BIM rapid positioning system and method for reserved steel bars in subway station construction

Abstract

The invention relates to a BIM (Building Information Modeling) quick positioning system and method for reserved steel bars in subway station construction, and belongs to the technical field of computer-aided building design under electrical digital data processing. According to the system, an AR module carries out data interaction with a three-dimensional BIM model building module and a detection module, the three-dimensional BIM model building module calibrates a reinforcing steel bar binding position and carries out data interaction with a laser projection module, laser is controlled to precisely project the inclined direction and the end face center of a reserved reinforcing steel bar, and the positioning precision and the positioning efficiency are improved; and meanwhile, the AR module generates detection guidance, calculates the chiseling range of the mistakenly-buried reserved steel bars, controls AR eyes to synchronously display the detection guidance and the chiseling range, and corrects the parameters of the reserved steel bars of the three-dimensional BIM model building module. The problems of blindness, poor positioning precision, overlarge chiseling range, no consideration of steel bar displacement and incapability of accurately identifying the burial depth in manual chiseling of the mistakenly-buried steel bar in the prior art are solved, the structural damage caused by chiseling is reduced, and the construction efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of computer-aided architectural design technology under electronic digital data processing, and in particular to a BIM rapid positioning system and method for reserved steel bars in subway station construction. Background Technology

[0002] In the construction of subway station side walls, middle slabs and other structures, the reserved steel bars are key components for connecting subsequent processes. A portion of them needs to be reserved on the outside of the concrete. However, after each pour, some of the reserved steel bars on the outside of the concrete are always mistakenly covered by the concrete. The accurate positioning and excavation of the covered reserved steel bars directly affect the efficiency and quality of subsequent waterproof membrane laying and secondary structure construction.

[0003] Currently, the main method for locating covered pre-reserved steel bars is manual chiseling, which has significant drawbacks: After the concrete is poured, workers rely on construction experience or design drawings to anchor the bars and blindly chisel them with tools such as small hammers and electric picks to find the covered pre-reserved steel bars. This method relies entirely on manual experience, has poor positioning accuracy, takes more than 30 minutes per row of splice bars on average, and has an excessively large chiseling range (usually 100-150mm in diameter), which can easily damage the concrete structure and the steel bar protective layer.

[0004] Meanwhile, the actual deviations during construction were not considered: the lateral pressure and vibration impact during concrete pouring can cause the steel bars to shift by 5-20mm; errors in formwork installation and interference from embedded parts can also cause the theoretical coordinates to deviate from the actual positions; directly chiseling according to the coordinates on the drawings can easily result in "hollowing out" or "mis-chiseling", with frequent omissions and mis-chiseling, requiring repeated verification and correction, which delays the waterproof membrane laying process by 1-2 days and reduces construction efficiency; moreover, the design drawings only indicate the position of the steel bars and cannot reflect the actual thickness (depth) of the concrete cover, which can easily cause structural damage due to excessive chiseling. Summary of the Invention

[0005] The purpose of this invention is to provide a BIM-based rapid positioning system and method for pre-embedded rebar in subway station construction. This system integrates an AR module with a 3D BIM model building module and a detection module. The 3D BIM model building module accurately marks the rebar binding position and interacts with a laser projection module, controlling the laser to precisely project the tilt direction and end-face center of the pre-embedded rebar, improving the positioning accuracy and efficiency of rebar binding. Simultaneously, the AR module generates detection guidance, calculates the chiseling range for mistakenly embedded rebar, and controls the AR eye to synchronously display the detection guidance and chiseling range, while also correcting the rebar parameters in the 3D BIM model building module. This solves the problems of blindness, poor positioning accuracy, excessive chiseling range, failure to consider rebar displacement, and inaccurate identification of embedment depth leading to excessive chiseling in existing technologies, reducing structural damage caused by chiseling and improving construction efficiency.

[0006] The specific plan is as follows:

[0007] The BIM rapid positioning system for reserved steel bars in subway station construction includes a 3D BIM model building module, a laser projection module, a detection module, and an AR module.

