Low Order H∞ Control Design for a Piezo-Based Milli-Actuator

Abstract

The aim of the paper is to apply new techniques for low order or low complexity linear control design to servo controllers for milli-actuators in hard disk drives. This is accomplished in a systematic way by using a H∞-norm based mixed sensitivity design in which the order of the controller is constrained to a desired value. The mixed sensitivity approach allows for an intuitive tradeoff between disturbance rejection and servo tracking in the hard disk dual-stage control design. The proposed method is applied to a prototype piezoelectric milli-actuator and for this case study a comparison is made between the full and low order control designs. With the approach outlined in this paper, it is illustrated that a low order controller for a milli-actuator can be designed with a satisfactory servo performance.