Method and device for virtual assembly installation of prefabricated small box girder bridge

Abstract

The application discloses a prefabricated small box girder bridge position virtual combination installation method, which comprises the following steps: aligning a prefabricated small box girder to be installed with a mold; gridizing a contact surface of the prefabricated small box girder, extracting plane equations and normal vectors of two contact surfaces when the prefabricated small box girder contacts with a support, and determining an initial installation position; extracting prestress hole features of the prefabricated small box girder, taking a hole center as a feature point, longitudinally and sequentially virtually installing two groups of prefabricated small box girder pairs; extracting plane equations and normal vectors of a longitudinal and sequential surface and a top surface of the prefabricated small box girder, and transversely and sequentially virtually installing two groups of prefabricated small box girder pairs; keeping the installation position of a previous prefabricated small box girder and the support unchanged, changing a horizontal position of a subsequent prefabricated small box girder in multiple sequential manners, calculating a contact area, and determining a final installation position; and a prefabricated small box girder bridge position virtual combination installation device. The application has the advantages of being capable of realizing full-automatic virtual installation of the prefabricated small box girder and high precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of virtual installation of box girder. More particularly, the present application relates to a method and device for virtual combined installation of prefabricated small box girder bridge. BACKGROUND

[0002] The point cloud data of the small box girder obtained by using the three-dimensional laser scanning technology for virtual installation can not only effectively improve the installation precision of the construction site, but also comprehensively improve the construction quality of the whole project. However, in the prior art, Revit, SCENE and other software are usually used to perform reverse modeling on the point cloud data of various complex small box girder components, and the building information model (BIM) is used to realize pre-assembly, or point cloud modeling based on target splicing is used to complete virtual assembly. Such prior art solutions generally involve reverse engineering, and need to use various professional software to model and format convert the point cloud, and are highly dependent on the BIM model. In the process of manual selection of control points for point cloud splicing, the subjectivity is large, so that the precision is difficult to effectively control, and when the quality of the scanning point cloud is missing, the small box girder component is difficult to realize accurate installation. SUMMARY

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

[0004] In order to achieve the object and other advantages of the present application, a method for virtual combined installation of prefabricated small box girder bridge is provided, comprising: S1, registering the prefabricated small box girder to be installed with the prefabricated small box girder mold to obtain a prefabricated small box girder meeting the accuracy requirements; S2, performing grid processing on the contact surface of the prefabricated small box girder, extracting the plane equation and normal vector of the two contact surfaces when the prefabricated small box girder contacts the support, aligning the grid intersection point after the grid processing with the center of the support when the normal vectors of the two contact surfaces are the same, calculating the average distance from all points in the support contact surface point cloud to the fitting plane of the prefabricated small box girder contact surface, and traversing all grid intersection points to take the grid intersection point with the smallest average distance as the initial installation position of the prefabricated small box girder and the support;

[0005] S3, extracting the prestressed hole features on the longitudinal extension surface of the two groups of prefabricated small box girders in front and back extension, taking the center of the prestressed hole as a feature point for feature matching, and performing longitudinal extension virtual installation on the two groups of prefabricated small box girders; S4, keeping the installation position of the prefabricated small box girder in front unchanged during the extension virtual installation, performing various extension changes on the horizontal position of the prefabricated small box girder behind, calculating the contact area of the prefabricated small box girder and the support after the extension change, and traversing all extension change positions to take the horizontal position of the prefabricated small box girder with the maximum contact area as the final installation position of the prefabricated small box girder and the support.

[0006] Preferably, the virtual combined installation method of the prefabricated small box girder bridge site further comprises: S5, extracting plane equations and normal vectors of longitudinal extension surfaces and top surfaces of the two groups of prefabricated small box girders extending leftward and rightward respectively, so that the normal vectors of the planes where the longitudinal extension surfaces of the two groups of prefabricated small box girders extending leftward and rightward are located satisfy linear correlation, and the normal vectors of the planes where the top surfaces are located satisfy parallel relationship, and performing virtual installation of the two groups of prefabricated small box girders extending leftward and rightward in the transverse direction.

