Method for wedge time shift calibration in a disk drive
View Patent ↗A method is disclosed for identifying wedge time shift zones on a magnetic disk of a disk drive. The disk drive further includes a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, and a head that is actuated over the disk. During operation, the control systems causes a seek of the head across the disk and measures wedge-to-wedge times between servo wedges. The control system then calculates a wedge-to-wedge time shift value using the wedge-to-wedge times and determines whether the wedge-to-wedge time shift time value exceeds a predetermined threshold. If the wedge-to-wedge time shift value exceeds the predetermined threshold, then the control system identifies a wedge time shift zone, and stores information for compensating for the identified wedge time shift zone during disk operations.
1. A method for wedge time shift calibration in a disk drive, the disk drive comprising a disk, a head actuated over the disk, and a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, the disk having a plurality of spaced-apart embedded servo wedges that define a plurality of concentric data tracks, the method comprising the steps of:
(a) seeking across the disk and measuring wedge-to-wedge times between servo wedges;
(b) calculating a wedge-to-wedge time shift value using the wedge-to-wedge times;
(c) determining whether the wedge-to-wedge time shift time value exceeds a predetermined threshold;
(d) if the wedge-to-wedge time shift value exceeds the predetermined threshold, then identifying a wedge time shift zone; and
(e) storing information for compensating for the identified wedge time shift zone during disk operations.
2. A method for wedge time shift calibration as defined in claim 1 , wherein the identified wedge time shift zone comprises a zone start cylinder and a zone end cylinder.
3. A method for wedge time shift calibration as defined in claim 2 , wherein the step of storing information for compensating for the identified wedge time shift zone further comprises storing the wedge-to-wedge time shift value corresponding to the zone start cylinder and the wedge-to-wedge time shift value corresponding to the zone end cylinder in nonvolatile memory.
4. A method for wedge time shift calibration as defined in claim 1 , further comprising continuing the seek from an outer diameter to an inner diameter of the disk and, for each identified wedge time shift zone, storing information for compensating for each identified wedge time shift zone during disk operations.
5. A method for wedge time shift calibration as defined in claim 1 , further comprising continuing the seek from an inner diameter to an outer diameter of the disk and, for each identified wedge time shift zone, storing information for compensating for each identified wedge time shift zone during disk operations.
6. A disk drive, comprising:
a magnetic disk having a plurality of spaced-apart embedded servo wedges that define a plurality of concentric data tracks;
a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system;
a head actuated over the disk;
a control system for:
seeking across the disk and measuring wedge-to-wedge times between servo wedges;
calculating a wedge-to-wedge time shift value using the wedge-to-wedge times;
determining whether the wedge-to-wedge time shift time value exceeds a predetermined threshold;
if the wedge-to-wedge time shift value exceeds the predetermined threshold, then identifying a wedge time shift zone; and
storing information for compensating for the identified wedge time shift zone during disk operations.
7. A disk drive as defined in claim 6 , wherein the identified wedge time shift zone comprises a zone start cylinder and a zone end cylinder.
8. A disk drive as defined in claim 7 , wherein storing information for compensating for the identified wedge time shift zone further comprises storing the wedge-to-wedge time shift value corresponding to the zone start cylinder and the wedge-to-wedge time shift value corresponding to the zone end cylinder in nonvolatile memory.
9. A disk drive as defined in claim 6 , wherein the control system is further for continuing the seek from an outer diameter to an inner diameter of the disk and, for each identified wedge time shift zone, storing information for compensating for each identified wedge time shift zone.
10. A disk drive as defined in claim 6 , wherein the control system is further for continuing the seek from an inner diameter to an outer diameter of the disk, for each identified wedge time shift zone, storing information for compensating for each identified wedge time shift zone.
11. A magnetic disk of a disk drive, comprising:
a plurality of spaced-apart embedded servo wedges that define a plurality of concentric data tracks;
at least one wedge time shift zone; and
stored information for compensating for a wedge time shift zone during disk operations wherein the stored information for compensating for a wedge time shift zone comprises a zone start cylinder and a zone end cylinder.
12. A magnetic disk as defined in claim 11 , wherein the stored information for compensating for a wedge time shift zone further comprises a wedge-to-wedge time shift value corresponding to the zone start cylinder and a wedge-to-wedge time shift value corresponding to the zone end cylinder.