Multirate digital control for high track density magnetic disk drives

A computationally effective fixed-order multirate digital control scheme is presented for disk drive actuator control. The proposed multirate controller outputs control commands at each control update instant, while the multirate control scheme is evenly computed for every measurement sampling period, thereby eliminating the need for very powerful processors for implementation. Application results demonstrate that the proposed multirate control scheme is useful to smooth control inputs so as not to excite the flexible mode dynamics of the actuator arm and suspensions.