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CN116740060B - Dimensional detection method of prefabricated components based on point cloud geometric feature extraction - Google Patents

Dimensional detection method of prefabricated components based on point cloud geometric feature extraction Download PDF

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CN116740060B
CN116740060B CN202311009724.8A CN202311009724A CN116740060B CN 116740060 B CN116740060 B CN 116740060B CN 202311009724 A CN202311009724 A CN 202311009724A CN 116740060 B CN116740060 B CN 116740060B
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point cloud
plane
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prefabricated components
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CN116740060A (en
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周思宇
叶小菁
吴仙俣
琚川徽
王华彬
李学俊
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Anhui University
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/0002Inspection of images, e.g. flaw detection
    • G06T7/0004Industrial image inspection
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/10Segmentation; Edge detection
    • G06T7/194Segmentation; Edge detection involving foreground-background segmentation
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/60Analysis of geometric attributes
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/70Determining position or orientation of objects or cameras
    • G06T7/73Determining position or orientation of objects or cameras using feature-based methods
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06VIMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00Arrangements for image or video recognition or understanding
    • G06V10/40Extraction of image or video features
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/10Image acquisition modality
    • G06T2207/10028Range image; Depth image; 3D point clouds
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/30Subject of image; Context of image processing
    • G06T2207/30108Industrial image inspection
    • G06T2207/30164Workpiece; Machine component
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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    • Y02P90/30Computing systems specially adapted for manufacturing

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Abstract

The invention discloses a method for detecting the size of an assembled prefabricated part based on the extraction of geometrical characteristics of point clouds, which comprises the steps of firstly, finely dividing the point cloud foreground and the background of the assembled prefabricated part based on normal vectors, so that the point cloud of the assembled prefabricated part is divided from the environmental background; then, after the geometric characteristics of the point cloud of the prefabricated part are extracted, fitting the edge line of the prefabricated part according to the geometric characteristics of the point cloud, and calculating according to the fitted edge line to obtain the size information of the prefabricated part; and finally, adding 3D text labels of the size information of the prefabricated parts under the point cloud visual interface. According to the method, the edge line is fitted and the characteristic points are extracted based on the segmentation result of the cloud data of the real measurement points of the prefabricated components, so that the size of the prefabricated components is calculated, the purpose of automatic size detection is achieved, the detection efficiency is improved, and meanwhile, the accuracy of size detection is guaranteed.

Description

Method for detecting size of prefabricated part based on point cloud geometric feature extraction
Technical Field
The invention relates to the field of assembly type building industry, in particular to an assembly type prefabricated part size detection method based on point cloud geometric feature extraction.
Background
The building is an important direction of development of the building industry, and is a building assembled by processing various types of building components in advance in a factory and then transporting the building components to a construction site through reliable connection. Compared with the existing cast-in-situ structure building, the cast-in-situ structure building has the advantages of large-scale production, high construction speed and low construction cost.
In an industrial construction prefabricated component production plant, a plurality of prefabricated components of different types are often produced according to the order requirements. In order to reduce the cost, the existing manufacturing enterprises generally adopt a mode that a plurality of types of components are produced by converting processes on the same production line. In production, different products have various technical categories, large operation process difference and complex index system. The assembled prefabricated components are large in size, various in types and complex in structure; this brings great difficulty to the design of the automated and intelligent technical scheme for the quality detection of the prefabricated components. In the existing automatic detection method, in the process of detecting the prefabricated components, the accuracy of a detection result is often difficult to meet the requirement, and even the detection result needs to be checked manually.
The existing quality detection methods are limited to human eye detection and steel ruler detection, the detection efficiency is low, the quality detection is easy to be influenced by human, and the quality detection result is required to be recorded by paper, so that the intelligent degree is low. The common component size detection and assembly modes all require a great deal of human intervention. Instruments such as a level gauge, a theodolite, a total station and the like can only observe a single point, the detection efficiency is low, and rapid and effective detection can not be carried out on multiple components and large-size components. Especially when measuring large components. In addition, factory-produced prefabricated components are susceptible to damage during transportation and assembly. In the manufacturing stage, the problems of component size errors, component position deviation, surface quality defects and the like may be caused by reasons of material problems, template manufacturing defects and the like.Existing 2The computer vision technology can automatically detect, but has large limitation, is easily influenced by shooting angles, and cannot visualize quality inspection results.
