US20200372931A1 - Calibrating elevator actuator for disk drive - Google Patents
Calibrating elevator actuator for disk drive Download PDFInfo
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- US20200372931A1 US20200372931A1 US16/806,029 US202016806029A US2020372931A1 US 20200372931 A1 US20200372931 A1 US 20200372931A1 US 202016806029 A US202016806029 A US 202016806029A US 2020372931 A1 US2020372931 A1 US 2020372931A1
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- 238000013500 data storage Methods 0.000 claims abstract description 18
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 230000001360 synchronised effect Effects 0.000 abstract 1
- 239000011295 pitch Substances 0.000 description 23
- 238000000034 method Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 239000004065 semiconductor Substances 0.000 description 3
- 101100428553 Arabidopsis thaliana VIL2 gene Proteins 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 2
- 230000005355 Hall effect Effects 0.000 description 2
- 101150065932 VEL1 gene Proteins 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
- G11B5/553—Details
- G11B5/5534—Initialisation, calibration, e.g. cylinder "set-up"
- G11B5/5543—Initialisation, calibration, e.g. cylinder "set-up" servo-format therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B21/00—Head arrangements not specific to the method of recording or reproducing
- G11B21/16—Supporting the heads; Supporting the sockets for plug-in heads
- G11B21/22—Supporting the heads; Supporting the sockets for plug-in heads while the head is out of operative position
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5552—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means
- G11B5/5556—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means with track following after a "seek"
- G11B5/556—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means with track following after a "seek" control circuits therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
- G11B5/553—Details
- G11B5/5534—Initialisation, calibration, e.g. cylinder "set-up"
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5569—Track change, selection or acquisition by displacement of the head across disk tracks details of specially adapted mobile parts, e.g. electromechanical control devices
- G11B5/5578—Multiple actuators addressing the same disk, e.g. to improve data rate or access rate
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5582—Track change, selection or acquisition by displacement of the head across disk tracks system adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock
Definitions
- Data storage devices such as disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk.
- VCM voice coil motor
- the disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors.
- the servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the actuator arm as it seeks from track to track.
- a disk drive typically comprises a plurality of disks each having a top and bottom surface accessed by a respective head. That is, the VCM typically rotates a number of actuator arms about a pivot in order to simultaneously position a number of heads over respective disk surfaces based on servo data recorded on each disk surface.
- FIG. 1 shows a prior art disk format 2 as comprising a number of servo tracks 4 defined by servo sectors 6 0 - 6 N recorded around the circumference of each servo track.
- Each servo sector 6 i comprises a preamble 8 for storing a periodic pattern, which allows proper gain adjustment and timing synchronization of the read signal, and a sync mark 10 for storing a special pattern used to symbol synchronize to a servo data field 12 .
- the servo data field 12 stores coarse head positioning information, such as a servo track address, used to position the head over a target data track during a seek operation.
- Each servo sector 6 i further comprises groups of servo bursts 14 (e.g., N and Q servo bursts), which are recorded with a predetermined phase relative to one another and relative to the servo track centerlines.
- the phase based servo bursts 14 provide fine head position information used for centerline tracking while accessing a data track during write/read operations.
- a position error signal (PES) is generated by reading the servo bursts 14 , wherein the PES represents a measured position of the head relative to a centerline of a target servo track.
- a servo controller processes the PES to generate a control signal applied to a head actuator (e.g., a voice coil motor) in order to actuate the head radially over the disk in a direction that reduces the PES.
- FIG. 1 shows a prior art disk format comprising a plurality of servo tracks defined by servo sectors.
- FIGS. 2A-2C show a data storage device in the form of a disk drive according to an embodiment comprising an elevator actuator configured to actuate a head along an axial dimension relative to first and second disks, a radial actuator configured to actuate the head radially over the disk surfaces, and a position sensor configured to generate a sinusoidal sensor signal representing a position of the head along the axial dimension.
- FIG. 3A shows an embodiment wherein a crashstop_offset is measured along the axial dimension from a crashstop position of the elevator actuator to a zero crossing of the sinusoidal sensor signal.
- FIG. 3B shows a sinusoidal sensor signal generated by the position sensor according to an embodiment.
- FIG. 4 is a flow diagram according to an embodiment wherein the crashstop_offset is used to position the head relative to the first disk surface.
- FIG. 5A shows an embodiment wherein a first elevator actuator comprising a first lead screw having a first pitch actuates an actuator arm along the axial dimension, and a second elevator actuator comprising a second lead screw having a second pitch actuates at least part of a load/unload ramp along the axial dimension.
- FIG. 5B is a flow diagram according to an embodiment wherein the first pitch of the first elevator actuator and the second pitch of the second elevator actuator are measured in order to synchronize the simultaneous movement of both actuators.
- FIGS. 6A-6D show a disk drive according to an embodiment comprising a first elevator actuator configured to actuate two actuator arms along an axial dimension relative to multiple disks, and a second elevator actuator configured to actuate at least part of a ramp along the axial dimension.
- FIGS. 7A and 7B show an embodiment wherein the position sensor comprises two sensor elements configured to generate quadrature sinusoids in order to compensate for amplitude variations in the sensor signals.
