Disk drives and disk drive containing devices that include a servo frequency generator and spindle control timer that compensate for disk eccentricity
View Patent ↗A disk includes an actuator assembly, a spindle motor and a disk that defines a plurality of servo wedges. A wedge to wedge timer is configured to measure the time elapsed between at least two circumferentially adjacent servo wedges and to output a wedge to wedge correction signal that defines a count between circumferentially adjacent servo wedges that is dependent upon the measured elapsed time. A servo frequency generator is configured to output a servo frequency generator signal having a frequency that is modulated by the wedge to wedge correction signal. A spindle motor control timer outputs a spindle control timer signal that is dependent upon the servo frequency generator signal and upon the time elapsed between at least two successive detections of circumferentially adjacent servo wedges. A spindle motor controller controls the spindle motor with a control signal that changes according to the spindle control timer signal.
1. A disk drive, comprising:
an actuator assembly having a read/write head;
a spindle motor;
a disk mounted for rotation on the spindle motor and including a recording surface having a plurality of tracks, each track including a plurality of servo wedges;
a wedge to wedge timer configured to measure a time elapsed between at least two successive detections of circumferentially adjacent servo wedges and to output a wedge to wedge correction signal that is dependent upon the measured elapsed time;
a servo frequency generator configured to output a servo frequency generator signal having a frequency that is modulated by the wedge to wedge correction signal;
a spindle motor control timer configured to output a spindle control timer signal that defines a count between circumferentially adjacent servo wedges that is dependent upon the servo frequency generator signal and upon the time elapsed between at least two successive detections of circumferentially adjacent servo wedges, and
a spindle motor controller for controlling the spindle motor with a control signal that changes according to the count of the spindle control timer signal.
2. The disk drive of claim 1 , wherein the spindle motor is configured to rotate at a desired rate that is independent of the count of the spindle control timer signal between circumferentially adjacent servo wedges.
3. The disk drive of claim 1 , wherein the spindle motor controller is configured to change the control signal according to the count of the spindle control timer signal.
4. A method for compensating for a once per revolution timing error in a disk drive having a spindle motor that rotates a disk, the method comprising the steps of:
rotating the disk, and while the disk is rotating:
measuring a wedge to wedge timing between at least two circumferentially adjacent servo wedges on a recording surface of the disk and outputting a wedge to wedge correction signal that is dependent upon the measured elapsed time;
generating a servo frequency signal that is modulated by the wedge to wedge correction signal;
generating a spindle control timer signal that defines a count between circumferentially adjacent servo wedges that is dependent upon the servo frequency generator signal and upon the wedge to wedge timing between at least two circumferentially adjacent servo wedges, and
controlling the spindle motor with a control signal that changes according to the count of the spindle control timer signal.
5. The method of claim 4 , wherein the rotating step rotates the disk at a desired rate that is independent of the count of the spindle control timer signal between circumferentially adjacent servo wedges.
6. The method of claim 4 , wherein the control signal in the controlling step is configured to change according to the count of the spindle control timer signal.
7. A mobile host device, comprising:
an enclosure;
a disk drive coupled to the enclosure, the disk drive including:
an actuator assembly having a read/write head;
a spindle motor;
a disk mounted for rotation on the spindle motor and including a recording surface having a plurality of tracks, each track including a plurality of servo wedges;
a wedge to wedge timer configured to measure a time elapsed between at least two successive detections of circumferentially adjacent servo wedges and to output a wedge to wedge correction signal that is dependent upon the measured elapsed time;
a servo frequency generator configured to output a servo frequency generator signal having a frequency that is modulated by the wedge to wedge correction signal;
a spindle control timer configured to output a spindle control timer signal that defines a count between circumferentially adjacent servo wedges that is dependent upon the servo frequency generator signal and upon the time elapsed between at least two successive detections of circumferentially adjacent servo wedges, and
a spindle motor controller for controlling the spindle motor with a control signal that changes according to the count of the spindle control timer signal.
8. The mobile host device of claim 7 , wherein the spindle motor is configured to rotate at a desired rate that is independent of the count of the spindle control timer signal between circumferentially adjacent servo wedges.
9. The mobile host of claim 7 , wherein the spindle motor controller is configured to change the control signal according to the count of the spindle control timer signal.