Adaptive robust actuator fault-tolerant control in presence of input saturation

In this article, we solve the problem of unknown actuator fault accommodation for a class of uncertain nonlinear systems, with explicit consideration of input saturation. A review of the existing literature reveals that fault-tolerant controllers are often designed without any regard to actuator saturation, and it is assumed that they will not saturate in spite of faults. In reality, however, considerable amount of control effort needs to be expended for suppressing the transients due to actuator faults, which can easily saturate the working actuators. In the present work, an indirect adaptive robust fault-tolerant controller is proposed which explicitly takes into account the actuator limits. Furthermore, the indirect design ensures that adaptation mechanism is not affected adversely due to actuator saturation. Finally, simulation studies performed on a nonlinear hypersonic aircraft model are presented to demonstrate the effectiveness of the proposed scheme in dealing with actuator faults in presence of input saturation.