- FIGS. 2A-2C show a data storage device in the form of a disk drive according to an embodiment comprising a first disk comprising a first disk surface 16 A and a second disk comprising a second disk surface 16 C.
- An elevator actuator 20 is configured to actuate a head 18 A along an axial dimension relative to the first and second disks, and a radial actuator 22 configured to actuate the head 18 A radially over the first disk surface 16 A or the second disk surface 16 C.
- a position sensor 24 is configured to generate a sinusoidal sensor signal representing a position of the head 18 A along the axial dimension.
- the disk drive further comprises control circuitry 26 configured to measure a crashstop offset (represented as crashstop_offset in the description below) along the axial dimension from a crashstop position of the elevator actuator 20 to a zero crossing of the sinusoidal sensor signal.
- each disk surface comprises a plurality of servo sectors 28 1 - 28 N that define a plurality of servo tracks, wherein data tracks 30 are defined relative to the servo tracks at the same or different radial density.
- the control circuitry 26 processes a read signal 32 emanating from the head 18 A to demodulate the servo sectors and generate a position error signal (PES) representing an error between the actual position of the head and a target position relative to a target track.
- PES position error signal
- a servo control system in the control circuitry 26 filters the PES using a suitable compensation filter to generate a control signal 34 applied to a VCM 22 which rotates an actuator arm 36 A about a pivot in order to actuate the head radially over the disk surface in a direction that reduces the PES.
- the head 18 A may be actuated over the disk surface 16 A based on the PES using one or more secondary actuators, for example, a microactuator that actuates a suspension coupling a head slider to the actuator arm 36 A, or a microactuator that actuates the head slider relative to the suspension (e.g., using a thermal actuator, piezoelectric actuator, etc.).
- the servo sectors 28 1 - 28 N may comprise any suitable head position information, such as a track address for coarse positioning and servo bursts for fine positioning.
- the servo bursts may comprise any suitable pattern, such as an amplitude based servo pattern or a phase based servo pattern ( FIG. 1 ).
- the VCM 22 actuates two actuator arms 36 A and 36 B each actuating a respective head 18 A and 18 B.
- the elevator actuator 20 in this embodiment actuates the actuator arms 36 A and 36 B in an axial dimension relative to the disks, effectively implementing an “elevator” system that raises/lowers the actuator arms 36 A and 36 B to enable the heads 18 A and 18 B to access the top and bottom surfaces of multiple disks (two disks in this example).
- This embodiment reduces the cost of the disk drive by reducing the number of actuator arms as well as the number of heads needed to access disk surface as compared to a conventional disk drive employing multiple actuator arms for actuating a respective head over a respective (dedicated) disk surface.
- This embodiment may also reduce the cost of the VCM 22 since it reduces the number (mass) of actuator arms rotated about the pivot.
- Another embodiment may employ a single actuator arm for actuating two heads or a single head, thereby further reducing the cost of the disk drive.
- a different type of radial actuator may be employed to actuate the head(s) radially over the disk surfaces, such as a linear actuator.
- any suitable position sensor 24 may be employed in the embodiments disclosed herein, such as any suitable optical or magnetic sensor.
- the position sensor may be implemented in any suitable mechanical configuration, such as an encoder strip and a corresponding transducer coupled to the actuator arm assembly as shown in the embodiment of FIG. 2B .
- FIG. 3A shows an embodiment wherein the position sensor 24 comprises a magnetic encoder strip 38 comprising a plurality of alternating polarity fixed magnets (N/S, N/S, . . .).
- the magnetic encoder strip 38 is fixed relative to the actuator arms and a suitable magnetic sensor, such as a Hall effect sensor, is coupled, for example, to the actuator arms 36 A and 36 B.
- the magnetic sensor As the elevator actuator 20 moves the actuator arms 36 A and 36 B in the axial dimension in order to reposition the head(s) over different disk surfaces, the magnetic sensor generates a sinusoidal sensor signal such as shown in FIG. 3B due to sensing the alternating magnetic field of the magnetic encoder strip 38 .
- the encoder strip 38 such as shown in FIG. 3A as well as the disks may be installed during manufacturing such that the axial location of each disk surface relative to the encoder strip 38 may be known within an insignificantly small variance.
- the variance in coupling the actuator arms to the base of the disk drive may create a significant variance between the location of the actuator arms relative to the encoder strip 38 when the elevator actuator 20 reaches a crashstop position.
- the crashstop position may be defined as the elevator actuator 20 moving the actuator arms down the axial dimension to the lowest point.
- the elevator actuator 20 may contact a physical crashstop at this point, and in another embodiment, at least part of the actuator arm assembly may contact a physical crashstop.
- the variance between the location of the actuator arms relative to the encoder strip 38 at the crashstop position is calibrated out by detecting a zero crossing in the sinusoidal sensor signal which then defines a home position for the actuator arms relative to the encoder strip 38 .
- FIG. 3A An example of this embodiment is shown in FIG. 3A wherein a crashstop_offset is measured along the axial dimension from a crashstop position of the elevator actuator 20 to a zero crossing of the sinusoidal sensor signal.