[0008] The 3D BIM model building module builds a 3D BIM model based on the subway station design drawings, assigns a unique identifier to each reserved steel bar and enters the steel bar parameters;

[0009] The laser projection module controls the laser to position the tilt direction and end face center of the reserved steel bars according to the reserved steel bar parameters in the 3D BIM model, and calibrates the tilt direction and end face center.

[0010] The detection module is used to control the start and stop of the electromagnetic detection equipment for the reserved steel bars and to transmit data.

[0011] The AR module interacts with the 3D BIM model construction module and the detection module to generate detection guidelines, calculate the chiseling range of the buried reserved steel bars, control the AR eyes to synchronously display the detection guidelines and chiseling range, and correct the reserved steel bar parameters of the 3D BIM model construction module.

[0012] Furthermore, the unique code includes region-axis-serial number, and the rebar parameters include the diameter, length, shape, and three-dimensional coordinates of the center point of the rebar end face.

[0013] Furthermore, the laser projection module receives the spatial vector parameters of the steel bar axis and the center coordinates P0 of the steel bar end face transmitted by the three-dimensional BIM model construction module. The laser line laying instrument calibrates the laser point at the center of the steel bar end face and projects the inclined laser line L0 of the steel bar in combination with the spatial vector parameters. The spatial vector parameters include the elevation angle α with the horizontal plane, the horizontal deviation angle β with the station reference axis, and the length L of the steel bar.

[0014] The laser projection module receives the center coordinates P2 of the rebar end face projected from the calibration point P1, and calculates the distance deviation P between P0 and P2. 偏 If P 偏 If the distance deviation threshold is not met, the center positioning accuracy of the rebar end face meets the requirements. The midpoint between P0 and P2 is taken as the final coordinates of the end face center. If P... 偏 >Distance deviation threshold, the device automatically backtracks the coordinate system transformation parameters, recalculates the projection angle, and corrects it;

[0015] Two verification points are selected on L0, denoted as M1 and M2 respectively. The angles α1 and α2 between the laser line and the horizontal plane at M1 and M2, and the horizontal deflection angles β1 and β2 between the laser line and the station reference axis are measured using a three-dimensional angle meter. The laser projection module receives the above angles α1 and α2 and the horizontal deflection angles β1 and β2. If |α1-α|≦angle deviation threshold one and |α2-α|≦angle deviation threshold two, |β1-β|≦angle deviation threshold three and |β2-β|≦angle deviation threshold four, then the result is acceptable. If the deviation exceeds the threshold, the equipment automatically adjusts the pitch motor and rotation motor of the laser transmitter, reprojects the laser line and verifies it until the above angle deviations meet the thresholds.

[0016] Furthermore, the AR module includes a calibration submodule, a communication submodule, a SLAM submodule, an analysis submodule, a display and rendering submodule, and an interaction submodule;

[0017] The calibration submodule scans the site environment using SLAM technology and matches the station construction coordinate system to ensure that the coordinates are consistent with the 3D BIM model.

[0018] The communication submodule interacts and transmits data with the 3D BIM model construction module and the detection module.

[0019] The SLAM submodule is used to anchor data to a virtual environment;

[0020] The display rendering submodule renders the data using images and enables virtual touch and voice interaction with construction workers through the interaction module.

[0021] The analysis submodule receives the end face coordinate data of the reserved steel bar and the map and location data of the SLAM submodule through the communication module. Using the center coordinate data of the steel bar end face as the theoretical position, it calculates a 1m×1m square focusing area on the same horizontal plane with the theoretical position center. The square focusing area is then divided into grids, and the coordinates and range of each grid are determined. The grid is then projected upward onto the concrete surface. The display rendering submodule renders the grid projected onto the concrete surface into the display screen of the AR glasses in a visual manner.

