Research On Measurement Technology Of Bending Forming Parameters Based On Line Structured Light

The CNC bending machine is used to bend the flat metal sheet into a part with a specific angle.The bending angle is one of the most important processing parameters in the forming process of the CNC bending machine.Measuring the bending angle by hand is ineffective,and hard to guarantee the accuracy.This paper studies and realizes the design and development of a bending parameter measurement system based on line structured light,and realizes real-time measurement of bending angles of different sizes,different materials,and different thickness.For domestic CNC bending machine sheet bending angle measurement method and bending machine operation method,the various requirements of the CNC bending machine for the angle measurement system are analyzed,the technical indicators of the angle measurement system are determined,and the overall implementation of the measurement system is designed.Aiming at the problem that the structured light strips are difficult to perform 3D reconstruction due to the difference of poses in the binocular camera,the centerline extraction algorithms of structured light based on different realization principles are studied and compared,and the one with higher extraction accuracy is finally selected.Aiming at the problem of light reflection on the surface of the smooth sheet,the Hough line transformation is used and the appropriate length threshold is set to extract the center line of the structured light bar.In order to obtain a higher accuracy of the 3D reconstruction of the structured light centerline,the accuracy of the 3D reconstruction method under the parallel camera model and the non-parallel camera model was studied and compared through experiments.The parallel camera model and the three-dimensional reconstruction method of triangulation are determined.Aiming at the problem that the imaging planes of the binocular cameras cannot be completely parallel in actual situations,stereo correction is used to make the imaging planes of the two cameras coplanar and aligned.Triangulation is used to complete the threedimensional reconstruction of the structured light centerline from the two-dimensional pixel coordinates to the spatial three-dimensional coordinates,and obtain the structured light centerline point cloud data.The random consensus algorithm divides the point cloud,and the least squares method fits the center line to obtain the direction vector of the center line,and completes the calculation of the bending angle.In order to realize the visualization of the measurement process and results and to verify the effectiveness of the measurement system designed in this paper,the software design and implementation of the measurement system,the calibration experiment of the binocular camera,and the measurement experiment of the bending angle of the sheet were completed based on QT and Visual Studio,which verified that the measurement accuracy of the measurement system and the measurement efficiency can meet the work requirements.The error model of structured light projection is established to analyze the error of the hardware part of the measurement system.