Study On Communication Performance And Electromagnetic Interference Problems Of In-vehicle CAN-Bus Network

Electronic control units are connected to the vehicle controller via CAN Bus inthe electric vehicle. The motor drive system and the DC/DC converter are the majorinterference sources inside the car. Due to the bundled wiring harness, including thecontrol lines of CAN controller, the electromagnetic interference (EMI) generated bythe prementioned interference source can impact the CAN-bus transmission line. Inorder to study the impact of the interior EMI on the CAN-bus, it is necessary to studythe communication performance and EMI problems of CAN-bus first. This thesissupported by the National Natural Science Foundation of China," EMC basic research，the electromagnetic environment analysis and optimization in the high voltage systemsof electric vehicle "（No51177183）,studies on the communication performance andproblems related to electromagnetic interference of in-vehicle CAN Bus, the mainresearch contents are as following:①Give a brief introduction and analysis of basic norms of CAN-bus, includinglayered structure、message type and communication mechanism etc. Have a goodunderstanding of the communication mechanism of CAN-bus on this basis. The thesisputs forward a simple method of building a CAN-bus node communication netwrok inMatlab using Simulink blocks. The designed communication model reflects thetransfer conditions of CAN-bus, and achieves the function of communication betweenelectronic nodes. The simulation results show that this model can be used as the busperformance analysis tool. The thsis also does some simple researches on the randomanalysis of message response time.②Compare the impact on harness crosstalk of unshielded twisted pair cables andshielded twisted pair cables, using simulation meathod, by analyzing the scatteringparameters. And discuss the crosstalk between single line and twisted pair cable on thebasis of studying the multi-conductor transmission line theory and theroy of crosstalk.Then verify the feasibility of using cascade transmission line model to calculate thetwisted-pair crosstalk by comparing the calculation and simulation result of thetwisted-pair crosstalk.③This thesis provides a preventive method against unauthorized datatransmission problems which may arise during the CAN-bus communication process.The characteristic of this method is that it’s possible to prevent the ECU from receiving unauthorized data frame. ECU is able to detect any unauthorized data frame andcovering unauthorized data frame with a frame error by using the method. So far, verylittle research on the prevention of unauthorized data transfers supported by traditionalsecurity mechanisms. It can be found out that the method is effective to preventunauthorized transmission, by comparison with other protection methods. It can alsoachieve sufficient real-time response and enhance the security of the CAN buscommunication.