Wall panel through-hole ratio detection method based on 3D point cloud data feature extraction

Abstract

The present invention discloses a method for detecting the through-hole rate of composite wall panels based on feature extraction of three-dimensional point cloud data, which belongs to the technical field. The method comprises: obtaining the center of the hole to be measured; obtaining the curvature calculation point of the hole to be measured; calculating the hole center curvature of the hole to be measured based on the curvature calculation point of the hole to be measured; calculating the hole normal vector based on the comprehensive curvature of the hole center point; using the coordinates of the hole center point as the search starting point, the hole normal vector as the search direction, setting the search distance to a certain value m, and setting the searched point cloud as the hole bottom data; if there is no hole bottom point cloud data or the calculated distance is greater than the set threshold h, the hole is considered to be a through hole; if the calculated distance is less than the set threshold h, the hole is a blocked hole; and calculating the through-hole rate. The method of the present invention calculates the through-hole rate based on the feature extraction of three-dimensional point cloud data of micro-array holes in composite wall panels, providing support for the accurate acquisition of the surface normal vector of the curved hole, and further providing support for the through-hole rate calculation.

Description

Technical Field

[0001] The present invention relates to a method for detecting the through-porosity of a composite wall panel, and in particular to a method for detecting the through-porosity of a composite wall panel based on feature extraction of three-dimensional point cloud data. Background Art

[0002] Composite materials, with their excellent properties such as high strength, high temperature resistance, corrosion resistance, and light weight, are widely used in aviation manufacturing. Panels are the most commonly used component in composite materials, and their machining accuracy is a key performance indicator in aircraft manufacturing. The machining of composite panel parts primarily involves contouring and hole-making. To meet aircraft performance requirements, thousands of tiny array holes must be produced in a composite panel per week. The through-hole ratio, or the ratio of the through-hole area to the total area of the panel, is a key metric for detecting these tiny array holes.

[0003] Laser scanning offers advantages such as non-contact and high-speed measurement for measuring through-porosity. However, the extraction of features from the three-dimensional point cloud data of micro-array holes in composite wall panels and the calculation of through-porosity remain unresolved. To address this issue, this paper proposes a method for extracting features from the three-dimensional point cloud data of micro-array holes in composite wall panels and calculating through-porosity. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned problems existing in the prior art and proposes a method for detecting the through-porosity of composite wall panels based on feature extraction of three-dimensional point cloud data. By calculating the comprehensive curvature of the surface, the surface normal vector is accurately obtained, and support is provided for the calculation of the through-porosity.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0006] A method for detecting through-porosity of composite wall panels based on feature extraction of three-dimensional point cloud data is characterized by comprising the following steps:

[0007] Step S1, obtaining the center P of the hole to be measured;

[0008] Step S2, obtaining the curvature calculation point of the measured hole;

[0009] Step S3, calculating the center curvature of the measured hole according to the curvature calculation point of the measured hole;

[0010] Step S4: Calculate the hole normal vector based on the comprehensive curvature of the hole center point P;

[0011] Step S5: Use the coordinates of the hole center point P as the search starting point, the hole normal vector as the search direction, and the search distance set to a certain value m, m≤1 / 5h, where h is the hole depth determination threshold. The searched point cloud is set as the hole bottom data; if there is no hole bottom point cloud data or the calculated distance is greater than the set threshold h, the hole is considered to be a through hole; if the calculated distance is less than the set threshold h, the hole is considered to be a blocked hole;

[0012] Step S6: Calculate the through-hole ratio t=N1 / N, where N is the total number of holes and N1 is the number of through holes.

[0013] Furthermore, in step S1, the hole center P is obtained by fitting based on the point cloud data.

[0014] Furthermore, in step S2, a circle is drawn with the hole center P as the center and R+d as the radius, the intersection A of the circle and the radial direction W of the wall panel is taken, the line is extended to intersect the other side of the circle as C, a perpendicular line to the line is taken through the hole center P, the intersection points of the perpendicular line and the circle are points B and D, and the four points A, B, C, and D are used as the curvature calculation points of the hole; where R is the theoretical value of the aperture, and d=1 / 3R.

[0015] Furthermore, in step S3, the curvatures of the four points A, B, C, and D are obtained respectively. The calculation method is as follows: a plane passing through the normal line of the point intersects with the surface to obtain a two-dimensional curve, which is a normal section of the surface. The curvature of any angle i passing through the surface is calculated to obtain the curvature Ki of each curve, and the maximum and minimum curvatures are taken respectively:

[0016] Kmax=Max(Ki);

[0017] Kmin=Min(Ki).

[0018] Calculate the curvature of A, B, C, and D respectively: K=1 / 2(Kmax+Kmin).

[0019] Furthermore, the comprehensive curvature of point P is defined as K P =1 / 2(K A 2 + K B 2 + K C 2 + K D 2 ) 1 / 2 , calculate the comprehensive curvature of point P.

