Reduction of model sets with inclusion

The problem of model set reduction with inclusion is formulated for the purpose of simplifying: the design of robust control systems. The problem is solved for model described by linear fractional transformation(LFT) with a generalized plant and an uncertainty. We introduce a new notion of model set inclusion in our model set reduction problem so that the reduced model set of smaller degree has to include the original model set. A necessary and sufficient condition for this inclusion to hold was found ill terms of a structured singular value inequality. A computationally tractable method for model set reduction is obtained for special case, single input single output, additive perturbed plant. The effectiveness of our method was demonstrated by numerical examples.