[0022] The analysis submodule also receives the signal strength E of each node in the aforementioned grid transmitted by the detection module. 节点 The dataset {E} is obtained. 节点 The analysis submodule will also analyze the signal strength E of each node. 节点 With the pre-stored rebar threshold E in the AR module 钢筋 When E is compared, 节点 ≥E 钢筋At that time, the three-dimensional coordinates of the grid node are anchored and recorded as a suspected node. The coordinates of the reinforcing steel below the concrete corresponding to the signal intensity of the suspected node are calculated using the "signal strength-burial depth" calibration curve, and the dataset {E} is obtained. 疑似节点 - Coordinates}; The analysis submodule compares and selects the grid node M with the strongest signal strength from multiple suspected nodes, anchors the coordinates of the grid node, and renders it in a visual manner on the display screen of the AR glasses through the display rendering submodule;

[0023] The analysis submodule receives the signal strength collected by the electromagnetic detection device as it rotates 360° around the strongest grid node M at a preset step size, forming a dataset {E}. 旋转}, from which the maximum signal strength E is identified max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, determine if the fluctuation amplitude is ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar.

[0024] Furthermore, if the analysis submodule determines that the condition of "fluctuation amplitude ≤ 10% and no single prominent peak" is not met, the display rendering submodule outputs "Rotate the electromagnetic detection device at point M around an axis perpendicular to the concrete surface until the signal strength reaches its maximum value E". max The text prompt "location";

[0025] The analysis submodule calculates the maximum signal strength E when the electromagnetic detection device is rotated to its maximum value. max The axial direction at the time of the event (i.e., the axial direction of the reserved reinforcing bar) is visualized and rendered onto the AR glasses' display screen via the display rendering submodule. The analysis submodule receives the signal strength collected in real time by the electromagnetic detection device moving along the axial direction of the reserved reinforcing bar, and obtains the dataset {E}. 轴线 The coordinates of the reinforcing steel bars below the concrete corresponding to the signal strength are calculated using the "signal strength-burial depth" calibration curve, resulting in the dataset {E}. 轴线 -coordinates}, and {E} 轴线 - Coordinates} are fitted to obtain the change curve. Analysis is performed to determine when the curve exhibits the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥ 80%) → stable background signal". The critical point A(x) at which the signal begins to attenuate is recorded. 峰 ,y 峰 ,z 峰This point is the axial boundary point of the rebar end (the junction between the rebar end and the side wall).

[0026] The analysis submodule calculates the axis perpendicular to the axis of the reinforcing bar at point A, projects it onto the concrete surface, and then renders this axis direction visually onto the AR glasses' display screen via the display rendering submodule. The analysis submodule receives electromagnetic detection equipment moving along point A in a direction perpendicular to the axis of the reinforcing bar to obtain the signal strength dataset {E}. 垂直 The data is transmitted to the analysis submodule, which identifies the strongest signal intensity and calculates the peak coordinates O(x) corresponding to the strongest signal intensity using the "signal intensity-burial depth" calibration curve. 峰 ,y 峰 ,z 峰 And anchor the rendering display;

[0027] Furthermore, the analysis submodule calculates multiple concentric virtual ring paths on the same horizontal plane, centered on the strongest grid node M or the strongest peak point O, and projects them upwards onto the concrete surface. The electromagnetic detection device then probes along these virtual ring paths at preset step sizes to obtain the signal strength dataset {E}. 环}, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面 At that time, this point is a valid contour point. The coordinates corresponding to the valid contour point are calculated using the "signal strength-burial depth" calibration curve, and the dataset {E} is obtained. 有效轮廓 - Coordinates}, anchoring the coordinates corresponding to all valid contour points, the analysis submodule performs surface fitting on the valid contour points to generate the actual contour line of the rebar end face, and the analysis submodule projects the actual contour line of the rebar end face upward onto the concrete surface to generate a "virtual projection column".

[0028] The display rendering submodule renders and displays the "virtual projection column". The projection area of ​​the virtual projection column on the concrete surface is the boundary of the chiseling range. The area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the end face of the steel bar in real time, and calculate the average value (buried depth). The virtual projection column constitutes the chiseling range guide.

[0029] The display rendering submodule transmits the "virtual projection column" data to the interaction submodule, enabling virtual interaction with construction personnel.

