Robust Adaptive Regulation by Output Error Feedback for Uncertain Nonlinear Systems

Abstract Minimum phase uncertain nonlinear systems in output feedback form are considered: they are subject to disturbances and/or uncertainties and are required to track reference signals. Both disturbances and references are generated by an exosystem whose parameters are uncertain. Under the assumption that the regulator problem has a solution, but with no a priori assumption on the required control input (e.g. no ‘immersion’ assumption), a global robust error feedback regulator is designed. If its adaptive internal model can generate the required control input global asymptotic regulation is achieved, otherwise the regulation error tends to a residual set which decreases as the reference input modeling error decreases.