Data storage device re-qualifying state estimator while decelerating head
View Patent ↗A data storage device is disclosed comprising a disk comprising a plurality of tracks defined by servo sectors, a head, and a servo controller configured to servo the head over the disk based on an estimated state generated by a state estimator. The servo controller is configured to execute a seek operation to seek the head over the disk and recover from a servo fault during the seek operation by generating an initial state estimate of the head at the beginning of the servo fault, and decelerating the head open-loop using a model-based deceleration control in response to the initial state estimate. While decelerating the head, the state estimator is re-qualified before the head reaches zero velocity, and after re-qualifying the state estimator and before the head reaches zero velocity, a seek operation is executed to seek the head to a target track closed-loop using the state estimator.
1. A data storage device comprising:
a disk comprising a plurality of tracks defined by servo sectors;
a head; and
a servo controller configured to servo the head over the disk based on an estimated state generated by a state estimator, wherein the servo controller is configured to execute a seek operation to seek the head over the disk and recover from a servo fault during the seek operation by at least:
generating an initial state estimate of the head at the beginning of the servo fault;
decelerating the head open-loop using a model-based deceleration control in response to the initial state estimate;
while decelerating the head, re-qualifying the state estimator before the head reaches zero velocity; and
after re-qualifying the state estimator and before the head reaches zero velocity, seeking the head to a target track closed-loop using the state estimator.
2. The data storage device as recited in claim 1 , wherein the model-based deceleration control comprises a model-based just-in-time (JIT) control.
3. The data storage device as recited in claim 1 , wherein the servo controller is further configured to recover from the servo fault by verifying the re-qualification of the state estimator.
4. The data storage device as recited in claim 3 , wherein when the state estimator passes the verification, the servo controller is further configured to recover from the servo fault by seeking the head to the target track closed-loop based on the state estimator and the servo sectors.
5. The data storage device as recited in claim 3 , wherein when the state estimator fails the verification, the servo controller is further configured to recover from the servo fault by:
using the model-based deceleration control to generate a first interim velocity estimate of the head; and
when the first interim velocity estimate of the head exceeds a threshold, continuing the decelerating of the head open-loop using the model-based deceleration control.
6. The data storage device as recited in claim 5 , wherein when the first interim velocity estimate of the head is less than the threshold, the servo controller is further configured to recover from the servo fault by re-initializing the servo controller.
7. The data storage device as recited in claim 6 , further comprising a voice coil motor (VCM) configured to actuate the head over the disk in response to a control signal generated by the servo controller, wherein the servo controller is further configured to recover from the servo fault by:
generating a second interim velocity estimate of the head based on a back electromotive force (BEMF) voltage generated by the VCM; and
re-initializing the servo controller based on the second interim velocity estimate.
8. A method of operating a data storage device, the method comprising:
servoing a head over a disk based on an estimated state generated by a state estimator, and
recovering from a servo fault during a seek operation by at least:
generating an initial state estimate of the head at the beginning of the servo fault;
decelerating the head open-loop using a model-based deceleration control in response to the initial state estimate;
while decelerating the head, re-qualifying the state estimator before the head reaches zero velocity; and
after re-qualifying the state estimator and before the head reaches zero velocity, seeking the head to a target track on the disk closed-loop using the state estimator.
9. The method as recited in claim 8 , wherein the model-based deceleration control comprises a model-based just-in-time (JIT) control.
10. The method as recited in claim 8 , further comprising recovering from the servo fault by verifying the re-qualification of the state estimator.
11. The method as recited in claim 10 , wherein when the state estimator passes the verification, the method further comprises recovering from the servo fault by seeking the head to the target track closed-loop based on the state estimator and the servo sectors.
12. The method as recited in claim 10 , wherein when the state estimator fails the verification, the method further comprises recovering from the servo fault by:
using the model-based deceleration control to generate a first interim velocity estimate of the head; and
when the first interim velocity estimate of the head exceeds a threshold, continuing the decelerating of the head open-loop using the model-based deceleration control.
13. The method as recited in claim 12 , wherein when the first interim velocity estimate of the head is less than the threshold, the method further comprises recovering from the servo fault by re-initializing a servo controller.
14. The method as recited in claim 13 , further comprising recovering from the servo fault by:
generating a second interim velocity estimate of the head based on a back electromotive force (BEMF) voltage generated by a voice coil motor; and
re-initializing a servo controller based on the second interim velocity estimate.