A dual-stage control algorithm for magnetic disk drives based on coarse motion prediction

A control algorithm is presented for both reliable and efficient realization of hard disk drives with a dual-stage actuator. It enables the full capability of the dual-stage actuator, while preserving the well-established structure of conventional single-arm actuator control algorithms. Basically, the present methodology is a combination of the existing single-arm servo design and an add-on tracking controller design for the microactuator subsystem, with the desired trajectory being the residual position error due to the coarse actuator. A key feature of the tracking controller is that it utilizes the preview information of its desired trajectory, which can be predicted fairly accurately based on the relatively slow coarse actuator dynamics. The best practical advantage is that the present method can achieve not only the high-performance track-following but also the overshoot-free track-seeking without significantly altering the existing single-arm servo system. The performance of the proposed method is demonstrated through some simulation and experiment