US 11,941,329 B2
Method for analyzing fuselage profile based on measurement data of whole aircraft
Jun Wang, Nanjing (CN); Tianchi Zhong, Nanjing (CN); Zhongde Shan, Nanjing (CN); Yuan Zhang, Nanjing (CN); and Kun Xiao, Nanjing (CN)
Assigned to Nanjing University of Aeronautics and Astronautics, Nanjing (CN)
Filed by Nanjing University of Aeronautics and Astronautics, Nanjing (CN)
Filed on May 8, 2023, as Appl. No. 18/313,410.
Claims priority of application No. 202210483143.7 (CN), filed on May 6, 2022.
Prior Publication US 2023/0274047 A1, Aug. 31, 2023
Int. Cl. G06F 30/15 (2020.01); B64C 1/00 (2006.01)
CPC G06F 30/15 (2020.01) [B64C 1/00 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A method for analyzing fuselage profile based on measurement data of an aircraft, comprising:
(S1) acquiring point-cloud data of the aircraft via a laser scanner, selecting point-cloud data of a fuselage component from the point-cloud data of the aircraft, and setting a bounding box of the point-cloud data of the fuselage component;
(S2) based on a weighted locally optimal projection (WLOP) operator, extracting a medial axis of the fuselage component from the point-cloud data of the fuselage component according to Ll median curve-skeleton concept of point cloud;
(S3) uniformly sampling the medial axis of the fuselage component into a plurality of skeleton points, and extracting a discrete point set of a cross-section of the fuselage component;
(S4) performing circle fitting on the discrete point set of the cross-section of the fuselage component to obtain a fitted circle of each cross-section slice of the fuselage component and parameters of the fitted circle; and
(S5) calculating a deformation displacement measurement indicator μ of the cross-section of the fuselage component to evaluate a profile of the cross-section of the fuselage component;
wherein the step (S2) comprises:
subjecting the point-cloud data of the fuselage component to smoothing and resampling based on the WLOP operator; and
extracting Ll median skeletons varying in size from the point-cloud data of the fuselage component by using a L1 median target energy function with a regular term based on the L1 median curve-skeleton concept to obtain the medial axis of the fuselage component; and
the step (S4) comprises:
(S401) regarding any cross-section slice Sv, initializing parameters of random sample and consensus (RANSAC) algorithm, setting the maximum number of iterations W, and assuming a score S(c0) and a threshold of an initial candidate circle c0;
(S402) calculating a sampling probability of each point inside the cross-section slice based on sampling point density of the cross-section slice; wherein the sampling probability of each point inside the cross-section slice is expressed as follows:

OG Complex Work Unit Math
wherein PVk indicates a sampling probability of a k-th point inside the cross-section slice; DVk indicates a sampling density of the k-th point inside the cross-section slice; |l| indicates the number of points contained in a local neighborhood l centered around the k-th point; r is a radius of the local neighborhood l; Dmax indicates a maximum sampling density inside the cross-section slice; and Dmin indicates a minimum sampling density inside the cross-section slice;
(S403) during one circle fitting, replacing random sampling in the RANSAC algorithm with sampling based on the sampling probability obtained in (S402), and calculating parameters (ad, bd, rd) of a candidate circle Ca corresponding to the sampling probability, wherein as indicates a first point on the candidate circle Cd; bd indicates a second point on the candidate circle Cd, and rd indicates a radius of the candidate circle Cd;
(S404) counting a sampling density of each inlier in an inlier set within a threshold of the candidate circle Cd, and taking the sampling density as a score S(Cd)=Σe=1mDte of the candidate circle Cd, wherein m represents the number of inliers; e is an index of the inliers; and Dte is a sampling density of an e-th inlier in the inlier set;
(S405) if S(Cd)>S(C0), assigning S(Cd) to S(c0), and deriving the parameters (ad, bd, rd) of the candidate circle Cd; and
(S406) if the number of fittings N<W, repeating steps (S403)-(S405), and if N≥W, obtaining fitted circles of all cross-section slices and parameters thereof.