Structural Decentralised Control of Concurrent Discrete-event Systems

摘要

A problem in a decentralised control of concurrent discrete-event system is formulated. We consider a system consisting of a number of subsystems and specifications are given locally on the subsystems. The problem is to find a set of 'structural' conditions under which, for a set of local specifications, the concurrent actions of decentralised supervisors will achieve the global optimality, and control of one subsystem never causes blocking in the other subsystems. This problem can be seen as that of achieving the distributivity of the control synthesis operator over the synchronous composition. We call the condition 'structural' since unlike the previous works, once the conditions are verified for a given system, decentralised control can be achieved for a set of specifications. Two sufficient conditions are obtained. The first condition, the shared-event-marking condition, requires the states before the shared events in subsystems to be marked. The second condition, the mutual controllability condition, may be interpreted as that a subsystem needs to track any uncontrollable shared event that could occur in the other subsystems. Examples are provided for illustration.