, the edge magnetization segments 414' have magnetization directions that are generally oriented in the same (e.g. positive) stage-z directions (where Nm is an even integer (Figures 6R, 6T)) and in opposing stage-z directions (where Nm is an odd integer (Figures 6Q, 6S)). Further, edge magnetization segments 414' of the embodiments of
6Q-6T have stage-x direction widths (e.g. ^ where N is a positive integer) that are half that
(e.g. of interior magnetization segments 414. The embodiments of Figure 6Q-6T are either mirror symmetric about central plane 441 (where Nm is an even integer (Figures 6R, 6T) or mirror anti-symmetric about central plane 441 (where Nm is an odd integer (Figures 6Q, 6S)). Like the embodiments of Figures 6A-6D, the characteristics of the embodiments of Figures 6M-6P allow these magnet arrays 412 to be used to construct magnet array assemblies 416 that are 90° rotationally symmetric about a stage-z oriented axis located at a stage-x-stage-y center of the magnet array assemblies 416. These characteristics include: (i) either mirror symmetry or mirror anti-symmetry about stage-z-y plane 441 ; (ii) stage-x directions widths Wmx = Nm^ x (where Nm is a positive integer and λχ is the spatial periodicity); and (iii) edge magnetization segments 414' have stage-x direction widths (^, where N is a positive integer) that are half of the stage-x direction widths (½) of the other
(interior) magnetization segments 414. It should be noted that a suitable magnet array 412 may comprise one or more of these 90° rotationally symmetric characteristics, but need not
have all of them.
[0081] It will be appreciated from the discussion above, that there are a large number of possible embodiments of magnet arrays 412 which may be used in the magnet array assemblies 416A, 416B of Figure 5A, 5B or any of the other ID magnet array assemblies described herein, with potential adjustments to the individual magnet arrays 412 of such magnet array assemblies 416. It will be appreciated that the exemplary embodiments described in Figures 6A-6T are exemplary and non-limiting in nature and that magnet arrays 412 may be provided with other features not explicitly described herein. For example, in some embodiments, magnet arrays 412 could comprise different parameters W^, N, Nm, Nt and/or Nz. As another example, in some embodiments, magnet arrays 412 could comprise centralized non-magnetic spacers like those described in PCT publication No.
WO2013/059934.
Bumpers
[0082] Referring back to Figure 3, moveable stage 110 of displacement device 150 comprises optional bumpers 117 which may protect moveable stage 110 from other moveable stages and other objects that may be introduced onto stator 30 or into working region 36. Bumpers 117 may be made of non-magnetic materials to protect moveable stage 110 and its magnet array assembly 116. Further bumpers 117 may prevent two or more moveable stages 110 from getting too close to one another (e.g. to a vicinity where their respective magnetization segments might attract one another and might overcome the forces caused by current controllably driven into coil traces 34). Bumpers 117 may also serve to prevent other objects with high magnetic permeability from getting too close to magnet array assembly 116. For example, in the absence of non-magnetic bumpers 117, an iron or steel washer/screw/nuts dropped onto working region 36 can be attached to magnet array assembly 116 and cause system failure.
[0083] Figure 7 shows a top cross-sectional view of the Figure 3 moveable stage 110 according to a particular embodiment showing non-magnetic bumpers 117. Bumper 117 comprises four bumper elements 117A, 117B, 117C, 117D abutting respective peripheral edges of magnet array assembly 116. The lateral width WB of a bumper element 117A, 117B, 117C, 117D may be defined to be the narrower one of its stage-x or stage-y dimension. The
lateral width WB of each bumper element 117A, 117B, 117C, 117D is preferably between Ο.ΐλ and 0.75λ, where λ is the magnet spatial period and it is assumed, for the exemplary embodiment of Figure 7, that λχ=λγ=λ. In some embodiments, this lateral width WB is set at 0.2λ~1λ. In some embodiments, this lateral width WB is set at 0.3λ~0.5λ. In some embodiments, this lateral width WB is set to be generally equal to 0.4λ. In some
embodiments, this lateral width WB is set to be generally equal to 0.45λ.
Back Iron
[0084] Referring back to Figure 3, in some embodiments, stage support structure 20 may be fabricated from highly magnetically permeable material (e.g. with relative magnetic permeability greater than 100), such as iron, ferrite, cobalt, combinations of these materials and/or the like. High magnetic permeability helps enhance the magnetic field below (e.g. in the negative stator-z direction relative to) magnet array assembly 16, which is where the coil traces of stator 30 are located during operation. Figures 11 A and 1 IB respectively depict cross-sectional views of the same magnet array assembly 16 supported by a non-magnetic stage support structure 20A and an iron-based stage support structure 20B. Stage support structure 20B of the Figure 11B embodiment is iron-based, but other magnetically permeable materials could be used to provide this stage support structure 20B (as discussed above). When provided in stage support structures 20, such magnetically permeable materials may be referred to herein as back iron. It can be seen from Figures 11 A and 1 IB, that the magnetic field in the case where support structure 20B comprises back iron (Figure 1 IB) is relatively strong below (e.g. in the negative stator-z direction relative to) magnet array assembly 16 when compared to the case where support structure 20A does not include back iron. A stronger magnetic field generated by the permanent magnets in magnet array assembly 16 can help increase the force on moveable stage 10 under the same coil trace current conditions.
[0085] In some embodiments, it may be beneficial to use a stage support structure 20A without back iron. Such embodiments may be desirable to minimize the weight of moveable stage 10, for example. Such stage support structures 20A can be fabricated from aluminum, ceramic, carbon-fiber reinforced composite materials, combinations of these materials and/or the like. Reducing the weight of stage support layer 20A may help to minimize moveable stage inertia.
Stator coil assembly
[0086] Various embodiments and additional detail of stator 30 are now provided. Referring back to Figure 1 described above, stator 30 comprises a stator coil assembly 35 which comprises at least the traces of a plurality of electrically conductive coils 31. Coils 31 are shaped to provide first and second pluralities of coil traces32, 34 which are respectively elongated in non-parallel directions. In particular embodiments, such as depicted in Figure 1 A, the first plurality of coil traces 32 is orthogonal to the second plurality of coil traces 34. In particular embodiments, such as depicted in Figure 1 A, first plurality of coil traces 32 is distributed over at least a portion of a first layer 40 and generally elongated in a stator-x direction; and second plurality of coil traces 34 is distributed over at least a portion of a second layer 42 and generally elongated in a stator-y direction. In some embodiments, such as depicted in Figure 1A, the first and second layers 40, 42 over which first and second pluralities of coil traces 32, 34 are respectively distributed may be located at different (e.g. first and second) stator-z locations, although this is not necessary and, in some embodiments, first and second layers 40, 42 may be provided in different excitation regions (described in more detail below), but at the same stator-z location.
[0087] In some embodiments, stator 30 may comprise additional pluralities of coil traces which may be distributed over portions of additional layers at corresponding additional stator-z direction locations. For example, stator 30 may comprise a first additional plurality of coil traces (not shown) distributed over at least a portion of a first additional layer at a corresponding first additional stator-z location and generally elongated in a stator-x direction; and a second additional plurality of coil traces (not shown) distributed over at least a portion of a second additional layer at a corresponding second additional stator-z location and generally elongated in a stator-y direction. Additional pluralities of coil traces are not limited to being elongated in the stator-x or stator-y directions. In some embodiments, additional pluralities of coil traces are provided which are generally elongated in angular directions between the stator-x and stator-y directions. For example, in some embodiments, stator 30 may comprise one or both of: a first additional angular plurality of coil traces (not shown) distributed over at least a portion of a first additional angular layer at a corresponding first additional angular stator-z location and generally elongated in a direction split between the
positive stator-x and positive stator-y directions (e.g. at 45° counter-clockwise around a stator-z axis from the positive stator-x direction in some embodiments); and a second additional angular plurality of coil traces (not shown) distributed over at least a portion of a second additional angular layer at a corresponding second additional angular stator-z location and generally elongated in a direction split between the negative stator-x and positive stator-y directions (e.g. at 45° clockwise around a stator-z axis from the negative stator-x direction in some embodiments).
[0088] In some embodiments, coil traces 32, 34 in layers 40, 42 at different stator-z locations may overlap one another in the stator-z direction. The two dimensional space over which coil traces 32, 34 overlap one another in the stator-z direction may define a working region 36 over which moveable stage 10 is moveable relative to stator 30. In some embodiments, coil traces 32, 34 in each corresponding layer 40, 42 may be distributed throughout their respective layers 40, 42, so that coil traces 32, 34 and/or layers 40, 42 may overlap in the stator-z direction at all locations in working region 36. This is not necessary. In some embodiments, coil traces 32, 34 may occupy particular excitation regions (described in more detail below) that occupy less than an entirety of a corresponding layer 40, 42. Some of coil traces 32, 34 may be connected at their ends to form a two-phase, three-phase, or multiple- phase winding configuration as described in more detail below. While working region 36 is a two-dimensional space, this description may describe working region 36 as a feature of stator 30, for convenience.
[0089] Figure 3 shows another embodiment of a displacement device 150 which comprises a stator 130 according to a particular embodiment. Stator 130 of the Figure 3 embodiment comprises a stator bearing layer 145, stator coil assembly 135, coil supporting layer 137, power electronics layer 138, and cooling layer 139. Stator coil assembly 135 may comprise the aforementioned coils 31 and/or coil traces 32, 34.
[0090] Stator bearing layer 145 may overlap with stator coil assembly 135 in stator-z direction over the stator- x/stator-y span of working region 36 (not shown in Figure 3). In the illustrated embodiment, stator bearing layer 145 comprises a generally planar stator bearing surface 126 which may be parallel and adjacent to (and may bear against) generally planar stage bearing surface 124 of moveable stage 110 during operation. In the illustrated embodiment, stage bearing surface 124 faces the negative stator-z direction and stator bearing
surface 126 faces the positive stator-z direction. Bearing layers 118, 145 may support moveable stage 10 in the stator-z direction, may constrain moveable stage 10 rotation about stator-x and stator-y oriented axes, may minimize friction forces in lateral (stator-x and stator-y) directions, and may minimize friction torque around axes oriented in the stator-z direction. Bearing layers 118, 145 may be fabricated from materials with a low coefficient of sliding friction. For example, in some embodiments, the coefficient of sliding friction (the ratio of the stator-x or stator-y direction friction force over their normal (stator-z direction) contact force) between bearing layers 118, 145 and their respective bearing surfaces 124, 126 is less than 0.2. In some embodiments, this coefficient of sliding friction is less than 0.15 and in some embodiments this coefficient of sliding friction is less than 0.06. In some
embodiments, one of stage bearing layer 118 and stator bearing layer 145 is fabricated from PTFE (Polytetrafluoroethylene) or PTFE doped materials, and the other of stage bearing layer 118 and stator bearing layer 145 is fabricated from metal-based material, such as stainless steel. Such combination of bearing materials results in their coefficient of friction as low as 0.04. In some embodiments, both bearing layers 118, 145 are made of PTFE or PTFE doped plastic material. Bearing layers 118, 145 may be provided in the shape of film, sheet, pad, a thin layer of coating and/or the like.
[0091] In some embodiments, stage bearing layer 118 may comprise a very flat bearing surface 124 which may be provided using manufacturing processes such as grinding, polishing and/or the like and stator bearing layer 145 may comprise or provide a restrictor layer which may be used to create an air bearing between stage bearing layer 118 and stator bearing layer 145. Such a restrictor layer may be fabricated from porous material with a large number of small holes. Non-limiting examples of materials which may be used to fabricate a restrictor layer include porous carbon, porous bronze, porous steel and/or the like. In some embodiments, a restrictor layer may comprise a hard solid material with small holes (e.g. created by a laser drilling process) that may be used to guide high pressure air. The diameter of the pores or holes in such restrictor layers may range between less than 100 nm to a few hundreds of microns, for example.
[0092] Figure 12 depicts a stator bearing layer 545 which comprises a restrictor layer 553. Stator bearing layer 545 may be used to provide an air bearing between the stator 30 and moveable stage 10 of any of the displacement devices 50 described herein. Stator bearing
layer 545 comprises multiple sub-layers, which define a plurality of air distribution chambers 554 and holes 555. The stator coil assembly 535 may be located between air distribution chambers 554 and a spacing layer 557. Holes 555 through stator coil assembly 535 may be provided by PCB vias, for example. High pressure air may be supplied to air chambers 554 via a suitably configured conduit 556. The high pressure air is forced out of chambers 554 via holes 555 and impinges on restrictor layer 553. As discussed above, restrictor layer 553 is porous and air flowing through its pores can create an air bearing above (in the positive stator-z direction relative to) stator bearing layer 545. As shown in the Figure 12
embodiment, stator bearing layer 545 may optionally comprise a spacing layer 557 between holes 555 and restrictor layer 553. Spacing layer 557 may provide through holes with cross- sectional areas that are larger than holes 555 for directing air from holes 555 to restrictor layer 553.
[0093] Coil supporting layer 137 may provide mechanical support to stator coil assembly 135.
Stator coil assembly 135 of the Figure 3 embodiment may be substantially similar to stator coil assembly 35 of the Figure 1 embodiment and may comprise coils 31 shaped to provide coil traces 32, 34 (and any additional coil traces) having features similar to those of the Figure 1 embodiment. Controller 60 may be connected to deliver control signals to one or more amplifiers 70 and controller 60 may be configured to use those signals to control the currents driven by amplifier(s) 70 into at least some of first coil traces 32 and at least some of second coil traces 34 to thereby cause moveable stage 10 to track a desired position within working region 36 - e.g. a desired position, (xr,yr), within working region 36, where xr is a desired position of moveable stage 10 in the stator-x direction and yr is a desired position of moveable stage 10 in the stator-y direction.
[0094] When in operation, moveable stage bearing surface 124 is in close proximity with (e.g. adjacent to) and generally parallel to stator bearing surface 126. The stator-z direction gap between moveable stage 110 and stator 130 is less than 10mm, and is typically less than lmm. In some embodiments, stage bearing surface 124 of moveable stage 110 is always in contact and bears against stator bearing surface 126 of stator 30. In some embodiments, the magnetic forces generated by the interaction of currents driven into coil traces 32, 34 and magnet array(s) 12 of moveable stage 30 may be controlled (e.g. by controller 60), such that
moveable stage 110 is attracted toward stator 30 whenever the currents are being controllably driven into coil traces 32, 34.
[0095] Figure 8A shows a schematic top view of a stator coil assembly 35 according to a particular embodiment which may be used in displacement device 50 (Figure 1),
displacement device 150 (Figure 3) or any of the other displacement devices described herein. Stator coil assembly 35, as depicted, comprises a plurality of excitation regions 43 A- 431 (collectively, excitation regions 43). In some embodiments, each of excitation regions 43 is rectangular in shape. In some embodiments, excitation regions 43 may have other shapes (e.g. triangular, hexagonal and/or the like). Each location in each of excitation regions 43 may overlap corresponding coil trace layers 40, 42 at different stator-z locations and corresponding coil traces 32, 34 (and any additional layers and additional coil traces) in the stator-z direction. Coil traces 32, 34 that overlap a particular one of excitation regions 43 in the stator-z direction may be said to be coil traces 32, 34 in, of, associated with or corresponding to the particular one of excitation regions 43. Each coil trace 32, 34 in each excitation region 43 can be excited with a controllable current, where such current may be controlled by controller 60 which may use control signals to control amplifier(s) 70 which in turn drive current into coil traces 32, 34. Each of excitation regions 43 may be connected to a corresponding amplifier module, which may be located in power electronics layer 138 (see Figure 3) or may be spatially separated from stator 30 and connected to coil traces 32, 34 in its excitation region 43 using suitable electrical connections. Currents driven into the coil traces 32, 34 in each excitation region 43 can be independently controlled. In some embodiments, two or more excitation regions 43 may share a common amplifier by connecting their corresponding coil traces in parallel or serially. It is not necessary that a particular stator coil assembly 35 comprise a plurality of excitation regions. In some embodiments, it is sufficient for a stator coil assembly 35 to have a single excitation region that spans the entire working region.
[0096] Figure 8B shows a schematic top view of a single layer 40 of the Figure 8A stator coil assembly 35 according to a particular embodiment, where the individually controllable coil traces 32 corresponding to each excitation region 43 have the same orientation in the illustrated layer 40. In the case of the example layer 40 illustrated in Figure 8B, layer 40 comprises individually controllable coil traces 32 which are elongated in the stator-x
direction corresponding to each excitation region 43. In such embodiments, the Figure 8 A stator coil assembly 35 may also comprise another layer 42 (not expressly shown) at another stator-z location wherein the other layer 42 comprises individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to each excitation region 43. It will be appreciated from the discussion herein that the Figure 8A stator assembly could comprise additional layers similar to layers 40, 42 described above.
[0097] Figure 8C shows a schematic top view of a single layer 40 of the Figure 8A stator coil assembly 35 according to another particular embodiment, where the individually controllable coil traces 32, 34 corresponding to each excitation region 43 have different orientations. In the case of the example layer 40 illustrated in Figure 8B, layer 40 comprises individually controllable coil traces 32 which are elongated in the stator-x direction corresponding to excitation regions 43A, 43C, 43E, 43G, 431 and layer 40 comprises individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to excitation regions 43B, 43D, 43F and 43H. In some such embodiments, the Figure 8A stator coil assembly 35 may also comprise another layer 42 (not expressly shown) at another stator-z location wherein the orientations of the coil traces 32, 34 in each excitation region 43 are reversed. For example, in in another layer 42, layer 42 may comprise individually controllable coil traces 34 which are elongated in the stator-y direction corresponding to excitation regions 43A, 43C, 43E, 43G, 431 and layer 42 may comprise individually controllable coil traces 32 which are elongated in the stator-x direction corresponding to excitation regions 43B, 43D, 43F and 43H. It will be appreciated from the discussion herein that the Figure 8A stator assembly could comprise additional layers similar to layers 40, 42 described above. In some embodiments, the Figure 8A stator assembly could comprise combinations of layers of the type described with reference to Figure 8B and layers of the type described with reference to Figure 8C.
[0098] Figures 9A-9D each show schematic depictions of portions of coil traces in one corresponding excitation region 43. Figure 9 A is a cross-sectional view (along a stator- x/stator-z plane) of one excitation region 43 of stator coil assembly 35 comprising a plurality of coil trace layers 40 A, 40B, 42 A, 42B (collectively, coil trace layers, 40, 42). In the Figure 9A embodiment, each coil trace layer 40, 42 is separated from adjacent coil trace layers 42, 40 by an insulation layer 47. Insulation layer 47 prevents electrical conduction between coil
trace layers 40, 42. Each coil trace layer 40, 42 extends in the stator-x and stator-y directions with its normal direction generally parallel to the stator-z direction. As discussed above, each coil trace layer 40, 42 comprises a plurality of coil traces which may be distributed over at least a portion of the layer and which extend in a particular stator direction (e.g. in the stator- x direction or the stator-y direction).
[0099] Figure 9B is a schematic cross-sectional view (along a stator-x/stator-y plane) of a first coil trace layer 40A according to a particular embodiment. Coil trace layer 40B may have characteristics similar to coil trace layer 40A. Coil trace layer 40A of the Figure 9B embodiment comprises a plurality of coil traces 32A, 32B, 32C, 32A', 32B', 32C
(collectively, coil traces 32), with each coil trace 32 linearly elongated in the stator-x direction. Due to their elongation in the stator-x direction, coil traces 32 may be referred to herein as x-traces 32 and coil trace layer 40 A may be referred to as an x-trace layer 40 or an x-layer 40. Figure 9C is a schematic cross-sectional view (along a stator-x/stator-y plane) of a second coil trace layer 42A according to a particular embodiment. Coil trace layer 42B may have characteristics similar to coil trace layer 42A. Coil trace layer 42A of the Figure 9C embodiment comprises a plurality of coil traces 34A, 34B, 34C, 34A', 34B', 34C
(collectively, coil traces 34), with each coil trace 34 linearly elongated in the stator-y direction. Due to their elongation in the stator-y direction, coil traces 34 may be referred to herein as y-traces 34 and coil trace layer 42A may be referred to as an y-trace layer 42 or a y- layer 42.
[0100] As can be seen from Figures 9B and 9C, each x-trace 32 has a stator-y direction width Wax and adjacent pairs of x-traces 32 are spatially offset by a stator-y direction spatial pitch Pcx and each y-trace 34 has a stator-x direction width of Wcy and adjacent pairs of y-traces 34 are spatially offset by a stator-x direction spatial pitch Pcy. In some embodiments, the stator-y λ
direction spatial pitch Pcx of x-traces 32 may be generally equal to Pcx =— 2rip =— 2rip , where λι=λγ is a first spatial period in a stage-y direction (as explained in more detail below) and np is an effective number of phases in the first currents (as explained in more detail below). In some embodiments, the stator-x direction spatial pitch Pcy of y-traces 34 may be generally equal to Pcv =—— =
y 2mv 2mv where λ2=λχ is a second spatial period in a stage-x direction (as explained in more detail below) and mp is an effective number of phases in the second
currents (as explained in more detail below). For example, a trace pitch of x-traces 32 in the
X λ
stator-y direction could be Pcx =— =— =— (corresponding to three effective phases (e.g.
np=3)). A three-phase amplifier with 6 transistors (e.g. MOSFET, or IGBT or BJT) could then be used to drive the x-traces 32 in layer 40A. In some embodiments, the stator-y direction spatial pitch Pcx of x-traces 32 may be generally equal to Pcx = = where P and Q are arbitrary positive integers. In some embodiments, the stator-x direction spatial pitch Pcy of y-traces 34 may be generally equal to Pcy = ^ = where R and S are arbitrary positive integers.
[0101] As shown in Figure 9B and 9C, the trace widths Wcx and Wcy are each less than the respective trace pitches Pcx and Pcy to avoid electric conduction between two adjacent traces. In some embodiments, these differences (Pcx-Wcx and PCy-WCy) may be relatively small (e.g. on the order of 100-400 microns in some embodiments) and may depend on the thickness of corresponding traces 32, 34 in the stator-z direction). It should be noted that there may be a plurality of x-trace layers 40 and y-trace layers 42 in one excitation region (as is the case, for example, in the embodiment of Figure 9A), and these trace layers 40, 42 may be located at different stator-z locations. X-traces 32 in different x-trace layers 40 of one excitation region 43 may be connected in parallel or be connected in serial or be each independently driven with different power amplifier channels. Similarly, y-traces 34 in different y-trace layers 42 of one excitation region 43 may be connected in parallel or be connected in serial or be each independently driven with different power amplifier channels.
[0102] Figure 9D shows an embodiment of coil trace layer 49 having coil traces 33 A, 33B, 33C, 33A', 33B', 33C (collectively, coil traces 33). Each trace 33 of the Figure 9D coil trace layer 49 is linearly elongated along a stator direction XE, which is oriented at an angle a relative to the stator-x direction. Due to its elongation direction at an angle a relative to the stator-x axis, coil traces 33 in the Figure 7D coil trace layer 49 may be referred to as a-traces
33 and coil trace layer 49 may be referred to as an a-trace layer 49. Typical values of angle a in some embodiments are 45° and 135°, although other angles may be used. The trace pitch and trace width of traces 33 in a-layer 49 may have features similar to those of coil traces 32,
34 of Figures 9B and 9C. It will be appreciated that a-layer 49 and a-traces 33 are optional and not necessary.
[0103] In general, current driven through the coil traces 32, 33, 34 is used to propel moveable stage 10 to a desired position. In particular, current driven in x- traces 32 may be used to propel moveable stage 10 along a stator-y direction to track a desired stator-y position yr; current driven in y-coil traces 34 may be used to propel moveable stage 10 along a stator-x direction to track a desired stator-x position xr; and current driven in oc-traces 33 may be used to rotate moveable stage 10 around a stator-z oriented axis, as explained below.
[0104] It will be appreciated that the number of coil traces 32, 34, 33 in layers 40, 42, 49 need not be limited to the exemplary six traces shown in Figures 9B, 9C, 9D. In some embodiments, coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction may comprise coil traces 32, 34, 33 that are non-parallel with respect to one another. In some embodiments, coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction may comprise coil traces that are orthogonally oriented with respect to one another. It will be appreciated that the number of coil trace layers 40, 42, 49 in stator 30 need not be limited to the four traces shown in the illustrative embodiment of Figure 9A. In general, stator 30 may comprise any suitable number of coil trace layers 40, 42, 49. Further, it is not a requirement that the orientations of coil traces 32, 34, 33 in coil trace layers 40, 42, 49 adjacent to one another in the stator-z direction be different from one another.
[0105] One excitation region 43 may comprise one or a plurality of x-trace layers 40 and one or a plurality of y-trace layers 42. In some embodiments, it may be desired that one excitation region 43 comprises one or a plurality of x-trace layers 40, one or a plurality of y-trace layers 42, and one or a plurality of oc-trace layers 49. Coil trace layers 40, 42, 49 (and their respective coils 32, 34, 33) in one excitation region 43 may overlap with each other in the stator-z direction throughout the excitation region 43. Generally, one coil excitation region 43 may comprise one or more oci-coil trace layers, one or more oc2-trace layers, one or more 0C3- trace layers ... one or more ocrtrace layers, where t is any positive integer, oci, oc2 ... (¾ are greater than or equal to 0° and less than 180°, but not equal to each other.
