Tracking Control of Nonminimal Phase System Without using Preview Information of the Desired Output

By using the preview information of the desired trajectory, the zero phase error tracking controller (ZPETC) is able to make the frequency response of non-minimal phase systems exhibit zero phase error for all frequencies and small gain errors at relatively low frequency range. A novel digital controller is proposed in this paper for the case that the preview information of the desired output was not available. In order to reduce the phase error, a high order modified plant model is used, which is composed of the closed loop transfer function and the Pade approximation of the delay term e^-taus . Determination of the time constant tau is also discussed. Experiment results developed for a DC motor servo system show the effectiveness of the proposed approach.