Controller optimization for minimum position error signals of hard disk drives

In order to reduce the position error signal (PES) and track misregistration (TMR) of disk drives, it is generally believed that the bandwidth of a disk drive servo system has to be increased. However, increase of the bandwidth is limited by feasible sampling frequency and mechanical resonances of a head disk assembly (HDA). Hence for a given servomechanical system, optimization of a servo controller is crucial to get the best TMR performance. In this paper, optimization of a servo controller that yields minimum PES is presented. The equivalent position-mode disturbance is estimated by the error transfer function inversion method and injected into the servo system to generate the PES. Minimization of the PES is confirmed by simulation and experiments.

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