Study On Controller Area Bus Based Communication Model

Fieldbus is a bus topology network used in the bottom layer of controlling system. In recent twenty years, there are several successful fieldbus in use, such as FF(Foundation Fieldbus), LonWorks(Local Operating Networks), PROFIBBUS, HART(Highway Addressable Remote Transducer) and CAN(Controller Area Network) as so on. Fieldbus control system not only an open communication network, but also a distributed controlling system. Its real time capability is determined by temporal characteristics of communication network (fieldbus) and with the increasing applications of fieldbus system in industrial control areas, the research on fieldbus's capability of handling real time traffic of message is becoming more important.Some scholar proposed control whole network by the prior frame, in fact it is a centralized token control way. Its communication model should been an arbitrator-producer-consumer model. In this model, it is difficult for the parameters of the equipment to be setup, and it is difficult to change since have been set first. Otherwise the real time capability of the node needs more calculate capability.According to the popular communication model base on CAN, this paper proposes a distributed real time communication model: producer-arbitrator-consumer (PAC) model. The identifier of arbitrator should be lowest priority in the network first. In the process of the message from producer to arbitrator, the message should be communicated with event-triggered traffic by producer. After the arbitrator received the messages from producer, it will send the messages to consumer with a police which combined cycle and not cycle traffic. In the basic cycle of arbitrator sending message, there are some time left to use sending messages by producer, because the priority of message from producer is lowest. The identifiers of all equipment are set facility and every message can traffic with priority in PAC model. Otherwise decrease the dependence of hardware.