Large steel truss segment assembly multi-purpose real-time digital monitoring method and system

Abstract

The application discloses a pre-assembly-free large steel truss section assembly multi-point real-time digital monitoring method and system, belongs to the technical field of bridge construction monitoring, solves the problem that the existing method cannot realize multi-point simultaneous measurement and cannot realize real-time feedback when the optical prism method is used for steel pipe section assembly positioning, and the method comprises the following steps: segment main pipe blanking scanning, segment main pipe line laying monitoring, segment main pipe assembly deviation rectification, and flange plate line laying fixing; the application provides a pre-assembly-free large steel truss section assembly multi-point real-time digital monitoring method, multiple visual measurements are adopted to avoid the visual line blockage of one-way measurement, and time waste caused by repeated conversion of measurement stations is avoided; the end centroid of the steel pipe can be accurately controlled, and uncertain errors caused by the measurement of a single waist line of the circular pipe are avoided; and a prior measurement recording method is adopted, only three mark points of the main pipe body are measured in the formal assembly stage, and the efficiency of line laying measurement is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction monitoring technology, specifically relating to a multi-view real-time digital monitoring method and system for the assembly of large steel truss segments without pre-assembly. Background Technology

[0002] The construction of ultra-long and large steel structures generally relies on multi-segment assembly. For example, the main arches of large-span steel-concrete composite arch bridges, rigid frame arch bridges, and steel box arch bridges often depend on pre-assembly technology for their steel truss segments. This technology uses the geometry of preceding segments to assist in the positioning and layout of subsequent segments, resulting in significant costs in terms of land, facilities, personnel, and materials. On one hand, to ensure the smoothness of the main arch's alignment and the alignment of bolt holes between adjacent main arch segments after assembly, existing technologies typically use pre-placed adjacent segments to assist in positioning the current segment. These preceding segments usually consist of multiple segments, i.e., an "n+1" pattern. This manufacturing method occupies a long, narrow site exceeding 100 meters, consuming vast amounts of land resources. Furthermore, in mountainous, steep, and complex terrain, large-scale processing is extremely difficult, requiring the construction of additional steel work platforms. On the other hand, because the segmental steel pipe members are positioned and laid out using the pipe side waistline measurement method, the measurement process requires repeated adjustments, and the members are ultimately fixed using a jig. This method not only has poor estimation accuracy of the actual centroid and central axis of the steel pipe, but also has low positioning efficiency. In addition, if the subsequent segment welding and positioning is limited by the site, it is often necessary to move the preceding segments, and repositioning them requires additional measurement and adjustment, reducing work efficiency. Overall, the pre-assembly of large-scale, multi-segment units results in low turnover rate of auxiliary workpieces, long time for repeated adjustments, and high requirements for personnel skills, which seriously restricts the efficiency of main arch assembly and forming.

[0003] Therefore, if the individual manufacturing of large main arch steel truss segments can be achieved, the process of adjusting preceding segments can be eliminated, significantly reducing land use and the investment of large amounts of personnel and equipment. It can also solve the problem of difficult assembly and manufacturing under complex mountainous terrain conditions. However, the independent manufacturing of large steel truss segments places extremely high demands on the positioning accuracy of the member axes. Not only must the axis be smooth, but all connecting bolt holes must be aligned at once without the assistance of adjacent segments. The number of bolt holes for the internal flange splicing between segments is generally between 24 and 32. On a large scale with pipe diameters exceeding 1m and pipe spacing exceeding 10m, ensuring millimeter-level spatial positioning accuracy (±1mm) for each bolt hole, strictly controlling the spatial position and orientation of the flanges, and precisely aligning the center of the chord steel pipe are prerequisites for the individual manufacturing of main arch segments. Besides the requirement for positioning accuracy, the ability to achieve rapid positioning is also key to improving the manufacturing efficiency of the main arch.

[0004] Existing measurement technologies cannot simultaneously guarantee millimeter-level layout and positioning as well as real-time correction and adjustment. Traditional optical prism measurement cannot accurately locate the center of the pipe opening, and the efficiency of switching stations for instruments such as total stations and levels is low. The field of view of structured light-based 3D reconstruction technology for industrial manufacturing is small and cannot be extended to large-scale workpiece processing. Image-based 3D reconstruction technology is sensitive to ambient light intensity and has low robustness and efficiency. Although 3D laser scanning technology has high accuracy, its scanning efficiency and the processing efficiency of massive point clouds are low, making it difficult to meet the engineering requirements for real-time adjustments in steel structure processing.

[0005] Meanwhile, Chinese patent CN119188003A discloses a high-precision assembly and positioning method and device for steel pipe segments, including: obtaining the coordinates of the center of the port of all chord members of the assembly segment; determining the positional deviation of the chord members based on the coordinates of the center of the port; adjusting the port of the chord members so that the positioning error of the chord members meets the set requirements; welding cross braces, diagonal braces, and web members to initially form the current manufacturing segment; positioning the inner flange of the chord members of the current manufacturing segment; and fixing the flange according to the positioned inner flange of the chord members. However, the existing method uses optical prisms, which can be accelerated by measuring robots, with each prism measuring once every 3-5 seconds at the fastest, but it cannot achieve simultaneous measurement of multiple points and cannot provide real-time feedback. To address the above problems, we propose a multi-view real-time digital monitoring method and system for the assembly of large steel truss segments without pre-assembly. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a multi-view real-time digital monitoring method and system for assembling large steel truss segments without pre-assembly. This solves the problem that existing methods, when using optical prisms to position steel pipe segments during assembly, cannot achieve simultaneous multi-point measurement and cannot provide real-time feedback.

