Study On CAN Communication Of Electronic Brake System For Commercial Vehicle

Electronic Brake System, which substitutes the electronic braking control signal for the pneumatic braking control signal of traditional barking system, reduces the reaction time of the braking system. Simultaneously, Electronic Brake System distributes the braking pressure, enhances the security and comfort during braking and gains the most optimal brake effect. The CAN communication is one of the key technologies. Study on this technology is the important part in the research of Electronic Brake System and the precondition of the self development of Electronic Brake System.Based on the corresponding research achievements abroad and domestic status of the technology, this paper addresses the study of CAN communication of Electronic Brake System and lucubrates on the aspect of communication protocol, hardware and software of the network nodes in Electronic Brake System for commercial vehicle. Besides, the on-road test of high and low attached road was implemented.First, the protocols of CAN2.0 and SAE J1939 are analyzed in detail. The framework and the type of the frame are introduced in this paper. Also, the error handling and error signaling are illustrated. The protocol of SAE J1939 is introduced according to the layers. Thus, the protocol lucubrating make atheoretic basis of further research in this paper. Before the design of CAN communication in Electronic Brake System, we should analyze the function requirements and the control strategy of the system, on the foundation of which, the design of physical layer structure and the design of data link and application layer is brought forward. This paper puts focus on the application layer design. In the light of priority, the addresses of network nodes and the identifier of 11 bits are defined. Besides, the content of transmitting signals and messages are defined in detail. After the protocol design, the protocol is simulated by using the software of CANoe of Vector Informatik Company. The simulation result shows that when communicating with this protocol, the performance of network communication is good; the busload and transmitting cycle delay are in the range of normal communication. Also, the busload will be smaller when actually communicating. Thus, the rationality and feasibility of protocol designed here are proved.Afterwards, the CAN bus nodes of Electronic Brake System are designed, which is the material step of realizing CAN communication of Electronic Brake System. This is illustrated in two aspects: hardware design and software design. The hardware of central control unit and wheel control unit is chosen. The 16 bits single chip of MC9S12DP256 is applied here, which has a CAN block as CAN controller. TJA1050 is applied as high speed transceiver. Central control unit circuit is designed, including power supply block and CAN bus interface circuit. In the circuit of CAN bus interface, optocoupler and optoisolater are applied to shield interfere. Besides, the wheel control unit circuit block diagram is presented. The host-control block software design of central control unit and wheel control unit are put forward and analyzed. And the software design of CAN communication block involves initialization of msCAN block and message transmitting/receiving. The idiographic software flow charts are given in thispaper and illuminated in term of software design principle.Finally, the foreign Electronic Brake System is analyzed for further research. The layout of system, structure of hardware and CAN communication are analyzed which make the preparation for on-road braking test. The braking evaluation test is completed on high and low attach road from which a method of braking performance evaluation test for Electronic Brake System is put forward.To summarize, this paper offers a powerful assist for further research and establishes the foundation for future analyses and development of CAN communication in electronic controlled system.