Development Of Pure Electric Vehicle Fault Diagnosis System

According to the statistics, the time needed for finding out traditional auto malfunction accounts for about70%, while the time for troubleshooting and repairing30%. Compared with the traditional vehicles, the mechanical structure of the pure electric vehicles is simple, but the electrical structure is complex, which an electronic integration system composed of multiple distributed subsystems. Once the electrical or communications failure occurs, it’s difficult to rule out the vehicle fault based on experience and traditional hand tools. Therefore, the development of on-board diagnosis system is more necessary.The pure electric vehicle fault diagnosis system, based on ISO15765protocol, which includes the on-board diagnostic management unit and fault diagnosis unit was developed. Firstly, studied the ISO15765protocol deeply. Corresponding to the OSI7layer reference model, analyzed the physical layer, data link layer, network layer and application layer specific application. Based on the deep understanding of ISO15765application layer protocol, the fault diagnosis system diagnostic protocols was defined in this paper:referring the fault code defined in ISO15031-6, redefined the fault code format adapted to the distributed system of pure electric vehicles; analyzed the specific parameters involved in the data flow transformation between the bus value and physical; designed the diagnosis services, including to read fault information, to clear fault codes, to read the data flow, etc. Then respectively designed the hardware and software for on-board diagnosis management unit and fault diagnosis unit. In front of the design of on-board diagnosis management unit, analyzed the functional requirements-vehicle safety monitoring, troubleshooting and diagnostic communication with external equipment fault diagnosis. Developed the hardware system and wrote the modularized software code to satisfy the function. Based on the detail analysis of the fault diagnostic equipment function, developed the hardware system and wrote the modularized software code. Finally, simulation and real vehicle testing was carried out to verify fault performance of the system.In the simulation test, a car bus analysis system was used to simulate on-board network nodes sending messages periodically. At the same time, monitored the sending and receiving diagnostic communication messages as well as the display results. Results showed that the system was able to implement the diagnosis communication function correctly in accordance with the agreement. The real vehicle test results showed that the system can satisfy the requirement of complex electromagnetic environment with high accuracy and reliability.