Detection Method Of Aircraft Skin Hole Size Based On Laser Vision

At present,aircraft manufacturing is developing towards the digital direction,which is very important to the digital and intelligent measurement of aircraft components.However,for a long time,most aircraft manufacturers mainly detect the skin holes manually,which has the problems of poor consistency of inspection quality and low inspection efficiency.In this paper,based on laser vision measurement technology,the overall structure and hardware structure of the measurement system are designed,and the calibration algorithm,strip center extraction algorithm,point cloud data processing algorithm and circle fitting algorithm of the measurement system are studied in depth,so as to achieve accurate measurement of the characteristics of the aircraft skin hole.The main work of this paper is as follows:(1)The characteristics of the skin hole were analyzed,and the overall design and hardware system design of the skin hole measurement system were carried out,including the selection of camera,lens,line laser transmitter and mobile platform.This paper discusses the principle of laser triangulation and analyzes the factors that may cause measurement error in the measurement process.(2)The camera model and the line structured light measurement model in the measurement system model are calibrated in order to realize the three-digit reconstruction of the line structured light scan.In this paper,Chang’s calibration method is used to calibrate the camera model.Based on the results of the initial calibration,the accuracy of the camera calibration is improved through the secondary calibration.Based on the principle of cross ratio invariance,the calibration of the optical plane is completed.The algorithm of strip center extraction of line structure light is analyzed to extract strip center.(3)According to the characteristics of the skinned hole point cloud data acquired by line structured light scanning,unnecessary noise points are mixed in the collected point cloud data due to various errors in the scanning measurement process,which will have a great impact on the measurement results.The causes of the errors are analyzed,and the error noise points are classified.The point cloud denoising and filtering algorithm is studied,and the noise points are filtered and removed.(4)According to the type of line scanning point cloud,the point cloud boundary extraction algorithm is analyzed,and finally the longitude and latitude line scanning method is adopted to extract the boundary features of skin holes.The method of circle fitting is discussed and the least square circle fitting method is adopted as the circle fitting method in this paper.Finally,simulation experiments were carried out on the simulated point cloud data and the actual measured point cloud data through Matlab to verify that the measurement system designed in this paper can accurately measure the geometric size of the skin hole.