[0007] Preferably, in S1, after the point cloud of the prefabricated small box girder to be installed and the point cloud of the prefabricated small box girder mold are denoised and down-sampled, an initial registration algorithm based on sampling consistency is used for registration.

[0008] Preferably, in S2, the prefabricated small box girder contact surface is subjected to meshing processing, which comprises: taking the center of the support contact surface as a (x, y, z) and the radius as r, the distance from the center a to the maximum deviation boundary within the allowable deviation of the installation range as R, R>r, taking the circular surface corresponding to the center a and the radius R as the prefabricated small box girder contact surface, and taking any three points on the prefabricated small box girder contact surface as a plane, and performing two-dimensional meshing on the prefabricated small box girder contact surface.

[0009] Preferably, in S2, the plane equation and the normal vector of the two contact surfaces when the prefabricated small box girder contacts the support are extracted, which comprises: taking any two points on the support contact surface and the prefabricated small box girder contact surface respectively, and using the RANSAC algorithm to fit a straight line and continuously iterate to obtain the plane equation and the normal vector of the two contact surfaces.

[0010] Preferably, in S2, the average distance of all points in the point cloud of the support contact surface to the fitting plane of the prefabricated small box girder contact surface is calculated, which comprises:

[0011]

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

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

[0014] Preferably, S31 comprises:

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

[0016]

[0017] In the formula, 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 three-dimensional space; x j , y j , z j are the coordinates of point j in the three-dimensional space; r ax , r ay , and r ax are the clustering parameters of the target shape.

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

[0019]

[0020] In the formula, 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, which is 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 three-dimensional space; x cl , y cl , z cl are the coordinates of point cl in the three-dimensional space; r bx , r by , r bz are the radius parameters for updating the D i density.

[0021] S313、According to the final point cloud density, the prefabricated small box girder point cloud is filtered, and the point cloud is divided into a plurality of clusters by using Euclidean clustering to extract the prestressed hole point cloud of the prefabricated small box girder; wherein,

[0022]

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

[0024] Preferably, in S4, the plurality of extension changes include rotation along the center line of the side elevation of the prefabricated small box girder, movement along the center line of the top surface of the prefabricated small box girder, and movement along the center line perpendicular to the side top surface of the prefabricated small box girder.

[0025] Preferably, in S4, the contact area of the prefabricated small box girder after the extension change and the support is calculated, specifically, the contact surface coordinates of the prefabricated small box girder after the extension change are obtained; the point cloud of the contact surface of the prefabricated small box girder and the point cloud of the contact surface of the support are converted into a Delaunay triangular network; the contact surface triangular network of the prefabricated small box girder and the contact surface triangular network of the support are superimposed to obtain the contact area of the prefabricated small box girder after the extension change and the support; wherein,

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

[0027] In the formula, (x, y, z) is the coordinates of any point of the prefabricated small box girder after the extension change, (x, y, z) is the coordinates of the point in the initial installation position, a is the angle of rotation along the center line of the side elevation of the prefabricated small box girder, Xr is the offset of movement along the center line of the top surface of the prefabricated small box girder, and Yd is the offset of movement along the center line perpendicular to the side top surface of the prefabricated small box girder.

[0028] The application also provides a prefabricated small box girder bridge position virtual combined installation equipment, comprising: 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 realize the installation method.

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

[0030] The prefabricated small box girder bridge site virtual combined installation method of the application solves the problems of high dependence on BIM model, large subjectivity of manual point selection of point cloud splicing control points and difficult control of precision, and ensures that the prefabricated small box girder components can also realize accurate sequential extension between the prefabricated small box girders and the prefabricated small box girder and the tight installation between the prefabricated small box girder and the support in the case that the scanning point cloud quality is missing and blocked, the 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 precision control of the method is reasonable, the applicability is strong, the installation basis can be provided for the engineering actual implementation, the overall efficiency of the project is greatly improved, the trial and error cost and time consumption in the actual construction process are reduced, and the accuracy and safety of the construction are ensured.

[0031] Other advantages, objects, and features of the application will be apparent from the following specification, and will be appreciated by those skilled in the art. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The small box girder point cloud and the mold point cloud of an embodiment of the application are shown in Figure 1.