[0106] Figure 10 is a schematic depiction of an excitation region 43 which forms part of a working region 36 associated with a stator coil assembly 35 according to an example embodiment. In excitation region 43, stator coil assembly 35 comprises an x-trace layer 40 comprising x-traces 32, a y-trace layer 42 comprising y-traces 34, an oci-trace layer 49A comprising oci-traces 33 A and an oc2-trace layer 49B comprising oc2-traces 33B. In the
illustrated embodiment of Figure 10, 0Ci is generally equal to 45° and (¾ is generally equal to 135°. It should be noted that in the depictions of Figures 9 and 10, only partial traces are shown for illustrative convenience and it should be understood that coil traces 32, 34, 33 in each coil trace layer 40, 42, 49 may be distributed throughout at least a portion of their corresponding excitation region 43 and may extend (in their corresponding extension direction) across at least a portion of their corresponding excitation region 43. Coil traces in coil-trace layers 40, 42, 49 of an excitation region 43 may be electrically connected at their ends to form multiple -phase (e.g. two phase, three phase or more) winding configurations.
[0107] Referring back to the illustrated embodiment of Figure 3, stator 130 comprises a coil support layer 137 for supporting coil assembly 135 and a power electronics layer 138. Power electronics layer 138 may comprise one or more amplifier(s) 70 connected by suitable electrical connections (not shown) to the coil traces of coil assembly 135 to provide excitation currents to the coil traces. In some embodiments, it is not necessary that amplifier(s) 70 be located in power electronics layer 138 and amplifier(s) 70 may be located in any suitable location which can facilitate the electrical connection of amplifier(s) 70 to the coil traces in coil trace assembly 135. This configuration is shown in dashed lines in Figure 3. Stator 130 and/or displacement device 150 may comprise a signal interface (and
corresponding electrical connections) between amplifier(s) 70 and controller 60 to facilitate control of amplifiers 70 by controller 60. Such a signal interface between controller 60 and amplifiers 70 may comprise any suitable form of signal interface, such as a real-time network interface, fieldbus and/or the like. In one example embodiment, this interface between controller 60 and amplifier(s) 70 comprises an EtherCAT interface.
[0108] Coil support layer 137 may be fabricated using highly magnetically permeable material (e.g. with relative magnetic permeability greater than 100), such as iron, ferrite, cobalt combinations of these materials and/or the like. Fabricating coil support layer 137 using magnetically permeable materials may help to increase the magnetic flux density at stator coil traces 32, 33, 34 and may thereby enhance the lateral (stator-x and stator-y) direction interaction forces associated with the interaction of the magnetic fields generated by stator 30 and by moveable stage 10. In some embodiments, coil support layer 137 may be fabricated using non-conductive materials to minimize eddy currents induced by motion of moveable stages. Non-limiting examples of non-conductive materials include plastics,
ceramics, mineral-based materials, composite materials and/or the like. In some
embodiments, coil support layer 137 may be fabricated using materials with low magnetic permeability, such as aluminum, ceramics, plastic, and/or the like.
[0109] Heat can be generated in displacement device 150. Such heat can come from a number of sources which may include: the currents driven into the traces of stator coil assembly 135, friction between stage bearing layer 118 and stator bearing layer 145, eddy currents in stator 30 induced by motion of moveable stage 110, electronic
devices/components inside power electronics layer 138 and/or the like. To accommodate such heat, in some embodiments, stator 130 comprises a cooling layer 139. Cooling layer 139 may comprise one or more cooling devices. Non- limiting examples of cooling devices include fans, surface area increasing heat sinks to allow air flow to carry heat away from stator 30, fluid-based cooling devices which may comprise cooling channels through which fluid coolant may flow and/or the like.
[0110] Stator 30 and coil assembly 35 may be fabricated using one or more printed-circuit boards (PCBs). PCBs can be manufactured using standard PCB fabrication, flat-panel display lithography, lithography and/or similar technology known in the art to provide coils 31 and coil traces 32, 34, 33 in their respective layers 40, 42, 49. Insulator layers 47 may comprise FR4 core, prepreg, ceramic material and/or the like and may be fabricated or otherwise inserted between coil layers 40, 42, 49. One or more coil layers 40, 42, 49 may be stacked together (i.e. adjacent to one another in the stator-z direction) in a single PCB board. In some embodiments, coil traces 32, 34, 33 generally elongated in the same direction (e.g. at different coil trace layers 40, 42, 49) may be connected in parallel or serially, depending on via design and/or electrical connection techniques for the ends of coil traces 32, 33, 34. In some embodiments, coil traces 32, 33, 34 generally elongated in the same direction (e.g. at different coil trace layers 40, 42, 49) are not electrically connected to one another.
[0111] Coil traces 32, 34, 33 fabricated using PCB technology can accommodate sufficient current for controlling the motion of moveable stage 10. By way of non-limiting example, each coil trace 32, 34, 33 can be fabricated from 6 oz copper (about 200-220 μπι thick) or more. As discussed above, in the portions of coil trace layers 40, 42, 49 that overlap with working region 36 may comprise coil traces 32, 34, 33 which are shaped in the form of flattened strips. Coil traces 32, 34, 33 having such flattened strip shapes may provide good
thermal conductivity. The inventors have confirmed (via testing) that laminated copper can carry a sustained current density of 10 A/mm with a 50°C temperature rise above ambient without using an active heat sink. Another advantage of planar layers 40, 42, 49 of coil traces 32, 34, 33 is that the naturally stratified conductors that provide coil traces 32, 34, 33 make them ideally suitable for carrying AC current, because the self-generated alternating magnetic field can easily penetrate the conductor through top and bottom (stator-z direction facing) surfaces but generates only relatively low self-induced eddy currents.
[0112] Multiple PCBs may be aligned side by side (e.g. in one or both of the stator-x and stator-y directions) to provide the desired stator-x and stator-y dimensions for working region 36. Board-to-board lateral connections (in the stator-x and/or stator-y directions) may be made at the edges by connecting pads, through-holes of edge-adjacent boards, copper wires and/or using other suitable bridging components of the like for electrically connecting conductors on adjacent PCB boards. In some embodiments, such bridging components may be located underneath the PCB boards (e.g. on the stator-z side opposite moveable stage 10); in some embodiments, such bridging components may be additionally or alternatively located above the PCB boards (e.g. on the same stator-z side as moveable stage 10) or on the side(s) of the PCB boards. When PCBs are connected adjacent to one another in the stator-x and/or stator-y directions, the end terminals (not shown) of coils 32, 33, 34 may be located at or near the perimeter of stator 30 for ease of wiring to amplifier(s) 70. Connecting PCBs to one another in this manner allows displacement device 50 to be easily extended in both stator-x and stator-y dimensions for various applications. In some embodiments, coil traces 32, 34, 33 on stator x-y adjacent PCB boards may be serially connected to one another to reduce the number of amplifier(s) 70 for driving current through coil traces 32, 33, 34. In some embodiments, coil traces 32, 33, 34 on any particular PCB board may be driven by one or more independent amplifier(s) 70 - e.g. coils 32, 33, 34 on one PCB board may be driven by amplifier(s) 70 that are different from amplifier(s) 70 which drive coils 32, 33, 34 on a stator x-y adjacent PCB board. Using independent amplifier(s) in this manner may increase the flexibility for multi-stage actuation and to reduce heat generation.
[0113] A single PCB board may be fabricated to have a thickness (in the stator-Z direction) of up to 5 mm (or more) using available PCB technology. When thicker boards are desired (e.g. for heavy-duty applications), multiple PCBs can be stacked together in the stator-Z
direction. Another benefit of using PCB technology to fabricate coil assembly 35 is the possibility of deploying large numbers of low-profile sensors (such as Hall-effect position sensor, capacitive position sensors and/or the like) directly on the board.
Motion Control
[0114] Figure 13A shows a schematic block diagram of a control system 58 suitable for use in controlling any of the displacement devices 50 described herein according to a particular embodiment. Although they may be described as different embodiments, except where otherwise specifically note, control system 58 and any of the control techniques,
embodiments and methods described in the remainder of this description may be used with any of the displacement devices 50 described herein. Control system 58 of the Figure 13A embodiment comprises controller 60, one or more amplifier(s) 70 and stator coil assembly 35. Controller 60 may comprise any suitably programmed controller capable of implementing control system 58. Such a controller 60 (and components thereof) may comprise hardware, software, firmware or any combination thereof. For example, such a controller 60 may be implemented on a programmed computer system comprising one or more processors, user input apparatus, displays and/or the like. Such a controller 60 may be implemented as an embedded system with a suitable user interface comprising one or more processors, user input apparatus, displays and/or the like. Processors may comprise microprocessors, digital signal processors, graphics processors, field programmable gate arrays, and/or the like. Components of controller 60 may be combined or subdivided, and components of controller 60 may comprise sub-components shared with other components of controller 60.
Components of controller 60, may be physically remote from one another.
[0115] Controller 60 may be configured to control one or more amplifiers 70 (illustrated, in Figure 13 A, as power amplifier 70) to drive currents into the plurality of coil traces in coil trace assembly 35 and to thereby controllably move moveable stage 10 relative to stator 30. In some embodiments, the currents in the plurality of coil traces create magnetic fields which interact with the magnetic fields of the magnet array assembly on moveable stage 10 and cause corresponding forces on moveable stage 10. The currents may be controlled by controller 60 such that these magnetic forces on moveable stage 10 may attract moveable stage 10 toward stator 30 (e.g. in the negative stator-z direction in the case of the illustrated
embodiments) at all times when controller 60 is controlling the currents driven by the one or more amplifiers 70.
[0116] In the illustrated embodiment, controller 60 is shown as comprising a trajectory generator 62 which generates desired or reference positions for each moveable stage 10. Such reference positions may include a desired or reference stator-x position xr of moveable stage 10, a desired or reference stator-y position yr of moveable stage and, optionally, a desired rotational orientation rzr of moveable stage 10 about a stage-z oriented axis (e.g. a stage-z oriented axis through the stage-x/stage-y center of moveables stage 10). The reference positions (xr,yr,rzr) generated by trajectory genereator 62 are typically based on user requirements, application requirements and/or the present actual location of moveable stage(s) 10. In the illustrated embodiment, controller 60 also comprises a current command generator 64. Typically, although not necessarily, the desired position (xr,yr,rzr) of moveable stage 10 will vary over time, such that each of the reference positions xr,yr,rzr is a function of time and may be described herein as xr(t),yr(t),rzr(t) at a particular time, t. The evolutions of the desired positions (xr,yr Zr) over time may be referred to as a desired or reference trajectory. Generally, each moveable stage 10 has a unique reference trajectory. For brevity, except where otherwise dictated by the context, this description will focus on the trajectory and corresponding control of one moveable stage 10, it being understood that trajectories and control of other moveable stages 10 may be similarly implemented.
[0117] Current command generator 64 receives the desired positions xr, yr, rzr from trajectory generator 62 and creates corresponding current control signals ir which are provided to amplifier(s) 70. It will be appreciated that current control signals ir may comprise a plurality of control signals. In response to these current control signals ir, amplifier(s) 70 drive currents ix, iy into at least some of the coil traces of stator coil assembly 35. In some embodiments, first currents ix may be driven into a first plurality of coil traces and second currents iy may be driven into a second plurality of coil traces. In some embodiments, ix represents the currents driven into stator-x oriented coil traces 32 and iy represents the currents driven into stator-y oriented coil traces 34. Accordingly, the currents ix may be referred to herein as x-currents and the currents iy may be referred to herein as y-currents. As discussed above, stator coil assembly may also comprise a-oriented coil traces 33 and amplifier(s) 70 may additionally or alternatively drive currents ia into these traces 33. However, except where otherwise dictated
by the context, discussion of drive currents ia is omitted for brevity from the description of motion control.
[0118] Figure 13B schematically depicts one possible connection scheme to connect a plurality of y-coil traces 34 in one coil trace layer 42 within an excitation region 43 according to a particular embodiment. It will be appreciated that x- traces 32 in layer 40 may have characteristics analogous to those of y-traces 34 in layer 42. While traces 34 shown in Figure 13B are generally elongated in the stator-y direction, there may be some terminal connections near the edges of one excitation region 43 which connect different traces 34 together. Trace terminating connections sometimes extend through one or more other layer (e.g. another layer in the stator-z direction), as shown by the dashed lines in Figure 13B. The illustrated embodiment of Figure 13B depicts a three-phase effective current embodiment where y- currents comprise three different current phases ijy (j=0,l,2), each of which flows along a first trace 34A, 34B, 34C in a first direction and returns along a second trace 34A', 34B', 34C in an opposite, direction (e.g. current y flows in one direction along coil trace 34A and flows in the opposite direction along coil trace 34A').
[0119] As the current phases ijy return in the opposite direction, they effectively provide opposite waveforms, as compared to when they flow in the first direction. As discussed further below, the waveforms of current phases ijy may be spatially periodic as a function of xr with spatial periods λχ (also referred to herein as λ2) in the stator-x direction. In such cases, the opposite waveforms of current phases ijy flowing in opposite directions are out of spatial phase with one another by half the spatial period ( = y). In the Figure 13B embodiment, the current phases ijy which are driven into adjacent traces 34 (e.g. into traces 34A and 34B) may be controlled to have waveforms which have spatial phase differences of = The spatial period λχ= λ2 of the current phases ijy may be same spatial period described elsewhere herein in connection with the spatially periodic characteristics of magnet arrays 12 and/or coil traces 34. For example, in the Figure 13B embodiment, the stator-x direction pitch Pcy of stator-y oriented traces 34 is also configured to be a function of the spatial period λχ= λ2. In particular, the stator-x direction pitch Pcy of traces 34 in the Figure 13B embodiment is generally given by PCy = ~f = ~~·
[0120] In the Figure 13B embodiment, the currents iy may be described as comprising three
effective current phases, because the currents iy include three current phases ijy flowing in the first direction and then returning in the opposing direction at phases that are out of spatial phase with one another by half the spatial period ( = ). For example, in Figure 13B embodiment, the current in trace 34A has the same amplitude as the current in trace 34A', but is flowing in an opposite direction; therefore, the currents in traces 34A, 34A' are not independent and are considered as one effective current phase. In general, the currents iy are multi-phase currents comprising a plurality mp of current phases ijy (j=0,l,...,mp-\), where mp is an integer greater than one. Similarly, the currents ix are multi-phase currents comprising a plurality np of current phases ikx (k=0,l,...,np-\), where np is an integer greater than one. The currents ix may be referred to as first currents ix and their corresponding current phases ikx may be referred to as first current phases ikx. The currents iy may be referred to as second currents iy and their corresponding current phases ijy may be referred to as second current phases ijy. In some embodiments, the first currents ix comprise a plurality of first current phases, ikx, where k is an integer from 0 to np-l representing a first phase index. In some cases, the first phase index k may be represented as a letter, where the letter represents an integer from 0 to np-l (e.g. A may represent 0, B may represent 1 , C may represent 2, etc.). The first current phases ikx may each be driven into a corresponding one of a first plurality of stage-x oriented coil traces (e.g. coil traces 32A, 32B, 32C, etc.) and may return along another corresponding one of the stage-x oriented coil traces (e.g. coil traces 32A', 32B', 32C, etc.). Phase-adjacent first current phases ikx are driven into spatially adjacent ones of at least some of the first plurality of stator-x oriented coil traces 32. As a function of yr, each first current phase ikx in a particular one of the first plurality of coil traces is out of phase with one or more phase-adjacent first current phases in one or more spatially adjacent ones of the first plurality of coil traces 32 by a first spatial phase difference of— =— . Such
2 TT-jj 2 TT-jj
embodiments may be described has having np effective first current phases ikx.
[0121] Similarly, in some embodiments, the second currents iy comprise a plurality of second current phases, ijy, where j is an integer from 0 to mp-l representing a second phase index, where mp is the effective number of second current phases. In some cases, the second phase index j may be represented as a letter, where the letter represents an integer from 0 to mp-l (e.g. A may represent 0, B may represent 1, C may represent 2, etc.). The second current
phases ijy may each be driven into a corresponding one of a second plurality of stage-y oriented coil traces (e.g. coil traces 34A, 34B, 34C, etc.) and may return along another corresponding one of the stage-y oriented coil traces (e.g. coil traces 34A', 34B', 34C, etc.). Phase- adjacent second current phases ijy are driven into spatially adjacent ones of at least some of the second plurality of stator-y oriented coil traces 34. As a function of yr, each second current phase ijy in a particular one of the second plurality of coil traces is out of phase with one or more phase-adjacent second current phases in one or more spatially adjacent ones of the second plurality of coil traces 34 by a second spatial phase difference of -^2- =
[0122] Figures 13C and 13D respectively schematically depict an x-trace layout in a first layer 40 and a y-trace layout in a second layer 42 of an exemplary excitation region 43 according to a particular embodiment. Excitation region 43 of the illustrated embodiment of Figures 13C, 13D has a stator-x dimension of 2 χ and a stator-y dimensions of 2Ay. In the illustrated embodiment of Figures 13C, 13D,
although this is not necessary. In some embodiments, an excitation region 43 may have a stator-x dimension of Νχλχ and a stator-y dimension of Ny y, where Nx and Ny can be arbitrary positive integer numbers and λχ may be, but need not be, the same as y. Stator x-trace layer 40 of the Figure 13C embodiment comprises twelve x-traces 32 with a stator-y direction pitch Pcx of λγ/6. X-traces 32 are excited with three (np=3) effective current phases x, ijx, i2%. In some embodiments, these twelve x-traces can be driven by one three-phase amplifier; in some embodiments, these twelve x-traces can be driven by two three-phase amplifiers, for example, with each group of six adjacent x-traces independently driven by one three phase amplifier. Stator y-trace layer 42 of the Figure 13D embodiment comprises twelve y-traces 34 with a stator-x direction pitch PCy of λχ/6. Y-traces 34 are excited with three (ηιρ=3) effective current phases ioy, iiy, i2y In some embodiments, these twelve y-traces can be driven by one three-phase amplifier; in some embodiments, these twelve y-traces can be driven by two three-phase amplifiers, for example, with each group of six adjacent y traces independently driven by one three phase amplifier. Within excitation region 43, the x-traces 32 of layer 40 (Figure 13B) and the y- traces 34 of layer 42 may overlap one another in the stator-z direction.
[0123] Figures 13E and 13F show a pair of stator-z direction configurations for coil layers 40, 42 according to a pair of exemplary embodiments. Figure 13E depicts four trace layers
alternating between x-trace layers 40A, 40B and y-trace layers 42A, 42B. Figure 13F depicts four trace layers in which two x-trace layers 40A, 40B are adjacent one another in the stator-z direction and two y-trace layers 42 A, 42B are adjacent one another in the stator-z direction. In some embodiments, x-trace layers 40 and y-trace layers 42 may be layered in any pattern and any number of x-trace layers 40 and y-trace layers 42 may be provided. It should be noted that different excitation regions 43 may be independently driven or share common multiple phase currents.
[0124] Referring back to Figure 13 A, in currently preferred embodiments, first and second coil trace currents ΐχ> iy &re generated based on reference trajectory information (xr,yr,rzr) by control system 58. In some embodiments, control system 58 may generate first and second coil trace currents ix, iy based on reference trajectory information (xr,yr,rzr) and position feedback signals related to the current position of moveable stages 10. In some
embodiments, control system 58 may generate first and second coil trace currents ix, iy based on reference trajectory information (xr,yr,rzr) without using real-time position feedback signals related to the current position of moveable stages 10. The first and second coil trace currents ix, iy may create corresponding traveling magnetic field waves which are locked with corresponding ones of reference trajectories yr, xr. In this disclosure and the accompanying claims, when a current, current trace and/or corresponding magnetic field is described as traveling with a reference variable (e.g. with a reference trajectory or reference variable xr, yr), it should be understood to mean that such current, current trace and/or magnetic field varies spatially as the reference variables vary over time (e.g. as reference trajectory variables xr, yr vary over time). For example, in the case of three effective phases for both first currents ix and second currents iy (i.e. np=mp=3), current command generator 64 may use reference trajectory information (xr,yr,rzr) to generate three effective control signals ioxr, iixr, hxr for the first current phases hx and three effective control signals ioyr, iiyr, hyr for the second current phases ijy. These control signals (referred to generally as control signals ir) may then be used to cause amplifier(s) 70 to generate the first and second current phases x, ijx, and y, ijy, i2y (referred to generally as current phases ijy). It will be appreciated that control signals ixr, iyr may have functional forms similar to first and second current phases hx, ijy or, in some embodiments, may have digitally encoded formats which otherwise specify the functional forms of first and second current phases hx, ijy. Accordingly, unless the context dictates
otherwise, control signals ixr, iyr may be referred to herein interchangeably with first and second current phases hx, ijy.
[0125] In some embodiments, each first current phase ¾ is determined based on a function F(yr), where yr is the desired position of a moveable stage 10 in the stator-y direction in a working region 36. The function F(yr) may be a spatially periodic function of yr in the stator- y direction. The function, F(yr) may have the first spatial period
in the stator-y direction. The function, F(yr), may vary periodically with yr, such that, at least over a portion of working region 36, F(yr=y0) is equal to F(yr=y0+X ), where y0 is an arbitrary position of the moveable stage 10 in the stator-y direction. In some embodiments, the arbitrary position o is in a first interior portion of working region 36 (i.e. more than a stator-y distance λ1 from the stator-x oriented edges of working region 36). F(yr) may be a sinusoidal function of yr although F(yr) may be another periodic function of yr.
[0126] Figure 13G shows a number of first control signals ixr (i.e. control signals ixr used to generate first current phases ix which are driven into a first set of (e.g. stator-x oriented) coil traces) according to a particular embodiment where the function F(yr) is a sinusoidally periodic function of yr and the number of effective phases np=3. Figure 13G shows the three waveforms of the control signals i0xr, iixr, xr as a function of yr. It can be seen that the waveforms for the control signals xr, iixr, hxr are periodic functions of yr with a spatial period of
is the first magnetic spatial period in the stator-y direction, as discussed above. It should be noted that to avoid obscuring the drawing, Figure 13G refers to without loss of generality. Control signals xr, iixr, hxr are fed to amplifier(s) 70 and result in a corresponding current phases kx, ijx, hx, where each of current phases x, ijx, hx is driven into a spatially adjacent one of the first (e.g. stator-x oriented) coil traces. Because current phases x, ijx, hx are driven into x-coil traces 32, they may be referred to as first current phases x, ijx, hx or x-current phases. As indicated by Figure 13G, for the case where the number of phases np=3, the spatial phase shift between spatially adjacent x-current phases kx, Ux, hx (and corresponding control signals ioxr, iixr, hxr) is— 2 =— 2 =— 6 , which may also be equal to the stator-y oriented pitch Pcx of x-coil traces 32. For the Figure 13G illustrated embodiment, F(yr) is a sinusoidally periodic function of yr and, the waveforms of the control signals ioxr, iixr, hxr can be analytically represented as:
ioxr = Α0χ5ίη( 2π + ψχ) (la)
where Akx is the amplitude of the k phase control signal waveform in an excitation region and ψχ is an arbitrary offset. For the case where the control signals ioxr, iixr, hxr are sinusoidally periodic, a full spatial period is equivalent to 2π radians in electrical phase angle (where the electrical phase angle Θ is related to a spatial distance d2 in a second direction
2nd2
(stator y direction) by Θ = ■) and, consequently, the phase difference between phase- λ1
adjacent ones of control signals ioxr, iixr, i2Xr can be described as— =— in electrical phase angle with units of radians, which is evident from equation (1) above and is equivalent to a spatial phase shift of — . In some embodiments, the amplitude Atx is equal for all of the
6
control signals ijxr and can be referred to as Ax, X-current phases x, ijx, driven into at least some of the first (e.g. stator-x oriented) coil traces 32 may be amplified versions of control signals xr, ijxr, hxr and may have the same functional form as control signals xr, ijxr, hxr- In some cases the amplitudes of the x-current phases x, ijx, i2% may be different than those of the control signals i0xr, iixr, i2Xr-
[0127] The x-current phases x, ijx, may be connected to be driven into x- traces traces 32 in a manner similar to the connection of the current phases to the stator-y oriented traces shown in Figure 13B, for example. In some embodiments, x-current phases x, ijx, i2% may be driven into several spatially adjacent (e.g. in the stator-y direction) sets of x-traces 32. In some embodiments, x-current phases x, ijx, i2% may be driven into all of the x-traces 32 in this manner. In some embodiments, x-current phases x, ijx, i2% may be driven into at least some of x-traces 32. It will be appreciated from Figure 13G that these x-current phases x, ijx, i2x will generate a stator-y direction traveling magnet field wave. This traveling magnetic field wave will move with reference trajectory signal yr. At a particular yr, the magnetic fields created by the x-current phases x, ijx, i2% will interact with the magnetic fields associated with the magnet array assembly 16 of moveable stage 10, to create a potential energy profile
(e.g. a well) which has a local minimum when stage 10 is located at the stator-y location yr, thereby trapping moveable stage 10 at the desired stator-y location yr. When yr changes (i.e. it is desired to move moveable stage 10 to a new stator-y location), the resulting magnetic field generated by x-current phases x, ijx, i2% in x-traces 32 moves with yr and so does the minimum potential energy location (the minimum potential energy location may also be referred to as the bottom of a potential energy well or potential well). As discussed in more detail below, similar y-current phases ijy can be generated in stator-y oriented coil traces 34 to control the location of moveable stage 10 to a desired location (xr,yr)- [0128] Generally, the multi-phase current phases hx are not limited to three effective phases. As discussed above, the number of effective phases np for x-current phases hx may be any integer greater than one. In such cases, the corresponding current phases can be sinusoidally periodic functions of yr and can have a functional form
where k is a phase index that varies from 0 to np-\ , Akx is the amplitude of the k current phase waveform and ψχ is an arbitrary offset. It can be seen from equation (2) that in such embodiments, the phase shift between adjacent current phases hx takes the general form
-^- = (spatial phase) or (in electrical angle with units of radians). Phase-adjacent ones
V
of current phases * can be driven into spatially adjacent x-traces 32, such that the phase difference between the current p ^hases driven into sp ratially J ad Jiacent x-traces 32 is— 2np =— 2np
(spatial phase) or— (in electrical angle with units of radians). In such embodiments, x-traces np
32 in stator 30 can be designed to have a stator-y oriented coil trace pitch PrY =— =— .
