On the Synthesis of Safe Control Policies in Decentralized Control of Discrete Event Systems

State estimation and safe controller synthesis for a general form of decentralized control architecture for discrete event systems is investigated. For this architecture, controllable events are assigned to be either ``conjunctive'' or ``disjunctive''. A new state estimator that accounts for past local control actions when calculating the set of estimated system states is presented. The new state estimator is applied to a previous general decentralized control law. The new control method generates a controlled language at least as large as that generated by the original method if a safety condition is satisfied. An algorithm for generating locally maximal control policies for a given state estimate is also discussed. The algorithm allows an amount of ``steering'' of the controlled system through an event priority mechanism.