[0033] Figure 2 The small box girder point cloud and the mold point cloud in Figure 1 are shown after registration processing in Figure 2. Figure 1

[0034] Figure 3 A group of point clouds with circular holes and hole extraction results of an embodiment of the application are shown in Figure 3.

[0035] Figure 4 The various sequential extension changes of the prefabricated small box girder in the horizontal plane position of an embodiment of the application are shown in Figure 4.

[0036] Figure 5 The prefabricated small box girder virtual combined installation result diagram of an embodiment of the application is shown in Figure 5.

[0037] Figure 6 The small box girder point cloud after virtual installation of an embodiment of the application is shown in Figure 6. DETAILED DESCRIPTION

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

[0039] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof. ​

[0040] It should be noted that the experimental methods described in the following embodiments are conventional methods, and the reagents and materials are commercially available unless otherwise specified. In the description of the present application, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0041] The present application provides a prefabricated small box girder bridge site virtual combination installation method, comprising:

[0042] S1, the prefabricated small box girder is matched with the prefabricated small box girder mold: the prefabricated small box girder to be installed is matched with the prefabricated small box girder mold, and the prefabricated small box girder meeting the accuracy requirement is obtained.

[0043] Specifically, the prefabricated small box girder point cloud (small box girder point cloud) and the prefabricated small box girder mold point cloud (mold point cloud) obtained by three-dimensional laser radar scanning are denoised, down-sampled and other point cloud preprocessing work. According to the geometric characteristics of the small box girder and the mold, the initial registration based on sampling consistency (SAC-IA algorithm) algorithm is used for automatic registration without human operation, and the error is calculated. For the small box girder point cloud and the mold point cloud, first, the small box girder point cloud is used to search for the corresponding nearest point pair of each point in the mold point cloud, and then the rigid transformation matrix is calculated by using the found point pair, and the transformation matrix is applied to the small box girder point cloud. The mean square error between the transformed small box girder point cloud and the mold point cloud is calculated. The process of searching for the nearest point to the final error evaluation is repeated iteratively until the error of two times is less than the threshold value, and the iteration process is ended.

[0044] Taking the small box girder point cloud and the mold point cloud in Figure 1 as an example, the effect after processing by the registration algorithm of the present application is shown in Figure 2 It can be seen that the small box girder point cloud and the mold point cloud achieve good registration effect in the bottom surface and the side wall, and the registration accuracy is high, and the mean square error is only 0.037676 m, which meets the industrial production error requirement.

[0045] S2, determining the initial installation position of the prefabricated small box girder and the support: firstly, the prefabricated small box girder contact surface is subjected to grid processing, secondly, the plane equation and normal vector of the two contact surfaces when the prefabricated small box girder contacts the support are extracted, then the grid intersection points after the grid processing are aligned with the center of the support circle when the normal vectors of the two contact surfaces are the same, the average distance of all points in the support contact surface point cloud to the fitting plane of the prefabricated small box girder contact surface is calculated, finally, all grid intersection points are traversed, and the grid intersection point with the smallest average distance is taken as the initial installation position of the prefabricated small box girder and the support.

[0046] Specifically, the prefabricated small box girder contact surface is subjected to grid processing, including that the center of the support contact surface is a (x, y, z), the radius is r, the distance from the center a to the maximum deviation boundary in the allowable deviation range of installation is R, R>r, the circle surface corresponding to the center a and the radius R is taken as the prefabricated small box girder contact surface, three points on the prefabricated small box girder contact surface are selected as a plane, the prefabricated small box girder contact surface is subjected to two-dimensional grid, and the grid density can be adjusted according to the accuracy required by different projects, for example, 0.01 m is taken as the density of grid division in the present application.

[0047] The plane equation and normal vector of the two contact surfaces when the prefabricated small box girder contacts the support are extracted, including that any two points on the support contact surface and the prefabricated small box girder contact surface (any two grid intersection points on the prefabricated small box girder contact surface, such as the b point and the k point in the figure) are taken respectively, a straight line is fitted by using the RANSAC algorithm with the extracted any two points and iterated k times, and the plane equation and normal vector of the two contact surfaces are obtained. Wherein, Figure 4

[0048]

[0049] In the formula, k is the iteration number, p represents the probability of the RANSAC algorithm result being useful, w is the probability of data in the inliers set, and then the probability of n groups of data required for model fitting once all being in the inliers set is w n , and the probability of not being in the inliers set is 1-w n .