[0007] This invention is implemented as follows: a multi-view real-time digital monitoring method for the assembly of large steel truss segments without pre-assembly, the method comprising:

[0008] S10, Segment main tube unloading scan: The segment main tube unloading is scanned based on the industrial camera arranged in the segment main tube unloading area, and the local coordinate transformation of the centroids at both ends of the tube in the tube body target coordinate system is completed;

[0009] S20, Segment main pipe laying monitoring: A camera system is set up in the main pipe assembly yard and the industrial camera is calibrated to calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard.

[0010] S30, Segment main pipe assembly correction: Calculate the centroids at both ends of the main pipe, adjust the position and orientation of the main pipe and flange based on the calculation results, monitor the position and orientation error in real time, and correct the segment main pipe assembly based on the position and orientation error.

[0011] S40, Flange layout and fixing: Measure and calculate the world coordinates of the flange's marking points, adjust the flange's position based on the calculation results, and weld the adjusted flange.

[0012] Preferably, the segmental main tube unloading scanning method includes:

[0013] S101, Layout and calibration of the 4 industrial camera system in the unloading yard, based on the industrial cameras arranged along the unloading length of the segment main pipe to scan the unloading of the segment main pipe;

[0014] S102, Measure the world coordinates of the i-th main pipe body and pipe end marker point;

[0015] S103, obtain the world coordinates of the i-th main pipe body and the pipe end marker point, and calculate the world coordinates of the centroids at both ends of the main pipe;

[0016] S104, load the world coordinates of the centroids at both ends of the main pipe, and perform local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body.

[0017] Preferably, when arranging and calibrating the 4 industrial camera system in the unloading yard, the calibration of the industrial cameras includes intrinsic parameter matrix calibration and extrinsic parameter matrix calibration. The intrinsic parameter calibration adopts the Zhang Zhengyou calibration method; the extrinsic parameter matrix calibration adopts the normalized eight-point method. After the industrial cameras are set up, no less than 3 targets are randomly arranged in advance at different horizontal positions and different heights on the ground. The side length of the targets used for calibration is not less than 10cm. The world coordinates of the center points of all targets are measured and recorded in advance using a total station. Then, the pixel coordinates of the center points of all targets in the camera imaging plane are quickly and accurately searched using the YOLO algorithm or manual point-pointing. Then, the extrinsic parameter matrices of all industrial cameras are solved using the P3P or PnP algorithm. One of the industrial cameras is defined as camera zero. With the optical center of camera zero as the origin of the coordinate system, the rotation matrix R and translation matrix T between adjacent industrial cameras and camera zero are constructed to obtain the rotation and translation relationship between any adjacent cameras, as well as the absolute pose of the industrial cameras.

[0018] Preferably, when calculating the world coordinates of the centroids at both ends of the main pipe, the pixels in the imaging planes of the four industrial cameras are triangulated, and the world coordinates of the i-th main pipe body and the pipe end marker point are obtained through beam adjustment optimization of multiple views. Then, the spatial center coordinates of the steel pipe end are obtained according to the least squares fitting, and the world coordinates of the steel pipe end center are fitted with the spatial point of the end reflector sphere.

[0019] Preferably, when performing local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body, firstly, three targets on the outer wall of any i-th steel pipe are selected as reference points of the local coordinate system to establish the local coordinate system of the pipe body. Then, the world coordinates of the centers at both ends of the steel pipe are transformed to the local coordinate system of the pipe body.

[0020] Preferably, the segmental main pipe laying monitoring method includes:

[0021] S201, Camera system layout and calibration in assembly field 6: The camera system is laid out in the main assembly field and the industrial cameras are calibrated. The calibration of the industrial cameras includes the calibration of the intrinsic parameter matrix and the extrinsic parameter data.

[0022] S202, after the industrial camera is set up and calibrated, measure the i-th main tube target;

[0023] S203 uses inverse transformation to solve for the world coordinates of the centroids at both ends of the main pipe within the main pipe assembly field.

[0024] Preferably, the segment master group assembly correction method includes:

[0025] S301, Calculate the centroids at both ends of the main pipe;

[0026] S302 adjusts the position and orientation of the main pipe and flange based on the calculation results, and monitors the position and orientation error in real time to determine whether the position and orientation error meets the requirements.

[0027] S303, if the positional error meets the requirements, spot welding is used to initially fix the main section; if the positional error does not meet the requirements, the main section assembly is corrected based on the positional error.

[0028] S304, finely adjusted web members and cross braces, and welded into shape.

[0029] Preferably, the flange layout and fixing method includes:

[0030] S401 uses a multi-view system composed of calibrated and fixed industrial cameras to measure the world coordinates of the marking points of the bolt joint flange, solve the flange pose, and output the solution results.

[0031] S402, adjust the flange position based on the calculation results, and spot weld the flange to fix it;

[0032] S403, formally welded flange, completed the assembly and manufacturing of large steel truss segments.

[0033] On the other hand, the present invention also provides a multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly. The multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly includes:

[0034] The unloading scanning module scans the unloading of the segment main pipe based on an industrial camera arranged in the unloading yard of the segment main pipe, and completes the local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body;

[0035] The line laying monitoring module is used to deploy the camera system in the main pipe assembly yard and calibrate the industrial cameras, and calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard.

[0036] The assembly and correction module is used to calculate the centroids at both ends of the main pipe, adjust the position and orientation of the main pipe and flange based on the calculation results, monitor the position and orientation error in real time, and correct the assembly and orientation of the segment main pipe based on the position and orientation error.

