Research On On-line Measurement Technology Of Aero-engine Blade Based On Binocular Structure Light

The blade is an important part of the aircraft engine,and its profile accuracy affects the performance of the engine.The robot blade grinding can remove the tool path dents and surface hardening layer left after the blade is milled to ensure the accuracy of the profile.However,due to the limitations of offline measurement methods,the integration of blade measurement and grinding could not be achieved.In response to this problem,this paper combines the development status of blade optical measurement and binocular structured light,and studies the online measurement technology of blade profile based on binocular structured light.The main work is as follows:Based on the principle of binocular structured light measurement,the blade is coded by a hybrid coding method of four-step phase shift method and eight-step phase shift method,the multi-frequency hierarchical method is used to calculate the absolute phase,and the blade contour is reconstructed according to the triangulation method.Explain the calibration principle of binocular structured light system,including the principle of monocular camera calibration and the principle of stereo calibration.Aiming at the registration problem of multi-angle measurement data of blade-like flat parts,in order to reduce the error caused by the repeated positioning accuracy of robots to point cloud registration,an online calibration method of rotary axis based on machine vision is proposed.Before measuring the blades each time,obtain the posture relationship between the camera and the calibration plate through the image of the checkerboard calibration plate(fixed on the sixth axis of the robot)under different perspectives,and directly solve the rigid transformation matrix between the sixth axis and the camera through coordinate transformation.Then control the robot to rotate the blade to obtain multi-view point cloud data.In order to meet the requirements of online blade measurement,a point cloud registration algorithm based on the rotation axis and the iterative closest point(ICP)algo-rithm is proposed,which can automatically complete the multi-view point cloud registration of the blade according to the rotation axis online calibration results,and obtain complete and accurate blade point cloud data.Build a binocular structure light blade online measurement system,and perform standard gauge block measurement and blade measurement experiment,the gauge block measurement deviation is better than 0.044 mm.The blade measurement model was compared with the reference model scanned by Leica T-Scan 5 in 3D,and the average deviation was-0.007 mm.The experimental results show that the measurement accuracy of the blade measurement system can reach 0.05 mm.