Improvement of H_∞ Controller by Using RBode Plot for Magnetic-Head Positioning System in HDDs

摘要

In this paper, we present a design method of a robust controller for the magnetic-head positioning system in HDDs based on the H_∞ control theory and the Robust Bode (RBode). The RBode plot represents robust performance criteria as allowable and forbidden areas on Bode diagrams. Using the RBode plot, we can easily improve an existing feedback controller with visualized guidelines in order to compensate for disturbances against plant perturbations for a magnetic-head positioning system in a hard disk drive. With the RBode plot method, we need frequency characteristics data of the controlled object and weighting functions. Thus, there is no need to construct transfer function models of controlled objects. Simulation results with the HDD benchmark problem showed that the proposed method enable us to improve the positioning accuracy from the initial H_∞ controller by about 11% without losing stabilities of the control system.