Patent ID: 8630059

Claim:
A disk drive, comprising: a disk; an actuator arm comprising a head configured to read and write data to the disk; a servo controller configured to control the actuator arm, the servo controller using a position error signal to generate a controller output signal; a plant configured to mechanically model the disk drive and to receive a control command to which a disturbance is added and to generate a plant output; a disturbance observer, the disturbance observer using the control command and the plant output to generate a delayed and estimated version of the disturbance, the disturbance observer comprising a Q filter having a selected center frequency ω 0 , and a perfect phase cancellation filter, the perfect phase cancellation filter being configured to receive the delayed and estimated version of the disturbance and to reject selected disturbances and align a desired attenuation frequency with the selected center frequency of the Q filter, an output of the perfect phase cancellation filter being subtracted from the controller output signal to generate the control command.