Some results on the integration of manufacturing systems using Petri nets

This paper presents some results on the integration of manufacturing systems using a modular approach based on Petri nets. We first define a class of Petri nets called controllable-output nets (CO-nets) which characterizes most real-life manufacturing modules. More precisely, a CO-net is an acyclic Petri net with input-output transitions in which each output transition corresponds to a t-invariant whose support does not contain any other output transition. The CO-nets are live, reversible and consistent. Most important, we prove that the integration of the CO-net modules preserves these properties under some fairly weak conditions. The second part of the paper concerns the abstraction of module models The abstraction is important if the integrated model is to be used to manage the related system in a hierarchical way. For this purpose, we introduce the notion of reduced t-invariants which characterizes the token flow relationship of the input/output transitions of a Petri net module. An efficient algorithm is proposed to calculate a generating family of the reduced t-invariants