Abstract
This paper considers a design method of a digital controller which realizes approximately an arbitrarily specified closed-loop response. A weighted sum of square errors is introduced as a measure of the approximation. Minimizing the weighted sum, a linear equation is obtained for unknown parameters of the reduced-order controller. In this method, the order of the controller can be arbitrarily specified. A new criterion is proposed to determine the order of the controller. The criterion is based upon a tradeoff between goodness of the approximation and degradation of that for changes in plant parameters. Examples are given to illustrate the effectiveness of this design method.
