Model-following controller design based on a stabilized digital inverse system

This paper explains and demonstrates a model-following controller design based on the stabilized digital inverse system. Conventional digital inverse systems are constructed behind a plant to estimate unknown disturbances. Herein, the inverse system is designed in front of the plant. The model-following controller is then constructed on the basis of this structure. However, when the relative degree of the transfer function for the continuous-time plant is greater than the 3rd order, discrete-time systems often become a non-minimum phase. Furthermore, when a short sampling period is chosen, the inverse system cannot be constructed, because unstable zeros appear. To solve these problems, the auxiliary observation inter-sample output is adopted from the model. In addition, a parallel feedforward compensator is added in parallel with the plant. We confirmed the effectiveness of the proposed method by performing simulations for several plants.