Data storage devices and methods with frequency-shaped sliding mode control

Patent metadata

Field	Value
Publication number	US-9542966-B1
Application number	US-201514828255-A
Country	US
Kind code	B1
Filing date	Aug 17, 2015
Priority date	Jul 9, 2015
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A data storage device includes a disk, a head, a microactuator, a coarse actuator, and a servo controller. The microactuator is configured to position the head relative to the disk. The coarse actuator is configured to position the microactuator relative to the disk. The servo controller is configured to generate an adjusted position error signal based on a position error signal and an estimated microactuator position signal. The servo controller is also configured to filter the adjusted position error signal with a shaping filter to generate a filtered position error signal, and to provide sliding mode control of the coarse actuator based at least partially on the filtered position error signal.

First claim

What is claimed is:

1. A data storage device, comprising:
a microactuator configured to position a head relative to a disk;
a coarse actuator configured to position the microactuator relative to the disk; and
a servo controller configured to generate an adjusted position error signal based on a position error signal and an estimated microactuator position signal, and configured to filter the adjusted position error signal with a shaping filter to generate a filtered position error signal, and configured to provide sliding mode control of the coarse actuator based at least partially on the filtered position error signal;
wherein the shaping filter is configured to provide frequency dependent filtering of the adjusted position error signal to generate the filtered position error signal.

2. The data storage device of claim 1 ,
wherein the servo controller is further configured to generate a derivative position error signal as a derivative of the adjusted position error signal, and is configured to provide the sliding mode control of the coarse actuator based on the filtered position error signal and the derivative position error signal.

3. The data storage device of claim 2 ,
wherein the servo controller is further configured to scale the derivative position error signal to generate a scaled derivative position error signal, and is configured to provide the sliding mode control of the coarse actuator based on the filtered position error signal and the scaled derivative position error signal.

4. The data storage device of claim 1 ,
wherein the servo controller comprises a digital signal processor programmed with a discrete time state space model of the shaping filter and a control law for the sliding mode control.

5. The data storage device of claim 1 ,
wherein the shaping filter is a peak filter with a single peak.

6. The data storage device of claim 1 ,
wherein the shaping filter is a peak filter with multiple peaks.

7. The data storage device of claim 1 ,
wherein the shaping filter is a peak filter that is configured to amplify a magnitude of the adjusted position error signal when a frequency of the adjusted position error signal is approximately a peak frequency of the peak filter.

8. The data storage device of claim 7 ,
wherein the peak frequency of the peak filter is an expected frequency of the position error signal due to vibration of an actuator arm assembly on which the head is mounted induced by audio sounds.

9. The data storage device of claim 1 ,
wherein the servo controller is further configured such that the sliding mode control provided by the servo controller comprises a nonlinear control of the coarse actuator with respect to the filtered position error signal.

10. The data storage device of claim 1 ,
wherein the servo controller is further configured such that the sliding mode control comprises a discrete time nonlinear control that includes an approaching phase in which a trajectory of the sliding mode control is toward a sliding surface and a sliding phase in which the trajectory of the sliding mode control is to slide along the sliding surface, and wherein the sliding mode control has a different gain when the trajectory is approaching from one side of the sliding surface than when the trajectory is approaching from an opposite side of the sliding surface.

11. The data storage device of claim 1 ,
wherein the coarse actuator comprises a voice coil motor; and
wherein the microactuator comprises a piezoelectric actuator.

12. The data storage device of claim 1 ,
wherein the position error signal represents a position of the head relative to a center of a track of the disk; and
wherein the servo controller is further configured to generate a microactuator compensation signal to control the microactuator based on the position error signal, and is further configured to generate the estimated microactuator position signal with a microactuator position estimator that estimates a response of the microactuator to the microactuator compensation signal.

13. A method for providing control in a data storage device, the method comprising:
generating an adjusted position error signal based on a position error signal and an estimated microactuator position signal;
filtering the adjusted position error signal with a shaping filter that provides frequency dependent filtering of the adjusted position error signal to generate a filtered position error signal; and
providing sliding mode control of a coarse actuator based at least partially on the filtered position error signal.

14. The method of claim 13 , further comprising:
generating a microactuator compensation signal to control a microactuator based on the position error signal; and
generating the estimated microactuator position signal with a microactuator position estimator that estimates a response of the microactuator to the microactuator compensation signal;
wherein the position error signal represents a position of a head moved by the coarse actuator and the microactuator relative to a center of a track of a disk.

15. The method of claim 13 , further comprising:
generating a derivative position error signal as a derivative of the adjusted position error signal;
wherein providing the sliding mode control includes providing the sliding mode control based on the filtered position error signal and the derivative position error signal.

16. The method of claim 15 , further comprising:
scaling the derivative position error signal to generate a scaled derivative position error signal;
wherein providing the sliding mode control includes providing the sliding mode control based on the filtered position error signal and the scaled derivative position error signal.

17. The method of claim 13 ,
wherein the shaping filter is a peak filter with a single peak.

18. The method of claim 13 ,
wherein the shaping filter is a peak filter with multiple peaks.

19. The method of claim 13 , wherein the shaping filter is a peak filter, and wherein the method further comprises:
processing a particular position error signal obtained while an actuator arm assembly on which a head is mounted to is vibrating due to external audio sound with an adaptive notch filter with adjustable notch frequencies to determine at least one frequency range at which the particular position error signal has a maximum value; and
setting a peak frequency of the peak filter based on the at least one frequency range.

20. The method of claim 13 ,
wherein the sliding mode control comprises a discrete time nonlinear control that includes an approaching phase in which a trajectory of the sliding mode control is toward a sliding surface and a sliding phase in which the trajectory of the sliding mode control is to slide along the sliding surface, and wherein the sliding mode control has a different gain when the trajectory is approaching from one side of the sliding surface than when the trajectory is approaching from an opposite side of the sliding surface.

21. The method of claim 13 ,
wherein the shaping filter has a frequency response that provides a varying amplification or attenuation of the adjusted position error signal as a function of frequency of the adjusted position error signal.

22. The method of claim 13 ,
wherein the shaping filter is a peak filter having a frequency response that is at a maximum at a peak frequency.

23. The method of claim 22 ,
wherein the peak filter provides for

Assignees

• Univ California
• Western Digital Tech Inc

Inventors

• Zheng Minghui
• Tomizuka Masayoshi
• Chen Xu
• Xi Wei
• Guo Guoxiao

Classifications

• G11B20/10046

  filtering or equalising, e.g. setting the tap weights of an FIR filter · CPC title

• G11B5/59627 Primary

  Aligning for runout, eccentricity or offset compensation (G11B5/5534, G11B5/59677, G11B5/59688 take precedence) · CPC title

• G11B5/556 Primary

  control circuits therefor · CPC title

• G11B5/4873

  the arm comprising piezoelectric or other actuators for adjustment of the arm · CPC title

• G11B5/59694

  System adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock · CPC title