Uncertainty and performance of adaptive controllers for functionally uncertain output feedback systems

We consider nonlinear systems in an output feedback form which are functionally known up to a L/sup 2/ measure of uncertainty. The control task is to drive the output of the system to some neighbourhood of the origin. A modified L/sup 2/ measure of transient performance (penalising both state and control effort) is given, and the performance of a class of model based adaptive controllers is studied. An upper performance bound is derived.