Design And Application On Bus Communications Protocol Based On SAE J1939

As the vehicle's energy, emissions, noise regulations become increasingly stringent, and customers'needs for comfort, security and entertainment are further improved, traditional purely mechanical devices have been unable to meet the regulations'and customers'demands for automobile high performance. The developments of network communication, computer and control technology make more and more automobile electronic technologies to be applied to modern automobile. The rapid developments of automobile electronic technology make the communication mode of vehicle network which every electronic control system in the automobile uses become very necessary. Vehicle network not only can reduce wiring harness of electronic systems and automobile's manufacturing cost, but also can achieve every system information sharing, make automobile more intelligent and integrated, form the basis for further improving vehicle performance and expanding system function. Therefore the protocol of vehicle network communication is one of the core technologies of Automotive Electronics. The design of vehicle network communication protocol is the prerequisite and basis for independent research and development of electronic control system.This paper combined with "Automotive Smart & Integrated Control System CAN communication protocol design and application" project which Jilin University cooperate with Xiamen King Long United Automotive Industry Co Ltd, researches the CAN bus protocol's design and application on bus communication networks, designs the communication protocol used in passenger cars, develops the software that can analyze network communication protocol. Finally, tests components and carries out vehicle test, analyses the bus communication network's performance. As the specific works: Firstly, sorts vehicle network protocols, and chooses the low-cost and flexibly configurable CAN bus from five sorts of vehicle network as the base of bus communication network. After analyzing the features of CAN bus, analyses the high-level CAN protocol SAE J1939 according to OSI seven layers network model in detail, especially Data Link Layer, Application Layer, Diagnostic Mechanism and Network Management Protocol. These works form the basis for formulating the bus communication protocol.Before designs bus communication protocol, this paper analyses and formulates the control strategy of bus electronic control system, designs the communication network topology. Then designs the bus network communication protocol XMQ J1939 that based on SAE J1939. Defines continuous and discrete parameters for bus network communication, designs the parameters group according to the principles of SAE J1939. Based on bus fault diagnosis demands, formulates fault diagnosis mechanism and designs diagnostic protocol. Also designs bus communication network's compatibility mechanism, allocates network address to each node's ECU. And the way of network address arbitration is designed to make the network more reliable. In order to analyze the data on CAN bus when does components and vehicle test, according to users'needs, builds the system architecture model with Unified Modeling Language UML, selects Visual C++ development environment to design the protocol that based on the SAE J1939 analysis software.At last, carries out components test and vehicle test. For testing control system components, designs the testing process, detects communication data frame of the control system and the contents of return message include of fault diagnosis message, exams the compatibility mechanism to ensure that all parts of the control system can meet the requirements of bus communication protocol, and can carry out vehicle test. In the vehicle test, there are static tests and dynamic tests. For all of control system components that fitted on the bus, besides the contents in the components test, also carries out the electronic control unit exchanging test, that can verify the control systems which have same functions can work stably without modifying the software or hardware. The analysis of vehicle test data proves that the load rate of CAN bus, the rate of order message transmission delay and equipment response delay time are in the normal range, the bus communication network have good performance.The bus communication protocol designed in this paper will help vehicle enterprises control manufacturing cost, and home automotive electronics corporation improve technology, in the mean time, lays a good foundation for CAN bus function expansion in the future.