Research And Application Of Workpiece Measurement Technology Based On 3D Point Cloud

With the improvement of industrial productivity since the 21st century,the measurement efficiency of traditional workpiece measurement technology has gradually failed to keep up with the rapidly increasing measurement demand.With the development of image processing technology and optical camera technology in recent years,the 3D measurement technology of workpieces by laser scanners has gradually improved and can take advantage of its high precision,high efficiency,non-contact and other advantages in workpiece measurement.It is of great significance to study the measurement technology of workpieces based on 3D point cloud to help industrial production automation.The research content of this paper originated from the project of "Online Measurement Technology of Geometric Precision Based on Machine Vision".According to the structural characteristics of the tested special workpieces in the project,the overall scheme design of the workpiece measurement system based on the three-dimensional point cloud is completed.The technical difficulties such as the extraction of the complex structure of the workpiece,the conversion of point cloud data to the mathematical model is solved,and the development of the 3D measurement software and the workpiece measurement experiment is completed.The main content of the paper is as follows:(1)According to the requirements of the workpiece measurement system,the overall scheme of the workpiece measurement system is proposed,and the hardware selection and system design are completed,and the measurement system is built.(2)Aiming at the measurement requirements of workpieces,a set of workpiece measurement process based on 3D point cloud is designed.Several steps including point cloud scanning,point cloud filtering,point cloud segmentation,point cloud fitting and error function calculation are discussed in detail.(3)The key technologies encountered in the measurement process is studied.Firstly,aiming at the ICP point cloud fine registration algorithm,its advantages and disadvantages are studied,and an improved ICP algorithm combining distance threshold and distance ratio is proposed,and the accuracy of the improved algorithm is improved through comparative experiments.Then for the conversion of point cloud data to mathematical model,the RANSAC method suitable for the characteristics of point cloud data is used for fitting,the fitting process of the plane model and the 3D circular model used in the measurement is discussed in detail.(4)The software development of the workpiece measurement system based on 3D point cloud is completed.Firstly software requirements analysis and architecture design is conducted,then the measurement process is designed and core modules such as point cloud acquisition module,point cloud preprocessing module,point cloud segmentation module is developed.Finally,the 3D measurement function is verified through software testing.(5)For the tested special workpieces involved in the project,the research and development of the workpiece measurement system is used for measurement,and the measurement results are compared with the 3D software Geomagic Studio to verify the accuracy of the measurement results.Finally,the measurement error is analyzed.