Design of Sensitivity Function of Multi-Rate VCM Control System

Abstract

The method for designing the sensitivity function of a multiple-input single-output servo system is proposed. The method does not require weight or a weight function unlike linear quadratic (LQ) or H_∞ design. First, a controller candidate is derived by taking into consideration the specification of robustness of the plant system. Then, the sensitivity function is derived from the gain specification of the sensitivity function. As the design of a multi-rate controller can be shown to be equivalent to the multiple-input single-output system, the method is employed to design the multi-rate VCM position control system. The multi-rate controller is designed such that at frequencies higher than the Nyquist frequency, the desired robustness is achieved.