COUPLING BETWEEN THE MODELING AND CONTROLLER-DESIGN PROBLEMS .1. ANALYSIS

Controller-design issues influence modeling decisions; therefore, the modeling and controller-design problems are coupled. Part I of this th is paper proposes a quantification of this coupling in terms of the si ze of the set of models from which satisfactory controllers may be der ived. Moreover, in the context of an extremely general frame work, we prove that the coupling increases us performance specifications are ti ghtened and as uncertainty is increased. Further more, the existence o f a preferred model for controller design is demonstrated; this model is preferred in rite sense that its nse leads to improved robustness o r performance. However, this model does not necessarily satisfy our in tuitive notion of a worst-case model; rather; it depends on the perfor mance specifications and uncertainty. The analysis of coupling present ed here in motivates the design approach formulated in the companion p aper, Part II.