New design of multirate state feedback control for HDD

This paper discusses a new design method for state feedback multirate control with current estimator. A computationally effective multirate digital control scheme, in which the control outputs are calculated based only on the state estimates at sampling instants, is presented. It is shown that the states of the redesigned state feedback multirate control system match the states of conventional state feedback multirate control system at every sampling instant. The redesigned method is applied to a HDD servo control systems. The experimental results show that the performance of the redesigned multirate system is similar to that of the conventional multirate design in terms of open loop bandwidth, phase margin and gain margin.