[0037] The layout and fixing module is used to measure and calculate the world coordinates of the flange's marking points, adjust the flange's position and orientation based on the calculation results, and weld the adjusted flange.

[0038] Compared with the prior art, the embodiments of this application have the following main advantages:

[0039] This invention provides a multi-view real-time digital monitoring method for assembling large steel truss segments without pre-assembly. It employs multiple visual measurements to avoid line-of-sight obstruction caused by unidirectional measurements and avoids the time waste caused by repeatedly switching measurement stations. It can accurately control the centroid of the steel pipe ends and avoid the uncertain errors caused by measuring a single waistline of a circular pipe. Furthermore, it adopts a priori measurement and recording method, measuring only three marker points on the main pipe body during the formal assembly stage, and using the coordinates of the marker points to calculate the centroid coordinates of the two ends of the main pipe, which greatly improves the efficiency of measurement and layout.

[0040] This invention employs a pre-assembly-free, single-segment independent manufacturing mode and simultaneously scans and cuts the main pipe of each segment, completely eliminating the dependence on narrow spaces required by the traditional "n+1" physical pre-assembly process. Traditional methods require hundreds of meters of continuous space for placing multiple segments side-by-side, while this invention only requires a single-segment manufacturing area, significantly reducing land use. Especially in complex terrains such as steep mountainous areas, canyon bottoms, and riverbeds, the size of the steel operating platform is reduced exponentially, eliminating the cost and procedures of large-scale site leveling and steel platform erection. This solves the problems of "inability to implement" or "excessive cost" caused by site limitations in traditional processes, significantly improving the adaptability of manufacturing technology to complex terrains.

[0041] Compared to existing point cloud direct measurement technologies (structured light scanning, laser SLAM or VSLAM, multi-sensor fusion scanning, etc.), current technologies only employ scanning modeling after the steel truss segment positioning and fabrication are completed, followed by measurement within the point cloud. Point cloud processing and point measurement consume significant time and can only detect manufacturing accuracy, not correct deviations. This invention, however, adopts a priori approach, pre-establishing and processing the point cloud before the steel pipe assembly stage, without impacting the assembly schedule. The relative relationship (world coordinates → local coordinates) between the centroid of the steel pipe end and the marked points is established during the steel pipe cutting stage. During the steel pipe assembly and layout stage, this relative relationship (world coordinates → local coordinates) is directly invoked. Only a few fixed marked points on the pipe body need to be measured to indirectly calculate the steel pipe's axial orientation and end centroid coordinates (local coordinates → world coordinates). Furthermore, this can be completed instantly through the direct measurement of only three target points, thus greatly improving the efficiency of measurement and layout.

[0042] Compared with existing total station surveying techniques, this invention enables multi-point simultaneous measurement, eliminating the need for repeated station transfers due to obstructions or angle limitations, and avoiding error accumulation caused by station transfers. Furthermore, real-time target point tracking significantly reduces the switching time between individual measurement points. Compared to existing 3D reconstruction surveying techniques, this invention uses image binarization processing, retaining only image information of reflective or bright marker points, reducing background interference, and calculating only the marker points, greatly improving the calculation efficiency of target marker points. Moreover, edge feature extraction exhibits higher robustness than RGB images with backgrounds, resulting in higher measurement stability. Employing multi-directional and multi-view image capture avoids obstruction problems in single-direction shooting, enabling simultaneous measurement of both ends of the steel pipe, saving time spent switching perspectives, and achieving real-time feedback of the steel pipe's axis. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the implementation process of the multi-view real-time digital monitoring method for the assembly of large steel truss segments without pre-assembly provided by the present invention.

[0044] Figure 2 A schematic diagram of the section main tube feeding and scanning in an embodiment of the present invention is shown.

[0045] Figure 3 The image shows a feature point image of the section main pipe being scanned by an industrial camera.

[0046] Figure 4 This diagram illustrates the measurement of the main chord length during the assembly of large steel truss segments.

[0047] Figure 5 This diagram illustrates the measurement of the chord main pipe width during the assembly of large steel truss segments.

[0048] Figure 6 A schematic diagram of the main flange layout measurement is shown in an embodiment of the present invention.

[0049] Figure 7 A diagram showing the relationship between the main flange hole positions and the reflective ball fixing device in an embodiment of the present invention is provided.

[0050] Figure 8 A schematic diagram of a multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly is shown.

[0051] In the diagram: 1. Steel pipe; 2. Target; 3. Reflective ball holder; 3-1. Reflective ball; 3-2. Screw; 3-3. Magnetic base; 4. Industrial camera; 4-1. Imaging plane; 4-2. Imaging point; 5. Flange; 6. Stiffening plate; 100. Material unloading scanning module; 200. Line laying monitoring module; 300. Assembly and correction module; 400. Line laying fixing module. Detailed Implementation

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0053] Existing methods for assembling and positioning steel pipe segments using optical prisms cannot achieve simultaneous multi-point measurements and cannot provide real-time feedback. To address these issues, we propose a multi-view real-time digital monitoring method and system for assembling large steel truss segments without pre-assembly. In short, the method involves first scanning the main pipe segment before it is cut, completing the local coordinate transformation of the centroids at both ends of the main pipe within the coordinate system of the target 2 on the pipe body. Then, the main pipe segment is monitored and its assembly is corrected. Finally, the world coordinates of the marking points on the flange 5 are measured and calculated. Based on the calculation results, the position and orientation of the flange 5 are adjusted, and the adjusted flange 5 is welded, completing the layout and fixing of the flange 5. This invention provides a multi-view real-time digital monitoring method for assembling large steel truss segments without pre-assembly. It uses multiple visual measurements to avoid line-of-sight obstruction caused by unidirectional measurement and avoids the time waste caused by repeatedly switching measurement stations. It can accurately control the centroid of the end of the steel pipe 1 and avoid the uncertain error caused by measuring a single waistline of the circular pipe. Furthermore, it adopts a priori measurement and recording method, measuring only 3 marker points on the main pipe body during the formal assembly stage, and using the coordinates of the marker points to calculate the coordinates of the centroids at both ends of the main pipe, which greatly improves the efficiency of measurement and layout.

