Vehicle Safety Localization And Monitoring In Tunnel Using Spread Spectrum Communication

The rapid development of highway tunnels has greatly improved the current situation of highway traffic environment in China,but it also brings a series of problems.With the increase of the number of tunnels,traffic accidents in tunnels are also increasing.Tunnel accidents not only cause casualties,vehicle damage and economic damage,but also cause serious negative impacts.Because GPS and other positioning systems lose their positioning function in tunnels and can not locate and monitor vehicles in time,the traditional positioning system can not meet the current safety system requirements in tunnels.Therefore,it is necessary to study a technology that can monitor the position and operation status of vehicles in tunnels.This paper focuses on the safety positioning and monitoring technology of tunnel based on spread spectrum communication tunnels,mainly doing the following work:(1)Introduce the related theories of wireless sensor networks,including definition,composition,structure and characteristics.Analyze wireless positioning technology,including related concepts and technical classification of positioning technology.The positioning algorithms based on ranging mainly include RSSI,TDOA,AO A and TO A.The non-ranging based localization algorithms mainly include DV hop,centroid algorithm and weighted centroid algorithm,and the evaluation of positioning mechanism and positioning performance are introduced.The theory of spread spectrum communication technology is introduced,including the type of spread spectrum technology and related.Performance indicators,as well as the characteristics of frequency hopping spread spectrum;(2)The field strength-distance model of the conductive magnetic wave is transmitted in free space,and the model is fitted by experiment.The error is corrected by least squares method.The signal is processed by fast Fourier transform.The resulting spectrum leakage problem is studied and processed,and the interpolation method is used for correction.In the process of signal acquisition,two methods are designed.One is based on the hardware processing,and the strength value of the signal is directly measured by the hardware device;the other is the signal wave through another hardware,the acquisition board and the PC end.Processing to obtain an accurate signal;(3)An improved positioning algorithm is proposed,which mainly includes weighted centroid localization algorithm and improved weighted centroid localization algorithm,and simulates the positioning algorithm.The overall architecture of tunnel vehicle positioning safety and monitoring system is designed,including structural function design and monitoring decision system.The design of the roadside unit layout;at the same time,the selection and design of the modules required for the construction of the hardware platform;finally,the workflow of the vehicle unit and the roadside unit is designed.The tunnel vehicle positioning safety and monitoring system designed in this paper starts from the perspective of vehicle road information interaction,vehicle position monitoring and operation status monitoring,realizes vehicle communication and maintains vehicle monitoring in real time,and plans the operation of the vehicle through monitoring and decision-making.It realizes no blind spots and high reliability monitoring and warning for vehicles in the tunnel.