Research And Design Of VCU Diagnosis System For Electric Vehicle

Compared with traditional fuel vehicles,electric vehicles with small environmental load are getting more popular from the effect of the increasing world environmental awareness and the domestic preferential tax policy.Because electric vehicles are equipped with more electronic equipment than traditional fuel vehicles and exchange greater data between devices than traditional fuel vehicles,the diagnosis and detection of electric vehicles is not the traditional mechanical repair,but combination of modern electronic diagnosis technology and the traditional mechanical repair.Thus it makes the diagnosis and detection of electric vehicle become a new technical challenges for enterprise.It is in the thesis mainly studied the program update of Vehicle Control Unit(VCU)and the fault diagnosis for electric vehicles,and a VCU diagnosis system for electric vehicle based on ISO15765 is designed by using CAN bus technology.This system can realize the function of VCU program updating and CAN system fault diagnosis.The mainly contents are as following:(1)The relevant technical standards for system design are studied.The architecture of ISO15765 protocol and the technical feature of CAN bus and the protocol specification of CAN bus are analysed.In addition,the main functions of VCU and the main performance indexes of Infineon XC2000 MCU are introduced.(2)An underlying programming protocol stack in line with ISO15765 standards is developed.The XC2000 online programming process is established,which includes initialization,key authentication,Flash partion erasing,Flash partion writing,etc.The XC2000 Flash driver is developed to implement Flash block erasing and writing by address.The bootloader is developed to implement hardware resource initialization and ISO15765 protocol stack loading.(3)An underlying fault diagnosis protocol stack in line with ISO15765 standards is developed,which can implement the function of DTC reading,DTC cleaning,data flow reading,actuator testing and so on.(4)A host computer electric vehicle diagnosis system is developed.The host computer system and underlying protocol stack are joint tested by the Hardware-in-the-loop Test Bench.The results show that the VCU diagnosis system for electric vehicle based on CAN bus has ECU online programming,fault diagnosis and data management functions,achieving the technical goals.