| Abstract |
In this paper, novel multirate feedback controllers are proposed for digital control systems, where it is restricted that the speed of the A/D converters are slower than that of the D/A converters. The proposed controllers achieve vibration suppression and disturbance rejection even in the semi-Nyquist frequency region. First, the continuous-time vibration suppression controller is exactly discretized by the multirate sampling control based on the closed-loop characteristics. Second, the multirate repetitive controllers are proposed both by the feedback and feedforward approaches. Moreover, the initial value compensations for ob-server are proposed in order to prevent the overshoot. The proposed controllers are applied to the settling and following modes of hard disk drive, and the advantages of these approaches are demonstrated by simulations. |
