H∞H∞ filtering for discrete-time systems with time-varying delay

This paper focuses on H∞H∞ filter design for discrete-time systems with time-varying delay. A delay-dependent H∞H∞ performance analysis result is first established for error systems without ignoring any terms in the derivative of Lyapunov functional by considering the relationship between the time-varying delay and its upper bound. The resulting criterion is extended to systems with polytopic-type uncertainties. Based on the derived H∞H∞ performance analysis results, the H∞H∞ filter is designed in terms of linear matrix inequalities (LMIs). Numerical examples are given to demonstrate the merits of the proposed method.