Can Bus Network Real-time Analysis

Along with the rapid development of the computer technology and network communication technology, the field-bus technology has been more and more widely applied to industrial control field. The CAN bus is the most potential field-bus in industrial control field. It has advanced technology, high reliability, good stability, complete functions, rational cost, etc. In the actual application of industrial control system, the real-time transmission of message is very important. In some situation of higher real-time demand, message delay can cause the error control of system and accidents. The message delay doesn't allow. Therefore, the real-time has become a hot issue about application research in CAN-bus.Firstly, the article expounds the type and main characteristics of field-bus technology, and emphatically introduces the agreement standard and a message transmission and encoding mode in CAN-bus technology. According to the agreement standard, it has a deep research on the reason which caused the CAN bus delay. The paper analyses the delay time of each part, gives the mathematical model of the delay time, and calculates the different delays in the different CAN-bus networks. It analyses some improving methods about real-time in CAN-bus and points out some shortcomings of these methods. According to the principle that dynamic change of priority can improve real-time, it designs a kind of improved method of dynamic allocation priority and makes it realize by software.It is based on iCAN agreement which is independently researched and developed in CAN bus application-layer protocol in our country. It expounds the structures about various communication layers in iCAN agreement, including message formats and message transmission standards in iCAN. It has researched iCAN experimental teaching development platform which is developed by Guangzhou electronic. According to the characteristics of platform, the function of each module and relevant test software are discussed and practiced.This paper has established three different CAN networks which are mainly based on iCAN agreement. It provides a fast and reliable method to construct a CAN-bus network for industrial automatic control field. At the same time it has realized the CAN network performance analysis. The designed CAN control networks are a test platform. It tests the different delays in different CAN network, and records a lot of test results. The method of improved dynamic allocation priority has been applied to the actual CAN network, and the algorithm has been tested. The test results verify the feasibility of the algorithm for improving real-time in network. It provides a new method for improving the real-time in CAN network.