Research On Shielding Technology Of Engine Electronic Control System

With the development of pulse power technology and antenna technology,a variety of electromagnetic pulse sources,such as high-power microwave source and nuclear magnetic pulse source,are constantly emerging,and automotive electronic equipment is becoming more and more rich and integrated.The protection of external electromagnetic interference has become a problem of concern,especially the engine electronic control system,as the most core part of the vehicle,determines the safe operation of the vehicle Driving problem,in order to make the car work normally and safely,the electromagnetic protection of the engine can not be ignored.For the engine electronic control system,the electromagnetic interference is usually coupled through the back door such as slot and cable.Therefore,the research on the protection of holes and cables has theoretical significance for the protection design of engine electronic control system.General electronic equipment,especially highly integrated control equipment,will be protected by metal shell.However,the small holes and gaps caused by heat dissipation may also bring the enhancement effect of coupling field,which poses a serious threat to the electronic devices in the cavity.Based on the transmission line matrix method,the electromagnetic coupling characteristics of metal cavities with holes and slots are studied systematically.Aiming at three different types of intense electromagnetic pulse,the simulation models of different sizes of slots and cavities are established respectively.The coupling field inside the metal cavity with slots under the action of intense electromagnetic pulse is obtained by calculation.The coupling characteristics of the cavity under the action of different intense electromagnetic pulse are compared and analyzed,and the influence of slot width length ratio on the time-domain shielding effectiveness and main frequency component of the cavity is explained.On this basis,the interaction mechanism between metal cavity with holes and three different types of intense electromagnetic pulses is discussed.It is found that the mechanism of interaction between a metal cavity with a slot and a strong EMP is the response of the resonant mode of the cavity and the resonant frequency of the slot to the strong EMP.When the resonant mode(including high-order mode)and the resonant frequency of the slot are in the strong electromagnetic pulse band,the coupling field inside the cavity is very strong,even the enhancement effect appears,which poses a serious threat to the internal electronic equipment.At the same time,due to the lowest shielding effectiveness of vertical incidence and polarization matching,when designing metal shield for electronic equipment,we should try to avoid being directly exposed by the strong electromagnetic pulse.At the same time,based on the strong electromagnetic pulse frequency band,we should suppress the cavity resonance mode and slot resonance frequency in the band to improve its protection performance.On the other hand,there are many kinds of cables inside the engine,so it is difficult to simulate the whole model of the engine cable,whether in technology or computing memory.So this paper studies the simplified modeling method of the automobile wiring harness,and analyzes the simulation results in detail The " Equivalent cable bundle method " simplifies and tests the model with coaxial line and multiple single core wires on the infinite conductive plane under the irradiation of various high power pulses.The classification method of wiring harness is given,which simplifies the calculation of unit parameter matrix of wiring harness,the calculation of geometric parameters of cross section of wiring harness after simplification,and the calculation formula of equivalent connection parameters of wiring harness after simplification.By comparing the load current before and after simplification,the simplified modeling of two different types of cables on infinite conductive plane is realized.In addition,a simplified modeling method is proposed to split the coaxial line into two single core wires for various types of cylindrical shielding cavity conductors,and the detailed modeling process is also given.Through the comparison of load current before and after the simplification,it is verified that although the resonant frequency and curve similarity of current in each core wire are almost the same,and the current amplitude is the same at some resonance points before and after the simplification,the whole power is on There is a great difference in the flow amplitude.Through the simplified modeling of wire harness,the calculation time is greatly reduced while ensuring the accuracy.However,the shielding cavity model needs to be further improved.