Arborescent architecture for decentralized supervisory control of discrete event systems

Decentralized control of discrete event systems consists in using local supervisors that observe locally the plant and compute local decisions to enable or disable events; those local decisions are transmitted to fusion modules that combine them to generate global enablement/disablement decisions that are actually applied to the plant. C&P and D&A controls are the two simplest systematic decentralized controls. Inference-based control is the most general systematic decentralized control, which generalizes significantly C&P and D&A controls. In this paper, we first propose a method that realizes a control objective C by an arborescent architecture (or tree). Each leaf of the tree is a decentralized control, and each node n is a disjunction or conjunction of the enabling/disabling decisions of the two children of n. We show that if the control objective C is realizable by inference-based control, then every leaf of the obtained tree is a C&P or D&A control. This means that by combining adequately C&P and D&A controls, we can realize every control objective that is realizable by inference-based control.