CA1292661C - Force and torque converter - Google Patents
Force and torque converterInfo
- Publication number
- CA1292661C CA1292661C CA000588461A CA588461A CA1292661C CA 1292661 C CA1292661 C CA 1292661C CA 000588461 A CA000588461 A CA 000588461A CA 588461 A CA588461 A CA 588461A CA 1292661 C CA1292661 C CA 1292661C
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Abstract
A force and torque converter provides command signals representative of a translational applied force and an applied torque extending about an axis substantially perpendicular to the axis along which the translational force is applied. The apparatus comprises of body to which the force and torque are applied, first and second connecting means attached to the body, means for biasing the connecting means to a central position and sensor means comprising two sensor devices arranged to detect a displacement force in each of the first and second connecting means respectively and which respond to the applied translation force and also respond to the torque to resolve the torque into a force comprising two components. A very important embodiment of the invention is arranged to operate in three dimensions and to resolve any applied torque into a respective components related to three mutually perpendicular axes. The apparatus can thus interpret operator applied hand signals for controlling an apparatus such as a computer based system.
Description
lZ~2661 ~IELD OF THE INVENTIQN
The present invention relates to a force and torque converter and has useful applications in a wide field of activities particularly where a manual motion ~s to be converted into a cont~ol ~signal~. For esample, machines such as industrial robots, back hoes and computer graphic works~ations have comples control reguirements.
BAC~QUND TO THE IEY~TIQ~
In esisting systems, control of a vehicle such as a back hoe is achieved by manipulation of levers and more ~ecently by joy sticks. In computer applications joy sticks are a common control system but a computer may also employ a ~track ball"
or a ~mouse~. These devices have limited directions of motion ~ and accordingly limited commands only are possible.
In addition to a control system, there is also a need for a sensing system to monitor applied forces and torques; an esample of such a sensor system is a system for monitoring applied forces and torques with respect to three a~es in a manipulator (see United States Patent 3 921 445 Hill and Sword). In that specification the manipulator is of a hand like form comprising a pair of jaws which are relatively pivotally movable under operation of an electric motor. The manipulator is defined as having a wrist and sensing means are provided for sensing the magnitude and direction of forces along three mutually orthoganal a~es intersecting at the wrist and for sensing the magnitude and direction of torques about the axes. The form of the sensing means is a series of sensors extending around the longitudinal asis of the manipulator.
~SUMMARY OF THE INVE~TION
In one aspect, the present invention consists in an apparatus for providing output signals for use as command 129Z~iGl fiignals with respect to X, Y and Z mutually osthogonal a~es, the signals being representative of a translational applied force and an applied torque, the apparatus comprising a ~ase, a body to which the forces and tor~ues are applied, resilient S connecting means attached to the body and mounting the body for receiving force in any direction ana torque about any asis and for resiliently resisting displacement of the body from a normal position relative to the base, and sensor means arranged to detect a response to and to provide said output signals corresponding to components of an applied torque and components of an applied translational force with respect to said ases, and wherein said sensor means comprise either (a) a sis sensor unit configuration arranged in a three dimensional substantially uniform array with respect to said X, Y and Z
ases, the sensor units being arranged in pairs for detecting displacement along a respective operating axis, a first pair of said sensor units having an operating a~is in the X
direction, a second pair of said sensor units having an operating asis in the Y direction and a third pair of said sensor units having an operating asis in the ~ direction, each of the sensor units being non-responsive to any displacement at right angles to its operating axis, whereby the output signals may be processed to provide a command signal corresponding to any applied torque or any applied translational force, cr (b) a four sensor unit configuration arranged in two pairs and in accordance with two of the three pairs of sensor units in said six sensor unit configurat;on.
In the preferred embodiments described below, a very small displacement results from each of the translational force and applied torque, the connecting means being biased ~o a central position. However, it is possible to embody the invention in a form in which no displacement takes place and instead sensors respond whereby a signal is derived representative of the force or torque tending to cause displacement at each sensor. For example, a system in which automatic control causes the input of some energy to resist the displacement could be used, the input of energy having a lZg2~1 corresponding signal generated for indicating the magnitude of the applied force.
The invention is especially ~aluabl~ in permitting embodiments in which the applied translational force and/or the applied torque are respectively resolved into components with respect to most prefera~ly three mutually ~erpendicular ases. Hereinafter the invention will be e~emplifed with reference to the most comples esample ~n which a three dimensional device is utilised and it w;ll be appreciated that a comples ergonomically designed contro~ system can utilise an apparatus of this form. It is envisage~ that for many applications a handle or grip for an operator will be provided and this grip is adapted to receive a t~nslational force and a torque, the translational force being applied in any direction and the torque being about a~ desired a~is. The output signals can be used to control a~y required device and sophisticated control of, for esample, a machine can be achieved with just one control member. ~his can be very important for the control of complex ma~hines which require an operator to use a multiplicity of separ~ite levers for controlling, e.g. hydraulic circuits. ~nother area in which there may be very beneficial applicatio~3 is for control of devices for handicapped persons.
In a preferred embodiment the appa~tus is such that only at most very small displacement results from the applied translational force and~or torque. In ~;he mechanical examples described hereinafter the mathematical ~rror resulting from displacement is at most exceedingly sma~l and may be disregarded for very small angles of di$placement.
In one specific embodiment, the fi~ed base has a portion at which the X, Y and Z axes intersect and the connecting means comprise respective pairs of resiliently deformable connecting arms extending in the Z and ~ directions, the arms of each pair extending away from the ba~se portion in opposite directions to be connected to the body, and wherein the sensor means are adapted to detect a displacement in the respective connecting arms and provide signals permitting computation of 12gZ661 the applied torque and/or force, the sensor means detecting torque about the Y axis or displacement in the X direction at respective locations in the arms e~tending in the Z direction on opposite sides of the X axis, and detecting torgue about the X a~is or displacement in the Z direction at respective locations ~n the connecting arms e~tending in the Y direction on opposite sides of the Z a~is.
Preferably, ~he apparatus described in the previous para~raph is such that the remote ends of said arms are constrained against movement in second and third mutually perpendicular a~es, which are each perpendicular to said first asis.
When the embodiment of the preceding paragraph is applied to a three dimensional version, then the connecting means comprises three pairs of arms eYtending mutually perpendicularly and co-operating with the body so that the respective pairs of arms are constrained about respective mutually perpendicular axes.
Apparatus according to the invention preferably includes signal processing means for processing the signals detected at the respective sensor means whereby output signals correspond with the applied torque and the applied translational force and, in the case of a three dimensional version of the invention, the output signals represent the resolution of the applied force and applied torque with respect to three mutually perpendicular axis.
A second important embodiment of the invention is one in which the connecting means comprises a series of three connecting structures each comprising an arm extending from the body and pivotally connected through a joint having universal action through at least a limited range of angles to a leg, the leg extendinq normally in a direction substantially at right angles to the arm to be attached to the fi~ed base, the biasing means biasing the leg to a central position and the leg having an ability to move aqainst the biasing in a plane being substantially that containing the pivot point of the universal joint and substantially perpendicular to the axis of the leg.
Preferably, a universal joint providing a limited range of motion is used for the pivotal connection between the leg and the arm.
Preferably, the apparatus is arranged such that each of arms of the connecting structur~s has its pivotal connection with its leg member 6uch that a reference a~is of the connecting member extends rom a central point in the body through the pivotal connection and this reference a~is is substantially at right angles to the asis along which displacement is sensed by displacement of the pivotal connection.
Preferably, each leg member is arranged to e~tend at right angles to the reference asis of the associated connecting member, the remote end of the leg member being fixed.
