Insensitive H∞ tracking control for discrete-time systems with coefficient sensitivity constraints

The problem of designing insensitive H_∞ output tracking controller for discrete-time systems is studied in a unified framework by using the delta operator approach. Coefficient sensitivity functions of transfer functions with respect to controller coefficient variations are defined, and the H_∞ norms of the sensitivity functions are used to measure the sensitivity of the transfer functions with respect to controller coefficient variations. Based on a novel bounded real lemma, a sufficient condition for the existence of the insensitive controller is obtained in terms of linear matrix inequality (LMI) technique. Finally, a numerical example based on linearize model of F-18 aircraft is given to illustrate the effectiveness of the proposed method.