Prefabricated small box girder bridge position virtual combination installation method and equipment

Abstract

The invention discloses a prefabricated small box girder bridge position virtual combination installation method. The method comprises the steps that a prefabricated small box girder to be installed is registered with a mold; gridding the contact surfaces of the prefabricated small box girder, extracting a plane equation and a normal vector of the two contact surfaces when the prefabricated small box girder is in contact with a support, and determining an initial mounting position; pre-stress hole characteristics of the small prefabricated box girders are extracted, the circle centers of the holes are used as characteristic points, and the two sets of small prefabricated box girders extending front and back are subjected to longitudinal extending virtual installation; extracting plane equations and normal vectors of the longitudinal extension surfaces and the top surfaces of the prefabricated small box girders, and performing transverse extension virtual installation on the two groups of prefabricated small box girders which extend left and right; the mounting positions of the previous small prefabricated box girder and the support are kept unchanged, the horizontal plane position of the next small prefabricated box girder is subjected to various follow-up changes, the contact area is calculated, and the final mounting position is determined; and the small box beam bridge position virtual combination installation equipment is prefabricated. The method has the advantages of being capable of achieving full-automatic virtual installation of the prefabricated small box girder, high in precision and the like.

Description

Technical Field

[0001] The present invention relates to the field of virtual installation of box girders. More specifically, the present invention relates to a method and device for virtual combined installation of precast small box girders at the bridge site. Background Art

[0002] Using the point cloud data of small box girders obtained by three-dimensional laser scanning technology for virtual installation can not only effectively improve the installation accuracy at the construction site, but also comprehensively improve the construction quality of the entire project. However, in the prior art, most of them use software such as Revit and SCENE to reverse model the point cloud data of various complex small box girder components, and realize pre-assembly with the help of Building Information Modeling (BIM), or perform point cloud modeling based on target splicing to complete virtual assembly. Such prior art solutions generally involve reverse engineering, which requires the use of a variety of professional software to model and convert the format of the point cloud, and highly relies on the BIM model. In the process of manually selecting points for the point cloud splicing control points, the subjectivity is relatively large, resulting in difficult to effectively control the accuracy. And when there are deficiencies in the scanned point cloud quality, it is difficult to accurately install the small box girder components. Summary of the Invention

[0003] An object of the present invention is to provide a method and device for virtual combined installation of precast small box girders at the bridge site to at least solve the above problems.

[0004] To achieve the object and other advantages of the present invention, a method for virtual combined installation of precast small box girders at the bridge site is provided, including: S1. Register the precast small box girders to be installed with the precast small box girder mold to obtain precast small box girders meeting the accuracy requirements; S2. Perform meshing on the contact surface of the precast small box girders, extract the plane equations and normal vectors of the two contact surfaces when the precast small box girders contact the bearing. When the normal vectors of the two contact surfaces are the same, align any grid intersection point after meshing with the center of the bearing, calculate the average distance from all points in the point cloud of the bearing contact surface to the fitting plane of the precast small box girder contact surface, traverse all grid intersection points, and use the grid intersection point when the average distance is the smallest as the initial installation position of the precast small box girder and the bearing;

[0005] S3. Extract the prestressed hole features on the longitudinal extension surfaces of two groups of precast small box girders that are extended forward and backward in sequence, perform feature matching with the centers of the prestressed holes as feature points, and perform longitudinal extension virtual installation on two groups of precast small box girders that are extended forward and backward in sequence; S4. Keep the installation position of the precast small box girder in front unchanged during the extended virtual installation, perform various extension changes on the horizontal plane position of the precast small box girder behind, calculate the contact area between the precast small box girder after the extension change and the bearing, traverse all extended change positions, and use the horizontal plane position of the precast small box girder when the contact area is the largest as the final installation position of the precast small box girder and the bearing.

[0006] Preferably, the virtual combined installation method for precast small box girder bridge positions further includes: S5. Respectively extract the plane equations and normal vectors of the longitudinally extended surfaces and top surfaces of two groups of precast small box girders that extend left and right, so that the normal vectors of the planes where the longitudinally extended surfaces of the two groups of precast small box girders that extend left and right are linearly correlated, and the normal vectors of the planes where the top surfaces are located are parallel. Perform transverse extension virtual installation on the two groups of precast small box girders that extend left and right.