Preferably, the biasing means includes resilient deformability provided in the leg member and for this purpose preferably a reduced diameter portion is provided in the leg member near its remote fixed end.
An important embodiment of the invention consists in an apparatus for transforming applied forces into translational components along three mutually perpendicular axes and torque components about these three axes, the apparatus comprising a body to which the force is applied, three connecting members attached to the body and extending away therefrom such that in a central position of the body remote connection points on the respective connection members lie along respective reference axes extending from a central point of the body, these reference axes being mutually perpendicular, respective leg means being pivotally connected to the respective connection members at said connection points through universal joints of limited range and motion, biasing means being provided to bias the connecting members towards the central position and sensor means for sensing displacement of each connecting member and/or each connecting leg whereby the nature of the applied force may be determined.
12~Z66~
For this important embodiment an effective mechanical design is one in which the body is a ball-like member and each of the connecting members is generally L-shaped and extends in a plane at right angles to the corresponding leg member, the S arm of the L connected to the ball-like member estending through the ball mem~er and being pi~otable ~bout its own asis which e~tends at right angles to the leg member and at right angles to the reference asis of the connecting ~ember, anB the other leg of the L having a universal joint located upon the reference a~is.
To facilitate a stable and durable mounting, the arm of the leg of each connecting member passing through the ball-like body can be of a cranked design to permit overlapping of the three respective arms.
Preferably, the sensor means associated with each connecting member is arranged to operate substantially in a plane and is arranged to monitor motion transverse to the reference axis of the connecting member and motion along the reference axis.
- 20 Where the device has three reference axes, rotation of the body about a first axis will cause displacement at the sensors mounted by a connecting members having reference axes perpendicular to the axis about which rotation takes place.
This is due to an applied couple; there are equal and opposite reactions.
Since the invention will normally be applied in a situation in which only small motions are monitored, references to planes and motion in planes (although representing an ideal situation) will not necessarily precisely describe the motion which in fact occurs. The motion which occurs in one embodiment is planar, but in other embodiments is over a small portion of a near-spherical surface, but for the small motions envisaged, these motions can be treated in practice as essentially planar motions and will be described in this specification as being planar.
Preferably, each sensor has a planar plate and motion is detected by a light emitting means and light detecting means.
129Z6~1 Advantageously a data processing means collates the detected movements of the three sensor plates and produces a signal representative of the effort applied to the body of the apparatus, which may comprise translational motion, rotational motion or combinations thereof.
RIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described by way of esample only with reference to the accompanying drawings in which:
Figure 1 is a schematic view of a first embodiment of the invention;
Figure 2 is a plan view of the first embodiment in practical form with the top of the spherical hand grip removed;
Figure 3 is a partially broken away side-view of the first embodiment with the top of the hand grip removed and the front portion of the arm structure in the middle region just above the central plane omitted;
Figure 4 is a perspective view illustrating the principles of a second embodiment in which the mounting structure is directed externally from the hand grip arrangement;
Figure 5 is a sectional elevational view of a practical embodiment corresponding to Figure 4 and looking along the Y
direction at the device as seen in the X-Z plane;
Figure 6 is a plan view of the embodiment of Figure 5;
Figure 7 is an enlarged view of a preferred form of mounting for the respective legs of the embodiment of Figures 5 and 6;
Figure 8 is an elevation of the embodiment of Figure 7;
Figure 9 is an inverted plan view of the embodiment of Figure 7;
Figure 10 is a plan view of an alternative embodiment of connecting arm for use with the operator hand grip shown in Figures 12 and 13 and corresponding to the arms 33A, 33~ and 33C of Figures 4 to 6;
~}Z6t;~
Figure 11 is an elevation of the mounting arm of Figure 10;
Figure 12 is an a~ial cross-sectional ~levation of a ball like operators hand grip for use with mounting arms as in Figures 10 and 11 in an apparatus functioning in a manner equivalent to Figures 4 to 6; and Figure 13 is an inverted plan view of the operator's grip shown in Figure 12.
- The theory behind the operation of the first embodiment can ~e more easily understood by referring to the schematic diagram of Figure 1 which illustrates an embodiment with the mounting arrangement internally disposed relative to an operator~s hand grip. Three pairs of leaf-spring elements lOA, lOB and lOC are attached to a metal base 8 and e~tend in three mutually perpendicular planes; the center lines of the leaf-spring elements intersect at the centre of the base 8, and extend respectively along X, Y and Z ases.
The leaf-spring elements lOA, lOB and lOC are substantially of the same length and each leaf-spring element has at the end distant from the base 8, a ball-like tip llA, llB and llC which lies within a respective slot 12A, 12B and 12C in a hand grip 9 represented by a frame. Each slot provides constraint of the corresponding tip against movement relative to the grip in a direction perpendicular to the plane of the corresponding leaf spring. Thus, for esample a displacement force applied to the grip 9 along the Z asis causes bending of the leaf-springs lOB only and strain gauges (not shown) measure the bending so that a signal corresponding to the displacement force can be produced. Each tip has a freedom of motion relative to the grip 9 in the plane of the corresponding leaf-spring. Thus, displacement of the hand grip along the direction of elongation of a leaf-spring, or across the direction of the leaf-spring does not result in any bending of the leaf-spring.
A displacement force at an angle to each of the a~es is resolved into corresponding bending components in all leaf-spring elements.
-`-` l.Z92~i6~
Similarly, a torque applied to the hand grip is resolved into corresponding couples about the respective X, Y and Z
ases. For e~ample, torque about the Z a~is causes equal and opposite bending of the leaf-springs lOA as the respective tips are deflected.
Forces applied along each of the ases and torques applied about each of the a~es can be eguated as follows:
FX ~ Rl ~ ~2 TX ~ R5 - R6 Fy . R3 + R4 Ty - Rl - R2 Fz , R5 ~ R6 ~z , R3 - R4 where FI represents a force in the I direction, ~I
represents a torgue about the I axis and Rl to R6 represent relative displacements in the directions indicated.
When a force is applied to the hand grip 9 in the X
direction, there is a corresponding slight bending of one pair of leaf-spring elements lOC such that one element of the pair bends a distance equal to Rl and the other element bends a distance equal to R2. The resultant force in the X direction is thus given by Fx = Rl + R2.
Similarly, if a torque is applied about the Y axis, one of the leaf-springs of a leaf-spring pair lOC bends and produces a displacement of Rl, while the other leaf-spring of the same pair bends and produces a displacement of R2 in the opposite direction. The resultant displacement about the Y
axis is thus given by ~y = Rl - R2. The remaining forces and torques are calculated in a similar manner.
In practice an apparatus as shown in Figures 2 and 3 is used to implement the principles shown by the schematic diagram of Figure 1 in which like parts have been given like reference numerals. ~he sensing apparatus is supported by a fixed supporting rod 3 above a ground plane, the rod connecting to a central mounting block 8. A force or torque applied by an operator's hand placed on a spherical hand grip 9 is converted into its individual mutually perpendicular components by means of an optical detector. In this embodiment each of the X, Y and Z leaf-spring elements consists of a pair of flat resilient metal strips spaced apart lZ~Z6~
and secured by screws 7 to opposite faces of the central cubic mounting bloc~ 8 and at their remote ends the ~trips are interconnected b~ a connector 13 having screws which also attaches an end fitting 14. The end fitting 14 has an asially e~tending shaft terminating in the ball like tip lLA, llB or llC.
