Vertex results for parametric H-infinity problems of weighted interval feedback systems

This paper deals with the parametric H-infinity problems of weighted interv al feedback systems. It will be shown, by an example, that the maximal H-in finity norm of the first-order weighted sensitivity function does not enjoy the extremality property generally, but it is achieved at one of the 16 ed ge plants and this result can be generalized to the case of some high-order weighting functions. The conditions under which vertex results hold will b e investigated finally. (C) 2000 Elsevier Science B.V. All rights reserved.