A simply supported beam bridge pre-assembly error transmission analysis method based on a kinematic chain

Abstract

The application discloses a simply supported beam bridge pre-assembly error transmission analysis method based on a motion chain, which comprises the following steps: scanning components by using a laser scanner to obtain point cloud data; processing the point cloud data to obtain assembly point point cloud of the components; separating bolt hole inner wall point cloud from the assembly point point cloud, and obtaining the center coordinates and the diameter of the bolt hole to simplify the model of the main beam and the secondary beam; establishing a motion chain model by using the simplified model, analyzing an error transmission path, and obtaining an error transmission formula; optimizing the position of a splicing plate in view of the assembly deviation existing in the motion chain model, and calculating the through-hole rate of the optimized bolt; and calculating the number and coordinates of the bolt holes that need to be corrected on the splicing plate based on the maximum through-hole rate of the bolt. The application can accurately describe the assembly relationship and mechanical interaction between components, and effectively analyze the error transmission and accumulation mechanism in the splicing process of large steel components.

Description

Technical Field

[0001] This invention relates to the fields of information technology and building safety management, specifically a method for analyzing the transmission of pre-assembly errors in simply supported beam bridges based on kinematic chains. Background Technology

[0002] Simply supported steel bridges are typically assembled from multiple large steel segments. Traditionally, during the component production stage, physical trial assembly is conducted in the factory to avoid matching problems during on-site assembly. However, factory trial assembly significantly impacts production efficiency, and its high cost is mainly due to factors such as labor input, assembly equipment, site limitations, and component transportation. Therefore, virtual pre-assembly is considered a potential alternative.

[0003] This method aims to achieve two key objectives by digitally simulating the assembly process of components: (1) verifying the geometric accuracy of the components; and (2) comparing the design data with the measured data to verify the assemblability of the components. However, current virtual pre-assembly methods focus on the error of a single component, while ignoring the error propagation and accumulation effects during the manufacturing and assembly process. This may lead to a significant deviation between the actual position of the finally assembled component and the design value. Summary of the Invention

[0004] The purpose of this invention is to provide a method for analyzing the pre-assembly error propagation of simply supported beam bridges based on kinematic chains, comprising the following steps:

[0005] S1. A 3D laser scanner is used to scan the area where each target component is located to obtain point cloud data of the area where each target component is located; the target component includes a main beam, a secondary beam, and a splicing plate; the main beams are connected to each other and to the secondary beams through splicing plates and bolts;

[0006] S2. Based on the coordinates of the 3D laser scanner and the RANSAC algorithm, a 3D coordinate system is established in the point cloud data of the area where the target component is located to construct a bounding box, and the point cloud of the target component is extracted from the bounding box.

[0007] S3. Obtain the coordinate range of the assembly points from the construction drawings. Based on the coordinate range of the assembly points, filter the point cloud of the target component to obtain the point cloud of the assembly points of the target component. The assembly points include the assembly points on the main beam and the secondary beam.

[0008] The assembly point includes several flat plates, and several bolt holes are provided on the flat plates;

[0009] The assembly point cloud includes the planar plate point cloud and the bolt hole inner wall point cloud;

[0010] S4. Based on the RANSAC and DBSCAN algorithms, the inner wall point cloud of bolt holes is separated from the assembly point point cloud, and the center coordinates and diameter of each bolt hole are obtained from it.

[0011] S5. Based on the splicing method of the components and the coordinates of the bolt holes, the main beam and secondary beam are simplified in model; the key features of the main beam and secondary beam are retained during the simplification process.

[0012] S6. Using the simplified main and secondary beam models, establish a kinematic chain model, analyze the error propagation path, and obtain the error propagation formula.

[0013] The kinetic chain model includes 2 Each main beam and × Each secondary beam;

[0014] S7. To address the assembly deviations in the kinematic chain model, optimize the position of the splicing plate so that the position of the bolt holes on the splicing plate corresponds one-to-one with the position of the bolt holes on the main and secondary beams, and calculate the through hole rate of the optimized bolts.

[0015] S8. Based on the maximum through-hole ratio of bolts, calculate the number of bolt holes that need to be corrected on the splicing plate using either the minimum bolt hole correction number method or the minimum component coordinate deviation method. The coordinates and diameter of the corrected bolt holes are determined; the corrected bolt holes are those bolt holes on the splice plate that still cannot be aligned with the bolt holes of the main beam and the secondary beam after the position of the splice plate has been optimized.

[0016] Furthermore, in step S1), multiple stations are set up around the target component, and a three-dimensional laser scanner is set up at the station to scan the component.

[0017] Multiple common target spheres are set between adjacent sites for point cloud registration.

[0018] Furthermore, in step S2), the method for extracting the target component includes the following steps:

[0019] S2.1. Based on the coordinates of the 3D laser scanner, construct a 3D bounding box for the point cloud data, acquire the point cloud data inside the bounding box, and denote it as the point cloud. ;

[0020] S2.2. Based on the RANSAC algorithm, fit the ground beneath the target component to obtain a ground point cloud; calculate the average elevation coordinates of the ground point cloud, denoted as... ;

[0021] S2.3 Determine whether there is a base between the target component and the ground. If so, extract the point cloud. Elevation coordinates greater than + The point cloud is used as the target component point cloud; otherwise, the point cloud is extracted. Elevation coordinates greater than The point cloud is used as the target component point cloud; This refers to the height of the base.

[0022] S2.4. Based on the RANSAC algorithm, fit the planes parallel to and perpendicular to the ground of the target component, and calculate the cross product of the normal vectors of the two planes. And rotate the target component so that Parallel to the x-axis;

[0023] The x-axis is the x-axis of the three-dimensional coordinate system in step S2).

[0024] Furthermore, in step S4), obtaining the center coordinates and diameter of the bolt hole includes the following steps:

[0025] S4.1. Based on the RANSAC algorithm, fit the planar plate to obtain the point cloud of the planar plate, and separate the point cloud of the planar plate from the assembly point cloud to obtain the point cloud of the inner wall of the bolt hole.

[0026] S4.2. Based on the plane equation of the planar plate, rotate the point cloud of the inner wall of the bolt hole to make the normal vector of the planar plate... and The axis is parallel; The axis is the three-dimensional coordinate system in step S2). axis;

[0027] S4.3 Project the point cloud of the inner wall of the bolt hole to From a plane, we obtain a two-dimensional point cloud;

[0028] The The plane is the three-dimensional coordinate system in step S2). flat;

[0029] S4.4 Based on the DBSCAN algorithm, the two-dimensional point cloud is clustered, and then the circular holes are fitted by the least squares method to finally obtain the center coordinates and diameter of each bolt hole.

[0030] Furthermore, in step S5), the simplified single main beam includes a main beam body, two main-to-main beam assembly points, and One main-secondary beam assembly point.

