阅读说明：本技术 一种基于翼身对接实测数据的整流蒙皮构造方法 (Rectification skin construction method based on measured data of wing body butt joint ) 是由 隋少春 汪俊 唐皓 朱绪胜 于 2020-06-24 设计创作，主要内容包括：本发明是一种基于翼身对接实测数据的整流蒙皮构造方法,首先利用高精度三维激光扫描仪扫描翼身连接处及其附近蒙皮的三维外形点云数据；再根据翼身连接处的整流蒙皮安装台阶的方向信息,在任一处构造台阶的法线和切线,利用该处台阶的切线在该处台阶的底部构造一条NURBS曲线,利用该处台阶的法线构造高度线,在该处台阶的顶部利用翼身连接处附近蒙皮的点云的流型信息构造一条NURBS曲线；接着利用每个截面形状中底部端点拟合NURBS曲线,作为截面的扫掠线；最后利用多截面扫掠方法获得整流蒙皮的外形模型。该种整流蒙皮构造方法通过对三维激光扫描仪采集飞机翼身对接部分周围三维点云数据作逆向重建构造出能与其装配的最优整流蒙皮三维数字模型。(The invention relates to a method for constructing a rectification skin based on actual measurement data of wing body butt joint, which comprises the steps of firstly, scanning three-dimensional appearance point cloud data of a skin at the joint of a wing body and the skin near the joint of the wing body by using a high-precision three-dimensional laser scanner; constructing a normal line and a tangent line of the step at any position according to the direction information of the step for installing the rectifying skin at the connection position of the wing body, constructing a NURBS curve at the bottom of the step by using the tangent line of the step, constructing a height line by using the normal line of the step, and constructing a NURBS curve at the top of the step by using the flow pattern information of the point cloud of the skin near the connection position of the wing body; fitting a NURBS curve by using the bottom endpoint in each section shape as a sweep line of the section; and finally, obtaining the appearance model of the rectifying skin by using a multi-section sweeping method. According to the method for constructing the rectification skin, the three-dimensional laser scanner is used for collecting three-dimensional point cloud data around the butt joint part of the wing body of the airplane to perform reverse reconstruction to construct an optimal rectification skin three-dimensional digital model capable of being assembled with the three-dimensional laser scanner.)

1. A rectification skin construction method based on measured data of wing body butt joint is characterized by comprising the following steps: the model construction method of the rectification skin comprises the following steps:

step 1, scanning three-dimensional appearance point cloud data of a wing body joint and a skin nearby the wing body joint by using a high-precision three-dimensional laser scanner;

step 2, constructing a section of the rectification skin, constructing a normal line and a tangent line of the step at a required position according to direction information of a step for installing the rectification skin at the connection position of the wing body, constructing a NURBS curve at the bottom of the step by utilizing the tangent line of the step, constructing a height line by utilizing the normal line of the step, and constructing a NURBS curve at the top of the step by utilizing flow pattern information of point cloud of the skin near the connection position of the wing body;

step 3, fitting a NURBS curve by utilizing the bottom endpoint in each cross section shape to be used as a sweep line of the cross section;

and 4, obtaining the appearance model of the rectifying skin by using a multi-section sweeping method.

2. The method for constructing the rectifying skin based on the measured data of the butt joint of the wing body as claimed in claim 1, wherein: in the step 1, the skin at the connection part of the wing body and the skin near the connection part of the wing body are a step structure fixedly installed on the rectification skin and the outer edge structure of the step structure.

