A Technology For Extracting Repair Features Of Aircraft Skin Based On Laser Scanning

Processing and docking quality of aircraft skin is of great importance of the assembly efficiency and quality of the aircraft.There is a repair amount after the roughing of the skin,and the skin needs to be repaired in order to achieve accurate skin docking.The traditional method of repairing is manual scribe and manual cutting,which has low efficiency and poor quality and cannot meet modern production requirements.The trend of skinning nowadays is the use of CNC machining and accurate repair features is required for CNC machining.In order to provide accurate repairing features for the skin repairing,this paper designs a technical method for extracting repair features of aircraft skin based on laser scanning.The aircraft skin scanning data processing method was studied,and the corresponding extraction software was developed and the software was verified.The main contributions in this thesis are as follows:(1)The extraction scheme of the skinning features is designed.Repair features include repair amount and repair boundary.The skin repair features extraction technology scheme is formulated according to the extraction requirements.This technical solution includes aircraft skin measurement process,skin repairing amount and skinning boundary extraction method.(2)The method of reconstruction of the end surface of the skin is studied.Boundary points are extracted based on discrete curvature,and the point cloud data are segmented by extracting the boundary feature points in boundary points to obtain the data of the end surface of the skin.Then,the serrated end face is focused on.The boundary feature points are sorted by the improved nearest-point algorithm to finally sort the end-face data.The end face data is segmented and the end face reconstructed.The reconstructed end face is used for the extraction of the repair amount.(3)The method of repair boundary reconstruction is studied.The point cloud on the upper surface of the skin is triangulated,and the intersection points of the end face and the upper surface triangle meshed are obtained.When the skin end face is a serrated face,a method for transforming the spatial curve fitting into a plane curve fitting is proposed and a curve reconstruction method which can ensure connection point's extracting precision and curvature smoothing is proposed.(4)The software of aircraft skin repairing features extraction based on laser scanning is developed to realize the control of the relevant parameters of the measurement process and the processing of the skin scanning data.The accuracy of repair features extraction is verified by experiments.