Disk drive determining touchdown threshold
View Patent ↗A disk drive is disclosed comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator for controlling a fly height of the head over the disk in response to a DFH setting. A touchdown (TD) threshold is initialized, and the DFH setting that causes a TD signal to exceed the TD threshold is determined. The TD threshold is adjusted, and the DFH setting that causes the TD signal to exceed the adjusted TD threshold is determined. A slope of the DFH setting relative to the TD threshold is determined, and an operating TD threshold is determined in response to a change in the slope.
1. A disk drive comprising:
a disk;
a head actuated over the disk;
a dynamic fly height (DFH) actuator for controlling a fly height of the head over the disk in response to a DFH setting; and
control circuitry operable to:
initialize a touchdown (TD) threshold;
determine the DFH setting that causes a TD signal to exceed the TD threshold;
adjust the TD threshold;
determine the DFH setting that causes the TD signal to exceed the adjusted TD threshold;
determine a slope of the DFH setting relative to the TD threshold; and
determine an operating TD threshold in response to a change in the slope.
2. The disk drive as recited in claim 1 , further comprising a TD sensor operable to generate the TD signal.
3. The disk drive as recited in claim 2 , wherein the TD sensor is integrated with the head.
4. The disk drive as recited in claim 2 , wherein the TD sensor comprises a microactuator for actuating the head over the disk.
5. The disk drive as recited in claim 2 , wherein:
the head is coupled to a distal end of an actuator arm; and
the TD sensor is coupled to the actuator arm.
6. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to determine the operating TD threshold in response to when a derivative of the slope exceeds a threshold.
7. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to determine the operating TD threshold by:
detecting when the slope exceeds a first threshold; and
after detecting when the slope exceeds the first threshold, detecting when the slope exceeds a second threshold.
8. The disk drive as recited in claim 7 , wherein the control circuitry is further operable to determine the operating TD threshold by:
detecting when the slope rises above a first threshold; and
after detecting when the slope rises above the first threshold, detecting when the slope falls below a second threshold.
9. The disk drive as recited in claim 1 , wherein the control circuitry adjusts the TD threshold by increasing the TD threshold.
10. The disk drive as recited in claim 1 , wherein the control circuitry adjusts the TD threshold by decreasing the TD threshold.
11. A method of operating a disk drive comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator for controlling a fly height of the head over the disk in response to a DFH setting, the method comprising:
initializing a touchdown (TD) threshold;
determining the DFH setting that causes a TD signal to exceed the TD threshold;
adjusting the TD threshold;
determining the DFH setting that causes the TD signal to exceed the adjusted TD threshold;
determining a slope of the DFH setting relative to the TD threshold; and
determining an operating TD threshold in response to a change in the slope.
12. The method as recited in claim 11 , wherein the disk drive further comprises a TD sensor operable to generate the TD signal.
13. The method as recited in claim 12 , wherein the TD sensor is integrated with the head.
14. The method as recited in claim 12 , wherein the TD sensor comprises a microactuator for actuating the head over the disk.
15. The method as recited in claim 12 , wherein:
the head is coupled to a distal end of an actuator arm; and
the TD sensor is coupled to the actuator arm.
16. The method as recited in claim 11 , further comprising determining the operating TD threshold in response to when a derivative of the slope exceeds a threshold.
17. The method as recited in claim 16 , further comprising determining the operating TD threshold by:
detecting when the slope exceeds a first threshold; and
after detecting when the slope exceeds the first threshold, detecting when the slope exceeds a second threshold.
18. The method as recited in claim 17 , further comprising determining the operating TD threshold by:
detecting when the slope rises above a first threshold; and
after detecting when the slope rises above the first threshold, detecting when the slope falls below a second threshold.
19. The method as recited in claim 11 , further comprising adjusting the TD threshold by increasing the TD threshold.
20. The method as recited in claim 11 , further comprising adjusting the TD threshold by decreasing the TD threshold.