GEOMETRIC APPROACH TO SIMULTANEOUS SYSTEM DESIGN: PARAMETER INSENSITIVE DISTURBANCE DECOUPLING BY STATE AND OUTPUT FEEDBACK.

In this paper we obtain a necessary and sufficient condition to the problem of constructing a fixed control, for a family of input-output systems with an additional disturbance input, that decouples the disturbance from the output in each of the plants. We show that when such a control does exist, it can be synthesized by a state feedback through a nonswitching gain. On the other hand, if the state is not available for feedback, we consider feeding back the output through a dynamic compensator and obtain a necessary and sufficient condition for the above simultaneous disturbance decoupling problem under certain special cases. Our approach generalizes the geometric approach introduced by Basile/Marrow, Wonham/Morse and by Schumacher.