- the elevator actuator 20 moves the actuator arms up the axial dimension until the first zero crossing in the sinusoidal sensor signal is detected.
- the crashstop_offset may be measured relative to a different (e.g., second) zero crossing in the sinusoidal sensor signal.
- the crashstop_offset may be measured by detecting a target zero crossing in the sinusoidal sensor signal, and then moving the elevator actuator 20 to the crashstop position.
- the crashstop_offset may be measured by moving the elevator actuator 20 between the crashstop position and the target zero crossing multiple times and averaging the offset measurements.
- the crashstop_offset may be measured by detecting multiple zero crossings in the sinusoidal sensor signal. For example, in the example of FIG. 3A the elevator actuator 20 may move the actuator arms up the axial dimension over multiple zero crossings and the crashstop_offset (e.g., relative to the first zero crossing) may be measured based on the measured position of the multiple zero crossings (e.g., by averaging out noise in the sinusoidal sensor signal).
- the elevator actuator 20 is controlled to move the head(s) to a nominal position representing the location of a target disk surface (e.g., move head 18 B to disk surface 16 D in FIG. 2C ).
- the nominal position is defined as a nominal distance D 1 from the crashstop position to the position representing the target disk surface. Accordingly in one embodiment, the elevator actuator 20 is first moved to the target zero crossing described above which represents the home position for the position sensor 24 , and then the elevator actuator 20 is moved a distance:
- the elevator actuator 20 is moved to the crashstop position (block 40 ), and then the elevator actuator 20 moves the heads along the axial dimension (block 42 ) until the first zero crossing is detected in the sinusoidal sensor signal (block 44 ).
- the corresponding crashstop_offset is saved (block 46 ), and the position sensor is “homed” based on the detected zero crossing (block 48 ).
- the “home” position may be defined as a distance of zero along the axial dimension which may be defined by the location of the detected zero crossing in the sinusoidal sensor signal.
- the elevator actuator 20 then moves the head(s) from the home position to the nominal position of a target disk surface by moving the head(s) by a distance of D 1 minus the crashstop_offset (block 50 ).
- the measured crashstop_offset may be saved, for example, in a non-volatile semiconductor memory and then used to move the head(s) to a first target disk surface when the disk drive is powered on.
- the elevator actuator 20 may be moved to the crashstop position and then moved up until detecting the first zero crossing in the sinusoidal sensor signal which defines the home position for the elevator actuator.
- the elevator actuator 20 then moves the heads by the distance D 1 minus the saved crashstop_offset (i.e., in this embodiment it is unnecessary to remeasure the crashstop_offset).
- the elevator actuator 20 may be controlled open loop when moving to the crashstop position as well as moving to the target zero crossing of the sinusoidal sensor signal as described above with reference to FIG. 3A and 3B .
- the elevator actuator 20 may be controlled closed loop based on any suitable states (velocity, position, etc.) as determined from the position sensor 24 .
- the elevator actuator 20 may be controlled using a suitable velocity profile in order to seek the head(s) along the axial dimension toward a target position relative to the disk surfaces.
- the closed loop control may switch the feedback in order to control the elevator actuator 20 based on a position error in order to settle onto the target position.
- the disk drive may comprise a ramp 52 configured to load/unload the head(s) to and from a target disk surface.
- the actuator arm(s) may be actuated along the axial direction by a first elevator actuator 54 , and at least part of the ramp 52 may be simultaneously actuated along the axial dimension by a second elevator actuator 56 in order to position the head(s) relative to the disk surfaces prior to loading the head(s) onto a target disk surface.
- the first elevator actuator 54 comprises a first stepper motor configured to rotate a first lead screw 58 in order to actuate the actuator arms 36 A and 36 B which are threaded onto the first lead screw 58
- the second elevator actuator 56 comprises a second stepper motor configured to rotate a second lead screw 60 in order to actuate at least part of the ramp 52 which is threaded onto the second lead screw 60
- the first lead screw 58 comprises a first pitch
- the second lead screw 60 comprises a second pitch different than the first pitch.
- the pitch of the first lead screw 58 is greater than the pitch of the second lead screw 60 , but in other embodiments the opposite may be the case.
- control circuitry 26 synchronizes a simultaneous movement of the first and second elevator actuators 54 and 56 , for example, to compensate for the difference in pitch between lead screws such as shown in FIG. 5A .
- a first velocity command may be generated to move the first elevator actuator 54 and a corresponding second velocity command may be generated to simultaneously move the second elevator actuator 56 .
- the second velocity command may initially be generated based on a default (nominal) pitch ratio between the first and second lead screws 58 and 60 :
- VELpbcmd2 VELcmd1*P1def/P2def
- VELcmd2 VELcmd1*P1mes/P2mes
- P 1 mes represents the measured pitch of the first lead screw 58 and P 2 mes represents the measured pitch of the second lead screw 60 .
- FIG. 5B An example of this embodiment is understood with reference to the flow diagram of FIG. 5B , wherein default velocity commands are generated for the first and second elevator actuators (block 62 ) based on the ratio of the default pitches of the lead screws 58 and 60 as described above.