[0129] Figure 14A shows a partial schematic illustration of a np -phase coil layout in an x- trace layer 40 of an excitation region 43, with stator-x direction width of Νχλχ, and a stator-y direction width of Ny y according to a particular embodiment. It can be seen from Figure
14A that phase-adjacent ones of current phases hx may be driven into spatially adjacent x- traces 32 and this pattern can be repeated for several spatially adjacent (e.g. in the stator-y direction) sets of x-traces 32. In some embodiments, spatially adjacent sets of x-traces (2np traces) can be driven with the same current phases hx. In some embodiments, each set of x- traces (2np traces) in one excitation region 43 can be independently driven with current
phases ¾ to allow the control of multiple moveable stages 10 independently. Figure 14B shows the current waveforms x, ijx as a function of desired stator-y location yr for moveable stage 10 for the case where Aia=Ax is the same for current phases x. Figure 14B shows the spatial phase difference— =— for spatially adjacent current phases kx. While current
2rip 2rip
phases kx may generally have any waveform that is a spatially periodic function of yr, sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution. Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like.
[0130] Current phases ijy driven into at least some of y-traces 34 to control the stator-x position of moveable stage 10 to track a desired xr position may be similarly generated. In some embodiments, each second current phase ijy is determined based on a function G(xr), where xr is the desired position of a moveable stage 10 in the stator-x direction in a working region 36. The function G(xr) may be a spatially periodic function of xr in the stator-x direction. The function, G(xr) may have the second spatial period
in the stator-x direction. The function, G(xr), may vary periodically with xr, such that, at least over a portion of working region 36, G(xr=x0) is equal to 0(χ =χ0+^2), where x0 is an arbitrary position of the moveable stage 10 in the stator-x direction. In some embodiments, the arbitrary position Xo is in a second interior portion of working region 36 (i.e. more than a stator-x distance λ2 from the stator-y oriented edges of working region 36). G(xr) may be a sinusoidal function of xr although G(xr) may be another type of periodic function of xr.
[0131] The waveforms for the control signals z, and the corresponding current phases ijy driven into y-traces 34 may be periodic signals of xr with a spatial period of
where is the second magnet spatial period in the stator-x direction, as discussed above.
Control signals z,y are fed to amplifier(s) 70 and result in a corresponding current phases ijy, where each of current phases ijy is driven into a spatially adjacent one of the second (e.g. stator-y oriented) coil traces. Because current phases ijy are driven into y-coil traces 34, they may be referred to as second current phases ijy or y-current phases. The spatial phase shift between spatially adjacent y-current phases ijy (and corresponding control signals z,y) is
-^2- = -^K which may also be equal to the stator-x oriented coil trace pitch Pcy of y-traces
2 2
34. For the case where G(xr) is a sinusoidally periodic function of xr and three effective phases (i.e. mp=3), the waveforms of the control signals z, can be analytically represented as:
io r = A0ysin( 2π + <py) (3a) yr = Alysin( 2n - ' + <py) (3b)
2π
hyr = A2ysin{-T- 2n -— + <py) (3c) where Ajy is the amplitude of the /* phase control signal waveform in an excitation region and (py is an arbitrary offset. For the case where the control signals ioyr, iiyr, hyr are sinusoidally periodic, a full spatial period is equivalent to 2π radians in electrical phase angle (where the electrical phase angle Θ is related to a spatial distance d-ι in a first direction
(stator-x direction) by θ = -ίΞί-ΐ) consequently, the phase difference between phase- adjacent ones of control signals ioyr, iiyr, hyr is given by -^- =— in the electrical angle
2
domain, which is evident from equation (3) above. In some embodiments, the amplitude Ajy is equal for all of the control signals z,y and can be referred to as Ay, Y-current phases ky, ijy, hy driven into at least some of the second (e.g. stator-y oriented) coil traces 34 may be amplified versions of control signals ioyr, hyr, hyr and may have the same functional form as control signals ioyr, hyr, hyr- In some cases the amplitudes of the y-current phases ky, ijy, hy may be different than those of the control signals kyr, hyr, hyr-
[0132] For the general case, where the number of effective phases mp for y-current phases ijy may be any integer greater than one. In such cases, the corresponding current phases can be sinusoidally periodic functions of xr and can have a functional form
ijy = Ajy sin (¾ 27r - ; ^ + <py) (4) where j is a phase index that varies from 0 to mp-\ , Ajy is the amplitude of the /* current phase waveform and (py is an arbitrary offset. It can be seen from equation (4) that in such embodiments, the phase shift between adjacent current phases ijy takes the general form —2- = -^- (spatial phase) or— (in electrical angle with units of radians). Phase-adjacent ones of current phases ijy can be driven into spatially adjacent y-traces 34, such that the phase
difference between the current phases driven into spatially adjacent y-traces 34 is—— =—^- (spatial phase) or— (in electrical angle with units of radians). In such embodiments, y-traces
nip
34 in stator 30 can be designed to have a stator-x oriented coil trace pitch Pcv = -^2- = -^2-.
[0133] The y-current phases ijy may be connected to be driven into y-traces traces 34 in a manner similar to that shown in Figure 13B, for example. In some embodiments, y-current phases ijy may be driven into several spatially adjacent (e.g. in the stator-x direction) sets of y-traces 34. In some embodiments, y-current phases ijy may be driven into all of the y-traces 34 in this manner. In some embodiments, y-current phases ijy may be driven into at least some of y-traces 34. In some embodiments, spatially adjacent sets of y-traces (2mp traces) can be driven with the same current phases ijy. In some embodiments, each set of y-traces
(2mptraces) in one excitation region 43 can be independently driven with current phases ijy to allow the control of multiple moveable stages 10 independently. These y-current phases ijy will generate a stator-x direction traveling magnet field wave. This traveling wave will move with reference trajectory signal xr. At a particular xr, the magnetic fields created by the y- current phases ijy will interact with the magnetic fields associated with the magnet array assembly 16 of moveable stage 10, to create a potential energy profile (e.g. a well) which has a local minimum when stage 10 is located at the stator-x location xr, thereby trapping moveable stage 10 at the desired stator-x location xr. When xr changes (i.e. it is desired to move moveable stage 10 to a new stator-x location), the resulting magnetic field generated by y-current phases ijy in y-traces 34 moves with xr and so does the minimum potential energy location.
[0134] In some embodiments, the spatially periodic functions Fp(yr) and Gp(xr) are angularly periodic functions with first and second angular periods equal to 2π (e.g. sinusoidal functions) such that, as a function of yr, each x-current phase, in a particular one of x- traces 32 is out of phase with one or more adjacent x-current phases hx in one or more spatially adjacent ones of x-traces 32 by a first electrical angular phase difference 2πΙηρ and, as a function of xr, each second current phase, ¾, in a particular one of the y-traces 34 is out of phase with one or more adjacent y-current phases ijy in one or more spatially adjacent y- traces 34 by a second electrical angular phase difference 2n/mp.
[0135] In some embodiments, the x-current phases and y-current phases ijy are driven into
corresponding coil traces 32, 34 over at least a portion of the working region 36. For example, in some embodiments, the x- and y-current phases ijy are driven into
corresponding traces that span an excitation region 43. This is not necessary, however, in some embodiments, the x- and y-current phases ¾ are driven into corresponding traces 32, 34 over a portion of an excitation region 43 or over more than one excitation region 43. In some embodiments, the x- and y-current phases ijy are driven into as few as two x-traces 32 and two y-traces 34.
[0136] It will be appreciated that the motion control techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
Trajectory Acceleration Compensation
[0137] The amplitudes Akx of x-current phases hx (e.g. from equations (1) and (2)) controls the strength or magnitude of the magnetic field corresponding to the kth x-current phase ¾ driven into its corresponding x-trace 32 - i.e. the magnetic field strength increases with the amplitude Akx. As discussed above, in some embodiments,
for all the x-current phases hx. For the sake of brevity, much of the discussion that follows will assume without loss of generality. A stronger magnetic field creates a corresponding steeper potential energy well having a more pronounced local minimum, which in turn more strongly traps/locks moveable stage 10 and permits improved motion tracking error of moveable stage 10, but at the expense of greater energy consumption, where motion tracking error in Y means the difference between the actual stator-y direction location of stage 10 in and its desired stator-y direction location yr and motion tracking error in X means the difference between the actual stator-x direction location of stage 10 and its desired stator-x location xr. The actual stator-x direction location of stage 10 can be the actual stator-x direction location of the geometric center of the stator 10 magnetic assembly 16. The actual stator-y direction location of stage 10 can be the actual stator-y direction location of the geometric center of the stator 10 magnetic assembly 16.
[0138] During implementation, it may be desired to vary Ax from time to time to accord with motion tracking objectives and/or power consumption objectives. In some embodiments, the amplitude Ax may be varied based on reference trajectory acceleration (i.e. the 2nd time
derivative (acceleration) of yr). For example, in some embodiments, the amplitude Ax may be positively correlated with the acceleration of yr - e.g. Ax may be increased when the acceleration of yr is relatively high (i.e. there is a desire to change the velocity of moveable stage 10 relatively quickly in the stator-y direction) and decreased when the acceleration of yr is relatively low (i.e. there is a desire to keep moveable stage 10 relatively stationary or moving with constant velocity in the stator-y direction). For example, in some embodiments, the amplitudes Ax may be varied linearly with the desired acceleration of yr according to: Ax = A0 + a\yr(t) | , where A0 represents a minimum current amplitude, a is a positive design parameter and yr(t) is the desired acceleration of moveable stage 10. Other relationships between amplitude Ax and yr(t) may provide suitable results, as long as Ax increases with |yr(t) l - For example, an alternative relationship is: Ax = A0 + ayr 2 (t). In these ways, the system can move moveable stage 10 with a low tracking error in the stator-y direction and high acceleration rates during acceleration, and minimize power consumption during relatively stationary states and relatively low acceleration (constant speed) states (i.e. zero acceleration states). As indicated, the amplitude Ax of trace currents ix may still be nonzero (e.g. AX=A0), even when the moveable stage has no desired acceleration in stator-y direction. It will be appreciated that the amplitudes Ajy (or Ay with the above-discussed assumption) of the y-current phases ijy (e.g. from equations (3) and (4)) can be varied with the desired acceleration of moveable stage 10 in the stage-x direction (i.e. \xr (t) |) in an analogous manner.
[0139] It will be appreciated that the acceleration compensation techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
High Frequency Amplitude Modulation and Phase Modulation of Coil Trace Currents
[0140] In some applications, there may be friction forces which act against translational motion of moveable stage 10 and/or friction torques which act against rotation of moveable stage 10 around a stator-z oriented axis. Such friction may result from contact between the stage and stator bearing surfaces 124, 126. Such friction forces/torque can cause tracking error (i.e. where moveable stage 10 does not exactly track the desired reference parameters (xr, yr, rZr)). Tracking errors may be understood to be the difference between actual positions
of a moveable stage 10 (e.g. the actual position of the geometric center of the magnet array assembly 16 corresponding to moveable stage 10) and the desired reference positions (xr, yr, rzr) of the moveable stage 10. In feedback based control, tracking errors can be fed back to the control system, which can compensate for such tracking errors. However, in some embodiments, control system 54 (Figure 13 A) operates without using real-time position based feedback. Consequently, to minimize tracking errors arising from friction, some embodiments make use of a dynamic lubrication method.
[0141] In some embodiments, dynamic lubrication (for x-current phases ihd involves modulating current phase amplitudes Ax and/or modulating current phase phase angles φχ at temporal frequencies - e.g. at temporal frequencies in a range of 50Hz to 40kHz in some embodiments. For example, in the waveforms for each x-current phase the amplitude Ax and phase ψχ can be generated in the following way:
AX = A0 + k \yr(t) \ + Adsm(o)At + ψΑ) (5a) ψχ = ψ0 + ψα sin ( ωφί + ψφ)
(5b)
where Ad is dynamic lubrication modulation amplitude for the current phase amplitude Ax, ωΑ is the temporal modulation frequency for the current phase amplitude Ax, ψχ is the above discussed phase parameter, φ0 is an constant phase angle, <pd is modulation amplitude for the current phase phase ψχ, ωφ is modulation frequency for the current phase phase ψχ, ψΑ and ψφ are arbitrary constant modulation phase angles for amplitude modulation and phase modulation, respectively.
[0142] High frequency amplitude and/or phase modulation of x-current phases ¾ can generate high frequency vibration in the stator-z and stator-y directions and such vibration can help attenuate normal direction (stator-z direction) contact force between bearing surfaces 124, 126 of moveable stage 10 and stator 30 and thus attenuate friction force which tends to inhibit motion in in the stator-y direction. Consequently, this effect can help reduce moveable stage tracking errors. In some embodiments, this dynamic lubrication modulation is used only in particular circumstances. For example, in some embodiments, dynamic lubrication modulation may be used when moveable stage 10 is in a relatively stationary state or when moveable stage 10 is moving at a relatively constant speed (i.e. when the desired acceleration parameter |yr(t) l is relatively low). In some embodiments, dynamic lubrication may be used
at all times or at select occasions based on other parameters associated with the desired position yr of moveable stage 10.
[0143] The modulation frequencies ωΑ and ωφ can be identical or can be set at different values. In one exemplary embodiment, one or both of modulation frequencies ωΑ and ωφ are set at or near one resonant frequency of moveable stage 10 in the stator-z direction dynamics. In this description and the accompanying claims, the phrase at or near a resonant frequency should be understood to mean at the resonant frequency +/-10%. Due to resonance, the modulation-induced vibration can achieve maximum vibration amplitude. Some
embodiments involve setting Qa)A= Ιϊωφ, where Q and R may be any positive or negative integer numbers. For example, when Q=R=\ , a 2-D rotating nearly elliptical force vector (with force components in the stator-y and stator-z directions) will act on moveable stage 10. Such elliptical excitation by amplitude modulation and phase modulation of x-traces 32 can result in very small amount of motion along the stator-y direction. This elliptical excitation can be used to achieve fine motion control of moveable stages 10 and/or be used to minimize friction-induced motion tracking error or steady-state positioning error.
[0144] It will be appreciated that the amplitudes Ajy (or Ay with the above-discussed assumption) and/or phases <py of the y-current phases ijy, can be similarly modulated at temporal frequencies - e.g. at temporal frequencies in a range of 50Hz to 40kHz in some embodiments. For example, in the waveforms for each y-current phase ijy, the amplitude Ay and phase <py can be generated in the following way:
Ay = A0 + k \xr(t) \ + Adsin(a)At + ψΑ) (6a)
<P = <Po + φα $∞( ωφ ί + ψφ)
(6b)
where Ad is dynamic lubrication modulation amplitude for the current phase amplitude Ay, ωΑ is the temporal modulation frequency for the current phase amplitude Ay, <py is the above discussed phase parameter, φ0 is an constant phase angle, ψά is modulation amplitude for the current phase phase (py, ωφ is modulation frequency for the current phase phase (py, ψΑ and ψφ are arbitrary constant modulation phase angles for amplitude modulation and phase modulation, respectively. In equations (5) and (6), the dynamic lubrication parameters A0, φ0, Ad, ψο, ωΑ, ωφ , ψΑ and ψφ are the same for x-current phases and y-current phases ijy, but
this is not necessary and these parameters may be different for x-current phases ¾ and y- current phases ijy.
[0145] It will be appreciated that the amplitude and phase modulation techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
Impulse excitation for fine positioning
[0146] In some embodiments, fine position control of moveable stage 10 may involve application of impulse signals to an initial amplitude and/or initial phase. Impulses may be used to finely adjust the moveable stage when the desired position (xr, yr) remains static. Increasing the amplitudes of current phases ijy (as discussed above) can minimize tracking error caused by friction forces - i.e. moveable stage 10 may be brought closer to the minimum magnetic potential energy location (xr,yr) at higher amplitudes of current phases ijy. Once a moveable stage 10 moves close to its minimum energy location (xr,yr), moveable stage 10 will be latched there by friction force and the amplitudes of current phases ¾, can be decreased to reduce power consumption. At this stage, in some embodiments, the fine position of moveable stage 10 can be controlled using impulse control as described in more detail below.
[0147] Figure 15 A shows amplitude Ax and phase ψχ impulses for an x-current phase hx according to a particular embodiment. Similar impulses can be provided to the amplitudes Ax and phases ψχ for other x-current phases hx. As shown in Figure 15 A, the amplitude Ax which is at an initial level of A0 prior to i;, suddenly increases to a first impulse amplitude Ao+Aj at time i; for a first temporal period At and then, at time t2, decreases to a lower level. In some embodiments, the lower level (after ti) is Ao, while in other embodiments it may be a different amplitude. Similarly, the phase ψχ which is at an initial level of φ0 prior to i;, suddenly increases to a first impulse amplitude φ0 + ψι at time i; for a first temporal period At and then, at time t2, decreases to a lower level. In some embodiments, the lower level (after ti) is φ0, while in other embodiments it may be a different from φ0. In some embodiments, the phase impulse strength ψ, may be positive or negative. For example, ψ, can be +π/2 or — π/2 or other values. It will be appreciated that amplitude and phase impulses having similar characteristics may be applied to the amplitude Ay and phase <py of y-current phases ijy. Such
phase impulses in x-traces can also help achieve stator-y acceleration of moveable stage 10.
[0148] In some embodiments, the impulse duration is in a range of 0<At<10 minutes. In some embodiments, the impulse duration is in a range of 0<At<l minute. In some embodiments, the impulse duration is in a range of 0<At<l second. In some embodiments, the impulse duration is in a range of 0<At<0.1 second. The impulses in the amplitudes and phases of x-current phases 4* will create impact forces on moveable stage 10 in the stator-y direction and stator-z direction; and impulses in the amplitudes and phases of y-current phases ijy will create impact forces on moveable stage 10 in the stator-x direction and stator-z direction. The resulting impact forces may create small amounts of motion which can help with the fine position of moveable stage 10.
[0149] While the illustrated embodiment of Figure 15 A shows a rectangular impulse waveform, this is not necessary. In some embodiments, impulses of any arbitrary waveform shapes can additionally or alternatively be used. For example, impulses having triangular, rounded or other waveform shapes may be used. Some embodiments involve imparting impulses on the amplitudes Ax (or Ay) of x-current phase 4* (or y-current phases ijy) without imparting impulses on the phases (i.e. <P/=0). Some embodiments involve imparting impulses on the phases ψχ (or <py) of x-current phase * (or y-current phases ijy) without imparting impulses on the amplitudes (i.e. A/=0). Figure 15B shows a series of amplitude Ax and phase ψχ impulses for an x-current phase * according to a particular embodiment. Each impulse in the Figure 15B series may have parameters similar to the impulses described above in connection with Figure 15 A. Using a series of impulses like those shown in Figure 15B, moveable stage 10 can experience a series of impact forces. The impact strength of the series of impulses (e.g. the parameter Aj) can vary from one impulse to another (e.g. decreasing over time), as illustrated in Figure 15B. It will be appreciated that a similar series of amplitude Ay and phase (py impulses could be used for y-current phases ijy. A series of impulses can be used to generate a series of impulse forcse and thus fine step motion to minimize tracking error, with the aid of suitable feedback position sensors.
[0150] Figure 15C shows an exemplary moveable stage fine positioning process according to a particular embodiment in which a first amplitude impulse 61 A is applied to the x-current phases 4* at a time and lasts for a period of time At before a second amplitude impulse 61B is applied to the y-current phases ijy at a time t2. Each impulse 61 A, 61B may have features
similar to the amplitude impulse described above in Figure 15A. First impulse 61 A may be applied to all of the x-current phases hx and second impulse 6 IB may be applied to all of the y-current phases ijy. In the illustrated embodiment of Figure 15C, t2-ti>At, such that the amplitude Ay of the y-current phases ijy remains at its pre-impulse level (Ay=A0y in the illustrated embodiment) when impulse 61 A is applied to the x-current phases ¾ and, similarly, the amplitude Ax of the x-current phases ¾ remains at its post-impulse level (Ax=A0x in the illustrated embodiment) when impulse 61 B is applied to the y-current phases ijy. While only exerting impulse excitation on one of x-current phases ¾ and y-current phases ijy at a time can help to avoid issues associated with developing excess heat, this feature of the Figure 15C embodiment is not necessary. In some embodiments, impulses 61A, 61B may overlap temporally. That is, the start time t2 of impulse 61B may occur at a time less than ti+At and the finish time t2+At may occur at a time after tj+At. In general, the start time of impulse 61B may be one of before and after the start time of impulse 61 A and the finish time of impulse 6 IB may be the one of before and after the finish time of impulse 61 A. In general, the duration Atj of impulse 61 A may be different that the duration At2 of impulse 61B. Figure 15C shows only amplitude impulses 61A, 61B. In some embodiments, one or both of amplitude impulses 61 A, 6 IB could be accompanied by phase impulses having
characteristics similar to those shown in Figure 15 A.
[0151] Figure 15D shows an exemplary moveable stage fine positioning process in which a first amplitude impulse 61 A is applied to the x-current phases ¾ at a time i; and lasts for a period of time At before a second amplitude impulse 61B is applied to the y-current phases ijy at a time t2. The fine positioning process of the Figure 15D embodiment differs from the fine positioning process of the Figure 15C embodiment in that during first impulse 61A applied to the x-current phases hx (i.e. from the time i; to tj+At in the illustrated embodiment), the amplitudes Ay of the y-current phases ijy are reduced to a low level (e.g. to zero or some other suitable low level) from their nominal level A0y and, similarly, during second impulse 61B applied to the y-current phases ijy (i.e. from the time t2 to t2+At in the illustrated embodiment) the amplitudes Ax of the x-current phases hx are reduced to a low level (e.g. to zero or some other suitable low level) from their nominal level A0x. This Figure 15D amplitude reduction during the application of impulses 61 A, 61 B can reduce heat generated during impulses 61 A, 6 IB and may also reduce the normal direction contact force between moveable stage 10 and
stator 30 during impulses 61 A, 6 IB, and thus further minimize friction force induced positioning error. It will be appreciated that phase impulse excitation may have properties similar to that of amplitude impulse excitation described herein.
[0152] It will be appreciated that the impulse excitation fine positioning techniques described in this section may be applied to any of the displacement devices 50 described herein, any of the moveable stages 10 described herein and any of the stators 30 described herein.
Initialization of moveable stages
[0153] In some embodiments, during operation, displacement device 50 and its control system 58 operate without real-time position feedback (i.e. control system 58 does not require real-time positions of moveable stage(s) 10). However, in some embodiments, it may be beneficial for control system 58 to know initial location(s) of moveable stage(s) 10 (e.g. on startup). The initial location of a moveable stage 10 is useful for determining the coil traces 32, 34 into which current phases ijy should be driven to control the position of the moveable stage 10. Several techniques for determining an initial position(s) of moveable stage(s) 10 are described herein.
[0154] One example way to determine initial position of moveable stage(s) 10 involves using one-by-one initialization. One-by-one initialization comprises positioning a moveable stage 10 at a specific well-defined start location by other means, such as manually or by a robotic arm/hand. Figure 16A is a schematic depiction of how a one-by-one initialization process may be used to determine an initial location of a moveable stage in a displacement device 550 according to a particular embodiment. In the Figure 16A displacement device 550, a predefined region 563 is defined for placing a moveable stage 510 upon startup. In some embodiments, placing moveable stage 510 in start region 563 may comprise abutting moveable stage 510 against alignment device 565. In some embodiments, coil traces 32, 34 overlapping start region 563 in the stator-z direction may be switched off (i.e. may not be driven with current phases i^, ijy) during the process of locating moveable stage 510 in start region 563 - i.e. to minimize interacting forces between moveable stage 510 and stator 530. By placing moveable stage 510 in region 563 and, optionally, pushing or otherwise abutting moveable stage 510 against alignment device 565, moveable stage 510 will be positioned at start region 563. Once the location of moveable stage 510 is approximately known, control
system 58 may drive current phases ijy into coil traces 32, 34 in region 563 and may move moveable stage 510 away to other locations in working region 536, whereupon moveable stage 510 is fully controlled by control system 58 and its corresponding current phases ijy. Once a first moveable stage 510 is under the control of control system 58, the initialization procedure can be repeated for a next moveable stage 10.