[0031] The main beam body has a rod-like structure. The main-to-main beam assembly points have a point-like structure and are located at both ends of the main beam body. The main-to-secondary beam assembly points have a rod-like structure and are spaced apart on the main beam body.

[0032] The key features of the main beam include the length of the main beam body, the length of the main-secondary beam assembly points, and the lateral distance between each assembly point, wherein the lateral direction is the length direction of the main beam body.

[0033] The simplified single secondary beam consists of a secondary beam body and two secondary-main beam assembly points.

[0034] The secondary beam body has a rod-like structure, and the two ends of the rod are provided with secondary-main beam assembly points with a point-like structure.

[0035] The key feature of the secondary beam includes the length of the secondary beam body.

[0036] Furthermore, in step S6), the kinematic chain model includes two parallel rows of main beams and secondary beams.

[0037] Each column of main beams is arranged with There are one main beam, and each secondary beam group contains... Each secondary beam.

[0038] The main beams in the two main beam groups are formed in a one-to-one correspondence. For each pair of main beams, a secondary beam group connects to each pair of main beams. A secondary beam group contains... Each secondary beam.

[0039] Furthermore, in step S6), the source of the error is: due to manufacturing errors in the components, each component was translated to ensure successful pre-assembly; the error propagation formula for the main beam is as follows:

[0040] (1)

[0041] (2)

[0042] In the formula:

[0043] For the first The first main beam The x-coordinate value of each assembly point =1,2,…,2 , =1,2,…,2+ ;

[0044] In the first Among the main beams, the first The distance between each assembly point and the first assembly point;

[0045] This refers to the design distance between adjacent main beams;

[0046] During the assembly process, the first The first main beam The actual x-coordinate value of each assembly point;

[0047] for Compared to The distance traveled; For the first One main beam.

[0048] Furthermore, in step S7), due to the propagation of errors, assembly deviations occur in the kinematic chain model. These assembly deviations include spacing deviations and misalignment deviations.

[0049] The spacing deviation and misalignment deviation refer to the deviations in the lateral and longitudinal distances between two adjacent main beams in the same column of main beams, which prevent the bolt holes on the splicing plate from being aligned with the bolt holes on the main and secondary beams. Therefore, the position of the splicing plate needs to be adjusted.

[0050] The optimization function for the splicing panel is shown below:

[0051] (3)

[0052] In the formula:

[0053] The rotation angle of the splicing panel. The optimal rotation angle for the splicing panel;

[0054] This is the translation distance of the splicing panel. The optimal translation distance for the splicing panels;

[0055] The center of the extracted main and secondary beam bolt hole groups ;

[0056] The center of the extracted splice plate bolt hole group .

[0057] Furthermore, in step S8), the bolt through-hole ratio The calculation formula is as follows:

[0058] (4)

[0059] (5)

[0060] (6)

[0061] In the formula:

[0062] This refers to the number of bolt holes; This indicates whether the bolt hole can be successfully installed. If it is successfully installed, the value is 1; otherwise, the value is 0.

[0063] These are the design values ​​for bolt production;

[0064] The maximum bolt diameter that can be installed in the assembly system is the maximum inscribed circle diameter of the common area of ​​the assembly system consisting of two splicing plates and the main / secondary beam horizontal plate located between the two splicing plates in the two-dimensional projection.

[0065] This is the actual diameter of the current bolt hole;

[0066] The actual center coordinates of the current bolt hole;

[0067] The coordinates of the center of the bolt holes at the same installation position for the three plates, namely two splicing plates and one main / secondary beam horizontal plate;

[0068] The diameter of the bolt holes at the same installation position for the three panels, namely two splicing panels and one main / secondary beam horizontal panel.

[0069] Furthermore, in step S8), the minimum number of bolt holes is corrected. Optimize virtual pre-assembly to minimize the number of bolt holes corrected. The calculation formula is as follows:

[0070] (7)

[0071] (8)

[0072] (9)

[0073] (10)

[0074] In the formula:

[0075] , These represent the total number of bolt holes that need to be corrected at the splicing positions of the main beam and secondary beam, respectively.

[0076] , These are the number of bolt holes at a single splice location of the main beam and secondary beam, respectively.

[0077] , Represent When assembling a main beam, the number of main-to-main beam assembly points and main-to-secondary beam assembly points on the main beam;

[0078] Main beam and main beam The deviation between them maps to the porosity. for and The distance between them;

[0079] For secondary beams and secondary beam The deviation between them maps to the porosity. for and The distance between them;

[0080] The virtual pre-assembly is optimized based on the minimum component coordinate deviation, and the optimization function is as follows:

[0081] (11)

[0082] In the formula: 2 The design value of the distance between the first and last assemblies of each main beam.

[0083] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0084] This invention presents an assembly model based on kinematic chain theory, which accurately describes the assembly relationships and mechanical interactions between components and effectively analyzes the error propagation and accumulation mechanisms during the assembly of large steel components. Simultaneously, it saves time in actual assembly processes, offering high economic benefits, wide applicability, and providing specific bolt correction solutions for factories. Attached Figure Description

[0085] Figure 1 This invention discloses a flowchart of a method for analyzing the pre-assembly error transmission of a simply supported beam bridge based on a kinematic chain;

[0086] Figure 2 This is the component assembly point extraction result of embodiment 12 of the present invention; wherein, Figure 2 (a) is a point cloud A schematic diagram, Figure 2 (b) is a schematic diagram of the target component extraction. Figure 2 (c) is a schematic diagram of the axis alignment of the target component. Figure 2 (d) is a schematic diagram of assembly point extraction;

[0087] Figure 3 This is the result of extracting bolt hole information in Embodiment 12 of the present invention; wherein, Figure 3(a) is a schematic diagram of the point cloud of the planar plate and the point cloud of the inner wall of the bolt hole. Figure 3 (b) is a schematic diagram of bolt hole clustering. Figure 3 (c) is a schematic diagram of the fitting of the bolt hole diameter and the center of the circle;

[0088] Figure 4 This is a calculation diagram of the maximum diameter of the bolt hole clearance in Embodiment 12 of the present invention; wherein, Figure 4 (a) is a schematic diagram of the assembly system. Figure 4 (b) is A schematic diagram illustrating the geometric meaning;

[0089] Figure 5 This is a simplified result of the main beam in Embodiment 12 of the present invention; wherein, Figure 5 (a) Schematic diagram of the main beam. Figure 5 (b) Simplified schematic diagram of the main beam;

[0090] Figure 6 Schematic diagram for calculation of main beam assembly points;

[0091] Figure 7 This is a simplified result of the secondary beam in Embodiment 12 of the present invention;

[0092] Figure 8 This is a schematic diagram of the component degree-of-freedom system in Embodiment 12 of the present invention; wherein, Figure 8 (a) is a schematic diagram of component assembly. Figure 8 (b) is a schematic diagram of the degrees of freedom of the component's movement;