- Each elevator actuator is moved to their respective crashstop positions using their respective default velocity commands (block 64 ).
- Each elevator actuator is then moved up toward a first zero crossing of at least one of the sinusoidal position signals (block 66 ) until the first zero crossing is detected (block 68 ).
- the position sensors are homed (e.g., zeroed) based on the detected zero crossing (block 70 ).
- Both axial motors are controlled to rotate n full revolutions (block 72 ), and the corresponding displacements Dn 1 and Dn 2 of the actuator arm(s) and ramp are measured based on the corresponding position sensors (block 74 ).
- the pitches of each lead screw is then measured (block 76 ). based on:
- the velocity command for the second elevator actuator is then generated based on the ratio of the measured pitches (block 78 ).
- a velocity command may be generated for the second elevator actuator and a corresponding velocity command generated for the first elevator actuator based on the ratio of the measured pitches.
- FIGS. 6A-6D show a disk drive according to an embodiment comprising a first elevator actuator 54 ( FIG. 6B ) configured to actuate two actuator arms 36 A and 36 B along an axial dimension relative to multiple disks, and a second elevator actuator 56 ( FIG. 6D ) configured to actuate at least part of a ramp along the axial dimension.
- the first elevator actuator 54 comprises a first stepper motor configured to rotate a first lead screw 58 ( FIG. 6C ) in order to vertically actuate the actuator arms 36 A and 36 B which are threaded onto the first lead screw 58
- the second elevator actuator 56 comprises a second stepper motor configured to rotate a second lead screw 60 ( FIG.
- the ramp 52 comprises a first ramp part 52 A that is fixed relative to the disks, and a second ramp part 52 B that is vertically actuated in the axial dimension by rotating the second lead screw 60 .
- the heads 18 A and 18 B are unloaded onto the second ramp part 52 B prior to vertically actuating the second ramp part 52 B in the axial dimension.
- the heads 18 A and 18 B are loaded onto the respective disk surfaces by rotating the actuator arms 36 A and 36 B such that the heads slide along the second ramp part 52 B onto the first ramp part 52 A, and then loaded from the first ramp part 52 A onto the respective disk surfaces.
- the first lead screw 58 comprises a cylindrical assembly that is rotated (clockwise or counter-clockwise) about a pivot assembly 80 using any suitable stepper motor (e.g., a claw-pole permanent magnet stepper motor), thereby adjusting the vertical position of the actuator arms 36 A and 36 B along the axial dimension.
- a voice coil 82 is coupled to the pivot assembly 80 which is rotated about a fixed pivot 84 in order to rotate the combined assembly (voice coil 82 , actuator arms 36 A and 36 B, and lead screw 58 ) about the fixed pivot 84 , thereby actuating the heads 18 A and 18 B radially over the respective disk surfaces.
- the combined assembly further comprises an encoder strip 86 (similar to the encoder strip 38 of FIG.
- the ramp assembly also comprises an encoder strip 90 (similar to the encoder strip 38 of FIG. 3A ) and at least one sensor coupled to the second ramp part 52 B for generating a sinusoidal sensor signal such as shown in FIG. 3B as the second ramp part 52 B moves along the axial dimension by rotating the second lead screw 60 using any suitable stepper motor.
- FIG. 7A and 7B show an embodiment wherein the position sensor comprises two sensor elements 92 A and 92 B (e.g., two Hall effect sensors) configured to generate respective quadrature sinusoids 94 A and 94 B (phase offset by ninety degrees) in order to compensate for amplitude variations in the sensor signals 92 A and 92 B.
- the first quadrature sinusoid 94 A generated by the first sensor element 92 A may be represented as:
- g represents a gain of the sinusoids.
- the gain g (and corresponding amplitude of the sinusoids) may vary due, for example, to temperature fluctuations or fluctuations in the gap between the encoder strip 86 / 90 and the sensor elements 92 A and 92 B across the stroke of the sensor elements. Variations in the amplitude of a single sinusoidal signal generated by a single sensor element may induce errors in the position signal demodulated from the sinusoidal signal. This amplitude variation can be compensated by employing two sensor elements 92 A and 92 B that are offset vertically by ninety degrees (such as shown in FIG. 7A ) and by exploiting the trigonometry identity:
- the amplitude of the quadrature sinusoids 94 A and 94 B may be normalized by dividing the output of each sensor element 92 A and 92 B by the above trigonometry identity:
- other anomalies in the quadrature sinusoids 94 A and 94 B may be compensated using any suitable signal processing techniques prior to normalizing the amplitude as described above, such as compensating for a sensitivity difference between the sensor elements 92 A and 92 B resulting in different relative amplitudes of the quadrature sinusoids, compensating for a phase error between the quadrature sinusoids, or compensating for a DC offset of the quadrature sinusoids.
- control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a data storage controller, or certain operations described above may be performed by a read channel and others by a data storage controller.
- the read channel and data storage controller are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC).
- the control circuitry may include a suitable preamp circuit implemented as a separate integrated circuit, integrated into the read channel or data storage controller circuit, or integrated into a SOC.
