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With China's highway transportation industry, the rapid development of the high rate of traffic accidents , traffic safety become increasingly important social issues , has aroused widespread concern. Development of intelligent transport systems and intelligent vehicle technology to solve our problem of effective traffic safety measures . This article discusses the world's intelligent transportation systems and intelligent vehicle technologies in the application of automatic crash situation, combined with China's highway situation , driving habits and existing sensor technology , designed in line with China 's national conditions of the vehicle longitudinal collision avoidance warning system , its purpose : in critical situations , alarm , alert the driver , so that there is a certain pretreatment time , thereby avoiding driver fatigue , negligence, accidents caused by misjudgment , proactive protection of traffic safety purposes. The basic working principle is : the use of detection equipment to accurately measure the distance between the front of the obstacle , and quickly back to the car micro-processing systems, micro-processing system through the operation , compare, and then make a judgment , such as reaching a dangerous speed, distance, start the alarm device , using the form of voice and light alarm . In the process of developing this system , depending on the operating conditions , more in-depth study of the distance and the braking distance alarm situation , the establishment of an alarm from the model and the braking distance model ; Then, depending on the basic functions to be achieved , the design of the system programs, and on this basis, select the system power supply design information collection, alarm signal output, and other devices in the application circuit ; MCS-51 assembly language with the preparation of the system control program ; Finally, we use a PC analog signal inputs , the use of lights and sound the alarm , obtained simulation results . Experimental results show that a vehicle speed signal input , the alarm safe braking distance is longer than the distance , the alarm can be realized in different ways . Hardware and software matches the system is stable .
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