[0007] Preferably, in S1, after denoising and downsampling the point cloud of the precast small box girder to be installed and the point cloud of the precast small box girder mold, use the initial registration algorithm based on sampling consistency for registration.

[0008] Preferably, in S2, perform meshing on the contact surface of the precast small box girder, including: Denote the center of the bearing contact surface as a(x, y, z), the radius as r, and the distance from the center a to the maximum deviation boundary within the allowable deviation range of the installation range as R, R>r. Use the circular surface corresponding to the center a and the radius R as the contact surface of the precast small box girder. Select any three points on the contact surface of the precast small box girder as a plane, and perform two-dimensional meshing on the contact surface of the precast small box girder.

[0009] Preferably, in S2, extract the plane equations and normal vectors of the two contact surfaces when the precast small box girder contacts the bearing, including: Respectively take any two points on the bearing contact surface and the precast small box girder contact surface, and use the RANSAC algorithm to fit a straight line with the extracted any two points and continuously iterate to obtain the plane equations and normal vectors of the two contact surfaces.

[0010] Preferably, in S2, calculate the average distance from all points in the bearing contact surface point cloud to the fitting plane of the precast small box girder contact surface, specifically:

[0011]

[0012] In the formula, D avg is the average distance; n is the total number of points in the bearing contact surface point cloud; x i , y i , z i are the coordinates of point i in the bearing contact surface point cloud in three-dimensional space; a, b, c, d are the parameters of the fitting plane, and their values are determined by the plane equation of the precast small box girder contact surface.

[0013] Preferably, S3 includes, S31, extracting the prestressed hole point cloud by using a method based on point cloud density clustering; S32, performing 2D circle fitting on the prestressed hole point cloud by using the RANSAC algorithm, extracting the circle index, and obtaining the coordinate information of the center of the circle; S33, taking the centers of the prestressed holes on the extended surfaces of the two groups of prefabricated small box girders extending forward and backward and close to the four corners of the facade as feature points for feature matching, and calculating the transformation matrix K, and finally performing K transformation on the entire point cloud of one of the prefabricated small box girders to complete the extended virtual installation between the two groups of prefabricated small box girders.

[0014] Preferably, S31 includes:

[0015] S311. Calculate the initial point cloud density D of point i in the prefabricated small box girder point cloud i ,

[0016]

[0017] Where D i is the initial point cloud density of point i; N is the total number of points in the point cloud; j is an index variable that represents the number of other points different from point i; x i 、y i 、z i is the coordinate of point i in three-dimensional space; x j 、y j 、z j is the coordinate of point j in three-dimensional space; r ax 、r ay and r ax is the clustering parameter of the target shape;

[0018] S312. Calculate the final point cloud density D of point i in the prefabricated small box girder point cloud i ′,

[0019]

[0020] Where D i ′ is the final point cloud density of point i; D i is the initial point cloud density of point i; D cl is the density of the initial cluster center of the point cloud, which is derived from the initial distribution of the point cloud and is a constant; x i 、y i 、z i is the coordinate of point i in three-dimensional space; x cl 、y cl 、z cl is the coordinate of point cl in three-dimensional space; r bx 、r by 、r bz To update D i Radius parameter of density;

[0021] S313. After filtering the point cloud of the precast small box girder according to the final point cloud density, the point cloud is divided into several clusters by Euclidean clustering, and the prestressed hole point cloud of the precast small box girder is extracted; where

[0022]

[0023] In the formula, μ m is the center of cluster C m ; J is the loss function, representing the total error measure of clustering; M is the number of clusters, indicating that the point cloud is divided into M clusters; C m is the m-th cluster; c i is the i-th point in cluster C m .

[0024] Preferably, in S4, the multiple sequential changes include rotating around the center line of the side elevation of the precast small box girder, moving along the center line of the top surface of the precast small box girder, and moving perpendicular to the center line of the side and top surfaces of the precast small box girder.

