Dual-stage servo control and active vibration compensation in magnetic hard disk drives

In order to sustain the continuing increase in storage density in magnetic hard disk drives (HDD), high bandwidth dual-stage actuator servo systems have been developed to improve the precision of read/write head positioning control. In this dissertation, robust and adaptive controller design methodologies and algorithms are developed for PZT-actuated suspension and MEMS microactuator based dual-stage servo systems. Active vibration control techniques using dual-stage multi-sensing servo systems to compensate for high-frequency structural vibrations are proposed.; A coupled MIMO plant model of a PZT-actuated suspension dual-stage actuator is identified using frequency response modal testing. A structured uncertainty model is established to represent both parametric uncertainty and unmodeled dynamics for robust control design and analysis. Dual-stage controllers are designed using a decoupled single-input single-output (SISO) frequency shaping design technique and multi-variable robust controller design technique mu-synthesis. Experimental results are presented and compared.; An active vibration damping control scheme of using one PZT element as a vibration sensor and the other one as an actuator is proposed to damp the resonance modes of the PZT-actuated suspension dual-stage actuator. Vibration damping controller design using Kalman filter based state feedback control is described. Experimental results are presented demonstrating the effectiveness of the proposed control scheme in suppressing airflow excited structural vibrations.; For the controller design of a MEMS microactuator based dual-stage servo system, a decoupled design structure with microactuator inner-loop damping and a design methodology by discrete-time pole placement are proposed. A self-tuning control scheme is developed to compensate for the variations in the microactuator's resonance mode. An adaptive feedforward control technique is also developed for active vibration compensation using MEMS microactuator dual-stage servo systems. Simulation results are presented to verify the proposed control schemes.