[0030] Furthermore, the detection module transmits the actual end face center coordinates of a certain reserved rebar back to the 3D BIM model construction module. The 3D BIM model construction module, combined with the unique identifier of the reserved rebar, automatically corrects the end face center coordinates.

[0031] A method for rapid BIM positioning of reserved steel bars in subway station construction, based on the aforementioned rapid BIM positioning system for reserved steel bars, includes the following steps:

[0032] S1: Based on the subway station design drawings, construct a 3D BIM model in BIM software, assign a unique identifier to each reserved steel bar and enter the steel bar parameters;

[0033] S2: Export the above model in an AR-compatible format, synchronize it to the AR glasses database, and integrate the electromagnetic detection device into the AR glasses;

[0034] S3: Construction workers bind the steel bars to the preset positions according to the reserved steel bar parameters in the 3D BIM model, and calibrate the tilt direction and end face center to complete the concrete pouring;

[0035] S4: After the concrete has initially set, construction workers carry electromagnetic detection equipment, wear AR glasses, and enter the preset position of the reserved steel bars according to the coordinate guidance of the BIM model.

[0036] S5: If the reserved steel bars at the preset location are mistakenly covered by concrete, the electromagnetic detection device scanning mode is turned on according to the detection guide generated by the BIM rapid positioning system. After the information of the reserved steel bars is detected is analyzed and processed, it is anchored and rendered in the AR glasses' field of view to generate a chiseling range guide.

[0037] S6: Construction workers chisel the reserved steel bars to the reserved positions according to the chiseling range guide;

[0038] S7: Compare the actual location of the detected reserved steel bars with the location parameters in the BIM model, calculate the deviation value and correct it.

[0039] Furthermore, integrating the electromagnetic detection device into the AR glasses in step S2 includes the following sub-steps:

[0040] S21. Combine the concrete strength parameters to preset the electromagnetic field attenuation coefficient of the electromagnetic detection equipment to ensure that the detection accuracy of the steel bars after penetrating the concrete is ≤ ±5mm, and eliminate the interference of concrete strength on the signal.

[0041] S22. Select an electromagnetic detection device with low-frequency electromagnetic field emission and secondary magnetic field reception functions, and connect it to the AR glasses via Bluetooth.

[0042] S23. The electromagnetic detection equipment is calibrated using steel bars at known locations and depths. This involves having the electromagnetic detection equipment scan the steel bars at the known locations and depths, recording the difference between the detection signal and the actual location, and the AR module's built-in system automatically adjusting the signal conversion parameters. Subsequent detections will be corrected accordingly to ensure accurate results.

[0043] Furthermore, step S5 includes the following sub-steps:

[0044] S51. Coordinate calibration: Before starting the scanning mode, the AR glasses scan the site environment using SLAM technology, match the station construction coordinate system, ensure that the coordinates are of the same origin as the 3D BIM model, and calibrate the electromagnetic detection equipment with the station construction coordinate system.

[0045] S52. Peak Threshold Calibration and "Signal Strength-Buried Depth" Calibration Curve Fitting: Various specifications of reinforcing bars, consistent with on-site construction, were selected as calibration samples. An adjustable-thickness concrete sheet was placed over each end of the reinforcing bar and anchored at the end center. The electromagnetic detection equipment was placed against the projection point on the surface of the concrete sample block directly above the end center. Using this point as the center, the surrounding area was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain the signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 端面 Multiple specifications of steel bars, consistent with those used in on-site construction, were selected as calibration samples. Their sidewalls were covered with thin, adjustable-thickness concrete sheets. The electromagnetic detection equipment was placed directly above the concrete sample surface, and the projection area of ​​the sidewall onto the concrete sample surface was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 钢筋 ;

