Fault Estimation for a Class of Nonlinear Systems Based on Intermediate Estimator

This technical note investigates the problem of fault estimation for a class of nonlinear systems with Lipschitzian nonlinearities. In most of the existing fault estimation approaches, the observer matching condition should be satisfied. However, this condition is hard to meet for many systems. To overcome this restriction, a new fault estimation method is proposed, where an intermediate variable is introduced and a specially designed intermediate estimator is proposed to estimate the state and the faults simultaneously by exploiting the properties of fault distribution matrix. It is proved that the states of the error system are uniformly ultimately bounded. Simulation examples verify the effectiveness of the proposed method.