- control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the flow diagrams described herein.
- the instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In another embodiment, the instructions are stored on the disk and read into a volatile semiconductor memory when the disk drive is powered on. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry.
- At least some of the flow diagram blocks may be implemented using analog circuitry (e.g., analog comparators, timers, etc.), and in other embodiments at least some of the blocks may be implemented using digital circuitry or a combination of analog/digital circuitry.
- analog circuitry e.g., analog comparators, timers, etc.
- digital circuitry e.g., digital comparators, timers, etc.
- a disk drive may include a magnetic disk drive, an optical disk drive, a hybrid disk drive, etc.
- some embodiments may include electronic devices such as computing devices, data server devices, media content storage devices, etc. that comprise the storage media and/or control circuitry as described above.
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Abstract
Description
- This application is a divisional of U.S. patent application Ser. No. 16/433,110 filed on Jun. 06, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62/851,169, filed on May 22, 2019, all of which are hereby incorporated by reference in their entirety.
- Data storage devices such as disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the actuator arm as it seeks from track to track.
- A disk drive typically comprises a plurality of disks each having a top and bottom surface accessed by a respective head. That is, the VCM typically rotates a number of actuator arms about a pivot in order to simultaneously position a number of heads over respective disk surfaces based on servo data recorded on each disk surface.
FIG. 1 shows a priorart disk format 2 as comprising a number ofservo tracks 4 defined by servo sectors 6 0-6 N recorded around the circumference of each servo track. Eachservo sector 6 i comprises a preamble 8 for storing a periodic pattern, which allows proper gain adjustment and timing synchronization of the read signal, and async mark 10 for storing a special pattern used to symbol synchronize to aservo data field 12. The servo data field 12 stores coarse head positioning information, such as a servo track address, used to position the head over a target data track during a seek operation. Eachservo sector 6 i further comprises groups of servo bursts 14 (e.g., N and Q servo bursts), which are recorded with a predetermined phase relative to one another and relative to the servo track centerlines. The phase based servo bursts 14 provide fine head position information used for centerline tracking while accessing a data track during write/read operations. A position error signal (PES) is generated by reading the servo bursts 14, wherein the PES represents a measured position of the head relative to a centerline of a target servo track. A servo controller processes the PES to generate a control signal applied to a head actuator (e.g., a voice coil motor) in order to actuate the head radially over the disk in a direction that reduces the PES. -
FIG. 1 shows a prior art disk format comprising a plurality of servo tracks defined by servo sectors. -
FIGS. 2A-2C show a data storage device in the form of a disk drive according to an embodiment comprising an elevator actuator configured to actuate a head along an axial dimension relative to first and second disks, a radial actuator configured to actuate the head radially over the disk surfaces, and a position sensor configured to generate a sinusoidal sensor signal representing a position of the head along the axial dimension. -
FIG. 3A shows an embodiment wherein a crashstop_offset is measured along the axial dimension from a crashstop position of the elevator actuator to a zero crossing of the sinusoidal sensor signal. -
FIG. 3B shows a sinusoidal sensor signal generated by the position sensor according to an embodiment. -
FIG. 4 is a flow diagram according to an embodiment wherein the crashstop_offset is used to position the head relative to the first disk surface. -
FIG. 5A shows an embodiment wherein a first elevator actuator comprising a first lead screw having a first pitch actuates an actuator arm along the axial dimension, and a second elevator actuator comprising a second lead screw having a second pitch actuates at least part of a load/unload ramp along the axial dimension. -
FIG. 5B is a flow diagram according to an embodiment wherein the first pitch of the first elevator actuator and the second pitch of the second elevator actuator are measured in order to synchronize the simultaneous movement of both actuators. -
FIGS. 6A-6D show a disk drive according to an embodiment comprising a first elevator actuator configured to actuate two actuator arms along an axial dimension relative to multiple disks, and a second elevator actuator configured to actuate at least part of a ramp along the axial dimension. -
FIGS. 7A and 7B show an embodiment wherein the position sensor comprises two sensor elements configured to generate quadrature sinusoids in order to compensate for amplitude variations in the sensor signals. -
FIGS. 2A-2C show a data storage device in the form of a disk drive according to an embodiment comprising a first disk comprising afirst disk surface 16A and a second disk comprising asecond disk surface 16C. Anelevator actuator 20 is configured to actuate ahead 18A along an axial dimension relative to the first and second disks, and aradial actuator 22 configured to actuate thehead 18A radially over thefirst disk surface 16A or thesecond disk surface 16C. Aposition sensor 24 is configured to generate a sinusoidal sensor signal representing a position of thehead 18A along the axial dimension. The disk drive further comprisescontrol circuitry 26 configured to measure a crashstop offset (represented as crashstop_offset in the description below) along the axial dimension from a crashstop position of theelevator actuator 20 to a zero crossing of the sinusoidal sensor signal. - In the embodiment of