In this em~odiment, the optical detector associated with each leaf-spring comprises a light emitting diode ~LED) 2 and a photodiode 3 fi~edly mounted on a bracket 4. Each bracket is mounted on a respective mounting bar 6 secured by screws 7 to the central bloc~ 8, with a packing block 6A and the central part of the leaf-spring element being sandwiched between the mounting bar 6 and the central block 8. A shutter 5 is attached to the end fitting 14(which interconnects the leaf-spring metal strips) and thus movement of the shutter alters the e~tent to which the radiation of the LED 2 can fall on the photodiode 3. Thus displacement is determined by alteration of current in electrical circuitry. Each photodiode is connected through wiring for electronic circuitry where the necessary computation of force and torque takes place.
Referring to Figure 4, a second embodiment is shown wherein a hand grip 30 is represented by a mounting ball 31 to which shafts 31A, 31B and 31C are affiYed. The hand grip 30 is mounted through a set of three L-shaped mounting structures pivotally mounted on the respective mutually perpendicular shafts. The mounting structures comprise V-shaped arm members 33A, 33B and 33C and respective leg members 32A, 32B and 32C
which connect the hand grip 30 to a base 34.
Each of the arm members 33A, 33B and 33C is V-shaped and hingably connected to the corresponding shafts 31A, 31B and 31C for pivotal motion respectively about the X, Z and Y
aYes. Each of the arm members is connected to a respective leg member 32A, 32B and 32C through a ball joint 35 which provides a limited range of universal relative motion. The base of each leg member is fixed to the base 34 and includes a narrow portion 36 near the base to provide a region of preferential bending. Each leg is of a spring metal material and has inherent resilience biasing the leg to the position shown in the drawing.
In use a force and or torque applied to the grip 30 results, in the general case, in a displacement of each of the respective arm-leg member connections and in particular displacement at the respective ball joints is detected. In a practical embodiment a detection plate assembly would be mounted near each ball joint to enable accurate measurements of deflection in a substantially planar surface perpendicular to the asis of the respective leg 32A, 328 or 32C. It can be shown that ths force and torque components applied to the grip can be calculated from the respective displacements by the following equations:
FX = Rl ~ R2 TX = -R3 Fy = R3 ~ R4 Ty = -R5 Fz = R5 ~ R6 Tz = -Rl where FI is a force applied in the I direction, TI is a torque applied about the I axis and Rl to R6 represent the relative displacements of each respective ball joint as sh~wn in the drawing.
The schematic diagram shown in Figure 4 is useful for understanding the principles behind the operation of the second embodiment: however, a construction as shown in Figures 5 and 6 is a practical embodiment.
The complexities associated with the construction of the second embodiment can be more readily understood by considering one of its mutually perpendicular planes. Thus referring to Figure 5, an X-Z plane is shown with the Y asis perpendicular to the plane of the paper. The apparatus hcs corresponding construction and function when considered ir~
either of the other two perpendicular planes. In the embodiment of Figures 5 and 6 the same reference numerals have been used for the parts corresponding to the structure shown in Figure 4.
Figure 5 is an axial section through the ball-like g-ip 30 which is adapted to fit comfortably in the operator's lZ92661 hand. The hinges represented by the mounting shafts 31A, 31B, 31C of Figure 4 are replaced by respective cranked cross-shafts 31~, 31B and 31C which o~tend from just one side of the ball grip 30 and comprise part of the respective arms 33A, 33B and 33C. The cranked profile of each ~haft is to permit the three mutually perpendicular ~hafts to pa~s diametrically through the ball and to cross over one another thereby permitting the shafts to be rotatably mounted ~t each end at bearing points 40 within the ball grip. ~he free end of each shaft is secured by a screw 45 and washer 44, a part spherical cap 46 being secured over the free end of the shaft by screws 43.
Each ball joint 35 comprises a part-spherical ball member 35A mounted on the leg 32A, 32B and 32C with a corresponding tip element 35B (with a part-spherical cavity) mounted on the end of the respective arms 33A, 33B and 33C. A screw threaded e~tension 35C extends beyond the ball joint from the leg and the ball joint is assembled by a first securing nut 38. A
sensor assembly 39 is then fixed on the screw threaded e~tension and secured in place by a second nut 41.
The sensor plate assembly 39 mounted on the end of arm 33B extends generally in the X-Z plane. The sensor plate 39 is of opaque material and is adapted to interrupt to a variable and partial extent the passage of light from light sources 42 which are directed towards light dependant resistors 47.
Reference will now be made to Figure 7 to 9 which show a preferred and alternative mounting arrangement for the respective legs of the embodiment of Figures 4 to 6. One mounting unit is shown in each of Figures 7 to 9 and has the general feature of providing true displacement in a plane, whereas in the arrangement of Figures 4 to 6 the displacement is in a very small arc of a sphere and is thus not true planar motion and very small errors are introduced into the results obtained.
In Figures 7 to 9 the parts for mounting the ball grip corresponding to leg-arm combination 32A, 33A are shown; like 12~2661 reference numerals are used or like parts.
A rigid base plate 34 is adapted to be fixed to a rigid mount so as not to move in space. The mounting arm 33A is pivotally connected to the hand grip (not shown) and is connected to the base plate 34 through a resiliently displacable mounting leg arrangement; the ~rm has a ball joint including a ball 35A estending from the arm 33A and engaged in a seat of the mounting leg arrangment. This leg arrangement comprises a generally pear-shaped rigid plate 32A providing a seat for the ball 35A, a first set of spring legs 36A, a rigid connecting disX 36~ and secondary spring legs 36C estending parallel to the first set of legs and connected to the base 34. The respective sets of legs are alternately spaced equally around a circular path and thus form essentially a ~ ples spring structure. Any motion of the mounting arm 33A
~n a plane parallel to the plate 32A causes the three spring legs 36A to be bent resiliently into a shallow S-shape, reaction occurs through the disk 36B, and the secondary legs 36C bend resiliently into a corresponding S-shape bent in the opposite direction. Thus, an applied force to the hand qrip 30 causing displacement of the arm 33A in the relevant plane causes motion of the plate 32A and thus motion of an attached shutter 39 in;a parallel plane thereto. Displacement is detected by the degree of interruption of a light source (not shown) inpinging on photodiodes 47.
From Figure 8 it will be seen that the shutter 39 has operating edges 39a and 39b extending at right angles so that displacement in the plane is resolved in two components. The shutter is mounted on a mounting shaft 39c extending from the pear-shaped plate 32A through an aperture in the rigid base 34, the rigid base carrying the photodiodes.
Figure 7 shows most clearly respective bosses 36D through which the resilient legs 36A ex~end, these bosses estending into respective apertures in the base 34. Any excessive movement of the arm 33A causes one or more of the bosses to abut the wall of the corresponding aperture thereby providing a limit to movement.
125~Z661 An alternative and advantageous embodiment is a variation on that of Figures 4 to 6 and wherein the mounting arm is formed as shown in Figures 10 and 11 and the hand grip is as formed in Figures 12 and 13. The operating principles are the same, but the construction has advantages.
As shown in Figures 10 and 11, the mount~ng arm referenced 33A has a generally Y-shaped physical form having respective ends 50, 51 and 52. End 50 has, e~tending laterally therefrom, the ball 35A for connection to the mounting leg (or plate 32A as shown in Figure 9), End 51 terminates in a sleeve like tip 51a with an aperture e~tending therethrough (along the X asis) and aligned with a small bore estending obliquely through the tip region of the arm 52.
