Design Of Fault Diagnosis System Based On MC9S12XEP100 For A Pure Electric Vehicle

The problem of environmental pollution and energy consumption caused by traditional cars needs to be solved urgently,In recent years,the state has extremely supported the development of new energy vehicles,Pure electric vehicle(EV)has it’s own characteristic of no exhaust emissions,low noise,high energy conversion rate compared to traditional cars,recyclable braking and downhill energy,that make EV more acceptable.However,most EV is still under testing,and the failure rate is relatively high.The level of electrification and automation of EV is very high,but there is also a shortage of service technicians and experts who can master the high-tech of EV.Diagnostic criteria of Each EV manufacturing plants is different,resulting in repair shop diagnosed different manufacturers of cars increased maintenance costs.Meanwhile,high-voltage devices and other damage can cause fatal accidents in the driving process,Therefore,there are fault diagnosis system is even more necessary.Designing a smarter,more humane,safer,pure EV diagnostic system requires a more intelligent "brain" to control,And vehicle controller as a "brain" is the core controller of the EV,It controls the vehicle’s operating status and energy management,the fault diagnosis function based on CAN bus of vehicle controller will read the relevant fault data frame,monitor the failure of the various components of the system in real-time,and provide the corresponding fault judgment and strategy to make its security,reliability improved greatly,that also provide a reliable basis for the maintenance and repair of EV.The background and significance of this subject are explained,The domestic and international status quo of EV fault diagnostic study are introduced.The architecture of fault diagnosis standard ISO 15765 is analysed,diagnostic communication protocol based on ISO 15765 is addressed: the application layer of diagnosis service is designed;When the data link layer CAN extension frame is designed,according to the requirements of each EV subsystem,CAN message is formulated.The service provided by the network layer to the application layer is introduced.The protocol unit of the network layer is analyzed and the data flow control management is designed.The diagnostic communication protocol for EV is developed.The overall scheme of fault diagnosis based on vehicle controller is designed,the powertrain diagnostic architecture is introduced,The fault diagnosis code,fault diagnosis mechanism,and fault classification of pure electric vehicle were established,and the fault diagnosis strategy design of the powertrain was completed.The development platform of EV fault diagnosis system is designed.Vehicle controller fault diagnosis hardware based on MC9S12XEP100;The vehicle controller software,including the main program,analog acquisition and fault diagnosis program,are designed;The PC software,including reading the fault code,clearing the fault code and reading the data flow,are designed.To verify the availability and feasibility of EV fault diagnosis system designed in this paper,hardware-in-the-loop system test platform based on dSPACE is designed,and the relevant fault is injected into vehicle controller for simulation test.The test results show that the fault diagnosis system of pure electric vehicle can meet functional requirement.