Robust and perfect tracking control design of a hard disk drive with a dual-stage actuator

This paper deals with the problem of a servo system design for a typical dual-stage actuator hard disk drive using a so-called discrete-time robust and perfect tracking (RPT) approach. We will first present the system identification methods to model the physical systems of the primary actuator and the micro-actuator from measured frequency response data. Then the two individual servo loops for the primary actuator and the micro-actuator are designed. To achieve a high bandwidth and fast response time, the micro-actuator is designed to do most of the tracking work. Thus we formulate its design work into a robust and perfect tracking problem, in which a measurement feedback controller can be obtained. For the primary actuator servo loop, some conventional method is applied to make the servo loop stable and let it have slow response to the reference. The simulation results shows that the compensated dual-stage actuator servo system can have a very fast time response and no overshoot.