OPTIMAL MULTIRATE CONTROL DESIGN FOR HARD-DISK DRIVE SERVO SYSTEMS

This paper presents a multirate digital controller design for HDD serv o systems via direct parameter optimization approach. In order to find a satisfactory multirate controller with good transient and steady st ate performance, a linear quadratic performance index with stability c onstraints is introduced. The controller parameters are selected based on the HDD servo system transient response data instead of a detailed plant model. The proposed method can improve the performance of LQG m ultirate servo designs without knowing exact plant parameters or noise model. The effect of controller order on system performance is also s tudied. For a 4th order system studied, it is found that a 4th order c ontroller is sufficient to achieve the optimal performance.