FIG. 2A , each disk surface comprises a plurality of servo sectors 28 1-28 N that define a plurality of servo tracks, whereindata tracks 30 are defined relative to the servo tracks at the same or different radial density. Thecontrol circuitry 26 processes aread signal 32 emanating from thehead 18A to demodulate the servo sectors and generate a position error signal (PES) representing an error between the actual position of the head and a target position relative to a target track. A servo control system in thecontrol circuitry 26 filters the PES using a suitable compensation filter to generate acontrol signal 34 applied to aVCM 22 which rotates anactuator arm 36A about a pivot in order to actuate the head radially over the disk surface in a direction that reduces the PES. In one embodiment, thehead 18A may be actuated over thedisk surface 16A based on the PES using one or more secondary actuators, for example, a microactuator that actuates a suspension coupling a head slider to theactuator arm 36A, or a microactuator that actuates the head slider relative to the suspension (e.g., using a thermal actuator, piezoelectric actuator, etc.). The servo sectors 28 1-28 N may comprise any suitable head position information, such as a track address for coarse positioning and servo bursts for fine positioning. The servo bursts may comprise any suitable pattern, such as an amplitude based servo pattern or a phase based servo pattern (FIG. 1 ). - In the embodiment shown in
FIGS. 2B-2C , theVCM 22 actuates twoactuator arms respective head elevator actuator 20 in this embodiment actuates theactuator arms actuator arms heads VCM 22 since it reduces the number (mass) of actuator arms rotated about the pivot. Another embodiment may employ a single actuator arm for actuating two heads or a single head, thereby further reducing the cost of the disk drive. In yet another embodiment, a different type of radial actuator may be employed to actuate the head(s) radially over the disk surfaces, such as a linear actuator. - Any
suitable position sensor 24 may be employed in the embodiments disclosed herein, such as any suitable optical or magnetic sensor. In addition, the position sensor may be implemented in any suitable mechanical configuration, such as an encoder strip and a corresponding transducer coupled to the actuator arm assembly as shown in the embodiment ofFIG. 2B .FIG. 3A shows an embodiment wherein theposition sensor 24 comprises amagnetic encoder strip 38 comprising a plurality of alternating polarity fixed magnets (N/S, N/S, . . .). Themagnetic encoder strip 38 is fixed relative to the actuator arms and a suitable magnetic sensor, such as a Hall effect sensor, is coupled, for example, to theactuator arms elevator actuator 20 moves theactuator arms FIG. 3B due to sensing the alternating magnetic field of themagnetic encoder strip 38. - In one embodiment, the
encoder strip 38 such as shown inFIG. 3A as well as the disks may be installed during manufacturing such that the axial location of each disk surface relative to theencoder strip 38 may be known within an insignificantly small variance. However in one embodiment, the variance in coupling the actuator arms to the base of the disk drive may create a significant variance between the location of the actuator arms relative to theencoder strip 38 when theelevator actuator 20 reaches a crashstop position. In the example ofFIG. 3A , the crashstop position may be defined as theelevator actuator 20 moving the actuator arms down the axial dimension to the lowest point. In one embodiment, theelevator actuator 20 may contact a physical crashstop at this point, and in another embodiment, at least part of the actuator arm assembly may contact a physical crashstop. In one embodiment, the variance between the location of the actuator arms relative to theencoder strip 38 at the crashstop position is calibrated out by detecting a zero crossing in the sinusoidal sensor signal which then defines a home position for the actuator arms relative to theencoder strip 38. - An example of this embodiment is shown in
FIG. 3A wherein a crashstop_offset is measured along the axial dimension from a crashstop position of theelevator actuator 20 to a zero crossing of the sinusoidal sensor signal. In the example ofFIG. 3A and 3B , theelevator actuator 20 moves the actuator arms up the axial dimension until the first zero crossing in the sinusoidal sensor signal is detected. In other embodiments, the crashstop_offset may be measured relative to a different (e.g., second) zero crossing in the sinusoidal sensor signal. In one embodiment, the crashstop_offset may be measured by detecting a target zero crossing in the sinusoidal sensor signal, and then moving theelevator actuator 20 to the crashstop position. In one embodiment, the crashstop_offset may be measured by moving theelevator actuator 20 between the crashstop position and the target zero crossing multiple times and averaging the offset measurements. In yet another embodiment, the crashstop_offset may be measured by detecting multiple zero crossings in the sinusoidal sensor signal. For example, in the example ofFIG. 3A theelevator actuator 20 may move the actuator arms up the axial dimension over multiple zero crossings and the crashstop_offset (e.g., relative to the first zero crossing) may be measured based on the measured position of the multiple zero crossings (e.g., by averaging out noise in the sinusoidal sensor signal). - In one embodiment, after measuring the crashstop_offset relative to a target zero crossing, the
elevator actuator 20 is controlled to move the head(s) to a nominal position representing the location of a target disk surface (e.g.,move head 18B todisk surface 16D inFIG. 2C ). In one embodiment, the nominal position is defined as a nominal distance D1 from the crashstop position to the position representing the target disk surface. Accordingly in one embodiment, theelevator actuator 20 is first moved to the target zero crossing described above which represents the home position for theposition sensor 24, and then theelevator actuator 20 is moved a distance: -
D1-crashstop_offset - in order position the head(s) to the nominal position representing the location of the target disk surface. An example of this embodiment is understood with reference to the flow diagram of