[0093] Figure 9 This is a schematic diagram of the kinematic chain model of the two main beams in Embodiment 12 of the present invention; wherein, Figure 9 (a) is a schematic diagram of the initial state of the component. Figure 9 (b) is a schematic diagram of the state of the component after it has been moved;

[0094] Figure 10 This is a schematic diagram of the kinematic chain model of the four main beams in Embodiment 12 of the present invention; wherein, Figure 10 (a) is a schematic diagram of the initial state of the component. Figure 10 (b) is a schematic diagram of the state of the component after it has been moved;

[0095] Figure 11 This is a schematic diagram of the kinematic chain model of the six main beams in Embodiment 12 of the present invention;

[0096] in, Figure 11 (a) is a schematic diagram of the initial state of the component. Figure 11 (b) is a schematic diagram of the state of the component after it has been moved;

[0097] Figure 12This is a schematic diagram of the kinematic chain model of 2n main beams in Embodiment 12 of the present invention; wherein, Figure 12 (a) is a schematic diagram of the initial state of the component. Figure 12 (b) is a schematic diagram of the state of the component after it has been moved;

[0098] Figure 13 This is the deviation mapping calculation result of embodiment 12 of the present invention; wherein, Figure 13 (a) is a schematic diagram of the spacing deviation. Figure 13 (b) is a schematic diagram of the misalignment deviation. Figure 13 (c) Schematic diagram of main and secondary beam bolt information calculation. Figure 13 (d) is a schematic diagram for calculating the bolt information of the splicing plate; Figure 13 (e) is a schematic diagram showing the initial alignment of the bolt holes of the splicing plate with the bolt holes of the main and secondary beams;

[0099] Figure 14 This is the deviation mapping calculation result of embodiment 12 of the present invention; wherein, Figure 14 (a) is a schematic diagram of the splicing panel rotation. Figure 14 (b) is a schematic diagram of the movement of the splicing panels. Figure 14 (c) is a schematic diagram of the optimal orientation of the splicing panel;

[0100] Figure 15 This is the optimization result based on minimum component coordinate deviation in Implementation Example 12 of the present invention;

[0101] Figure 16 This is a schematic diagram of error propagation path analysis in Embodiment 12 of the present invention;

[0102] Figure 17 This is the virtual estimated through-hole ratio result of assembly bolts in Implementation Example 12 of the present invention; Figure 17 (a) is a schematic diagram of the virtual estimated through-hole ratio of assembled bolts based on the minimum bolt hole correction method. Figure 17 (b) is a schematic diagram of the virtual estimated through-hole ratio of assembly bolts based on the minimum component coordinate deviation method;

[0103] Figure 18 The result of bolt hole correction quantity in embodiment 12 of the present invention;

[0104] Figure 19 This is a schematic diagram showing the installation position of the secondary beam after the main beam of the present invention has been moved.

[0105] In the diagram: Main beam 1, secondary beam 2, splice plate 3, assembly point 4, main-to-main beam assembly point 5, main-to-secondary beam assembly point 6, secondary-to-main beam assembly point 7. Detailed Implementation

[0106] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0107] Example 1:

[0108] A method for analyzing the propagation of pre-assembly errors in simply supported beam bridges based on kinematic chains includes the following steps:

[0109] S1. A 3D laser scanner is used to scan the area where each target component is located to obtain point cloud data of the area where each target component is located; the target component includes a main beam 1, a secondary beam 2, and a splicing plate 3; the main beams 1 are connected to each other and to the secondary beams 2 through the splicing plate 3 and bolts.

[0110] S2. Based on the coordinates of the 3D laser scanner and the RANSAC algorithm, a 3D coordinate system is established in the point cloud data of the area where the target component is located to construct a bounding box, and the point cloud of the target component is extracted from the bounding box.

[0111] S3. Obtain the coordinate range of assembly point 4 from the construction drawings. Based on the coordinate range of assembly point 4, filter the point cloud of the target component to obtain the assembly point point cloud of the target component. The assembly point 4 includes each assembly point on the main beam and the secondary beam.

[0112] The assembly point includes several flat plates, and several bolt holes are provided on the flat plates;

[0113] The assembly point cloud includes the planar plate point cloud and the bolt hole inner wall point cloud;

[0114] S4. Based on the RANSAC and DBSCAN algorithms, the inner wall point cloud of bolt holes is separated from the assembly point point cloud, and the center coordinates and diameter of each bolt hole are obtained from it.

[0115] S5. Based on the splicing method of the components and the coordinates of the bolt holes, the main beam and secondary beam are simplified in model; the key features of the main beam and secondary beam are retained during the simplification process.

[0116] S6. Using the simplified main and secondary beam models, establish a kinematic chain model, analyze the error propagation path, and obtain the error propagation formula.

[0117] The kinetic chain model includes 2 Each main beam and × Each secondary beam;

[0118] S7. To address the assembly deviations in the kinematic chain model, optimize the position of the splicing plate so that the position of the bolt holes on the splicing plate corresponds one-to-one with the position of the bolt holes on the main and secondary beams, and calculate the through hole rate of the optimized bolts.

[0119] S8. Based on the maximum through-hole ratio of bolts, calculate the number of bolt holes that need to be corrected on the splicing plate using either the minimum bolt hole correction number method or the minimum component coordinate deviation method. The coordinates and diameter of the corrected bolt holes are determined; the corrected bolt holes are those bolt holes on the splice plate that still cannot be aligned with the bolt holes of the main beam and the secondary beam after the position of the splice plate has been optimized.

[0120] Example 2:

[0121] The main structure of this embodiment is the same as that of embodiment 1. Further, in step S1), multiple stations are set up around the target component, and a three-dimensional laser scanner is set up at the station to scan the component.

[0122] Multiple common target spheres are set between adjacent sites for point cloud registration.

[0123] Example 3:

[0124] The main structure of this embodiment is the same as any one of embodiments 1 to 2. Further, in step S2), the method for extracting the target component includes the following steps:

[0125] S2.1. Based on the coordinates of the 3D laser scanner, construct a 3D bounding box for the point cloud data, acquire the point cloud data inside the bounding box, and denote it as the point cloud. ;

[0126] S2.2. Based on the RANSAC algorithm, fit the ground beneath the target component to obtain a ground point cloud; calculate the average elevation coordinates of the ground point cloud, denoted as... ;

[0127] S2.3 Determine whether there is a base between the target component and the ground. If so, extract the point cloud. Elevation coordinates greater than + The point cloud is used as the target component point cloud; otherwise, the point cloud is extracted. Elevation coordinates greater than The point cloud is used as the target component point cloud; This refers to the height of the base.

[0128] S2.4. Based on the RANSAC algorithm, fit the planes parallel to and perpendicular to the ground of the target component, and calculate the cross product of the normal vectors of the two planes. And rotate the target component so that Parallel to the x-axis;

[0129] The x-axis is the x-axis of the three-dimensional coordinate system in step S2).