The hand grip shown in Figures 12 and 13 is of plastics material and has a spherical ball-shaped head and a circular base plate 30a, and is adapted to be connected to a set of three arms of the type shown in Figures 10 and 11. The base plate 30a has a series of three spaced inclined bores 30b e~tending from chamfered surfaces and respectively along X, Y
and Z a~es of the apparatus. A series of three a~ially aligned corresponding bores 30c are provided in the top portion of the spherical head. Figure 12 shows a section along the X asis. The arm end 51 of the mounting arm of Figure 10 and 11 is secured by a bolt to the tapped bore 30b and the end 52 of the arm is inserted through a corresponding interior bore 30d in the spherical head so that the tip of the arm has its oblique bore aligning with the bore 30c for accommodating a securing pin. The pin is threadably engaged in the bore 30c, but is a s~iding fit in the oblique bore in the arm end 52.
Thus, the mounting arm has a limited freedom to rotate about the X asis at its connection with the ball-shaped head and freedom about the Z-axis at its connection with the mounting leg arrangement, as conceptually shown in Figure 4.
Therefore, any displacement force on the ball-shaped head and along the X asis or a torque about the X axis results in no displacement of mounting leg 32A associated with arm 33A but lZ926 61 in either case the other mounting legs may be displaced and thus the motion detected.
The ball-shaped head includes a central interior bore 30e for clearance purposes for the respective arm ends 52.
The invention can be applied to the control of an industrial robot, whereby pushing and twisting motions of the operator' 8 hand on the grip 30 causes corresponding motions at the respective sensor plate assembly and by computation in accordance wath the above eguations the applied forces ana torgues can be determined. This permits corresponding motion to be controlled in the robot.
A further advantageous application of the present invention, in general, e~ploits the ability of embodiments of the invention to detect and measure orce and/or torque applied relative to two parts. An illustrative e~ample is the case of a connection between two aircraft flying in formation and connected by a refueling device. The invention could be incorporated in a coupling whereby the relative applied translational forces and torques between the two aircraft are detected and monitored and indeed in a sophisticated application this might cause the control systems of the aircraft to automatically compensate as may be necessary to keep the applied forces and torques within allowable ranges.
The present invention relates to a force and torque converter and has useful applications in a wide field of activities particularly where a manual motion ~s to be converted into a cont~ol ~signal~. For esample, machines such as industrial robots, back hoes and computer graphic works~ations have comples control reguirements.
BAC~QUND TO THE IEY~TIQ~
In esisting systems, control of a vehicle such as a back hoe is achieved by manipulation of levers and more ~ecently by joy sticks. In computer applications joy sticks are a common control system but a computer may also employ a ~track ball"
or a ~mouse~. These devices have limited directions of motion ~ and accordingly limited commands only are possible.
In addition to a control system, there is also a need for a sensing system to monitor applied forces and torques; an esample of such a sensor system is a system for monitoring applied forces and torques with respect to three a~es in a manipulator (see United States Patent 3 921 445 Hill and Sword). In that specification the manipulator is of a hand like form comprising a pair of jaws which are relatively pivotally movable under operation of an electric motor. The manipulator is defined as having a wrist and sensing means are provided for sensing the magnitude and direction of forces along three mutually orthoganal a~es intersecting at the wrist and for sensing the magnitude and direction of torques about the axes. The form of the sensing means is a series of sensors extending around the longitudinal asis of the manipulator.
~SUMMARY OF THE INVE~TION
In one aspect, the present invention consists in an apparatus for providing output signals for use as command 129Z~iGl fiignals with respect to X, Y and Z mutually osthogonal a~es, the signals being representative of a translational applied force and an applied torque, the apparatus comprising a ~ase, a body to which the forces and tor~ues are applied, resilient S connecting means attached to the body and mounting the body for receiving force in any direction ana torque about any asis and for resiliently resisting displacement of the body from a normal position relative to the base, and sensor means arranged to detect a response to and to provide said output signals corresponding to components of an applied torque and components of an applied translational force with respect to said ases, and wherein said sensor means comprise either (a) a sis sensor unit configuration arranged in a three dimensional substantially uniform array with respect to said X, Y and Z
ases, the sensor units being arranged in pairs for detecting displacement along a respective operating axis, a first pair of said sensor units having an operating a~is in the X
direction, a second pair of said sensor units having an operating asis in the Y direction and a third pair of said sensor units having an operating asis in the ~ direction, each of the sensor units being non-responsive to any displacement at right angles to its operating axis, whereby the output signals may be processed to provide a command signal corresponding to any applied torque or any applied translational force, cr (b) a four sensor unit configuration arranged in two pairs and in accordance with two of the three pairs of sensor units in said six sensor unit configurat;on.
In the preferred embodiments described below, a very small displacement results from each of the translational force and applied torque, the connecting means being biased ~o a central position. However, it is possible to embody the invention in a form in which no displacement takes place and instead sensors respond whereby a signal is derived representative of the force or torque tending to cause displacement at each sensor. For example, a system in which automatic control causes the input of some energy to resist the displacement could be used, the input of energy having a lZg2~1 corresponding signal generated for indicating the magnitude of the applied force.
The invention is especially ~aluabl~ in permitting embodiments in which the applied translational force and/or the applied torque are respectively resolved into components with respect to most prefera~ly three mutually ~erpendicular ases. Hereinafter the invention will be e~emplifed with reference to the most comples esample ~n which a three dimensional device is utilised and it w;ll be appreciated that a comples ergonomically designed contro~ system can utilise an apparatus of this form. It is envisage~ that for many applications a handle or grip for an operator will be provided and this grip is adapted to receive a t~nslational force and a torque, the translational force being applied in any direction and the torque being about a~ desired a~is. The output signals can be used to control a~y required device and sophisticated control of, for esample, a machine can be achieved with just one control member. ~his can be very important for the control of complex ma~hines which require an operator to use a multiplicity of separ~ite levers for controlling, e.g. hydraulic circuits. ~nother area in which there may be very beneficial applicatio~3 is for control of devices for handicapped persons.
In a preferred embodiment the appa~tus is such that only at most very small displacement results from the applied translational force and~or torque. In ~;he mechanical examples described hereinafter the mathematical ~rror resulting from displacement is at most exceedingly sma~l and may be disregarded for very small angles of di$placement.
In one specific embodiment, the fi~ed base has a portion at which the X, Y and Z axes intersect and the connecting means comprise respective pairs of resiliently deformable connecting arms extending in the Z and ~ directions, the arms of each pair extending away from the ba~se portion in opposite directions to be connected to the body, and wherein the sensor means are adapted to detect a displacement in the respective connecting arms and provide signals permitting computation of 12gZ661 the applied torque and/or force, the sensor means detecting torque about the Y axis or displacement in the X direction at respective locations in the arms e~tending in the Z direction on opposite sides of the X axis, and detecting torgue about the X a~is or displacement in the Z direction at respective locations ~n the connecting arms e~tending in the Y direction on opposite sides of the Z a~is.
Preferably, ~he apparatus described in the previous para~raph is such that the remote ends of said arms are constrained against movement in second and third mutually perpendicular a~es, which are each perpendicular to said first asis.
When the embodiment of the preceding paragraph is applied to a three dimensional version, then the connecting means comprises three pairs of arms eYtending mutually perpendicularly and co-operating with the body so that the respective pairs of arms are constrained about respective mutually perpendicular axes.
Apparatus according to the invention preferably includes signal processing means for processing the signals detected at the respective sensor means whereby output signals correspond with the applied torque and the applied translational force and, in the case of a three dimensional version of the invention, the output signals represent the resolution of the applied force and applied torque with respect to three mutually perpendicular axis.
A second important embodiment of the invention is one in which the connecting means comprises a series of three connecting structures each comprising an arm extending from the body and pivotally connected through a joint having universal action through at least a limited range of angles to a leg, the leg extendinq normally in a direction substantially at right angles to the arm to be attached to the fi~ed base, the biasing means biasing the leg to a central position and the leg having an ability to move aqainst the biasing in a plane being substantially that containing the pivot point of the universal joint and substantially perpendicular to the axis of the leg.
