Design of H∞-optimal feedback systems

In this paper we provide a treatment of the H^∞-mixed sensitivity optimization approach to feedback system design which is viewed as a generalization of the H^∞-sensitivity minimization problem introduced by Zames [1979, 1981] The optimization problem is shown to reduce to a nonstandard interpolation problem which can nonetheless be solved for a prespecified performance level. The optimal performance is characterized as the norm of a Hankel plus Toeplitz operator and some computational approaches for implementing the design method are suggested. It is hoped that the design method proposed here will contribute to extending the scope of H^∞-optimization methods.