ADAS Research Of Foggy Sky Expressway Based On High Precision Beidou System

The safe driving problem in the foggy environment has become a bottleneck that restricting the full utilization of expressway function.At present,for dense fog weather,the management department mainly adopts measures to close the expressway to ensure safety,but in fact,the accident is only transferred to other roads.Based on the analysis of the development trend of global satellite navigation system,high-precision electronic map and vehicle-borne network communication technology,this paper studies the ADAS based on high-precision Beidou system.According to the multi-lane driving scheme of the foggy highway,key issues such as lane-level positioning technology and early warning strategy of fog-sky driving are explored.The main research contents and results of this paper are as follows:(1)Combining the development trend of centimeter-level BDS positioning technology,high-precision electronic map and vehicle-borne network communication technology,the overall scheme of vehicle ADAS on fog-sky expressway is designed,the vehicle positioning module and the IEEE WAVE communication protocol adopted by ADAS are determined,and the vehicle driving warning rules and the determination method of vehicle safe distance based on multi-lane driving on fog-sky expressway are designed.(2)Aiming at the requirement of multi-lane vehicle traffic in foggy weather on expressway,the key elements of BDS positioning accuracy and high-precision electronic map in lane-level positioning technology are analyzed.The method of cubic spline curve fitting for lane-level map is studied.Based on high-precision electronic map and centimeter-level BDS positioning technology,a real-time vehicle lane recognition method based on successive approximation method is proposed.(3)The hardware system of vehicle-mounted unit is designed and developed,which mainly includes the minimum system module with STM32F103 as control chip,Beidou positioning and navigation module,vehicle wireless data receiving and sending module,human-computer interaction module and other auxiliary modules.(4)The software program of auxiliary driving system for foggy sky expressway is developed.Based on C language and Keil MDK programming software,the initialization function of system operation,Beidou data receiving subroutine,wireless network data receiving subroutine and sending subroutine,calculation of safety distance parameter and judgment procedure of early warning decision conditions are edited by using library function programming method.(5)The performance measurements and analysis of the system network are carried out,and the vehicle wireless network communication performance experiment is designed from two aspects of network delay and throughput.The experimental results show that the network performance of the system is stable under the traffic environment of foggy sky expressway.The efficient communication with low delay below 30 ms and high data throughput above 550kb/s within 300 m communication distance can guarantee quick and efficient transmission and reception of vehicle driving status information.