Disclosure of Invention
The invention aims to provide an assembled prefabricated part size detection method based on point cloud geometric feature extraction, which is used for fitting edge lines and extracting feature points based on a segmentation result of assembled prefabricated part real-point cloud data, further calculating the size of an assembled prefabricated part, realizing the purpose of automatic size detection of the assembled prefabricated part, improving the detection efficiency and ensuring the accuracy of size detection.
The technical scheme of the invention is as follows:
the method for detecting the size of the prefabricated part based on the point cloud geometric feature extraction specifically comprises the following steps:
(1) The method comprises the steps of carrying out segmentation on the point cloud foreground and the background of the prefabricated part based on the refinement of normal vector, so that the point cloud of the prefabricated part is segmented from the environment background;
(2) Extracting geometric features of the point cloud of the prefabricated part;
(3) Fitting the edge line of the prefabricated part according to the geometric characteristics of the point cloud of the prefabricated part, and calculating according to the fitted edge line to obtain the size information of the prefabricated part;
(4) 3 adding size information of prefabricated part under point cloud visualization interfaceText labels.
The specific mode for carrying out the point cloud foreground-background segmentation of the prefabricated component based on the normal vector refinement comprises the following steps:
s11, refining normal vector: traversing each point in the point cloud of the prefabricated component, acquiring adjacent point sets of each point, and calculating curvature change and normal difference between a normal vector of each point and a normal vector of a current point of any point in each adjacent point set; when the curvature change and the normal direction difference exceed the set threshold values, taking the curvature change and the normal direction difference as residual error items, constructing a linear equation set, and calculating an adjustment value of an algorithm vector by solving the linear equation set; updating the normal vector of the current point according to the adjustment value of the normal vector to obtain a refined normal vector, repeating the steps, iterating for a plurality of times to adjust and optimize the normal vector of each point until the preset iteration times are reached, outputting the optimized normal vector as a new normal vector, and orienting the new normal vector to realize the refinement of the normal vector;
s12, performing image segmentation based on region growth refined by normal vector, performing secondary region growth segmentation when segmentation is not complete, and passing through a threshold value based on the condition of over-segmentationThe plane segmentation method is used for circularly recursively acquiring the maximum bin of the over-segmentation result, and finally, the point cloud of the prefabricated component is segmented from the environment background.
The said threshold valueThe plane segmentation method specifically comprises the following steps:
a. establishing a plane model: randomly selecting three points in the point cloud data to establish an initial plane model;
b. single plane fitting: after a plane model is built and a fitting plane is built, calculating the distance between each point in the point cloud and the fitting plane, and counting the number of internal points;
c. multi-plane fitting: judging whether the current fitted plane model is reasonable or not according to the number of the internal points, and when the number of the internal points reaches a preset threshold value, considering that the current plane model is better to fit, and taking the current plane model as a final segmentation result; when the number of the inner points is insufficient, reconstructing the inner points into a new point cloud, and executing the steps on the new point cloudObtaining a new oneDividing the new division result with the step +.>And (3) comparing the segmentation results of the cells, and selecting the group with the largest surface element as the final segmentation result.
The specific mode for extracting the geometric features of the prefabricated part point cloud is edge extraction of the prefabricated part point cloud, and the specific steps are as follows:
point-to-pointNeighborhood point->Fitting the tangent plane by least squares, +.> =1,2,…,/>The method comprises the steps of carrying out a first treatment on the surface of the The general expression of the plane equation is shown in formula (1):
(1);
the least square equation corresponding to each neighborhood point is shown in formula (2):
(2);
i.e.(3);
Solving the equation of the above formula (3) to obtain parameters、/>And->Carrying out formula (1) and obtaining a plane equation;
point to PointNeighborhood point->Projection onto tangential plane, point->The projection point in the tangential plane is,/>And->The parametric equation of (2) is shown in the following formula (4):
(4);
will beSubstituting tangential plane equation to obtain +.>
(5);
Wherein,,、/>、/>、/>are constants in the tangential plane equation, and the projection point coordinates ++can be obtained by substituting the formula (5) into the formula (4)>
In dotsProjection points of +.>For starting point, & lt + & gt>Defining a vector for the endpoint +.>Wherein any vector is taken>The vector product of the vector and the normal vector of the tangential plane is calculated as a vector +.>Then sequentially finding the vector +.>Respectively and vector->Vector->Included angle->、/>When->Included angle->The value of (2) is replaced by->The method comprises the steps of carrying out a first treatment on the surface of the For formula (6)>Sorting, selecting the maximum +.>As maximum angle->
(6);
Comparing adjacent two vectorsMaximum included angle->With the magnitude of the set angle threshold, when the maximum included angle +>If the angle is larger than the set angle threshold, then the point +.>Added to the set of boundary points.