[0050] The average distance of all points in the support contact surface point cloud to the fitting plane of the prefabricated small box girder contact surface is specifically,

[0051]

[0052] In the formula, D avg is the average distance, n is the total number of points in the support contact surface point cloud, x i , y i , and z i ​Let be the coordinates of point i in the three-dimensional space of the point cloud of the support contact surface; a, b, c, and d are the parameters of the fitted plane, whose values ​​are determined by the plane equation of the precast small box girder contact surface.

[0053] S3. Longitudinal extension virtual 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 longitudinal extension virtual installation on the two sets of precast small box girder pairs that are longitudinally extended.

[0054] Specifically, S31, the point cloud of prestressed holes is extracted using a point cloud density clustering method, including:

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

[0056]

[0057] In the formula, D i Let be 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 Let x be the coordinates of point i in three-dimensional space; j y j z j Let r be the coordinates of point j in three-dimensional space; ax r ay and r az Clustering parameters for the target shape;

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

[0059]

[0060] In the formula, D i ′ represents the final point cloud density of point i; D i Let D be the initial point cloud density at point i; cl The density of the initial cluster centers of the point cloud is derived from the initial distribution of the point cloud and is a constant; x i y i z i Let x be the coordinates of point i in three-dimensional space; cl t cl z cl Let cl be the coordinates of point cl in three-dimensional space; r bx r by r bz For use in updating D i The radius parameter of density;

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

[0062]

[0063] In the formula, μ m is the center of the cluster C m ; J is a loss function, representing the total error measurement of clustering; M is the number of clusters, representing the division of the point cloud into M clusters; C m is the mth cluster; c i is the ith point in the cluster C m .

[0064] Taking a set of point clouds with circular holes as an example, the holes on the surface are extracted by using the above method, and the results are shown in Figure 3 , wherein, Figure 3 (a) is the original point cloud data, Figure 3 (b) is the hole extraction result.

[0065] S32, the RANSAC algorithm is used to fit the 2D circle to the prestressed hole point cloud, the index of the circle is extracted, and the center coordinates, radius and normal vector information are obtained.

[0066] S33, the centers of the prestressed holes on the two groups of prefabricated small box girders are taken as feature points for feature matching, and the transformation matrix K is calculated, and finally the K transformation is performed on the whole point cloud of one of the prefabricated small box girders, and the virtual installation of the two groups of prefabricated small box girders is completed.

[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 of the virtual installation unchanged, and change the horizontal position of the prefabricated small box girder in many ways, second, calculate the contact area of the prefabricated small box girder and the support after the change, and finally traverse all the change positions, and take the horizontal position of the prefabricated small box girder with the largest contact area as the final installation position of the prefabricated small box girder and the support.

[0068] Specifically, the horizontal position of the prefabricated small box girder changes in many ways, as shown in Figure 4 , including Figure 4 (a): rotating along the center line of the prefabricated small box girder side facade as the axis, Figure 4 (b): moving along the center line of the prefabricated small box girder top surface and Figure 4 (c): moving along the center line perpendicular to the prefabricated small box girder side top surface.

[0069] The contact area of the precast small box girder and the support after the change in the extension is calculated, specifically, the contact surface coordinates of the precast small box girder after the change in the extension are obtained; the precast small box girder contact surface point cloud and the support contact surface point cloud are converted into a Delaunay triangular network; the precast small box girder contact surface triangular network and the support contact surface triangular network are superimposed and calculated to obtain the contact area of the precast small box girder and the support after the change in the extension; wherein,

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

[0071] In the formula, (X, Y, Z) is the coordinates of any point of the precast small box girder after the change in the extension, (X, Y, Z) is the coordinates of the point in the initial installation position, a is the angle of rotation along the center line of the side surface of the precast small box girder, Xr is the offset amount of movement along the center line of the top surface of the precast small box girder, and Yd is the offset amount of movement along the center line perpendicular to the side top surface of the precast small box girder.

