Study And Improvement On The Real Time Communications Of CAN Bus

In the area of FCS(field-bus control system) ,with low cost, easy design and inherent multi-host-communication mechanism, CAN (Control Area Network) has witnessed the rapid development. And with the expansion of FCS network scale and the application, the real time capability of its communication has been challenged greatly.Focusing on the real-time capability of CAN bus, based on its characteristics and main disadvantage, the theory of the real time capability of CAN-bus is analyzed, followed by a conclusion that with high load the network time delay would greatly augment. According to the CAN data link layer characteristic, a new schedule algorithm of time division multiplexing design based on dynamic PRI promote is presented. This algorithm can reduce the collision of network information without additional network load. On the other hand, a guarantee that the low PRI information still occupies a certain bandwidth under the condition of high load, is made in this algorithm. At last, the design of a network control experimental equipment is designed, and with the test data a conclusion can be get that the dynamic PRI promote CAN has less network delay over base CAN.The study in this thesis indicates that the dynamic PRI promote CAN has less network delay over base CAN and can grantee a low PRI information still occupying a certain bandwidth under the condition of high load.