Data storage device employing sliding mode control of spindle motor
View Patent ↗A data storage device is disclosed comprising a head actuated over a disk, and a spindle motor configured to rotate the disk. A speed of the spindle motor is sampled, and an error signal is generated based on a difference between the sampled speed and a target speed. A sliding mode control signal for controlling a speed of the spindle motor is generated based on a first non-zero gain when the error signal is greater than zero and less than a first positive threshold, and a second non-zero gain when the error signal is greater than the first positive threshold.
1. A data storage device comprising:
a head actuated over a disk;
a spindle motor configured to rotate the disk; and
control circuitry configured to:
sample a speed of the spindle motor;
generate an error signal based on a difference between the sampled speed and a target speed; and
generate a sliding mode control signal for controlling the speed of the spindle motor based on:
a first non-zero gain when the error signal is greater than zero and less than a first positive threshold; and
a second non-zero gain when the error signal is greater than the first positive threshold,
wherein a first slope of the sliding mode control signal defined by the first non-zero gain is contiguous with a second slope of the sliding mode control signal defined by the second non-zero gain.
2. The data storage device as recited in claim 1 , wherein the first non-zero gain is less than the second non-zero gain.
3. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to saturate the sliding mode control signal when the error signal is greater than a second positive threshold higher than the first positive threshold.
4. A method of operating a disk drive, the method comprising:
sampling a speed of a spindle motor;
generating an error signal based on a difference between the sampled speed and a target speed; and
generating a sliding mode control signal for controlling the speed of the spindle motor based on:
a first non-zero gain when the error signal is greater than zero and less than a first positive threshold; and
a second non-zero gain when the error signal is greater than the first positive threshold,
wherein a first slope of the sliding mode control signal defined by the first non-zero gain is contiguous with a second slope of the sliding mode control signal defined by the second non-zero gain.
5. The method as recited in claim 4 , wherein the first non-zero gain is less than the second non-zero gain.
6. The method as recited in claim 4 , further comprising saturating the sliding mode control signal when the error signal is greater than a second positive threshold higher than the first positive threshold.