Abstract: A new formulation of fault diagnosis and fault-tolerant control algorithm is presented for a class of nonlinear dynamic systems with a linear output structure.A Lyapunov-based adaptive observer is proposed to produce a residual signal.The fault estimate guarantees negativity of the first order derivative of the Lyapunov function using Lyapunov analysis.Two adaptive observers are designed for fault-tolerant control, and the system output after occurrence of a fault tracks the output of the original system through a nonlinear controller reconfiguration.Simulation results show the effectiveness of the proposed algorithm.

Key words: fault-tolerant control, nonlinear systems, Lyapunov function, adaptive observers, fault diagnosis