[0130] Example 4:

[0131] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Further, in step S4), obtaining the center coordinates and diameter of the bolt hole includes the following steps:

[0132] S4.1. Based on the RANSAC algorithm, fit the planar plate to obtain the point cloud of the planar plate, and separate the point cloud of the planar plate from the assembly point cloud to obtain the point cloud of the inner wall of the bolt hole.

[0133] S4.2. Based on the plane equation of the planar plate, rotate the point cloud of the inner wall of the bolt hole to make the normal vector of the planar plate... and The axis is parallel; The axis is the three-dimensional coordinate system in step S2). axis;

[0134] S4.3 Project the point cloud of the inner wall of the bolt hole to From a plane, we obtain a two-dimensional point cloud;

[0135] The The plane is the three-dimensional coordinate system in step S2). flat;

[0136] S4.4 Based on the DBSCAN algorithm, the two-dimensional point cloud is clustered, and then the circular holes are fitted by the least squares method to finally obtain the center coordinates and diameter of each bolt hole.

[0137] Example 5:

[0138] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Further, in step S5), the simplified single main beam includes a main beam body, two main-to-main beam assembly points 5, and... There are 6 main and secondary beam assembly points.

[0139] The main beam body has a rod-like structure. The main-to-main beam assembly points 5 have a point-like structure and are located at both ends of the main beam body. The main-to-secondary beam assembly points 6 have a rod-like structure and are spaced apart on the main beam body.

[0140] The key features of the main beam include the length of the main beam body, the length of the main-secondary beam assembly point 6, and the lateral distance between each assembly point, wherein the lateral direction is the length direction of the main beam body.

[0141] The simplified single secondary beam consists of a secondary beam body and two secondary-main beam assembly points 7.

[0142] The secondary beam body has a rod-like structure, and the two ends of the rod are provided with secondary-main beam assembly points 7 with a point-like structure.

[0143] The key feature of the secondary beam includes the length of the secondary beam body.

[0144] Example 6:

[0145] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Further, in step S6), the kinematic chain model includes two parallel rows of main beams and secondary beams.

[0146] Each column of main beams is arranged with There are one main beam, and each secondary beam group contains... Each secondary beam.

[0147] The main beams in the two main beam groups are formed in a one-to-one correspondence. For each pair of main beams, a secondary beam group connects to each pair of main beams. A secondary beam group contains... Each secondary beam.

[0148] Example 7:

[0149] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Further, in step S6), the source of the error is: due to manufacturing errors in the components, each component is translated to ensure successful pre-assembly; the error propagation formula of the main beam is as follows:

[0150] (1)

[0151] (2)

[0152] In the formula:

[0153] For the first The first main beam The design x-coordinate value of each assembly point =1,2,…,2 , =1,2,…,2+ ;

[0154] In the first Among the main beams, the first The distance between each assembly point and the first assembly point;

[0155] This refers to the design distance between adjacent main beams;

[0156] During the assembly process, the first The first main beam The actual x-coordinate value of each assembly point;

[0157] for Compared to The distance traveled; For the first One main beam.

[0158] Example 8:

[0159] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, in step S7), due to the transmission of error, the kinematic chain model has an assembly deviation.

[0160] The assembly deviations include spacing deviations and misalignment deviations.

[0161] The spacing deviation and misalignment deviation refer to the deviations in the lateral and longitudinal distances between two adjacent main beams in the same column of main beams, which prevent the bolt holes on the splicing plate from being aligned with the bolt holes on the main and secondary beams. Therefore, the position of the splicing plate needs to be adjusted.

[0162] The optimization function for the splicing panel is shown below:

[0163] (3)

[0164] In the formula:

[0165] The rotation angle of the splicing panel. The optimal rotation angle for the splicing panel;

[0166] This is the translation distance of the splicing panel. The optimal translation distance for the splicing panels;

[0167] The center of the extracted main and secondary beam bolt hole groups ;

[0168] The center of the extracted splice plate bolt hole group .

[0169] Example 9:

[0170] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Further, in step S8), the bolt through-hole ratio is... The calculation formula is as follows:

[0171] (4)

[0172] (5)

[0173] (6)

[0174] In the formula:

[0175] This refers to the number of bolt holes; This indicates whether the bolt hole can be successfully installed. If it is successfully installed, the value is 1; otherwise, the value is 0.

[0176] These are the design values ​​for bolt production;

[0177] The maximum bolt diameter that can be installed in the assembly system is the maximum inscribed circle diameter of the common area of ​​the assembly system consisting of two splicing plates and the main / secondary beam horizontal plate located between the two splicing plates in the two-dimensional projection.

[0178] This is the actual diameter of the current bolt hole;

[0179] The actual center coordinates of the current bolt hole;

[0180] The coordinates of the center of the bolt holes at the same installation position for the three plates, namely two splicing plates and one main / secondary beam horizontal plate;

[0181] The diameter of the bolt holes at the same installation position for the three panels, namely two splicing panels and one main / secondary beam horizontal panel.

[0182] Example 10:

[0183] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Further, in step S8),

[0184] Based on minimum bolt hole correction quantity Optimize virtual pre-assembly to minimize the number of bolt holes corrected. The calculation formula is as follows:

[0185] (7)

[0186] (8)

[0187] (9)

[0188] (10)

[0189] In the formula:

[0190] , These represent the total number of bolt holes that need to be corrected at the splicing positions of the main beam and secondary beam, respectively.

[0191] , These are the number of bolt holes at a single splice location of the main beam and secondary beam, respectively.

[0192] , Represent When assembling a main beam, the number of main-to-main beam assembly points and main-to-secondary beam assembly points on the main beam;

[0193] Main beam and main beam The deviation between them maps to the porosity. for and The distance between them;

[0194] For secondary beams and secondary beam The deviation between them maps to the porosity. for and The distance between them;

[0195] The virtual pre-assembly is optimized based on the minimum component coordinate deviation, and the optimization function is as follows:

[0196] (11)

[0197] In the formula: 2 The design value of the distance between the first and last assemblies of each main beam.

[0198] Example 11:

[0199] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Furthermore, in view of the problem that the research on error transmission and accumulation mechanism in the current virtual pre-assembly technology is insufficient, this invention provides an error transmission analysis method for pre-assembly of simply supported beam bridges based on kinematic theory.

[0200] The present invention employs the following method:

[0201] S101. Use a 3D laser scanner to scan a fixed area of ​​the component to obtain point cloud data of the component and splicing panel;

[0202] S102. For the component point cloud data in step S101, the target component is extracted based on the scanner coordinates and RANSAC algorithm, and the target component is segmented based on the prior knowledge of the construction drawings to obtain the assembly point cloud.

[0203] S103. For the assembly point cloud extracted in step S102, the RANSAC and DBSCAN algorithms are used to segment and calculate the bolt hole information (center coordinates and diameter) of the assembly points and splicing plates.

