Analysis Of Automotive Wiring Harness Equivalent Model And Its Application In Electromagnetic Compatibility Simulation

With the development of the electronic and intelligent technology, auto electronic equipments are increasing rapidly. For the electronic devices in the automotive electrical network varying, the wiring harness plays an important role. Without it, there are no electronic and intelligent autos. Meanwhile, the increase of electronic equipments worsens the auto electromagnetic environment. Especially with the wiring harness growing in number, the automotive electromagnetic compatibility (EMC) becomes more serious. Therefore, in order to ensure vehicle safety and reliability, setting up automotive wiring harness model for EMC simulation become significant whether in theoretical field or in engineering research field.This thesis, supported by the National Natural Science Foundation of China,"Automotive EMC forecast and key technologies for electromagnetic interference suppression"(No.50877081) and Chongqing Natural Science Foundation of China,"Electromagnetic Compatibility for Automotive Electrical System"(No.CSTC, 2006BA6015), focuses on the emulation methods of automotive wiring harness and experimental verification.In the course of this research, the thesis uses the electromagnetic theory, circuit theory, and EMC technology theory and testing method. The aspects concerned are as follows:①Deduce Multi-conductor transmission line equation from Maxwell fundamental equations in details and explains the physical meaning of capacitance matrix elements, and discuss the analytical and numerical methods of multi-conductor transmission line unit length inductance and capacitance matrix. These are the foundations for calculating the automotive wiring harness multi-conductor transmission line inductance matrix and capacitance matrix.②Propose the principle of equivalent impedance defined the electromagnetic characteristics of the multi-conductor transmission line. Then, the equivalent impedance formula is deduced. According to the size of the terminal impedance and the equivalent impedance, the wiring harness can be classified in different groups. This approach greatly simplifies the wiring harness modeling by making the multi-conductor transmission lines reduce to four groups mostly. The equivalent methods of calculating differential-mode load, the common-mode load and the source are obtained. Establish the equivalent model by the circuit for the wiring harness efficient simulation.③The induced current by the plane incident wave is calculated from the electromagnetic wave theory. Analyze the coupling modes which can produce the induced current. Verify the effectiveness of the finite element method (FEM) in calculating the induced current. Discuss the terminal load, terminal structures and the dielectric effect in the induce current. Taking the wiring harness consisting of nine conductors for example, the whole process of establishing the equivalent model for electromagnetic radiation (EMR) sensitivity is described in details. The emulation results show that the wiring harness equivalent model can save computing resources under accuracy condition. The experiment which is carried out in the semi-anechoic chamber validates the correctness of the equivalent model for EMR sensitivity emulation.④Establish the simple wire radiation emission model based on the antenna theory. Verify the effectiveness of the FEM to calculate the electric field strength, the magnetic field strength, and the total power of radiation around the wire. Discuss the terminal load, terminal structures and the dielectric effect in the EMR emission. Taking the wiring harness consisting of 12 conductors for example, the whole process of establishing the equivalent model for EMR emission is described in details. The example proves that the conductor can be classified flexibly if its terminal load is equal to the equivalent impedance, and it also illustrates that the wiring harness equivalent model can save computing resources under accuracy condition. The experiment validates the correctness of the equivalent model for EMR emission emulation.⑤Based on the analysis of the ignition system conducted electromagnetic interference (EMI), it is drawn conclusion that the radiated EMI of the ignition system is come from the current flowing through ignition coil primary side which acts as an antenna in this situation. Thereby, the EMR emission model of the ignition system is established. The process of building the vehicle body FEM model in HFSS software for EMC forecast is introduced. The experiment certificates the model. The induced current in the vehicle wiring harness generated by ignition system EMR emission is simulated using the equivalent model, and it shows that the equivalent model can be used in automotive wiring harness for EMC analysis.⑥Establish a harness network according to the size of the chassis. The harness network equivalent model is built by the wiring harness equivalent model. The emulation results show that the equivalent model can be used to the complex structure harness network. Under the accuracy condition, it can reduce the computation time, computer memory greatly.