Discrete-time controller design to attenuate effects of external disturbances

This paper presents a discrete time controller to attenuate influence of external disturbances. The proposed controller elevates tracking performance by suppressing a peak of a plant input sensitivity function. The controller is computed from an inverse model of a conventional plant input sensitivity function. For a stable and casual inverse model, we introduce all-pass filters and unit delays. In addition, high pass filters are utilized to avoid amplification of high frequency disturbance, which is a different approach from traditional design methods. Experimental verifications demonstrate the effectiveness of this design method and it is confirmed that the controller suppresses the sensitivity peak and enhances tracking performance obviously.