Preferably, a universal joint providing a limited range of motion is used for the pivotal connection between the leg and the arm.
Preferably, the apparatus is arranged such that each of arms of the connecting structur~s has its pivotal connection with its leg member 6uch that a reference a~is of the connecting member extends rom a central point in the body through the pivotal connection and this reference a~is is substantially at right angles to the asis along which displacement is sensed by displacement of the pivotal connection.
Preferably, each leg member is arranged to e~tend at right angles to the reference asis of the associated connecting member, the remote end of the leg member being fixed.
Preferably, the biasing means includes resilient deformability provided in the leg member and for this purpose preferably a reduced diameter portion is provided in the leg member near its remote fixed end.
An important embodiment of the invention consists in an apparatus for transforming applied forces into translational components along three mutually perpendicular axes and torque components about these three axes, the apparatus comprising a body to which the force is applied, three connecting members attached to the body and extending away therefrom such that in a central position of the body remote connection points on the respective connection members lie along respective reference axes extending from a central point of the body, these reference axes being mutually perpendicular, respective leg means being pivotally connected to the respective connection members at said connection points through universal joints of limited range and motion, biasing means being provided to bias the connecting members towards the central position and sensor means for sensing displacement of each connecting member and/or each connecting leg whereby the nature of the applied force may be determined.
12~Z66~
For this important embodiment an effective mechanical design is one in which the body is a ball-like member and each of the connecting members is generally L-shaped and extends in a plane at right angles to the corresponding leg member, the S arm of the L connected to the ball-like member estending through the ball mem~er and being pi~otable ~bout its own asis which e~tends at right angles to the leg member and at right angles to the reference asis of the connecting ~ember, anB the other leg of the L having a universal joint located upon the reference a~is.
To facilitate a stable and durable mounting, the arm of the leg of each connecting member passing through the ball-like body can be of a cranked design to permit overlapping of the three respective arms.
Preferably, the sensor means associated with each connecting member is arranged to operate substantially in a plane and is arranged to monitor motion transverse to the reference axis of the connecting member and motion along the reference axis.
- 20 Where the device has three reference axes, rotation of the body about a first axis will cause displacement at the sensors mounted by a connecting members having reference axes perpendicular to the axis about which rotation takes place.
This is due to an applied couple; there are equal and opposite reactions.
Since the invention will normally be applied in a situation in which only small motions are monitored, references to planes and motion in planes (although representing an ideal situation) will not necessarily precisely describe the motion which in fact occurs. The motion which occurs in one embodiment is planar, but in other embodiments is over a small portion of a near-spherical surface, but for the small motions envisaged, these motions can be treated in practice as essentially planar motions and will be described in this specification as being planar.
Preferably, each sensor has a planar plate and motion is detected by a light emitting means and light detecting means.
129Z6~1 Advantageously a data processing means collates the detected movements of the three sensor plates and produces a signal representative of the effort applied to the body of the apparatus, which may comprise translational motion, rotational motion or combinations thereof.
RIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described by way of esample only with reference to the accompanying drawings in which:
Figure 1 is a schematic view of a first embodiment of the invention;
Figure 2 is a plan view of the first embodiment in practical form with the top of the spherical hand grip removed;
Figure 3 is a partially broken away side-view of the first embodiment with the top of the hand grip removed and the front portion of the arm structure in the middle region just above the central plane omitted;
Figure 4 is a perspective view illustrating the principles of a second embodiment in which the mounting structure is directed externally from the hand grip arrangement;
Figure 5 is a sectional elevational view of a practical embodiment corresponding to Figure 4 and looking along the Y
direction at the device as seen in the X-Z plane;
Figure 6 is a plan view of the embodiment of Figure 5;
Figure 7 is an enlarged view of a preferred form of mounting for the respective legs of the embodiment of Figures 5 and 6;
Figure 8 is an elevation of the embodiment of Figure 7;
Figure 9 is an inverted plan view of the embodiment of Figure 7;
Figure 10 is a plan view of an alternative embodiment of connecting arm for use with the operator hand grip shown in Figures 12 and 13 and corresponding to the arms 33A, 33~ and 33C of Figures 4 to 6;
~}Z6t;~
Figure 11 is an elevation of the mounting arm of Figure 10;
Figure 12 is an a~ial cross-sectional ~levation of a ball like operators hand grip for use with mounting arms as in Figures 10 and 11 in an apparatus functioning in a manner equivalent to Figures 4 to 6; and Figure 13 is an inverted plan view of the operator's grip shown in Figure 12.
- The theory behind the operation of the first embodiment can ~e more easily understood by referring to the schematic diagram of Figure 1 which illustrates an embodiment with the mounting arrangement internally disposed relative to an operator~s hand grip. Three pairs of leaf-spring elements lOA, lOB and lOC are attached to a metal base 8 and e~tend in three mutually perpendicular planes; the center lines of the leaf-spring elements intersect at the centre of the base 8, and extend respectively along X, Y and Z ases.
The leaf-spring elements lOA, lOB and lOC are substantially of the same length and each leaf-spring element has at the end distant from the base 8, a ball-like tip llA, llB and llC which lies within a respective slot 12A, 12B and 12C in a hand grip 9 represented by a frame. Each slot provides constraint of the corresponding tip against movement relative to the grip in a direction perpendicular to the plane of the corresponding leaf spring. Thus, for esample a displacement force applied to the grip 9 along the Z asis causes bending of the leaf-springs lOB only and strain gauges (not shown) measure the bending so that a signal corresponding to the displacement force can be produced. Each tip has a freedom of motion relative to the grip 9 in the plane of the corresponding leaf-spring. Thus, displacement of the hand grip along the direction of elongation of a leaf-spring, or across the direction of the leaf-spring does not result in any bending of the leaf-spring.
A displacement force at an angle to each of the a~es is resolved into corresponding bending components in all leaf-spring elements.
-`-` l.Z92~i6~
Similarly, a torque applied to the hand grip is resolved into corresponding couples about the respective X, Y and Z
ases. For e~ample, torque about the Z a~is causes equal and opposite bending of the leaf-springs lOA as the respective tips are deflected.
Forces applied along each of the ases and torques applied about each of the a~es can be eguated as follows:
FX ~ Rl ~ ~2 TX ~ R5 - R6 Fy . R3 + R4 Ty - Rl - R2 Fz , R5 ~ R6 ~z , R3 - R4 where FI represents a force in the I direction, ~I
represents a torgue about the I axis and Rl to R6 represent relative displacements in the directions indicated.
When a force is applied to the hand grip 9 in the X
direction, there is a corresponding slight bending of one pair of leaf-spring elements lOC such that one element of the pair bends a distance equal to Rl and the other element bends a distance equal to R2. The resultant force in the X direction is thus given by Fx = Rl + R2.
Similarly, if a torque is applied about the Y axis, one of the leaf-springs of a leaf-spring pair lOC bends and produces a displacement of Rl, while the other leaf-spring of the same pair bends and produces a displacement of R2 in the opposite direction. The resultant displacement about the Y
axis is thus given by ~y = Rl - R2. The remaining forces and torques are calculated in a similar manner.
