Language model approach to nonblocking supervisor synthesis for nondeterministic discrete event systems

Considers the nonblocking supervisory control problems of nondeterministic discrete event systems (DESs) which are modeled as nondeterministic automata with ε-moves. Based on language models, the paper presents the necessary and sufficient conditions for the existence of a nonblocking supervisor to achieve a given language specification for a nondeterministic DES. The developed nonblocking supervisor always guarantees the absence of blocked states in a controlled nondeterministic system. Moreover, when the language specification does not satisfy the existence conditions, the paper provides the computational algorithm for finding the supremal language of the specification which satisfies the conditions. Furthermore, the results developed are demonstrated through the example of an assembly work station.