Constraint function based hierarchical control of discrete event systems

Due to the introduction of uncontrollable transitions in the supervisory control of discrete event systems modeled by controlled Petri nets, a disjunction of several linear inequalities is needed to express the admissible markings. In this paper, we propose a two level hierarchical control synthesis method to deal with this kind of OR logic constraints. In the method, the constraint function plays an important role not only in the construction of the low level monitor but also in the determination of the control policy. The obtained supervisor is maximally permissive and the online computation has the complexity of polynomial times. An example is used to illustrate the proposed synthesis algorithm.