In practice an apparatus as shown in Figures 2 and 3 is used to implement the principles shown by the schematic diagram of Figure 1 in which like parts have been given like reference numerals. ~he sensing apparatus is supported by a fixed supporting rod 3 above a ground plane, the rod connecting to a central mounting block 8. A force or torque applied by an operator's hand placed on a spherical hand grip 9 is converted into its individual mutually perpendicular components by means of an optical detector. In this embodiment each of the X, Y and Z leaf-spring elements consists of a pair of flat resilient metal strips spaced apart lZ~Z6~
and secured by screws 7 to opposite faces of the central cubic mounting bloc~ 8 and at their remote ends the ~trips are interconnected b~ a connector 13 having screws which also attaches an end fitting 14. The end fitting 14 has an asially e~tending shaft terminating in the ball like tip lLA, llB or llC.
In this em~odiment, the optical detector associated with each leaf-spring comprises a light emitting diode ~LED) 2 and a photodiode 3 fi~edly mounted on a bracket 4. Each bracket is mounted on a respective mounting bar 6 secured by screws 7 to the central bloc~ 8, with a packing block 6A and the central part of the leaf-spring element being sandwiched between the mounting bar 6 and the central block 8. A shutter 5 is attached to the end fitting 14(which interconnects the leaf-spring metal strips) and thus movement of the shutter alters the e~tent to which the radiation of the LED 2 can fall on the photodiode 3. Thus displacement is determined by alteration of current in electrical circuitry. Each photodiode is connected through wiring for electronic circuitry where the necessary computation of force and torque takes place.
Referring to Figure 4, a second embodiment is shown wherein a hand grip 30 is represented by a mounting ball 31 to which shafts 31A, 31B and 31C are affiYed. The hand grip 30 is mounted through a set of three L-shaped mounting structures pivotally mounted on the respective mutually perpendicular shafts. The mounting structures comprise V-shaped arm members 33A, 33B and 33C and respective leg members 32A, 32B and 32C
which connect the hand grip 30 to a base 34.
Each of the arm members 33A, 33B and 33C is V-shaped and hingably connected to the corresponding shafts 31A, 31B and 31C for pivotal motion respectively about the X, Z and Y
aYes. Each of the arm members is connected to a respective leg member 32A, 32B and 32C through a ball joint 35 which provides a limited range of universal relative motion. The base of each leg member is fixed to the base 34 and includes a narrow portion 36 near the base to provide a region of preferential bending. Each leg is of a spring metal material and has inherent resilience biasing the leg to the position shown in the drawing.
In use a force and or torque applied to the grip 30 results, in the general case, in a displacement of each of the respective arm-leg member connections and in particular displacement at the respective ball joints is detected. In a practical embodiment a detection plate assembly would be mounted near each ball joint to enable accurate measurements of deflection in a substantially planar surface perpendicular to the asis of the respective leg 32A, 328 or 32C. It can be shown that ths force and torque components applied to the grip can be calculated from the respective displacements by the following equations:
FX = Rl ~ R2 TX = -R3 Fy = R3 ~ R4 Ty = -R5 Fz = R5 ~ R6 Tz = -Rl where FI is a force applied in the I direction, TI is a torque applied about the I axis and Rl to R6 represent the relative displacements of each respective ball joint as sh~wn in the drawing.
The schematic diagram shown in Figure 4 is useful for understanding the principles behind the operation of the second embodiment: however, a construction as shown in Figures 5 and 6 is a practical embodiment.
The complexities associated with the construction of the second embodiment can be more readily understood by considering one of its mutually perpendicular planes. Thus referring to Figure 5, an X-Z plane is shown with the Y asis perpendicular to the plane of the paper. The apparatus hcs corresponding construction and function when considered ir~
either of the other two perpendicular planes. In the embodiment of Figures 5 and 6 the same reference numerals have been used for the parts corresponding to the structure shown in Figure 4.
Figure 5 is an axial section through the ball-like g-ip 30 which is adapted to fit comfortably in the operator's lZ92661 hand. The hinges represented by the mounting shafts 31A, 31B, 31C of Figure 4 are replaced by respective cranked cross-shafts 31~, 31B and 31C which o~tend from just one side of the ball grip 30 and comprise part of the respective arms 33A, 33B and 33C. The cranked profile of each ~haft is to permit the three mutually perpendicular ~hafts to pa~s diametrically through the ball and to cross over one another thereby permitting the shafts to be rotatably mounted ~t each end at bearing points 40 within the ball grip. ~he free end of each shaft is secured by a screw 45 and washer 44, a part spherical cap 46 being secured over the free end of the shaft by screws 43.
Each ball joint 35 comprises a part-spherical ball member 35A mounted on the leg 32A, 32B and 32C with a corresponding tip element 35B (with a part-spherical cavity) mounted on the end of the respective arms 33A, 33B and 33C. A screw threaded e~tension 35C extends beyond the ball joint from the leg and the ball joint is assembled by a first securing nut 38. A
sensor assembly 39 is then fixed on the screw threaded e~tension and secured in place by a second nut 41.
The sensor plate assembly 39 mounted on the end of arm 33B extends generally in the X-Z plane. The sensor plate 39 is of opaque material and is adapted to interrupt to a variable and partial extent the passage of light from light sources 42 which are directed towards light dependant resistors 47.
Reference will now be made to Figure 7 to 9 which show a preferred and alternative mounting arrangement for the respective legs of the embodiment of Figures 4 to 6. One mounting unit is shown in each of Figures 7 to 9 and has the general feature of providing true displacement in a plane, whereas in the arrangement of Figures 4 to 6 the displacement is in a very small arc of a sphere and is thus not true planar motion and very small errors are introduced into the results obtained.
In Figures 7 to 9 the parts for mounting the ball grip corresponding to leg-arm combination 32A, 33A are shown; like 12~2661 reference numerals are used or like parts.
A rigid base plate 34 is adapted to be fixed to a rigid mount so as not to move in space. The mounting arm 33A is pivotally connected to the hand grip (not shown) and is connected to the base plate 34 through a resiliently displacable mounting leg arrangement; the ~rm has a ball joint including a ball 35A estending from the arm 33A and engaged in a seat of the mounting leg arrangment. This leg arrangement comprises a generally pear-shaped rigid plate 32A providing a seat for the ball 35A, a first set of spring legs 36A, a rigid connecting disX 36~ and secondary spring legs 36C estending parallel to the first set of legs and connected to the base 34. The respective sets of legs are alternately spaced equally around a circular path and thus form essentially a ~ ples spring structure. Any motion of the mounting arm 33A
~n a plane parallel to the plate 32A causes the three spring legs 36A to be bent resiliently into a shallow S-shape, reaction occurs through the disk 36B, and the secondary legs 36C bend resiliently into a corresponding S-shape bent in the opposite direction. Thus, an applied force to the hand qrip 30 causing displacement of the arm 33A in the relevant plane causes motion of the plate 32A and thus motion of an attached shutter 39 in;a parallel plane thereto. Displacement is detected by the degree of interruption of a light source (not shown) inpinging on photodiodes 47.
From Figure 8 it will be seen that the shutter 39 has operating edges 39a and 39b extending at right angles so that displacement in the plane is resolved in two components. The shutter is mounted on a mounting shaft 39c extending from the pear-shaped plate 32A through an aperture in the rigid base 34, the rigid base carrying the photodiodes.
Figure 7 shows most clearly respective bosses 36D through which the resilient legs 36A ex~end, these bosses estending into respective apertures in the base 34. Any excessive movement of the arm 33A causes one or more of the bosses to abut the wall of the corresponding aperture thereby providing a limit to movement.
125~Z661 An alternative and advantageous embodiment is a variation on that of Figures 4 to 6 and wherein the mounting arm is formed as shown in Figures 10 and 11 and the hand grip is as formed in Figures 12 and 13. The operating principles are the same, but the construction has advantages.