[0204] S104. Based on the assembly points and bolt hole information of the splicing plate obtained in step 103, establish a method for calculating the bolt through hole ratio when assembling the splicing plate and components in the actual assembly system.

[0205] S105. Based on the component point cloud data obtained in step S101, the main beam component and the secondary beam component are simplified according to the location of the assembly point and the geometric dimensions of the component.

[0206] S106. Based on the simplified model obtained in step S105, determine the degrees of freedom for component movement, establish a kinematic chain model for the assembly of two main beams and three secondary beams, and analyze the error propagation path.

[0207] S107. Based on the simplified model obtained in step S105, establish a kinematic chain model for the assembly of 4 main beams and 6 secondary beams, and analyze the error propagation path.

[0208] S108. Based on the simplified model obtained in step S105, establish the kinematic chain model for the assembly of 6 main beams and 9 secondary beams, and analyze the error propagation path.

[0209] S109. Based on the simplified model obtained in step S105, establish a kinematic chain model for the assembly of 2n main beams and 3n secondary beams, analyze the error propagation path, and derive the kinematic chain model to the assembly of any number of components to obtain the error propagation formula.

[0210] S110. Based on the kinematic chain model obtained in step 108, establish a mapping between component assembly deviation and bolt through-hole ratio. The assembly deviation is divided into two categories: spacing deviation and misalignment deviation. The splicing plate is optimized by rotation and translation. The objective function is to minimize the sum of the Euclidean distances of all circle centers, and then the bolt through-hole ratio is calculated.

[0211] S111. Based on the kinematic chain model and deviation mapping obtained in steps 109 and 110, the virtual pre-assembly is optimized using two methods: the minimum number of bolt hole corrections and the minimum component coordinate deviation, to obtain the optimization results.

[0212] Preferably, step S101 includes:

[0213] Different stations are set up around the target component, with at least three common target spheres placed between adjacent stations to complete the scanning of point cloud data around the component. The point cloud data of each station obtained from the scan are registered to make strong correspondence between the target spheres of adjacent stations, thereby completing the fine registration of the point cloud and obtaining the overall point cloud data of the component.

[0214] Preferably, step S102 includes:

[0215] During scanning, the scanner surrounds the points around the component. First, a bounding box for the component's point cloud is created based on the scanner coordinates, and the internal point cloud is then used as the bounding box. The RANSAC algorithm was used to fit the ground, and the average elevation coordinates of the ground point cloud were calculated as follows: Since the components are typically placed on a steel base and timber, assume the height of the steel base and timber is... Therefore, the elevation coordinates are taken to be greater than 10 ... The point cloud of the target component is used as the point cloud of the component. Then, the two principal planes of the component are fitted based on the RANSAC algorithm, and the cross product of the normal vectors of the two principal planes is calculated. Rotate the component to and Axis alignment is achieved by parallelizing the axes. Finally, based on prior knowledge of the construction drawings, the coordinate range of the assembly points is queried, and the point cloud of the assembly points is obtained through point cloud pass-through filtering. Similarly, the point cloud of the splicing plate can be obtained.

[0216] Preferably, step S103 includes:

[0217] The point clouds in the assembly points and splicing panels consist of bolt hole groups and two planar plates on either side. First, the RANSAC algorithm is used to fit the point cloud of the planar plates to separate the point clouds of the planar plates from those of the inner walls of the bolt holes. Then, based on the planar equations of the planar plates, the bolt hole groups are rotated and projected onto... Two-dimensional point cloud obtained from a plane Then, the DBSCAN algorithm is used to cluster the bolt hole group into individual bolt holes. The center coordinates and diameter of each bolt hole are obtained by performing two-dimensional circle fitting based on the least squares method.

[0218] Preferably, step S104 includes:

[0219] In actual assembly, for bolts to be successfully installed, they need to pass through both the splicing plates and the assembly system composed of the components (there are two splicing plates on the upper and lower sides, with the component assembly point in the middle). Therefore, the through-hole ratio... The calculation can be performed using the following formula:

[0220]

[0221]

[0222] in Porosity; This indicates whether the bolt hole can be successfully installed. If it can be installed successfully, the value is 1; otherwise, the value is 0. This refers to the number of bolt holes; The maximum bolt diameter that can be installed in the assembly system; These are the design values ​​for bolt production.

[0223] When the assembled system is projected into two dimensions, it consists of three circles with slightly different centers and diameters, sharing a common area. Therefore, it can be assumed that for the bolts to be successfully installed, It needs to be smaller than the diameter of the largest inscribed circle of this common area. , The calculation method is shown below.

[0224]

[0225] in, This indicates the diameter currently being calculated; Indicates the coordinates currently being calculated. Represents the coordinates of three circles (two splicing panels and one component assembly point); This represents the diameter of the three circles.

[0226] Preferably, step S105 includes:

[0227] Based on the splicing method of the main beam and secondary beam, the assembly points and key geometric dimensions of the components are retained to simplify the components. Since the assembly points consist of bolt hole groups, the assembly point coordinates and geometric dimensions of the components are calculated based on the bolt hole coordinates obtained in step 104.

[0228] Preferably, step S106 includes:

[0229] Based on the simplified model obtained in step 105, a pre-assembled model with 2 main beams and 3 secondary beams is established. The influence of the translation of the secondary beams on the total open area ratio between the main beams and secondary beams and the transmission of errors in the 5 components are analyzed.

[0230] Preferably, step S107 includes:

[0231] Based on the simplified model obtained in step 105, a pre-assembled model with 4 main beams and 6 secondary beams was established. The effects of the translation of the main beams and secondary beams on the total open area ratio between the main beams and secondary beams and between the main beams were analyzed, as well as the transmission of errors among the 10 components.

[0232] Preferably, step S108 includes:

[0233] Based on the simplified model obtained in step 105, a pre-assembled model with 6 main beams and 9 secondary beams was established. The effects of the translation of the main beams and secondary beams on the total open area ratio between the main beams and secondary beams and between the main beams were analyzed, as well as the transmission of errors among the 15 components.

[0234] Preferably, step S109 includes:

[0235] Establish Each main beam and The kinematic chain model for assembling individual beams is used to analyze the error propagation path, determine the degrees of freedom, and derive the error propagation formula for assembling any number of components.

[0236]

[0237]

[0238] Preferably, step S110 includes:

[0239] For bolted components, assembly deviations at each assembly point will cause changes in the bolt hole ratio. Assembly deviations can be divided into spacing deviations and misalignment deviations. Spacing deviations occur when the distance between two components is not equal to the design value, while misalignment deviations occur when two components that should be aligned are misaligned. An optimal state that maximizes the bolt hole ratio can be found by rotating and translating the splicing plate. To reduce computational costs, the sum of the Euclidean distances between the centers of the bolt holes at the assembly points of the splicing plate and the components is used as the objective function. When the sum of the Euclidean distances is minimized, the splicing plate is in its optimal state, and the bolt hole ratio at this state is used as a mapping of the current assembly deviation.