[0155] Figure 16B depicts an alignment device 565' according to another embodiment which may be used with displacement device 550 and the one-by-one initialization technique of Figure 16A. Alignment device 565' comprises one or more alignment features 566, which may interact physically with complementary alignment features (not shown) in moveable stages 510 to assign with one-by-one initialization as described above. In the Figure 16B embodiment, alignment features 566 each comprise a corresponding protrusion that may be received in a complementary recess in moveable stage 510. It will be appreciated that complementary pairs of alignment features 566 in alignment device 565' and moveable stage 510 could have a variety of other shapes. For example, moveable stage 510 may additionally or alternatively comprise one or more beveled surfaces and/or protrusions and alignment features 566 may additionally or alternatively comprise one or more complementary shaped beveled surfaces and/or recesses.
[0156] Figure 16C schematically depicts a displacement device 550" comprising a stator 530" and a plurality of moveable stages 510" according to another embodiment. Figure 16C illustrates a group initialization technique for determining the initial positions of moveable stages 510". Moveable stages 510" are organized side by side to form a pattern either manually or with the aid of a robot device. An optional alignment device 565" (having features similar to alignment devices 565, 656') may be provided and used to facilitate organizing these moveable stages 510". Moveable stages 510" can be organized into a rectangular matrix pattern, for example. In the exemplary embodiment of Figure 16C, eleven moveable stages 510 are organized into three rows, with the third row not completely filled. Next, information in relation to the organized pattern of moveable stage 510" is input into control system 58 (e.g. controller 60) via a graphical user interface 567" (or by any other suitable input interface). In this way, control system 58 will roughly know the positions of each moveable stage 510" with an accuracy to within a small fraction of spatial periods (λχ,λγ). With this information, control system 58 can drive moveable stages 510" and separate
moveable stages 510" from each other with an appropriate algorithm.
[0157] Alignment devices 565, 565', 565" are optional. For example, when a robot device is used to initialize the positions of moveable stages, alignment devices 565, 565', 565" may not be needed as positional feedback from the robot device (such as positional feedback related to the position of a robot arm/hand) may be sufficient to position each moveable stage accurately. Initialization may occur only once (e.g. when a displacement device is first powered on). In some embodiments, before powering off the displacement device, control system 58 can drive the moveable stages back to their initialization locations. As a result, when the displacement device is powered on again, the moveable stages should be very close to the desired pattern with minimum requirement from an operator. In this sense, only the very first initialization needs some effort to organize the moveable stages to form a matrix pattern, although these methods can be used for adding additional moveable stages or in other situations.
Moveable stage motion path patterns
[0158] Displacement devices according to particular embodiments provide flexibility with respect to the motion paths over which moveable stages can be controllably moved, especially when compared to conventional belt-based conveyor or track systems, where the one-dimensional track location and sizes are fixed after manufacturing. For the purpose of illustrating a number of exemplary motion paths of moveable stages, Figure 17A
schematically depicts the working region 36 of a stator 30 divided into a plurality of excitation regions 43 according to a particular embodiment. Each excitation region 43 is associated with one or more amplifier(s) 70 to drive current phases ijy into its x-traces 32 and its y-traces 34. For the examples that follow, it will be assumed (without loss of generality) that the current phases ¾, are driven with a three phase configuration similar to that described above, although this is not necessary. In each excitation region 43, the x- current phases are independent from the y-current phases ijy. Figure 17B shows one exemplary moveable stage 10, which may be used with the Figure 17A stator 30. Moveable stage 10 of the Figure 17B embodiment comprises a magnet array assembly 16 and bumper 17, which surrounds magnet array assembly 16. It will be understood that although moveable stage 10 of the Figure 17B embodiment is depicted as being square with a bumper
surrounding the perimeter, it may be of any suitable shape or form, such as any of at least the moveable stages described herein.
[0159] Figure 17C shows one motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30. The Figure 17C embodiment provides a path 69A (e.g. an oval shaped path 69A), along which a plurality (e.g. nine) moveable stages 10 can move bi-directionally. The Figure 17C embodiment also provides two entry/exit paths 69B (shown in dashed lines). Moveable stages 10 moving along path 69 A can exit via either one of entry/exit paths 69B. Similarly, moveable stages 10 outside path 69 A can enter path 69 A via one of entry/exit paths 69B. The exact size of the oval shaped path 90 can be dynamically changed by control software to meet certain application needs. Moreover, the numbers, sizes and/or locations of exit/entry paths 69B can also be dynamically changed by control software as desired.
[0160] Figure 17D shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30. Moveable stages 10 move along two paths 69A' and 69 A" (e.g. circular paths 69A', 69A"). One moveable stage 10 can transition from one path 69 A' to another path 69A", or vice versa. Alternatively, a moveable stage 10 can move out of both circular paths 69A', 69A". Figure 17E shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30 which mimics a conventional oval shaped conveyer system by moving moveable stages 10 along a path 69 A. The motion of moveable stages 10 can be bi-directional and the shape and size of the path 69A can be dynamically adjusted by software. Figure 17F shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17 A stator 30. Figure 17F is similar to Figure 17D in that moveable stages 10 move along two paths 69A' and 69 A", except that the Figure 17F paths 69A', 69A" have different shapes than the Figure 17D paths.
[0161] Figure 17G shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30. Figure 17G shows that groups of moveable stages 10 can move together very closely. Different groups of moveable stages 10 can pass each other in opposite directions. Different groups of moveable stages 10 can have individual moveable stages 10 spaced apart by varying distances. Groups of moveable stages 10 can comprise any suitable number of available moveable stages 10. Individual moveable stages
10 can switch between groups or form new groups. Figure 17H shows another motion pattern of a plurality of the Figure 17B moveable stages 10 relative to the Figure 17A stator 30. Figure 17H shows that a matrix group of moveable stages 10 (e.g. 9 moveable stages 10 in a 3 by 3 matrix group) can also move together and have independent motion from another linear group of moveable stages 10, and two groups can pass each other. Moveable stages 10 can form into linear (ID) groups, or matrix (2D) groups as shown in Figure 17H. Each moveable stage 10 may have completely independent motion from all other moveable stages 10. A plurality of moveable stages 10 can form into groups and a group of moveable stages 10 can also ungroup themselves to allow independent motion for each moveable stage 10.
[0162] When a plurality of moveable stages 10 move together in a queue with space in between each moveable stage 10, such as in the Figure 17F example, each moveable stage 10 can achieve independent motion control, can flexibly move out of the moving queue
(dynamic exit), and can also allow other in-coming moveable stages 10 to merge into an existing queue (dynamic entry).
[0163] Figures 18A-18F schematically illustrate one exemplary embodiment of a process of a number of the Figure 17B moveable stages 10 ungrouping from one another. In Figure 18 A, nine moveable stages 1 OA- 101 form a group to move together relative to a stator 30 (e.g. the Figure 17A stator 30, in the illustrated embodiment). Stator 30 includes a plurality of independently driven current excitation regions 43 shown in dashed outline, each pair of excitation regions separated by a corresponding boundary plane. These boundary planes may be oriented in stator- x-stator-z planes or stator-y-stator-z planes. In some embodiments, the center-to-center distance between moveable stages 10 may comprise integer multiples of the first and second array spatial periods (λγ=λι, λχ=λ2), the magnet array assemblies 16 of moveable stages 10 grouped as shown in Figure 18A can share corresponding current phases ikx, ijy, which couples their motion together. One technique for ungrouping the Figure 18A moveable stages 10 comprises: (a) the group moves in a first stator-x direction as shown in Figure 18A until the group reaches the location shown in Figure 18B, where moveable stages 10A, 10D and 10G are located in excitation regions 43 decoupled from the rest of the group; (b) moveable stages 10A, 10D, 10G may then be driven in the first stator-x direction away from the other moveable stages 10 using suitable y-current phases ijy (which may be the same for each of moveable stages 10A, 10D, 10G). As shown in Figure 18C, during this time the
rest of the moveable stages (10B, IOC, 10E, 10F, 10H, 101) in the group may be held stationary or may be driven in the second (i.e. opposite to the first) stator-x direction by suitable y-current phases ijy. As a result, stages 10A, 10D, 10G are independently driven from the rest of the group; (c) moveable stages 10A, 10D, 10G are then driven in a first stator-y direction (as shown in Figure 18D) using suitable x-current phases ¾ until stage 10G is located in an excitation region 43 that is decoupled from stages 10A and 10D; (d) As shown in Figure 18E, during this time, stage 10G is further driven in the first stator-y direction using suitable x-current phases while the rest of moveable stages 10A, 10B, IOC, 10D, 10E, 10F, 10H and 101 may be held stationary or may be driven in the second (i.e. opposite to the first) stator-y direction by suitable x-current phases hx. As a result, moveable stage 10G separates from moveable stages 1 OA, 10D (as shown in Figure 18E); and (e) as shown in Figure 18F, moveable stage 10G can now achieve independent motion in stator-x and stator-y directions. In similar ways, the other moveable stages 10 can be ungrouped to achieve independent motion in the stator-x and stator-y directions.
[0164] By reversing the above process, a plurality of moveable stages 10 can form into linear (1 -dimensional) group(s) or a matrix (2-dimensional) group(s). This is useful in queuing for saving space or in high speed movement of a relatively large number of moveable stages 10.
[0165] In general, the currents in different excitation regions may be controllably driven to cause a first group of one or more moveable stages to separate from a second group of one or more moveable stages by: driving the currents to position the plurality of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages (e.g. magnet assemblies of the first group of moveable stages and magnet assemblies of the second group of moveable stages are on opposite sides of the first boundary plane); and driving the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: move the first group of moveable stages in a first direction away from the first boundary plane; and move the first group of moveable stages in a first direction aware from the second group of moveable stages, the first direction parallel with the first boundary plane; while driving the plurality of currents in at least some of the coil traces of the second excitation region to at least one of: maintain the location of the second group of moveable
stages within the working region; and move the second group of moveable stages in a second direction away from the first boundary plane; and move the second group of moveable stages in a direction away from the first group of moveable stages, the second directional parallel with the first boundary plane. The first boundary plane between the first and second excitation regions may be in either a stator-x-stator-z plane or a stator-y-stator-z plane.
Similarly, a second plurality of currents in different excitation regions may be controllably driven to cause a first sub-group of the first group of moveable stages to separate from a second sub-group of the first plurality of moveable stages by: driving the second plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a second boundary plane extending in a stator-z direction between a third excitation region of the plurality of excitation regions and a fourth excitation region of the plurality of excitation regions divides the first sub-group and the second sub-group of the first group of moveable stages (e.g. magnet assemblies of the first and second sub-groups are on opposite sides of the second boundary plane); and driving the second plurality of currents in at least some of the coil traces of the third excitation region to at least one of: move the first sub-group of moveable stages in a third direction away from the second boundary plane; and move the first sub-group of moveable stages in a third direction away from the second sub-group of moveable stages, the third direction parallel with the surface of the second boundary plane; while driving the second plurality of currents in at least some of the coil traces of the fourth excitation region to at least one of: maintain the location of the second sub-group of moveable stages within the working region; and move the second sub-group of moveable stages in a fourth direction away from the second boundary plane; move the second sub-group of the moveable stages in a fourth direction away from the first sub-group of moveable stages, the fourth direction paralle with the surface of the second boundary plane. The second boundary plane may be in one of a stator- x-stator-z plane and a stator-y-stator-z plane and may be orthogonal to the first boundary plane. The third excitation region may be one of the first excitation region and the second excitation region. The fourth excitation region may be one of the first excitation region and the second excitation region, but is different than the third excitation region.
[0166] Some aspects of the invention provide methods for controlling the movement of a plurality of moveable stages relative to a stator to separate a first group of one or more
moveable stages from a second group of one or more moveable stages. Each moveable stage among the first and second groups of moveable stages may be similarly constructed with one or more magnet arrays, the one or more magnet arrays comprising at least one magnet array comprising a plurality of magnetization segments, each magnetization segment having a corresponding magnetization direction. The methods comprise: providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide a plurality of stator-z-direction-non-overlapping excitation regions, each excitation region comprising: a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer; and a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction. The first and second portions of the first and second layers may overlap one another in a stator-z direction throughout the excitation region. The stator-z direction may be generally orthogonal to both the stator-x direction and the stator-y direction. The method may also comprise controllably driving a plurality of currents into the plurality of electrical coils to thereby cause a first group of one or more of the plurality of moveable stages to separate from a second group of one or more of the plurality of moveable stages. Controllable driving the plurality of currents into the plurality of electrical coils may comprise: driving the plurality of currents into the plurality of electrical coils to position the plurality of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages; driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: move the first group of moveable stages in a first direction away from the first boundary plane; and move the first group of moveable stages in a first direction away from the second group of moveable stages, the first direction parallel with the first boundary plane surface; while driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region, driving at least some of the plurality of currents in at least some of the coil traces of the second excitation region to at least one of: maintain a location of the second group of moveable stages within the working region; move the second group of moveable stages in a second direction away from the first boundary plane; and move the second group
of moveable stages in a second direction away from the first group of moveable stages, the second direction parallel with the first boundary plane surface The first boundary plane between the first and second excitation regions may be in one of a stator-x-stator-z plane and a stator-y-stator-z plane.
[0167] The method may comprise controllably driving a second plurality of currents into the plurality of electrical coils to thereby cause a first sub-group of the first group of moveable stages to separate from a second sub-group of the first group of moveable stages.
Controllably driving the second plurality of currents into the plurality of electrical coils may comprise: driving the second plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a second boundary plane extending in the stator-z direction between a third excitation region of the plurality of excitation regions and a fourth excitation region of the plurality of excitation regions divides the first sub-group and the second sub-group of the first group of moveable stages; and driving at least some of the second plurality of currents in at least some of the coil traces of the third excitation region to at least one of: move the first sub-group of the first group of moveable stages in a third direction away from the second boundary plane; and move the first sub-group of the first group moveable stages in a direction away from the second sub-group of the first group of moveable stages, the third direction parallel with the second boundary plane surface; while driving at least some of the second plurality of currents in at least some of the coil traces of the third excitation region, driving at least some of the second plurality of currents in at least some of the coil traces of the fourth excitation region to at least one of: maintain the location of the second sub-group of the first group of moveable stages within the working region; move the second sub-group of moveable stages in a fourth direction away from the second boundary plane; and move the second sub-group of the first group of moveable stages in a fourth direction away from the first sub-group of the first group of moveable stages, the fourth direction parallel with the second boundary plane surface. The second boundary plane may be in one of a stator-x-stator-z plane and a stator-y-stator-z plane and may be orthogonal to the first boundary plane. The third direction may be orthogonal to the first direction. The third excitation region may be one of the first excitation region and the second excitation region. The fourth excitation region may be one of the first excitation region and the second excitation region, but may be different than the
third excitation region. A stator-z location of the third layer may be the same as one of: a stator-z location of the first layer; and a stator-z location of the second layer.
[0168] In some embodiments, for each moveable stage in the first and second groups of moveable stages: a stator-x dimension of the first excitation region is greater than a stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage; a stator-y dimension of the first excitation region is greater than a stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage; a stator- x dimension of the second excitation region is greater than the stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage; a stator-y dimension of the second excitation region is greater than the stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage. Driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region may comprise driving currents with similar periodicity but with different phases into the first plurality of coil traces. In some embodiments, driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region may comprise driving currents with similar periodicity but with different phases into the second plurality of coil traces.
[0169] Similarly, the process may be reversed and the currents in different excitation regions may be controllably driven to cause a first group of one or more moveable stages to abut against, or be close (e.g. within a distancel.5 i or 1.5λ2) to, a second group of one or more moveable stages by: driving the plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions, divides the first and second groups of moveable stages (e.g. magnet assemblies of the first group of moveable stages and magnet assemblies of the second group of moveable stages are on opposite sides of the first boundary plane); and driving the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: maintain the location of the first group of moveable stages within the working region; and move the first group of moveable stages in a first direction toward the first boundary plane; move the first group of moveable stages in a first direction toward the second group of moveable stages, the first direction parallel to the surface of the
first boundary plane; while driving the plurality of currents in at least some of the coil traces in the second excitation region to at least one of: move the second group of moveable stages in a second direction toward the first boundary plane; and move the second group of moveable stages in a second direction toward the first group of moveable stages, the second direction parallel with the surface of the first boundary plane.
[0170] Some aspects of the invention provide methods for controlling the movement of a plurality of moveable stages relative to a stator to bring the moveable stages into close proximity to one another. The method comprises: providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide a plurality of excitation regions, each excitation region comprising: a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer; a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction. The first and second portions of the first and second layers may overlap one another in a stator-z direction throughout the excitation region, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction. The method may comprise: providing a plurality of moveable stages moveable relative to the stator within a two-dimensional working region, each moveable stage comprising one or more magnet arrays, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction; and controllably driving a plurality of currents into the plurality of electrical coils to thereby cause a first group of one or more of the plurality of moveable stages within one magnet array dimension to a second group of one or more of the plurality of moveable stages. Controllably driving the plurality of currents into the plurality of electrical coils may comprise: driving the plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between a first of the plurality of excitation regions and a second of the plurality of excitation regions divides the first and second groups of moveable stages; and driving the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: maintain the location of the first group of moveable stages within the working region; move
the first group of moveable stages in a first direction toward the first boundary plane; move the first group of moveable stages in a first direction towards the second group of moveable stages, the first direction parallel to the surface of the first boundary plane; while driving the plurality of currents in at least some of the coil traces in the second excitation region to at least one of: move the second group of moveable stages toward the first boundary plane; move the second group of moveable stages in a second direction toward the first group of moveable stages, the second direction parallel to the first boundary plane surface.
Rotating motion of moveable stage with the aid of a-coil traces
[0171] Figures 19A-19G schematically depict a technique for implementing rotational motion of a moveable stage 610 about a stator-z oriented axis according to a particular embodiment. The technique of Figures 19A-19G is shown for a displacement device incorporating a magnet array assembly 616 and a coil trace assembly 635 according to specific embodiments, but by suitable modification which will be understood to those skilled in the art after the following explanation, the technique of Figures 19A-19G can be applied to other displacement devices described herein. Figure 19A shows a magnet array assembly 616 of a moveable stage 610 according to a particular embodiment which is used to facilitate the illustration of Figures 19A-19G.
[0172] As illustrated in Figure 19B, stator 630 comprises a-coil traces 633 distributed over at least a portion of a a-trace layer 649 which are oriented at an angle a° relative to the positive stator-x axis. In general, a may be any angle between 0°-90°. To facilitate explanation, it will be assumed, without loss of generality, that a-coil traces 633 are oriented at 45° relative to the positive stator-x axis. Current phases ka may be driven into a-coil traces 633. Such current phases ka may have properties similar to the x-current phases ¾ and/or the y-current phases ijy, except that there may be a different (or the same) spatial period λα. By orienting coil traces 633 to be elongated at 45° relative to the positive stator-x axis, the traveling magnetic field wave generated by the current phases driven into coil traces 633 is generated such that moveable stage 610 will have a local minimum potential energy when magnet array assembly 616 is in the 45°-orientation shown in Figure 19D. With this potential energy minimum, moveable stage 10 will tend to rotate around a stator-z oriented axis 671 from the 0° orientation shown in Figure 19B, through the orientation in Figure 19C to reach the 45°-
orientation illustrated in Figure 19D. During this rotation, the position of the center of moveable stage 610 (through which stator-z oriented axis 671 extends) may remain nearly unchanged in the stator-x, stator-y coordinate system. In addition or in the alternative to using 45°-current phases driven into 45°-traces 633 to effect the rotation of moveable stage 610 between the 0° (Figure 19B) orientation and the 45° (Figure 19D) orientation, 135°-current phases could be driven into 135°-traces 633' in 135°-trace layer 649' to effect the rotation of moveable stage 610 between the 0° (Figure 19B) orientation and the 45° (Figure 19D) orientation.
[0173] After moveable stage 610 rotates to the orientation shown in Figure 19D, y-current phases ijy may be driven into y-traces 634 in y-trace layer 642 (Figure 19E) to achieve further rotation about stator-z oriented axis 671. When y-current phases ijy are driven into y-traces 634, the traveling magnetic field wave generated by y-current phases ijy is generated such that moveable stage 610 will have a local minimum potential energy when magnet array assembly 616 is in the 90°-orientation shown in Figure 19G. With this potential energy minimum, moveable stage 10 will tend to rotate around stator-z oriented axis 671 from the 45° orientation shown in Figure 19E, through the orientation in Figure 19F to reach the 90°- orientation illustrated in Figure 19G. During this rotation, the position of the center of moveable stage 610 (through which stator-z oriented axis 671 extends) may remain nearly unchanged in the stator-x, stator-y coordinate system. In addition or in the alternative to using y-current phases ijy to effect the rotation of moveable stage 610 between the 45° (Figure 19E) orientation and the 90° (Figure 19G) orientation, x-current phases ¾ could be driven into x- traces 632 in x- trace layer 640 to effect the rotation of moveable stage 610 between the 45° (Figure 19E) orientation and the 90° (Figure 19G) orientation.
[0174] Since magnet array assembly 616 is 90° rotationally symmetric about stator-z oriented axis 671, the Figure 19G orientation is magnetically equivalent to the Figure 19B orientation. Consequently, further rotation about axis 671 can be achieved by suitable repetition of the above-described procedures using 45°-current phases and/or 135°-current phases and x- current phases and/or y-current phases ijy.
[0175] The rotation techniques and coil trace assemblies described in Figures 19A-19G are described with application to magnet array assembly 616. It will be appreciated that magnet array assembly 616 has a layout similar to magnet array assembly 416A (Figure 5A). Any of
the rotation techniques and coil trace assemblies described in Figures 19A-19G may be used with magnet array assembly 416A (or a left-handed version thereof - see description of left- handed versus right-handed magnet arrays above) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE. Figure 5B shows a left-handed magnet array assembly 416B that is different than magnet array assembly 416 A (Figure 5 A) in that the individual magnet arrays of magnet array assembly 416B are offset and spaced apart from one another as described above. Regardless, any of the rotation techniques and coil trace assemblies described in Figures 19A-19G may be used with magnet array assembly 416B (or a right-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE.
360° Rotation Control Methods for ID magnet array assembly
[0176] In some embodiments, moveable stages 10 comprising ID magnet array assemblies 16 (e.g. magnet array assemblies 16 of the type shown in Figures 5A, 5B, 5E, 5G, 51) may be capable of fully controllable 360° rotation about a stator-z oriented axis using current phases driven into coil traces having any two or more directions (e.g. x-current phases ¾ driven into x-traces 32 and y-current phases ijy driven into y-traces 34). Figures 20A and 20B
respectively depict the generation of y-current phases ijy and x-current phases ija which may be used to achieve controllable 360° rotation about a stator-z oriented axis according to a particular embodiment. The particular embodiment of Figures 20A and 20B is a three-phase embodiment where the number of effective phases np=mp=3. The top portion of Figure 20 A shows the generation of three y-current phases y, ijy, according to:
where Ay is an amplitude (assumed, in the illustrated embodiment, to be the same for all of the y-current phases i0y, iiy, ¾)> λ2=λχ is a spatial period in the stator-x direction, and (py is a phase offset. It can be seen from equations (7), that the magnetic field generated by the y- current phases ijy travel in the stator-x direction with xr — dr in the stator-x direction, where xr is a reference stator-x trajectory and dr is a differential reference quantity used to cause
rotation, as explained in more detail below. As discussed above, when a current, a current trace and/or its associated magnetic field is described as traveling with a reference variable (e.g. with a reference trajectory variable xr, yr, dr), it should be understood to mean that such current, current trace and/or magnetic field varies spatially as the reference variables vary over time (e.g. the magnetic field generated by the y-current phases travel in the stator-x direction with xr — dr as reference trajectory variables xr, dr vary over time). It can be seen from equations (7) that in such embodiments, the phase shift between adjacent y-current phases i0y, ily, i2y is (in electrical angle radians) or ½ (in spatial phase). Phase-adjacent ones of y-current phases i0y, iiy, ¾ can be driven into spatially adjacent y-traces 34, such the phase difference between the y-current phases y, ijy, i2y driven into spatially adjacent y-traces 34 is
A.
