Supervisory control of multilevel discrete-event systems with a bus structure

High-tech systems often contain a few components with many dependencies across the system, acting as system-level integrating components. In a hierarchical system decomposition, such so-called bus components tend to be placed in the top node. In supervisory control synthesis, this results in a significant increase of the state space. In this paper, a method is proposed to transform a set of plant models and requirement models into a tree-structured multilevel discrete-event system with a bus structure. After recording the dependencies within the system, the bus and the non-bus plant models are identified and separated. Subsequently, each set of plant models is clustered separately, resulting in a multilevel discrete-event system. Finally, these two systems are merged into a single multilevel discrete-event system where bus plant models are distributed over the multilevel discrete-event system. Experimental results of several models available in the literature are reported to assess the applicability of the proposed method.