The use of multirate notch filters in embedded-servo disk drives

This paper explores the merits of using a discrete time multirate notch filter,in series with an FIR filter, for controlling a flexible mechanical system whose resonance is beyond one-half the servo sample rate (in other words, an aliased resonance). Through numerical optimization of the closed loop transient response, the performance of this architecture is compared to that of a single-rate notch with an FIR filter, and that of an FIR filter alone. For the specific example chosen here, it is seen that the multirate notch gives results that are far superior to either of the alternatives