Supervisory control of partially observed discrete event systems with arbitrary control patterns

In this paper, we study supervisory control of partially observed discrete event systems with arbitrary control patterns. First, we present a necessary and sufficient condition for the existence of a supervisor for a given non-empty and closed language K. Next, we consider the case where the language K does not satisfy the condition. We prove that there always exists its infimal superlanguage for which there exists a supervisor when the set Gamma of control patterns is closed under intersection. This infimal superlanguage is the optimal solution larger than K. On the other hand, when Gamma is closed under union, there does not necessarily exist its supremal sublanguage for which there exists a supervisor. In other words, the optimal solution smaller than K does not exist in general. So, in this case, we present a suboptimal solution smaller than K.