[0054] This invention provides a multi-view real-time digital monitoring method for assembling large steel truss segments without pre-assembly. Figure 1 A schematic diagram illustrating the implementation process of a multi-view real-time digital monitoring method for the assembly of large steel truss segments without pre-assembly is shown. The method specifically includes:

[0055] S10, Segment main tube unloading scan: The industrial camera 4 arranged in the segment main tube unloading area scans the segment main tube unloading and completes the local coordinate transformation of the centroids at both ends of the main tube in the coordinate system of the tube body target 2.

[0056] S20, Segment main pipe laying monitoring: A camera system is set up in the main pipe assembly yard and the industrial camera 4 is calibrated to calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard.

[0057] S30, Segment main pipe assembly correction: Calculate the centroids at both ends of the main pipe, adjust the 5-position pose of the main pipe and flange based on the calculation results, monitor the pose error in real time, and correct the segment main pipe assembly based on the pose error.

[0058] S40, Flange layout and fixing: Measure and calculate the world coordinates of the marking points of flange 5, adjust the position and orientation of flange 5 based on the calculation results, and weld the adjusted flange 5.

[0059] This invention provides a multi-view real-time digital monitoring method for assembling large steel truss segments without pre-assembly. It uses multiple visual measurements to avoid line-of-sight obstruction caused by unidirectional measurement and avoids the time waste caused by repeatedly switching measurement stations. It can accurately control the centroid of the end of the steel pipe 1 and avoid the uncertain error caused by measuring a single waistline of the circular pipe. Furthermore, it adopts a priori measurement and recording method, measuring only 3 marker points on the main pipe body during the formal assembly stage, and using the coordinates of the marker points to calculate the coordinates of the centroids at both ends of the main pipe, which greatly improves the efficiency of measurement and layout.

[0060] In this embodiment of the invention, the segmental main tube blanking scanning method includes:

[0061] S101, Layout and calibration of 4 industrial cameras in the unloading yard, based on the industrial cameras 4 arranged along the unloading length of the segment main pipe to scan the unloading of the segment main pipe;

[0062] It should be noted that when the industrial camera system is set up and calibrated in the material unloading area, the calibration of the industrial camera 4 includes the calibration of the intrinsic parameter matrix and the calibration of the extrinsic parameter matrix. The intrinsic parameter calibration adopts the Zhang Zhengyou calibration method; the extrinsic parameter matrix calibration adopts the normalized eight-point method. After the industrial camera 4 is set up, no less than 3 targets 2 are randomly arranged in advance at different horizontal positions and different heights on the ground. In order to ensure the calibration accuracy, the side length of the target 2 used for calibration is not less than 10cm. The world coordinates of the center points of all targets 2 are measured and recorded in advance using a total station.

[0063] Figure 2 This diagram illustrates a segmental main pipe feeding and scanning process in an embodiment of the present invention. Figure 2 As can be seen, during the scanning of the main section, multiple sets of reflective ball holders 3 are installed on the inner wall of the steel pipe 1. Each reflective ball holder 3 includes a reflective ball 3-1, a screw 3-2, and a magnetic base 3-3. The magnetic base 3-3 is fixedly installed on the inner wall of the steel pipe 1. The screw 3-2 is fixedly installed on the magnetic base 3-3 using a plug-in method. The reflective ball 3-1 is detachably connected to the screw 3-2 via threads. The length of the screw 3-2 is fixed at 5-10cm. The reflective ball 3-1 is tightened to its maximum to avoid errors in center fitting caused by ball center deviation. The magnetic base 3-3 is attached to the end of the steel pipe 1 or the edge of the flange 5, with the edge of the base aligned with the edge of the attached object to ensure accurate line laying. Figure 2 The positions of target 2 and industrial camera 4 are also shown. The industrial camera 4 is circumferentially located outside the steel pipe 1. When the industrial camera 4 is scanning, it generates an imaging plane 4-1, and multiple imaging points 4-2 are formed within the imaging plane 4-1. Above the steel pipe 1 unloading and processing area, four industrial cameras 4 are evenly arranged, forming a certain angle with the vertical line. The area enclosed by the line connecting the four industrial cameras 4 should be larger than the horizontal projection area of ​​the steel pipe 1, ensuring that any reflective sphere 3-1 or target 2 can be covered by the images of at least two industrial cameras 4 at the same time. Then, the YOLO algorithm or manual point-splitting is used to quickly and accurately search for the pixel coordinates of the center points of all targets 2 in the camera imaging plane 4-1. Then, the P3P or PnP algorithm is used to solve for the extrinsic parameter matrix of all industrial cameras 4, and one of the industrial cameras 4 is defined as camera zero. With the optical center of camera zero as the origin of the coordinate system, the rotation matrix R and translation matrix T between adjacent industrial cameras 4 and camera zero are constructed. This process is repeated to obtain the rotation and translation relationship between any adjacent cameras, as well as the absolute pose of the industrial cameras 4.

