Adaptive Control of Nonlinear Systems in the presence of Actuator Failures

This paper presents an adaptive state feedback control scheme for a class of nonlinear systems with unknown parameters, variable control gains and in the presence of unknown time varying actuator failures. The designed controller compensates unknown loss of effectiveness failures as well as unknown time varying stuck failures in actuators. The considered actuator failure can cover most failures that may occur in actuators of the practical systems. The proposed adaptive controller is constructed based on a backstepping design method. Appropriate Lyapunov-Krasovskii functionals are introduced to design new adaptive laws to compensate the unknown actuator failures and unknown parameters. The offered method ensures the asymptotic output tracking and the boundedness of all the closed-loop signals. The proposed design approach is employed for a wing rock control of an aircraft in the presence of time varying actuator failures. The simulation results verify the effectiveness and correctness of the proposed adaptive control method.