The structured singular value (s.s.v) mu enables the study of robust stabil
ity and performance of a controller in the presence of real parametric unce
rtainties and complex uncertainties corresponding to neglected dynamics. In
spite of the NP-hard characteristic of the problem, it is now possible to
compute an interval for the s.s.v. mu using polynomial-time algorithms. The
skewed s.s.v. nu was introduced by Fan and Tits(1) in the context of robus
t performance analysis. The primary aim of this paper is to propose a new m
ixed nu upper bound, which is applicable to problems with a special, but pr
actically important, structure. We then illustrate through a realistic miss
ile example that certain problems naturally require the nu tool rather than
the mu tool. Copyright (C) 1999 John Wiley & Sons, Ltd.