Robust adaptive fault tolerant control for a class of linearly parameterized uncertain nonlinear systems: An integrated method

In the fault tolerant control systems, there often exist coupled uncertainties between the fault estimate subsystems and the state control subsystems. The coupled uncertainties are often ignored in the conventional separated design approaches, and the control performance degradation or even in-stability may be induced. To address this problem, an integrated fault tolerant control method is developed in this paper. The key point of this paper is to design the fault estimator and the fault tolerant controller from the perspective of the composite system comprised of the two subsystems. A combined weight update law, associating with both the state control dynamic equation and the observation error subsystem, is obtained. A new sufficient condition for the closed-loop stability is derived in terms of linear matrix inequalities. Based on a combined Lyapunov function, the composite closed-loop system is proven to be globally stable. Meanwhile, with the parameterized nonlinear functions and the unknown actuator/sensor faults, the coupled uncertainties are analyzed. Several illustrative examples are employed and the simulation results demonstrate the effectiveness of the proposed method.