- (in electrical angle radians) or - (in spatial phase). In such embodiments, y-traces 34 in stator 30 can be designed to have a stator-y coil trace pitch Pcy = - = -f-
[0177] This technique for generating y-current phases ijy can be generalized for a different number mp of effective y-current phases, where mp is an integer greater than 1. A set of multiphase sinusoidal y-current phases ¾, to produce a magnetic field wave that travels with xr — dr in the stator-x direction is given by: ijy = Ay sin {^-^- 2π - j - + <py (8a) where: j is an integer phase index which varies from 0 to mp-\ , mp is the number of effective phases and the other variables in equation (8a) have the same meanings as those of equation (7). It can be seen from equation (8a) that in such embodiments, the phase shift between adjacent current phases ijy takes the general form = (in spatial phase) or (in electrical angle radians). Phase- adjacent ones of current phases ijy can be driven into spatially adjacent y-traces 34, such the phase difference between the current phases driven into spatially adjacent y-traces 34 is = (in spatial phase) or (in electrical angle radians). In such embodiments, y-traces 34 in stator 30 can be designed to have a stator-y coil trace pitch Pcy = = Furthermore, the current phases ijy of equation (8a) can be generalized to comprise any periodic function G(xr-dr) (rather than being merely sinusoidal) that is periodic with xr-dr with a stator-x direction period λ2=λΛ, where adjacent current phases
ijy in spatially adjacent y-traces are out of phase with one another by a spatial phase difference -^2- =
2πΐρ 2πΐρ
[0178] The bottom portion of Figure 20A shows the generation of three y-current phases ioy, iiy, hy which vary with xr + dr in the stator-x direction according to:
i0y = AySin^ ^- 2π + <py) (9a) ily = AySin(—^— 2π - - + <py)
(9b)
i2y = AySin^-^- ln - + <py) (9c) where the parameters of equations (9) have the same meanings as those of equations (7). However, it can be seen from equations (9) that the currents by the bottom portion of Figure 20A generate magnetic fields which travel with xr + dr in the stator-x direction. For the general case with mp effective y-current phases, equation (9) may be generalized to:
Vdr . π \
Av sin — 2n - j— + <py
,2 J mp )
(10a)
where the parameters of equation (10) have the same meanings as those of equation (8a). However, it can be seen from equations (10) that the currents generated by the bottom portion of Figure 20A generate magnetic fields which travel with xr + dr in the stator-x direction. It can be seen from equation (10a) that in such embodiments, the phase shift between adjacent current phases ijy takes the general form = (in spatial phase) or (in electrical angle radians). Phase-adjacent ones of current phases ¾, can be driven into spatially adjacent y-traces 34, such that the phase difference between the current phases driven into spatially adjacent y-traces 34 is = (in spatial phase) or -^- (in electrical angle radians). In such embodiments, y-traces 34 in stator 30 can be designed to have a stator-y coil trace pitch
Pcy = -^2- = Furthermore, the current phases ¾, of equation (10a) can be generalized to comprise any periodic function G(xr+dr) (rather than being merely sinusoidal) that is periodic with xr+dr with a stator-x direction period λ2=λΛ, where adjacent current phases ijy in spatially adjacent y-traces are out of phase with one another by a spatial phase difference -^2- =
2m.p 2m.p
[0179] While current phases ijy may generally have any waveform that is a spatially periodic function of xr-dr (in the top portion of Figure 20A) or xr+dr (in the bottom portion of Figure 20 A), sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution. Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like. Y-current phases ijy that generate magnetic fields that travel with xr+dr may be referred to herein collectively as second positive rotational currents and individually as second positive rotational current phases. Conversely, y-current phases ijy that generate magnetic fields that travel with xr-dr may be referred to herein collectively as second negative rotational currents and individually as second negative rotational current phases.
[0180] In moveable stage rotating process, when xr is fixed or no translation motion in the stator-x direction is commanded, the two types of y-current phases ijy and corresponding magnetic field traveling waves generated by the top and bottom portions of Figure 20A will travel in two opposite directions along the stator-x axis. For example, when dr is ramping up positively (increase with time at a positive rate), the y-current phases ijy and corresponding magnetic field traveling waves generated by top part of Figure 20A will travel in the negative stator-x direction and the y-current phases ijy and corresponding magnetic field traveling waves generated by the bottom part of Figure 20A will travel in the positive stator-x direction.
[0181] In an analogous manner, the top portion of Figure 20B shows the generation of three x-current phases x, ijx, i2% which vary with yr — dr in the stator-y direction which, for the general case with np effective x-current phases, may be generalized to:
where Ax is an amplitude (assumed, in the illustrated embodiment, to be the same for all of the x-current phases ijy), λι=λγ is a spatial period in the stator-y direction, ψχ is a phase offset, k is an integer phase index which varies from 0 to np-\, np is the number of effective phases, yr is a reference stator-y trajectory and dr is a differential reference quantity used to cause rotation, as explained in more detail below. As was the case with the y-current phases discussed above, the current phases hx of equation (11) can be generalized to comprise any
periodic function F(yr-dr) (rather than being merely sinusoidal) that is periodic with yr-dr with a stator-y direction period λ^λ,,, where adjacent current phases ikx in spatially adjacent x- traces are out of phase with one another by a spatial phase difference— =— . The bottom
2rip 2rip
portion of Figure 20B shows the generation of three x-current phases x, iix, i2x which vary with yr + dr in the stator-y direction which, for the general case with np effective x-current phases,
where the parameters of equation (12) have the same meanings as those of equation (11). As was the case with the y-current phases discussed above, the current phases ¾ of equation (12) can be generalized to comprise any periodic function F(yr+dr) (rather than being merely sinusoidal) that is periodic with yr+dr with a stator-y direction period λ^λ,,, where adjacent current phases in spatially adjacent x- traces are out of phase with one another by a spatial phase difference— =— . It can be seen from equations (11) and (12) that in such embodiments, the phase shift between adjacent x-current phases ikx takes the general form
= (in spatial phase) or (in electrical angle radians). Phase-adjacent ones of x- current phases ikx can be driven into spatially adjacent x-traces 32, such the phase difference between the current phases driven into spatially adjacent x-traces 32 is— =— (spatial phase) or— (in radians). In such embodiments, x-traces 32 in stator 30 can be designed to
rip
have a stator-x coil trace pitch Pcx =— =— .
1 L JL 2np 2np
[0182] While current phases ikx may generally have any waveform that is a spatially periodic function of yr-dr (in the top portion of Figure 20B) or yr+dr (in the bottom portion of Figure
20B), sinusoidal waveforms are currently preferred due to many advantageous features such as energy efficiency, compact trace layout, simplification of power electronics design, smooth motion and fine motion resolution. Other types of trajectory-dependent periodic waveform can also be used to drive multi-phase coils traces, such as square wave, triangle waves, trapezoidal waves and/or the like. X-current phases ikx that generate magnetic fields that travel with yr+dr may be referred to herein collectively as first positive rotational currents and individually as first positive rotational current phases. Conversely, x-current
phases ¾ that generate magnetic fields that travel with yr-dr may be referred to herein collectively as first negative rotational currents and individually as first negative rotational current phases. Furthermore, it should be appreciated that the differential variable dr described above in connection with equation (7)-(12) and in the description of the embodiments in Figures 20A and 20B may be the same variable; in general, however, the differential variable dr used in the embodiment of Figure 20A (equations (7)-(10)) may be different than, and independent from, the differential variable dr used in the embodiment of Figure 20B (equations (11)-(12)).
[0183] In moveable stage rotating process, when yr is fixed or no translation motion in the stator-y direction is commanded, the two types of x-current phases ikx and corresponding magnetic field traveling waves generated by the top and bottom portions of Figure 20B will move in two opposite directions along the stator-y axis. For example, when dr is ramping up positively (increasing with time at a positive rate), the x-current phases ¾ and corresponding magnetic field traveling waves generated by top part of Figure 20B will travel in the negative stator-y direction and the x-current phases ikx and corresponding magnetic field traveling waves generated by the bottom part of Figure 20B will travel in the positive stator-y direction.
[0184] Figure 21 A shows one non-limiting example of magnet array assembly 716 which may be used for controllable 360° rotation according to a particular embodiment. Magnet array assembly 716 comprises four ID magnet arrays 712A-712D. Magnet arrays 712B, 712D are linearly elongated in stage-y direction, and magnet array 712A, 712C are linearly elongated in stage-x direction. Each magnet array 712 comprises a plurality of linearly elongated magnetization segments 714 with corresponding magnetization directions generally orthogonal to its elongation direction. Each ID magnet array has a stage-x dimension of 1λ and a stage-y dimension of 1λ, where it is assumed (for each of explanation and without loss of generality) that λΙ=λγ=λ2=λχ=λ. Generally, any ID magnet array assembly 16 described herein can be used for the controllable 360° rotation operation, by applying the operational methods and control algorithms described herein with appropriate modification where desired. Magnet array assemblies having the 90° rotational symmetric property (about a z- oriented axis (e.g. axis 771 at the center stage-x-stage-y center of magnet array assembly 16 and/or moveable stage 10)) are currently preferred.
[0185] Figures 21B-2 IK illustrate possible coil traces 732, 734 and corresponding current phases driven therein to operate the Figure 21A magnet array assembly 716 to achieve controllable rotation. Figure 21B shows a top view of a displacement device 750 including a moveable stage 710 comprising the Figure 21A magnet array assembly 716 which is moveable relative to a stator 730 comprising coil assembly 735. A stator-z oriented axis 771 extends through the stage-x-stage-y center 771A of moveable stage 710 and/or magnet array assembly 716 and coincides with a notional dividing plane CC, which extends in the stator-y and stator-z directions. Inside stator coil assembly 735, there are first and second pluralities (i.e. first and second groups) of y-traces 734 that are elongated in the stator-y direction: traces 734- (shown in solid lines) and traces 734+ (shown in broken lines), where traces 734- represent the y-traces located on the negative stator-x side of a boundary that coincides with dividing plane CC and traces 734+ represent the y-traces located on the positive stator-x side of the boundary that coincides with dividing plane CC. First and second pluralities of coil traces 734+, 734- may be located on the same or different layers (e.g. at the same or different stator-z locations). Coil traces 734+ are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr (i.e. coil traces 734+ are driven with second positive rotational current phases) and coil traces 734- are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr (i.e. coil traces 734- are driven with second negative rotational current phases). In practice, the first and second pluralities of y-current phases ijy can be driven into y-traces 734 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of y-current phases ijy can be independently driven into two pluralities of y-traces 734 inside one excitation region 43. During the rotation process, xr may be fixed or there may be no commanded translation motion along the stator-x axis. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 734- and those generated by the current phases driven in traces 734+) will move in opposite directions. When dr is positively ramping up (i.e. increasing its value with time), the magnetic field traveling wave generated by current phases driven in coil traces 734+ will travel in the positive stator-x direction and this wave will pull ID magnet array 712D in the positive stator-x direction; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 734- will travel in the negative stator-x
direction and this wave will pull ID magnet array 712B in the negative stator-x direction. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction as shown in Figure 21C. For example, when dr increases by λ, magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 816 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0186] Figure 21D illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using x-current phases ikx driven into first and second pluralities (i.e. first and second groups) of x-traces 732+, 732-. First and second pluralities of x-traces 732+, 732- may be located on the same or different layers (e.g. at the same or different stator-z locations). The Figure 21D illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 771 at the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710). Inside stator coil assembly 735, there are first plurality 732- and second plurality 732+ of x-traces 732 that are elongated in the stator-x direction, where traces 732- represent the x-traces located on the negative stator-y side of a boundary that coincides with dividing plane DD and traces 732+ represent the x-traces located on the positive stator-y side of the boundary that coincides with dividing plane DD. Coil traces 732+ are driven with x- current phases (and generate corresponding magnetic fields) which travel with yr+dr (i.e. coil traces 732+ are driven with first positive rotational current phases) and coil traces 732- are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with yr-dr (i.e. coil traces 732- are driven with first negative rotational current phases). In practice, first and second pluralities of x-current phases ikx can be driven into x-traces 732 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases ikx can be independently driven into two pluralities (i.e. groups) of x-traces 732 inside one excitation region 43. During the rotation process, yr may be fixed or there may be no commanded
translation motion along the stator-y axis. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 732- and those generated by the current phases driven in traces 732+) will move in opposite directions. When dr is positively ramping up (i.e. increasing its value with time), the magnetic field traveling wave generated by current phases driven in coil traces 732+ will travel in the positive stator-y direction and this wave will pull ID magnet array 712A in the positive stator-y direction; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 732- will travel in the negative stator-y direction and this wave will pull ID magnet array 712C in the negative stator-y direction. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when dr increases by λ, magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0187] Figure 21 E illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using x-current phases * driven into first and second pluralities of x-traces 732+', 732-'. First and second pluralities of x-traces 732+', 732-' may be located on the same or different layers (e.g. at the same or different stator-z locations). The Figure 21E illustration shows a notional dividing plane CC which extends in the stator-y and stator-z directions and coincides with stator-z oriented axis 771 in the stage- x-stage-y center 771A of magnet array 716 and/or moveable stage 710. Inside stator coil assembly 735 of the Figure 21E embodiment, there are first plurality 732-' and second plurality 732+' of x-traces 732 that are elongated in the stator-x direction, where traces 732-' represent x-traces located on the negative stator-x side of a boundary that coincides with dividing plane CC and traces 732+' represent x-traces located on the positive stator-x side of the boundary that coincides with dividing plane CC. Coil traces 732+' are driven with x- current phases 4* (and generate corresponding magnetic fields) which travel with yr+dr (i.e. coil traces 732+' are driven by first positive rotational current phases) and coil traces 732-' are
driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with yr-dr (i.e. coil traces 732-' are driven by first negative rotational current phases). In practice, first and second pluralities of x-current phases ikx can be independently driven into x- traces 732 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases ikX can be independently driven into two pluralities (i.e. groups) of x-traces 732 inside one excitation region 43. During the rotation process, yr is not necessarily fixed in which case the techniques illustrated in Figure 2 IE permit moveable stage 710 to achieve simultaneous stator-y oriented translation and rotation about central stator-z oriented axis 771. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 732-' and those generated by the current phases driven in traces 732+') will move with different characteristics: one moves ahead of yr by a distance dr and the other moves behind yr by a distance dr. When dr is positively ramping up (i.e. increasing its value with time), the magnetic field traveling wave generated by current phases driven in coil traces 732+' will pull ID magnet array 712A in the positive stator-y direction relative to stage-x-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 732-' will pull ID magnet array 712C in the negative stator-y direction relative to stage-x-stage-y center 771 A of magnet arrays 716 and/or moveable stage 710. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when dr increases by λ, magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0188] Figure 21F illustrates a method of controllably rotating magnet array assembly 716 and its corresponding moveable stage 710 using y-current phases ijy driven into first and second pluralities of y-traces 734+', 734-'. First and second pluralities of y-traces 734+', 734-' may be located on the same or different layers (e.g. at the same or different stator-z
locations). The Figure 21F illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771A of magnet array 716 and/or moveable stage 710. Inside stator coil assembly 735 of the Figure 21F embodiment, there are first plurality 734-' and second plurality 734+' of y-traces 734 that are elongated in the stator-y direction, where traces 734-' represent y-traces located on the positive stator-y side of a boundary which coincides with dividing plane DD and traces 734+' represent y-traces located on the negative stator-y side of the boundary which coincides with dividing plane DD. Coil traces 734+' are driven with y- current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr (i.e. coil traces 734+' are driven by second positive rotational current phases) and coil traces 734-' are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr (i.e. coil traces 734-' are driven by second negative rotational current phases). In practice, first and second pluralities of y-current phases ¾, can be independently driven into y- traces 734 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of y-current phases ijy can be independently driven into two pluralities (i.e. groups) of y-traces 734 inside one excitation region 43. During the rotation process, xr is not necessarily fixed in which case the techniques illustrated in Figure 2 IF permit moveable stage 710 to achieve simultaneous stator-x oriented translation and rotation about stator-z oriented axis 771. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 734-' and those generated by the current phases driven in traces 734+') will move with different characteristics: one moves ahead of xr by a distance dr and the other moves behind xr by a distance dr. When dr is positively ramping up (i.e. increasing its value with time), the magnetic field traveling wave generated by current phases driven in coil traces 734+' will pull ID magnet array 712D in the positive stator-x direction relative to the stage-z-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710; at the same time, the magnetic field traveling wave generated by current phases driven in coil traces 734-' will pull ID magnet array 712B in the negative stator-x direction relative to the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when dr increases by λ, magnet array assembly 716 will rotate around
the stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0189] As shown in Figure 21 G, some embodiments comprise combining the techniques shown in Figures 21B and 21E by driving x-current phases ¾ in traces 732-', 732+' and y- current phases ijy in traces 734-, 734+ to achieve greater torque during rotation. The rotation of magnet array assembly 716 is operated along the plane CC that extends in the stator-y direction and stator-z direction. Boundary plane CC may be at the boundary between a pair of excitation regions 43A, 43B. The Figure 21G technique allows rotation of moveable stage 710 while the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710 translates along CC (i.e. in the stator-y direction).
[0190] As shown in Figure 21H, some embodiments comprise combining the techniques shown in Figures 21D and 21F by driving y-current phases ijy in traces 734-', 734+' and x- current phases in traces 732-, 732+ to achieve larger torque during rotation. The rotation of magnet array assembly 716 is operated along the plane DD that extends in the stator-x direction and stator-z direction. Boundary plane DD may be the boundary between a pair of excitation regions 43A, 43B. The Figure 21H technique allows rotation of moveable stage 710 while the stage-x-stage-y center 771A of magnet array assembly 716 and/or moveable stage 710 translates along DD (i.e. in the stator-x direction).
[0191] As shown in Figure 211, some embodiments comprise combining the techniques shown in Figures 21C and 21D by driving y-current phases ijy in traces 734-, 734+ and x- current phases in traces 732-, 732+ to achieve larger torque during rotation.
[0192] As shown in Figure 21 J, some embodiments comprise rotating magnet array assembly 716 and its corresponding moveable stage 710 at the intersection point of four independently driven current excitation regions 43A-43D. The Figure 21 J illustration shows notional dividing boundary planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of boundary planes CC and DD coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771 A of magnet array assembly
716 and/or moveable stage 710. Stator-z oriented axis 771 coincides with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D coincides with axis 771. Inside stator coil assembly 735 of the Figure 21J embodiment, x-traces 732A in excitation region 43A are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+dr, y-traces 734B in excitation region 43B are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 732C in excitation regions 43C are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr-dr and y-traces 734D in excitation region 43D are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 21J illustration, but coil traces 732A, 734B, 732C, 734D may be distributed throughout at least a portion of their respective excitation regions 43A-43D. The current phases driven into the coil traces in each of excitation regions 43 A- 43D create traveling magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in x-coil traces 732A (region 43 A) will pull ID magnet array 712A in the positive stator-y direction; the magnetic field traveling wave generated by current phases driven in y-coil traces 734B (region 43B) will pull ID magnet array 712B in the negative stator-x direction; the magnetic field traveling wave generated by current phases drive in x-coil traces 732C (region 43C) will pull ID magnet array 712C in the negative stator-y direction; and the magnetic field traveling wave generated by current phases driven in y-coil traces 734D (region 43D) will pull ID magnet array 712D in the positive stator-x direction. Consequently, magnet array assembly 716 will rotate around its central z-oriented axis 771 in a counter-clockwise direction. For example, when dr increases by λ, magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90° counter-clockwise. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around central stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0193] Figure 21 K shows another embodiment which comprises rotating magnet array assembly 716 and its corresponding moveable stage 710 at the intersection point of four independently driven current excitation regions 43A-43D. The Figure 21 K embodiment may be considered to be a combination of techniques shown in Figures 21 E and 2 IF. The Figure 21 K illustration shows notional boundary dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator-x stator-z directions and the intersection of boundary planes CC, DD coincides with the stator-z oriented axis 771 in the stage-x-stage-y center 771 A of magnet array assembly 716 and/or moveable stage 710. Stator-z oriented axis 771 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 771. Inside stator coil assembly 735 of the Figure 21 K embodiment, x-traces 732A in excitation region 43 A are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+ dr, y-traces 734A in excitation region 43A are driven with y-current phases ijy (and generate
corresponding magnetic fields) which travel with xr-dr, x-traces 732B in excitation region 43B are driven with x-current phases hx (and generate corresponding magnetic fields) which travel with yr-dr, y-traces 734B in excitation region 43B are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 732C in excitation regions 43C are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr-dr, y-traces 734C in excitation region 43C are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with Xr+dr, x-traces 732D in excitation regions 43D are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+ dr, and y-traces 734D in excitation region 43D are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 21 K illustration, but coil traces 732A-732D, 734A-734D may be distributed over corresponding layers throughout at least a portion of their respective excitation regions 43A-43D. The current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in x-coil traces 732A (region 43 A) will pull ID magnet array 712A in the positive stator-y direction; the
magnetic field traveling wave generated by current phases driven in y-coil traces 734B (region 43B) will pull ID magnet array 712B in the negative stator-x direction; the magnetic field traveling wave generated by current phases drive in x-coil traces 732C (region 43C) will pull ID magnet array 712C in the negative stator-y direction; the magnetic field traveling wave generated by current phases driven in y-coil traces 734D (region 43D) will pull ID magnet array 712D in the positive stator-x direction.
[0194] Initially, when stage 710 is in the configuration shown in Figure 2 IK, the y-current phases in traces 734A (region 43A), the x-current phases in traces 732B (region 43B), the y- current phases in traces 734C (region 43C) and the x-current phases in traces 732D (region 43D) will have minimal effect on stage 710, as their trace elongation directions are orthogonal to the elongation directions of the magnetization segments in their corresponding magnet arrays 712A, 712B, 712C, 712D. However, as stage 710 starts to rotate in the counterclockwise direction (with dr ramping upwardly): the y-current phases in traces 734A (region 43 A) will start to pull magnet array 712A in the negative stator-x direction; the x- current phases in traces 732B (region 43B) will start to pull magnet array 712B in the negative stator-y direction; the y-current phases in traces 734C (region 43C) will start to pull magnet array 712C in the positive stator-x direction; and the x-current phases in traces 732D (region 43D) will start to pull magnet array 712D in the positive stator-y direction. This will further help to rotate stage 710 about axis 771 in the counter-clockwise direction (in the Figure 21 K view). Consequently, magnet array assembly 716 will rotate counter-clockwise about its central z-oriented axis 771 in a counter-clockwise direction. For example, when dr increases by λ, magnet array assembly 716 will rotate around central stator-z oriented axis 771 by 90°. Due to its 90° rotational symmetry, magnet array assembly 716 is in the same magnetic configuration after a rotation of 90°, and thus a further increase of λ in dr will result in a further 90° rotation around stator-z oriented axis 771. By repeating this sequence, any controllable amount of rotation can be achieved. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 716 will rotate around central stator-z oriented axis 771 in a clockwise direction.
[0195] Figure 22A shows another non-limiting example of magnet array assembly 816 which may be used for controllable 360° rotation according to a particular embodiment. Comparing Figure 22A to Figure 21A, it can be seen that magnet array assembly 816 of Figure 22A is
similar to magnet array 716 of Figure 21 A, except that the relative orientation of magnet arrays 812A-812D in magnet array 816 is different than that of magnet arrays 712A-712D in magnet arrays 716. In particular, magnet array assembly 716 (Figure 21 A) is a right-handed magnet array assembly and magnet array assembly 816 (Figure 22 A) is a left-handed magnet array assembly (see descriptions of left-handed and right handed magnet array assemblies described above in connection with Figures 5 A and 5B). Like magnet arrays 712A-712D, each magnet array 812A-812D has a stage-x dimension of 1λ and a stage-y dimension of 1λ, where it is assumed (for each of explanation and without loss of generality) that
i= y= 2= x= . Generally, magnet array assembly 816 of Figure 22A can be controllably rotated by appropriate modification of the techniques described in Figures 20A, 20B and 21B-21J. Such techniques will be appreciated by those skilled in the art having regard to the teachings of this disclosure. A number of non- limiting examples of such techniques are shown in Figures 22B-22F.
[0196] As illustrated in Figure 22B, a displacement device 850 having a moveable stage 810 comprising the Figure 22A magnet array assembly 816 can be rotated about z-oriented axis 871 located at the stage-x/stage-y center 871 of magnet array 816.1n a manner analogous to Fi gure 21B described above, rotating magnet array 816 comprises driving y-current phases ijy into y-traces 834+ and into y-traces 834-. However, due to the left-handed pattern of magnet array assembly 816 (as compared to the right-handed pattern of magnet array 716), the same y-current phases ijy driven into the same y-traces (and the corresponding same magnetic field traveling waves) will result in rotation of magnet array assembly 816 (and its moveable stage 810) in opposite rotational directions than magnet array assembly 716 (and its moveable stage 710).
[0197] Figure 22C shows a current driving method modified from 21 G to accommodate the left-handed magnet array assembly 816. In Figure 22C, magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises first and second pluralities of x-traces 832-', 832+' and first and second pluralities of y-traces 834-, 834+, similar to the system described in Figure 21G. First and second pluralities of x-traces 832+, 832- may be located on the same or different layers (e.g. at the same or different stator-z locations). First and second pluralities of y-traces 834+, 834- may be located on the same or different layers (e.g. at the same or
different stator-z locations). However, for the left-handed magnet array assembly 816, the current driven into these traces is different than in Figure 21 G. More particularly, in Figure 22C, y-traces 834- are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel wit xr+dr and y-traces 834+ are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr. The x-current phases ¾ driven into coil traces 832-' and 832+' may be similar to those driven into coil traces 732-' and 732+' for the Figure 21 G described above. Using these current driving methods shown in Figure 22C, magnet array assembly 816 will rotate counter-clockwise (in the view of Figure 22C), when dr is ramping up and clockwise when dr is ramping down.
