Model reference adaptive control for a class of nonlinear systems with unknown degrees and uncertain relative degrees

This paper presents a novel approach to the design of model reference adaptive control for a class of nonlinear systems with unknown degrees and uncertain relative degrees. Contrary to the conventional model reference adaptive control where the degrees and relative degrees of controlled systems are assumed to be known, the degrees in the present paper are completely unknown, and the relative degrees are partly unknown; that is, the relative degrees are known to be r, r+1, or r+2 with known r∈N. It is shown that the tracking errors converge to arbitrarily small residual regions under such uncertainties of processes