Loop-Shaping Technique for Quadruple-Stage Actuator System in Hard Disk Drive

The future of the cloud service is dependent on the hard disk drive (HDD) capacity growth because demands for the data capacity in the cloud service are rapidly increasing. To solve this issue, we are going to improve the accuracy of a magnetic-head positioning control system so that size of bits for data stored on a disk decreases. In this paper, we have proposed the control system design method for the quadruple-stage actuator system which is a future technology for HDDs. In the proposed method, we employ the Robust Bode (RBode) plot that enables us to design the robust controller with visualized guidelines on the Bode plot of the open-loop characteristics. The validation results with a hybrid simulation by measurement data and mathematical models showed that the proposed control system has good robust performances against the large disturbance for HDDs.