Robust UIO-based fault estimation for sampled-data systems: An LMI approach

This paper presents a robust unknown input observer-based approach to deal with fault diagnosis for sampled-data control system with unknown input. Firstly a discrete-time model was considered to approximate its continuous-time dynamics. Secondly by considering the actuator or sensor fault as an auxiliary state vector, an augmented system is constructed. Thirdly we derive the structure of the proposed robust unknown input observer. A sufficient existence condition in terms of the linear matrix inequalities (LMIs) technique is given and proved. Finally, the proposed method is applied to a sampled-data flight control system. Simulation results demonstrate the designed method can estimate both actuator fault and sensor fault.