[0020] In summary, the present invention has the following advantages:

[0021] The method of the present invention calculates the through-porosity based on the feature extraction of three-dimensional point cloud data of tiny array holes in composite wall panels, provides support for the accurate acquisition of the normal vector of the curved surface, and further provides support for the through-porosity calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the hardware for testing the through-hole rate of composite wall panels;

[0023] Figure 2 Schematic diagram of composite wall panel parts;

[0024] Figure 3 This is a schematic diagram for calculating the hole center normal vector;

[0025] Figure 4 Schematic diagram for judging the depth of through-hole. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0027] Example 1

[0028] The present invention provides a method for detecting the through-porosity of composite wall panels based on feature extraction of three-dimensional point cloud data. Figure 1 The following is a schematic diagram of the detection hardware, which includes the following steps:

[0029] Step S1, obtaining the center P of the hole to be measured;

[0030] Step S2, obtaining the curvature calculation point of the measured hole;

[0031] Step S3, calculating the center curvature of the measured hole according to the curvature calculation point of the measured hole;

[0032] Step S4: Calculate the hole normal vector based on the comprehensive curvature of the hole center point P;

[0033] Step S5: Use the coordinates of the hole center point P as the search starting point, the hole normal vector as the search direction, and the search distance set to a certain value m, m≤1 / 5h, where h is the hole depth determination threshold. The searched point cloud is set as the hole bottom data; if there is no hole bottom point cloud data or the calculated distance is greater than the set threshold h, the hole is considered to be a through hole; if the calculated distance is less than the set threshold h, the hole is considered to be a blocked hole;

[0034] Step S6: Calculate the through-hole ratio t=N1 / N, where N is the total number of holes and N1 is the number of through holes.

[0035] Example 2

[0036] The present invention provides a method for detecting the through-porosity of a composite wall panel based on feature extraction of three-dimensional point cloud data, comprising the following steps:

[0037] Step S1: Obtain the center of the hole to be measured. According to the point cloud data, the hole center P is fitted.

[0038] Step S2: Get the curvature calculation point. Figure 2 and Figure 3 As shown, a circle is constructed with the hole center P as the center and the radius R+d as the radius. The intersection of this circle and the wall plate radius W is point A. Extend this line to intersect the other side of the circle at point C. A perpendicular line to this line intersects the circle at points B and D. These four points are used as the calculation points for the hole curvature. R is the theoretical aperture diameter, and d = 1 / 3R.

[0039] Step S3: Calculate the hole center curvature. Take the curvatures of points A, B, C, and D respectively. The calculation method is to intersect the surface with a plane whose normal passes through the point to obtain a two-dimensional curve, which is a normal section of the surface. Calculate the curvature of any angle i passing through the surface to obtain the curvature Ki of each curve, and take its maximum and minimum curvatures respectively:

[0040] Kmax=Max(Ki);

[0041] Kmin=Min(Ki).

[0042] Calculate the curvature of A, B, C, and D respectively: K=1 / 2(Kmax+Kmin). Define the comprehensive curvature of point P as K P =1 / 2(K A 2 +K B 2 + K C 2 + K D 2 ) 1 / 2 , calculate the comprehensive curvature of point P.

[0043] Step S4: Calculate the aperture normal vector. According to the comprehensive curvature of point P, calculate the aperture normal vector.

[0044] Step S5: Through-hole determination. Set the circle center coordinate P as the search starting point, the hole normal vector as the search direction, and the search distance to a certain value m, where m≤1 / 5h, where h is the hole depth determination threshold. Set the searched point cloud as the hole bottom data.

[0045] like Figure 4 As shown in FIG, if there is no point cloud data of the hole bottom or the calculated distance is greater than the set threshold h, the hole is considered to be a through hole; if the calculated distance is less than the set threshold h, the hole is considered to be a blocked hole.

[0046] Step S6: Calculate the number of through holes N1 and the total number of holes N, and the through hole rate is t=N1 / N.

[0047] Although the specific embodiments of the present invention are described in detail in conjunction with the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for detecting the through-porosity of composite wall panels based on feature extraction of three-dimensional point cloud data, characterized in that: The steps include: Step S1, obtaining the center P of the hole to be measured; Step S2, obtaining the curvature calculation points of the measured hole: draw a circle with the hole center P as the center and R+d as the radius, take the intersection point A of the circle and the wall plate radius direction W, extend the line and intersect the other side of the circle to point C, take a perpendicular line through the hole center P to the line, and the intersection points of the perpendicular line and the circle are points B and D, and use points A, B, C, and D as the curvature calculation points of the hole; where R is the theoretical value of the hole diameter, and d=1 / 3R; Step S3, calculate the center curvature of the measured hole according to the curvature calculation point of the measured hole: obtain the curvatures of the four points A, B, C, and D respectively, and the calculation method is as follows: according to the intersection of a plane passing through the normal line of the point with the curved surface, a two-dimensional curve is obtained, that is, a normal section of the curved surface, and the curvature of any angle i passing through the curved surface is calculated to obtain the curvature Ki of each curve, and the maximum curvature and minimum curvature are taken respectively: Kmax=Max(Ki); Kmin=Min(Ki); Calculate the curvature of points A, B, C, and D respectively: K=1 / 2(Kmax+Kmin); Step S4: Define the comprehensive curvature of point P as K P =1 / 2(K A 2 + K B 2 + K C 2 + K D 2 ) 1 / 2 , K P Indicates the curvature of the measured point P, K A , K B , K C , K D Respectively represent the curvatures of the extracted points A, B, C, and D; the hole normal vector is calculated based on the comprehensive curvature of the hole center point P; Step S5: Use the coordinates of the hole center point P as the search starting point, the hole normal vector as the search direction, and the search distance set to a certain value m, m≤1 / 5h, where h is the hole depth determination threshold. The searched point cloud is set as the hole bottom data; if there is no hole bottom point cloud data or the calculated distance is greater than the set threshold h, the hole is considered to be a through hole; if the calculated distance is less than the set threshold h, the hole is considered to be a blocked hole; Step S6, calculating the through-hole ratio t=N1 / N, where N is the total number of holes and N1 is the number of through holes.

2. The method for detecting through-porosity of composite wall panels based on three-dimensional point cloud data feature extraction according to claim 1, characterized in that: In step S1, the hole center P is obtained by fitting based on the point cloud data.

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