Disturbance rejection on critical resonant mode in hard disk drives

In this paper, we propose a control method which combines notch filter and peak filter to provide disturbance rejection at the frequency of critical resonant mode. The settling rate is also improved by time-varying the parameters of the peak filter. Our simulation and experimental results show that the out-of-phase resonant mode is reshaped to an in-phase mode, and the disturbance at the frequency of critical resonant mode is attenuated by 70% with an improved settling rate. The proposed control method is shown to be robust against ± 10% perturbation of natural frequencies.