Relations between Properties of Multivariable Feedback Systems at Different Loop-Breaking Points: Part II

The purpose of this paper is to investigate the relation between feedback properties at the input and output of a multivariable plant. These properties may differ significantly at frequencies for which the plant transfer function has a high condition number. Furthermore, properties at one point may be relatively insensitive to uncertainty at that point, yet be extremely sensitive to uncertainty at the other. We use the structure of a highly conditioned plant to determine when these difficulties may exist and to suggest ways in which they may be circumvented, if possible.