Disk drive detecting defective spiral servo track
AssigneeWestern Digital Technologies, Inc.
InventorsJiangang Liang, Siri S. Weerasooriya
Life of this patent
Estimating the term…
Abstract
A disk drive is disclosed comprising a disk and a head actuated over the disk, wherein the disk comprises a plurality of spiral tracks, each comprising a high frequency signal interrupted by a sync mark at a sync mark interval. The head is used to read a spiral track to generate a spiral track crossing signal g(xn), where xn is a time in a demodulation window. A position error signal (PES) is determined in response to g(xn), and a deviation index is computed by correlating g(xn) with a nominal track crossing signal shifted by the PES. When the deviation index is less than a threshold, the PES is used to servo the head over the disk.
Claims16
A disk drive comprising:
- a disk comprising a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval;
- a head actuated over the disk;
- and
- control circuitry operable to:
- use the head to read a spiral track to generate a spiral track crossing signal g(xn), where xn is a time in a demodulation window;
- determine a position error signal (PES) in response to g(xn);
- compute a deviation index by correlating g(xn) with a nominal track crossing signal shifted by the PES;
- and
- when the deviation index is less than a threshold, use the PES to servo the head over the disk.
A method of operating a disk drive, the disk drive comprising a disk and a head actuated over the disk, wherein the disk comprises a plurality of spiral tracks each comprising a high frequency signal interrupted by a sync mark at a sync mark interval, the method comprising:
- using the head to read a spiral track to generate a spiral track crossing signal g(xn), where xn is a time in a demodulation window;
- determining a position error signal (PES) in response to g(xn);
- computing a deviation index by correlating g(xn) with a nominal track crossing signal shifted by the PES;
- and
- when the deviation index is less than a threshold, using the PES to servo the head over the disk.
Dependencies are inferred from the claim text.