Analysis Of Power System And Study Of Its Fault Diagnosis For Electric Vehicles

At Present,As New Energy Vehicles have become a new strategic industry in China's industrial filed,domestic vehicle manufacturers and parts suppliers launch different levels of research and development on it.Electric Vehicles,the important part of New Energy Vehicles,is a hot spot pursued by current manufacturers.In particular,the intelligentization and networking of Electric Vehicles have attracted more and more attention from the traditional Internet industry.However,“3 electric” technology(battery,motor and electric control)as the key core technology of the power system of Electric Vehicles has not yet been fully grasped by domestic vehicle manufacturers.At the same time,the power system of Electric Vehicles,which is a new high voltage system,has certain difficulty and danger in development,debugging and maintenance.In addition,the fault diagnostic system based on CAN bus for vehicles is becoming the most basic requirement of the intelligentization and networking of vehicles.Therefore,it is necessary to develop a fault diagnostic system for the power system of Electric Vehicles.Firstly,this paper elaborated the global energy and environment problems,and introduced the development and research status of Electric Vehicles at home and aboard.It also analyzed the development and research status of fault diagnostic technology for Electric Vehicles at home and abroad.Then,according to the general structure of power system of Electric Vehicles and special features of the vehicle(using EMT transmission system),the working principle and control strategy of each subsystem(power battery,power motor,and transmission)in the power system of this Electric Vehicle were discussed.Combined with actual test of real vehicle,the failure and causes of each subsystem were analyzed in this paper.Also,some fault maintenance scheme are proposed.It provide the basis for the following designed diagnostic software.Secondly,this paper analyzed the protocol stack of UDS protocol based on CAN bus,and introduced the advantages of the network architecture.It analyzed the types of messages on CAN bus,and focused on the analysis of data unit,timing management and timeout processing for the network layer protocol(ISO15765-2)on CAN bus,and also analyzed diagnostic service units,timing management and timeout processing of the application layer protocol(ISO15765-3,ISO14229-1).Finally,the design of the fault diagnostic software on PC terminal for the power system of the tested vehicle and the design of the fault simulation system based on CANoe were introduced in detail.Through the experimental debugging of the complete fault simulation system,the semi-physical and semi-simulated fault system,and the real vehicle test,the functional validity and reliability of the fault diagnostic software on PC terminal are verified.