[0046] The "signal strength-buried depth" calibration curve was established through preliminary tests simulating on-site construction conditions. Concrete test blocks with the same strength grade and aggregate ratio as the actual construction were selected. Reinforcing bars of the same specifications (diameter and material) as the pre-reserved reinforcing bars were embedded in the test blocks. The positions of the reinforcing bars were fixed according to a preset buried depth gradient (e.g., 5mm, 10mm, 15mm…100mm, covering common erroneous buried depths), ensuring that the vertical distance between the center of the reinforcing bar and the concrete surface accurately corresponded to each buried depth value. Then, the electromagnetic sensor to be calibrated was placed directly above the corresponding reinforcing bar on the test block surface, and the device was turned on to collect stable signal strength values ​​at each buried depth. Each buried depth was repeatedly sampled three times, and the average value was taken to reduce errors. Finally, a smooth curve was generated by fitting data (e.g., linear fitting, polynomial fitting) with the buried depth value on the x-axis and the corresponding average signal strength on the y-axis. After removing outlier data points and marking confidence intervals, the calibration curves for different signal strengths and corresponding buried depths were obtained, ensuring matching with the actual on-site detection environment. The analysis submodule called this curve and associated it with the station construction coordinate system for calibration, calculating the buried depth z based on the measured signal strength. 深Because the sensor is in close contact with the concrete surface, its three-dimensional coordinates (x, y, z) are... 表 ,y 表 ,z 表 Subtract the embedment depth to obtain the actual coordinates (x) of the reinforcing bar. 表 ,y 表 ,z 表 -z 深 ), and lightly bound to the corresponding signal;

[0047] S53. Initial Grid Scan Confirms Reinforcement Presence: Construction workers wear AR glasses. The system's AR module uses green crosshairs to anchor the theoretical positions of the reinforcing bars in the 3D BIM model. The system's AR module calculates a 1m×1m square focusing area centered on the theoretical position on the same horizontal plane and divides it into grids. The coordinates and range of each grid are determined, and the grid is projected upwards onto the concrete surface. The grid projected onto the concrete surface is then rendered visually onto the AR glasses' display screen: 1) The display screen divides the area into a uniform 20mm×20mm grid (50×50 nodes in total); 2) Construction workers hold sensors and move them at a constant speed along the grid nodes (moving speed ≤5cm / s to avoid missed signal detection). The bottom surface of the sensor is in close contact with the concrete surface, and the signal strength E of each node is recorded in real time. 节点 3) The system's AR module automatically generates a signal strength heatmap and automatically determines when a certain E 节点 ≥E 钢筋 When the grid node is identified as a suspected node, its coordinates are calculated and anchored. If no suspected area is detected, the scanning range can be expanded to 2m×2m and the operation repeated.

[0048] S54. The system's AR module compares and selects the grid node M with the strongest signal strength from multiple suspected nodes. This point is projected onto the concrete surface. Construction personnel hold an electromagnetic detection device and slowly rotate it 360° around an axis perpendicular to the concrete surface, with rotation increments of 5°, collecting the signal strength dataset {E} throughout the process. 旋转 The system's AR module identifies the maximum signal strength E from this. max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, if the fluctuation amplitude is judged to be ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar, and the mesh node M is marked and visualized for recognition.

[0049] S55. If condition S54 is not met, according to the system prompts, the construction personnel should rotate the electromagnetic detection equipment around an axis perpendicular to the concrete surface until the signal strength reaches its maximum value E. max At this location, the axial direction of the electromagnetic detection equipment (the central axis of symmetry of the equipment) is the axial direction of the reinforcing bar. The AR module projects this axial direction onto the concrete surface. Then, following the projection axis guidance generated by the system's AR module, the construction personnel hold the electromagnetic detection equipment and move it along both sides of this projection axis, with a scanning speed of 3cm / s and a step size of 2mm. The signal strength and corresponding coordinates are recorded in real time, resulting in a signal strength-coordinate dataset {E}. 轴线 -coordinates}, the system AR module will use the above dataset {E} 轴线 - Coordinates} are fitted to obtain the change curve. When the system analysis curve exhibits the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥ 80%) → stable background signal", the system records the critical point A(x) at which the signal begins to attenuate. 峰 ,y 峰 ,z 峰 The system marks and renders the point, which is the axial boundary point of the rebar end (the junction between the rebar end and the side wall). To verify the accuracy, the construction personnel scan in reverse once according to the system prompts. If the coordinate deviation of point A in the two detections is ≤3mm, the average value is taken as the final boundary point, and the coordinates of the point are recorded.

