Data storage device compensating for hysteretic response of microactuator
View Patent ↗A data storage device is disclosed comprising a microactuator configured to actuate a head over a disk. A control signal applied to the microactuator is generated based on an input sequence u(k). A Preisach bit map b j is updated based on the input sequence u(k), wherein the Preisach bit map b j corresponds to a Preisach plane modeling a hysteretic response of the microactuator. A current compensation value y i is generated based on an update value generated based on: ∑ j h ( j ) b ^ j where h j represents a slice of the Preisach plane and {circumflex over (b)} j is an update bit map based on at least part of the Preisach bit map b j . The current input u i and the current compensation value y i are combined to generate the control signal applied to the microactuator.
1. A data storage device comprising:
a disk;
a head;
a microactuator configured to actuate the head over the disk; and
control circuitry configured to:
generate a control signal applied to the microactuator based on an input sequence u(k);
update a Preisach bit map b j based on the input sequence u(k), wherein the Preisach bit map b j corresponds to a Preisach plane modeling a hysteretic response of the microactuator;
generate a current compensation value y i based on an update value generated based on:
∑
j
h
(
j
)
b
^
j
where h j represents a slice of the Preisach plane and {circumflex over (b)} j is an update bit map based on at least part of the Preisach bit map b j ; and
combine a current input u i and the current compensation value y i to generate the control signal applied to the microactuator.
2. The data storage device as recited in claim 1 , wherein the compensation value compensates for the hysteretic response of the microactuator.
3. The data storage device as recited in claim 1 , wherein when a previous input u i-1 is less than the current input u i , the control circuitry is further configured to generate the current compensation value y i by adding the update value to a previous compensation value y i-1 .
4. The data storage device as recited in claim 1 , wherein when a previous input u i-1 is less than the current input u i , the control circuitry is further configured to generate the update bit map {circumflex over (b)} j based on u i -u i-1 bits of the Preisach bit map b j .
5. The data storage device as recited in claim 4 , wherein the u i -u i-1 bits of the Preisach bit map b j comprise high order bits of the Preisach bit map b j having a target value.
6. The data storage device as recited in claim 5 , wherein the u i -u i-1 bits of the Preisach bit map b j comprise the high order bits of the Preisach bit map b j having a target value of 1.
7. The data storage device as recited in claim 6 , wherein after generating the update value the control circuitry is further configured to clear m high order bits of the Preisach bit map b j where m represents the u i -u i-1 high order bits of the Preisach bit map b j having a target value of 1 plus the intervening 0 bits.
8. The data storage device as recited in claim 1 , wherein when a previous input u i-1 is greater than the current input u i , the control circuitry is further configured to generate the current compensation value y i by subtracting the update value from a previous compensation value y i-1 .
9. The data storage device as recited in claim 1 , wherein when a previous input u i-1 is greater than the current input u i , the control circuitry is further configured to generate the update bit map {circumflex over (b)} j by inverting at least part of the Preisach bit map b j .
10. A data storage device comprising:
a head;
a disk;
a microactuator configured to actuate the head over the disk; and
control circuitry configured to:
inject a sinusoid into a control signal applied to the microactuator and measure a sinusoidal response of the microactuator; and
generate a Preisach plane based on at least two cycles of the measured sinusoidal response, wherein the Preisach plane models a hysteretic response of the microactuator.
11. The data storage device as recited in claim 10 , wherein the control circuitry is further configured to:
generate a control signal applied to the microactuator based on an input sequence u(k);
generate compensation values y(k) based on the input sequence u(k) and the Preisach plane; and
combine a current input u i and a current compensation value y i to generate the control signal applied to the microactuator.
12. The data storage device as recited in claim 11 , wherein the compensation values y(k) compensate for the hysteretic response of the microactuator.
13. The data storage device as recited in claim 10 , wherein the control circuitry is further configured to:
adjust an offset of the sinusoid injected into the control signal applied to the microactuator; and
after adjusting the offset, generate part of the Preisach plane based on at least two cycles of the measured sinusoidal response.
14. A method of operating a data storage device, the method comprising:
generating a control signal applied to a microactuator based on an input sequence u(k), wherein the microactuator is configured to actuate a head over a disk;
updating a Preisach bit map b j based on the input sequence u(k), wherein the Preisach bit map b j corresponds to a Preisach plane modeling a hysteretic response of the microactuator;
generating a current compensation value y i based on an update value generated based on:
∑
j
h
(
j
)
b
^
j
where h j represents a slice of the Preisach plane and {circumflex over (b)} j is an update bit map based on at least part of the Preisach bit map b j ; and
combining a current input u i and the current compensation value y i to generate the control signal applied to the microactuator.
15. The method as recited in claim 14 , wherein the compensation value compensates for the hysteretic response of the microactuator.
16. The method as recited in claim 14 , wherein when a previous input u i-1 is less than the current input u i , the method further comprises generating the current compensation value y i by adding the update value to a previous compensation value y i-1 .
17. The method as recited in claim 14 , wherein when a previous input u i-1 is less than the current input u i , the method further comprises generating the update bit map {circumflex over (b)} j based on u i -u i-1 bits of the Preisach bit map b j .
18. The method as recited in claim 17 , wherein the u i -u i-1 bits of the Preisach bit map b j comprise high order bits of the Preisach bit map b j having a target value.
19. The method as recited in claim 18 , wherein the u i -u i-1 bits of the Preisach bit map b 1 comprise the high order bits of the Preisach bit map b 1 having a target value of 1.
20. The method as recited in claim 19 , wherein after generating the update value the method further comprises clearing m high order bits of the Preisach bit map b j where m represents the u i -u i-1 high order bits of the Preisach bit map b j having a target value of 1 plus the intervening 0 bits.
21. The method as recited in claim 14 , wherein when a previous input u i-1 is greater than the current input u i , the method further comprises generating the current compensation value y i by subtracting the update value from a previous compensation value y i-1 .
22. The method as recited in claim 14 , wherein when a previous input u i-1 is greater than the current input u i , the method further comprises generating the update bit map {circumflex over (b)} j by inverting at least part of the Preisach bit map b j .
23. A method of operating a data storage device, the method comprising:
actuating a head over a disk using a microactuator;
injecting a sinusoid into a control signal applied to the microactuator and measure a sinusoidal response of the microactuator; and
generating a Preisach plane based on at least two cycles the measured sinusoidal response, wherein the Preisach plane models a hysteretic response of the microactuator.
24. The method as recited in claim 23 , further comprising:
generating a control signal applied to the microactuator based on an input sequence u(k);
generating compensation values y(k) based on the input sequence u(k) and the Preisach plane; and
combining a current input u i and a current compensation value y i to generate the control signal applied to the microactuator.
25. The method as recited in claim 24 , wherein the compensation values y(k) compensate for the hysteretic response of the microactuator.
26. The method as recited in claim 23 , further comprising:
adjusting an offset of the sinusoid injected into the control signal applied to the microactuator; and
after adjusting the offset, generating part of the Preisach plane based on at least two cycles the measured sinusoidal response.