[0198] Figure 22D shows a current driving method modified from Figure 21 H to accommodate the left-handed magnet array assembly 816. In Figure 22D, magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises first and second pluralities of x- traces 832-, 832+ and first and second pluralities of y-traces 834-', 834+', similar to the system described in Figure 21H. First and second pluralities of x-traces 832+, 832- may be located on the same or different layers (e.g. at the same or different stator-z locations). First and second pluralities of y-traces 834+', 834-' may be located on the same or different layers (e.g. at the same or different stator-z locations). However, for the left-handed magnet array assembly 816, the current driven into these traces is different than in Figure 21H. More particularly, in Figure 22C, x-traces 832- are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+dr and x-traces 832+ are driven with x- current phases (and generate corresponding magnetic fields) which travel with yr-dr. The y-current phases ijy driven into coil traces 834-' and 834+' may be similar to those driven into coil traces 734-' and 734+' for the Figure 21H described above. Using these current driving methods shown in Figure 22D, magnet array assembly 816 will rotate counter-clockwise (in the view of Figure 22D), when dr is ramping up and clockwise when dr is ramping down.
[0199] Figure 22E shows a current driving method modified from Figure 21 J to
accommodate the left-handed magnet array assembly 816. In Figure 22E, magnet array assembly 816 (and its corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises four independently driven current excitation regions 43A-43D. The Figure 22E illustration shows notional dividing
planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of planes CC/DD coincides with stator-z oriented axis 871 in the stage-x-stage-y center 871 A of magnet array assembly 816 and/or moveable stage 810. Stator-z oriented axis 871 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 871. Inside stator coil assembly 835 of the Figure 22E embodiment, y-traces 834A in excitation region 43A are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 832B in excitation region 43B are driven with x-current phases hx (and generate corresponding magnetic fields) which travel with yr-dr, y-traces 834C in excitation regions 43 C are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr and x-traces 732D in excitation region 43D are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 22E illustration, but coil traces 834A, 832B, 834C, 832D may be distributed throughout at least a portion of their respective excitation regions 43A-43D. The current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in y-coil traces 834A (region 43A) will pull ID magnet array 812A in the negative stator-x direction; the magnetic field traveling wave generated by current phases driven in x- coil traces 832B (region 43B) will pull ID magnet array 812B in the negative stator-y direction; the magnetic field traveling wave generated by current phases drive in y-coil traces 834C (region 43C) will pull ID magnet array 812C in the positive stator-x direction; and the magnetic field traveling wave generated by current phases driven in x-coil traces 832D (region 43D) will pull ID magnet array 812D in the positive stator-y direction. Consequently, magnet array assembly 816 will rotate around its central z-oriented axis 871 in a counterclockwise direction. For example, when dr increases by λ, magnet array assembly 816 will rotate around the stator-z oriented axis 871 by 90°. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 816 will rotate around the stator-z oriented axis 871 in a clockwise direction.
[0200] Figure 22F shows a current driving method similar to Figure 21 K for left-handed
magnet array assembly 816. In Figure 22F, magnet array assembly 816 (and its
corresponding moveable stage 810) are rotated about axis 871 by a stator 830 comprising a coil assembly 835, which comprises four independently driven current excitation regions 43A-43D having features similar to those of Figure 22E. Inside stator coil assembly 835 of the Figure 22F embodiment, y-traces 834A in excitation region 43A are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, , x-traces 832A in excitation region 43 A are driven with x-current phases hx (and generate
corresponding magnetic fields) which travel with yr+ dr, x-traces 832B in excitation region 43B are driven with x-current phases hx (and generate corresponding magnetic fields) which travel with yr-dr, y-traces 834B in excitation region 43B are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, y-traces 834C in excitation regions 43C are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr, x-traces 832C in excitation region 43 C are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr- dr, x-traces 732D in excitation region 43D are driven with x-current phases (and generate corresponding magnetic fields) which travel with yr+dr and y-traces 834D in excitation region 43D are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 22F illustration, but coil traces 834A, 832B, 834C, 832D may be distributed throughout at least a portion of their respective excitation regions 43A-43D. The coil traces 832A-832D and 834A-834D in excitation regions 43A-43D and their corresponding drive current phases ijy are the same as coil traces 732A-732D and 734A-734D in excitation regions 43A-43D and corresponding drive current phases ijy of the Figure 21 K embodiment. As a result, when dr is positively ramping up, magnet array assembly 816 and its corresponding moveable stage 810 will rotate counter-clockwise and when dr is negatively ramping down, magnet array assembly 816 and its corresponding moveable stage 810 will rotate clockwise.
[0201] The rotation techniques and coil trace assemblies 735, 835 described in Figures 20, 21 and 22 are described with application to magnet array assemblies 716 and 816. It will be appreciated that magnet array assembly 716 has a layout similar to magnet array assembly 416 A (Figure 5 A) and that magnet array assembly 816 has a layout similar to a left-handed
version of magnet array assembly 416A (Figure 5 A). Any of the rotation techniques and coil trace assemblies 735, 835 described in Figures 20, 21 and 22 may be used with magnet array assembly 416A (or a left-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE. Figure 5B shows a left-handed magnet array assembly 416B that is different than magnet array assemblies 716 and 816 in that the individual magnet arrays of magnet array assembly 416B are offset and spaced apart from one another as described above. Regardless, any of the rotation techniques and coil trace assemblies 735, 835 described in Figures 20, 21 and 22 may be used with magnet array assembly 416B (or a right-handed version thereof) and such magnet array assemblies may comprise any of the individual magnet arrays described in Figures 6A-6EE, by applying the operational methods and control algorithms described herein with appropriate modification.
360° Rotation Control Methods for 2D magnet array assembly
[0202] In some embodiments, moveable stages 10 comprising 2D magnet array assemblies 16 (e.g. magnet array assemblies 16 of the type shown in Figures 4A, 4B, 4D) may be capable of fully controllable 360° rotation about a stator-z oriented axis using current phases driven into coil traces having any two or more directions (e.g. x-current phases ¾ driven into x-traces 32 and y-current phases ijy driven into y-traces 34). Such x-current phases ¾ and y- current phases ijy could be similar to, and have any of the characteristics of, the current phases described above which vary with yr±dr and xr±dr - see Figures 20A, 20B and the
corresponding description and generalizations discussed above. Figure 23A shows one non- limiting example of magnet array assembly 916 comprising a magnet array 912 which may be used for controllable 360° rotation according to a particular embodiment. Magnet array assembly 916 and magnet array 912 of the Figure 23 A embodiment comprise a plurality of sub-arrays 921. By way of non- limiting example, as shown by dashed lines in Figure 23 A, each of sub-arrays 921 A, 921B, 921C, 921D may be similar to sub-array 321 of the embodiment shown in Figure 4D. In some embodiments, each of sub- arrays 921 of magnet array assembly 916 may be similar to any of the other 2D sub-arrays 21 described herein. Generally, any 2D magnet array assembly 16 described herein can be used for the controllable 360° rotation operation, by applying the operational methods and control
algorithms described herein with appropriate modification where desired. Magnet array assemblies 916 with 90° rotational symmetric property (about a z-oriented axis (e.g. axis 971)) are currently preferred.
[0203] Magnet array assembly 916 of the Figure 23 A embodiment comprises a stage-x direction dimension of 2λχ and a stage-y direction dimension of 2 y. In the Figure 23A embodiment, λχ=λγ=λ without loss of generality. Generally, the stage-x and stage-y direction dimensions of magnet array assembly 916 may comprise any positive integer number of its magnetic spatial period λ and magnet array assembly 916 may comprise any positive integer number of sub-arrays 921. The magnetization directions of each magnetization segment in the Figure 23A illustration are shown with the conventional field direction annotations. In some embodiments, the magnetization directions of each of the magnetization segments in the Figure 23 A sub-arrays 921 could be reversed (i.e. have its magnetization direction changed by 180° for each magnetization segment).
[0204] Figures 23B-23F illustrate possible coil traces 932, 934 and corresponding current phases ikx, ijy driven therein to operate the Figure 23 A magnet array assembly 916 to achieve controllable rotation. Figure 23B shows a top view of a displacement device 950 including a moveable stage 910 comprising the Figure 23 A magnet array assembly 916 which is moveable relative to a stator 930 comprising coil assembly 935. A stator-z oriented axis 971 extends through the stage-x-stagey center 971 A of magnet array assembly 916 and/or moveable stage 910 and coincides with a notional dividing plane CC, which extends in the stator-y and stator-z directions. Inside stator coil assembly 935, there are first plurality 932- and second plurality 932+ of x-traces 932 that are elongated in the stator-x direction, where traces 932- represent the x-traces located on the negative stator-x side of dividing plane CC and traces 932+ represent the x-traces located on the positive stator-x side of dividing plane CC. Coil traces 932+ are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with yr+dr and coil traces 932- are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with yr-dr. In practice, first and second pluralities of x-current phases ikx can be independently driven into x-traces 932 of two excitation regions 43 with dividing plane CC as a boundary of two excitation regions 43. Additionally or alternatively, first and second pluralities of x-current phases ikx can be independently driven into two pluralities (i.e. groups) of x-traces 932 inside one excitation
region 43. During the rotation process, yr is not necessarily fixed in which case the techniques illustrated in Figure 23B permit moveable stage 910 to achieve simultaneous stator-y oriented translation and rotation about central stator-z oriented axis 971. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 932- and those generated by the current phases driven in traces 932+) will move with different characteristics: one moves ahead of yr by a distance dr and the other moves behind yr by a distance dr. When dr is positively ramping up (increasing its value with time), the magnetic field traveling wave generated by current driven in coil traces 932+ will tend to pull the portion of magnet array 912 that is on the positive stage-x side of plane CC toward the positive stator-y direction relative to the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910; at the same time the magnetic field traveling wave generated by current driven in coil traces 932- will pull the portion of magnet array 912 that is on the negative stage-x side of plane CC toward the negative stator-y direction relative to stage-x-stage-y center 971 A of magnet array assembly 916. Consequently, magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a counter-clockwise direction. If dr is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
[0205] Figure 23C illustrates a method of controllably rotating magnet array assembly 916 and its corresponding moveable stage 910 using y-current phases ijy driven into first and second pluralities of y-traces 934+, 934-. The Figure 23C illustration shows a notional dividing plane DD which extends in the stator-x and stator-z directions and coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable sage 910. Inside stator coil assembly 935, there are first plurality 934- and second plurality 934+ of y-traces 934 that are elongated in the stator-y direction, where traces 934+ represent the y-traces located on the negative stator-y side of dividing plane DD and traces 934- represent the y-traces located on the positive stator-y side of dividing plane DD. Coil traces 934+ are driven with y-current phases ¾ (and generate corresponding magnetic fields) which travel with xr+dr and coil traces 934- are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr. In practice, first and second pluralities of y-current phases ijy can be independently driven into y-traces 934 of two excitation regions 43 with dividing plane DD as a boundary of two excitation regions 43.
Additionally or alternatively, first and second pluralities of y-current phases iky can be independently driven into two pluralities (i.e. groups) of y-traces 934 inside one excitation region 43. During the rotation process, xr is not necessarily fixed in which case the techniques illustrated in Figure 23C permit moveable stage 910 to achieve simultaneous stator-x oriented translation and rotation about central stator-z oriented axis 971. The two types of traveling magnetic field waves (i.e. those generated by the current phases driven in traces 934- and those generated by the current phases driven in traces 934+) will move with different characteristics: one moves ahead of xr by a distance dr and the other moves behind xr by a distance dr. When dr is positively ramping up (increasing its value with time), the magnetic field traveling wave generated by current driven in coil traces 934+ will tend to pull the portion of magnet array assembly 916 that is on the negative stage-y side of plane DD toward the positive stator-x direction relative to the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910; at the same time the magnetic field traveling wave generated by current driven in coil traces 934- will tend to pull the portion of magnet array assembly 916 that is on the positive stage-y side of plane DD toward the negative stator-x direction relative to stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910. Consequently, magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a counter-clockwise direction. If dr is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around central stator- z oriented axis 971 in a clockwise direction.
[0206] As shown in Figure 23D, some embodiments comprise rotating magnet array assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D. The Figure 23D illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator- x/stator-z directions and the intersection of panes CC/DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971A of magnet array assembly 916 and/or moveable stage 910. Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 971. Inside stator coil assembly 935 of the Figure 23D embodiment, x-traces 932A in excitation region 43A are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+ dr, y-traces 934B in excitation region 43B are driven with y-current phases ijy
(and generate corresponding magnetic fields) which travel with xr-dr, x-traces 932C in excitation regions 43C are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr-dr and y-traces 934D in excitation region 43D are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 23D illustration, but coil traces 932A, 934B, 932C, 934D may be distributed throughout at least a portion of their respective excitation regions 43A-43D. The current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in x-coil traces 932A (region 43 A) will pull the portion of magnet array assembly 916 located on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the positive stator-y direction; the magnetic field traveling wave generated by current phases driven in y-coil traces 934B (region 43B) will pull the portion of magnet array assembly 916 located on the negative stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-x direction; the magnetic field traveling wave generated by current phases driven in x-coil traces 932C (region 43C) will pull the portion of magnet array assembly 916 located on the negative stage-x side of plane CC and the negative stage-y side of plane DD in the negative stator-y direction; and the magnetic field traveling wave generated by current phases driven in y-coil traces 934D (region 43D) will pull the portion of magnet array assembly 916 located on the positive stage-x side of plane CC and the negative stage-y side of plane DD in the positive stator-x direction. Consequently, magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If dr is negatively ramping (decreasing its value with time), magnet array assembly 916 will rotate around the stator-z oriented axis 971 in a clockwise direction.
[0207] Like Figure 23D, Figure 23E shows another technique for rotating magnet array assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D. The Figure 23E illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator- x/stator-z directions and the intersection of planes CC, DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971A of magnet array assembly 916 and/or
moveable stage 910. Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 971. Inside stator coil assembly 935 of the Figure 23E embodiment, y-traces 934A in excitation region 43A are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 932B in excitation region 43B are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr- dr, y-traces 934C in excitation regions 43C are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr and x-traces 932D in excitation region 43D are driven with x-current phases ikx (and generate corresponding magnetic fields) which travel with yr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 23E illustration, but coil traces 934A, 932B, 934C, 932D may be distributed throughout at least a portion of their respective excitation regions 43A-43D. The current phases driven into the coil traces in each of excitation regions 43 A- 43D create magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in y-coil traces 934A (region 43A) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and on the positive stage-y side of plane DD in the negative stator-x direction; the magnetic field traveling wave generated by current phases driven in x-coil traces 932B (region 43B) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and on the positive stage-y side of plane DD in the negative stator-y direction; the magnetic field traveling wave generated by current phases drive in y-coil traces 934C (region 43C) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and on the negative stage-y side of plane DD in the positive stator-x direction; and the magnetic field traveling wave generated by current phases driven in x-coil traces 932D (region 43D) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and on the negative stage-y side of plane DD in the positive stator-y direction. Consequently, magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
[0208] Figure 23F shows another embodiment which comprises rotating magnet array
assembly 916 and its corresponding moveable stage 910 at the intersection point of four independently driven current excitation regions 43A-43D. The Figure 23F embodiment may be considered to be a combination of techniques shown in Figures 23D and 23E. The Figure 23F illustration shows notional dividing planes CC, DD which respectively extend in the stator-y/stator-z and stator-x/stator-z directions and the intersection of the planes CC, DD coincides with the stator-z oriented axis 971 in the stage-x-stage-y center 971 A of magnet array assembly 916 and/or moveable stage 910. Stator-z oriented axis 971 is coincident with the intersection of excitation regions 43A-43D - i.e. a corner of each of excitation regions 43A-43D is located at axis 971. Inside stator coil assembly 935 of the Figure 23F
embodiment, x-traces 932A in excitation region 43A are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+ dr, y-traces 934A in excitation region 43A are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 932B in excitation region 43B are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr-dr, y-traces 934B in excitation region 43B are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr-dr, x-traces 932C in excitation regions 43C are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr- dr, y-traces 934C in excitation region 43C are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr, x-traces 932D in excitation regions 43D are driven with x-current phases ¾ (and generate corresponding magnetic fields) which travel with yr+ dr, and y-traces 934D in excitation region 43D are driven with y-current phases ijy (and generate corresponding magnetic fields) which travel with xr+dr. For the sake of drawing clarity, only partial coil traces are shown in excitation regions 43A-43D of the Figure 23F illustration, but coil traces 932A-932D, 934A-934D may be distributed over corresponding layers throughout at least a portion of their respective excitation regions 43 A- 43D. The current phases driven into the coil traces in each of excitation regions 43A-43D create traveling magnetic field waves that move in different directions. When dr is positively ramping up (i.e. increasing its value with time): the magnetic field traveling wave generated by current phases driven in x-coil traces 932 A (region 43 A) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the positive stator-y direction and the magnetic field traveling wave generated by
current phases driven in y-coil traces 934A (region 43A) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-x direction; the magnetic field traveling wave generated by current phases driven in x-coil traces 932B (region 43B) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-y direction and the magnetic field traveling wave generated by current phases driven in y-coil traces 934B (region 43B) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and the positive stage-y side of plane DD in the negative stator-x direction; the magnetic field traveling wave generated by current phases drive in x-coil traces 932C (region 43C) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and the negative stage-y side of plane DD in the negative stator-y direction and the magnetic field traveling wave generated by current phases driven in y-coil traces 934C (region 43C) will pull the portion of magnet array assembly 916 on the negative stage-x side of plane CC and the negative stage-y side of plane DD in the positive stator-x direction; and the magnetic wave generated by current phases driven in x-coil traces 932D (region 43D) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the negative stage-y side of plane DD in the positive stator-y direction and the magnetic field traveling wave generated by current phases driven in y-coil traces 934D (region 43D) will pull the portion of magnet array assembly 916 on the positive stage-x side of plane CC and the negative stage-y side of plane DD in the positive stator-x direction. Consequently, magnet array assembly 916 will rotate around its central z-oriented axis 971 in a counter-clockwise direction. If dr is negatively ramping (i.e. decreasing its value with time), magnet array assembly 916 will rotate around central stator-z oriented axis 971 in a clockwise direction.
Application in in-vitro diagnostics
[0209] Referring back to the Figure 3 embodiment, displacement device 150 of the Figure 3 embodiment may be used for a particular application, wherein part holder 119 carries a glass or plastic tube 119 A, which may contain biological samples 119B, for example. Moveable stage 110 may, for example, carry biological samples 119B to travel between different biological sample analyzers for biological content analysis.
[0210] Figure 24 depicts another exemplary embodiment showing a displacement device 1050 of any of the types described herein used for another particular application. On stator 1030, there are many moveable stages 1010. Each moveable stage 1010 may carry a particular biological sample. Samples can be sent to different analyzers 1075 based on user input, such as a doctor's recommendation. As each sample may require different analysis, the moving path of each moveable stage 1010 is not necessarily the same. Moveable stages 1010 may carry samples in or out of an analyzer 1075. A moveable stage 1010 may carry samples and have a full 360° controllable rotation so that, for example, a sample label on tube 119A (Figure 3) can be scanned (e.g. by a barcode reader, a RFID reader and/or the like) to verify its identification. Arrows in Figure 24 show possible motion directions of each moveable stage 1010. The flexibility of moving in the stator-x and stator-y directions and rotating around a stator-z direction axis of this displacement devices make it very suitable for many applications, such as this application.
[0211] Certain implementations of the invention comprise controllers, computers and/or computer processors which execute software instructions which cause the controllers, computers and/or processors to perform a method of the invention. For example, one or more processors in a controller or computer may implement data processing steps in the methods described herein by executing software instructions retrieved from a program memory accessible to the processors. The invention may also be provided in the form of a program product. The program product may comprise any medium which carries a set of computer- readable signals comprising instructions which, when executed by a data processor, cause the data processor to execute a method of the invention. Program products according to the invention may be in any of a wide variety of forms. The program product may comprise, for example, physical (non-transitory) media such as magnetic data storage media including floppy diskettes, hard disk drives, optical data storage media including CD ROMs, DVDs, electronic data storage media including ROMs, flash RAM, or the like. The instructions may be present on the program product in encrypted and/or compressed formats.
[0212] Where a component (e.g. a software module, controller, processor, assembly, device, component, circuit, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a "means") should be interpreted as including as
equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.
[0213] While a number of exemplary aspects and embodiments are discussed herein, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. For example:
• In some embodiments, a combination of skewed coil traces and slanted magnet arrays may also be usefully implemented to eliminate internal stresses in the magnetic arrays while reducing or minimizing the effects of the interaction of current carrying coil traces with higher order harmonics of the magnetic fields of the magnet arrays.
• Coil traces may be fabricated using techniques other than PCB technology. Any
conductor that is or may be shaped to be generally linearly elongated may be used to provide coil traces.
• In this description and the accompanying claims, elements are said to overlap one another in or along a direction. When it is described that two or more objects overlap in or along the Z-direction, this usage should be understood to mean that a Z-direction-oriented line could be drawn to intersect the two or more objects.
• In the embodiments described herein the stator and stage bearing surfaces are generally flat (e.g. planar). This is not necessary. In some embodiments, the stator and stage bearing surfaces may comprise complementarily curved surfaces. In the case of curved bearing surfaces, the stage-z and stator-z may be understood to be oriented parallel to the direction of the normal of such curved bearing surfaces.
• In some instances, this description and the accompanying claims use the term generally to describe directions, orientations, shapes, relationships (e.g. equalities) and/or the like. For example, a coil trace may be generally elongated in a stator-x direction or a surface may be generally planar. Such directions, orientations, shapes, relationships and/or the like should be considered to accommodate the specified directions, orientations, shapes, relationships and/or the like and/or relatively small deviations (from an operational or engineering perspective) from the specified directions, orientations, shapes, relationships and/or the like.
[0214] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
Claims
WHAT IS CLAIMED IS:
1. A displacement device comprising:
a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the currents driven by the one or more amplifiers and to thereby cause the moveable stage to track a desired position, (xr,yr), within the working region, where xr is a desired position of the moveable stage in the stator-x direction in the working region and yr is a desired position of the moveable stage in the stator-y direction in the working region;
wherein:
the controller is configured to control the currents driven by the one or more amplifiers to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces; the first currents, ix, comprise a plurality of first current phases, each first
current phase, ikx, driven into a corresponding one of the at least some of the first plurality of coil traces and phase- adjacent first current phases driven into spatially adjacent ones of the at least some of the first plurality of coil traces, where:
k is an integer from 0 to np-\ representing a first phase index; and np is a number greater than or equal to two of different effective phases in the first currents, ix;
each first current phase, ikx, is determined based on a function F(yr), where F(yr) is a spatially periodic function of yr in the stator-y direction over the working region, with a first spatial period, λΰ
each first current phase, ikx, in a particular one of the at least some of the first plurality of coil traces is out of phase, as a function of yr, with one or more phase- adjacent first current phases in one or more spatially adjacent ones of the at least some of the first plurality of coil traces by a first spatial phase difference— ;
2np
the second currents, iy, comprise a plurality of second current phases, ijy, each second current phase, ijy, driven into a corresponding one of the at least some of the second plurality of coil traces and phase-adjacent second current phases driven into spatially adjacent ones of the at least some of the second plurality of coil traces, where:
j is an integer from 0 to mp-\ representing a second phase index; and mp is a number greater than or equal to two of different effective phases in the second currents, iy;
each second current phase, ijy, is determined based on a function G(xr), where G(xr) is a spatially periodic function of xr in the stator-x direction over the working region, with a second spatial period, λ2; and
each second current phase, ijy, in a particular one of the at least some of the second plurality of coil traces is out of phase, as a function of xr, with one or more phase-adjacent second current phases in one or more spatially adjacent ones of the at least some of the second plurality of coil traces by a second spatial phase difference
2. A displacement device according to claim 1 or any other claim herein wherein F(yr) and G(Xr) are each sinusoidal functions.
3. A displacement device according to any of claims 1 and 2 or any other claim herein wherein the controller is configured to determine each first current phase, ikx, according to ikx = Akx sin ( - 2π— k— + φχ 1 where, Akx is an amplitude of the kth
\λ1 rip
first current phase, ikx, and φχ is an arbitrary phase offset, and to determine each second current phase, ijy, according to i;y = Ajy sin (^- 2π— j -^- + <py where, Ajy is an amplitude of the second current phase, ijy, and cpy is an arbitrary phase offset.
4. A displacement device according to claim 3 or any other claim herein wherein the amplitude Akx=Ax and the amplitude Ax is the same for each of the first current phases and wherein the amplitude Ayj=Ay and the amplitude Ay is the same for each of the second current phases.
5. A displacement device according to any one of claims 1 to 4 or any other claim herein wherein F(yr) and G(xr) are angularly periodic functions with first and second angular periods 2π corresponding to the first and second spatial periods λι and λ2 and wherein: each first current phase, ikx, in the particular one of the at least some of the first plurality of coil traces is out of phase with the one or more phase-adjacent first current phases in one or more spatially adjacent ones of the at least some of the first plurality of coil traces by a first angular phase difference— ; each second current phase, ijy, in
rip
the particular one of the at least some of the second plurality of coil traces is out of phase with the one or more phase-adjacent second current phases in one or more spatially adjacent ones of the at least some of the second plurality of coil traces by a second angular phase difference— .
mp
6. A displacement device according to any one of claims 1 to 5 or any other claim herein
wherein: F(yr) varies periodically with yr over at least a first portion of the working region such that F(yr=y0) is equal to F(yr=y0+ i) where y0 is an arbitrary position of the moveable stage in the stator-y direction inside the first portion of the working region; and G(xr) varies periodically with xr over at least a second portion of the working region such that G(xr=x0) is equal to G(xr=x0+ 2) where x0 is an arbitrary position of the moveable stage in the stator-x direction inside the second portion of the working region.
