Disk drive compensating for repeatable run out selectively per zone

Patent metadata

Field	Value
Publication number	US-8953271-B1
Application number	US-201313928845-A
Country	US
Kind code	B1
Filing date	Jun 27, 2013
Priority date	May 13, 2013
Publication date	Feb 10, 2015
Grant date	Feb 10, 2015

Abstract

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors. A plurality of zones are defined, wherein each zone comprises a plurality of the servo tracks. A metric is generated for each zone, and when the metric for a first zone exceeds a first threshold, feedback compensation values for at least two servo tracks are generated, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track. When the metric for a second zone does not exceed the first threshold, generating feedback compensation values for the second zone is skipped.

First claim

What is claimed is:

1. A disk drive comprising:
a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors;
a head actuated over the disk; and
control circuitry operable to:
define a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generate a metric for each zone;
when the metric for a first zone exceeds a first threshold, generate feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skip generating feedback compensation values for the second zone;
generate a position error signal (PES) representing a difference between a measured position of the head and a target position;
generate a repeatable disturbance for each of a plurality of tracks in each zone based on the PES; and
generate the metric for each zone as an average magnitude of the repeatable disturbance generated for the plurality of tracks.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to write the feedback compensation values generated for each servo track to each servo track.

3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
average the metrics generated for the zones to generate an average metric; and
when the metric for the second zone does not exceed the first threshold and the average metric exceeds a second threshold, generate feedback compensation values for the second zone.

4. A method of operating a disk drive comprising a head actuated over a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, the method comprising:
defining a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generating a metric for each zone;
when the metric for a first zone exceeds a first threshold, generating feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skipping generating feedback compensation values for the second zone;
generating a position error signal (PES) representing a difference between a measured position of the head and a target position;
generating a repeatable disturbance for each of a plurality of tracks in each zone based on the PES; and
generating the metric for each zone as an average magnitude of the repeatable disturbance generated for the plurality of tracks.

5. The method as recited in claim 4 , further comprising writing the feedback compensation values generated for each servo track to each servo track.

6. The method as recited in claim 4 , further comprising:
averaging the metrics generated for the zones to generate an average metric; and
when the metric for the second zone does not exceed the first threshold and the average metric exceeds a second threshold, generating feedback compensation values for the second zone.

7. A disk drive comprising:
a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors;
a head actuated over the disk; and
control circuitry operable to:
define a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generate a metric for each zone;
when the metric for a first zone exceeds a first threshold, generate feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skip generating feedback compensation values for the second zone;
generate a position error signal (PES) representing a difference between a measured position of the head and a target position;
generate a non-repeatable disturbance for each of a plurality of tracks in each zone based on the PES; and
generate the metric for each zone as an average magnitude of the non-repeatable disturbance generated for the plurality of tracks.

8. A method of operating a disk drive comprising a head actuated over a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, the method comprising:
defining a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generating a metric for each zone;
when the metric for a first zone exceeds a first threshold, generating feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skipping generating feedback compensation values for the second zone;
generating a position error signal (PES) representing a difference between a measured position of the head and a target position;
generating a non-repeatable disturbance for each of a plurality of tracks in each zone based on the PES; and
generating the metric for each zone as an average magnitude of the non-repeatable disturbance generated for the plurality of tracks.

9. A disk drive comprising:
a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors;
a head actuated over the disk; and
control circuitry operable to:
define a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generate a metric for each zone;
when the metric for a first zone exceeds a first threshold, generate feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skip generating feedback compensation values for the second zone;
average the metrics generated for the zones to generate an average metric; and
when the metric for the second zone does not exceed the first threshold and the average metric exceeds a second threshold, generate feedback compensation values for the second zone.

10. A method of operating a disk drive comprising a head actuated over a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, the method comprising:
defining a plurality of zones, wherein each zone comprises a plurality of the servo tracks;
generating a metric for each zone;
when the metric for a first zone exceeds a first threshold, generating feedback compensation values for at least two servo tracks, wherein the feedback compensation values compensate for a written-in error of the servo sectors of each servo track;
when the metric for a second zone does not exceed the first threshold, skipping generating feedback compensation values for the second zone;
averaging the metrics generated for the zones to generate an average metric; and
when the metric for the second zone does not exceed the first threshold and the average metric exceeds a second threshold, generating feedback compensation values for the second zone.

Assignees

• Western Digital Tech Inc

Inventors

• Chayarangkan Tanaat Wut
• Kungsadankosit Julasak
• Jittramatr Thitinun
• Samuhatananon Siam
• Choong Chin Yang
• Chen Wei Kiat
• Wu Eugene Chun-Tsing

Classifications

• G11B5/59627 Primary

  Aligning for runout, eccentricity or offset compensation (G11B5/5534, G11B5/59677, G11B5/59688 take precedence) · CPC title