[0072] S5, the box girder is transversely extended and virtually installed: the plane equations and normal vectors of the longitudinal extension surfaces and top surfaces of the two groups of precast small box girders extending left and right are extracted respectively, the normal vectors of the planes where the longitudinal extension surfaces of the two groups of precast small box girders extending left and right are located satisfy linear correlation, and the normal vectors of the planes where the top surfaces are located satisfy parallel relationship, and the two groups of precast small box girders extending left and right are transversely extended and virtually installed.

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

[0074]

[0075] One of the precast small box girder top surface planes c is determined by the coordinates of any three points in the top surface point cloud of the two groups of precast small box girders extending left and right, and the plane equation is a3x+b3y+c3z+d3=0; and the other precast small box girder top surface plane d, the plane equation is a4x+b4y+c4z+d4=0; and the normal vectors are obtained by the plane equation The two vectors satisfy the following formula:

[0076]

[0077] After the two groups of parallel planes are controlled by twice vector calculation, the two groups of prefabricated small box girders which are longitudinally aligned can be parallel in geometric space. On this basis, the two outer side lines of the box girders are on the same straight line, and the initial position of the two groups of prefabricated small box girders which are transversely aligned is obtained. The gap between the two groups of prefabricated small box girders which are transversely aligned is determined by the initial installation position of the two groups of prefabricated small box girders and the respective supports, and no other adjustment is needed.

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

[0079] Firstly, the abutment calculation method in S2 is used to calculate the abutment of the box girder A and the supports A and B, and the initial installation position thereof is obtained (as shown in (a) of Fig. 2). Figure 5 Secondly, the longitudinal alignment calculation method in S3 is used to calculate the box girder A and the box girder B which is longitudinally aligned with the box girder A, and the longitudinal alignment position of the box girder B is obtained. Then, the calculation method in S2 is used to calculate the box girders A and B and the supports A, B and C, and the installation position of the box girders A and B and the supports A, B and C is obtained (as shown in (b) of Fig. 2). Figure 5 (b) of Fig. 2). Then, the box girders A and B and the supports A, B and C are taken as an independent system, and the optimal fitting degree traversal algorithm in S5 is used to calculate the final installation position of each component in the system. Then, the transverse alignment calculation method in S4 is used to calculate the box girders A and C and the supports A and B, and the installation position of the box girders A and B and the supports is obtained (as shown in (c) of Fig. 2). Figure 5 (c) of Fig. 2). Finally, the box girder C is taken as the starting segment of a new column, and the above installation process is repeated, and the installation of the entire box girders and supports of the high-speed bridge is finally completed.

[0080] The application also provides a virtual installation system which is a virtual combined installation method of the prefabricated small box girder bridge of the application relying on a Three.js virtual environment. Three.js is a WebGL-based JavaScript library for creating and rendering 3D graphics on web pages. It simplifies direct interaction with WebGL, enabling developers to more easily create complex three-dimensional scenes, animations, interactions and visualizations in browsers, using six elements, namely scene (Scene), camera (PerspectiveCamera), renderer (Renderer), vertex and UV coordinates, index buffer list (IBO) and mesh model (Mesh) to build the basic framework of the virtual installation environment, and combining buffer geometry and camera track controller to change the vertex coordinates in the manner of mouse control, so that the virtual installation environment has human-computer interaction properties. In order to achieve better visualization effect, the API provided by Three.js and the WebGL library are used to modify the functions of point cloud color, point size and point number in the system display in real time. Then the two small box girders which are sequentially extended before and after the S1 registration detection (the mean square error of the small box girder point cloud 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 algorithm (namely S2, S3 and S4) in the system, the small box girder point cloud after virtual installation will be automatically generated, as shown in the figure. Figure 5 As shown in the figure, through the observation of the connection of the small box girder, it can be concluded that, from the visual effect, the virtual combined installation method of the prefabricated small box girder bridge of the application can better complete the virtual installation task of the prefabricated small box girder.