A displacement device according to any one of claims 1 to 6 or any other claim herein wherein: F(yr) varies periodically with yr over a first interior portion of the working region, the first interior portion of the working region located away from edges of the working region by a distance such that F(yr=y0) is equal to F(yr=y0+ i) where y0 is an arbitrary position of the moveable stage in the stator-y direction inside the first interior region; and G(xr) varies periodically with xr over a second interior portion of the working region, the second interior portion of the working region located away from the edges of the working region by a distance <½, such that G(xr=x0) is equal to where x0 is an arbitrary position of the moveable stage in the stator-x direction inside the second interior portion.
A displacement device according to any one of claims 1 to 7 or any other claim herein wherein: a spatial pitch, Pcx, of the first plurality of coil traces in the stator-y direction is given by— ; and a spatial pitch, Pcy, of the second plurality of coil traces in the
2rip
stator-x direction is given by .
A displacement device according to any one of claims 1 to 7 or any other claim herein wherein: a spatial pitch, Pcx, of the first plurality of coil traces in the stator-y direction is given by— , where P and Q are arbitrary positive integer numbers; and a spatial pitch, Pcy, of the second plurality of coil traces in the stator-x direction is given by—^, where R and S are arbitrary positive integer numbers.
10. A displacement device according to any one of claims 1 to 9 or any other claim herein wherein each of the plurality of first magnetization segments is linearly elongated in a stage-x direction, each first magnetization direction of each first magnetization segment is generally orthogonal to the stage-x direction and at least two of the first magnetization segments have first magnetization directions that are different from one another and wherein the first magnetization directions of the first magnetization segments exhibit the first spatial period λ1 over a stage-y direction width of the first magnet array, the stage-y direction non-parallel to the stage-x direction.
11. A displacement device according to claim 10 or any other claim herein wherein the one or more magnet arrays comprise a second magnet array, the second magnet array comprising a plurality of second magnetization segments linearly elongated in the stage-y direction, each second magnetization direction of each second magnetization segment is generally orthogonal to the stage-y direction and at least two of the second magnetization segments have second magnetization directions that are different from one another and wherein the second magnetization directions of the second magnetization segments exhibit the second spatial period λ2 over a stage-x direction width of the second magnet array.
12. A displacement device according to claim 11 or any other claim herein wherein the one or more magnet arrays comprise:
a third magnet array, the third magnet array comprising a plurality of third magnetization segments linearly elongated in the stage-x direction, each third magnetization direction of each third magnetization segment is generally orthogonal to the stage-x direction and at least two of the third magnetization segments have third magnetization directions that are different from one another and wherein the third magnetization directions of the third magnetization segments exhibit the first spatial period λ1 over a stage-y direction width of the third magnet array; and
a fourth magnet array, the fourth magnet array comprising a plurality of fourth magnetization segments linearly elongated in the stage-y direction, each fourth magnetization direction of each fourth magnetization segment is generally orthogonal
to the stage-y direction and at least two of the fourth magnetization segments have fourth magnetization directions that are different from one another and wherein the fourth magnetization directions of the fourth magnetization segments exhibit the second spatial period λ2 over a stage-x direction width of the fourth magnet array.
13. A displacement device according to any one of claims 11 to 12 or any other claim herein wherein: the stage-y direction width of the first magnet array is equal to the first spatial period λ1 such that the first magnetization directions of the first magnetization segments exhibit a single period over the stage-y direction width of the first magnet array; and the stage-x direction width of the second magnet array is equal to the second spatial period λ2 such that the second magnetization directions of the second magnetization segments exhibit a single period over the stage-x direction width of the second magnet array.
14. A displacement device according to claim 12 or any other claim herein wherein: the stage-y direction width of the first magnet array is equal to the first spatial period λ1 such that the first magnetization directions of the first magnetization segments exhibit a single period over the stage-y direction width of the first magnet array; the stage-x direction width of the second magnet array is equal to the second spatial period λ2 such that the second magnetization directions of the second magnetization segments exhibit a single period over the stage-x direction width of the second magnet array; the stage-y direction width of the third magnet array is equal to the first spatial period λ1 such that the third magnetization directions of the third magnetization segments exhibit a single period over the stage-y direction width of the third magnet array; and the stage-x direction width of the fourth magnet array is equal to the second spatial period λ2 such that the fourth magnetization directions of the fourth magnetization segments exhibit a single period over the stage-x direction width of the fourth magnet array.
15. A displacement device according to any one of claims 1 to 9 or any other claim herein wherein:
each of the plurality of first magnetization segments is linearly elongated in a stage-x direction, each first magnetization direction of each first magnetization segment is generally orthogonal to a stage-x direction and at least two of the first magnetization segments have first magnetization directions that are different from one another and wherein each first magnetization segment has a stage-y direction width λι λι
that is one of— or— , the stage-y direction non-parallel to the stage-x direction andN being a positive integer.
A displacement device according to claim 15 or any other claim herein wherein the one or more magnet arrays comprise:
a second magnet array, the second magnet array comprising a plurality of second magnetization segments linearly elongated in the stage-y direction, each second magnetization direction of each second magnetization segment is generally orthogonal to the stage-y direction and at least two of the second magnetization segments have second magnetization directions that are different from one another and wherein each second magnetization segment has a stage-x direction width that is η λ2 λ2
one of— N or— 2N ;
a third magnet array, the third magnet array comprising a plurality of third magnetization segments linearly elongated in the stage-x direction, each third magnetization direction of each third magnetization segment is generally orthogonal to the stage-x direction and at least two of the third magnetization segments have third magnetization directions that are different from one another and wherein each third magnetization segment has a stage-y direction width that is one of— or— ;
a fourth magnet array, the fourth magnet array comprising a plurality of fourth magnetization segments linearly elongated in the stage-y direction, each fourth magnetization direction of each fourth magnetization segment is generally orthogonal to the stage-y direction and at least two of the fourth magnetization segments have fourth magnetization directions that are different from one another and wherein each
\2 \2 fourth mag bnetization seg bment has a stag be-x direction width that is one of— N or— 2N .
17. A displacement device according to any one of claim 1 to 9 or any other claim herein, the first magnet array comprising one or more sub-arrays, each sub-array comprising: a central magnetization segment having a first magnetization direction; and a plurality of additional magnetization segments, each additional magnetization segment having an edge which abuts against a corresponding peripheral edge of the central magnetization segment and each additional
magnetization segment having a corresponding second magnetization direction, each corresponding second magnetization direction different from the first magnetization direction.
18. A displacement device according to claim 17 or any other claim herein wherein each sub-array has a dimension of λ2 in a stage-x direction and each sub-array has a dimension of λ1 in a stage-y direction, the stage-y direction non-parallel to the stage-x direction.
19. A displacement device according to any one of claims 17 and 18 or any other claim herein wherein the one or more sub-arrays comprise a plurality of sub-arrays, each of the plurality of sub-arrays having at least one edge that abuts against another one of the plurality of sub- arrays.
20. A displacement device according to any one of claims 17 to 19 or any other claim herein wherein each corresponding second magnetization direction is opposed to the first magnetization direction.
21. A displacement device according to any one of claims 17 to 20 or any other claim herein wherein, for each sub-array, peripheral edges of the additional magnetization segments are aligned with principal directions of the first magnet array, the principal directions corresponding to directions along which a notional linear wire carrying a constant current and extending through a notional stage-z oriented axis at a center of the stage-x-stage-y plane of the the first magnet array induces a magnetic field which generates maximum force on the moveable stage.
22. A displacement device according to any one of claims 17 to 19 or any other claim herein wherein each sub-array comprises:
a plurality of peripheral magnetization segments, each peripheral magnetization segment having an edge which abuts against a corresponding peripheral edge of a corresponding additional magnetization segment and each peripheral magnetization segment having a corresponding peripheral magnetization direction and wherein each peripheral magnetization direction of each peripheral magnetization segment is opposed to the first magnetization direction and generally orthogonal to the second magnetization direction of the additional magnetization segment against which the peripheral magnetization segment abuts.
23. A displacement device according to claim 22 or any other claim herein wherein, for each sub-array, peripheral edges of the peripheral magnetization segments are aligned with principal directions of the first magnet array, the principal directions
corresponding to directions along which a notional linear wire carrying a constant current and extending through a notional stage-z oriented axis at a center of the stage- x-stage-y plane of the the first magnet -array induces a magnetic field which generates maximum force on the moveable stage.
24. A displacement device according to any one of claims 17 to 23 or any other claim herein wherein the first spatial period λ1 is greater than or equal to a principal direction dimension of the central magnetization segment and the first spatial period λ1 is less than or equal to twice the principal direction dimension of the central magnetization segment, the principal direction corresponding to a direction along which a notional linear wire carrying a constant current and extending through a notional stage-z oriented axis at a center of the stage-x-stage-y plane of the first magnet array induces a magnetic field which generates maximum force on the moveable stage.
25. A displacement device according to any one of claims 10 to 16 and 18 to 24 or any
other claim herein wherein the stage-x direction is generally orthogonal to the stage-y direction.
26. A displacement device according to any one of claims 1 to 25 or any other claim
herein wherein the one or more magnet arrays make up a magnet array assembly and wherein the magnet array assembly is 90° rotationally symmetric with rotation about a stage-z axis located at a stage-x-stage-y center of the magnet array assembly.
27. A displacement device according to any one of claims 1 to 26 or any other claim
herein wherein the stator-x direction is generally orthogonal to the stator-y direction.
28. A displacement device according to any of claims 1 to 27 or any other claim herein wherein at least a portion of the working region overlaps the first portion of the first layer and the second portion of the second layer in the stator-z direction.
29. A displacement device according to claim 28 or any other claim herein wherein each location in the working region overlaps the at least a portion of the first layer and the at least a portion of the second layer in the stator-z direction.
30. A displacement device according to any of claims 1 to 29 or any other claim herein wherein an interaction of magnetic fields induced by first and second currents, ix, iy, and the one or more magnet arrays creates a spatial potential energy profile associated with a position of the moveable stage in the working region, the spatial potential energy profile having a spatially local minimum when the moveable stage is located at the desired position, (xr, yr).
31. A displacement device according to any of claims 3 to 4 or any other claim herein wherein the controller is configured to determine based, at least in part, on a desired acceleration of the moveable stage in the stage-y direction and to determine Ajy based, at least in part, on a desired acceleration of the moveable stage in the stage- x direction.
32. A displacement device according to claim 31 or any other claim herein wherein the controller is configured to determine the desired acceleration of the moveable stage in the stage-y direction based on an estimate of a second time derivative of the desired position yr and the desired acceleration of the moveable stage in the stage-x direction based on an estimate of a second time derivative of the desired position xr and wherein the controller is configured to determine to be positively correlated with a magnitude of the desired acceleration of the moveable stage in the stage-y direction and to determine Ajy to be positively correlated with a magnitude of the desired acceleration of the moveable stage in the stage-x direction.
33. A displacement device according to any of claims 1 to 32 or any other claim herein, wherein the controller is configured to control the one or more amplifiers to finely adjust the moveable stage in the stator-y direction when the desired position of the moveable stage in the stator-y direction, yr, remains static by creating a first impulse in the first currents, ix, the first impulse comprising increasing an amplitude of each first current phase, to a first impulse amplitude for a first temporal period, Atj, then decreasing the amplitude of each first current phase, back to a lower level after the first temporal period, At;.
34. A displacement device according to claim 33 or any other claim herein, wherein the controller is configured to control the one or more amplifiers to finely adjust the moveable stage in the stator-x direction when the desired position of the moveable stage in the stator-x direction, xr, remains static by creating a second impulse in the second currents, iy, the second impulse comprising increasing an amplitude of each second current phase, ijy, to a second impulse amplitude for a second temporal period, At2, then decreasing the amplitude of each second current phase, ijy, back a lower level after the second temporal period, At2.
35. A displacement device according to claim 34 or any other claim herein wherein a start time of the first temporal period, At^ is one of before and after a start time of the
second temporal period, At and a finish time of the first temporal period, t^ is the one of before and after a finish time of the second temporal period, At2.
36. A displacement device according to claim 35 or any other claim herein wherein the controller is configured to reduce the amplitude of each second current phase, ijy, during the first temporal period, At;, and to reduce the amplitude of each first current phase, during the second temporal period, At2.
37. A displacement device according to any of claims 1 to 36 or any other claim herein, wherein the controller is configured to control the one or more amplifiers to finely adjust the moveable stage in the stator-y direction when the desired position of the moveable stage in the stator-y direction, yr, remains static by creating a first phase impulse in the first currents, ix, the first phase impulse comprising increasing the phase of each first current phase, to a first impulse phase for a first temporal period, Atj, then decreasing the phase of each first current phase, back to a lower level after the first temporal period, Atj.
38. A displacement device according to claim 37 or any other claim herein, wherein the controller is configured to control the one or more amplifiers to finely adjust the moveable stage in the stator-x direction when the desired position of the moveable stage in the stator-x direction, xr, remains static by creating a second phase impulse in the second currents, iy, the second phase impulse comprising increasing the phase of each second current phase, ijy, to a second impulse phase for a second temporal period, At2, then decreasing the phase of each second current phase, ijy, back a lower level after the second temporal period, At2.
39. A displacement device according to any one of claims 1 to 38 or any other claim herein wherein the one or more magnet arrays make up a magnet array assembly and the working region is larger than a two-dimensional area of the magnet array assembly.
A displacement device according to any one of claims 1 to 39 or any other claim herein wherein np=mp.
A displacement device according to any one of claims 1 to 40 or any other claim herein wherein np=mp=3.
A displacement device according to any one of claims 1 to 41 or any other claim herein wherein the first spatial period, λι, is equal to the second spatial period, λ2, such \ &t λι=λ2=λ.
A displacement device according to any one of claims 1 to 27 and 30 to 42 wherein the first and second portions of the first and second layers correspond to a single excitation region.
44. A displacement device according to any one of claims 1 to 27 and 30 to 42 or any other claim herein wherein the plurality of electrical coils is shaped to provide a third plurality of coil traces elongated in the stator-x direction and distributed over at least a third portion of the second layer and a fourth plurality of coil traces elongated in the stator-y direction and distributed over at least a fourth portion of the first layer and wherein at least a portion of the working region overlaps the third portion of the second layer and the fourth portion of the first layer in a stator-z direction.
45. A displacement device according to any one of claims 1 to 44 or any other claim
herein wherein:
the stator comprises a stator bearing layer comprising a generally planar stator bearing surface;
the moveable stage comprises a stage bearing layer comprising a generally planar stage bearing surface;
the moveable stage is arranged atop the stator such that the stage bearing surface is generally parallel with and adjacent to the stator bearing surface; and
at least one of the stator bearing surface and the stage bearing surface
comprises polytetrafluoroethylene.
46. A displacement device according to any one of claims 1 to 45 or any other claim
herein wherein:
the stator comprises a stator bearing layer comprising a generally planar stator bearing surface;
the moveable stage comprises a stage bearing layer comprising a generally planar stage bearing surface;
the moveable stage is arranged atop the stator such that the stage bearing surface is generally parallel with and bears against the stator bearing surface; and the controller is configured to control the currents driven by the one or more amplifiers to drive the first currents, ix, in the at least some of the first plurality of coil traces and to drive the second currents, iy, in the at least some of the second plurality of coil traces, such that the first currents, ix, and the second currents, iy, create a magnetic field which causes a corresponding magnetic force on the one or more magnet arrays of the moveable stage, the magnetic force attracting the moveable stage toward the stator at when the controller is controlling the currents driven by the one or more amplifiers to move the moveable stage between first and second locations in the working region.
47. A displacement device according to any one of claims 1 to 46 or any other claim
herein wherein the controller is configured to modulate an amplitude of each first current phase ¾ based on a modulation term of the form Adsin(a)At + ψΑ) where Ad is dynamic lubrication amplitude modulation amplitude, ωΑ is a temporal amplitude modulation frequency and ψΑ is an arbitrary constant modulation phase angle.
48. A displacement device according to any one of claims 1 to 47 or any other claim
herein wherein the controller is configured to modulate a phase φ¾χ of each current phase hx based on a modulation term of the form <pdsin(o>^t + ψφ) where φά is dynamic lubrication phase modulation amplitude, ωφ is a temporal phase modulation frequency and ψφ is an arbitrary constant modulation phase angle.
49. A displacement device according to claim 47 or any other claim herein wherein the controller is configured to modulate a phase φ¾χ of each current phase ¾ based on a modulation term of the form <pdsin(o>^t + ψφ) where φά is dynamic lubrication phase modulation amplitude, ωφ is a temporal phase modulation frequency and ψφ is an arbitrary constant modulation phase angle and the controller is configured to set at least one of the modulation frequencies ωΑ and ωφ at or near a resonant frequency of the moveable stage in the stator-z direction dynamics.
50. A displacement device according to claim 47 or any other claim herein wherein the controller is configured to modulate a phase φ¾χ of each current phase hx based on a modulation term of the form <pdsin(o>^t + ψφ) where φά is dynamic lubrication phase modulation amplitude, ωφ is a temporal phase modulation frequency and ψφ is an arbitrary constant modulation phase angle and the controller is configured to set Qo)A= Ιϊωφ, where Q and R are positive or negative integer numbers.
51. A displacement device according to any one of claims 47 to 50 or any other claim herein wherein ωΑ is in a range of 2ji(50rad/s) to 2π(40χ10 rad/s).
52. A displacement device according to any one of claims 1 to 51 or any other claim
herein wherein the stator-x and stator-y directions are orthogonal to one another, the first and second layers located at corresponding first and second stator-z locations, and the plurality of electrically conductive coils is shaped to provide a third plurality of coil traces distributed over at least a portion of a third layer at a corresponding third stator-z location and generally elongated in a direction in a plane of the stator-x and stator-y directions and at an angle a relative to the stator-x direction, wherein the controller is configured to control the currents driven by the one or more amplifiers to thereby cause the moveable stage to rotate about a stage-z oriented axis, and wherein: the controller is configured to cause the one or more amplifiers, for a temporal period, to temporarily discontinue driving the first currents, ix, or substantially reduce amplitudes of the first currents, ix, in the at least some of the first plurality of coil
traces and to temporarily discontinue driving the second currents, iy, or substantially reduce amplitudes of the second currents, iy, in the at least some of the second plurality of coil traces;
during the temporal period, the controller is configured to cause the one or more amplifiers to drive third currents, ia, in at least some of the third plurality to coil traces, to thereby effect rotation of the moveable stage about the stage-z oriented axis by an angular distance a in a first angular direction.
53. A displacement device according to claim 52 or any other claim herein wherein the controller is configured, after effecting rotation of the moveable stage about the stage- z oriented axis by an angular distance a, to discontinue driving the third currents, ia, or substantially reduce amplitudes of the third currents, ia, in the at least some of the third plurality of coil traces and to drive one of: the first currents, ix, in the at least some of the first plurality of coil traces and the second currents, iy, in the at least some of the second plurality of coil traces to thereby effect rotation of the moveable stage about the stage-z oriented axis by a further angular distance (90°-a) in the first angular direction.
54. A displacement device according to any one of claims 1 to 51 or any other claim
herein wherein the plurality of electrically conductive coils is shaped to provide a third plurality of coil traces generally elongated in the stator-x direction, the first plurality of coil traces and the third plurality of coil traces separated by a first boundary plane, wherein the controller is configured to control the currents driven by the one or more amplifiers to thereby cause the moveable stage to rotate about a stage-z oriented axis which coincides with the first boundary plane, and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive first positive rotational currents in the first plurality of coil traces and first negative rotational currents in the third plurality of coil traces;
the first positive rotational currents comprise a plurality of first positive rotational current phases, each first positive rotational current phase driven into a corresponding one of the first plurality of coil traces and phase-adjacent first positive
rotational current phases driven into spatially adjacent ones of the first plurality of coil traces, where each first positive rotational current phase is a periodic function of yr+ dr, with period equal to the first spatial period, λι where dr is a rotational reference parameter;
the first negative rotational currents comprise a plurality of first negative rotational current phases, each first negative rotational current phase driven into a corresponding one of the third plurality of coil traces and phase-adjacent first negative rotational current phases driven into spatially adjacent ones of the third plurality of coil traces, where each first negative rotational current phase is a periodic function of yr-dr, with period equal to the first spatial period, λι;
and wherein the controller is configured to at least one of: increase the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a first angular direction and decrease the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a second angular direction, opposed to the first angular direction.
55. A displacement device according to claim 54 or any other claim herein wherein the first boundary plane extends in the stator-z and stator-x directions and the stage-z oriented axis is coincident with the first boundary plane.
56. A displacement device according to claim 54 or any other claim herein wherein the first boundary plane extends in the stator-z and stator-y directions and the stage-z oriented axis is coincident with the first boundary plane.
57. A displacement device according claim 55 or any other claim herein wherein the plurality of electrically conductive coils is shaped to provide a fourth plurality of coil traces generally elongated in the stator-y direction, the second plurality of coil traces and the fourth plurality of coil traces separated by a second boundary plane, wherein the stage-z oriented axis coincides with the second boundary plane and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive second positive rotational currents in the second plurality of coil traces and
second negative rotational currents in the fourth plurality of coil traces;
the second positive rotational currents comprise a plurality of second positive rotational current phases, each second positive rotational current phase driven into a corresponding one of the second plurality of coil traces and phase- adjacent second positive rotational current phases driven into spatially adjacent ones of the second plurality of coil traces, where each second positive rotational current phase is a periodic function of xr+dr, with period equal to the second spatial period, λ2;
the second negative rotational currents comprise a plurality of second negative rotational current phases, each second negative rotational current phase driven into a corresponding one of the fourth plurality of coil traces and phase-adjacent second negative rotational current phases driven into spatially adjacent ones of the fourth plurality of coil traces, where each second negative rotational current phase is a periodic function of xr-dr, with period equal to the second spatial period, λ2.
58. A displacement device according to claim 57 or any other claim herein wherein the second boundary plane is co-planar with the first boundary plane.
59. A displacement device according to claim 57 or any other claim herein wherein the second boundary plane extends in the stator-z and stator-y directions.
60. A displacement device according claim 56 or any other claim herein wherein the plurality of electrically conductive coils is shaped to provide a fourth plurality of coil traces generally elongated in the stator-y direction, the second plurality of coil traces and the fourth plurality of coil traces separated by a second boundary plane, wherein the stage-z oriented axis coincides with the second boundary plane and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive second positive rotational currents in the second plurality of coil traces and second negative rotational currents in the fourth plurality of coil traces;
the second positive rotational currents comprise a plurality of second positive rotational current phases, each second positive rotational current phase driven into a corresponding one of the second plurality of coil traces and phase- adjacent second
positive rotational current phases driven into spatially adjacent ones of the second plurality of coil traces, where each second positive rotational current phase is a periodic function of xr+dr, with period equal to the second spatial period, λ2;
the second negative rotational currents comprise a plurality of second negative rotational current phases, each second negative rotational current phase driven into a corresponding one of the fourth plurality of coil traces and phase-adjacent second negative rotational current phases driven into spatially adjacent ones of the fourth plurality of coil traces, where each second negative rotational current phase is a periodic function of xr-dr, with period equal to the second spatial period, λ2.
61. A displacement device according to claim 60 or any other claim herein wherein the second boundary plane is coplanar with the first boundary plane.
62. A displacement device according to claim 60 or any other claim herein wherein the second boundary plane extends in the stator-z and stator-x directions.
63. A displacement device according to any one of claims 1 to 51 or any other claim herein wherein the plurality of electrically conductive coils is shaped to provide a third plurality of coil traces generally elongated in the stator-x direction, the first plurality of coil traces and the third plurality of coil traces respectively located in first and second excitation regions, wherein the controller is configured to control the currents driven by the one or more amplifiers to thereby cause the moveable stage to rotate about a stage-z oriented axis which coincides with a vertex where a first corner of the first excitation region meets a second corner of the second excitation region, and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive first positive rotational currents in the first plurality of coil traces and first negative rotational currents in the third plurality of coil traces;
the first positive rotational currents comprise a plurality of first positive rotational current phases, each first positive rotational current phase driven into a corresponding one of the first plurality of coil traces and phase-adjacent first positive rotational current phases driven into spatially adjacent ones of the first plurality of
coil traces, where each first positive rotational current phase is a periodic function of yr+ dr, with period equal to the first spatial period, λι, where dr is a rotational reference parameter;
the first negative rotational currents comprise a plurality of first negative rotational current phases, each first negative rotational current phase driven into a corresponding one of the third plurality of coil traces and phase-adjacent first negative rotational current phases driven into spatially adjacent ones of the third plurality of coil traces, where each first negative rotational current phase is a periodic function of yr-dr, with period equal to the first spatial period, λι
and wherein the controller is configured to at least one of: increase the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a first angular direction and decrease the rotational reference parameter dr to effect rotation about the stage-z oriented axis in a second angular direction, opposed to the first angular direction.
