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Track-seeking controller design for dual-stage actuator in magnetic disk drives

A new decoupled track-seeking controller design is described for dual-stage servo systems of magnetic disk drives. The controller is applied to the dual-stage system with a push-pull piezoelectric (PZT) micro-actuator and enables highspeed one-track seeking and short-span track seeking. The one-track seeking controller was designed in three steps: 1) a voice coil motor (VCM) feedforward controller was designed to prevent overshoot in response of VCM actuator; 2) a feedforward loop was designed from the VCM reference signal to the PZT actuator in order to decouple the dual-stage actuator system; and 3) a feedforward controller was designed for the PZT actuator such that an output position error signal (PES) only follows a PES reference signal. For the short-span seeking controller, the PZT actuator's stroke limit was considered. Simulations and experiments show that the proposed dual-stage track seeking controller performs better than the conventional single VCM servo.