| In recent years,each big city's subway construction pace is accelerating,the subway tunnel safety accidents occur from time to time,establishing a sound of metro tunnel construction real-time monitoring system,to access the tunnel for exact location and other information of construction site and to reduce the loss of the accident is of important significance.According to the requirement of safety construction management of subway tunnel,combined with the characteristics of electromagnetic wave propagation in tunnel,this thesis studies the technology of tunnel personnel positioning based on RSSI.The main research contents are as follows:(1)Principals of several common techniques used in wireless positioning has been introduced,including WiFi positioning technology,ZigBee positioning technology,infrared positioning technology,Bluetooth positioning technology,as well as ultrasonic positioning technology,etc.In addition,the nature of TOA,TDOA,AOA and RSSI algorithm has been explained.Through analyzing of the combination of the simplicity,cost of system comprehensively,the RSSI algorithm based on WiFi had been adopted.(2)The first step of adopting the RSSI algorithm to position the tunnel officer is to establish the model of the propagation attenuation model for WiFi signal.The method of physical optics(PO)had been adopted,simulating by the FEKO,the WiFi signal attenuation model following the change of distance between the antenna and the wall of tunnel has been analyzed.(3)According to the simulation model analysis results,through the experiment,it is analyzed that the base station antenna from the tunnel wall at different distance tunnel WiFi signal propagation attenuation model experiment,the relationship between expression of RSSI and the propagation distance is established.The influence of the distance between the base station and the tunnel wall on the attenuation model is analyzed,and the implementation scheme of the base station is determined by comparing the suitable location and positioning system.(4)Based on the simulation and experiment,the positioning system for the Metro tunnel officer adopted on WiFi technique and RSSI algorithm had been developed.The whole system can be divided into three parts including positioning node,base station and upper computer.And the test had been taken in the tunnel of the sixth line of Wuhan Metro in Changqing Garden.The test result had satisfied the customer. |
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