H∞ performance of weighted interval plants: complete characterization of vertex results

Recently, it has been shown in [1] that the worst-case H_∞ norm of an interval plant weighted by the transfer function p(s)/s^l(s + α) is achieved at one of the so-called weighted Kharitonov plants. In this paper, we show that this class of weights is maximal in the sense that more complex weights do not generally lead to such extremality properties.