The Design Of Center-Controller Node In Electric Vehicle Based On CAN-BUS And The Realization Of Protocol

Electric vehicles with the advantages of high efficiency, energy saving, environmental protection, low noise and so on, will be the ideal transport in the future.But for the large number of electronic control systems have been applied in electric vehicles, the traditional wiring methods will inevitably lead to some new problems: the harness lengthen and complexity increased, system reliability reduced, the weight of body increased, the difficulty of the manufacture, installation and maintenance of vehicles electrical systems will also be increased. The CAN-bus technology appeared in the 1980s is the best way to solve such problems.In the electric vehicles, center controller which is the core of the whole control system, play a role in the global control. The center controller node is the core component of the center controller; it is the device which is responsible for transferring information between center controller and other control unit. Its performance directly influences the control effect of the whole control system. Therefore, the development of a fully functional center controller node is the essential task in the process of vehicle control system commercialization.This thesis carries out research on the design of center controller node and the realization of protocol in electric vehicle.First of all, we should deeply study the technical specifications of the CAN bus, starting from the characteristics of CAN bus, carefully analyze CAN2.0 technical specifications, including the CAN bus relate concepts, its hierarchical structure, the four frame types and their structure, focusing on Analyzing the communication theory and communication processes of CAN bus, provide a theoretical basis for CAN bus applications in electric vehicles.After studied the hardware structure of communication node of CAN bus, we complete the hardware design of the center controller node in electric vehicle, according to the characteristics of the node and functional requirements. The design of the CAN intelligent node circuit of center controller node adopts MCU+ independent CAN controller + CAN transceiver. Main chips select microprocessor P89C669FA, independent CAN controller's selection SJA1000, CAN transceiver TJA1050. As the selected chips are all produced by Philips, making the hardware circuit has a high degree of compatibility. Center controller has been modular designed under the design requirements of the center controller, including a power supply module, analog input module and digital input module.In order to achieve the functions of the center controller node ,after completed the hardware circuit design of the center controller in electric vehicle, we also design the perfect software. The design idea of software design is as follows: first initialize the CAN controller SJA1000; then design the send and receive procedures of CAN communications packet, while also including the necessary interrupt procedures; last design the corresponding application procedures for the circuit chip of its hardware extensions. The flow charts of program design have been given.CAN bus protocol is divided into three layers: physical layer, data link layer and application layer protocol. CAN bus protocol strictly defines the physical layer and data link layer protocol, but for the application layer protocol is not strictly defined, requiring users to design their own based on their needs. There is currently no uniform electric vehicle application layer protocol standard; we design the electric vehicle application layer protocol according to the electric vehicle characteristics. In order to make the designed application layer protocol more standard, we reference to the most popular SAE J1939 agreement in the process of making protocol. SAE J1939 protocol is SAE (Society of Automotive Engineers) published the standard communication protocol based on CAN bus vehicle serial communication and control network protocol standards. J1939 protocol with CAN2.0B agreement as the core, according to OSI hierarchical structure, defines the network layer and application layer protocol on the basis of defined physical layer and data link layer in the CAN bus. In this paper, based on SAE J1939 protocol, combined with the characteristics of electric vehicles and the actual needs, detailed defined the ID and Date of electric vehicle protocol, completed the coding design of the communication protocol. We have formulated electric vehicles application layer protocol.After that we need protocol simulation. In this paper, Vector's CANoe software was used to simulate the designed application layer protocol. Protocol simulation is divided into three steps: using CANdb++ to establish a database, establishing a simulation model, realizing node communication through CAPL program. On the analog network monitoring, network operation and stability, communication was good. Concluded that the electric vehicles designed protocol is rational and to meet the design requirements.In summary, this research work provides a strong support for further study of the electric vehicles. Not only complete the hardware and software design, but also Propose the design method of meet the functional requirements of the CAN communication protocol, lay the foundation of Research and Development on CAN network communication in electric vehicles in the future.