[0025] Preferably, in S4, calculate the contact area between the precast small box girder after sequential change and the bearing. Specifically, obtain the contact surface coordinates of the precast small box girder after sequential change; convert the point cloud of the contact surface of the precast small box girder and the point cloud of the contact surface of the bearing into Delaunay triangulation; perform overlay calculation on the contact surface triangulation of the precast small box girder and the contact surface triangulation of the bearing to obtain the contact area between the precast small box girder and the bearing after sequential change; where

[0026] (x, y, z) = {sin a(X + Xr), cos a(Y + Yd), Z}

[0027] In the formula, (x, y, z) is the coordinate of any point on the precast small box girder after sequential change, (x, y, z) is the coordinate of this point in the initial installation position, α is the rotation angle around the center line of the side elevation of the precast small box girder, Xr is the offset along the center line of the top surface of the precast small box girder, and Yd is the offset along the direction perpendicular to the center line of the side and top surfaces of the precast small box girder.

[0028] The present invention also provides a virtual combined installation device for a precast small box girder bridge site, including: a processor and a memory; wherein, the memory is used to store a computer program; the processor is used to load and execute the computer program to implement the above installation method.

[0029] The present invention has at least the following beneficial effects:

[0030] The virtual combined installation method of the prefabricated small box girder bridge position of the present invention utilizes the significant feature of the prestressed hole and the plane fitting of the contact surface between the prefabricated small box girder and the support, which effectively solves the problems of high dependence on the BIM model, high subjectivity in the manual selection of point cloud splicing control points, and difficulty in controlling the accuracy. At the same time, it ensures that the prefabricated small box girder components can achieve accurate extension between prefabricated small box girders and close installation between prefabricated small box girder and the support even when the scanning point cloud quality is lost or blocked. Experimental results show that the average error after virtual installation is only 0.61mm, the maximum offset error is 1.09mm, the average angle is only 0.086°, and the maximum offset angle is 0.114°. The method has reasonable precision control and strong applicability. It can provide an installation basis for the actual implementation of the project, greatly improve the overall efficiency of the project, reduce the trial and error cost and time consumption in the actual construction process, and ensure the accuracy and safety of the construction.

[0031] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a point cloud of a small box girder and a mold point cloud according to an embodiment of the present invention;

[0033] Figure 2 yes Figure 1 The effect of the small box girder point cloud and the mold point cloud after registration processing;

[0034] Figure 3 A set of point clouds with circular holes and hole extraction results according to an embodiment of the present invention;

[0035] Figure 4 This is a diagram showing various sequential changes in the horizontal position of a prefabricated small box girder in one embodiment of the present invention;

[0036] Figure 5 This is a diagram showing the virtual assembly and installation results of a prefabricated small box girder according to an embodiment of the present invention;

[0037] Figure 6 This is a point cloud of a small box girder after virtual installation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the embodiments and drawings so that those skilled in the art can implement the invention with reference to the description.

[0039] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0040] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained from commercial channels; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention.

[0041] The present invention provides a method for virtual combined installation of precast small box girder bridges in the bridge position, including:

[0042] S1. Registration of precast small box girder and precast small box girder mold: Register the precast small box girder to be installed with the precast small box girder mold to obtain a precast small box girder that meets the accuracy requirements.

[0043] Specifically, perform point cloud preprocessing work such as denoising and downsampling on the point cloud of the precast small box girder (small box girder point cloud) and the point cloud of the precast small box girder mold (mold point cloud) obtained by three-dimensional lidar scanning. According to the geometric characteristics of the small box girder and the mold, use the algorithm based on sampling consistency initial registration (SAC-IA algorithm) to perform automatic registration without manual operation and calculate the error. For the small box girder point cloud and the mold point cloud, first search for the corresponding nearest neighbor point pairs of each point in the mold point cloud using the small box girder point cloud, and then calculate the rigid body transformation matrix using the found point pairs. Apply this transformation matrix to the small box girder point cloud and calculate the mean square error of the distance between the transformed small box girder point cloud and the mold point cloud. The process of searching for the nearest neighbor point to the final error evaluation in the algorithm is iterated repeatedly until the error between two times is less than the threshold, and the iteration process ends.

