CASE application of colored Petri nets to development of a distributed scheduling system

Floor level control systems such as scheduling and production monitoring systems differ from conventional software systems of plant, once they are highly integrated with the physical production system. Similarly to sequential control systems, the plant and the control system may not be considered independently, once both are mutually dependent. This is an extremely complex issue specially when dealing with the integration of the plant floor level with other higher levels of the system also when dealing with new requirement of safety, variety and speed. This work proposes a modeling technique based on colored Petri nets (CPN) which allows not only the hierarchical modeling of data and material flow in the system on the same model, but also with clear division and representation of interactions among the production and data handling components. Advantages of the authors' CASE (computer aided software engineering) modeling technique are demonstrated by applying it to the development of a distributed scheduling and monitoring system of a multi-layer PCB board production line. The generated plant model was used to the analysis and evaluation of the production process. The same model was used for the proposal and validation of a distributed and dynamic scheduling system, and also a production monitoring system. The proposed approach may also be used for allowing a smooth of the integration of plant floor level with higher level control and administrative systems.