[0081] Further, in order to verify the accuracy, effectiveness and reliability of the virtual combined installation method of the prefabricated small box girder bridge proposed by the application, five prefabricated small box girders are selected for virtual installation experiment, and the precision is tested from the overall error and the local error. The overall error refers to the comparison and analysis of the small box girder point cloud after virtual installation and the small box girder design parameters, taking the four corner points on the sequentially extended connection surface of the small box girder as feature points, calculating the error of the coordinates of the four feature points and the design coordinates, the x-axis direction error is denoted as Dx, the y-axis direction error is denoted as Dy, and the z-axis direction error is denoted as Dy; the local error refers to the included angle of the connection surface of the two sequentially extended box girders, denoted as the included angle of the normal vectors of the two sequentially extended connection surfaces, which is the sequentially extended included angle value, and the results are shown in Table 1.

[0082] Table 1 Virtual installation error detection table

[0083]

[0084] From the error detection table, in the precision detection test, the maximum offset error is 1.09mm, the average error is 0.61mm; the maximum offset angle is 0.114°, the average angle is 0.086°, the errors obtained in the experiment meet the precision specified in the "Highway Engineering Quality Inspection and Evaluation Standard First Edition Civil Engineering" (JTC F80 / 1-2017) and "Small Box Girder Precast and Installation Process Technology Description".

[0085] In summary, the prefabricated small box girder bridge virtual combination installation method can quickly and effectively perform full-automatic virtual installation on the prefabricated small box girder and has good precision. The virtual installation on the component can also be completed under the condition that the quality of the scanning point cloud has certain defects and occlusions, which shows that the present application has certain value for guiding construction and good generality, and in addition, has certain reference significance for similar problems.

[0086] The present application also provides a prefabricated small box girder bridge virtual combination installation device, which is a device comprising a processor (CPU / MCU / SOC) and a memory (ROM / RAM), such as a desktop computer, a laptop computer, a smart phone and the like. In particular, the memory stores a computer program, and the processor can implement all or part of the steps of the prefabricated small box girder bridge virtual combination installation method when loading and executing the computer program.

[0087] The number of devices and the processing scale described herein are used to simplify the description of the present application. It is obvious to those skilled in the art that the application of the prefabricated small box girder bridge virtual combination installation method of the present application, modification and change is obvious.

[0088] Although the embodiments of the present application have been disclosed as above, it is not limited to the application listed in the specification and the embodiments, and it can be fully applied to various fields suitable for the present application, and other modifications can be easily realized by those skilled in the art, therefore, the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for virtual assembly installation of precast small box girder bridge, characterized in that, The method comprises the following steps: S1, aligning the prefabricated small box girder to be installed with the prefabricated small box girder mold to obtain a prefabricated small box girder meeting the accuracy requirements; S2, grid processing the contact surface of the prefabricated small box girder, extracting the plane equation and normal vector of the two contact surfaces when the prefabricated small box girder contacts the support, aligning the grid intersection point after the grid processing with the center of the support when the normal vectors of the two contact surfaces are the same, calculating the average distance from all points in the point cloud of the support contact surface to the fitting plane of the prefabricated small box girder contact surface, and traversing all grid intersections to take the grid intersection with the smallest average distance as the initial installation position of the prefabricated small box girder and the support; S3, extracting the prestressed hole features on the longitudinal extension surface of the two groups of prefabricated small box girders in front and back extension, taking the center of the prestressed hole as a feature point for feature matching, and virtually installing the two groups of prefabricated small box girders in longitudinal extension; S4, keeping the installation position of the prefabricated small box girder in front unchanged during the virtual installation in extension, changing the horizontal position of the prefabricated small box girder in extension, calculating the contact area of the prefabricated small box girder and the support after the extension change, and traversing all extension change positions to take the horizontal position of the prefabricated small box girder with the maximum contact area as the final installation position of the prefabricated small box girder and the support.

2. The precast small box girder bridge site virtual assembly installation method of claim 1 wherein, Further comprising S5, extracting the plane equation and normal vector of the longitudinal extension surface and the top surface of the two groups of prefabricated small box girders in left and right extension respectively, making the normal vectors of the planes where the longitudinal extension surfaces of the two groups of prefabricated small box girders in left and right extension satisfy linear correlation, and the normal vectors of the planes where the top surfaces satisfy parallel relationship, and virtually installing the two groups of prefabricated small box girders in transverse extension.

