Hard disk drive head-disk interface dithering
A procedure for accurately determining thermal flying height control (TFC) touchdown power associated with a head-disk interface (HDI) in a hard disk drive (HDD) involves dithering the spacing corresponding to the HDI by applying an oscillating signal. The touchdown power with the HDI dithering applied is determined and, based on that and the dithering amplitude, the touchdown power without dithering applied, as well as the back-off power, is determinable.
1. A method for determining touchdown power associated with a head-disk interface (HDI) in a hard disk drive (HDD), the method comprising:
dithering the spacing corresponding to said HDI by applying an oscillating signal;
determining touchdown power with HDI dithering applied;
based on said touchdown power with HDI dithering applied, determining touchdown power without HDI dithering applied; and
storing, within said HDD, a characterization of said touchdown power without dithering applied.
2. The method of claim 1 , wherein determining said touchdown power without HDI dithering applied includes determining based on the amplitude of said dithering.
3. The method of claim 2 , wherein determining said touchdown power without HDI dithering includes computing the sum of said touchdown power with HDI dithering applied and said amplitude of said dithering.
4. The method of claim 1 , further comprising:
determining the amplitude of said dithering.
5. The method of claim 4 , wherein determining the amplitude of said dithering includes determining based on a signal from an embedded contact sensor (ECS).
6. The method of claim 4 , wherein determining the amplitude of said dithering includes determining based on a Wallace spacing loss relationship.
7. The method of claim 1 , wherein applying said oscillating signal includes applying a voltage between a head and a disk associated with said HDI.
8. The method of claim 1 , wherein applying said oscillating signal includes applying an oscillating component to a power signal for a thermal flying height control (TFC) heater element.
9. The method of claim 1 , wherein applying said oscillating signal includes applying said signal in a frequency range between the revolutions per minute (RPM) of said disk and the natural frequency of an air bearing surface of a slider on which a head associated with said HDI is mounted.
10. The method of claim 1 , wherein applying said oscillating signal includes applying said signal in a frequency range between 1 kHz-100 kHz.
11. A hard disk drive (HDD) comprising:
a disk medium rotatably mounted on a spindle;
a head slider comprising a read/write head configured to read from and to write to said disk medium;
a voice coil actuator configured to move said head slider to access portions of said disk medium; and
a least one electronic component comprising one or more sequences of instructions which, when executed by one or more processors, cause performance of:
dithering the spacing between said head slider and said disk medium by applying an oscillating signal;
determining touchdown power with head-disk interface (HDI) dithering applied;
based on said touchdown power with HDI dithering applied, determining touchdown power without HDI dithering applied;
storing, within said HDD, a characterization of said touchdown power without dithering applied; and
providing a back-off power signal to a thermal flying height control (TFC) heater element to achieve a particular spacing between said head slider and said disk medium.
12. The hard disk drive of claim 11 , said one or more sequences of instructions further causing performance of:
determining the amplitude of said dithering.
13. The hard disk drive of claim 12 , wherein determining said touchdown power without HDI dithering includes computing the sum of said touchdown power with HDI dithering applied and said amplitude of said dithering.
14. The hard disk drive of claim 12 , wherein determining the amplitude of said dithering includes determining based on a signal from an embedded contact sensor (ECS) or on a Wallace spacing loss relationship.
15. The hard disk drive of claim 11 , wherein applying said oscillating signal includes applying a voltage between said head and said disk medium.
16. The hard disk drive of claim 11 , wherein applying said oscillating signal includes applying an oscillating component to a power signal for a thermal flying height control (TFC) heater element.
17. The hard disk drive of claim 11 , wherein applying said oscillating signal includes applying said signal in a frequency range between the revolutions per minute (RPM) of said disk medium and the natural frequency of an air bearing surface of a slider on which said head is mounted.
18. An electronic component manufacture comprising one or more sequences of instructions which, when executed by one or more processors, cause performance of:
dithering the spacing between a head slider and a disk medium by applying an oscillating signal;
determining touchdown power with head-disk interface (HDI) dithering applied; and
based on said touchdown power with HDI dithering applied, determining touchdown power without HDI dithering applied.
19. The electronic component manufacture of claim 18 , said one or more sequences of instructions further causing performance of:
determining the amplitude of said dithering; and
wherein determining said touchdown power without HDI dithering includes computing the sum of said touchdown power with HDI dithering applied and said amplitude of said dithering.
20. The electronic component manufacture of claim 18 , wherein applying said oscillating signal includes applying a voltage between said head slider and said disk medium.
21. The electronic component manufacture of claim 18 , wherein applying said oscillating signal includes applying said signal in a frequency range between the revolutions per minute (RPM) of said disk medium and the natural frequency of an air bearing surface of said head slider.