[0050] S56. Following the projection axis guidance from the AR glasses, construction personnel move the electromagnetic detection device along point A in a direction perpendicular to the axis of the reinforcing bar, scanning within a range of ±100mm with a step size of 1mm, ensuring complete coverage of the end section, and obtaining the signal strength dataset {E}. 垂直 The system's AR module automatically identifies the strongest peak point O(x) from it. 峰 ,y 峰 ,z 峰 The image is then anchored and rendered to show that the point is located at the end face of the buried rebar.

[0051] S57. Using the strongest grid node M from S54 or the strongest peak point O from step S56 as the center, the AR module sets up multiple virtual ring paths and projects them onto the concrete surface. The distance between adjacent rings is constant. The electromagnetic detection device scans each ring path sequentially from the inside out, with a rotation step of 3° and a scanning speed of 5° / s, to obtain the signal strength dataset {E}. 环}, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面 At that time, mark the point as a valid contour point, calculate the corresponding three-dimensional coordinates, and obtain the dataset {E}. 有效轮廓 - Coordinates}, anchor all valid contour points and render the display;

[0052] S58. After scanning, the AR module automatically removes abnormal contour points: Abnormal contour points include: 1) Points with signal fluctuation amplitude > 8% (excluding interference from concrete impurities); 2) Points with a deviation from the 3D BIM model section contour > 5mm (excluding interference from adjacent metals); 3) The AR module performs surface fitting on the remaining valid contour points to generate the actual contour line of the steel bar end face, with a fitting error ≤ ±2mm.

[0053] S59. The AR module projects the fitted actual outline of the rebar end face upwards onto the concrete surface, generating a "virtual projection column" which is then rendered and displayed in the AR glasses. The projection area of ​​this virtual projection column on the concrete surface is the boundary of the chiseling range, and the area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the rebar end face in real time, calculating the average value (burying depth). This virtual projection column serves as a guide for the chiseling range for construction workers. The AR module enables virtual interaction between the "virtual projection column" data and the construction workers.

[0054] Compared with the prior art, the present invention has at least one of the following technical effects:

[0055] 1. Completely change the manual, experience-based blind chiseling mode. The chiseling range is precisely defined by the "virtual projection column". The chiseling diameter is reduced from the traditional 100-150mm to 5-10mm beyond the outline of the steel bar end face, avoiding excessive chiseling that damages the concrete body and steel bar protective layer. Combined with the "signal strength-buried depth" calibration curve, the chiseling depth is precisely controlled, eliminating structural damage caused by unknown buried depth and reducing the risk of leakage in the later stage.

[0056] 2. The 3D BIM model assigns a unique identifier to the rebar, and with AR guidance, it can directly lock the detection area without the need for manual comparison with drawings. This enables rapid location of misplaced rebar. The grid initial scanning + node determination process significantly shortens the time required to locate single-row splice bars. AR displays chiseling guidance in real time, reducing rework caused by "hollowing out" or "incorrect chiseling". The waterproof membrane laying process is no longer delayed, and the overall construction progress is improved.

[0057] 3. AR glasses visualize the location, depth, and chiseling range of steel bars through green cross lines, heat maps, and virtual projection columns, allowing construction workers to operate accurately without professional measurement skills. The interactive function supports touch query of coordinates, depth, and other data, replacing traditional drawing interpretation, reducing reliance on experienced technicians, and shortening the on-site operation training cycle.

[0058] 4. The BIM model provides accurate theoretical coordinates in the early stages, interacts with the laser projection module to control the tilt direction and end center of the reserved steel bars, and improves the positioning accuracy and efficiency of steel bar binding. The laser projection module's dual-point calibration eliminates initial positioning errors. After construction, the SLAM submodule feeds back the actual end coordinates to the BIM model and automatically completes parameter correction, forming a closed-loop management of "modeling-construction-detection-correction". The corrected model provides accurate data for subsequent processes, avoids cumulative errors, and improves the overall project accuracy.

