Abstract
In this paper, a reduction problem of H∞ controllers is considered. The problem treated here is that of truncating high order H∞ controllers which are complicated by high order free parameters. This problem sometimes appears when a numerical approach is used for H∞ control problems. The H∞ controller is truncated by approximating a free parameter which is high order solution of the Model Matching Problem using the balanced realization approximation technique. This method preserves internal stability of closed loop systems and the domain in which closed loop poles locate. A sufficient condition for preserving an H∞-norm constraint of the closed loop system in which a high order controller is approximated by low order one is derived. Thus, in this reduction method closed loop properties are taken into account, i. e. the internal stability and the domain in which all closed loop poles locate are preserved.
