Adaptive sliding mode control of a disk drive actuator

This paper presents the design of a time optimal variable structure controller for seeking and tracking the read/write heads of a computer hard disk. The controller is robust to both parameter variations and unmodeled dynamics. It also introduces a sufficiently high bandwidth to enable accurate track following in the presence of runout. Control chatter during seeking is reduced through the introduction of a boundary layer around the switching surface. The controller performance is evaluated against a conventional proximate time optimal servo (PTOS) control structure. Time and frequency domain simulations provide proof of the superior robustness and runout performance of the variable structure controller