[0064] S102, Measure the world coordinates of the i-th main pipe body and pipe end marker point;

[0065] S103, obtain the world coordinates of the i-th main pipe body and the pipe end marker point, and calculate the world coordinates of the centroids at both ends of the main pipe;

[0066] In this embodiment of the invention, when calculating the world coordinates of the centroids at both ends of the main pipe, the pixels in the imaging plane 4-1 of the four industrial cameras 4 are triangulated, and the world coordinates of the i-th main pipe body and end marker point are obtained through bundle adjustment (BA) of multiple views. Then, the spatial center coordinates of the end of the steel pipe 1 are obtained according to least squares fitting, and the world coordinates of the end center of the steel pipe 1 are fitted with the spatial point of the center of the end reflector 3-1. Here, the spatial center of the end of the steel pipe 1 and the circle formed by the end-fixed reflector 3-1 are concentric circles. Therefore, the world coordinates of the end center of the steel pipe 1 can be fitted with the spatial point of the center of the end reflector 3-1. The least squares expression is as follows:

[0067]

[0068] Among them, XO i,j ,YO i,j ZO i,j Let be the world coordinates of the center of the j-th end opening of the i-th steel pipe segment; Let R represent the set of X, Y, Z coordinates of the center point of the reflective sphere 3-1 at the j-th end of the i-th steel pipe segment in the local coordinate system. i,j The radius of the j-th opening of the i-th arch rib segment is the radius of the steel pipe 1 after deducting the height of the reflective ball fixing device 3.

[0069] S104, load the world coordinates of the centroids at both ends of the main pipe, and perform local coordinate transformation of the centroids at both ends of the main pipe in the target 2 coordinate system of the pipe body.

[0070] In this embodiment of the invention, when performing local coordinate transformation of the centroids at both ends of the main pipe in the coordinate system of the target 2 on the pipe body, firstly, three targets 2 on the outer wall of any i-th steel pipe 1 are selected as reference points of the local coordinate system to establish the local coordinate system of the pipe body. As in formula (2-4) and Figure 2 As shown. The standard vector of the local coordinate system for the i-th segment of steel pipe 1, where norm represents normalization:

[0071]

[0072]

[0073] in, Let x, y, and z represent the world coordinates of the center point of the j-th target 2 on the tube, respectively. A vector is obtained by the cross product of two vectors.

[0074] Then, the world coordinates of the centers at both ends of steel pipe 1 are transformed to the local coordinate system of the pipe body. The transformation formula is expressed as:

[0075]

[0076] in,

[0077] Where lowercase x, y, and z represent world coordinates, uppercase X, Y, and Z represent local coordinates, and T represents world coordinates. i Let represent the target coordinate system transformation matrix for the i-th steel pipe segment 1.

[0078] It should be noted that the targets 2 on the outer wall of the tube should be generally facing upwards to avoid image obstruction. The number of targets 2 on each tube should not be less than three, and preferably four, to avoid information loss due to obstruction of any target 2, and to ensure robustness in recording the relative spatial relationship between the ports of the steel pipe 1. Figure 3 The image shows feature point images of the industrial camera 4 scanning the section pipe before unloading. Steps S101-S104 are repeated for each pipe segment unloaded from the steel pipe 1, and then the reflective ball retainer 3 is removed, leaving the pipe body target 2.

[0079] Meanwhile, when scanning the section main pipe, multi-view vision can be used to measure the world coordinates of key marker points or target 2. Alternatively, SFM, SLAM technology or other point cloud generation methods can be used to scan the spatial relative relationship between key marker points or target 2 and steel pipe 1 or other types of steel components in advance, as long as the world coordinates can be calculated from the local coordinates.

[0080] This invention employs a pre-assembly-free, single-segment independent manufacturing mode and simultaneously scans and cuts the main pipe of each segment, completely eliminating the dependence on narrow spaces required by the traditional "n+1" physical pre-assembly process. Traditional methods require hundreds of meters of continuous space for placing multiple segments side-by-side, while this invention only requires a single-segment manufacturing area, significantly reducing land use. Especially in complex terrains such as steep mountainous areas, canyon bottoms, and riverbeds, the size of the steel operating platform is reduced exponentially, eliminating the cost and procedures of large-scale site leveling and steel platform erection. This solves the problems of "inability to implement" or "excessive cost" caused by site limitations in traditional processes, significantly improving the adaptability of manufacturing technology to complex terrains.

[0081] Meanwhile, compared with existing point cloud direct measurement technologies (structured light scanning, laser SLAM or VSLAM, multi-sensor fusion scanning, etc.), existing technologies only use scanning modeling after the steel truss segment positioning and manufacturing are completed, and then measurement is performed in the point cloud. Point cloud processing and point measurement consume a lot of time, and can only detect its manufacturing accuracy, but cannot correct deviations. The embodiment of this invention adopts a priori thinking, pre-establishing and processing the point cloud before the steel pipe 1 assembly stage, without occupying the steel pipe 1 assembly period. The relative relationship (world coordinates → local coordinates) between the centroid of the steel pipe 1 port and the marker point is established during the steel pipe 1 cutting stage. During the steel pipe 1 assembly and layout stage, this relative relationship (world coordinates → local coordinates) is directly called. Only a few fixed marker points on the pipe body need to be measured to indirectly calculate the axis attitude and port centroid coordinates (local coordinates → world coordinates) of steel pipe 1. Moreover, it can be completed instantly by directly measuring only 3 target points, thus greatly improving the efficiency of measurement and layout.

