Robust H∞ filter design for uncertain nonlinear discrete systems with state delay

In this paper, we address the problem of robust H∞ filter design for a class of nonlinear discrete-time systems with norm-bounded parameter uncertainty, unknown state delay, and unknown nonlinear disturbance. Firstly, the suffident condition of the existence of the robust filter is analyzed by the modified Riceati inequalities, such that the filtering process remains robustly stable and a prescribed H∞ performance lever is achieved. Then the filter is characterized in the terms of positive solutions of two algebraic Riccati-like equations, irrespective of the uncertainties, time delays and nonlinearities. The simulation example further shows the validity and the applicability of the proposed approach.