Adaptive robust control of SISO nonlinear systems in a semi-strict feedback form

This paper considers the adaptive robust control of a class SISO nonlinear systems in a semi-strict feedback form. The systems may possess both parametric uncertainties and unknown nonlinear functions that may represent modeling errors and external disturbances. With prior knowledge of the bounds of the parametric uncertainties and the bounding functions of the unknown nonlinear functions, a systematic way to combine the backstepping adaptive control with deterministic robust control is developed. The method preserves the advantages of the two methods, namely asymptotic stability of adaptive control in the presence of parametric uncertainties, and guaranteed transient performance with prescribed precision of deterministic robust control for both parametric uncertainties and unknown nonlinear functions. The resulting controller is more flexible and Versatile than either adaptive control or robust control alone. Simulation results verify the advantages of the suggested method. (C) 1997 Elsevier Science Ltd.