Magnetic-head positioning control of HDDs with improved <i>H</i>_∞ controller by Robust Controller Bode (RCBode) plot

Abstract

In this paper, we present a robust controller design method for a magnetic-head positioning system in a hard disk drive (HDD) based on the H ∞ control theory and the Robust Controller Bode (RCBode) lot. The RCBode plot represents robust performance criteria as allowable and forbidden areas on Bode diagrams for a controller. Using the RCBode plot, we can improve an existing H ∞ controller with visualized guidelines in order to compensate for disturbances against plant perturbations. We show utilities of the proposed method by applying it to a popular benchmark problem for the HDDs. Simulation results with the HDD benchmark problem showed that the proposed method enables us to improve positioning accuracy of the magnetic-head position by about 15% without losing stability margins from the original H ∞ controller.

Active disturbance rejection control for discrete systems with zero dynamics

“…20 In addition, NMP outputs with unstable zeros are quite common in many practical systems. 21,22 Many researchers have provided approximate model-inversion techniques for systems with NMP outputs. 23,24 These techniques were compared in model inverse control for a hard disk drive.…”

“…(21 − 35K + 15K 2 ), K = k−k i k f −k i , y i = 0, k i =10, y f = 100, and k f = 70. A step input disturbance f I = 5 occurred at iteration 100.…”