3. The method of claim 1, wherein, In S2, the grid processing of the contact surface of the prefabricated small box girder comprises the following steps: taking the center of the support contact surface as a(x, y, z) and the radius as r, the distance from the center a to the maximum deviation boundary within the allowable deviation of the installation range as R, R>r, taking the circular surface corresponding to the center a and the radius R as the contact surface of the prefabricated small box girder, and taking three optional points on the contact surface of the prefabricated small box girder as a plane to perform two-dimensional grid processing on the contact surface of the prefabricated small box girder.

4. The method of claim 3, wherein, In S2, the plane equation and normal vector of the two contact surfaces when the prefabricated small box girder contacts the support are extracted, which comprises the following steps: taking any two points on the support contact surface and the prefabricated small box girder contact surface respectively, using the RANSAC algorithm to fit a straight line by using the extracted any two points and constantly iterating to obtain the plane equation and normal vector of the two contact surfaces.

5. The precast small box girder bridge site virtual assembly installation method of claim 4 wherein, In S2, the average distance from all points in the point cloud of the support contact surface to the fitting plane of the prefabricated small box girder contact surface is calculated, which is specifically, where D avg is the average distance; n is the total number of points in the point cloud of the contact surface of the support; x i , y i , z i are the coordinates in three-dimensional space of the point i in the point cloud of the contact surface of the support. a, b, c, d are the parameters of the fitted plane, the values of which are determined by the equation of the plane of the contact surface of the prefabricated small box girder.

6. The precast small box girder bridge site virtual assembly installation method as claimed in claim 1, wherein, In S3, it comprises the following steps: S31, extracting the prestressed hole point cloud by using the point cloud density clustering based method; S32, performing 2D circle fitting on the prestressed hole point cloud by using the RANSAC algorithm to extract the index of the circle and obtain the center coordinate information; S33, taking the center of the prestressed hole near the four corners of the facade on the extension surface of the two groups of prefabricated small box girders in front and back extension as a feature point for feature matching, calculating the transformation matrix K, and finally performing K transformation on the whole point cloud of one of the prefabricated small box girders to complete the extension virtual installation between the two groups of prefabricated small box girders.

7. The precast small box girder bridge site virtual assembly installation method as claimed in claim 6, wherein, In S31, it comprises the following steps: S311、Calculate the initial point cloud density D of point i in the prefabricated small box girder point cloud 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 , and z i are the coordinates of point i in three-dimensional space; x j , y j , and 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 the point i in the prefabricated small box girder point cloud i ′, where D i is the final point cloud density for point i; D i is the initial point cloud density for point i; D cl is the initial cluster center density for the point cloud, derived 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 D i density. S313, after filtering the prefabricated small box girder point cloud according to the final point cloud density, the point cloud is divided into several clusters by 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 a loss function representing a total error measure of clustering; M is the number of clusters representing the division of the point cloud into M clusters; C m is the mth cluster; and c i is the ith point in cluster C m .

8. The precast small box girder bridge site virtual assembly installation method as claimed in claim 1, wherein, In S4, the multiple sequential changes include rotation along the center line of the side surface of the prefabricated small box girder, movement along the center line of the top surface of the prefabricated small box girder, and movement along the center line perpendicular to the side and top surface of the prefabricated small box girder.

9. The precast small box girder bridge site virtual assembly installation method as claimed in claim 8, wherein, In S4, the contact area of the prefabricated small box girder after the sequential change and the support is calculated, specifically, the contact surface coordinates of the prefabricated small box girder after the sequential change are obtained; the point cloud of the contact surface of the prefabricated small box girder and the point cloud of the contact surface of the support are converted into a Delaunay triangular network; the triangular network of the contact surface of the prefabricated small box girder and the triangular network of the contact surface of the support are superimposed and calculated to obtain the contact area of the prefabricated small box girder after the sequential change and the support; 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 sequential change, (X, Y, Z) is the coordinate of the point in the initial installation position, α is the angle of rotation along the center line of the side surface of the prefabricated small box girder, Xr is the offset of movement along the center line of the top surface of the prefabricated small box girder, and Yd is the offset of movement along the center line perpendicular to the side and top surface of the prefabricated small box girder.

10. A precast small box girder bridge site virtual assembly installation apparatus, characterized by, Comprise: 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 realize the installation method as claimed in any one of claims 1-9.

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