Settling Control with Reference Redesign for Dual Actuator Hard Disk Drive Systems

Abstract

This paper considers settling control for a dual actuator system for hard disk drives consisting of a coarse actuator(voice coil motor) and a fine actuator(peizoelectric transducer, PZT). The design method proposed in this paper is called the dual actuator reference trajectory re-design(RTRD). In the RTRD, the design is divided into three steps. In the first step, the coarse actuator loop is designed to be stable via active damping and achieve the basic performance. In the second step, the fine actuator path is designed by loop shaping for superior performance of the overall system. Finally the reference signals are generated for both VCM and PZT actuators. In the dual rate RTRD : the coarse actuator works at slow sampling frequency and the fine actuator works at fast sampling frequency. The “soft switching” technique is applied for gradually introducing the fine actuator(PZT actuator), which may shorten the settling time and achieve smoother settling response. The effectiveness of the proposed approach is evaluated by simulations.