The Design Of Vehicle Body Information Monitoring System Based On CAN Bus

With the rapid development of the modern automobiles,the lasting increase of electronic devices of automobiles,the traditional wiring harnesses can not satisfy much more complexity of control systems of automobiles. The network control system for automobile is developed ,which takes advantage of the technical achievements in the fields such as electronic, computer, sensor and controlling. In order to solve the questions that the automobile wiring becomes huge and complex,the system is unreliable, the difficulty of breakdown maintenance is big. A kind of automobile network control system based on CAN bus is designed. CAN bus make the real-time, stability,safety and economy of the automobile much better. As the development trend of the LAN of the automobile,CAN bus,as the representative of C class networks ,will be popularized gradually and hold a dominant position.According to the characteristic of automobile electronic ,based on researching the standard of CAN protocol technology,the acquisition and processing of the analog signal,digital signal and switching signal are completed; the display such as oil mass, water temperature, rotational speed, the speed of vehicle etc. alarm of overrun and control state of light is realized, A kind of CAN gateway is designed, with the aim of realizing data communication between high-speed CAN and the low-speed CAN communication.A USB to CAN adapter is designed by myself. Terminal sends the control signal to the bus,the signal is fed back to the monitoring software after the successfully controlling of the corresponding node. The communication between CAN node and Terminal is realized. In the first place,the monitoring software can monitor the operation of the system,in the second place,the fault analysis is running.The standard of CAN has only defined the protocol of the physical layer and the data link layer, so the system establishes the application layer protocol for the automobile CAN network control. The system uses the expansion patterns of 29 identifiers, which defined two-byte identifier and one-byte data field code. Each device leaves wide resources for the future expansion when the protocol updated.To the incertitude of fault diagnosis, the decision-making fusion based on evidence theory is put forward. The basic conception of evidence theory is introduced.With the simulation based on the example, we can know evidence theory fusion improved the fault diagnosis precision. It is hard to give the basic probability function in the process of using the evidence theory, so the model based on network and D-S evidence is put forward. The simulation of the example show it is feasible and effective.