Performance enhancement of multi-rate controller for hard disk drives

This paper describes a new multi-rate controller for hard disk drives, whic h has a modified state estimator to correct the estimated states not only a t measurement instances of the position error signal but also at every cont rol instance when updating the control input. This modification makes the c ontrol input smoother compared to the conventional multi-rate scheme. This estimator is obtained as a stochastic optimal estimator for a linear dynami c system with a 'random walk' input noise process. The effectiveness of the modified scheme is demonstrated by experiments.