An approach to the design and implementation of the hierarchical control system of FMS, combining structured knowledge representation formalisms and high-level Petri nets

A presentation is made of the methodology adopted in the design of the coordination subsystem and the real-time scheduling subsystem for the simulation and the real-time control of flexible manufacturing systems (FMSs). This particular approach, combining structured, object-oriented paradigms and a particular extension of high-level Petri nets, is presented and discussed. The focus is on the following issues: (1) the modeling of the FMS control system in a structured knowledge base (frame-based multiple-inheritance semantic networks); (2) the automatic synthesis of Petri net models of the coordination subsystem, starting from such a knowledge base; (3) the dynamic behavior of the coordination subsystem; and (4) the structure of the real-time scheduling subsystem, based on particular heuristic suboptimal multicriterion algorithms. The interaction mechanisms between the coordination and scheduling subsystems are defined. A particular case study involving a class of problems on the concurrent scheduling of multiple projects is taken as an example