Invariant sets computation for convex difference inclusions systems

In this paper we introduce the Convex Difference Inclusion (CDI) systems as a modeling framework useful to analyze set-theory and invariance-related issues for nonlinear and uncertain systems. The dynamics of a CDI system is given by a set-valued map whose values are convex, compact subsets of the space and are determined by convex bounding functions. Necessary and sufficient boundary-type conditions for invariance and contractiveness, characteristic of the linear systems, are given for the CDI systems. Lyapunov functions are proved to be induced by contractive sets for CDI systems, as in the linear context. A computational procedure for obtaining polytopic invariant and contractive sets for nonlinear systems, based on the properties of the CDI systems, is presented.