Resonance compensation in dual-stage hard disk drive servo system

Abstract

To enhance the speed and precision, piezoelectric micro-actuator made form lead zirconate titanate (PZT) is used as the secondary actuator in dual-stage hard disk drive (HDD) where a voice coil motor (VCM) is used as the primary actuator. Both VCM actuator and PZT micro-actuator (MA) have the problem of mechanical resonance. Conventional approach is to use a pre-compensator notch filter to suppress the resonance. This method needs an accurate plant model, which is always difficult to obtain. On the other hand, a simple controller in the feedback path is a good solution for suppressing the resonance which does not require a very precise plant model. This paper presents a feedback resonant controller designed in simple way to suppress the resonance of PZT actuator. The design is based on a combined approach where M-norm minimisation and mixed passivity, negative-imaginary, small-gain theorem are used. Simulation results substantiate the effectiveness of the proposed controller.