Research On Electromagnetic Protection Technology Of Advanced Driving Assistance System

The advanced driving assistance system is a kind of active safety technology that can enable the driver to detect the potential safety hazards in advance by sensing the dynamic information of the surrounding environment and identifying,detecting and tracking static and dynamic objects through a variety of sensing devices installed on the vehicle.With the continuous development of automotive information and intelligence,advanced driving assistance system has become an important link to ensure vehicle driving safety.At the same time,the complex electromagnetic environment interference of the system is becoming more and more obvious.On the one hand,more and more electronic devices in the vehicle interfere with the advanced driving assistance system more and more seriously.On the other hand,the continuous development of man-made strong electromagnetic pulse poses a severe challenge to the safety of advanced driving assistance system.The research on electromagnetic protection technology of advanced driving assistance system has positive significance and value for vehicle driving safety.This paper takes the sensing equipment,conduction harness and central control unit of advanced driving assistance system as the research object,and analyzes the electromagnetic coupling mechanism of advanced driving assistance system.The protection method of 24GHz millimeter wave radar in sensing equipment is studied.Bandpass frequency selective surface and energy selective surface with cross,square and circular aperture are designed,and the radiation characteristics and shielding efficiency are verified respectively.The crosstalk between the conductor bundles and the interference of the coupling between the conductor bundles under the irradiation of strong electromagnetic pulse are analyzed.It is verified that the crosstalk and radiation coupling interference between the conductor bundles can be effectively reduced by adding a shielding layer to the harness.The electromagnetic protection methods of central control unit cooling hole and optical window are analyzed.Through the electromagnetic protection of the weak links of advanced driving assistance system,the stability of the system in complex electromagnetic environment can be effectively improved.The main research contents are as follows:（1）Electromagnetic protection technology for sensing equipment of advanced driving assistance system.Focus on the vehicle mounted 24GHz millimeter wave radar,and complete the modeling of microstrip patch array antenna,radome and radar shell according to its structure,characteristics and material.The bandpass frequency selective surfaces with cross,square and circular apertures are designed,and the radiation characteristics of the three structural frequency selective surfaces are analyzed.Among them,the cross aperture frequency selective surface can ensure the trafficability in the 24GHz frequency band and effectively protect the strong electromagnetic pulse outside the working frequency band.Based on the frequency selective surface of the three structures,the energy selective surface is designed by bridging PIN diodes.The radiation characteristics of the three structures when bridging 4,8 and 16 PIN diodes are analyzed.It is verified that when the strong electromagnetic pulse exceeds the safety threshold,the energy selective surface realizes the function of protecting the strong electromagnetic pulse by moving the harmonic frequency.（2）Electromagnetic protection technology of conduction harness of advanced driving assistance system.By establishing the simulation model of the transmission wire harness of the vehicle driving assistance system in the vehicle electromagnetic environment,the crosstalk between the transmission wire bundles of the driving assistance system and the interference of the coupling of the transmission wire harness under hemp irradiation are simulated and analyzed.By simulating the influence law of the distance,included angle,coupling length and other variables between the two wires on the crosstalk between the wires,this paper puts forward a reference for reducing the crosstalk between the transmission wire bundles of the driving assistance system.The crosstalk between wire harnesses can be reduced to a certain extent by adjusting the layout between wire harnesses.In order to further reduce the crosstalk between harnesses,the single wire,twisted pair and super five twisted pair harnesses that are vulnerable to crosstalk are shielded.After adding the shielding layer,the cable crosstalk is significantly reduced,and the peak value of the most serious crosstalk voltage is less than 9×10^-6v,almost negligible.By simulating the coupling interference signal of the conduction harness of the driving assistance system under the incidence of hemp with different incidence angles and polarization directions,it is concluded that the incidence angle and the polarization direction of the electric field will have a great impact on the coupling interference of the harness,and this consideration should not be ignored in the layout of the harness.Shielding is the most effective means of strong electromagnetic pulse protection.By shielding single wire,twisted pair and super five twisted pair,the coupling interference voltage of the harness is significantly reduced,indicating that the protective measure has achieved good shielding effect.（3）Electromagnetic protection technology of central control unit of advanced driving assistance system.According to the actual size and material of the central control unit,three-dimensional modeling is carried out,focusing on the electromagnetic protection methods of weak links such as cooling holes and optical windows.By studying the relationship between the cooling hole and electromagnetic leakage from the two aspects of the size and periodic distance of the cooling hole,the electromagnetic leakage caused by the cooling hole can be effectively reduced by reducing the area of a single cooling hole and increasing the periodic distance of the cooling hole.For optical windows,metal grid and conductive film can be used for electromagnetic protection of optical windows.Compared with ordinary optical windows,it can effectively improve the electromagnetic protection ability while ensuring good light transmittance.Contribution and innovation are as follows:（1）The strong electromagnetic pulse protection technology of vehicle mounted24GHz millimeter wave radar based on frequency selective surface and energy selective surface is proposed.The bandpass frequency selective surface with cross aperture,square aperture and circular aperture is designed.The cross aperture frequency selective surface can ensure the trafficability in the 24GHz frequency band and effectively protect the strong electromagnetic pulse outside the working frequency band.Based on the frequency selection surface,the energy selection surface can be constructed by bridging the pin diode.The frequency shift of the energy selection surface will occur when the pin diode starts working,and the resonant frequency shift degree of the energy selection surface will gradually increase with the increase of the number of PIN diodes.Therefore,when designing the energy selection surface,the number and position of PIN diodes can be selected according to the bandwidth of strong electromagnetic pulse and the specific working frequency of the protected object,and the expected effect can be achieved through optimization.（2）The technical methods to reduce the crosstalk between transmission wire bundles and the coupling interference of transmission wire bundles under the irradiation of strong electromagnetic pulse are proposed.By adjusting the layout of the conductor bundle,the crosstalk between the harnesses can be reduced to a certain extent.The maximum peak value of the cable crosstalk voltage after adding the shielding layer to the conductor bundle is less than 9×10^-6v,almost negligible.Shielding is the most effective means of strong electromagnetic pulse protection.Under the irradiation of strong electromagnetic pulse,the coupling interference voltage of harness is significantly reduced by shielding single wire,twisted pair and super five twisted pair.