3. The method for constructing the rectifying skin based on the measured data of the butt joint of the wing body as claimed in claim 2, wherein: in the step 2, the concrete steps of constructing the section of the rectifying skin are as follows:

step 2.1, determining the positions of the sections to be obtained, and obtaining a section plane of each position;

step 2.2, determining a section plane, performing surface fitting on the point cloud of the side wall and the bottom of the step, and taking any point on an intersection line of the curved surfaces as a point A; taking the tangent vector of the intersection line at the point A as a direction line; fitting a plane at the bottom of the step, and taking a vector perpendicular to the direction line in the plane as a tangent line; constructing a plane by the direction line and the tangent line, and taking a vector which is perpendicular to the plane and passes through the point A as a normal line; a section plane is determined by a normal line and a plane constructed by a tangent line;

step 2.3, performing plane fitting on the side wall of the step around the cross section and the plane of the cross section, extracting an intersection line of the plane and the plane of the cross section, namely a height line of the shape of the cross section, and performing the same operation on the step on the other symmetrical side to obtain two groups of height lines on two sides of the same plane of the cross section;

step 2.4, performing plane fitting on the bottom surface of the step around the cross section to obtain an intersection line of the bottom plane and the side wall plane, and enabling the intersection point of the intersection line of the bottom plane and the side wall plane and the cross section plane to be an endpoint of a bottom NURBS curve; extracting an intersection line of the cross-sectional plane and the bottom plane, making the intersection line of the cross-sectional plane and the bottom plane be a direction vector of one endpoint of the bottom NURBS curve, performing the same operation on the symmetrical steps on the other side, and constructing the bottom NURBS curve through the two endpoints of the bottom NURBS curve and the two groups of corresponding direction vectors;

step 2.5, performing plane fitting on the top surface of the step around the cross section to obtain an intersection line of the top plane and the side wall of the step, setting the intersection point of the intersection line of the top plane and the side wall of the step and the cross section plane as an endpoint of the top NURBS curve, extracting the intersection line of the cross section plane and the top plane, setting the intersection line of the cross section plane and the top plane as a direction vector of the endpoint of the top NURBS curve, performing the same operation on the step on the other symmetrical side, and constructing the top NURBS curve through the two endpoints of the top NURBS curve and the two corresponding groups of direction vectors;

and 2.6, connecting the two height lines, the top NURBS curve and the bottom NURBS curve on each section plane to form a closed section model.

4. The method for constructing the rectifying skin based on the measured data of the butt joint of the wing body as claimed in claim 3, wherein: in the step 2.1, for the continuously-changed rectifying skin, the cross section positions are densely selected in the area with large shape change, and the cross section positions are sparsely selected in the area with small shape change; for the rectifying skin with irregular change, the section position is selected at the position with the shape abrupt change.

5. The method for constructing the rectifying skin based on the measured data of the butt joint of the wing body as claimed in claim 3, wherein: in step 2.4 and step 2.5, the NURBS curve is mathematically defined as follows:

p (K) is the position vector on the curve, N_i,m(K) Is a m-th order spline basis function;

wherein the mathematical definition of the basis functions is:

in the formula, Pi is a control point, Ri is a weight factor, and K is a node vector.

6. The method for constructing the rectifying skin based on the measured data of the butt joint of the wing body as claimed in claim 2, wherein: in step 3, the step of fitting the sweep line of the cross section is as follows:

step 3.1, extracting end points at the same position of the bottom on all the determined section planes;

and 3.2, fitting all the endpoints at the same position to obtain a NURBS curve passing through all the endpoints, so that the skin digital model obtained by sweeping has continuity with the butt joint part of the wing body, and the appearance of the airplane is continuous after the skin is actually installed.

Technical Field

The invention relates to the technical field of three-dimensional model reconstruction, in particular to a method for constructing a rectification skin based on measured data of butt joint of a wing body.

Background

With the development of aviation industry in China, the requirement on the precision of a new type of airplane is higher and higher. The aircraft has many and complicated parts, wherein the shape of the fairing skin influences the aerodynamic appearance of the aircraft and is one of key parts in the aircraft manufacturing process, so that the improvement of the assembly precision of the fairing skin is very significant. During the assembly of an aircraft, the pre-assembly of the fairing skin is a very important part, and in the traditional process, the repair of the aircraft fairing skin is completed in the step, and the repair amount of the actual fairing skin can be obtained by comparing the existing skin parts with the assembly position through the pre-assembly. However, the method needs to reprocess the existing skin parts, even the existing parts can not be processed, and the method can not be accurately repaired once and needs to be repaired for many times, thereby greatly influencing the manufacturing speed. Therefore, a new method is needed, an ideal rectification skin model is directly obtained through an actual assembly position, the process flow is shortened, and the overall efficiency is improved.

