The authors deal with mode and parameter-dependent robust mixed ℋ₂/ℋ_∞ filtering design for a class of discrete-time switched polytopic linear systems. The objective is to design a homogeneous switched mixed ℋ₂/ℋ_∞ filter guaranteeing the asymptotic stability of the resulting filtering error systems with given performance measures. Based on a switched parameter-dependent Lyapunov function combined with Finsler's lemma, some novel conditions for robust ℋ₂ and ℋ_∞ performance analysis are proposed and in turn the filter synthesis is developed. It is shown that by using a new linearisation technique combined with a bounding approach, the filter gains can be obtained by solving a set of linear matrix inequalities. Finally, a numerical example is provided to illustrate the effectiveness and less conservatism of the proposed approach.

A generalised H₂ controller synthesis method for discrete-time fuzzy systems based on a piecewise Lyapunov function is presented. The basic idea of the proposed approach is to construct a controller for the discrete-time fuzzy systems in such a way that a piecewise Lyapunov function can be used to establish global stability with generalised H₂ performance for the resulting closed-loop fuzzy control systems. It is shown that the control laws can be obtained by solving a set of linear matrix inequalities that are numerically tractable with commercially available software. An example is presented to demonstrate the advantage of the proposed approach.