Robust fast adaptive fault estimation for systems with time-varying interval delay

This paper studies the problem of actuator fault estimation for linear continuous systems, which is subject to time-varying interval delay and norm-bounded external disturbance. Based on the fast adaptive fault estimation (FAFE) algorithm, our attention is focused on the design of fault estimation filters to guarantee the filtering error system to be asymptotically stable with a prescribed H∞ performance. A delay-dependent criterion is established to reduce the conservatism of designing procedure, and the FAFE algorithm can enhance the performance of fault estimation. A novel Lyapunov-Krasovskii function is employed, which includes the information of the upper and the lower bounds of the time delay. An improved sufficient condition for the existence of such a filter is established in terms of the linear matrix inequality (LMI) by the Schur complements and the cone complementary linearization algorithm. In addition, the results for the systems with time-varying interval delay are simplified when the delay is constant and the delay is not considered. Four illustrative examples are given to show the effectiveness of the proposed method.