Disk drive using timing loop control signal for vibration compensation in servo loop
View Patent ↗A disk drive is disclosed comprising a timing loop configured to generate a clock synchronized to a rotation of a disk and a servo loop configured to control an actuator to actuate a head over the disk. A timing signal generated by the timing loop is filtered with a pre-compensation filter (PCF) comprising an inverse transfer function from a delta in a rotation velocity of the disk (Δω) due to a vibration affecting the disk drive to the timing signal, and the actuator is controlled to actuate the head over the disk based on an output of the PCF.
1. A disk drive comprising:
a disk;
a head;
an actuator; and
control circuitry comprising a timing loop configured to generate a clock synchronized to a rotation of the disk and a servo loop configured to control the actuator to actuate the head over the disk, the control circuitry configured to:
filter a timing signal generated by the timing loop with a pre-compensation filter (PCF) comprising an inverse transfer function from a delta in a rotation velocity of the disk (Δω) due to a vibration affecting the disk drive to the timing signal; and
control the actuator to actuate the head over the disk based on an output of the PCF.
2. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to:
attenuate low frequency noise in the timing signal; and
control the actuator to actuate the head over the disk based on the noise attenuated timing signal.
3. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to:
attenuate a repeatable component (RC) of the timing signal; and
control the actuator to actuate the head over the disk based on the RC attenuated timing signal.
4. The disk drive as recited in claim 1 , wherein:
the timing signal comprises a timing error; and
the inverse transfer function comprises:
(1+ P t C t )· k
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of a compensator of the timing loop; and
k is a constant.
5. The disk drive as recited in claim 4 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to the timing error; and
f 0 represents a base frequency of the frequency generator.
6. The disk drive as recited in claim 1 , wherein:
the timing signal comprises a timing control signal output by a compensator of the timing loop; and
the inverse transfer function comprises:
(1+ P t C t )· k/C t
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of the compensator of the timing loop; and
k is a constant.
7. The disk drive as recited in claim 6 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to a timing error; and
f 0 represents a base frequency of the frequency generator.
8. A method of operating a disk drive, the method comprising:
filtering a timing signal generated by a timing loop with a pre-compensation filter (PCF) comprising an inverse transfer function from a delta in a rotation velocity of a disk (Δω) due to a vibration affecting the disk drive to the timing signal; and
controlling an actuator using a servo loop to actuate a head over the disk based on an output of the PCF.
9. The method as recited in claim 8 , further comprising:
attenuating low frequency noise in the timing signal; and
controlling the actuator to actuate the head over the disk based on the noise attenuated timing signal.
10. The method as recited in claim 8 , further comprising:
attenuating a repeatable component (RC) of the timing signal; and
controlling the actuator to actuate the head over the disk based on the RC attenuated timing signal.
11. The method as recited in claim 8 , wherein:
the timing signal comprises a timing error; and
the inverse transfer function comprises:
(1+ P t C t )· k
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of a compensator of the timing loop; and
k is a constant.
12. The method as recited in claim 11 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to the timing error; and
f 0 represents a base frequency of the frequency generator.
13. The method as recited in claim 8 , wherein:
the timing signal comprises a timing control signal output by a compensator of the timing loop; and
the inverse transfer function comprises:
(1+ P t C t )· k/C t
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of the compensator of the timing loop; and
k is a constant.
14. The method as recited in claim 13 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to a timing error; and
f 0 represents a base frequency of the frequency generator.
15. Control circuitry comprising:
a timing loop configured to generate a clock synchronized to a rotation of a disk of a disk drive that comprises a head and an actuator; and
a servo loop configured to control the actuator to actuate the head over the disk,
wherein the control circuitry configured to:
filter a timing signal generated by the timing loop with a pre-compensation filter (PCF) comprising an inverse transfer function from a delta in a rotation velocity of the disk (Δω) due to a vibration affecting the disk drive to the timing signal; and
control the actuator to actuate the head over the disk based on an output of the PCF.
16. The control circuitry as recited in claim 15 , wherein the control circuitry is further configured to:
attenuate low frequency noise in the timing signal; and
control the actuator to actuate the head over the disk based on the noise attenuated timing signal.
17. The control circuitry as recited in claim 15 , wherein the control circuitry is further configured to:
attenuate a repeatable component (RC) of the timing signal; and
control the actuator to actuate the head over the disk based on the RC attenuated timing signal.
18. The control circuitry as recited in claim 15 , wherein:
the timing signal comprises a timing error; and
the inverse transfer function comprises:
(1+ P t C t )· k
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of a compensator of the timing loop; and
k is a constant.
19. The control circuitry as recited in claim 18 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to the timing error; and
f 0 represents a base frequency of the frequency generator.
20. The control circuitry as recited in claim 15 , wherein:
the timing signal comprises a timing control signal output by a compensator of the timing loop; and
the inverse transfer function comprises:
(1+ P t C t )· k/C t
where:
P t represents a transfer function of a frequency generator of the timing loop;
C t represents a transfer function of the compensator of the timing loop; and
k is a constant.
21. The control circuitry as recited in claim 20 , wherein the constant k comprises
1/ k 0 f 0
where:
k 0 represents a ratio of Δω to a timing error; and
f 0 represents a base frequency of the frequency generator.