Decentralized supervisory control: Nondeterministic transitions versus deterministic moves

This paper addresses the existence problem of the global supervisor for a distributed plant so that the closed loop system satisfies a global linear temporal logic specification given in a decomposable automaton. The paper shows that if there exist local supervisors for individual sub-plants of a distributed plant, then a global controller exists for decentralized supervisory control of the plant. This existence result is shown for two types of distributed plants: loosely cooperating (with deterministic events and disjoint synchronization on the common events) and synchronously communicating (with joint synchronization on the non-deterministic common events) distributed discrete event systems. For supervisory control of nondeterministic transition systems, a new notion of synchronized simulation relation is introduced to design the decentralized supervisor using synchronous product composition. An example is given to illustrate the concept of synchronized supervisory control of nondeterministic plants. This work is a new contribution in synchronization of nondeterministic events and actions in supervisory control.