As shown in Figures 10 and 11, the mount~ng arm referenced 33A has a generally Y-shaped physical form having respective ends 50, 51 and 52. End 50 has, e~tending laterally therefrom, the ball 35A for connection to the mounting leg (or plate 32A as shown in Figure 9), End 51 terminates in a sleeve like tip 51a with an aperture e~tending therethrough (along the X asis) and aligned with a small bore estending obliquely through the tip region of the arm 52.
The hand grip shown in Figures 12 and 13 is of plastics material and has a spherical ball-shaped head and a circular base plate 30a, and is adapted to be connected to a set of three arms of the type shown in Figures 10 and 11. The base plate 30a has a series of three spaced inclined bores 30b e~tending from chamfered surfaces and respectively along X, Y
and Z a~es of the apparatus. A series of three a~ially aligned corresponding bores 30c are provided in the top portion of the spherical head. Figure 12 shows a section along the X asis. The arm end 51 of the mounting arm of Figure 10 and 11 is secured by a bolt to the tapped bore 30b and the end 52 of the arm is inserted through a corresponding interior bore 30d in the spherical head so that the tip of the arm has its oblique bore aligning with the bore 30c for accommodating a securing pin. The pin is threadably engaged in the bore 30c, but is a s~iding fit in the oblique bore in the arm end 52.
Thus, the mounting arm has a limited freedom to rotate about the X asis at its connection with the ball-shaped head and freedom about the Z-axis at its connection with the mounting leg arrangement, as conceptually shown in Figure 4.
Therefore, any displacement force on the ball-shaped head and along the X asis or a torque about the X axis results in no displacement of mounting leg 32A associated with arm 33A but lZ926 61 in either case the other mounting legs may be displaced and thus the motion detected.
The ball-shaped head includes a central interior bore 30e for clearance purposes for the respective arm ends 52.
The invention can be applied to the control of an industrial robot, whereby pushing and twisting motions of the operator' 8 hand on the grip 30 causes corresponding motions at the respective sensor plate assembly and by computation in accordance wath the above eguations the applied forces ana torgues can be determined. This permits corresponding motion to be controlled in the robot.
A further advantageous application of the present invention, in general, e~ploits the ability of embodiments of the invention to detect and measure orce and/or torque applied relative to two parts. An illustrative e~ample is the case of a connection between two aircraft flying in formation and connected by a refueling device. The invention could be incorporated in a coupling whereby the relative applied translational forces and torques between the two aircraft are detected and monitored and indeed in a sophisticated application this might cause the control systems of the aircraft to automatically compensate as may be necessary to keep the applied forces and torques within allowable ranges.
Claims (18)
1. An apparatus for providing output signals for use as command signals with respect to X, Y and Z mutually orthogonal axes, the signals being representative of a translational applied force and an applied torque, the apparatus comprising a base, a body to which the forces and torques are applied, resilient connecting means attached to the body and mounting the body for receiving force in any direction and torque about any axis and for resiliently resisting displacement of the body from a normal position relative to the base, and sensor means comprising a set of sensor units arranged to detect a response to and to provide said output signals corresponding to components of an applied torque and components of an applied translational force with respect to said axes, and characterised in that the connecting means resolves applied torque and force into detectable responses at six locations arranged in a three dimensional substantially uniform array with respect to said X, Y and Z axes, each of the six locations being adapted to have one of the sensor units, the sensor units being arranged in pairs for detecting displacement along a respective operating axis, a first pair of said sensor units having an operating axis in the X
direction, a second pair of said sensor units having an operating axis in the Y direction and a third pair of said sensor units having an operating axis in the Z direction, each of the sensor units being non-responsive to any displacement at right angles to its operating axis, whereby the output signals may be processed to provide a command signal corresponding to any applied torque or any applied translational force, and the apparatus further including at least four of such sensor units arranged in two pairs and providing two of the three pairs of sensor units which the apparatus is adopted to utilize.
direction, a second pair of said sensor units having an operating axis in the Y direction and a third pair of said sensor units having an operating axis in the Z direction, each of the sensor units being non-responsive to any displacement at right angles to its operating axis, whereby the output signals may be processed to provide a command signal corresponding to any applied torque or any applied translational force, and the apparatus further including at least four of such sensor units arranged in two pairs and providing two of the three pairs of sensor units which the apparatus is adopted to utilize.
2. Apparatus as claimed in claim 1 and wherein the resilient connecting means comprising a set of resilient connecting arm structures arranged in a three dimensional substantially uniform array with respect to said X, Y and Z
axes, and wherein the base has a portion at which the X, Y
and Z axes intersect and the connecting arm structures comprise respective pairs of resiliently deformable connecting arms extending in the X, Y and Z directions, the arms of each pair extending away from the base in opposite directions to be connected to the body, and wherein six of said sensor units are mounted at each of said locations and the sensor units are adapted to detect a displacement in the respective connecting arms and provide said output signals, the sensor units detecting torque about the Y axis or displacement in the X direction at respective locations in the arms extending in the Z direction on opposite sides of the X axis, and detecting torque about the X axis or displacement in the Z direction at respective locations in the connecting arms extending in the Y direction on opposite sides of the Z axis.
axes, and wherein the base has a portion at which the X, Y
and Z axes intersect and the connecting arm structures comprise respective pairs of resiliently deformable connecting arms extending in the X, Y and Z directions, the arms of each pair extending away from the base in opposite directions to be connected to the body, and wherein six of said sensor units are mounted at each of said locations and the sensor units are adapted to detect a displacement in the respective connecting arms and provide said output signals, the sensor units detecting torque about the Y axis or displacement in the X direction at respective locations in the arms extending in the Z direction on opposite sides of the X axis, and detecting torque about the X axis or displacement in the Z direction at respective locations in the connecting arms extending in the Y direction on opposite sides of the Z axis.
3. Apparatus as claimed in claim 2 wherein said sensor units include sensor elements associated with said resiliently deformable connecting arms which extend in the X
direction and which are adapted to respond to a translational force in the Y direction or to a torque about the Z axis.
direction and which are adapted to respond to a translational force in the Y direction or to a torque about the Z axis.
4. Apparatus as claimed in claim 3, wherein the respective connecting arms engage with portions of the body with respective freedoms of motion to a limited extent and respective constraints as follows:
X axis arms: constrained by interengagements in Y
direction, free in Z and X direction and free to rotate about X axis;
Y axis arms: constrained by interengagements in Z
direction, free in X and Y directions and free to rotate about Y axis;
Z axis arms: constrained by interengagements in X
direction, free in Y and Z directions, and free to rotate about Z axis.
X axis arms: constrained by interengagements in Y
direction, free in Z and X direction and free to rotate about X axis;
Y axis arms: constrained by interengagements in Z
direction, free in X and Y directions and free to rotate about Y axis;
Z axis arms: constrained by interengagements in X
direction, free in Y and Z directions, and free to rotate about Z axis.
5. Apparatus as claimed in claim 4, and wherein the body comprises a housing member having a portion of the fixed base generally centrally disposed therein with a mounting arm of the fixed base extending out through the housing, and the resiliently deformable connecting arms extending along the respective X, Y and Z axes from the fixed base portion to engage with the housing at respective locations, each of the connecting arms having a ball-like tip engaging in a corresponding slot in the housing.
6. Apparatus as claimed in claim 5, wherein each of the connecting arms is of spring strip-like material, the strips extending in the X, Y and Z directions having their respective planes at right angles to one another.
7. Apparatus as claimed in claim 5 and wherein the sensor means comprises a sensor element associated with each of the pair of connecting arms extending respectively along the X, Y and Z axes and adapted to monitor the resilient displacement thereof, each sensor element including a shutter element disposed normally to interupt partially a beam of electromagnetically radiation from a source to an electromagnetically sensitive electronic device which is adapted to be connected into a circuit, the electrical characteristics of the sensor element varying depending upon the amount of electromagnetic radiation incident thereon and thus corresponding to the position of the shutter element.