The fitting of the edge line of the prefabricated part is to fit a straight line in the boundary point set by randomly selecting a group of points, and evaluate the fitting effect by calculating the distance from other points to the straight line.
When the edge of one plane of the prefabricated component is rectangular, grouping the edge straight lines through the geometric features of the straight lines when fitting the edge lines, and then selecting a group of points after grouping to fit the straight lines.
The fitting of the edge line of the prefabricated part is to perform a straight line fitting algorithm for a plurality of times, so that all boundary points of the plane of the prefabricated part are fitted, and a plurality of fitting straight lines are obtained; calculating the size of the prefabricated part, namely calculating the distance between every two fitting straight lines, and obtaining the size information of the prefabricated part by solving the shortest distance between the two fitting straight lines; comparing the calculated size information of the prefabricated part with the size of the standard prefabricated part, namely calculating by the formula (7) to obtain measurement accuracy
(7);
In the formula (7), the amino acid sequence of the compound,for the dimensional information of prefabricated components of the assembly type, +.>Is the size of a standard prefabricated part.
The invention has the advantages that:
(1) According to the method for detecting the size of the prefabricated part based on the point cloud geometric feature extraction, which is provided by the invention, the point cloud segmentation part provides a method for segmenting the point cloud foreground and the background of the prefabricated part based on the normal vector refinement, and the image segmentation is performed based on the region growth of the normal vector refinement, so that the accuracy of segmenting the point cloud foreground and the background is improved, and better initial data is provided for the automatic size detection of the subsequent prefabricated part.
(2) When the geometric features of the point cloud of the prefabricated component are extracted, the boundary feature extraction algorithm based on the normal line improved by the search strategy is adopted, and the boundary feature extraction algorithm based on the normal line improved by the search strategy is implemented by comparing one point with the neighborhood point thereofVector included angle projected in tangential plane to judge whether the point is boundary point or not, the search strategy improvement means that the radius of normal calculation is searched and calculatedThe combination of neighbor searches becomes a hybrid search, thereby balancing the search speed and accuracy; compared with the traditional edge feature extraction algorithm, the method has higher detection precision, is more flexible in detection mode for components with different shapes, breaks the bottleneck of traditional detection, and enables quality detection to be paperless, intelligent and visual.
(3) The invention is based on 3Visual technique, 2->Vision means that by taking a picture of a plane with a camera and then identifying the object by image analysis or comparison, the features on the object plane can be seen, which can be used for absence/presence detection, and 3Visually acquired data are mainly 3 +.>The three-dimensional point cloud data collected by the sensor not only can sense whether the components exist in the scene, but also can accurately detect the size and the position orientation of the components, and the detection data is more comprehensive and accurate.
Detailed Description
The following description will clearly and fully describe the technical solutions of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The method for detecting the size of the prefabricated part based on the point cloud geometric feature extraction specifically comprises the following steps:
(1) And the point cloud foreground and the background of the prefabricated component are segmented based on the refinement of the normal vector, so that the point cloud of the prefabricated component is segmented from the environment background (prefabricated factory), and the specific mode is as follows:
s11, refining normal vector: traversing each point in the point cloud of the prefabricated component, acquiring adjacent point sets of each point, and calculating curvature change and normal difference between a normal vector of each point and a normal vector of a current point of any point in each adjacent point set; when the curvature change and the normal direction difference exceed the set threshold values, taking the curvature change and the normal direction difference as residual error items, constructing a linear equation set, and calculating an adjustment value of an algorithm vector by solving the linear equation set; updating the normal vector of the current point according to the adjustment value of the normal vector to obtain a refined normal vector, repeating the steps, iterating for a plurality of times to adjust and optimize the normal vector of each point until the preset iteration times are reached, outputting the optimized normal vector as a new normal vector, and orienting the new normal vector to realize the refinement of the normal vector;
s12, performing image segmentation based on region growth refined by normal vector, performing secondary region growth segmentation when segmentation is not complete, and passing through a threshold value based on the condition of over-segmentationThe plane segmentation method comprises the steps of circularly recursively obtaining the maximum bin of an over-segmentation result, and finally, segmenting the point cloud of the prefabricated component from an environmental background;
