Disk drive estimating microactuator gain by injecting a sinusoid into a closed loop servo system

摘要

A disk drive is disclosed comprising a head, a disk surface, and 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. A microactuator compensator processes a position error signal (PES) to generate a first control signal, and a disturbance sinusoid is injected into the first control signal to generate a second control signal, wherein the microactuator is controlled in response to the second control signal. Feed-forward compensation is generated corresponding to the injected disturbance sinusoid, and a third control signal is generated in response to the PES and the feed-forward compensation, wherein the VCM is controlled in response to the third control signal. A gain of the microactuator is estimated in response to the feed-forward compensation.

主权项

1. 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:
generate a position error signal (PES) representing a position of the head over the disk surface;process the PES using a microactuator compensator to generate a first control signal;inject a disturbance sinusoid into the first control signal to generate a second control signal;control the microactuator in response to the second control signal;generate first feed-forward compensation corresponding to the injected disturbance sinusoid;generate a third control signal in response to the PES and the first feed-forward compensation;control the VCM in response to the third control signal; andestimate a gain of the microactuator in response to the first feed-forward compensation; wherein prior to injecting the disturbance sinusoid into the first control signal the control circuitry is further operable to adapt a second feed-forward compensation according to:
A(k+1)=A(k)+μ·PES·cos(nk)B(k+1)=B(k)+μ·PES·sin(nk)where:n represents a frequency of the disturbance sinusoid;μ is a learning coefficient; andA and B are coefficients of a second sinusoid used to generate the second feed-forward compensation; and after injecting the disturbance sinusoid into the first control signal the control circuitry is further operable to adapt the first feed-forward compensation according to:a⁡(j+1)=a⁡(j)+(1m⁢∑i=1m⁢Ai⁡(k)post-inj)-A0⁢⁢pre-injb⁡(j+1)=b⁡(j)+(1m⁢∑i=1m⁢Bi⁡(k)post-inj)-B0⁢⁢pre-inj where:a and b are coefficients of a first sinusoid used to generate the first feed-forward compensation;A0 and B0 are coefficients of the second sinusoid prior to injecting the disturbance sinusoid into the first control signal; andAi and Bi are coefficients of the second sinusoid generated over m samples of the PES after injecting the disturbance sinusoid into the first control signal.