Adaptive robust output feedback controllers guaranteeing uniform ultimate boundedness for uncertain nonlinear systems

The problem of robust output feedback stabilization for a class of nonlinear systems with partially known uncertainties is considered. A class of continuous adaptive robust output feedback controllers that can guarantee uniform ultimate boundedness of the resulting closed-loop systems in the presence of uncertainties is proposed. In contrast with some results presented in the control literature, the adaptive law for updating the estimate values of the unknown parameters is continuous, and the existence of the solutions to the resulting closed-loop systems in the usual sense can be guaranteed. Moreover, due to the continuity of the output feedback controller and adaptive law, the proposed adaptive robust output feedback controller is easily implemented in practical robust control, and no chattering appears in practical systems. Finally, an illustrative example is given to demonstrate the utilization of the results.