Disk drive performing lifetime logging of microactuator sensitivity

1. A disk drive comprising:

a head;

a disk surface;

a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface; and

control circuitry operable to:

periodically measure a sensitivity of the microactuator over a lifetime of the microactuator; and

store each measured sensitivity in a timeline log, wherein the timeline log represents a degradation curve of the microactuator over the lifetime of the microactuator.

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

measure a temperature when measuring the sensitivity of the microactuator; and

store each measured temperature in the timeline log, wherein the timeline log represents a degradation curve of the microactuator versus temperature over the lifetime of the microactuator.

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

extrapolate the degradation curve over a window of the timeline log spanning at least two months; and

predict at least one of a performance degradation and a failure of the microactuator based on the extrapolated degradation curve.

4. The disk drive as recited in claim 3 , wherein the control circuitry is further operable to extrapolate the degradation curve by curve fitting the measured sensitivities to a pre-characterized degradation curve.

5. The disk drive as recited in claim 4 , wherein the control circuitry is further operable to curve fit the degradation curve to the pre-characterized degradation curve based on the measured temperatures.

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

extrapolate the degradation curve over a window of the timeline log spanning at least two months; and

recalibrate a gain of the microactuator based on the extrapolated degradation curve.

7. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to extrapolate the degradation by curve fitting the measured sensitivities to a pre-characterized degradation curve.

8. The disk drive as recited in claim 7 , wherein the control circuitry is further operable to curve fit the measured sensitivities to the pre-characterized degradation curve based on the measured temperatures.

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

extrapolate the degradation curve over a window of the timeline log spanning at least two months; and

predict a performance degradation of the microactuator based on the extrapolated degradation curve.

10. The disk drive as recited in claim 9 , wherein the control circuitry is further operable to extrapolate the degradation curve by curve fitting the measured sensitivities to a pre-characterized degradation curve.

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

extrapolate the degradation curve over a window of the timeline log spanning at least two months; and

predict a failure interval that the microactuator is expected to fail based on the extrapolated degradation curve.

12. The disk drive as recited in claim 11 , wherein the control circuitry is further operable to extrapolate the degradation curve by curve fitting the measured sensitivities to a pre-characterized degradation curve.

13. A method of operating a disk drive, the disk drive comprising a head, a disk surface, and a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface, the method comprising:

periodically measuring a sensitivity of the microactuator over a lifetime of the microactuator; and

storing each measured sensitivity in a timeline log, wherein the timeline log represents a degradation curve of the microactuator over the lifetime of the microactuator.

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

measuring a temperature when measuring the sensitivity of the microactuator; and

storing each measured temperature in the timeline log, wherein the timeline log represents a degradation curve of the microactuator versus temperature over the lifetime of the microactuator.

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

extrapolating the degradation curve over a window of the timeline log spanning at least two months; and

predicting at least one of a performance degradation and a failure of the microactuator based on the extrapolated degradation curve.

16. The method as recited in claim 15 , wherein extrapolating the degradation comprises curve fitting the measured sensitivities to a pre-characterized degradation curve.

17. The method as recited in claim 16 , further comprising curve fitting the measured sensitivities to the pre-characterized degradation curve based on the measured temperatures.

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

extrapolating the degradation curve over a window of the timeline log spanning at least two months; and

recalibrating a gain of the microactuator based on the extrapolated degradation curve.

19. The method as recited in claim 18 , wherein extrapolating the degradation curve comprises curve fitting the measured sensitivities to a pre-characterized degradation curve.

20. The method as recited in claim 19 , further comprising curve fitting the measured sensitivities to the pre-characterized degradation curve based on the measured temperatures.

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

extrapolating the degradation curve over a window of the timeline log spanning at least two months; and

predicting a performance degradation of the microactuator based on the extrapolated degradation curve.

22. The method as recited in claim 21 , wherein extrapolating the degradation curve comprises fitting the measured sensitivities to a pre-characterized degradation curve.

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

extrapolating the degradation curve over a window of the timeline log spanning at least two months; and

predicting a failure interval that the microactuator is expected to fail based on the extrapolated degradation curve.

24. The method as recited in claim 23 , wherein extrapolating the degradation curve comprises curve fitting the measured sensitivities to a pre-characterized degradation curve.