A displacement device according to claim 63 or any other claim herein wherein the plurality of electrically conductive coils is shaped to provide fourth and fifth pluralities of coil traces generally elongated in the stator-y direction, the fourth plurality of coil traces and the fifth plurality of coil traces respectively located in third and fourth excitation regions, wherein the stage-z oriented axis coincides with a second vertex where a third corner of the third excitation region meets a fourth corner of the fourth excitation region, and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive second positive rotational currents in the fourth plurality of coil traces and second negative rotational currents in the fifth plurality of coil traces;
the second positive rotational currents comprise a plurality of second positive rotational current phases, each second positive rotational current phase driven into a corresponding one of the fourth plurality of coil traces and phase-adjacent second positive rotational current phases driven into spatially adjacent ones of the fourth plurality of coil traces, where each second positive rotational current phase is a periodic function of xr+dr, with period equal to the second spatial period, λ2;
the second negative rotational currents comprise a plurality of second negative rotational current phases, each second negative rotational current phase driven into a corresponding one of the fifth plurality of coil traces and phase-adjacent second negative rotational current phases driven into spatially adjacent ones of the fifth plurality of coil traces, where each second negative rotational current phase is a periodic function of xr-dr, with period equal to the second spatial period, λ2.
65. A displacement device according to any one of claims 54 to 64 or any other claim herein wherein the controller is configured to drive currents which cause simultaneous rotation of the moveable stage about the z-oriented axis and translation of the moveable stage.
66. A displacement device according to any one of claims 54 to 65 or any other claim herein wherein the third plurality of coil traces is distributed over at least a third portion of the first layer.
67. A displacement device according to any one of claims 54 to 65 or any other claim herein wherein the third plurality of coil traces is distributed over at least a third portion of a third layer, the third layer at a third stator-z location that is different from a first stator-z location of the first layer.
68. A displacement device according to any one of claims 11 to 12 or any other claim herein wherein: the stage-y direction width Wmy of the first magnet array is related to the first spatial period λ1 according to Wmy = a where a is a positive integer such that the first magnetization directions of the first magnetization segments exhibit one or more half periods over the stage-y direction width of the first magnet array; and the stage-x direction width Wmx of the second magnet array is related to the second spatial period λ2 according to Wmx = b— where b is a positive integer such that the second magnetization directions of the second magnetization segments exhibit one or more half periods over the stage-x direction width of the second magnet array.
69. A displacement device according to claim 12 or any other claim herein wherein: the stage-y direction width Wmy of the first magnet array is related to the first spatial period λ1 according to Wmy = a ~ where a is a positive integer such that the first magnetization directions of the first magnetization segments exhibit one or more half periods over the stage-y direction width of the first magnet array; the stage-x direction width Wmx of the second magnet array is related to the second spatial period λ2 according to Wmx = b where b is a positive integer such that the second magnetization directions of the second magnetization segments exhibit one or more half periods over the stage-x direction width of the second magnet array; the stage-y direction width Wmy of the third magnet array is related to the first spatial period λ1 according to Wmy = a where a is a positive integer such that the third
magnetization directions of the third magnetization segments exhibit one or more half periods over the stage-y direction width of the third magnet array; and the stage-x direction width Wmx of the fourth magnet array is related to the second spatial period λ2 according to Wmx = b where b is a positive integer such that the fourth magnetization directions of the fourth magnetization segments exhibit one or more half periods over the stage-x direction width of the fourth magnet array
70. A displacement device according to any one of claims 21 and 23 or any other claim herein wherein the first magnet array has two principal directions and each sub-array has a width equal to the first spatial period λ1 in a first of the two principal directions and a width equal to the second spatial period λ2 in a second of the two principal directions.
71. A method, in a displacement device, for controlling the movement of a moveable stage relative to a stator, the method comprising:
providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
providing a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
controllably driving a plurality of currents into the plurality of electrical coils to thereby cause the moveable stage to track a desired position, (xr,yr), within the working region, where xr is a desired position of the moveable stage in the stator-x direction in the working region and yr is a desired position of the moveable stage in the stator-y direction in the working region;
wherein controllably driving the plurality of currents into the plurality of electrical coils comprises:
driving first currents, ix, in at least some of the first plurality of coil traces and driving second currents, iy, in at least some of the second plurality of coil traces; the first currents, ix, comprising a plurality of first current phases, each first current phase, driven into a corresponding one of the at least some of the first plurality of coil traces and phase- adjacent first current phases driven into spatially adjacent ones of the at least some of the first plurality of coil traces, where:
k is an integer from 0 to np-\ representing a first phase index; and np is a number of different effective phases in the first currents, ix; each first current phase, is determined based on a function F(yr), where F(yr) is a spatially periodic function of yr in the stator-y direction over the working region, with a first spatial period, λΰ
each first current phase, in a particular one of the at least some of the first plurality of coil traces is out of phase, as a function of yr, with one or
more phase- adjacent first current phases in one or more spatially adjacent ones of the at least some of the first plurality of coil traces by a first spatial phase difference— ;
2np
the second currents, iy, comprising a plurality of second current phases, each second current phase, ijy, driven into a corresponding one of the at least some of the second plurality of coil traces and phase-adjacent second current phases driven into spatially adjacent ones of the at least some of the second plurality of coil traces, where:
j is an integer from 0 to mp-\ representing a second phase index; and mp is a number of different effective phases in the second currents, iy; each second current phase, ijy, is determined based on a function G(xr), where G(xr) is a spatially periodic function of xr in the stator-x direction over the working region, with a second spatial period, λ2; and
each second current phase, ijy, in a particular one of the at least some of the second plurality of coil traces is out of phase, as a function of xr, with one or more phase-adjacent second current phases in one or more spatially adjacent ones of the at least some of the second plurality of coil traces by a second spatial phase difference
2mp
A method according to claim 71 or any other claim herein wherein:
the moveable stage is one of a first group of one or more moveable stages; and the plurality of electrically conductive coils is shaped to provide:
a third plurality of coil traces generally elongated in a stator-x direction and distributed over at least a third portion of a third layer;
a fourth plurality of coil traces generally elongated in a stator-y direction and distributed over at least a fourth portion of a fourth layer;
the third and fourth portions of the third and fourth layers overlapping one another in a stator-z direction; and
the method comprises
providing a second group one or more moveable stages, each of the second
group of moveable stages comprising one or more second magnet arrays, the one or more second magnet arrays comprising a second magnet array, the second magnet array comprising a plurality of second magnetization segments, each second magnetization segment having a corresponding second magnetization direction; controllably driving the plurality of currents into the plurality of electrical coils to separate the first group of moveable stages from the second group of moveable stages, wherein controllably driving the plurality of currents into the plurality of electrical coils to separate the first group of moveable stages from the second group of moveable stages comprises:
providing a plurality of stator-z-direction-non-overlapping excitation regions comprising: a first excitation region wherein the first and second portions of the first and second layers overlap one another in a stator-z direction; and a second excitation region wherein the third and fourth portions of the third and fourth layers overlap one another in the stator-z direction; driving the plurality of currents into the plurality of electrical coils to position the first and second groups of moveable stages at a location in the working region wherein a first boundary plane extending in the stator-z direction between the first excitation region and the second excitation regions divides the first and second groups of moveable stages;
driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region to at least one of: move the first group of moveable stages in a first direction away from the first boundary plane; and move the first group of moveable stages in a first direction away from the second group of moveable stages, the first direction parallel with the first boundary plane surface;
while driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region:
driving at least some of the plurality of currents in at least some of the coil traces of the second excitation region to at least one of: maintain a location of the second group of moveable stages within the working region; move the second group of moveable stages in a
second direction away from the first boundary plane; and move the second group of moveable stages in a second direction away from the first group of moveable stages, the second direction parallel with the first boundary plane surface.
73. A method according to claim 72 or any other claim herein wherein the first boundary plane extending between the first and second excitation regions is in one of a stator-x- stator-z plane and a stator-y-stator-z plane.
74. A method according to any one of claims 72 and 73 or any other claim herein
comprising controllably driving a second plurality of currents into the plurality of electrical coils to thereby cause a first sub-group of the first group of moveable stages to separate from a second sub-group of the first group of moveable stages, wherein controllably driving the second plurality of currents into the plurality of electrical coils comprises:
driving the second plurality of currents into the plurality of electrical coils to position the first group of moveable stages at a location in the working region wherein a second boundary plane extending in the stator-z direction between a third excitation region of the plurality of excitation regions and a fourth excitation region of the plurality of excitation regions divides the first sub-group and the second sub-group of the first group of moveable stages; and
driving at least some of the second plurality of currents in at least some coil traces of the third excitation region to at least one of: move the first sub-group of the first group of moveable stages in a third direction away from the second boundary plane; and move the first sub-group of the first group moveable stages in a direction away from the second sub-group of the first group of moveable stages, the third direction parallel with the second boundary plane surface;
while driving at least some of the second plurality of currents in at least some coil traces of the third excitation region:
driving at least some of the second plurality of currents in at least some coil traces of the fourth excitation region to at least one of: maintain the
location of the second sub-group of the first group of moveable stages within the working region; move the second sub-group of moveable stages in a fourth direction away from the second boundary plane; and move the second subgroup of the first group of moveable stages in a fourth direction away from the first sub-group of the first group of moveable stages, the fourth direction parallel with the second boundary plane surface.
A method according to claim 74 or any other claim herein wherein the second boundary plane is in one of a stator-x-stator-z plane and a stator-y-stator-z plane is orthogonal to the first boundary plane.
A method according to any one of claims 74 to 75 or any other claim herein wherein the third direction is orthogonal to the first direction.
77. A method according to any one of claims 74 to 76 or any other claim herein wherein the third excitation region is one of the first excitation region and the second excitation region.
78. A method according to any one of claims 74 to 77 or any other claim herein wherein the fourth excitation region is one of the first excitation region and the second excitation region, but is different than the third excitation region.
79. A method according to any one of claims 74 to 78 or any other claim herein wherein a stator-z location of the third layer is the same as one of: a stator-z location of the first layer; and a stator-z location of the second layer.
80. A method according to any one of claims 72 to 79 or any other claim herein wherein, for each moveable stage in the first and second groups of moveable stages:
a stator-x dimension of the first excitation region is greater than a stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage;
a stator-y dimension of the first excitation region is greater than a stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage;
a stator-x dimension of the second excitation region is greater than the stage-x dimension of the moveable stage and less than twice the stage-x dimension of the moveable stage;
a stator-y dimension of the second excitation region is greater than the stage-y dimension of the moveable stage and less than twice the stage-y dimension of the moveable stage.
81. A method according to any one of claims 72 to 80 or any other claim herein wherein driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region comprises driving the first currents, ix, into the first plurality of coil traces.
82. A method according to any one of claims 72 to 81 or any other claim herein wherein driving at least some of the plurality of currents in at least some of the coil traces of the first excitation region comprises driving the second currents, iy, into the second plurality of coil traces.
83. A method according to any one of claims 71 to 82 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
84. A displacement device comprising:
a stator comprising a stator bearing layer comprising a generally planar stator bearing surface extending in orthogonal stator-x and stator-y directions and a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
a moveable stage comprising a stage bearing layer comprising a generally planar stage bearing surface extending in orthogonal stage-x and stage-y directions and one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first
magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the plurality of currents driven by the one or more amplifiers to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces;
wherein the moveable stage is arranged atop the stator such that the stage bearing surface is generally parallel with and bears against the stator bearing surface; and
wherein at least one of the stator bearing surface or the stage bearing surface is fabricated from polytetrafluoroethylene.
85. A displacement device according to claim 84 comprising any of the features,
combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
86. A method, in a displacement device, for controlling the movement of a moveable
stage relative to a stator, the method comprising:
providing a stator comprising a stator bearing layer comprising a generally planar stator bearing surface extending in orthogonal stator-x and stator-y directions and a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
providing a moveable stage comprising a stage bearing layer comprising a generally planar stage bearing surface extending in orthogonal stage-x and stage-y directions and one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
controllably driving a plurality of first currents, ix, in at least some of the first plurality of coil traces and a plurality of second currents, iy, in at least some of the second plurality of coil traces to thereby controllably move the moveable stage in the working region;
arranging the moveable stage atop the stator such that the stage bearing surface is generally parallel with and bears against the stator bearing surface; and fabricating at least one of the stator bearing surface or the stage bearing surface from polytetrafluoroethylene.
A method according to claim 86 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim
herein.
A displacement device comprising:
a stator comprising a stator bearing layer comprising a generally planar stator bearing surface extending in orthogonal stator-x and stator-y directions and a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
a moveable stage comprising a stage bearing layer comprising a generally planar stage bearing surface extending in orthogonal stage-x and stage-y directions and one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first
magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the plurality of currents driven by the one or more amplifiers to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces;
wherein the moveable stage is arranged atop the stator such that the stage bearing surface is generally parallel with and bears against the stator bearing surface;
and
wherein the controller is configured to control the plurality of currents driven by the one or more amplifiers to create a magnetic field which causes a corresponding magnetic force on the one or more magnet arrays of the moveable stage, the magnetic force attracting the moveable stage toward the stator at when the controller is controlling the currents driven by the one or more amplifiers to move the moveable stage between first and second locations in the working region.
89. A displacement device according to claim 88 comprising any of the features,
combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
90. A method, in a displacement device, for controlling the movement of a moveable stage relative to a stator, the method comprising:
providing a stator comprising a stator bearing layer comprising a generally planar stator bearing surface extending in orthogonal stator-x and stator-y directions and a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
providing a moveable stage comprising a stage bearing layer comprising a generally planar stage bearing surface extending in orthogonal stage-x and stage-y directions and one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first
magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
arranging the moveable stage atop the stator such that the stage bearing surface is generally parallel with and bears against the stator bearing surface
controllably driving a plurality of currents into the plurality of electrical coils to thereby control movement of the moveable stage relative to the stator within the working region, wherein controllably driving the plurality of currents comprises: driving first currents, ix, in at least some of the first plurality of coil traces, driving second currents, iy, in at least some of the second plurality of coil traces and thereby creating a magnetic field which causes a corresponding magnetic force on the one or more magnet arrays of the moveable stage, the magnetic force attracting the moveable stage toward the stator at when controllably driving the plurality of currents to control movement of the moveable stage between first and second locations in the working region.
91. A method according to claim 90 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
92. A displacement device comprising:
a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
a moveable stage comprising one or more magnet arrays, the moveable stage
moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the currents driven by the one or more amplifiers and to thereby cause the moveable stage to track a desired position, (xr,yr), within the working region, where xr is a desired position of the moveable stage in the stator-x direction in the working region and yr is a desired position of the moveable stage in the stator-y direction in the working region;
wherein:
the controller is configured to control the currents driven by the one or more amplifiers to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces; the first currents, ix, comprise a plurality of first current phases, ikx, each first current phase, ikx, driven into a corresponding one of the at least some of the first plurality of coil traces and phase- adjacent first current phases driven into spatially adjacent ones of the at least some of the first plurality of coil traces, where:
k is an integer from 0 to np-\ representing a first phase index; and np is a number of different effective phases in the first currents, ix; each first current phase, ikx, is determined according to ikx =
Akx sin ( - 2π— k— + φχ ) where, Aux is an amplitude of the k* first current phase, ikx, ; is a first spatial period and φχ is an arbitrary phase offset;
each first current phase, ikx, in a particular one of the at least some of the first plurality of coil traces is out of phase, as a function of yr, with one or more phase- adjacent first current phases in one or more spatially adjacent ones of the at least some of the first plurality of coil traces by a first phase difference— ;
the second currents, iy, comprise a plurality of second current phases, ijy, each second current phase, ijy, driven into a corresponding one of the at least some of the second plurality of coil traces and phase-adjacent second current phases driven into spatially adjacent ones of the at least some of the second plurality of coil traces, where:
j is an integer from 0 to mp- \ representing a second phase index; and mp is a number of different effective phases in the second currents, iy; each second current phase, ijy, is determined according to i;y =
Ajy sin (^ - 2π— j -^- + <py where, Ajy is an amplitude of the jth second current phase, ijy, λ2 is a second spatial period and φν is an arbitrary phase offset; and each second current phase, ijy, in a particular one of the at least some of the second plurality of coil traces is out of phase, as a function of xr, with one or more phase-adjacent second current phases in one or more spatially adjacent ones of the at least some of the second plurality of coil traces by a second phase difference— .
A displacement device according to claim 92 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
A method, in a displacement device, for controlling the movement of a moveable stage relative to a stator, the method comprising:
providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
the first and second portions of the first and second layers overlapping
one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
providing a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
controllably driving a plurality of currents into the plurality of electrical coils to thereby cause the moveable stage to track a desired position, (xr,yr), within the working region, where xr is a desired position of the moveable stage in the stator-x direction in the working region and yr is a desired position of the moveable stage in the stator-y direction in the working region;
wherein controllably driving the plurality of currents into the plurality of electrical coils comprises:
driving first currents, ix, in at least some of the first plurality of coil traces and driving second currents, iy, in at least some of the second plurality of coil traces; the first currents, ix, comprising a plurality of first current phases, each first current phase, ikx, driven into a corresponding one of the at least some of the first plurality of coil traces and phase- adjacent first current phases driven into spatially adjacent ones of the at least some of the first plurality of coil traces, where:
k is an integer from 0 to np-\ representing a first phase index; and np is a number of different effective phases in the first currents, ix; each first current phase, ikx, is determined according to ikx =
Akx sin ( - 2π— k— + φχ ) where, Aux is an amplitude of the k* first current phase, ikx, ; is a first spatial period and φχ is an arbitrary phase offset;
each first current phase, ikx, in a particular one of the at least some of the first plurality of coil traces is out of phase, as a function of yr, with one or more phase- adjacent first current phases in one or more spatially adjacent ones of the at least some of the first plurality of coil traces by a first phase difference— ;
the second currents, iy, comprising a plurality of second current phases, each second current phase, ijy, driven into a corresponding one of the at least some of the second plurality of coil traces and phase-adjacent second current phases driven into spatially adjacent ones of the at least some of the second plurality of coil traces, where:
j is an integer from 0 to mp- \ representing a second phase index; and mp is a number of different effective phases in the second currents, iy; each second current phase, ijy, is determined according to i;y =
Ajy sin (^ - 2π— j -^- + <py where, Ajy is an amplitude of the jth second current phase, ijy, λ2 is a second spatial period and φν is an arbitrary phase offset; and each second current phase, ijy, in a particular one of the at least some of the second plurality of coil traces is out of phase, as a function of xr, with one or more phase-adjacent second current phases in one or more spatially adjacent ones of the at least some of the second plurality of coil traces by a second phase difference— .
A method according to claim 94 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
A displacement device comprising:
a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal
to both the stator-x direction and the stator-y direction;
wherein the first and second layers are located at corresponding first and second stator-z locations, and
wherein the plurality of electrically conductive coils is shaped to provide a third plurality of coil traces distributed over at least a portion of a third layer at a corresponding third stator-z location and generally elongated in a direction in a plane of the stator-x and stator-y directions and at an angle a relative to the stator-x direction;
a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the plurality of currents driven by the one or more amplifiers to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces to thereby control a position of the moveable stage within the working region; and
wherein the controller is configured to control the currents driven by the one or more amplifiers to thereby cause the moveable stage to rotate about a stage-z oriented axis, and wherein:
the controller is configured to cause the one or more amplifiers, for a temporal period, to temporarily discontinue driving the first currents, ix, or substantially reduce amplitudes of the first currents, ix, in the at least some of the first plurality of coil traces and to temporarily discontinue driving the second currents, iy, or substantially reduce amplitudes of the second currents, iy, in the at least some of the second plurality of coil traces;
during the temporal period, the controller is configured to cause the one or
more amplifiers to drive third currents, ia, in at least some of the third plurality to coil traces, to thereby effect rotation of the moveable stage about the stage-z oriented axis by an angular distance a in a first angular direction.
97. A displacement device according to claim 96 comprising any of the features,
combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
98. A method, in a displacement device, for controlling the movement of a moveable stage relative to a stator, the method comprising:
providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction orthogonal to the stator-x direction;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
wherein the first and second layers are located at corresponding first and second stator-z locations; and
wherein the plurality of electrically conductive coils is shaped to provide a third plurality of coil traces distributed over at least a portion of a third layer at a corresponding third stator-z location and generally elongated in a direction in a plane of the stator-x and stator-y directions and at an angle a relative to the stator-x direction;
providing a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first
magnetization segment having a corresponding first magnetization direction;
controllably driving a plurality of currents into the plurality of electrical coils to drive first currents, ix, in at least some of the first plurality of coil traces and to drive second currents, iy, in at least some of the second plurality of coil traces to thereby control a position of the moveable stage within the working region;
controllably driving the plurality of currents into the plurality of electrical coils to cause the moveable stage to rotate about a stage-z oriented axis, wherein controllably driving the plurality of currents into the plurality of electrical coils to cause the moveable stage to rotate about the stage-z oriented axis comprises:
for a temporal period, temporarily discontinuing driving the first currents, ix, or substantially reducing amplitudes of the first currents, ix, in the at least some of the first plurality of coil traces and temporarily discontinuing driving the second currents, iy, or substantially reducing amplitudes of the second currents, iy, in the at least some of the second plurality of coil traces; during the temporal period, controllably driving third currents, ia, in at least some of the third plurality to coil traces, to thereby effect rotation of the moveable stage about the stage-z oriented axis by an angular distance a in a first angular direction.
A method according to claim 98 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein. A displacement device comprising:
a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
a third plurality of coil traces generally elongated in the stator-x direction, the first plurality of coil traces and the third plurality of coil traces separated by a first boundary plane;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first magnetization segment having a corresponding first magnetization direction;
one or more amplifiers connected to drive a plurality of currents in the plurality of electrically conductive coils;
a controller connected to deliver signals to the one or more amplifiers and configured, by using such signals, to control the currents driven by the one or more amplifiers and to thereby cause the moveable stage to rotate about a stage-z oriented axis which coincides with the first boundary plane, and wherein the controller is configured to control the currents driven by the one or more amplifiers to drive first positive rotational currents in the first plurality of coil traces and first negative rotational currents in the third plurality of coil traces;
the first positive rotational currents comprise a plurality of first positive rotational current phases, each first positive rotational current phase driven into a corresponding one of the first plurality of coil traces and phase-adjacent first positive rotational current phases driven into spatially adjacent ones of the first plurality of coil traces, where each first positive rotational current phase is a periodic function of yr+ dr, where yr is a desired position of the moveable stage in the stator-y direction in the working region and dr is a rotational reference parameter;
the first negative rotational currents comprise a plurality of first negative rotational current phases, each first negative rotational current phase driven into a corresponding one of the third plurality of coil traces and phase-adjacent first negative rotational current phases driven into spatially adjacent ones of the third plurality of
coil traces, where each first negative rotational current phase is a periodic function of yr-dr; and
wherein the controller is configured to at least one of: increase the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a first angular direction and decrease the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a second angular direction, opposed to the first angular direction.
101. A displacement device according to claim 100 comprising any of the features,
combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
102. A method, in a displacement device, for controlling the movement of a moveable stage relative to a stator, the method comprising:
providing a stator comprising a plurality of electrically conductive coils, the plurality of electrically conductive coils shaped to provide:
a first plurality of coil traces generally elongated in a stator-x direction and distributed over at least a first portion of a first layer;
a second plurality of coil traces generally elongated in a stator-y direction and distributed over at least a second portion of a second layer, the stator-y direction non-parallel to the stator-x direction;
a third plurality of coil traces generally elongated in the stator-x direction, the first plurality of coil traces and the third plurality of coil traces separated by a first boundary plane;
the first and second portions of the first and second layers overlapping one another in a stator-z direction, the stator-z direction generally orthogonal to both the stator-x direction and the stator-y direction;
providing a moveable stage comprising one or more magnet arrays, the moveable stage moveable relative to the stator within a two-dimensional working region, the one or more magnet arrays comprising a first magnet array, the first magnet array comprising a plurality of first magnetization segments, each first
magnetization segment having a corresponding first magnetization direction;
controllably driving first positive rotational currents in the first plurality of coil traces and first negative rotational currents in the third plurality of coil traces to cause the moveable stage to rotate about a stage-z oriented axis which coincides with the first boundary plane;
wherein:
the first positive rotational currents comprise a plurality of first positive rotational current phases, each first positive rotational current phase driven into a corresponding one of the first plurality of coil traces and phase-adjacent first positive rotational current phases driven into spatially adjacent ones of the first plurality of coil traces, where each first positive rotational current phase is a periodic function of yr+ dr, where yr is a desired position of the moveable stage in the stator-y direction in the working region and dr is a rotational reference parameter;
the first negative rotational currents comprise a plurality of first negative rotational current phases, each first negative rotational current phase driven into a corresponding one of the third plurality of coil traces and phase-adjacent first negative rotational current phases driven into spatially adjacent ones of the third plurality of coil traces, where each first negative rotational current phase is a periodic function of yr-dr; and
wherein controllably driving first positive rotational currents in the first plurality of coil traces and first negative rotational currents in the third plurality of coil traces comprises at least one of: increasing the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a first angular direction and decreasing the rotational reference parameter dr over time to effect rotation about the stage-z oriented axis in a second angular direction, opposed to the first angular direction.
A method according to claim 102 comprising any of the features, combinations of features or sub-combinations of features of any of claims 1 to 70 or any other claim herein.
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Cited By (33)
Publication number | Priority date | Publication date | Assignee | Title |
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