[0082] It should be noted that before entering the segment main pipe laying monitoring stage, the industrial camera 4 setup and internal / external parameter matrix calibration in step S101 should be repeated first. In the segment main pipe laying monitoring, there should be no fewer than 6 industrial cameras 4 in the assembly area to avoid line-of-sight obstruction and excessive distance leading to reduced imaging and measurement quality, while simultaneously meeting the requirements for accuracy, stability, and efficiency. For example... Figure 4 A schematic diagram showing the measurement of the length of the main chord member during the assembly of large steel truss segments is provided. Figure 5 This invention illustrates a schematic diagram of the measurement and layout of the main chord section during the assembly of large steel truss segments. In this embodiment, compared to existing total station measurement techniques, this invention enables simultaneous multi-point measurement, eliminating the need for repeated station transfers due to obstructions or angle limitations, and avoiding error accumulation caused by station transfers. Furthermore, real-time target point tracking significantly reduces the switching time between individual measurement points. Compared to existing 3D reconstruction measurement techniques, this invention uses image binarization processing, retaining only the image information of reflective or bright marker points, reducing background interference, and calculating only the marker points, greatly improving the calculation efficiency of target marker points. Moreover, the robustness of edge feature extraction is higher than that of RGB images with a background, resulting in higher measurement stability. Using multi-directional, multi-view image capture avoids obstruction problems in single-direction shooting, enabling simultaneous measurement of both ends of the steel pipe 1, saving time in changing perspectives, and achieving real-time feedback of the steel pipe 1's axis.

[0083] In this embodiment of the invention, the segmental main pipe laying monitoring method includes:

[0084] S201, Camera system setup and calibration in assembly field 6: The camera system is set up in the main assembly field and the industrial camera 4 is calibrated. The calibration of the industrial camera 4 includes calibration of the intrinsic parameter matrix and extrinsic parameter data. The calibration method is the same as in step S101.

[0085] S202, After the industrial camera 4 is set up and calibrated, the i-th main tube target 2 is measured, that is, the three-dimensional reconstruction of the target 2 pixels in steps S103-S104 is repeated.

[0086] S203 uses inverse transformation to solve for the world coordinates of the centroids at both ends of the main pipe within the main pipe assembly field.

[0087] In this embodiment of the invention, when using inverse transformation to calculate the world coordinates of all tube targets 2, the calculation formula is expressed as:

[0088]

[0089] Where lowercase x, y, z represent world coordinates, and uppercase X, Y, Z represent local coordinates, and is the inverse transformation matrix, which is obtained by formula (6).

[0090] In this embodiment of the invention, the segment master group splicing correction method includes:

[0091] S301, Calculate the centroids at both ends of the main pipe;

[0092] S302, adjusts the 5 positions of the main pipe and flange based on the calculation results, and monitors the position error in real time to determine whether the position error meets the requirements;

[0093] S303, if the positional error meets the requirements, spot welding is used to initially fix the main section; if the positional error does not meet the requirements, the main section assembly is corrected based on the positional error.

[0094] S304, finely adjusted web members and cross braces, and welded into shape.

[0095] It should be noted that when calculating the centroids at both ends of the main pipe, the local coordinates of the two ends of the center are substituted into formula (4) to calculate the world coordinates of the two ends of the center of the steel pipe 1. Thus, the pose of the axis of the steel pipe 1 can be obtained. By comparing with the designed pose, the pose error of the current placement of the steel pipe 1 is obtained. The pose error is calculated by formula (8).

[0096]

[0097] Where Δ i, j represents the deviation of the center of the j-th pipe opening on the i-th steel pipe segment 1; These are the current coordinates of the j-th nozzle on the i-th segment; These are the design coordinates of the j-th nozzle on the i-th segment.

[0098] In steps S302-S304, the positional deviation of each steel pipe 1 is calculated according to formula (5), and the placement position of the steel pipe 1 is adjusted until the laying accuracy requirement is met. Finally, the welding and shaping of the steel truss segment is completed.

[0099] In this embodiment of the invention, the flange layout and fixing method includes:

[0100] S401 uses a multi-view system consisting of calibrated and fixed industrial cameras 4 to measure the world coordinates of the marking points of the bolt joint flange 5, solve the pose of the flange 5, and output the solution results.

[0101] S402, adjust the position of flange 5 based on the solution results, and spot weld flange 5 to fix it;

[0102] S403, formally welded flange 5, completed the assembly and manufacturing of large steel truss segments.

[0103] It should be noted that the manufacturing of the steel truss segment enters the flange 5 layout and fixing stage, which is the positioning and welding of the flange at the end of the steel pipe 1. Figure 6 A schematic diagram of the line setting and measurement of the main flange 5 in an embodiment of the present invention is shown, while Figure 7 The diagram illustrates the planar relationship between the bore positions of the main flange 5 and the reflective ball holder 3 in an embodiment of the present invention. In step S401, a multi-view system composed of calibrated and fixed industrial cameras 4 is used to measure the world coordinates of the marker points of the bolt joint flange 5, and the pose of the flange 5 is solved. To facilitate the characterization of the pose of the flange bore positions, the reflective ball holder 3 is used for both 6-hole and 8-hole flanges. Figure 7 The fixing method is as follows: multiple sets of reflective ball fixing devices 3 are fixed on the flange 5. The flange 5 is fixedly connected to the end of the steel pipe 1 through multiple sets of stiffening plates 6, so that the angle between the spatial auxiliary connection line of the reflective ball fixing device 3 and the hole connection line is more regular and more convenient to represent the overall position of the bolt hole.