wherein, based on threshold valueThe plane segmentation method specifically comprises the following steps:
a. establishing a plane model: randomly selecting three points in the point cloud data to establish an initial plane model;
b. single plane fitting: after a plane model is built and a fitting plane is built, calculating the distance between each point in the point cloud and the fitting plane, and counting the number of internal points;
c. multi-plane fitting: judging whether the current fitted plane model is reasonable or not according to the number of the internal points, and when the number of the internal points reaches a preset threshold value, considering that the current plane model is better to fit, and taking the current plane model as a final segmentation result; when the number of the inner points is insufficient, reconstructing the inner points into a new point cloud, and executing the steps on the new point cloudObtaining a new segmentation result, and combining the new segmentation result with the step +.>Comparing the segmentation results of the (a), and selecting a group with the largest surface element as a final segmentation result;
(2) Extracting geometric features of the point cloud of the prefabricated part, wherein the specific mode is edge extraction of the point cloud of the prefabricated part, and the specific steps are as follows:
point-to-pointNeighborhood point->Fitting the tangent plane by least squares, +.> =1,2,…,/>The method comprises the steps of carrying out a first treatment on the surface of the The general expression of the plane equation is shown in formula (1):
(1);
the least square equation corresponding to each neighborhood point is shown in formula (2):
(2);
i.e.(3);
Solving the equation of the above formula (3) to obtain parameters、/>And->Carrying out formula (1) and obtaining a plane equation;
point to PointNeighborhood point->Projection onto tangential plane, point->The projection point in the tangential plane is,/>And->The parametric equation of (2) is shown in the following formula (4):
(4);
will beSubstituting tangential plane equation to obtain +.>
(5);
Wherein,,、/>、/>、/>are constants in the tangential plane equation, and the projection point coordinates ++can be obtained by substituting the formula (5) into the formula (4)>
In dotsProjection points of +.>For starting point, & lt + & gt>Defining a vector for the endpoint +.>Wherein any vector is taken>The vector product of the vector and the normal vector of the tangential plane is calculated as a vector +.>Then sequentially finding the vector +.>Respectively and vector->Vector->Included angle->、/>When->Included angle->The value of (2) is replaced by->The method comprises the steps of carrying out a first treatment on the surface of the For formula (6)>Sorting, selecting the maximum +.>As maximum angle->
(6);
Comparing adjacent two vectorsMaximum included angle->With the magnitude of the set angle threshold, when the maximum included angle +>If the angle is larger than the set angle threshold, then the point +.>Adding the boundary points into the boundary point set;
(3) Fitting the edge line of the prefabricated part according to the geometric characteristics of the point cloud of the prefabricated part, and calculating according to the fitted edge line to obtain the size information of the prefabricated part;
fitting of the edge lines of the prefabricated part is that a plurality of edge lines are fitted simultaneously: fitting straight lines by randomly selecting a group of points in the boundary point set, fitting all boundary points of the plane of the prefabricated part by executing a straight line fitting algorithm for a plurality of times, thereby obtaining a plurality of fitting straight lines, calculating the distance between every two fitting straight lines, obtaining the size information of the prefabricated part by solving the shortest distance between the two fitting straight lines, comparing the calculated size information of the prefabricated part with the size of a standard prefabricated part, namely obtaining the measurement precision by calculating according to a formula (7)
(7);
In the formula (7), the amino acid sequence of the compound,for the dimensional information of prefabricated components of the assembly type, +.>Is the size of a standard prefabricated part;
when the edge of one plane of the prefabricated component is rectangular, grouping the edge straight lines through geometric features (such as the start point, the end point, the direction vector and the like of the straight lines) of the straight lines when fitting the edge lines, and then selecting a group of points after grouping to fit the straight lines;
(4) 3 adding size information of prefabricated part under point cloud visualization interfaceText labels.
In order to verify the validity of the invention, the embodiment adopts an experimental method to verify the validity and accuracy of the size detection method of the assembled prefabricated part, and the specific experimental process comprises the following steps: the method comprises the steps of segmenting a foreground and a background of a component point cloud, extracting geometric features of the component point cloud, and automatically detecting the size and displaying a detection result.
1. Component point cloud foreground and background segmentation:
the improved effect of the experimental algorithm is that the indoor data set is disclosedAnd (3) performing verification, wherein two six classes of boxes, stacked boxes, shielding objects, cylindrical objects, mixed objects and complex scenes are selected. Through experiments, the invention has good accuracy and recall rate in object segmentation.
