Multi-view Point Cloud Splicing Research Of Air Compressor Blade Based On Inverse Rotation Method

With the rapid development of China civil aviation transportation industry,the role of aviation maintenance technology in the field of aviation has become even more important.Blade as a key part of aeroengine,due to its complex working environment prone to fatigue damage.Repairable damaged blades multilayer and multipass repairs need to be performed on the basis of a highly accurate 3D model of the blade to be repaired.To obtain the complete 3D point cloud model of the blade,it is an indispensable link to the leaf cloud stitching on the basis of obtaining the multi-angle surface type 3D point cloud by using the high-precision grating projection 3D measurement method.The 3D point cloud data splicing method is generally based on the shape characteristics of the measured object to be selected.Because of the flaky space shape of the aviation blade,it is difficult to obtain the common point cloud of the blade pot and the blade back.The reverse rotation method is used to stitch.Therefore,the research on raster projection 3D measurement and multi-view point cloud stitching system is carried out.On the premise of knowing the method of 3D point cloud acquisition and analyzing the method of splicing reverse point cloud at home and abroad,based on the three-dimensional measurement method of raster projection,a high-precision rotating platform is used to rotate the fixed angle ? to realize the multi-angle point cloud access.To achieve multi-angle point cloud stitching needs to rotate the center axis of the turntable as a medium,the three-dimensional point cloud rotation transform to the same coordinate system as the base point cloud.The calibration of the central axis of the turntable is the key link of multi-view point cloud splicing by the reverse rotation method.Aiming at the multi-view 3D measuring and splicing system of raster projection,a synchronous calibration method of camera and turntable center axis based on 2D checkerboard calibration plate is proposed.In the simulation experiment,the maximum reverse projection error of the camera calibration result is 0.42 pixel.Each fitting center to the standard axis straight line distance within 0.05 mm.In the actual test,the average deviation of the reconstructed standard sphere diameter from the standard sphere diameter of 38.0713 mm is 0.1293 mm,and the variance of the measurement result is 0.0014.The detection and extraction of corner points within the checkerboard grid is one of the important techniques for calibrating the center axis of the turntable using the 2D checkerboard calibration plate.Therefore,in this paper,in order to solve the problem of corner detection in the checkerboard,this paper proposes a method to detect the corner within the checkerboard.The method can detect all 48 corner points of the checkerboard in 9 seconds,which has obvious advantages compared with the Harris method and the improved method.And the environmental noise has less influence on the method and has good robustness.In the stitching test of the four view point cloud of the sixth stage of the aero-compressor using the raster projection 3D measurement and the reverse rotation point cloud stitching method,the maximum thickness of the three sections of the blade model and the solid blade obtained after splicing is 0.103 mm.The average relative deviation is 2.66%,which satisfies the need of blade welding trajectory planning.