| The grinding of pipe end weld is an important process in the process of oil and gas pipeline processing,which has an important impact on the reliability of the pipeline laying.However,The existing grinding method of steel pipe end weld has some shortcomings,such as low production efficiency,low qualified rate,grinding quality depends on the operating level of workers,endangering the physiological health of workers and so on,which can not meet the requirements of modern intelligent manufacturing production line.In order to achieve adaptive and intelligent polishing of steel pipe end welds,this study has conducted research on vision-guided robot flexible polishing technology.Through research in three aspects,including robot hand-eye calibration,point cloud data processing,and polishing path planning,the accuracy of hand-eye calibration and polishing quality have been improved.The main research content of the study includes the following aspects:Firstly,a method based on the M-shaped standard block as the calibration object is proposed for the hand-eye calibration problem of the line structured light sensor-guided robot system.A calibration model is established based on the constraints of the positions of the two parallel ridge lines of the calibration block,which includes the hand-eye relationship,robot kinematics,and errors of the two straight line pose parameters.Based on fixed-point constraints,the initial hand-eye relationship is solved and the initial values of the straight line pose parameters are calculated.Then,the error parameters are solved by the least squares method and compensated into the model iteratively,obtaining the final hand-eye relationship and kinematic error parameters of the robot.Secondly,in view of the contour point cloud of the steel pipe base metal collected by the linear structured light sensor,the point cloud preprocessing method of local weighted regression was selected to complete the identification of the weld end position,and the weld identification method based on the sum of residual squares and the extraction method of the weld inflection point by the maximum distance analysis method were proposed.the point cloud of the original surface was transformed and extended to the plane by cubic spline interpolation and inverse distance-weighted interpolation.According to the characteristics of spiral pipe welds,a visually guided flexible welding grinding method was designed.The grinding path position planned by this method can enable the tool to actively adapt to the curvature of the area being polished and form the polishing track of "X".Finally,the upper computer software is developed and a lot of polishing experiments are carried out.The software of hand-eye calibration and path planning algorithm was developed,and the automation of hand-eye calibration and flexible grinding of pipe end end was realized by PC SDK.The feasibility of hand-eye calibration algorithm and path planning algorithm is verified by experiments.The grinding experiment of the robot’s internal and external welds was completed and secondary testing was carried out.After grinding,the residual height of the external welds was less than 0.1 mm,and the residual height of the internal welds was less than0.3 mm,which met the requirements of welding seams polishing.In summary,The robot grinding scheme of pipe end weld with visual guidance designed in this paper has completed the grinding experiment verification and achieved good grinding effect,which has practical application value and popularization application value. |
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