Variable structure model-reference adaptive control (VS-MRAC) using only input and output measurements: the general case

A globally asymptotically stable VS-MRAC for the general case of plants with arbitrary relative degree is presented. It is shown that the VS approach leads to general adaptive controllers with outstanding performance. The controllers use only I/O measurements and are free of differentiators. The results indicate that several of the usual drawbacks of conventional MRACs (e.g. unsatisfactory transient behavior, lack of robustness, difficulties in designing controllers for time-varying or nonlinear plants) can be circumvented