Modified Pq Method for Robustness to Microactuator Saturation and Failure

Two concerns for the deployment of two stage actuators in disk drives are microactuator saturation and data recovery in the event of outright microactuator failure. Compensators designed for good performance with two intact actuators may be unstable when the microactuator saturates or stops working entirely. This paper develops a modification of the PQ Method to guarantee stable operation in the event of microactuator failure. Application of the Circle Criterion shows that the resulting design can be robust to actuator saturation. A controller design for a simplified but realistic model of a disk drive two stage actuator system illustrates the approach. Copyright © 2005 IFAC