[0044] Taking Figure 1 the small box girder point cloud and the mold point cloud in Figure 2 as an example, the effect after being processed by the registration algorithm of the present invention is as

[0045] S2. Determine the initial installation positions of the precast small box girder and the bearing: First, perform grid processing on the contact surface of the precast small box girder. Second, extract the plane equations and normal vectors of the two contact surfaces when the precast small box girder contacts the bearing. Then, when the normal vectors of the two contact surfaces are the same, align any grid intersection point after grid processing with the center of the bearing, and calculate the average distance from all points in the point cloud of the bearing contact surface to the fitting plane of the contact surface of the precast small box girder. Finally, traverse all grid intersection points, and use the grid intersection point with the minimum average distance as the initial installation position of the precast small box girder and the bearing.

[0046] Specifically, performing grid processing on the contact surface of the precast small box girder includes: Denote the center of the bearing contact surface as a(x, y, z), the radius as r, and the distance from the center a to the maximum deviation boundary under the allowable deviation of the installation range as R, where R > r. Use the circular surface corresponding to the center a and the radius R as the contact surface of the precast small box girder. Select any three points on the contact surface of the precast small box girder as a plane, and perform two-dimensional grid processing on the contact surface of the precast small box girder. The grid density can be adjusted according to the accuracy required for different projects. For example, in the present invention, 0.01 m is used as the grid division density.

[0047] Extracting the plane equations and normal vectors of the two contact surfaces when the precast small box girder contacts the bearing includes: Respectively take any two points on the bearing contact surface and the contact surface of the precast small box girder (take any two grid intersection points on the contact surface of the precast small box girder, such as Figure 4 point b and point k in

[0048]

[0049] In the formula, k is the number of iterations, p represents the probability that the result of the RANSAC algorithm is useful, w is the probability of the data in the inliers set. Then, for the n groups of data required for one model fitting, the probability that all of them are in the inliers set is w n and the probability that they are not in the inliers set is 1 - w n .

[0050] The average distance from all points in the point cloud of the bearing contact surface to the fitting plane of the contact surface of the precast small box girder is specifically

[0051]

[0052] In the formula, D avg is the average distance; n is the total number of points in the point cloud of the bearing contact surface; x i , y i , z iis the coordinate of point i in the 3D space on the bearing contact surface; a, b, c, and d are the parameters of the fitted plane, and their values are determined by the plane equation of the precast small box girder contact surface.

[0053] S3. Virtual longitudinal installation of box girders: Extract the prestressed hole features of the precast small box girders, use the center of the prestressed hole as the feature point for feature matching, and perform virtual longitudinal installation on two groups of precast small box girders that are longitudinally extended.

[0054] Specifically, S31. Extract the prestressed hole point cloud using the method based on point cloud density clustering, including:

[0055] S311. Calculate the initial point cloud density D of point i in the precast small box girder point cloud i ,

[0056]

[0057] where D i is the initial point cloud density of point i; N is the total number of points in the point cloud; j is an index variable representing the number of other points different from point i; x i , y i , z i are the coordinates of point i in the 3D space; x j , y j , z j are the coordinates of point j in the 3D space; r ax , r ay and r az are the clustering parameters of the target shape;

[0058] S312. Calculate the final point cloud density D i ′ of point i in the precast small box girder point cloud

[0059]

[0060] where D i ′ is the final point cloud density of point i; D i is the initial point cloud density of point i; D cl is the density of the initial clustering center of the point cloud, obtained from the initial distribution of the point cloud and is a constant; x i , y i , z i are the coordinates of point i in the 3D space; x cl , t cl , z cl are the coordinates of point cl in the 3D space; r bx , r by , r bz are the radius parameters for updating D i density;

[0061] S313, after filtering the point cloud of the prefabricated small box girder according to the final point cloud density, the point cloud is divided into several clusters using Euclidean clustering, and the prestressed hole point cloud of the prefabricated small box girder is extracted; wherein,

[0062]

[0063] Where μ m It is cluster C m The center of the point cloud; J is the loss function, which represents the total error metric of the clustering; M is the number of clusters, which means that the point cloud is divided into M clusters; C m is the mth cluster; c i Cluster C m The i-th point in .

[0064] Take a group of point clouds with circular holes as an example, and use the above method to extract the holes on its surface. The results are shown in Figure 3 ,in, Figure 3 (a) is the original point cloud data, Figure 3 (b) is the hole extraction result.

