Patent ID: 8611040

Claim:
A disk drive comprising: a head; a disk surface; a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop comprising a VCM and a microactuator servo loop comprising a microactuator operable to actuate the head over the disk surface; and control circuitry operable to: disable a microactuator compensator in the microactuator servo loop; and after disabling the microactuator compensator: inject a sinusoid into a control signal applied to the microactuator and measure coefficients of a corresponding sinusoidal response in a DSA error signal of the DSA servo loop; inject the sinusoid into a model of the microactuator to generate a compensation signal; generate a VCM error signal of the VCM servo loop based on the DSA error signal and the compensation signal; generate a VCM control signal based on the VCM error signal; and adjust a gain of the microactuator based on the VCM error signal and the coefficients of the sinusoidal response in the DSA error signal.