2. Extracting geometric features of component point clouds:
the embodiment mainly adopts the traditional technologyThe algorithm, the traditional boundary feature extraction algorithm based on the normal and the boundary feature extraction algorithm based on the normal with improved search strategy are compared, so that the effectiveness of the invention is embodied. By carrying out experiments on point clouds of 14 members with different shapes, compared with other two algorithms, the algorithm provided by the invention has the greatest number of extracted effective boundary points.
3. Automated size detection:
the experiment is to model six different types of components (the numbers are respectively、/>、/>、/>、/>) Wherein->、/>、/>The length is the same as that of the real component, belonging to the qualified component, < ->、/>Setting an error of +5mm, < > on the real member>Setting error-1 mm. Tests were performed on six different types of components to determine if the invention is able to accurately detect if the dimensions of the components meet quality standards. To further verify the accuracy of the dimensions of the detection member of the present invention, the experiment was divided into three steps:
(1) And verifying the influence of the distance for acquiring the point cloud data on the experimental result. Express boxes (150 mm×290 mm) similar to the shape of the members were measured at different distances, and the experimental results are shown in table 1 below:
table 1 error table of measured data for different distances
(2) The error of the collected point cloud is about 2mm within the distance range of 600mm-1600mm, which is obtained from the above table 1, and the measurement is performedThe precision reaches 98 percent. Thus, 1400mm was chosen as the reference distance when the component point cloud was acquired. Reference to national standard1, allowing deviation of the size of the prefabricated part to be +/-5 mm, adding a risk assessment mechanism, setting the deviation to be low risk within the range of 1mm, and considering the deviation to be qualified without taking any measures; setting the deviation within the range of 1-3mm as a stroke risk, considering that the deviation is possibly unqualified, and suggesting a secondary spot check of a quality inspector; for deviations in the range of 3-5mm, setting the deviation as a high risk, considering that the deviation is high in possibility of failure, releasing warning, and reminding a quality inspector to focus on manual rechecking of the components.
(3)、、/>And->The component is detected as a qualified component,>and->The component is at high risk and needs to be re-checked manually for the second time,/->The component is a medium risk, and the sampling inspection is reminded to be performed again.
After comparing with the manual recheck, the invention meets the quality inspection standard in the detection accuracy of the yard in the factory or outside the factory, realizes the preliminary screening work of the quality detection link, realizes the automation, improves the detection efficiency and ensures the detection accuracy.
Because the number of the point clouds is large, the time is too long when the edge extraction is carried out, and the down-sampling treatment is carried out on the point clouds by adopting an octree sampling method, so that the edge extraction time is reduced, and the efficiency is improved.
4. And (3) displaying a detection result:
selecting an area needing size detection from the point cloud object, selecting a marked point in the area, visualizing the point cloud by using a visualization tool, selecting the marked point by means of mouse interaction and the like, correlating the detected size information with the point cloud data, and displaying the size information at the marked point.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (5)