[0065] S32. Use the RANSAC algorithm to perform 2D circle fitting on the prestressed hole point cloud, extract the circle index, and obtain the circle center coordinates, radius, and normal vector information.

[0066] S33. The centers of the prestressed holes on the extended surfaces of the two groups of prefabricated small box girders near the four corners of the facade are used as feature points for feature matching, and their transformation matrix K is calculated. Finally, the K transformation is performed on the entire point cloud of one of the prefabricated small box girders to complete the extended virtual installation between the two groups of prefabricated small box girders.

[0067] S4. Determine the final installation position of the prefabricated small box girder and the support: First, keep the installation position of the prefabricated small box girder and the support in front unchanged during the virtual installation, and make multiple extension changes to the horizontal position of the prefabricated small box girder in the back; secondly, calculate the contact area between the prefabricated small box girder and the support after the extension change; finally, traverse all the extension change positions, and take the horizontal position of the prefabricated small box girder when the contact area is the largest as the final installation position of the prefabricated small box girder and the support.

[0068] Specifically, the various subsequent changes in the horizontal position of the prefabricated small box beam are as follows: Figure 4 Shown, including Figure 4 (a): Rotate along the center line of the side elevation of the prefabricated small box beam. Figure 4 (b): Move along the center line of the top surface of the precast small box beam and Figure 4 (c): Move perpendicular to the center line of the top surface of the prefabricated small box girder.

[0069] Calculate the contact area between the precast small box girder and the bearing after the sequential change. Specifically, obtain the coordinates of the contact surface of the precast small box girder after the sequential change; convert the point cloud of the contact surface of the precast small box girder and the point cloud of the contact surface of the bearing into Delaunay triangulation; perform overlay calculation on the triangulation of the contact surface of the precast small box girder and the triangulation of the contact surface of the bearing to obtain the contact area between the precast small box girder and the bearing after the sequential change; where

[0070] (x, y, z) = {sin a(X + Xr), cos a(Y + Yd), Z}

[0071] In the formula, (X, Y, Z) is the coordinate of any point on the precast small box girder after the sequential change, (X, Y, Z) is the coordinate of this point at the initial installation position, α is the rotation angle with the center line of the side elevation of the precast small box girder as the axis, Xr is the offset along the center line of the top surface of the precast small box girder, and Yd is the offset along the direction perpendicular to the center line of the side and top surfaces of the precast small box girder.

[0072] S5. Virtual transverse sequential installation of box girders: Extract the plane equations and normal vectors of the longitudinal sequential surfaces and top surfaces of the two groups of precast small box girders that are sequentially extended to the left and right respectively, so that the normal vectors of the planes where the longitudinal sequential surfaces of the two groups of precast small box girders that are sequentially extended to the left and right are located satisfy linear correlation, and the normal vectors of the planes where the top surfaces are located satisfy a parallel relationship, and perform virtual transverse sequential installation on the two groups of precast small box girders that are sequentially extended to the left and right.

[0073] Specifically, for the two groups of precast small box girders that are sequentially extended to the left and right, A, B, C, and D are the prestressed hole feature points on the longitudinal sequential surface of one of the precast small box girders, and E, F, G, and H are the prestressed hole feature points on the same-side longitudinal sequential surface of the other precast small box girder. Determine plane a through the coordinates of any three points among A, B, C, and D, and the plane equation is a1x + b1y + c1z + d1 = 0; determine plane b through the coordinates of any three points among E, F, G, and H, and the plane equation is a2x + b2y + c2z + d2 = 0; where (a1, b1, c1) and (a2, b2, c2) are the normal vectors of the two planes. The normal vectors of the two planes are respectively denoted as In order to make these two planes in the same plane, the two planes must be parallel, and the normal vectors must be linearly correlated, that is, the ratio of the two normal vectors should be the same, as shown in the following formula:

[0074]

[0075] Determine one of the top surface planes c of the precast small box girder through the coordinates of any three points in the point cloud of the top surface of the two groups of precast small box girders that are sequentially extended to the left and right, and the plane equation is a3x + b3y + c3z + d3 = 0; and the top surface plane d of the other precast small box girder, and the plane equation is a4x + b4y + c4z + d4 = 0; and obtain the normal vector through the plane equation Make the two vectors satisfy the following formula:

[0076]

[0077] After controlling two groups of planes to be parallel through two vector calculations, two groups of precast small box girders that are horizontally extended can be made parallel in geometric space. On this basis, by making the two outer side lines of the box girder on the same straight line, the initial positions of the two groups of precast small box girders that are horizontally extended can be obtained. The gap between two adjacent groups of precast small box girders that are horizontally extended is determined by the initial installation positions of the two groups of precast small box girders and their respective bearings, and no other adjustments are required.