[0059] 5. Electromagnetic detection is deeply integrated with AR and BIM, eliminating the need for additional sets of measurement equipment; precise chipping reduces the consumption of concrete repair materials and labor rework costs; BIM closed-loop management reduces the cost of subsequent structural reinforcement; it lowers the overall cost of positioning and chipping of pre-reserved steel bars for a single station, while also reducing material waste and meeting the requirements of green construction. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a module architecture diagram of the BIM rapid positioning system for the reserved reinforcement bars in this application. Detailed Implementation

[0062] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0063] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0064] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0065] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0066] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0067] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0068] See appendix Figure 1 The BIM rapid positioning system for reserved steel bars in subway station construction includes a 3D BIM model building module, a laser projection module, a detection module, and an AR module.

[0069] The 3D BIM model building module constructs a 3D BIM model based on the subway station design drawings. For example, using Revit software, each reserved steel bar is given a unique identification and steel bar parameters are entered. The unique code includes area-axis-serial number, which is used by the system to identify the corresponding steel bar and also by construction personnel to verify on-site, such as scanning the steel bar QR code on-site to verify the reserved steel bar information.

[0070] The laser projection module controls the laser to position the tilt direction and end face center of the reserved steel bars according to the reserved steel bar parameters in the 3D BIM model, and calibrates the tilt direction and end face center. The reserved steel bar parameters include, but are not limited to: the diameter, length, shape of the steel bar, and three-dimensional coordinates of the center point of the end face of the steel bar. Specifically, the laser projection module receives the spatial vector parameters of the rebar axis and the center coordinates P0 of the rebar end face from the 3D BIM model construction module. It controls the laser line laying instrument to calibrate the laser point at the center of the rebar end face and projects a laser line L0 to clearly indicate the inclined direction of the rebar, based on the spatial vector parameters. The spatial vector parameters include the elevation angle α with the horizontal plane, the horizontal deviation angle β with the station reference axis, and the length L of the rebar. The spatial vector parameters (α, β, L) uniquely determine the rebar orientation. By visualizing the laser line, the orientation angle can be verified without additional measuring tools. On-site workers can directly compare and construct, reducing reliance on professional surveyors and improving the efficiency of rebar positioning. The linear propagation characteristics of the laser ensure that the orientation line L0 is precisely parallel to the actual axis of the rebar. The visualization of the elevation angle and horizontal deviation angle solves the problem of "invisible and inaccurate measurement" of inclined rebar. At the same time, with subsequent calibration, it avoids positioning errors or misunderstandings caused by construction workers relying on drawings on-site.

[0071] The end face center calibration is as follows: The laser projection module receives the center coordinates P2 of the rebar end face projected from the calibration point P1 (distance ≥ 1.5m from P0), and calculates the distance deviation P between P0 and P2. 偏 If P 偏 If the distance deviation threshold (e.g., 3mm) is not met, the center positioning accuracy of the rebar end face meets the requirements. The midpoint between P0 and P2 is taken as the final center coordinate of the end face. If P 偏If the distance deviation threshold is exceeded, the equipment automatically backtracks the coordinate system transformation parameters, recalculates the projection angle, and corrects it. The tilt direction calibration is as follows: Two verification points are selected on L0, denoted as M1 and M2 respectively. The angles α1 and α2 between the laser line and the horizontal plane at M1 and M2, and the horizontal deflection angles β1 and β2 with the station reference axis are measured using a three-dimensional angle meter. The laser projection module receives the above angles α1 and α2 and the horizontal deflection angles β1 and β2. If |α1-α|≦angle deviation threshold one (e.g., 0.1°) and |α2-α|≦angle deviation threshold two (e.g., 0.1°), |β1-β|≦angle deviation threshold three (e.g., 0.05°) and |β2-β|≦angle deviation threshold four (e.g., 0.05°), then the direction is qualified. If the deviation exceeds the threshold, the equipment automatically adjusts the pitch motor and rotation motor of the laser emitter, reprojects the laser line, and verifies it until the above angle deviations meet the threshold. By verifying the end face center at two points and checking the direction at two points, combined with automatic backtracking correction and motor adjustment, coordinate transformation and projection angle errors are accurately eliminated, ensuring that the accuracy of end face center positioning and tilt direction projection meets the requirements. No manual repeated verification is required, which improves calibration efficiency and construction reliability, and ensures the accurate implementation of subsequent procedures.