8. Apparatus as claimed in claim 1 and wherein the resilient connecting means comprising a set of resilient connecting arm structures arranged in a three dimensional substantially uniform array with respect to said X, Y and Z
axes, and wherein the connecting arm structures comprise a series of three connecting structures each comprising an arm extending from the body and pivotally connected to a leg through a joint having universal action through at least a limited range of angles, the leg extending normally in a direction substantially at right angles to an operating axis of the arm extending from the intersection of said X, Y and Z axes through said joint, said leg being attached to the base, and the sensor means being arranged to monitor either (a) displacements in the respective legs as follows:
the leg elongated in the X direction responds to displacement in the Z direction, the leg elongated in the Y director, responds to displacement in the Z direction and in the X direction, and the leg elongated in the Z direction responds to displacement in the X direction; or (b) displacements of the respective legs in respective planes at right angles to the directions in which the respective legs extend from said universal joint towards the base.
axes, and wherein the connecting arm structures comprise a series of three connecting structures each comprising an arm extending from the body and pivotally connected to a leg through a joint having universal action through at least a limited range of angles, the leg extending normally in a direction substantially at right angles to an operating axis of the arm extending from the intersection of said X, Y and Z axes through said joint, said leg being attached to the base, and the sensor means being arranged to monitor either (a) displacements in the respective legs as follows:
the leg elongated in the X direction responds to displacement in the Z direction, the leg elongated in the Y director, responds to displacement in the Z direction and in the X direction, and the leg elongated in the Z direction responds to displacement in the X direction; or (b) displacements of the respective legs in respective planes at right angles to the directions in which the respective legs extend from said universal joint towards the base.
9. Apparatus as claimed in claim 8 wherein the body further comprises a ball-like element and each connecting arm is a cranked arm having a minor portion mounting the arm on the body about a pivotal axis extending at right angles to the operating axis applicable to that arm and a major portion extending from a peripheral portion of the ball-like element to the universal joint and at an angle to the operating axis.
10. Apparatus as claimed in claim 8 wherein each mounting arm is of a generally Y-shaped form and has a member extending transversely from one end portion for forming the universal joint connection with the associated leg, and the remote ends of the other arms have respective cross bores which are coaxial for pivotal attachment through elongated fixing elements to the body, the body being of ball-like form and having an outwardly extending flanged base, one of said other arms being connected to the flanged base and the other arm being inserted within the bore within the ball-like body, the axes of the cross bores in the respective Y-shaped arms being located on the X, Y and Z
axes of the apparatus, and the axes intersecting at the centre of the ball-like body.
axes of the apparatus, and the axes intersecting at the centre of the ball-like body.
11. Apparatus as claimed in any one of claim 8 wherein each of the legs is in the form of a resilient connecting structure comprising a plate member forming a universal joint member for engaging with the mounting arm and a resilient leg structure extending at right angles to the plate member and biasing the plate member to a central position and permitting the resilient displacement of the plate member in its own plane, the sensor means being arranged to monitor the displacements in a direction parallel to the plane of the plate.
12. Apparatus as claimed in claim 11 and wherein each of said resilient connecting structures comprises a rigid base member adapted to be fixed in space and forming at least part of said base of the apparatus, a rigid connector, and an array of resilient pins spaced normally parallel to one another and located spaced around an axis extending from the rigid base member and substantially at right angles thereto, the pins comprising a first set of at least 3 pins fixed to the rigid base member and fixed to the rigid connector, and a second set of at least 3 pins extending from the rigid connector through respective apertures in the rigid base member to be connected to said plate member.
13. Apparatus as claimed in claim 10 and wherein each of the legs is in the form of a resilient connecting structure comprising a plate member forming a universal joint member for engaging with the mounting arm, and a resilient leg structure extending at right angles to the plate member and biasing the plate member to a central position and permitting the resilient displacement of the plate member in its own plane, the sensor means being arranged to monitor the displacements in a direction parallel to the plane of the plate.
14. Apparatus for transforming applied forces into translational components along three mutually perpendicular axes and torque components about these three axes, the apparatus comprising a body to which the force and torque may be applied, three connecting members attached to the body and extending away therefrom such that in a central position of the body remote connection points on the respective connecting members lie along respective reference axes extending from a central point of the body, these reference axes being mutually perpendicular, each of the connecting members being connected to the body with a respective different freedom of motion with respect to components of displacement of the body in two of three mutually orthogonal axes and responsive to displacement only in the third of the orthogonal axes, respective leg means being pivotally connected to the respective connecting members at said connection points through universal joints of at least limited range and motion, biasing means being provided to bias the connecting members towards the central position, and sensor means arranged in a substantially symmetric three dimensional array for sensing displacement of each connecting member and/or each leg means whereby the nature of the applied force and torque may be determined and a corresponding output signal provided.
15. An apparatus as claimed in claim 4 wherein each of said sensor means comprises a light emitting means and a light detecting means axially aligned substantially at right angles to the respective axis and a control mask connected to the respective connecting members and operable to vary the degree of interruption of light onto the light detecting means whereby the magnitude of the output signal is usable in determining the applied torque and/or applied force.
16. An apparatus as claimed in Claim 1 and wherein the apparatus mounts six sensor units, each of the sensor means being mounted with a respective limitation of response with regard to displacement responsive to any applied torque or force, the first offset sensor means responding to displacement in the X direction but not responding to displacement in the Y or Z directions, the second sensor means responding to displacement in the Y direction but not to displacement in the X or Z directions and the third sensor means responding to displacement in the Z direction but not to displacement in the X or Y directions.
17. An apparatus as claimed in Claim 16 wherein each sensor means comprises a shutter element, means producing a beam of electromagnetic radiation a detecting means align with the beam for detecting electromagnetic radiation and providing a signal corresponding to the incident radiation, the shutter element being mounted normally to interrupt partially beam and responsive to displacement produced as a component of an applied torque and/or applied force to vary the amount of the beam incident on the detecting means.
18. Apparatus as claimed in Claim 16 and wherein the body comprises a hounded housing substantially surrounding the base, the base having a mounting stem protruding from the housing to mount the apparatus.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000588461A CA1292661C (en) | 1989-01-17 | 1989-01-17 | Force and torque converter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000588461A CA1292661C (en) | 1989-01-17 | 1989-01-17 | Force and torque converter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292661C true CA1292661C (en) | 1991-12-03 |
Family
ID=4139471
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000588461A Expired - Fee Related CA1292661C (en) | 1989-01-17 | 1989-01-17 | Force and torque converter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1292661C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114173971A (en) * | 2019-05-28 | 2022-03-11 | 阿特拉斯·科普柯工业技术公司 | Power drill and force sensor for such a drill |
| CN116698259A (en) * | 2023-08-04 | 2023-09-05 | 锐马（福建）电气制造有限公司 | Three-dimensional four-axis multidimensional force sensor |
-
1989
- 1989-01-17 CA CA000588461A patent/CA1292661C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114173971A (en) * | 2019-05-28 | 2022-03-11 | 阿特拉斯·科普柯工业技术公司 | Power drill and force sensor for such a drill |
| CN114173971B (en) * | 2019-05-28 | 2023-09-22 | 阿特拉斯·科普柯工业技术公司 | Power drill and force sensor for such a drill |
| CN116698259A (en) * | 2023-08-04 | 2023-09-05 | 锐马（福建）电气制造有限公司 | Three-dimensional four-axis multidimensional force sensor |
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