Research On 3D Reconstruction Algorithm Of Expansion Joint Based On Laser Scanning

As a kind of expansion joint can be absorbed by thermal expansion and contraction caused by the deformation of the elastic element,expansion joints can improve the reliability and safety of pipeline transportation,which have been widely used.However,at present,the change of wave shape before and after the expansion joint test in China is still in the stage of eye observation and manual measurement.The traditional detection methods have the disadvantages of low efficiency,poor precision and great labor intensity.Therefore,an inverse three-dimensional reconstruction technique which can directly reflect the waveform change before and after the expansion joint test is urgently needed,and the wave distance value of waveform is given.In recent years,with the rapid development of science and technology,laser scanners are widely used in surveying and mapping,distance measurement,point cloud data collection,and other industries,have speed is quick,convenient storage and computation flexible,high precision.In this paper,in view of the shortcomings of the traditional detection of expansion joints,the Canadian LMI line laser scanning measurement technology is applied to collect the point cloud data of the expansion joint waveform.A three-dimensional reconstruction algorithm based on the laser scanner is proposed.Based on the algorithm and the OpenGL technology,a software system for observation,easy operation and friendly interface has been developed.The system is conducive to improving the speed,accuracy and automation level of the expansion joint waveform detection device,and is of great significance for the popularization of the expansion joint detection device.The main work is as follows:1.Point cloud data processing of the expansion joint.In the process of laser point cloud data acquisition,due to the influence of the surrounding environment,the precision of the instrument and the position of placement,the point cloud data of the expansion joint may have problems such as abnormal point,noise point and gradient point.Therefore,in view of the characteristics of point cloud data of the expansion joint,this paper discusses the method of cloud data processing of expansion joint in detail,to ensures the accuracy and authenticity of the three-dimensional reconstruction of expansion joints.2.The curve fitting of the expansion joint waveform and the calculation of wave distance value.The traditional measurement of wave distance of expansion joint is manually measured by observation of human eye and vernier caliper.The accuracy of this method is not high,and the randomness is large.In this paper,according to the point cloud data of the wave collected by the laser scanner,the B spline is used to fit the wave curve of the expansion joint.The wave distance value of the expansion joint is accurately calculated by the curvature,thus ensuring the reliability and accuracy of the wave distance data.3.Spatial coordinate transformation of point cloud data of the expansion joint.This paper uses point cloud data of the expansion joint collected by line laser scanner.The data only contain depth information and interval information between points.If we want to get the point cloud data in the three-dimensional space of expansion joints,we need to transform the combination of line point cloud data into spatial coordinate point cloud data.According to the characteristics of point cloud data,the method of point cloud data combination is used to achieve the purpose of spatial coordinate transformation of point cloud data.4.The three-dimensional reconstruction of the expansion joint.According to the point cloud data of three-dimensional space of the expansion joint,this paper constructs the node vector of the expansion joint.Then,NURBS method is used to reconstruct 3D surface of the point cloud data of the expansion joint and combined with OpenGL to realize 3D reconstruction of expansion joint.The reverse 3D reconstruction of expansion joint can reflect the overall variation of the waveform before and after expansion joint test accurately,comprehensively and quickly.