Robust sliding mode observer for fault estimation of uncertain system

This paper describes a method of actuator fault estimation for linear uncertain systems. In this work, the upper bound of the unknown input is not required. To remove this requirement a modified sliding mode observer is presented. The novelty in this method lies in the structure of the mechanism introduced to calculate the sliding mode observer gain responsible to counteract uncertainty and actuator fault. In order to guarantee robustness to uncertainty, the developed observer use the H∞ principle. Then, based on Lyapunov method, asymptotic stability conditions are given to design the observer parameters. Also, the equivalent output error injection signal is used to estimate the fault. Finally, the validity of this approach is illustrated by a VTOL aircraft model.