1.基于点云几何特征提取的装配式预制构件尺寸检测方法,其特征在于:具体包括有以下步骤:1. The dimension detection method of prefabricated components based on point cloud geometric feature extraction is characterized by: specifically including the following steps: (1)、基于法向量精细化进行装配式预制构件点云前景和背景的分割,使得装配式预制构件的点云从环境背景中分割出来;(1) Segment the foreground and background of the prefabricated component point cloud based on normal vector refinement, so that the point cloud of the prefabricated component is segmented from the environmental background; 所述的基于法向量精细化进行装配式预制构件点云前景和背景的分割的具体方式为:The specific method of segmenting the foreground and background of the point cloud of prefabricated components based on normal vector refinement is as follows: S11、法向量精细化:遍历装配式预制构件点云中的每个点,对于每个点,获取其相邻点集合,然后对于每个相邻点集合中的任一点,计算其法向量与当前点法向量之间的曲率变化和法向量差异;当曲率变化和法向量差异超过设定的阈值,则将其作为残差项,构建线性方程组,通过求解线性方程组计算法向量的调整值;根据法向量的调整值,更新当前点的法向量,得到精细化后的法向量,最后重复以上步骤,多次迭代进行每个点法向量的调整优化,直到达到预定的迭代次数后,输出优化后的法向量作为新法向量,并对新法向量进行定向,实现法向量精细化;S11. Normal vector refinement: Traverse each point in the point cloud of prefabricated components. For each point, obtain its adjacent point set, and then for any point in each adjacent point set, calculate its normal vector and The curvature change and normal vector difference between the current point normal vectors; when the curvature change and the normal vector difference exceed the set threshold, it is used as a residual term to construct a linear equation system, and the adjustment of the normal vector is calculated by solving the linear equation system value; according to the adjustment value of the normal vector, update the normal vector of the current point to obtain the refined normal vector. Finally, repeat the above steps and adjust and optimize the normal vector of each point in multiple iterations until the predetermined number of iterations is reached. Output the optimized normal vector as a new normal vector, and orient the new normal vector to achieve normal vector refinement; S12、基于法向量精细化的区域生长进行图像分割,当没有分割完全,则进行二次区域生长分割,当存在过分割的情况时,再通过基于阈值的RANSAC平面分割方法,循环递归获取过分割结果的最大面元,最后使得装配式预制构件的点云从环境背景中分割出来;S12. Image segmentation is performed based on region growing with normal vector refinement. When the segmentation is not complete, secondary region growing segmentation is performed. When there is over-segmentation, the threshold-based RANSAC plane segmentation method is used to obtain the over-segmentation recursively. The maximum bin of the result finally enables the point cloud of the prefabricated components to be segmented from the environmental background; (2)、提取装配式预制构件点云的几何特征,具体方式为装配式预制构件点云的边缘提取,具体步骤如下:(2) Extract the geometric features of the prefabricated component point cloud. The specific method is edge extraction of the prefabricated component point cloud. The specific steps are as follows: 对点及邻域点/>用最小二乘法拟合切平面,/>,2,…,k;平面方程的一般表达式见式(1)所示:Right point and neighborhood points/> Use the least squares method to fit the tangent plane,/> ,2,…,k; the general expression of the plane equation is shown in equation (1): (1); (1); k个邻域点对应的最小二乘方程见式(2):The least squares equation corresponding to k neighborhood points is shown in Equation (2): (2); (2); (3);Right now (3); 解上式(3)的方程,得到参数、/>和/>,带入式(1),求得平面方程;Solve the equation of equation (3) above to get the parameters ,/> and/> , put into equation (1) to obtain the plane equation; 将点及邻域点/>向切平面投影,点/>在切平面中的投影点为,/>和/>的参数方程如下式(4)所示:Check point and neighborhood points/> Projection to tangent plane, point/> The projection point in the tangent plane is ,/> and/> The parametric equation of is shown in the following equation (4): (4); (4); 代入切平面方程,得到t:Will Substituting into the tangent plane equation, we get t: (5); (5); 其中,A、B、C、D均为切平面方程中的常数,将式(5)代入式(4)即可求出投影点坐标Among them, A, B, C, and D are all constants in the tangent plane equation. By substituting equation (5) into equation (4), the coordinates of the projection point can be obtained. ; 以点的投影点/>为起始点、/>为终点定义向量/>,在其中任取一向量/>,求其与切平面法向量的向量积设为向量v,再依次求出向量/>分别与向量/>及向量v的夹角/>、/>,当/>,则夹角/>的取值替换为/>;对式(6)求得的/>进行排序,选出其中最大的/>作为最大夹角/>point projection point/> is the starting point,/> Define a vector for the end point/> , pick any vector/> , find the vector product with the normal vector of the tangent plane, set it as vector v, and then find the vector/> respectively with vector/> and the angle between vector v/> ,/> , when/> , then the included angle/> The value of is replaced by/> ; Obtained from equation (6)/> Sort and select the largest one/> As the maximum included angle/> ; (6); (6); 比较相邻两个向量间的最大夹角/>与设定的角度阈值的大小,当最大夹角大于设定的角度阈值时,则该点/>加入到边界点集中;Compare two adjacent vectors The maximum angle between and the set angle threshold, when the maximum angle When it is greater than the set angle threshold, then the point/> Add to the set of boundary points; (3)、根据装配式预制构件点云的几何特征,进行装配式预制构件边缘线的拟合,再根据拟合的边缘线计算得到装配式预制构件的尺寸信息;(3) According to the geometric characteristics of the point cloud of the prefabricated components, fit the edge lines of the prefabricated components, and then calculate the size information of the prefabricated components based on the fitted edge lines; (4)、在点云可视化界面下添加装配式预制构件尺寸信息的3D文字标签。