Study On Key Technologies Of Target Vehicle For Active Safety Testing

With the significant increase of car ownership in China,roads have become far more crowded,road traffic accidents have increased dramatically,and car safety issues are getting worse.Vehicle active safety technologies can predict and mitigate risk of collision by warning the driver before it’ s coming too late and even actively braking the vehicle to avoid a crash.Therefore,it is needed to test and evaluate the vehicle active safety system.For target vehicle of automotive active safety testing,some key technologies such as radar target range and distance measurement system,wireless channel characteristics of between vehicles under special terrain environment and vehicle target absorbing devices are studied.The main contents of the dissertation can be summarized as follows:Firstly,in order to accurately detect target vehicle,simulation and analysis of radar cross section(RCS)of typical automotive model is firstly conducted.Based on SystemVue system-level simulation platform,a short-range LFM(Linear Frequency Modulation)and a long-distance FMCW(Frequency Modulated Continuous Wave)anti-collision radar system utilizing commonly-used millimeter-wave radar sensors of 24 GHz and 77 GHz are constructed respectively in this thesis.Radar system signals in ideal and noise contained FMCW environment are analyzed.Multiple sets of real distance/velocity values are measured and measurement error of distance and velocity are within ± 0.8 m and ± 0.4 m/s,respectively,meeting distance and velocity resolution requirements.Secondly,combined with the unique terrain of Chongqing,the surrounding area of the Jiefangbei business circle is selected and accurately modeled to investigate wireless channel characteristics of vehicle-to-vehicle(V2V)in urban environment.The multi-path delay dispersion parameters of static target and wireless channel characteristics such as path loss and average delay spread of moving target vehicle are simulated and analyzed.In addition,the influence on wireless channel characteristics of various wall building materials with different relative permittivity is also discussed.It is found that the larger the relative permittivity of the building material is,the larger reflection gain,RMS delay spread and path loss are.Finally,the absorbing structure of the simulated target vehicle is studied and optimized.A multi-band ultra-thin metamaterial absorber is designed by using artificial electromagnetic metamaterial technology.Starting from the design of a three-band absorber,conducting numerical analysis and experimental measurements,99.95%,99.28% and 96.36% absorption efficiencies are acquired at 8.15 GHz,11.4 GHz and 15.12 GHz resonance frequencies,respectively.It is demonstrated that the metamaterial absorber is insensitive to incident wave polarization angles and with perfect absorption characteristic under wide oblique incident angles in TE and TM modes.The electric field,magnetic field and surface current distributions at resonance frequencies have been analyzed for providing insight of the absorption mechanism of the proposed structure,that is,the existence of electric and magnetic mutual coupling.Moreover,the influence of the geometric parameters and different resonance patterns on the absorbing performance are discussed and analyzed.More importantly,a four-band absorber can be realized by adjusting structural parameters of the triple-band absorber.Through numerical analysis and geometric parameter discussion,it is illuminated that the four-band absorber can maintain high-efficiency absorption stability under different normal incident wave polarization states and wide oblique incident wave angles.