Hysteresis compensation in a disc drive

Patent metadata

Field	Value
Publication number	US-10068598-B2
Application number	US-201815915520-A
Country	US
Kind code	B2
Filing date	Mar 8, 2018
Priority date	Jun 1, 2016
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

Systems and methods for compensating for hysteresis in a disc drive are described. In one embodiment, a method may use an inverse hysteresis model to linearize effects of hysteresis of a microactuator in the disc drive. The hysteresis model may be a Coleman-Hodgdon hysteresis model. The hysteresis of the microactuator may be characterized, and the inverse hysteresis model may be based at least in part on the characterization. The inverse hysteresis model may be used to implement a digital filter. The digital filter may be employed in series with the microactuator to linearize the effects of hysteresis.

First claim

What is claimed is:

1. A storage device comprising:
a data storage medium;
a microactuator configured to move one or more read/write heads relative to the data storage medium; and
a servo controller to apply a direct current (DC) voltage to the microactuator to drive a pair of heads from the one or more read/write heads out of phase, and to repetitively adjust the DC voltage and apply the adjusted DC voltage until adjustments to the DC voltage cover an entire driving range of the microactuator.

2. The storage device of claim 1 , the servo controller being set to a single-stage mode until adjustments to the DC voltage cover an entire driving range of the microactuator, wherein the servo controller is set to a dual-stage mode upon determining adjustments to the DC voltage cover the entire driving range of the microactuator.

3. The storage device of claim 1 , comprising one or more processors configured to determine a baseline direct current skew for the pair of heads.

4. The storage device of claim 3 , wherein determining the baseline DC skew is based at least in part on performing a head switch relative to the pair of heads.

5. The storage device of claim 4 , the one or more processors to measure a change in DC skew relative to the pair of heads.

6. The storage device of claim 3 , the one or more processors to repetitively measure the change in DC skew for each adjusted DC voltage until adjustments to the DC voltage cover an entire driving range of the microactuator.

7. The storage device of claim 3 , the one or more processors to generate a hysteresis curve based at least in part on the repeated applying of the DC voltage and measuring of the change in DC skew over the entire driving range of the microactuator.

8. The storage device of claim 3 , the one or more processors to generate a hysteresis model of the microactuator based at least in part on the repeated applying of the DC voltage and measuring of the change in DC skew over the entire driving range of the microactuator.

9. The storage device of claim 8 , the one or more processors to implement a hysteresis compensator based at least in part on an inverse of the hysteresis model.

10. The storage device of claim 9 , wherein the hysteresis compensator includes a digital filter placed in series with the microactuator.

11. A method comprising:
moving one or more read/write heads relative to a data storage medium;
applying a DC voltage to a microactuator to drive a pair of heads from the one or more read/write heads out of phase;
repetitively adjusting the DC voltage; and
applying the adjusted DC voltage to the microactuator until adjustments to the DC voltage cover an entire driving range of the microactuator.

12. The method of claim 11 , further comprising providing a servo controller to apply the DC voltage, repetitively adjust the DC voltage, and apply the adjusted DC voltage, the servo controller being set to a single-stage mode until adjustments to the DC voltage cover an entire driving range of the microactuator, wherein the servo controller is set to a dual-stage mode upon determining adjustments to the DC voltage cover the entire driving range of the microactuator.

13. The method of claim 11 , further comprising:
determining a baseline direct current (DC) skew for the pair of heads.

14. The method of claim 13 , wherein determining the baseline DC skew is based at least in part on performing a head switch relative to the pair of heads.

15. The method of claim 14 , further comprising:
measuring a change in DC skew relative to the pair of heads.

16. The method of claim 15 , further comprising:
repetitively measuring the change in DC skew for each adjusted DC voltage until adjustments to the DC voltage cover an entire driving range of the microactuator.

17. The method of claim 13 , further comprising:
generating a hysteresis curve based at least in part on the repeated applying of the DC voltage and measuring of the change in DC skew over the entire driving range of the microactuator.

18. The method of claim 13 , further comprising:
generating a hysteresis model of the microactuator based at least in part on the repeated applying of the DC voltage and measuring of the change in DC skew over the entire driving range of the microactuator.

19. An apparatus comprising:
a data storage medium;
a microactuator configured to move one or more read/write heads relative to the data storage medium; and
a servo controller to apply a DC voltage to the microactuator to drive a pair of heads from the one or more read/write heads out of phase, and to repetitively adjust the DC voltage and apply the adjusted DC voltage until adjustments to the DC voltage cover an entire driving range of the microactuator.

20. The apparatus of claim 19 , the servo controller being set to a single-stage mode until adjustments to the DC voltage cover an entire driving range of the microactuator, wherein the servo controller is set to a dual-stage mode upon determining adjustments to the DC voltage cover the entire driving range of the microactuator.

Assignees

• Seagate Technology Llc

Inventors

• Hanson Reed D
• Haapala Kenneth A
• Kinney Dwight R
• Huang Xinghui

Classifications

• G11B5/59622

  Gain control; Filters · CPC title

• G11B5/4873

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

• G11B5/556 Primary

  control circuits therefor · CPC title