On improving control-loop robustness of model-matching controllers (Q1081567)

The paper characterizes the class of all stabilizing controllers for a two-degree-of-freedom control system which achieve a prescribed achievable transfer function. The characterization is in terms of an arbitrary proper stable transfer function. With this characterization, robust model matching is formulated as a standard \(H^{\infty}\)- optimization problem. The results are potentially the basis for robust controller designs to meet transfer function performance/robustness objectives, or to improve robustness of standard designs, such as LQG designs which focus primarily on performance for the nominal plant.