Disk drive implementing hysteresis for primary shock detector based on a more sensitive secondary shock detector
View Patent ↗A disk drive is disclosed comprising a head actuated over a disk, and control circuitry comprising a first shock detector and a second shock detector. A first number of shock events is detected based on the first shock detector, and when the first number of shock events exceeds an upper event threshold, a sensitivity of the first shock detector is decreased. After decreasing the sensitivity of the first shock detector, a second number of shock events is detected based on the second shock detector operating at a higher sensitivity than the first shock detector. When the second number of shock events falls below a lower event threshold, the sensitivity of the first shock detector is increased.
1. A disk drive comprising:
a disk;
a head actuated over the disk; and
control circuitry comprising a first shock detector and a second shock detector, the control circuitry operable to:
detect a first number of shock events based on the first shock detector;
when the first number of shock events exceeds an upper event threshold, decrease a sensitivity of the first shock detector;
after decreasing the sensitivity of the first shock detector, detect a second number of shock events based on the second shock detector operating at a higher sensitivity than the first shock detector; and
when the second number of shock events falls below a lower event threshold, increase the sensitivity of the first shock detector.
2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to adjust the sensitivity of the first shock detector by adjusting a first shock threshold of the first shock detector.
3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to adjust the sensitivity of the first shock detector by adjusting a gain of the first shock detector.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
filter a shock signal emanating from a shock sensor to generate a filtered shock signal, wherein the first shock detector is responsive to the filtered shock signal; and
adjust the sensitivity of the first shock detector by adjusting a bandwidth of the filtering.
5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
when increasing the sensitivity of the first shock detector, increase a sensitivity of the second shock detector; and
when decreasing the sensitivity of the first shock detector, decrease the sensitivity of the second shock detector.
6. The disk drive as recited in claim 1 , wherein the first shock detector detects shock events at a lower frequency than the second shock detector.
7. The disk drive as recited in claim 6 , wherein:
the disk comprises a plurality of servo sectors;
the first shock detector is capable of detecting a single shock event between consecutive servo sectors; and
the second shock detector is capable of detecting multiple shock events between consecutive servo sectors.
8. The disk drive as recited in claim 7 , wherein the control circuitry is operable to abort a write operation when the first shock detector detects the single shock event.
9. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
filter a shock signal emanating from a shock sensor to generate a filtered shock signal, wherein the first shock detector compares the filtered shock signal to a first shock threshold;
decrease the sensitivity of the first shock detector by increasing the first shock threshold; and
when the first shock threshold reaches a maximum, decrease the sensitivity of the first shock detector by decreasing a bandwidth of the filtering.
10. The disk drive as recited in claim 1 , wherein the control circuitry is operable to abort a write operation based on the first shock detector.
11. A method of operating a disk drive comprising:
detecting a first number of shock events based on a first shock detector;
when the first number of shock events exceeds an upper event threshold, decreasing a sensitivity of the first shock detector;
after decreasing the sensitivity of the first shock detector, detecting a second number of shock events based on a second shock detector operating at a higher sensitivity than the first shock detector; and
when the second number of shock events falls below a lower event threshold, increasing the sensitivity of the first shock detector.
12. The method as recited in claim 11 , further comprising adjusting the sensitivity of the first shock detector by adjusting a first shock threshold of the first shock detector.
13. The method as recited in claim 11 , further comprising adjusting the sensitivity of the first shock detector by adjusting a gain of the first shock detector.
14. The method as recited in claim 11 , further comprising:
filtering a shock signal emanating from a shock sensor to generate a filtered shock signal, wherein the first shock detector is responsive to the filtered shock signal; and
adjusting the sensitivity of the first shock detector by adjusting a bandwidth of the filtering.
15. The method as recited in claim 11 , further comprising:
when increasing the sensitivity of the first shock detector, increasing a sensitivity of the second shock detector; and
when decreasing the sensitivity of the first shock detector, decreasing the sensitivity of the second shock detector.
16. The method as recited in claim 11 , wherein the first shock detector detects shock events at a lower frequency than the second shock detector.
17. The method as recited in claim 16 , wherein:
the disk drive comprises a disk comprising a plurality of servo sectors;
the first shock detector is capable of detecting a single shock event between consecutive servo sectors; and
the second shock detector is capable of detecting multiple shock events between consecutive servo sectors.
18. The method as recited in claim 17 , further comprising aborting a write operation when the first shock detector detects the single shock event.
19. The method as recited in claim 11 , further comprising:
filtering a shock signal emanating from a shock sensor to generate a filtered shock signal, wherein the first shock detector compares the filtered shock signal to a first shock threshold;
decreasing the sensitivity of the first shock detector by increasing the first shock threshold; and
when the first shock threshold reaches a maximum, decrease the sensitivity of the first shock detector by decreasing a bandwidth of the filtering.
20. The method as recited in claim 11 , further comprising aborting a write operation to a disk based on the first shock detector.