Disclosure of Invention

The invention provides a rectification skin construction method based on measured data of wing body butt joint aiming at the defects in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a rectification skin construction method based on measured data of wing body butt joint is characterized by comprising the following steps: the model construction method of the rectification skin comprises the following steps:

step 1, scanning three-dimensional appearance point cloud data of a wing body joint and a skin nearby the wing body joint by using a high-precision three-dimensional laser scanner;

step 2, constructing a section of the rectification skin, constructing a normal line and a tangent line of the step at a required position according to direction information of a step for installing the rectification skin at the connection position of the wing body, constructing a NURBS curve at the bottom of the step by utilizing the tangent line of the step, constructing a height line by utilizing the normal line of the step, and constructing a NURBS curve at the top of the step by utilizing flow pattern information of point cloud of the skin near the connection position of the wing body;

step 3, fitting a NURBS curve by utilizing the bottom endpoint in each cross section shape to be used as a sweep line of the cross section;

and 4, obtaining the appearance model of the rectifying skin by using a multi-section sweeping method.

In the step 1, the skin at the connection part of the wing body and the skin near the connection part of the wing body are a step structure fixedly installed on the rectification skin and the outer edge structure of the step structure.

In the step 2, the concrete steps of constructing the section of the rectifying skin are as follows:

step 2.1, determining the positions of the sections to be obtained, and obtaining a section plane of each position;

step 2.2, determining a section plane, performing surface fitting on the point cloud of the side wall and the bottom of the step, and taking any point on an intersection line of the curved surfaces as a point A; taking the tangent vector of the intersection line at the point A as a direction line; fitting a plane at the bottom of the step, and taking a vector perpendicular to the direction line in the plane as a tangent line; constructing a plane by the direction line and the tangent line, and taking a vector which is perpendicular to the plane and passes through the point A as a normal line; a section plane is determined by a normal line and a plane constructed by a tangent line;

step 2.3, performing plane fitting on the side wall of the step around the cross section and the plane of the cross section, extracting an intersection line of the plane and the plane of the cross section, namely a height line of the shape of the cross section, and performing the same operation on the step on the other symmetrical side to obtain two groups of height lines on two sides of the same plane of the cross section;

step 2.4, performing plane fitting on the bottom surface of the step around the cross section to obtain an intersection line of the bottom plane and the side wall plane, and enabling the intersection point of the intersection line of the bottom plane and the side wall plane and the cross section plane to be an endpoint of a bottom NURBS curve; extracting an intersection line of the cross-sectional plane and the bottom plane, making the intersection line of the cross-sectional plane and the bottom plane be a direction vector of one endpoint of the bottom NURBS curve, performing the same operation on the step on the other side, and constructing the bottom NURBS curve through two endpoints of the bottom NURBS curve and two groups of corresponding direction vectors;

step 2.5, performing plane fitting on the top surface of the step around the cross section to obtain an intersection line of the top plane and the side wall of the step, setting the intersection point of the intersection line of the top plane and the side wall of the step and the cross section plane as an endpoint of a top NURBS curve, extracting the intersection line of the cross section plane and the top plane, setting the intersection line of the cross section plane and the top plane as a direction vector of the endpoint of the top NURBS curve, performing the same operation on the step on the other side, and constructing the top NURBS curve through the two endpoints of the top NURBS curve and the two corresponding sets of direction vectors;

and 2.6, connecting the two height lines, the top NURBS curve and the bottom NURBS curve on each section plane to form a closed section model.

In the step 2.1, for the continuously-changed rectifying skin, the cross section positions are densely selected in the area with large shape change, and the cross section positions are sparsely selected in the area with small shape change; for the rectifying skin with irregular change, the section position is selected at the position with the shape abrupt change.

