Research On The Three-Dimensional Topography Measurement System And Key Technology Of The Inner Surface Of The Long And Narrow Pipe

It is a significant method to obtain the internal information of the pipeline to carry out three-dimensional shape measurement on the internal surface of the pipeline.At present,the commonly used measurement methods for internal surface of pipelines are difficult to meet the requirements of measurement efficiency and accuracy for the measurement of internal surface of narrow and long pipelines with small diameter and large length.Given the inadequacies and limitations of prior art,this paper designs a three-dimensional topography measurement system for the inner surface of a narrow and long pipeline with a section of 110 mm × 110 mm and a length of greater than10000 mm,and studies its key technologies.The main research contents of this paper include :According to the measurement requirements and the characteristics of narrow and long pipelines,the overall measurement scheme based on line structured light scanning,local scanning and global splicing is designed.At the same time,the measurement system including four parts : structured light vision sensor,pipeline crawler and control system,axial distance measurement and spatial attitude orientation device and measurement and control software is designed.The calibration method of the system was studied,and the calibration method of the structural light parameters and the calibration method of the cylinder scanning model based on the two-dimensional chessboard target were designed.The experiment verifies that the calibration accuracy of the line structural parameters is better than ±0.060 mm,and the relative rotation angle of the cylinder piston rod around each axis during the scanning process is better than±0.100 degrees.The spatial attitude orientation method of measurement system and the global stitching method of measurement data are studied.The method based on axial distance measurement and spatial attitude orientation is designed,and the spatial pose calculation model of pipeline crawler is established to solve the spatial pose of pipeline crawler in the process of movement.Using the point cloud registration method based on the improved iteration nearest point algorithm,the rotation translation matrix obtained in the previous step is used as the initial value of iteration,and then the point cloud data of each measurement area is highly accurately fused,which solves the problem that the benchmark of local measurement data is not unified in the global splicing.The experiment verifies that the average root mean square error of point cloud registration can reach 0.129 mm.In the laboratory environment,the hardware system is built,and the system measurement software is compiled using both Qt and C++ development frameworks,which integrates the functions of system calibration,motion control,image acquisition and data processing during the experimental process.According to the characteristics of laser stripes in the actual acquisition image,a laser stripe center positioning method suitable for this project is designed to solve the problem of false extraction of laser stripe boundary.The local measurement accuracy verification experiment is performed by using the standard ring gauge,and the diameter measurement experiment accuracy outperforms ±0.189 mm,and the standard deviation of the experiment is 0.132 mm,which verifies the accuracy and repeatability of the local measurement.The functional verification experiment of the system is carried out by using the narrow and long pipelines,and the experiment shows that the measurement system and measurement scheme designed in this paper can realize the automatic and rapid measurement of the three-dimensional morphology of the inner surface of the narrow and long pipelines,and meet the measurement requirements in terms of measurement accuracy and measurement efficiency.