FIG. 4 , wherein theelevator actuator 20 is moved to the crashstop position (block 40), and then theelevator actuator 20 moves the heads along the axial dimension (block 42) until the first zero crossing is detected in the sinusoidal sensor signal (block 44). The corresponding crashstop_offset is saved (block 46), and the position sensor is “homed” based on the detected zero crossing (block 48). For example, the “home” position may be defined as a distance of zero along the axial dimension which may be defined by the location of the detected zero crossing in the sinusoidal sensor signal. The elevator actuator 20 then moves the head(s) from the home position to the nominal position of a target disk surface by moving the head(s) by a distance of D1 minus the crashstop_offset (block 50). - In one embodiment, the measured crashstop_offset may be saved, for example, in a non-volatile semiconductor memory and then used to move the head(s) to a first target disk surface when the disk drive is powered on. For example, when the disk drive is powered on the
elevator actuator 20 may be moved to the crashstop position and then moved up until detecting the first zero crossing in the sinusoidal sensor signal which defines the home position for the elevator actuator. The elevator actuator 20 then moves the heads by the distance D1 minus the saved crashstop_offset (i.e., in this embodiment it is unnecessary to remeasure the crashstop_offset). - In one embodiment, the
elevator actuator 20 may be controlled open loop when moving to the crashstop position as well as moving to the target zero crossing of the sinusoidal sensor signal as described above with reference toFIG. 3A and 3B . After homing theposition sensor 24 based on the detected zero crossing, in one embodiment theelevator actuator 20 may be controlled closed loop based on any suitable states (velocity, position, etc.) as determined from theposition sensor 24. For example, in one embodiment theelevator actuator 20 may be controlled using a suitable velocity profile in order to seek the head(s) along the axial dimension toward a target position relative to the disk surfaces. When the head(s) are within a predetermined threshold of the target position, the closed loop control may switch the feedback in order to control theelevator actuator 20 based on a position error in order to settle onto the target position. - In one embodiment (an example of which is shown in
FIGS. 6A-6D ), the disk drive may comprise aramp 52 configured to load/unload the head(s) to and from a target disk surface. In one embodiment, the actuator arm(s) may be actuated along the axial direction by afirst elevator actuator 54, and at least part of theramp 52 may be simultaneously actuated along the axial dimension by asecond elevator actuator 56 in order to position the head(s) relative to the disk surfaces prior to loading the head(s) onto a target disk surface. In the embodiment shown inFIGS. 6A-6D , thefirst elevator actuator 54 comprises a first stepper motor configured to rotate afirst lead screw 58 in order to actuate theactuator arms first lead screw 58, and thesecond elevator actuator 56 comprises a second stepper motor configured to rotate asecond lead screw 60 in order to actuate at least part of theramp 52 which is threaded onto thesecond lead screw 60. In one embodiment shown inFIG. 5A , thefirst lead screw 58 comprises a first pitch and thesecond lead screw 60 comprises a second pitch different than the first pitch. In the example ofFIG. 5A , the pitch of thefirst lead screw 58 is greater than the pitch of thesecond lead screw 60, but in other embodiments the opposite may be the case. - In one embodiment, the
control circuitry 26 synchronizes a simultaneous movement of the first andsecond elevator actuators FIG. 5A . For example, in one embodiment a first velocity command may be generated to move thefirst elevator actuator 54 and a corresponding second velocity command may be generated to simultaneously move thesecond elevator actuator 56. In one embodiment, the second velocity command may initially be generated based on a default (nominal) pitch ratio between the first and second lead screws 58 and 60: -
VELcmd1=VEL1 -
VELpbcmd2=VELcmd1*P1def/P2def - where P1def represents the default pitch of the
first lead screw 58 and P2def represents the default pitch of thesecond lead screw 60. After homing the first andsecond elevator actuators lead screw second elevator actuators 54 and 56: -
VELcmd1=VEL1 -
VELcmd2=VELcmd1*P1mes/P2mes - where P1mes represents the measured pitch of the
first lead screw 58 and P2mes represents the measured pitch of thesecond lead screw 60. - An example of this embodiment is understood with reference to the flow diagram of
FIG. 5B , wherein default velocity commands are generated for the first and second elevator actuators (block 62) based on the ratio of the default pitches of the lead screws 58 and 60 as described above. Each elevator actuator is moved to their respective crashstop positions using their respective default velocity commands (block 64). Each elevator actuator is then moved up toward a first zero crossing of at least one of the sinusoidal position signals (block 66) until the first zero crossing is detected (block 68). The position sensors are homed (e.g., zeroed) based on the detected zero crossing (block 70). Both axial motors are controlled to rotate n full revolutions (block 72), and the corresponding displacements Dn1 and Dn2 of the actuator arm(s) and ramp are measured based on the corresponding position sensors (block 74). The pitches of each lead screw is then measured (block 76). based on: -
P1mes=Dn1/n -
P2mes=Dn2/n - where P1mes represents the measured pitch of the first lead screw and P2mes represents the measured pitch of the second lead screw. The velocity command for the second elevator actuator is then generated based on the ratio of the measured pitches (block 78). In an alternative embodiment, a velocity command may be generated for the second elevator actuator and a corresponding velocity command generated for the first elevator actuator based on the ratio of the measured pitches.