[0104] On the other hand, embodiments of the present invention also provide a multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly. Figure 8 A schematic diagram of a multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly is shown. This system specifically includes:

[0105] The unloading scanning module 100 scans the unloading of the segment main pipe based on the industrial camera 4 arranged in the unloading yard of the segment main pipe, and completes the local coordinate transformation of the centroids at both ends of the main pipe in the coordinate system of the pipe target 2.

[0106] The cable laying monitoring module 200 is used to deploy the camera system in the main pipe assembly yard and calibrate the industrial camera 4, and calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard.

[0107] The assembly and correction module 300 is used to calculate the centroids at both ends of the main pipe, adjust the 5-position pose of the main pipe and flange based on the calculation results, monitor the pose error in real time, and correct the assembly of the segment main pipe based on the pose error.

[0108] The layout and fixing module 400 is used to measure and calculate the world coordinates of the marking points of flange 5, adjust the position and orientation of flange 5 based on the calculation results, and weld the adjusted flange 5.

[0109] In this embodiment, the material cutting scanning module 100, the line laying monitoring module 200, the assembly correction module 300, and the line laying fixing module 400 can be connected via a local area network or DTU communication. Furthermore, the steps of the pre-assembly-free large steel truss segment assembly multi-view real-time digital monitoring system provided in this embodiment correspond to the steps of the pre-assembly-free large steel truss segment assembly multi-view real-time digital monitoring method in the above embodiments, and will not be repeated here.

[0110] In summary, this invention provides a multi-view real-time digital monitoring method and system for assembling large steel truss segments without pre-assembly. The method employs multiple visual measurements to avoid line-of-sight obstruction in unidirectional measurements and avoids the time wasted by repeatedly switching measurement stations. It can accurately control the centroid of the ends of steel pipe 1, avoiding uncertain errors caused by measuring a single waistline of a circular pipe. Furthermore, it uses a priori measurement and recording method, measuring only three marker points on the main pipe during the formal assembly stage, and using the coordinates of these marker points to calculate the centroid coordinates of both ends of the main pipe, greatly improving the efficiency of measurement and layout.

[0111] This invention employs a pre-assembly-free, single-segment independent manufacturing mode and simultaneously scans and cuts the main pipe of each segment, completely eliminating the dependence on narrow spaces required by the traditional "n+1" physical pre-assembly process. Traditional methods require hundreds of meters of continuous space for placing multiple segments side-by-side, while this invention only requires a single-segment manufacturing area, significantly reducing land use. Especially in complex terrains such as steep mountainous areas, canyon bottoms, and riverbeds, the size of the steel operating platform is reduced exponentially, eliminating the cost and procedures of large-scale site leveling and steel platform erection. This solves the problems of "inability to implement" or "excessive cost" caused by site limitations in traditional processes, significantly improving the adaptability of manufacturing technology to complex terrains.

[0112] Compared to existing point cloud direct measurement technologies (structured light scanning, laser SLAM or VSLAM, multi-sensor fusion scanning, etc.), existing technologies only employ scanning modeling after the steel truss segment positioning and fabrication are completed, followed by measurement within the point cloud. Point cloud processing and point measurement consume significant time and can only detect manufacturing accuracy, not correct deviations. This invention, however, adopts a priori approach, pre-establishing and processing the point cloud before the steel pipe assembly stage, without impacting the steel pipe assembly schedule. The relative relationship (world coordinates → local coordinates) between the centroid of the steel pipe's port and the marker points is established during the steel pipe's cutting stage. During the steel pipe assembly and layout stage, this relative relationship (world coordinates → local coordinates) is directly invoked. Only a few fixed marker points on the pipe body need to be measured to indirectly calculate the axial orientation and port centroid coordinates (local coordinates → world coordinates) of the steel pipe. Furthermore, this can be completed instantly through the direct measurement of only three target points, thus greatly improving the efficiency of measurement and layout.

[0113] Compared with existing total station surveying techniques, this invention enables multi-point simultaneous measurement, eliminating the need for repeated station transfers due to obstructions or angle limitations, and avoiding error accumulation caused by station transfers. Furthermore, real-time target point tracking significantly reduces the switching time between individual measurement points. Compared to existing 3D reconstruction surveying techniques, this invention uses image binarization processing, retaining only image information of reflective or bright marker points, reducing background interference, and calculating only the marker points, greatly improving the calculation efficiency of target marker points. Moreover, edge feature extraction exhibits higher robustness than RGB images with backgrounds, resulting in higher measurement stability. Employing multi-directional and multi-view image capture avoids obstruction problems in single-direction shooting, enabling simultaneous measurement of both ends of the steel pipe 1, saving time spent switching perspectives, and achieving real-time feedback of the steel pipe 1's axis.

