Research On The Digital Coordination Deviation Of Pipe

Some segmented pipelines may be impossible to weld seamlessly together.It is necessary to do some grinding work on the parts of the pipelines so as to make it possible.For now,the work has always been conducted by operators in the way of manually cutting and polishing,which leads to long manufacturing time and no consistent quality guarantee.Here,the digital coordination method was raised in response to the above difficulties.Before being welded together,firstly,the actual data—position of tank and engine flanges,orientation and route of the segmented pipelines would be sampled.Secondly,viable solution would be found by emulating artificial polishing and assembly in digital space,according to final requirements.Finally,the coordination results would be used for machining the segmented pipelines.The process of digital coordination is: reverse reconstruction of the pipe fitting,object digitization,digital coordination,and the physical process of digital coordination(digital lofting).This thesis mainly analyses the deviation during the reverse engeering for pipe,object digitization and digital lofting using robot.The influence of measuring point location,measuring instrument and measuring point density on the reconstruction precision would be analyzed,then provide measurement advice.The surface of the pipe to be coordinated would be reconstructed by using the free surface fitting,cylinder fitting,and the method of surface reconstruction with the smaller deviation woule be analyzed.The axis would be parameterized by the starting point of the curvature,center of the axis and the normal vector of the axis.Parameters such as curvature centers of the elbow sections could be solved using the mean method of three point method and least square method,therefore,a more accurate solution can be found.Analyze the extraction accuracy of each parameter of the axis.The position of pipe fitting space is represented by parameterized axis.Robot lofting refers to the use of data-driven robot to cut and underline the pipe fittings.The unity of coordination result data and the robot coordinate system are realized by using the work object coordinate system.The influence of the calibration deviation of the work object coordinate and tool coordinate on the robot lofting is analyzed.