-
FIGS. 6A-6D show a disk drive according to an embodiment comprising a first elevator actuator 54 (FIG. 6B ) configured to actuate twoactuator arms FIG. 6D ) configured to actuate at least part of a ramp along the axial dimension. Thefirst elevator actuator 54 comprises a first stepper motor configured to rotate a first lead screw 58 (FIG. 6C ) in order to vertically actuate theactuator arms first lead screw 58, and thesecond elevator actuator 56 comprises a second stepper motor configured to rotate a second lead screw 60 (FIG. 6D ) in order to vertically actuate at least part of theramp 52B which is threaded onto thesecond lead screw 60. In the embodiment ofFIG. 6D , theramp 52 comprises afirst ramp part 52A that is fixed relative to the disks, and asecond ramp part 52B that is vertically actuated in the axial dimension by rotating thesecond lead screw 60. Theheads second ramp part 52B prior to vertically actuating thesecond ramp part 52B in the axial dimension. After positioning thesecond ramp part 52B to a target disk, theheads actuator arms second ramp part 52B onto thefirst ramp part 52A, and then loaded from thefirst ramp part 52A onto the respective disk surfaces. - In the embodiment of
FIG. 6C , thefirst lead screw 58 comprises a cylindrical assembly that is rotated (clockwise or counter-clockwise) about apivot assembly 80 using any suitable stepper motor (e.g., a claw-pole permanent magnet stepper motor), thereby adjusting the vertical position of theactuator arms voice coil 82 is coupled to thepivot assembly 80 which is rotated about a fixedpivot 84 in order to rotate the combined assembly (voice coil 82,actuator arms pivot 84, thereby actuating theheads encoder strip 38 ofFIG. 3A ) coupled to the voice coil assembly and at least onesensor 88 coupled to the actuator arm assembly. As theactuator arms sensor 88 generates a sinusoidal sensor signal such as shown inFIG. 3B which may be demodulated in any suitable manner to generate a position signal representing a position of the actuator arms along the axial dimension. In the embodiment ofFIG. 6D , the ramp assembly also comprises an encoder strip 90 (similar to theencoder strip 38 ofFIG. 3A ) and at least one sensor coupled to thesecond ramp part 52B for generating a sinusoidal sensor signal such as shown inFIG. 3B as thesecond ramp part 52B moves along the axial dimension by rotating thesecond lead screw 60 using any suitable stepper motor. -
FIG. 7A and 7B show an embodiment wherein the position sensor comprises twosensor elements respective quadrature sinusoids first quadrature sinusoid 94A generated by thefirst sensor element 92A may be represented as: -
g·sin(t) - and the
second quadrature sinusoid 94B generated by thesecond sensor element 92B may be represented as: -
g·cos(t) - where g represents a gain of the sinusoids. In one embodiment, the gain g (and corresponding amplitude of the sinusoids) may vary due, for example, to temperature fluctuations or fluctuations in the gap between the
encoder strip 86/90 and thesensor elements sensor elements FIG. 7A ) and by exploiting the trigonometry identity: -
sqrt[(g·sin(t))2+(g·cos(t))2]=g - That is, the amplitude of the
quadrature sinusoids sensor element -
- In other embodiments, other anomalies in the
quadrature sinusoids sensor elements - Any suitable control circuitry may be employed to implement the flow diagrams in the above embodiments, such as any suitable integrated circuit or circuits. For example, the control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a data storage controller, or certain operations described above may be performed by a read channel and others by a data storage controller. In one embodiment, the read channel and data storage controller are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC). In addition, the control circuitry may include a suitable preamp circuit implemented as a separate integrated circuit, integrated into the read channel or data storage controller circuit, or integrated into a SOC.
- In one embodiment, the control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the flow diagrams described herein. The instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In another embodiment, the instructions are stored on the disk and read into a volatile semiconductor memory when the disk drive is powered on. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry. In some embodiments, at least some of the flow diagram blocks may be implemented using analog circuitry (e.g., analog comparators, timers, etc.), and in other embodiments at least some of the blocks may be implemented using digital circuitry or a combination of analog/digital circuitry.
- In various embodiments, a disk drive may include a magnetic disk drive, an optical disk drive, a hybrid disk drive, etc. In addition, some embodiments may include electronic devices such as computing devices, data server devices, media content storage devices, etc. that comprise the storage media and/or control circuitry as described above.
- The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method, event or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described tasks or events may be performed in an order other than that specifically disclosed, or multiple may be combined in a single block or state. The example tasks or events may be performed in serial, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed example embodiments.
- While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the embodiments disclosed herein.
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- 2019-06-06 US US16/433,110 patent/US10622012B1/en active Active
- 2019-12-26 WO PCT/US2019/068514 patent/WO2020236222A1/en active Application Filing
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