SOME RESULTS ON SENSITIVITY OF GENERAL INPUT-OUTPUT SYSTEMS

We consider general input-output systems, which need not be of a feedback type, that are governed by nonlinear operator equations which relate the input, state, and output. Assuming that these equations depend on a parameter A which is allowed to vary in a neighborhood of a "nominal value" A0, we study the dependence of the output on A when the input is fixed. Essentially, we call a system insensitive if the output depends continuously on A. Two insensitivity concepts are introduced, and it is shown that certain monotonicity-like conditions ensure insensitivity. Also, several particular cases of the governing equations are studied. As examples, a control system described by a singular system of ordinary differential equations and a nonlinear feedback system are discussed.