Research On Prediction Of Crosstalk And Its Dynamic Characteristics In Automotive Wiring Harness

With the development of the automotive electronics, a growing number of electrical and electronics equipments are applied to automotive to improve the safety, comfort and controllability. As the network subject of automotive circuit, the automotive wiring harness which is distributed throughout the automotive chassis and body is used as the power line and signal transmission line of the device and connects various electrical and electronics equipments. However, due to the increase of automotive electrical and electronics equipments, electromagnetic compatibility of automotive inner has become more and more complex and adverse. As the most serious electromagnetic interference problem of automotive, crosstalk in automotive wiring harnesses appears and the crosstalk transmits to electrical and electronic equipments of automobile by the wiring harness, which has an effect on the device and leads to the severe decline of electromagnetic compatibility. At the initial design of automotive electromagnetic compatibility, researchers must make accurate and reasonable predictions on crosstalk in automotive wiring harnesses to ensure the safety and reliability of the automotive and avoid making modifications in the latter production of automotive owing to electromagnetic compatibility problems. Based on these predictions, researchers are capable of shortening the development cycle and saving development cost of automotive. This paper is supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China “Study on the electromagnetic compatibility of automotive based on random statistical technology”( NO.20110061110059) and it emphasizes on exploratory study about EMC simulation and prediction of wiring harness crosstalk in automotive.Further study is conducted on EMC simulation and prediction problems in this paper, such as the acquisition of the per unit length distribution parameter matrices in the automotive wiring harnesses, time-domain transient response of crosstalk in automotive wiring harness, instant prediction on automotive wiring harness by artificial neural networks, quantitative analysis of various influential factors of crosstalk in automotive wiring harness and dynamic characteristics prediction on crosstalk in automotive wiring harness when the geometric location is not fixed.Maxwell equations are used to deduce the multiconductor transmission lines equation and then the physical significance of per unit length distribution parameter matries are explained. Automotive wiring harness is regarded as the ideal lossless multiconductor transmission lines equations. According to the examples about the homogeneity of surrounding medium around wires, it can discuss and understand the application scope of Analytical Method, Method of Moments and Finite Element Method in the aspect of solving per unit length inductance matrix and per unit length capacitance matrix, which can be the basis on calculation of the per unit length distribution parameter matries in automotive wiring harnesses.Finite Difference Time Domain method is a classical numerical method for solving the multiconductor transmission lines equation. Using the traditional Finite Difference Time Domain method to conduct time-domain transient response of automotive wiring harness crosstalk,due to the limitation of the difference scheme, it will yield strong non-physical oscillations after discontinuous solution, which has some impact on the calculation results. Meanwhile, the computational efficiency is not high owing to the limitation of stability conditions. To solve this problem, a Finite-Difference Time-Domain method with implicit Wendroff difference scheme is proposed in this paper and it will be applied to conduct time-domain transient response of crosstalk in automotive wiring harness. Because this method contains implicit artificial viscosity term, it can weaken non-physical oscillations at discontinuous solutions caused by the discretization of spatial coordinates, which can improve the accuracy of the calculation results. At the same time, without being restricted by stability conditions, computation efficiency will has a significant improvement. Take non-uniform double-conductor transmission lines system and uniform three-conductor transmission lines system as examples to analyze time-domain transient response of the crosstalk. Compared simulation results of this method with the simulation results of traditional Leapfrog difference scheme and Lax-Wendroff difference scheme, it can be verified that Finite Difference Time Domain with implicit Wendroff difference scheme is more accurate and efficient in aspect of conducting time-domain transient response of crosstalk in automotive wiring harness.With the increase of electrical and electronic equipments in automotive, the kinds and quantity of the wiring harnesses grow rapidly. However, the computation efficiency of traditional calculation method such as Finite Difference Time Domain, Finite Element Method and Method of Moments is not high when analyzing the crosstalk in automotive wiring harness. At the same time, it may not have general applicability because of the limitation by conditions, so these methods have not been suitable for calculating complex the crosstalk in automotive wiring harness. In this paper, a kind of prediction model about crosstalk in automotive wiring harness based on GA-BP neural network is proposed, it can not only quickly predict crosstalk in automotive wiring harness, but also has broader scope of application. In the meanwhile, it takes advantage of weight algorithm to make a quantitative analysis about the impact of eight input parameters on crosstalk in automotive wiring harness including the length of automotive wiring harness, frequency, wire-to-ground height, excitation voltage, relative permittivity of insulating layer medium, relative distance in the wires, conductor radius of the wire, thickness of the insulating layer and it also simplifies the prediction model under the premise of guaranteeing calculation precision and calculation efficiency, which has an edificatory significance to the electromagnetic compatibility design of automotive wiring harness wires.Combine equations of three-conductor transmission line expressed by sine steady-state form with boundary conditions, deduce frequency-domain uncertainty analytical expressions of crosstalk in automotive wiring harness, and conduct analysis about the impacts of some factors on the crosstalk in automotive wiring harness, such as automotive wiring harness terminals with loads, wire-to-ground height and the relative distance between the wires, and then draw the qualitative conclusion. Aimed at the uncertain spatial location in automotive wiring harness, the present Random Displacement Spline Interpolation Method which is used to analyze dynamic characteristics of crosstalk in automotive wiring harness will be modified, in order to make it change from the traditional algorithm which only considers relative distance between wires to dynamic characteristics prediction method of crosstalk in automotive wiring harness which considers both automotive wiring harness on height and relative distance between wires. At the same time, a kind of dynamic characteristic prediction model of crosstalk in automotive wiring harness based on statistical methods is proposed, which considers both automotive wiring harness on height and relative distance between wires. Take the actual 7-pin automotive wiring harness model for example, it predicts the reasonable worst case of crosstalk in automotive wiring harness and probability density function and compares the prediction results with the modified Random Displacement Spline Interpolation method. The result turns out that the model proposed in this paper can be applied to predict dynamic characteristics of crosstalk in automotive wiring harness, which provides scientific basis for the design of automotive electromagnetic compatibility.