[0078] Furthermore, in order to better understand the installation process of the present invention, taking three-span precast small box girders (A, B, C) and two sections of bearings (A, B, C) as an example, the specific steps of high-speed bridge installation are introduced.

[0079] First, perform a close contact calculation on box girder A and bearings A and B through the close contact calculation method in S2 to obtain their initial installation positions (as shown in Figure 5 (a)). Secondly, use the longitudinal extension calculation method in S3 to calculate box girder A and box girder B that is longitudinally extended with it to obtain the longitudinal extension position of box girder B. Then, perform a calculation on box girder B and bearings B and C through the calculation method in S2 to obtain the installation positions of box girders A and B and bearings A, B, and C (as shown in Figure 5 (b)). After that, take box girders A and B and bearings A, B, and C as an independent system and calculate using the optimal fit traversal algorithm proposed in S5 to obtain the final installation positions of each component in the system. Then, perform a calculation on box girders A and C and bearings A and B through the transverse extension calculation method proposed in S4 to obtain the installation positions of box girders A, B, and C and the bearings (as shown in Figure 5 (c)). Finally, take box girder C as the starting section of a new column and repeat the above installation process, and so on, until the installation of all box girders and bearings of the high-speed bridge is finally completed.

[0080] The present invention also provides a virtual installation system, which is constructed based on the Three.js virtual environment relying on the virtual combined installation method of precast small box girder bridge positions of the present invention. Three.js is a JavaScript library based on WebGL for creating and rendering 3D graphics on web pages. It simplifies the direct interaction with WebGL, enabling developers to more easily create complex three-dimensional scenes, animations, interactions, and visualizations in browsers. The basic framework of the virtual installation environment is constructed using six major elements: scene, perspective camera, renderer, vertex and UV coordinates, index buffer array (IBO), and mesh model. By combining buffer geometry and camera orbit controller to change vertex coordinates in a way that manipulates the mouse, the virtual installation environment has the property of human-computer interaction. To achieve better visualization effects, the functions such as point cloud color, point size, and number of points in the system display are modified and updated in real time using the APIs provided by Three.js and the WebGL library. Then, two consecutive precast small box girders that have passed the S1 registration detection (the mean square error between the point cloud of the precast small box girder and the mold point cloud after registration is less than 0.05) are imported into the virtual installation system for virtual installation. Through the built-in algorithms in the system (i.e., S2, S3, S4), the system will automatically generate the point cloud of the small box girder after virtual installation is completed, as Figure 5 shown. By observing the connection of the small box girders, it can be concluded that from the visual effect, the virtual combined installation method of precast small box girder bridge positions of the present invention can better complete the virtual installation task of precast small box girders.

[0081] Furthermore, in order to verify the accuracy, effectiveness, and reliability of the proposed virtual combined installation method of precast small box girder bridge positions of the present invention, the present invention will select 5 precast small box girders in 4 groups for virtual installation experiments, and conduct accuracy tests from the overall error and local error. The overall error refers to comparing and analyzing the point cloud of the small box girder after virtual installation with the design parameters of the small box girder. Taking the four corner points on the consecutive connection surface of the small box girder as feature points, calculate the errors between the coordinates of the four feature points and the design coordinates. The error in the x-axis direction is denoted as Dx, the error in the y-axis direction is denoted as Dy, and the error in the z-axis direction is denoted as Dz; the local error refers to the included angle formed by the connection surfaces of two consecutive small box girders. Denote the included angle between the normal vectors of the two consecutive connection surfaces as α, and this value is the included angle value of the continuation. The results are shown in Table 1.

