Intermediate Observer-based Fault Estimation for Nonlinear System with Input Disturbances

This paper explores the intermediate observer-based fault estimation problem for nonlinear system with actuator faults, sensor faults and input disturbances. First, for sake of handling sensor faults conveniently, the system is transformed into augmented form. Second, the intermediate observer is utilized to simultaneously estimate the states, faults and input disturbances, which overcomes the constraint of observer matching condition. The estimation of input disturbances is introduced to raise the accuracy of fault estimation. Finally, by means of Lyapunov stability theory, the estimation errors are proved to be uniformly ultimately bounded. Simulations are given to validate the effectiveness and advantages of the developed approach.