[0114] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A multi-view real-time digital monitoring method for the assembly of large steel truss segments without pre-assembly, characterized in that, The method includes: S10, Segment main tube unloading scan: The segment main tube unloading is scanned based on the industrial camera arranged in the segment main tube unloading area, and the local coordinate transformation of the centroids at both ends of the tube in the tube body target coordinate system is completed; S20, Segment main pipe laying monitoring: A camera system is set up in the main pipe assembly yard and the industrial camera is calibrated to calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard. S30, Segment main pipe assembly correction: Calculate the centroids at both ends of the main pipe, adjust the position and orientation of the main pipe and flange based on the calculation results, monitor the position and orientation error in real time, and correct the segment main pipe assembly based on the position and orientation error. S40, Flange layout and fixing: Measure and calculate the world coordinates of the flange's marking points, adjust the flange's position based on the calculation results, and weld the adjusted flange. The section main tube unloading scan includes: S101, Layout and calibration of the 4 industrial camera system in the unloading yard, based on the industrial cameras arranged along the unloading length of the segment main pipe to scan the unloading of the segment main pipe; S102, Measure the world coordinates of the i-th main pipe body and pipe end marker point; S103, obtain the world coordinates of the i-th main pipe body and the pipe end marker point, and calculate the world coordinates of the centroids at both ends of the main pipe; S104, Load the world coordinates of the centroids at both ends of the main pipe, and perform local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body; The segment main pipe laying monitoring includes: S201, Camera system layout and calibration in assembly field 6: The camera system is laid out in the main assembly field and the industrial cameras are calibrated. The calibration of the industrial cameras includes the calibration of the intrinsic parameter matrix and the extrinsic parameter data. S202, after the industrial camera is set up and calibrated, measure the i-th main tube target; S203 uses inverse transformation to calculate the world coordinates of the centroids at both ends of the main pipe within the main pipe assembly field.

2. The method for multi-view real-time digital monitoring of large steel truss segment assembly without pre-assembly as described in claim 1, characterized in that: When arranging and calibrating the four industrial camera systems in the material unloading area, the calibration of the industrial cameras includes intrinsic parameter matrix calibration and extrinsic parameter matrix calibration. The intrinsic parameter calibration adopts the Zhang Zhengyou calibration method; the extrinsic parameter matrix calibration adopts the normalized eight-point method. After the industrial cameras are set up, no less than three targets are randomly arranged at different horizontal positions and different heights on the ground. The side length of the targets used for calibration is not less than 10cm. The world coordinates of the center points of all targets are measured and recorded in advance using a total station. Then, the pixel coordinates of the center points of all targets in the camera imaging plane are quickly and accurately searched using the YOLO algorithm or manual point-pointing. Then, the extrinsic parameter matrices of all industrial cameras are obtained by using the P3P or PnP algorithm. One of the industrial cameras is defined as camera zero. With the optical center of camera zero as the origin of the coordinate system, the rotation matrix R and translation matrix T between adjacent industrial cameras and camera zero are constructed to obtain the rotation and translation relationship between any adjacent cameras, as well as the absolute pose of the industrial cameras.

3. The method for multi-view real-time digital monitoring of large steel truss segment assembly without pre-assembly as described in claim 2, characterized in that: When calculating the world coordinates of the centroids at both ends of the main pipe, the pixels in the imaging planes of the four industrial cameras are triangulated, and the world coordinates of the i-th main pipe body and end marker point are obtained through beam adjustment optimization of multiple views. Then, the spatial center coordinates of the steel pipe end are obtained according to the least squares fitting, and the world coordinates of the steel pipe end center are fitted with the spatial point of the end reflector sphere.

4. The method for multi-view real-time digital monitoring of large steel truss segment assembly without pre-assembly as described in claim 3, characterized in that: When performing local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body, firstly, select three targets on the outer wall of any i-th steel pipe as reference points of the local coordinate system, and establish the pipe body local coordinate system Coor( , , Then, the world coordinates of the centers at both ends of the steel pipe are transformed to the local coordinate system of the pipe body.

5. The method for multi-view real-time digital monitoring of large steel truss segment assembly without pre-assembly as described in claim 4, characterized in that: The segment master group's error correction includes: S301, Calculate the centroids at both ends of the main pipe; S302 adjusts the position and orientation of the main pipe and flange based on the calculation results, and monitors the position and orientation error in real time to determine whether the position and orientation error meets the requirements. S303, if the positional error meets the requirements, spot welding is used to initially fix the main section; if the positional error does not meet the requirements, the main section assembly is corrected based on the positional error. S304, finely adjusted web members and cross braces, and welded into shape.

6. The method for multi-view real-time digital monitoring of large steel truss segment assembly without pre-assembly as described in claim 5, characterized in that: The flange layout and fixing includes: S401 uses a multi-view system composed of calibrated and fixed industrial cameras to measure the world coordinates of the marking points of the bolt joint flange, solve the flange pose, and output the solution results. S402, adjust the flange position based on the calculation results, and spot weld the flange to fix it; S403, formally welded flange, completed the assembly and manufacturing of large steel truss segments.

7. A multi-view real-time digital monitoring system for the assembly of large steel truss segments without pre-assembly, used to implement the multi-view real-time digital monitoring method for the assembly of large steel truss segments without pre-assembly as described in any one of claims 1-6, characterized in that: The pre-assembly-free large steel truss segment assembly multi-view real-time digital monitoring system includes: The unloading scanning module scans the unloading of the segment main pipe based on an industrial camera arranged in the unloading yard of the segment main pipe, and completes the local coordinate transformation of the centroids at both ends of the main pipe in the target coordinate system of the pipe body; The line laying monitoring module is used to deploy the camera system in the main pipe assembly yard and calibrate the industrial cameras, and calculate the world coordinates of the centroids at both ends of the main pipe in the main pipe assembly yard. The assembly and correction module is used to calculate the centroids at both ends of the main pipe, adjust the position and orientation of the main pipe and flange based on the calculation results, monitor the position and orientation error in real time, and correct the assembly and orientation of the segment main pipe based on the position and orientation error. The layout and fixing module is used to measure and calculate the world coordinates of the flange's marking points, adjust the flange's position and orientation based on the calculation results, and weld the adjusted flange.

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