[0082] Table 1 Virtual Installation Error Detection Table

[0083]

[0084] According to the error detection table, in the precision detection test, the maximum offset error is 1.09 mm and the average error is 0.61 mm; the maximum offset angle is 0.114° and the average angle is 0.086°. The errors obtained in this experiment all meet the precision requirements specified in the "Quality Inspection and Evaluation Standards for Highway Engineering, Volume 1, Civil Engineering" (JTC F80 / 1 - 2017) and the "Technical Specification for Prefabrication and Installation of Small Box Girder".

[0085] In summary, the virtual combined installation method for precast small box girder bridges proposed in the present invention can quickly and effectively perform full - automatic virtual installation of precast small box girders with good precision. It can also complete the virtual installation of components under the condition of certain missing and occlusion of the scanned point cloud, indicating that the present invention has certain value for guiding construction and good versatility. In addition, it also has certain reference significance for similar problems.

[0086] The present invention also provides a virtual combined installation device for precast small box girder bridges, which is a device including a processor (CPU / MCU / SOC) and a memory (ROM / RAM), such as: desktop computers, laptops, smartphones, etc. Specifically, the memory stores a computer program, and when the processor loads and executes the computer program, it can implement all or part of the steps of the above - mentioned virtual combined installation method for precast small box girder bridges.

[0087] The number of devices and the scale of processing described here are used to simplify the description of the present invention. The application, modification, and variation of the virtual combined installation method for precast small box girder bridges of the present invention are obvious to those skilled in the art.

[0088] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the illustrated examples described here.

Claims

1. A virtual combined installation method for precast small box girder bridges, characterized in that, Including: S1. Register the precast small box girder to be installed with the precast small box girder mold to obtain a precast small box girder meeting the accuracy requirements; S2. Perform meshing on the contact surface of the precast small box girder, extract the plane equations and normal vectors of the two contact surfaces when the precast small box girder contacts the support. When the normal vectors of the two contact surfaces are the same, align any grid intersection point after meshing with the center of the support, calculate the average distance from all points in the point cloud of the support contact surface to the fitting plane of the precast small box girder contact surface, traverse all grid intersection points, and use the grid intersection point with the minimum average distance as the initial installation position of the precast small box girder and the support; S3. Extract the prestressed hole features on the longitudinal extension surfaces of two groups of successively extended precast small box girders, use the center of the prestressed hole as the feature point for feature matching, and perform longitudinal extension virtual installation on two groups of successively extended precast small box girder pairs; S4. Keep the installation position of the precast small box girder in front during the extension virtual installation unchanged, perform various extension changes on the horizontal plane position of the precast small box girder behind, calculate the contact area between the precast small box girder and the support after the extension change, traverse all extension change positions, and use the horizontal plane position of the precast small box girder with the largest contact area as the final installation position of the precast small box girder and the support.

2. The virtual combined installation method for precast small box girder bridge positions according to claim 1, characterized in that, It also includes S5. Respectively extract the plane equations and normal vectors of the longitudinal extension surfaces and top surfaces of two groups of precast small box girders extending left and right, make the normal vectors of the planes where the longitudinal extension surfaces of the two groups of precast small box girders extending left and right satisfy linear correlation, and the normal vectors of the planes where the top surfaces are located satisfy the parallel relationship, and perform transverse extension virtual installation on two groups of precast small box girder pairs extending left and right.

3. The virtual combined installation method of precast small box girder bridge positions as claimed in claim 1, wherein, In S2, when performing meshing on the contact surface of the precast small box girder, it includes: Denote the center of the support contact surface as a(x, y, z), the radius as r, and the distance from the center a to the maximum deviation boundary under the allowable deviation of the installation range as R, R>r. Use the circular surface corresponding to the center a and the radius R as the contact surface of the precast small box girder, select any three points on the contact surface of the precast small box girder as a plane, and perform two-dimensional meshing on the contact surface of the precast small box girder.

4. The virtual combined installation method of precast small box girder bridge positions according to claim 3, characterized in that, In S2, when extracting the plane equations and normal vectors of the two contact surfaces when the precast small box girder contacts the support, it includes: Respectively take any two points on the support contact surface and the precast small box girder contact surface, use the RANSAC algorithm to fit a straight line with the extracted any two points and continuously iterate to obtain the plane equations and normal vectors of the two contact surfaces.

