Multiple Composition Petri Net Based Mechanism Research Of Multi-Fieldbus Protocol Conversion System

The development of fieldbus & industrial Ethernet is very advantageous for industrial control networks, nevertheless it results in some new problems and challenges. The diversity of industrial communication networks provides broad living & applied space, but at the same time it leads to a mess of multiple standards. The above problems are waiting to be solved, moreover, the extensive interests of commerce & technology have to be considered and the development of this technology field should be promoted rapidly. According to these factors the technology of multi-protocol conversion is effective & practical.In this paper, the MODBUS/TCP industrial Ethernet, which is applied widely, and DeviceNet & Profibus DP fieldbuses, which are representative device layer fieldbuses among multiple fieldbus standards, were researched objects. The message communication processes of these protocols were analyzed deeply and the principle & performance model of multi-protocol conversion system were made. Further the performance of multi-protocol conversion system was analyzed as to theory & experiment. Finally a small process control system, in which the core device was multi protocol converter and the controlled object was a small boiler, was constructed. The main contributions are as follows:1. The conception of multiple composition Petri net was presented and it was supposed that multiple similar Petri net models could be composed based on public places or public transitions, which behaved similarly. The above conception laid theoretical foundation for principle model of multi-protocol conversion system. 2. Two specialized conceptions, namely, state constancy and behavior constancy were presented. Under different composition situations, the boundness property, liveness property, state constancy and behavior constancy were all analyzed and the necessary and sufficient conditions for above properties were proposed. These conclusions guaranteed the correctness of principle model of multi-protocol conversion system. 3. According to the communication processes of MODBUS/TCP industrial Ethernet, DeviceNet, and Profibus fieldbuses, all communication state machines were uniformed into three stages, namely communication preparation, message communication and communication abort, and communication models of every protocol were made. Based on these communication models, the s-multi conversion Petri net model, in which the...