Pertubation in the I/O Map of a Non-linear Feedback System Caused by Large Plant Perturbation

This paper studies the perturbation in the input-output (I/O) map of a multi-input multi-output non-linear feedback system caused by large plant perturbations. It compares the effect of these perturbations on the given feedback system and on the nominally equivalent open-loop system. First the unity feedback system is considered, then a more general configuration—which includes the usual summing node as a special case—is analyzed. In both cases it is shown that the degree of desensitization provided by feedback is controlled by the linearized return difference operator.