Disk drive generating feed-forward fly height control based on temperature sensitive fly height sensor

• US 8,922,939 B1
• Filed: 06/20/2013
• Issued: 12/30/2014
• Est. Priority Date: 04/02/2013
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Knigge, Bernhard E., Xu, Jian
• Primary Examiner(s): Wong, K.
• Application Number:
  US13/922,417
• Time in Patent Office: 558 Days
• Field of Search: None
• US Class Current: 360/75
• CPC Class Codes: G11B 5/6058 using piezoelectric means
• CPC Class Codes: G11B 5/607 using thermal means

Abstract

A disk drive is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator (FHA) operable to actuate the head vertically over the disk. The head further comprises a temperature sensitive fly height sensor (TSS) operable to generate a fly height signal (FHS) representing a fly height of the head over the disk. An FHA actuation curve is measured for the FHA, and a conversion function is configured based on the FHA actuation curve, wherein the conversion function is operable to convert the FHS in first units (e.g., volts) into a corresponding fly height (FH) of the head in second units (e.g., nm).

Claims

1. A disk drive comprising:

a disk;

a head actuated over the disk, the head comprising a fly height actuator (FHA) and a temperature sensitive fly height sensor operable to generate a fly height signal (FHS) representing a fly height of the head over the disk; and

control circuitry operable to;

measure a FHA actuation curve for the FHA; and

configure a conversion function based on the FHA actuation curve, wherein the conversion function is operable to convert the FHS in first units of measurement into a corresponding fly height (FH) of the head in second units of measurement.

2. The disk drive as recited in claim 1, wherein the control circuitry is further operable to:

generate feed-forward (FF) control based on the FHS and the conversion function; and

generate an FHA control signal based on the FF control so that the head follows a topography variation of the disk.

3. The disk drive as recited in claim 2, wherein the control circuitry is further operable to generate the FF control based on an error between the FH of the head generated by the conversion function and a target fly height.

4. The disk drive as recited in claim 1, wherein the control circuitry is further operable to generate the FHA actuation curve while servoing the head near an inner diameter of the disk.

5. The disk drive as recited in claim 2, wherein the control circuitry is further operable to generate the FF control as a waveform representing the topography variation of the disk.

6. The disk drive as recited in claim 5, wherein the control circuitry is further operable to generate the FF control by varying an amplitude of the waveform representing the topography variation of the disk until a difference between the FH of the head generated by the conversion function and a target fly height falls below a threshold.

7. The disk drive as recited in claim 5, wherein the control circuitry is further operable to generate the FF control by varying a phase of the waveform representing the topography variation of the disk until a difference between the FH of the head generated by the conversion function and a target fly height falls below a threshold.

8. The disk drive as recited in claim 5, wherein the control circuitry is further operable to dither the FF control representing the waveform to increase an effective resolution of the FF control.

9. The disk drive as recited in claim 5, wherein the control circuitry is further operable to generate the FF control representing the waveform at multiple radial locations across the disk.

10. The disk drive as recited in claim 1, wherein the control circuitry is further operable to calibrate the conversion function over a plurality of different environmental conditions.

11. The disk drive as recited in claim 10, wherein the environmental conditions comprise a plurality of different ambient temperatures of the disk drive.

12. The disk drive as recited in claim 1, wherein the control circuitry is further operable to evaluate a waviness of the disk based on the FH of the head in the second units.

13. A method of operating a disk drive comprising a disk, a head actuated over the disk, the head comprising a fly height actuator (FHA) and a temperature sensitive fly height sensor operable to generate a fly height signal (FHS) representing a fly height of the head over the disk, the method comprising:

measuring a FHA actuation curve for the FHA; and

configuring a conversion function based on the FHA actuation curve, wherein the conversion function is operable to convert the FHS in first units of measurement into a corresponding fly height (FH) of the head in second units of measurement.

14. The method as recited in claim 13, further comprising:

generating feed-forward (FF) control based on the FHS and the conversion function; and

generating an FHA control signal based on the FF control so that the head follows a topography variation of the disk.

15. The method as recited in claim 14, further comprising generating the FF control based on an error between the FH of the head generated by the conversion function and a target fly height.

16. The method as recited in claim 13, further comprising generating the FHA actuation curve while servoing the head near an inner diameter of the disk.

17. The method as recited in claim 14, further comprising generating the FF control as a waveform representing the topography variation of the disk.

18. The method as recited in claim 17, further comprising generating the FF control by varying an amplitude of the waveform representing the topography variation of the disk until a difference between the FH of the head generated by the conversion function and a target fly height falls below a threshold.

19. The method as recited in claim 17, further comprising generating the FF control by varying a phase of the waveform representing the topography variation of the disk until a difference between the FH of the head generated by the conversion function and a target fly height falls below a threshold.

20. The method as recited in claim 17, further comprising dithering the FF control representing the waveform to increase an effective resolution of the FF control.

21. The method as recited in claim 17, further comprising generating the FF control representing the waveform at multiple radial locations across the disk.

22. The method as recited in claim 13, further comprising calibrating the conversion function over a plurality of different environmental conditions.

23. The method as recited in claim 22, wherein the environmental conditions comprise a plurality of different ambient temperatures of the disk drive.

24. The method as recited in claim 13, further comprising evaluating a waviness of the disk based on the FH of the head in the second units.