In step 2.4 and step 2.5, the NURBS curve is mathematically defined as follows:

p (K) is the position vector on the curve, N_i,m(K) Is a m-th order spline basis function;

wherein the mathematical definition of the basis functions is:

in the formula, Pi is a control point, Ri is a weight factor, and K is a node vector.

In step 3, the step of fitting the sweep line of the cross section is as follows:

step 3.1, extracting end points at the same position of the bottom on all the determined section planes;

and 3.2, fitting all the endpoints at the same position to obtain a NURBS curve passing through all the endpoints, so that the skin digital model obtained by sweeping has continuity with the butt joint part of the wing body, and the appearance of the airplane is continuous after the skin is actually installed.

The method for constructing the rectification skin based on the actual measurement data of the butt joint of the wing body has the advantages that: three-dimensional point cloud data around the butt joint part of the wing body of the airplane are collected through a three-dimensional laser scanner, and an optimal rectification skin three-dimensional digital model capable of being assembled with the point cloud data around the skin to be modeled is constructed through reverse reconstruction. Furthermore, a plurality of groups of NURBS curves are established through points and vectors which are fitted by the point cloud model in each section plane, so that the edge of each section plane can be accurately determined; by densely selecting the section planes in the area with large shape change and sparsely selecting the section planes in the area with small shape change, on one hand, the data base of the subsequent multi-section sweep modeling is ensured through the selection of a plurality of groups of section planes, and on the other hand, the continuity and the accuracy of the skin modeling are also ensured.

Drawings

Fig. 1 is a schematic working flow diagram of a method for constructing a rectification skin based on measured data of butt joint of a wing body according to the present invention.

Fig. 2 is a point cloud model of the skin at the connection position of the wing body and the skin near the connection position of the wing body in the method for constructing the rectification skin based on the measured data of the butt joint of the wing body.

Fig. 3 is a schematic diagram of fitting the shape of a cross section in the method for constructing a rectification skin based on measured data of wing body butt joint.

Fig. 4 is a schematic diagram of a multi-section sweep in a method for constructing a rectification skin based on measured data of wing body butt joint according to the present invention.

Fig. 5 is a schematic diagram of a skin sweeping result in the method for constructing a rectification skin based on measured data of wing body butt joint.

Detailed Description

The invention will now be described in further detail with reference to figures 1 to 3.

As shown in fig. 1, a method for constructing a rectification skin based on measured data of butt joint of a wing body is characterized in that: the model construction method of the rectification skin comprises the following steps:

step 1, scanning three-dimensional appearance point cloud data of a wing body joint and a skin nearby the wing body joint by using a high-precision three-dimensional laser scanner; the schematic diagram of the wing body joint and the skin near the wing body joint is shown in fig. 2, and the wing body joint and the skin near the wing body joint are a step structure fixedly installed on the rectification skin and the outer edge structure of the step structure.

Step 2, constructing a section of the rectification skin, constructing a normal line and a tangent line of the step at a required position according to direction information of a step for installing the rectification skin at the connection position of the wing body, constructing a NURBS curve at the bottom of the step by utilizing the tangent line of the step, constructing a height line by utilizing the normal line of the step, and constructing a NURBS curve at the top of the step by utilizing flow pattern information of point cloud of the skin near the connection position of the wing body;

step 2.1, determining the positions of the sections to be obtained, and obtaining a section plane of each position;

step 2.2, determining a section plane, performing surface fitting on the point cloud of the side wall and the bottom of the step, and taking any point on an intersection line of the curved surfaces as a point A; taking the tangent vector of the intersection line at the point A as a direction line; fitting a plane at the bottom of the step, and taking a vector perpendicular to the direction line in the plane as a tangent line; constructing a plane by the direction line and the tangent line, and taking a vector which is perpendicular to the plane and passes through the point A as a normal line; a section plane is determined by a normal line and a plane constructed by a tangent line; as shown in fig. 2, vector 1 is the direction of the height line, vector 2 is the direction line, and vector 3 is the normal;

