Simultaneous actuator and sensor fault estimation for discrete-time Lipschitz nonlinear systems in finite-frequency domain

This paper addresses the problem of actuator and sensor fault reconstruction simultaneously with finite-frequency specifications for discrete-time Lipschitz nonlinear systems. First, an augmented system description is given by extending the sensor fault as an auxiliary state vector. Then, a multiobjective unknown input proportional-integral observer is designed, and the nonlinear error dynamics are transformed into a linear parameter-varying system based on the use of a reformulated lipschitz property. Sufficient conditions for the design of a fault estimator with 2 finite-frequency H-infinity performances are derived in terms of linear matrix inequalities where a slack variable is introduced to reduce the conservativeness of the design. The proposed method can provide less restrictive linear matrix inequality conditions and get a better fault estimation performance than the existing one in the full frequency domain. Simulation results are given to show the effectiveness of the proposed techniques.