HARD DISK DRIVE REPEATABLE RUNOUT FEED FORWARD CANCELLATION WITH HIGH SPEED AND LOW POWER PHASE ROTATOR

Abstract

Embodiments of the present invention significantly reduce the number and complexity of processing operations to be performed. This is done by receiving the learned run out or vector A to be rotated by phase q. This phase q may be limited to a π/4 resolution. Sine function values and cosine function values based on q are selected from a group of values comprising −1, 0, and +1. The sine function values and cosine function values selected may then be applied to the learned run out or vector A to rotate the vector A by phase q. Because the sine and cosine values are limited to −1, 0 and +1 many multiplication processing operations are eliminated. This greatly simplifies the processing requirements associated with phase rotating of this learned run out.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein:

FIG. 1 depicts a pattern of radially-spaced concentric data tracks within the magnetic media of a disk;

FIG. 2 depicts a hard disk drive that includes a control circuitry, a hard disk, an actuator, a RW head and positioning arm in accordance with an embodiment of the present invention;

FIG. 3 is a functional block diagram of a disk controller in accordance with an embodiment of the present invention;

FIG. 4 provides a functional diagram of a prior art spindle frequency run-out cancellation module.

FIG. 5 provides a functional diagram of a spindle frequency run-out cancellation module with feed forward in accordance with an embodiment of the present invention;

FIG. 6 provides a table in accordance with an embodiment of the present invention;

FIG. 7 provides an NxFF learning functional diagram in accordance with an embodiment of the present invention;

FIG. 8 provides an NxFF functional diagram in accordance with an embodiment of the present invention;

FIGS. 9-24 provide simulation basis and simulation results associated with embodiments of the present invention.

Claims

1. A method to phase rotate a learned run out (vector A) Repeat Run Out (RRO) Feed-Forward cancellation system, comprising: receiving the learned run out (vector A) to be rotated by phase q;limiting phase q to a Π/4 resolution;selecting sine function values (α) and cosine function values (β) based on phase q, wherein α and β are selected from a group of values comprising −1, 0 and +1; andapplying α and β to sine function values and cosine function values associated with vector A to rotate vector A phase q.

2. The method of claim 1, wherein the selected values of α and β correspond to the sine and cosine functions corresponding to 0, Π/4, Π/2, 3Π/4 Π, 5Π/4, 3Π/2, and 7Π/4.

3. The method of claim 1, wherein the learned run out is used to generate a control signal to position a read/write (RW) head of a hard disk drive.

4. The method of claim 3, further comprising providing the control signal to an actuator coupled to the RW head to position the RW head over the data track in response to the control signal.

5. The method of claim 1, wherein RW head positioning error from a data track due to repeatable error is substantially removed from the PES.

6. The method of claim 1, wherein firmware within a Hard Disk Drive (HDD) controller implements the steps of claim 1.

7. A Spindle Frequency Run-out Cancellation system comprising: a first summing module operable to determine a position error signal (PES) from a measured read/write (RW) head position and a directed RW head position;a controller operable to generate a first control signal from the PES;a Feed Forward loop operable to generate a second control signal from the PES;a second summing module operable to produce a combined control signal from the first control signal and the second control signal; andan actuator operable to position the RW head over a data track based on the combined control signal.

8. The Spindle Frequency Run-out Cancellation system of claim 7, wherein the Feed Forward loop comprises: a DFT operable to receive the PES and generate a learned run out;a phase rotator operable to rotate the learned run out by a phase q, wherein q is limited to a Π/4 resolution;a vector integrator operable to produce integrated vector sine and cosine components; anda Feed Forward generator operable to produce the second control signal from the integrated vector sine and cosine components.

9. The Spindle Frequency Run-out Cancellation system of claim 8, wherein the phase rotator: selects sine function values (α) and cosine function values (β) based on phase q, wherein α and β are selected from a group of values comprising −1, 0 and +1; andapplies α and β to sine function values and cosine function values associated with the learned run out to rotate the learned run out by phase q.

10. The Spindle Frequency Run-out Cancellation system of claim 9, wherein the selected values of α and β correspond to the sine and cosine functions corresponding to 0, Π/4, Π/2, 3Π/4 Π, 5Π/4, 3Π/2, and 7Π/4.

11. The Spindle Frequency Run-out Cancellation system of claim 8, wherein combined control signal is used to position a RW head of a hard disk drive.

12. The Spindle Frequency Run-out Cancellation system of claim 11, wherein RW head positioning error from a data track due to repeatable error is substantially removed from the PES.

13. The Spindle Frequency Run-out Cancellation system of claim 11, wherein repeatable error substantially removed from the PES has a frequency corresponding to a harmonic of the spindle frequency.

14. The Spindle Frequency Run-out Cancellation system of claim 8, wherein the measured RW head position is derived from servo information.

15. A hard disk drive controller operable to substantially remove repeatable positioning errors from the read/write (RW) head position and a directed RW head position comprising: an interface module operable to couple the disk controller to a host computer system;a processing module coupled to a memory module wherein the processing module further comprises a Spindle Frequency Run-out Cancellation system, the Spindle Frequency Run-out Cancellation system comprises: a first summing module operable to determine a position error signal (PES) from a measured read/write (RW) head position and a directed RW head position;a controller operable to generate a first control signal from the PES;a Feed Forward loop operable to generate a second control signal from the PES;a second summing module operable to produce a combined control signal from the first control signal and the second control signal; andan actuator operably coupled to the processing module to position the RW head over a data track based on the combined control signal.

16. The hard disk drive controller of claim 15, wherein the Feed Forward loop comprises: a DFT operable to receive the PES and generate a learned run out;a phase rotator operable to rotate the learned run out by a phase q, wherein q is limited to a Π/4 resolution;a vector integrator operable to produce integrated vector sine and cosine components; anda Feed Forward generator operable to produce the second control signal from the integrated vector sine and cosine components.

17. The hard disk drive controller of claim 16, wherein the phase rotator: selects sine function values (α) and cosine function values (β) based on phase q, wherein α and β are selected from a group of values comprising −1, 0 and +1; andapplies α and β to sine function values and cosine function values associated with the learned run out to rotate the learned run out by phase q.

18. The hard disk drive controller of claim 17, wherein the selected values of α and β correspond to the sine and cosine functions corresponding to 0, Π/4, Π/2, 3Π/4 Π, 5Π/4, 3Π/2, and 7Π/4.

19. The hard disk drive controller of claim 15, wherein combined control signal is used to position a RW head of a hard disk drive.

20. The hard disk drive controller of claim 15, wherein the repeatable error substantially removed from the PES has a frequency corresponding to a harmonic of the spindle frequency.

21. The hard disk drive controller of claim 15, wherein the measured RW head position is derived from servo information within a hard disk.