3D Reconstruction And Measurement Of Workpieces Based On Structured Light And Binocular Vision

Welding technology is widely used in many fields,such as vehicle,petrochemical,electronics,ocean engineering and so on.In welding field,based on two-dimensional and three-dimensional vision technology,industrial robot visual navigation system can recognize and track welding joint and weld seam as well as plan the welding path,during which manual intervention is unnecessary.Compared with the 2 dimension(2D)data,the 3 dimension(3D)data can reflect the depth information,so that the robot visual navigation system can better assist welding seam tracking and quality detection.By this means,the safety and efficiency of the system will get improved.Therefore,3D reconstruction and measurement are the basis of welding visual navigation technology.To reconstruct the shape of the target workpiece to realize semi-automatic machining function of welding,an optical measurement method based on Gra y-code structured light and binocular vision is proposed.Which can provide more specific information for seam tracking.The main contents of this research are as follows:1)The imaging platform of the automatic welding tracking system and the imaging characteristics of the object to be measured has been analyzed,and the feasibility of the 3D reconstruction of the whole structure of the welding has been considered synthetically.Considering the difficulties in the stereo matching process caused by the absence of texture features of the welding object,the hardware platform of 3D vision reconstruction measurement system for binocular structured light has been designed and built by using active non-contact optical measurement method.2)Based on the theory of calibration,binocular calibration has been achieved to establish and obtain the connection between camera and reality.The distorting and pole correction are carried out by calculating the internal and external parameters,and the unified reference system is provided for the 3D coordinate calculation.Pole correction reduces the matching problem from two dimensions to one dimension in the whole reconstruction process,which greatly reduces the search amount and computational complexity of the whole algorithm.3)Aiming at the mismatch of matching primitives in the traditional region based stereo matching algorithm,a simple and fault-tolerant 7-bit gray-code projection measurement scheme is added to identify the stereo matching process of matching primitives.To obtain precise segmented pixel block coordinates,the black and white stripe boundary information of the projection pattern is extracted,by adopting the forward and negative code pattern method of projection transverse direction.A complete disparity map is obtained from the matching results,by filling the dead zone of the angle of view and the region where the matching fails.According to the triangulation principle,we can obtain the 3D point clouds by computing the 3D coordinates of the surface points of the object.In order to describe the object more intuitively,greedy projection triangulation is carried out to make the point cloud reconstitute three-dimensional figure,and the surface closer to the reality can be obtained so as to achieve the purpose of 3D reconstruction and measurement of the measured object.The related hardware platform is built for the project of 3D reconstruction of welding workpiece.And the camera calibration,image acquisition,Gray-code coding and decoding are completed.Stereo matching 3D point cloud computing and greedy projection triangulation surface reconstruction of all software work.In this paper,the feasibility analysis experiment of the 3D reconstruction system is carried out in the laboratory environment,and the 3D point cloud reconstruction of the object under test is realized.Considering the industrial production environment and the nondestructive positioning measurement,this method can quickly realize the localization reconstruction of the target workpiece,which has the advantages of low difficulty and high accuracy.Simultaneously meets the requirement of independent programming in the industrial site.At last,the paper summarizes and prospects the related work done in this paper.