Observer-based robust fault diagnosis for a class of uncertain nonlinear systems

Robust fault diagnosis is investigated for a class of uncertain nonlinear flight control systems based on the adaptive observer. A new general fault updating law is presented to relax the assumption conditions of the adaptive observer. In addition, a simplified fault updating law is further presented for the case of constant faults. The asymptotical stability of the adaptive observer and the uniform ultimate boundedness of the fault estimation error vector are proved by Lyapunov theorem. The effectiveness of the proposed scheme is demonstrated through the numerical simulation of a flight control system.