Design of H₂/H_∞ Controllers for Rigid Disk Servo System in Response to Operation Modes

Abstract

A control system design for head positioning in a rigid disk system has been studied in this paper. The use of multiple controllers is proposed to cope with variable operating modes. An H_∞ controller with robust stability in the track following mode of a recording head and an H₂ controller were designed by using a model-matching method for high-speed track seeking. The H₂ controller is adapted each seek distance. Finally, a control system was constructed with both controllers. Closed-loop stability is maintained due to the structure of Yula parameterization⁸⁾ even when the controllers are switched according to the operating mode.