Data storage device employing adaptive feed-forward control in timing loop to compensate for vibration
A data storage device is disclosed comprising a head actuated over a disk and a vibration detector configured to generate a vibration signal in response to a vibration affecting the data storage device. A timing loop is configured to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk. An adaptation control signal is generated based on the vibration signal and an error signal of the timing loop. An adaptive filter is adapted based on the adaptation control signal, wherein the adaptive filter filters the vibration signal to generate feed-forward compensation values. The feed-forward compensation values are applied to the timing loop to compensate for the vibration.
1. A data storage device comprising:
a disk;
a head actuated over the disk;
a vibration detector configured to generate a vibration signal in response to a vibration affecting the data storage device; and
control circuitry comprising a timing loop configured to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk, the control circuitry configured to:
generate an adaptation control signal based on the vibration signal and an error signal of the timing loop;
adapt an adaptive filter based on the adaptation control signal, wherein the adaptive filter filters the vibration signal to generate feed-forward compensation values; and
apply the feed-forward compensation values to the timing loop to compensate for the vibration.
2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
filter the vibration signal to generate a compensated vibration signal; and
generate the adaptation control signal based on the compensated vibration signal and the error signal.
3. The data storage device as recited in claim 2 , wherein filtering the vibration signal to generate the compensated vibration signal comprises filtering the vibration signal with a filter representing a torque rejection curve of the timing loop.
4. The data storage device as recited in claim 2 , wherein the control circuitry is operable to adapt the adaptive filter according to:
W k+1 =W k +μ∥ X k e k
where:
W k represents coefficients of the adaptive filter;
μ represents a learning coefficient;
X k represents the compensated vibration signal; and
e k represents the error signal.
5. The data storage device as recited in claim 1 , wherein the vibration detector comprises:
a vibration sensor configured to generate a sensor signal; and
a pre-compensation filter (PCF) configured to filter the sensor signal to generate the vibration signal, wherein the PCF compensates for a transfer function of the vibration sensor.
6. A data storage device comprising:
a disk comprising a plurality of servo sectors defining servo tracks;
a head actuated over the disk, the head comprising a first read element and a second read element; and
control circuitry configured to:
measure a first wedge-to-wedge time representing a time between consecutive servo sectors passing under the first read element as the disk rotates;
measure a second wedge-to-wedge time representing a time between consecutive servo sectors passing under the second read element as the disk rotates; and
generate a nominal wedge-to-wedge time based on the first wedge-to-wedge time and the second wedge-to-wedge time.
7. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to generate the nominal wedge-to-wedge time based on an average of the first wedge-to-wedge time and the second wedge-to-wedge time.
8. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk based on the nominal wedge-to-wedge time.
9. A method of operating a data storage device, the method comprising:
using a timing loop to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk;
generating an adaptation control signal based on a vibration signal and an error signal of the timing loop;
adapting an adaptive filter based on the adaptation control signal, wherein the adaptive filter filters the vibration signal to generate feed-forward compensation values; and
applying the feed-forward compensation values to the timing loop to compensate for the vibration.
10. The method as recited in claim 9 , further comprising:
filtering the vibration signal to generate a compensated vibration signal; and
generating the adaptation control signal based on the compensated vibration signal and the error signal.
11. The method as recited in claim 10 , wherein filtering the vibration signal to generate the compensated vibration signal comprises filtering the vibration signal with a filter representing a torque rejection curve of the timing loop.
12. The method as recited in claim 10 , further comprising adapting the adaptive filter according to:
W k+1 =W k +μ X k e k
where:
W k represents coefficients of the adaptive filter;
μ represents a learning coefficient;
X k represents the compensated vibration signal; and
e k represents the error signal.
13. The method as recited in claim 9 , further comprising filtering a sensor signal generated by a vibration sensor to generate the vibration signal, wherein the filtering compensates for a transfer function of the vibration sensor.
14. A method of operating a data storage device, the method comprising:
measuring a first wedge-to-wedge time representing a time between consecutive servo sectors passing under a first read element as a disk rotates;
measuring a second wedge-to-wedge time representing a time between consecutive servo sectors passing under a second read element as the disk rotates; and
generating a nominal wedge-to-wedge time based on the first wedge-to-wedge time and the second wedge-to-wedge time.
15. The method as recited in claim 14 , further comprising generating the nominal wedge-to-wedge time based on an average of the first wedge-to-wedge time and the second wedge-to-wedge time.
16. The method as recited in claim 14 , further comprising generating a disk-locked clock substantially synchronized to a rotation frequency of the disk based on the nominal wedge-to-wedge time.