Robust model reference adaptive controllers, Part I: Stability analysis

We study the stability given by a modified model reference adaptive controller. Modifications are projections of the adapted parameters into a compact set, normalization of the signals entering the adaptation law by a weighted L2-norm of the I/O signals. The a priori knowledge about the plant is implicit: order of a stabilizing regulator, compact set containing its coefficients. Global boundedness of the signals is established using both the error to signal approach of [10] and the operator theoretic approach of [8]. A conicity condition is involved but its robustness with respect to the graph topology of [20] is proved.