Petri net controllers to enforce disjunction of GMECs

This paper deals with the problem of enforcing disjunction of GMECs on a Petri net (PN) system. The problem of enforcing a conjunction of GMECs is well known; anyway, it has been proved that in presence of uncontrollable transitions a GMEC has to be transformed into a proper disjunction of GMECs to be enforced in a maximally permissive way. On the other hand, some control problems have to be directly specified as a disjunction of GMECs; this is the case when the legal marking belong to a non-convex region. In the literature the problem has been solved by extending the standard enabling rule for PNs by using OR-logic. In this paper we propose a standard PN based controller to enforce a limited non-convex legal marking region under some restrictions.