Kybernetika

In this paper we consider the feedback-action for reachable singular systems and its limit phenomena. Firstly we introduce the invariants which parametrize the feedback-orbits. These results were published in part a few years ago independently by different authors (see \cite{GluL90,KaHe89,MKZ90}). Then we characterize the orbit closures in the space of all reachable systems in terms of these invariants. This gives a contribution to the answer of the question: how does a system might look like, which occurs as the limit of a sequence of feedback-transformations, applied to a given system?