[0240] Preferably, step S111 includes:

[0241] For bolted connections, the ultimate goal is to minimize the number of bolt hole corrections. Correcting bolt holes in splice plates is more convenient than correcting bolt holes in the main components. Therefore, the first method optimizes the virtual pre-assembly based on the minimum number of bolt hole corrections to determine the number of splice plates requiring correction. The second method considers the component coordinates, ensuring the coordinates at both ends of the component match the design values, and then optimizes the internal components to determine the number of splice plates requiring correction.

[0242] Example 12:

[0243] The main structure of this embodiment is the same as any one of embodiments 1 to 11, and further, as follows: Figure 1 As shown, this invention discloses a flowchart of a method for analyzing the transmission of pre-assembly errors in simply supported beam bridges based on kinematic chains.

[0244] S101. Use a 3D laser scanner to scan a fixed area of ​​the component to obtain point cloud data of the component;

[0245] In practice, different stations are set up around the target component, with at least three common target spheres placed between adjacent stations to scan the point cloud data around the component. The point cloud data of each station is then registered to ensure a strong correspondence between the target spheres of adjacent stations, guaranteeing that the positional deviation is within 1mm. This completes the fine registration of the point cloud and yields the overall point cloud data of the component.

[0246] S102. For the component point cloud data in step S101, the target component is extracted based on the scanner coordinates and RANSAC algorithm, and the target component is segmented based on the prior knowledge of the construction drawings to obtain the assembly point cloud.

[0247] In practice, a bounding box for the component point cloud is created based on the scanner coordinates to obtain the internal component point cloud, such as... Figure 2 As shown in (a), the RANSAC algorithm was used for ground fitting, with a distance threshold coefficient of sigma=0.02, a random sampling number of n=5, and a maximum number of iterations of 1000, to obtain the ground point cloud. The average elevation coordinates of all ground point clouds were calculated. The height of the steel base and the wood were recorded on site. ,extract Elevation coordinates greater than The point cloud is obtained as the component point cloud. Figure 2 As shown in (b), the RANSAC algorithm is used to fit the component, obtaining two principal planes. The cross product of the normal vectors of the two principal planes is then calculated. As the main direction of the component, rotate the component to... and The axes are parallel, such as Figure 2 As shown in (c). Finally, based on prior knowledge of the construction drawings, a direct-pass filtering algorithm is used to filter and obtain the component assembly points based on the specific coordinates of the assembly points in the drawings, as shown in... Figure 2 As shown in (d).

[0248] S103. For the assembly point cloud extracted in step S102, the RANSAC and DBSCAN algorithms are used to segment and calculate the bolt hole information (center coordinates and diameter) of the assembly points and splicing plates.

[0249] In practice, the RANSAC algorithm is first used to fit the planar plate with bolt hole group, sigma=0.01, random sampling points n=5, and maximum number of iterations 500, to obtain the point cloud of the planar plate and the point cloud of the inner wall of the bolt hole group. ,like Figure 3 As shown in (a). Next, based on the fitted planar plate normal vector... ,Will Rotate to and The axis is parallel and projected onto the plane. Two-dimensional bolt hole group obtained from a plane Then, the DBSCAN algorithm is used to... Density clustering was performed to obtain the values ​​for each bolt hole. ,like Figure 3 As shown in (b). Finally, circle fitting is performed based on the least squares method, as follows. Figure 3 As shown in (c), the center coordinates and diameter of each bolt hole are obtained.

[0250] S104. Based on the assembly points and bolt hole information of the splicing plate obtained in step 103, establish a method for calculating the bolt through hole ratio when assembling the splicing plate and components in the actual assembly system.

[0251] In practical implementation, the bolt through-hole ratio This can be considered as the percentage of bolts that can be successfully installed out of a group of bolt holes, and can be calculated using the following formula:

[0252]

[0253]

[0254] in Porosity; This indicates whether the bolt hole can be successfully installed. If it can be installed successfully, the value is 1; otherwise, the value is 0. This refers to the number of bolt holes; The maximum bolt diameter that can be installed in the assembly system; These are the design values ​​for bolt production. The geometric meaning of is the diameter of the largest inscribed circle of the common area of ​​the assembly system composed of the upper splicing plate, components, and lower splicing plate in a two-dimensional projection, such as... Figure 4 As shown in (a) and (b). It can be calculated using the following formula:

[0255]

[0256] in, This indicates the diameter currently being calculated; This indicates the coordinates of the center of the circle being calculated. Represents the coordinates of the centers of the three circles (two splicing panels and one component assembly point); This represents the diameter of the three circles.

[0257] S105. Based on the component point cloud data obtained in step S101, the main beam component and the secondary beam component are simplified according to the location of the assembly point and the geometric dimensions of the component.

[0258] In practice, the main beam is first simplified, and its specific structure and assembly point locations are as follows: Figure 5 As shown in (a), there are 5 assembly points: assembly points 1 and 5 connect to the main beam, and assembly points 2, 3, and 4 connect to the secondary beams. Therefore, the coordinates of these five assembly points should be a key factor for simplification, for any main beam. Constructing the main beam features , The specific meanings of each item are as follows: Figure 5 As shown in (b), that is, each assembly point and the leftmost point The distance. and For example, Figure 6 As shown, it can be calculated using the following formula:

[0259]

[0260]

[0261] Similarly, the secondary beam can be simplified, and the simplification process is as follows: Figure 7 As shown.

[0262] S106. Based on the simplified model obtained in step S105, determine the degrees of freedom for component movement, establish a kinematic chain model for the assembly of two main beams and three secondary beams, and analyze the error propagation path.

[0263] In practice, the first step is to determine the degrees of freedom for component movement. During actual assembly, the assembly method for the main beams and secondary beams is as follows: Figure 8 As shown in (a), it is necessary to ensure that the distance between the main beams on both sides is equal to the design value. Therefore, the degree of freedom of the component is set to 1, along... Axial translation, such as Figure 8 As shown in (b). Next, the assembly system of two main beams and three secondary beams is analyzed. The main beams are defined as... , .in Indicates the first The first component There are one assembly point. The initial state is as follows: Figure 9 As shown in (a), due to manufacturing errors of the components, and , and , and The position is off. Therefore, Need to shift to the right This increases the bolt through-hole rate. ,like Figure 9 As shown in (b).

[0264] The error of the secondary beam is calculated based on the error of the main beam, see [reference]. Figure 19The dashed line represents the misaligned enclosure formed by the assembly points of the main and secondary beams of the two opposing main beams. The secondary beams are mounted on the centerline of the misaligned enclosure by default.

[0265] S107. Based on the simplified model obtained in step S105, establish a kinematic chain model for the assembly of 4 main beams and 6 secondary beams, and analyze the error propagation path.

