A simple controller for unknown nonlinear systems

This work addresses the dynamic feedback control problem of unknown nonlinear systems that can be affected by unknown state and control dependent perturbations (that can appear, for instance, as result of unexpected changes of system dynamics due to faults). To include the perturbations, unknown general nonlinear systems are considered. By using bounded linearly parameterized approximators to parameterized the unknown nonlinearities, a controller that guarantees uniform ultimate boundedness of all signals in closed loop is designed. The proposed controller forces the tracking error to converge to a ball whose radius can be a priori arbitrary specified by the control designer. Simulation results shows the effectiveness and feasibility of the proposed scheme.