Improved robust H∞ filtering for polytopic delta operator systems

The problem of robust H_∞ filtering for polytopic Delta operator systems is investigated. The main purpose is to obtain a stable and proper linear filter such that the filtering error system remains robustly stable with a prescribed H_∞ attenuation level. Based on the bounded real lemma, a more efficient evaluation of robust H_∞ performance can be obtained by a matrix inequality condition which contains additional free parameters. When applying this new matrix inequality condition to be the robust filter design, these parameters provide extra degrees of freedom in optimizing the guaranteed H_∞ performance and lead to a less-conservative design. A numerical example is included to illustrate the effectiveness of the proposed approach.