[0266] In practice, the initial assembly state is as follows: Figure 10 As shown in (a), at this time, due to manufacturing errors, and , and The distances between them are not equal to the design values ​​and need to be optimized through translation. Meanwhile, due to the connection of the secondary beams... and , and There will also be discrepancies between them. Therefore, we assume... The position remains unchanged, in order to improve It is necessary to move , Compared to move , Compared to move At this point, it can be discovered that... The absolute distance moved is , The propagation of the movement error gave ,like Figure 10 As shown in (b).

[0267] S108. Based on the simplified model obtained in step S105, establish the kinematic chain model for the assembly of 6 main beams and 9 secondary beams, and analyze the error propagation path.

[0268] In practice, the initial assembly state is as follows: Figure 11 As shown in (a), the state after the movement is as follows: Figure 11 As shown in (b). It can be found that The propagation of the movement error gave , The propagation of the movement error gave and , The propagation of the movement error gave .

[0269] S109. Based on the simplified model obtained in step S105, establish a kinematic chain model for the assembly of 2n main beams and 3n secondary beams, analyze the error propagation path, and derive the kinematic chain model to the assembly of any number of components to obtain the error propagation formula.

[0270] In practical implementation, based on the above analysis, the kinematic chain for assembling 2n main beams is derived. Initially, the coordinates of any assembly point are... It can be calculated using the following formula:

[0271]

[0272] in The main beam features proposed in step 5; This refers to the design distance between the main beams. The initial state of the components is as follows: Figure 12 As shown in (a), the state after the movement is as follows: Figure 12 As shown in (b). Compared to The distance traveled is defined as .in, Do not move Compared to Move. The assembly point of the moved component is defined as follows: , It can be calculated using the following formula:

[0273]

[0274] S110. Based on the kinematic chain model obtained in step 108, establish a mapping between component assembly deviation and bolt through-hole ratio. The assembly deviation is divided into two categories: spacing deviation and misalignment deviation. The splicing plate is optimized by rotation and translation. The objective function is to minimize the sum of the Euclidean distances of all circle centers, and then the bolt through-hole ratio is calculated.

[0275] In practice, assembly deviations are divided into two categories: spacing deviations and misalignment deviations, such as... Figure 13 As shown in (a) and (b), for different deviation types and deviation distances, the optimal splicing plate posture can be obtained by rotating and translating the splicing plate, thereby improving the through-hole ratio. Assume the center of the extracted bolt hole group from the component is... ,like Figure 13 As shown in (c), the center of the bolt hole group extracted from the splicing plate is... ,like Figure 13 As shown in (d). First, [the following is done] The center of the first bolt and In Alignment, such as Figure 13 As shown in (e). Next, the splicing panels are translated and rotated, both relative to... Proceeding, as illustrated in the following diagram Figure 14 As shown in (a) and (b). Among them, The following optimization function is used for optimization:

[0276]

[0277] in For the optimal rotation angle, The optimal translation distance is achieved. The optimized splicing panel orientation is as follows: Figure 14 As shown in (c). After obtaining the optimal splicing plate state, the bolt through hole ratio is calculated using the calculation method in step 104, thereby obtaining the mapping of the assembly deviation bolt through hole ratio.

[0278] S111. Based on the kinematic chain model and deviation mapping obtained in steps 109 and 110, the virtual pre-assembly is optimized using two methods: the minimum number of bolt hole corrections and the minimum component coordinate deviation, to obtain the optimization results.

[0279] In practice, the minimum number of bolt holes should be adjusted first. Optimize virtual pre-assembly. The calculation formula is as follows:

[0280]

[0281]

[0282]

[0283] in and These represent the total number of bolt holes that need to be corrected at the splicing positions of the main beam and secondary beam, respectively. and These are the number of bolt holes at a single splice location of the main beam and secondary beam, respectively. and Represent The number of splicing positions of the main beam and secondary beam when assembling a component; for and The deviation between components (i.e., between main beams) maps to the open area ratio. for and The distance between them; for and The deviation between components (i.e., between secondary beams) maps to the open area ratio. for and The distance between them. Therefore, the optimization function is as follows:

[0284]

[0285] Next, virtual pre-assembly optimization is performed based on the minimum component coordinate deviation using the second method. This requires that the distance between the first and last parts of the assembled component is equal to the design value, such as... Figure 15 As shown, the optimization function is as follows:

[0286]

[0287] in The design value for the first and last distances of the six main beams to be assembled.

[0288] The movement error results of the virtual pre-assembled main beam components (6 main beams and 9 secondary beams) in the implementation example are shown in Table 1; the cumulative error at each assembly point is shown in Table 2; and the error propagation path is shown in Table 2. Figure 16 As shown; the bolt through-hole ratios of the two optimization methods are as follows: Figure 17 As shown; the number of bolt holes that need to be corrected is as follows. Figure 18 As shown;

[0289]

[0290]

[0291] The above experimental results demonstrate that the method for analyzing the error transmission of pre-assembly of simply supported beam bridges based on kinematic chains disclosed in this invention can complete the virtual pre-assembly of steel components of simply supported beam bridges, establish a corresponding kinematic chain model, analyze the error transmission between components and the cumulative error of each assembly point, achieve pre-assembly optimization, and obtain the specific number of bolt hole corrections. The method described in this invention is indeed effective.

Claims

1. A method for analyzing the propagation of pre-assembly errors in simply supported beam bridges based on kinematic chains, characterized in that, Includes the following steps: S1. A three-dimensional laser scanner is used to scan the area where each target component is located to obtain point cloud data of the area where each target component is located; the target component includes a main beam (1), a secondary beam (2), and a splicing plate (3); the main beam (1) is connected to each other and to the secondary beam (2) through the splicing plate (3) and bolts; S2. Based on the coordinates of the 3D laser scanner and the RANSAC algorithm, a 3D coordinate system is established in the point cloud data of the area where the target component is located to construct a bounding box, and the point cloud of the target component is extracted from the bounding box. S3. Obtain the coordinate range of assembly point (4) from the construction drawing. Based on the coordinate range of assembly point (4), filter the point cloud of the target component to obtain the assembly point cloud of the target component. The assembly point (4) includes each assembly point on the main beam and the secondary beam. The assembly point includes several flat plates, and several bolt holes are provided on the flat plates; The assembly point cloud includes the planar plate point cloud and the bolt hole inner wall point cloud; S4. Based on the RANSAC and DBSCAN algorithms, the inner wall point cloud of bolt holes is separated from the assembly point point cloud, and the center coordinates and diameter of each bolt hole are obtained from it. S5. Based on the splicing method of the components and the coordinates of the bolt holes, the main beam and secondary beam are simplified in model; the key features of the main beam and secondary beam are retained during the simplification process. S6. Using the simplified main and secondary beam models, establish a kinematic chain model, analyze the error propagation path, and obtain the error propagation formula. The kinetic chain model includes 2 Each main beam and × Each secondary beam; The kinematic chain model includes secondary beam groups and two parallel rows of main beam groups; each row of main beam groups contains... Each main beam is formed by corresponding main beams in two rows of main beam groups. For each pair of main beams, a secondary beam group connects to each pair of main beams, and each secondary beam group has... Each secondary beam; The source of the error is as follows: due to manufacturing errors in the components, each component was translated to ensure successful pre-assembly; the error propagation formula for the main beam is shown below: （1） （2） In the formula: For the first The first main beam The x-coordinate value of each assembly point =1,2,…,2 , =1,2,…,2+ ; In the first Among the main beams, the first The distance between each assembly point and the first assembly point; This refers to the design distance between adjacent main beams; During the assembly process, the first The first main beam The actual x-coordinate value of each assembly point; for Compared to The distance traveled; For the first One main beam; S7. To address the assembly deviations in the kinematic chain model, optimize the position of the splicing plate so that the position of the bolt holes on the splicing plate corresponds one-to-one with the position of the bolt holes on the main and secondary beams, and calculate the through hole rate of the optimized bolts. S8. Based on the maximum through-hole ratio of bolts, calculate the number of bolt holes that need to be corrected on the splicing plate using either the minimum bolt hole correction number method or the minimum component coordinate deviation method. The coordinates and diameter of the corrected bolt holes are determined; the corrected bolt holes are those bolt holes on the splice plate that still cannot be aligned with the bolt holes of the main beam and the secondary beam after the position of the splice plate has been optimized.

2. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S1), multiple stations are set up around the target component, and a three-dimensional laser scanner is set up at the station to scan the component; Multiple common target spheres are set between adjacent sites for point cloud registration.

3. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S2), the method for extracting the target component includes the following steps: S2.

1. Based on the coordinates of the 3D laser scanner, construct a 3D bounding box for the point cloud data, acquire the point cloud data inside the bounding box, and denote it as the point cloud. ; S2.

2. Based on the RANSAC algorithm, fit the ground beneath the target component to obtain a ground point cloud; calculate the average elevation coordinates of the ground point cloud, denoted as... ; S2.3 Determine whether there is a base between the target component and the ground. If so, extract the point cloud. Elevation coordinates greater than + The point cloud is used as the target component point cloud; otherwise, the point cloud is extracted. Elevation coordinates greater than The point cloud is used as the target component point cloud; This refers to the height of the base. S2.

4. Based on the RANSAC algorithm, fit the planes parallel to and perpendicular to the ground of the target component, and calculate the cross product of the normal vectors of the two planes. And rotate the target component so that Parallel to the x-axis; The x-axis is the x-axis of the three-dimensional coordinate system in step S2).

4. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S4), obtaining the center coordinates and diameter of the bolt hole includes the following steps: S4.

1. Based on the RANSAC algorithm, fit the planar plate to obtain the point cloud of the planar plate, and separate the point cloud of the planar plate from the assembly point cloud to obtain the point cloud of the inner wall of the bolt hole. S4.

2. Based on the plane equation of the planar plate, rotate the point cloud of the inner wall of the bolt hole to make the normal vector of the planar plate... and The axis is parallel; The axis is the three-dimensional coordinate system in step S2). axis; S4.3 Project the point cloud of the inner wall of the bolt hole to From a plane, we obtain a two-dimensional point cloud; The The plane is the three-dimensional coordinate system in step S2). flat; S4.4 Based on the DBSCAN algorithm, the two-dimensional point cloud is clustered, and then the circular holes are fitted by the least squares method to finally obtain the center coordinates and diameter of each bolt hole.

5. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S5), the simplified single main beam includes a main beam body, two main-to-main beam assembly points (5), and One main-secondary beam assembly point (6); The main beam body has a rod-like structure; the main-to-main beam assembly point (5) has a point-like structure and is set at both ends of the main beam body; the main-to-secondary beam assembly point (6) has a rod-like structure and is set at intervals on the main beam body; The key features of the main beam include the length of the main beam body, the length of the main-secondary beam assembly point (6), and the lateral distance between each assembly point, wherein the lateral direction is the length direction of the main beam body; The simplified single secondary beam includes a secondary beam body and two secondary-main beam assembly points (7); The secondary beam body has a rod-like structure, and the two ends of the rod are provided with secondary-main beam assembly points (7) with a point-like structure. The key feature of the secondary beam includes the length of the secondary beam body.

6. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S7), due to the propagation of errors, assembly deviations occur in the kinematic chain model; The assembly deviations include spacing deviations and misalignment deviations; The spacing deviation and misalignment deviation refer to the deviation in the lateral and longitudinal distances between two adjacent main beams in the same column of main beams, which makes it impossible for the bolt holes on the splicing plate to be aligned with the bolt holes on the main and secondary beams. Therefore, the position of the splicing plate needs to be adjusted. The optimization function for the splicing panel is shown below: （3） In the formula: The rotation angle of the splicing panel. The optimal rotation angle for the splicing panel; This is the translation distance of the splicing panel. The optimal translation distance for the splicing panels; The center of the extracted main and secondary beam bolt hole groups ; The center of the extracted splice plate bolt hole group .

7. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 6, characterized in that: In step S8), the bolt through-hole ratio The calculation formula is as follows: （4） （5） （6） In the formula: This refers to the number of bolt holes; This indicates whether the bolt hole can be successfully installed. If it is successfully installed, the value is 1; otherwise, the value is 0. These are the design values ​​for bolt production; The maximum bolt diameter that can be installed in the assembly system is the maximum inscribed circle diameter of the common area of ​​the assembly system consisting of two splicing plates and the main / secondary beam horizontal plate located between the two splicing plates in the two-dimensional projection. This is the actual diameter of the current bolt hole; The actual center coordinates of the current bolt hole; The coordinates of the center of the bolt holes at the same installation position for the three plates, namely two splicing plates and one main / secondary beam horizontal plate; The diameter of the bolt holes at the same installation position for the three panels, namely two splicing panels and one main / secondary beam horizontal panel.

8. The method for analyzing the pre-assembly error propagation of a simply supported beam bridge based on kinematic chains according to claim 1, characterized in that: In step S8), Based on minimum bolt hole correction quantity Optimize virtual pre-assembly to minimize the number of bolt holes corrected. The calculation formula is as follows: （7） （8） （9） （10） In the formula: , These represent the total number of bolt holes that need to be corrected at the splicing positions of the main beam and secondary beam, respectively. , These are the number of bolt holes at a single splice location of the main beam and secondary beam, respectively. , Represent When assembling a main beam, the number of main-to-main beam assembly points and main-to-secondary beam assembly points on the main beam; Main beam and main beam The deviation between them maps to the porosity. for and The distance between them; For secondary beams and secondary beam The deviation between them maps to the porosity. for and The distance between them; The virtual pre-assembly is optimized based on the minimum component coordinate deviation, and the optimization function is as follows: （11） In the formula: 2 The design value of the distance between the first and last assemblies of each main beam.

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