HEAD POSITIONING DEVICE, HEAD POSITIONING CONTROL METHOD, HEAD POSITIONING CONTROL PROGRAM, RECORDING MEDIUM WITH HEAD POSITIONING CONTROL PROGRAM RECORDED THEREON, AND DISK UNIT USING THESE

摘要

PROBLEM TO BE SOLVED: To provide a head positioning control means for a disk unit using a double actuator by, which positioning can be performed at high speed in a long-distance seek operation, and accurately and stably in a short-distance seek operation or a following operation. SOLUTION: The head positioning device is provided with a micromotion control part 162 which controls head positioning by controlling the displacement quantity of a micromotion actuator 52 on the basis of a position error signal, and a coarse motion control part 161 which controls the head positioning on the basis of a relative displacement signal corresponding to the displacement quantity of the micromotion actuator 52. The coarse motion control part 161 has a nonlinear transforming unit 18 having nonlinear characteristics that the relative displacement signal is amplified by a larger gain than that obtained when an amplitude is small, when the amplitude of the relative displacement signal is large, and performs the head positioning by using a coarse motion actuator 5 on the basis of a transformed output signal.