| Subway is an important means of transportation in modern cities Because of its high speed and high density of people,once there is an accident,it will cause great loss of life and property In recent years,with the rapid growth of subway mileage in China,the safety problems of subway tunnels are becoming increasingly serious.There are many problems in manual detection,such as low efficiency,high cost,and high labor intensity in night detection.The existing machine detection cannot meet the requirements in speed.In this paper,3D laser line scanning measurement technology is applied to tunnel geometry detection,and a prototype of 3D laser line tunnel detection is designed and implemented SystemAt present,most of the existing tunnel detection equipment adopts the laser point measurement technology,and the measurement speed can not meet the actual application demand This paper compares and analyzes the laser point measurement technology and laser line measurement technology,and designs the subway tunnel detection system based on the laser line measurement technology.The system mainly consists of the measurement vehicle and laser line scanner,and adopts the photoelectric encoder and ten axis The sensors collect and measure the moving mileage and attitude of the car in real time.During the detection,the car moves along the track.Eight high-powered digital cameras collect the surface shape of the subway tunnel in real time.The main achievements are as follows(1)Based on the laser line scanning measurement technology,the hardware module and software module of the subway tunnel detection system are designed,and the main components such as laser,camera,photoelectric encoder and angle sensor are selected.According to the requirements of tunnel measurement,the camera imaging parameters are designed,and the scanner bracket,camera calibration target,simulation tunnel and other accessories are designed and manufactured;(2)The pulse reading of photoelectric encoder is realized by stm32f103zet6 development board serial port programming.The trajectory and attitude of trolley are calculated by the pulse of photoelectric encoder and the reading of ten axis sensor,and the calculated trajectory is compared with the manual measurement trajectory;(3)Using the dot graph as the calibration target,the algorithm of circle center extraction,row line and column line automatic recognition is designed and realized,and the error between the fitting grid and the circle center is analyzed;(4)The gray distribution of laser line image is analyzed,the algorithm of extracting the center of light band based on floating threshold is realized,and the algorithm of transforming image point coordinates into spatial coordinates based on the principle of constant cross ratio is given.The three-dimensional laser line tunnel detection prototype system developed in this paper has been tested in Shanghai Metro Line 7 and line 8,which verifies the technical scheme designed in this paper,and the main technical indicators meet the design requirements,Compared with the laser point detection system that collects 1 million points per second,the system in this paper collects 4.25 million points per second.The speed of the laser point detection system that collects 1 million points per second is only 0.85km/h according to the sampling interval of 2mm.The system detection speed in this paper reaches 3.6km/h.In terms of measurement principle,the excitation line measurement technology has a larger lifting space and can meet the needs of metro tunnel geometry detection,It has a good application prospect in ensuring the safe operation of subway. |
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