(4) Add 3D text labels with dimensional information of prefabricated components in the point cloud visualization interface. 2.根据权利要求1所述的基于点云几何特征提取的装配式预制构件尺寸检测方法,其特征在于:所述的基于阈值的RANSAC平面分割方法具体包括有以下步骤:2. The size detection method of prefabricated components based on point cloud geometric feature extraction according to claim 1, characterized in that: the threshold-based RANSAC plane segmentation method specifically includes the following steps: a、建立平面模型:在点云数据中随机选取三个点建立初始的平面模型;a. Establish a plane model: randomly select three points in the point cloud data to establish an initial plane model; b、单平面拟合:在建立平面模型并构建拟合平面后,计算点云中每个点到拟合平面的距离,并统计内点数量;b. Single plane fitting: After establishing the plane model and constructing the fitting plane, calculate the distance from each point in the point cloud to the fitting plane, and count the number of internal points; c、多平面拟合:根据内点的数量,判断当前拟合的平面模型是否合理,当内点数量达到预设的阈值,即认为当前平面模型拟合较好,将其作为最终的分割结果;当内点数量不足,则将内点重新组成新的点云,并对新的点云执行步骤b,得到一个新的分割结果,将新的分割结果与步骤b的分割结果进行比较,选择面元最大的一组作为最终分割结果。c. Multi-plane fitting: Based on the number of interior points, determine whether the currently fitted plane model is reasonable. When the number of interior points reaches the preset threshold, the current plane model is considered to have a good fit and will be used as the final segmentation result. ; When the number of interior points is insufficient, reorganize the interior points into a new point cloud, perform step b on the new point cloud, and obtain a new segmentation result. Compare the new segmentation result with the segmentation result of step b, and select The largest group of bins is used as the final segmentation result. 3.根据权利要求1所述的基于点云几何特征提取的装配式预制构件尺寸检测方法,其特征在于:所述的装配式预制构件边缘线的拟合是在边界点集中通过随机选择一组点来拟合直线,并通过计算其它点到该直线的距离来评估拟合效果。3. The size detection method of prefabricated components based on point cloud geometric feature extraction according to claim 1, characterized in that: the fitting of the edge lines of prefabricated components is performed by randomly selecting a group of boundary points. Points are used to fit a straight line, and the fitting effect is evaluated by calculating the distances from other points to the straight line. 4.根据权利要求3所述的基于点云几何特征提取的装配式预制构件尺寸检测方法,其特征在于:所述的装配式预制构件其中一平面的边缘为矩形时,在拟合边缘线时,通过直线的几何特征,进行边缘直线的分组,然后选择分组后的一组点来拟合直线。4. The size detection method of prefabricated components based on point cloud geometric feature extraction according to claim 3, characterized in that: when the edge of one plane of the prefabricated component is a rectangle, when fitting the edge line , group the edge straight lines through the geometric characteristics of the straight lines, and then select a group of grouped points to fit the straight lines. 5.根据权利要求3所述的基于点云几何特征提取的装配式预制构件尺寸检测方法,其特征在于:所述的装配式预制构件边缘线的拟合是通过多次执行直线拟合算法,使得装配式预制构件平面的所有边界点都被拟合,从而得到多条拟合直线;计算装配式预制构件的尺寸是对于每两条拟合直线,计算它们之间的距离,通过求解两条拟合直线之间的最短距离得到装配式预制构件的尺寸信息;将计算得到的装配式预制构件的尺寸信息与标准预制构件的尺寸进行对比,即通过式(7)计算得到测量精度E:5. The size detection method of prefabricated components based on point cloud geometric feature extraction according to claim 3, characterized in that: the fitting of the edge line of prefabricated components is by executing a straight line fitting algorithm multiple times, All boundary points of the prefabricated component plane are fitted, thereby obtaining multiple fitting straight lines; the size of the prefabricated prefabricated component is calculated by calculating the distance between them for each two fitting straight lines. The shortest distance between the fitting straight lines is used to obtain the dimensional information of the prefabricated components; the calculated dimensional information of the prefabricated components is compared with the size of the standard prefabricated components, that is, the measurement accuracy E is calculated through equation (7): (7); (7); 式(7)中,为装配式预制构件的尺寸信息,/>为标准预制构件的尺寸。In formula (7), Dimensional information for prefabricated components,/> are the dimensions of standard prefabricated components.
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