Disk drive increasing integrator output range to complete seek operation
View Patent ↗A disk drive is disclosed comprising a disk comprising a plurality of data tracks, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk. When an access command is received to access a target data track, a seek operation is initiated to seek the head toward the target data track, wherein the seek operation includes integrating a first state of the servo control system and limiting an output range of the integrating. The output range of the integrating is increased during the seek operation, for example, if an error occurs during the seek operation.
1. A disk drive comprising:
a disk comprising a plurality of data tracks;
a head; and
control circuitry comprising a servo control system operable to actuate the head over the disk, wherein the control circuitry operable to:
receive an access command to access a target data track;
initiate a seek operation to seek the head toward the target data track, wherein the seek operation includes integrating a first state of the servo control system and limiting an output range of the integrating; and
increase the output range of the integrating when a time-limit expires without successfully completing the seek operation.
2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to increase the output range of the integrating during a settle mode of the seek operation.
3. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to enable the integrating during the settle mode.
4. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to set the time-limit relative to a beginning of the settle mode.
5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to set the time-limit relative to a second state of the servo control system.
6. The disk drive as recited in claim 5 , wherein the second state comprises a position error signal representing a difference between a target radial location of the head and a measured radial location of the head.
7. The disk drive as recited in claim 5 , wherein the second state comprises a velocity of the head.
8. The disk drive as recited in claim 1 , wherein the first state comprises a position error signal representing a difference between a target radial location of the head and a measured radial location of the head.
9. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
detect a vibration level of the disk drive; and
delay increasing the output range of the integrating until the vibration level is below a threshold.
10. The disk drive as recited in claim 2 , wherein in response to the time-limit expiring during the settle mode, the control circuitry is further operable to perform a plurality of long seeks each over at least one hundred data tracks without accessing the disk in order to smoothen a bias force and improve a likelihood subsequent seek operations will complete successfully within the time-limit.
11. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of data tracks, a head, and control circuitry including a servo control system operable to actuate the head over the disk, the method comprising:
receiving an access command to access a target data track;
initiating a seek operation to seek the head toward the target data track, wherein the seek operation includes integrating a first state of the servo control system and limiting an output range of the integrating; and
increasing the output range of the integrating when a time-limit expires without successfully completing the seek operation.
12. The method as recited in claim 11 , further comprising increasing the output range of the integrating during a settle mode of the seek operation.
13. The method as recited in claim 12 , further comprising enabling the integrating during the settle mode.
14. The method as recited in claim 12 , further comprising setting the time-limit relative to a beginning of the settle mode.
15. The method as recited in claim 12 , further comprising setting the time-limit relative to a second state of the servo control system.
16. The method as recited in claim 15 , wherein the second state comprises a position error signal representing a difference between a target radial location of the head and a measured radial location of the head.
17. The method as recited in claim 15 , wherein the second state comprises a velocity of the head.
18. The method as recited in claim 12 , wherein the first state comprises a position error signal representing a difference between a target radial location of the head and a measured radial location of the head.
19. The method as recited in claim 12 , further comprising:
detecting a vibration level of the disk drive; and
delaying increasing the output range of the integrating until the vibration level is below a threshold.
20. The method as recited in claim 12 , wherein in response to the time-limit expiring during the settle mode, further comprising performing a plurality of long seeks each over at least one hundred data tracks without accessing the disk in order to smoothen a bias force and improve a likelihood subsequent seek operations will complete successfully within the time-limit.