Variable structure model-reference adaptive control (VS-MRAC) using only input and output measurements. II

For pt.I. see Tech. Rep. RT-01/87, COPPE/UFRJ-EE (1987). A globally asymptotically stable VS-MRAC was proposed in part I for plants with relative degree one. A VS-MRAC for plants of arbitrary relative degree is presented here. The controller requires only input/output measurements and is free of differentiators. The VS-MRAC, for relative degree ⩾2, explicitly requires the equivalent controls associated with certain sliding modes. In the ideal case where these equivalent controls are perfectly measurable, global asymptotic stability of the closed-loop system and exponential convergence of the output error are demonstrated. Stability is preserved in the presence of bounded input disturbances, and asymptotic tracking is shown to be possible even in this case