Robust diagnosis of incipient faults based on sliding mode observer

A robust incipient faults diagnosis proposal for a class of nonlinear system with unknown input disturbances is presented in this paper. First, the uncertain nonlinear system is transformed into two subsystems and one of them is free from disturbances. Then for the subsystem free from disturbances, an adaptive observer is constructed to reconstruct incipient faults and a sliding mode observer is constructed for another subsystem in order to eliminate the effect of unknown disturbances. Finally, the effectiveness of the proposed approach is illustrated via an aircraft example.