step 2.3, performing plane fitting on the side wall of the step around the cross section and the plane of the cross section, extracting an intersection line of the plane and the plane of the cross section, namely a height line of the shape of the cross section, and performing the same operation on the step on the other symmetrical side to obtain two groups of height lines on two sides of the same plane of the cross section;

step 2.4, performing plane fitting on the bottom surface of the step around the cross section to obtain an intersection line of the bottom plane and the side wall plane, and enabling the intersection point of the intersection line of the bottom plane and the side wall plane and the cross section plane to be an endpoint of a bottom NURBS curve; extracting an intersection line of the cross-sectional plane and the bottom plane, making the intersection line of the cross-sectional plane and the bottom plane be a direction vector of one endpoint of the bottom NURBS curve, performing the same operation on the step on the other side, and constructing the bottom NURBS curve through two endpoints of the bottom NURBS curve and two groups of corresponding direction vectors;

step 2.5, performing plane fitting on the top surface of the step around the cross section to obtain an intersection line of the top plane and the side wall of the step, setting the intersection point of the intersection line of the top plane and the side wall of the step and the cross section plane as an endpoint of a top NURBS curve, extracting the intersection line of the cross section plane and the top plane, setting the intersection line of the cross section plane and the top plane as a direction vector of the endpoint of the top NURBS curve, performing the same operation on the step on the other side, and constructing the top NURBS curve through the two endpoints of the top NURBS curve and the two corresponding sets of direction vectors;

and 2.6, as shown in fig. 3, connecting the two height lines, the top NURBS curve and the bottom NURBS curve on each section plane to form a closed section model, wherein a step structure fixedly installed on the fairing skin is shown in fig. 3.

Step 3, fitting a NURBS curve by utilizing the bottom endpoint in each cross section shape to be used as a sweep line of the cross section;

step 3.1, extracting end points at the same position of the bottom on all the determined section planes;

and 3.2, fitting all the endpoints at the same position to obtain a NURBS curve passing through all the endpoints, so that the skin digital model obtained by sweeping has continuity with the butt joint part of the wing body, and the appearance of the airplane is continuous after the skin is actually installed.

And 4, performing multi-section sweeping on all the generated section shapes, and obtaining the appearance model of the rectifying skin shown in the figure 5 by using a multi-section sweeping method.

Further, in the step 2, a plurality of groups of NURBS curves are established through points and vectors fitted by the point cloud model in each section plane, so that the edge of each section plane can be accurately determined

Further, in step 2.1, for the continuously-changing rectification skin, as shown in fig. 4, the cross-section positions are densely selected in the area with large shape change, and the cross-section positions are sparsely selected in the area with small shape change; for the rectifying skin with irregular change, the section position is selected at the position with the shape abrupt change. The adaptability can be adjusted according to the shape of the installation position of the rectification skin.

Further, in step 2.4 and step 2.5, the mathematical definition of the NURBS curve is as follows:

p (K) is the position vector on the curve, N_i,m(K) Is a m-th order spline basis function;

wherein the mathematical definition of the basis functions is:

in the formula, Pi is a control point, Ri is a weight factor, and K is a node vector.

According to the construction method of the rectification skin, the approximate sections of the rectification skin are reversely constructed by utilizing the three-dimensional point cloud data of the installation position, and then the sections are subjected to multi-section sweeping, so that the skin digital model beneficial to assembly is obtained, the steps of pre-assembly and repeated repair and assembly of the skin in the traditional process are omitted, the installation efficiency of the wing body butt joint rectification skin is improved, and the skin installation method based on actual measurement data and high efficiency is realized. The NURBS curve has continuity and is constrained by the control vertex, so that the shape of the butt joint of the wing body can be well fitted, and the fairing skin obtained by fitting the butt joint shape of the wing body and the surrounding skin also meet certain continuity requirements, thereby ensuring the aerodynamic shape performance of the airplane.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.