Patent ID: 8363350

Claim:
A magnetic disk drive comprising: a voice coil motor (VCM) actuator configured to coarsely move a head; a microactuator configured to slightly move the head; and a servo controller configured to control a predetermined seek operation of moving the head to a target track using both the VCM actuator and the microactuator, wherein the servo controller comprises: a microactuator controller configured to control the microactuator based on a positioning error between the target track and a position of the head or a positioning error between a first target trajectory and the position of the head, wherein the first target trajectory corresponds to the microactuator; a microactuator estimator configured to estimate a first displacement of the microactuator using a linear model from a first control input to be provided to the microactuator; a VCM actuator controller configured to control the VCM actuator based on a positioning error between the target track and a position of the VCM actuator or a positioning error between a second target trajectory and the first position of the VCM actuator, wherein the second target trajectory corresponds to the VCM actuator and the first position is estimated from the position of the head and the first displacement; a filter configured to estimate a position of the VCM actuator corresponding to a delay in the displacement of the microactuator caused by hysteresis of the microactuator, from a state of the VCM actuator in the predetermined seek operation, and to estimate a second displacement that is the delayed displacement of the microactuator, from the estimated position; and an adder configured to add the second displacement or a second control input corresponding to the second displacement to an input to the microactuator controller or an input to the microactuator.