5. The virtual combined installation method of precast small box girder bridge position according to claim 4, characterized in that, In S2, when calculating the average distance from all points in the point cloud of the support contact surface to the fitting plane of the precast small box girder contact surface, specifically: where D avg is the average distance; n is the total number of points in the point cloud of the bearing contact surface; x i , y i , z i are the coordinates of point i in the point cloud of the bearing contact surface in three-dimensional space; a, b, c, d are the parameters of the fitting plane, and their values are determined by the plane equation of the contact surface of the precast small box girder.

6. The virtual combined installation method for precast small box girder bridge positions according to claim 1, characterized in that, In S3, it includes: S31. Use the method of clustering based on point cloud density to extract the prestressed hole point cloud; S32. Use the RANSAC algorithm to perform 2D circle fitting on the prestressed hole point cloud, extract the index of the circle, and obtain the center coordinate information; S33. Use the centers of the prestressed holes near the four corners of the elevation on the extension surfaces of two groups of successively extended precast small box girders as feature points for feature matching, calculate their transformation matrix K, and finally perform K transformation on all the point clouds of one of the precast small box girders to complete the extension virtual installation between the two groups of precast small box girders.

7. The virtual combined installation method for precast small box girder bridges as described in claim 6, characterized in that, In S31, it includes: S311. Calculate the initial point cloud density D of point i in the point cloud of precast small box girders i , Where D i is the initial point cloud density of point i; N is the total number of points in the point cloud; j is an index variable representing the number of other points different from point i; x i , y i , z i are the coordinates of point i in three-dimensional space; x j , y j , z j are the coordinates of point j in three-dimensional space; r ax , r ay and r az are the clustering parameters of the target shape; S312. Calculate the final point cloud density D of point i in the point cloud of the precast small box girder i ′, Where D i ′ is the final point cloud density of point i; D i is the initial point cloud density of point i; D cl is the density of the initial clustering center of the point cloud, obtained from the initial distribution of the point cloud and is a constant; x i , y i , z i are the coordinates of point i in three-dimensional space; x cl , y cl , z cl are the coordinates of point cl in three-dimensional space; r bx , r by , r bz are the radius parameters used to update the D i density; S313, after filtering the point cloud of the prefabricated small box girder according to the final point cloud density, the point cloud is divided into several clusters using Euclidean clustering, and the prestressed hole point cloud of the prefabricated small box girder is extracted; wherein, where μ m is the center of cluster C m ; J is the loss function, representing the total error measure of clustering; M is the number of clusters, indicating that the point cloud is divided into M clusters; C m is the m-th cluster; c i is the i-th point in cluster C m .

8. The virtual combined installation method for precast small box girder bridges as described in claim 1, characterized in that In S4, the various sequential changes include rotation along the center line of the side elevation of the precast small box girder, movement along the center line of the top surface of the precast small box girder, and movement perpendicular to the center line of the side top surface of the precast small box girder.

9. The virtual combined installation method of precast small box girder bridge positions according to claim 8, wherein, In S4, the contact area between the precast small box girder and the support after the change is calculated, specifically, the coordinates of the contact surface of the precast small box girder after the change are obtained; the point cloud of the contact surface of the precast small box girder and the point cloud of the contact surface of the support are converted into a Delaunay triangulation; the triangulation of the contact surface of the precast small box girder and the triangulation of the contact surface of the support are superimposed to obtain the contact area between the precast small box girder and the support after the change; wherein, (x,y,z)={sinα(X+Xr),cosa(Y+Yd),Z} In the formula, (x, y, z) is the coordinate of any point of the prefabricated small box girder after the subsequent change, (X, Y, Z) is the coordinate of the point at the initial installation position, α is the angle of rotation along the center line of the side elevation of the prefabricated small box girder, Xr is the offset of the movement along the center line of the top surface of the prefabricated small box girder, and Yd is the offset of the movement perpendicular to the center line of the top surface of the prefabricated small box girder.

10. Prefabricated small box girder bridge position virtual combined installation equipment, characterized in that include: A processor and a memory; wherein the memory is used to store a computer program; and the processor is used to load and execute the computer program to implement the installation method according to any one of claims 1 to 9.

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