[0072] The principle of electromagnetic wave detection of rebar is as follows: An alternating electromagnetic field is generated by a transmitting coil, which penetrates the concrete and excites eddy currents in the rebar. The receiving coil then captures the secondary magnetic field generated by the eddy currents and converts it into an electrical signal (represented by a "signal strength" value). The higher the signal strength, the stronger the secondary magnetic field, which also means a tighter "electromagnetic coupling" between the device and the rebar. Compared with the sidewall, the metal cross-sectional area of ​​the rebar end face (a circular plane approximately perpendicular to the rebar's direction) is more concentrated, and the "directly facing area" between the end face and the device's electromagnetic field is the largest. When the device scans to the center of the end, the coupling strength between the electromagnetic field and the rebar reaches its highest point, and the eddy currents and secondary magnetic field are also strongest. Therefore, the signal strength will further increase from the stable peak range, forming a significant "signal peak" (which is also the key basis for locking the end center). The signal reaches its peak at the end position because the electromagnetic coupling with the sensor is strongest. The signal strength at the sidewall of the rebar is usually lower than that at the end because the electromagnetic coupling strength with the sensor is not as strong as at the end.

[0073] The detection module is used to control the start and stop of the electromagnetic detection equipment for the reserved steel bars, transmit data, and receive and transmit detection data. The construction personnel wearing AR glasses move the electromagnetic detection equipment. The electromagnetic detection equipment preferably has an electromagnetic sensor with a central axis of symmetry, and the electromagnetic wave detection range penetrates the concrete by no less than 200mm. This distance covers the burial depth of all the reserved steel bars that are mistakenly buried on the construction site, so as to avoid the situation that the detection distance is insufficient.

[0074] The "signal strength-buried depth" calibration curve was established through preliminary tests simulating on-site construction conditions: Concrete test blocks with the same strength grade and aggregate ratio as the actual construction were selected, and reinforcing bars of the same specifications (diameter and material) as the pre-reserved reinforcing bars were embedded. The positions of the reinforcing bars were fixed according to a preset buried depth gradient (e.g., 5mm, 10mm, 15mm…100mm, covering common erroneous buried depths), ensuring that the vertical distance between the center of the reinforcing bar and the concrete surface accurately corresponded to each buried depth value. Then, the electromagnetic sensor to be calibrated was placed directly above the corresponding reinforcing bar on the surface of the test block, and the device was turned on to collect stable signal strength values ​​at each buried depth. Each buried depth was repeatedly sampled three times, and the average value was taken to reduce errors. Finally, a smooth curve was generated by fitting data (e.g., linear fitting, polynomial fitting) with the buried depth value on the x-axis and the corresponding average signal strength on the y-axis. After removing outlier data points and marking the confidence interval, the calibration curve for different signal strengths and corresponding buried depths was obtained, ensuring matching with the actual on-site detection environment. The analysis submodule calls this curve and calculates the buried depth z (depth) based on the measured signal strength. Because the sensor is in close contact with the concrete surface, its three-dimensional coordinates (x, y, z) are... 表 ,y 表 ,z 表 Subtract the embedment depth to obtain the actual coordinates (x) of the reinforcing bar. 表 ,y 表 ,z 表 -z 深 After being lightly bound to the corresponding signal, it is transmitted to the AR module.

[0075] The AR module interacts with the 3D BIM model building module and the detection module. The AR module generates detection guidelines, calculates the chiseling range for the embedded reinforcing bars, controls the AR glasses to synchronously display the detection guidelines and chiseling range, and corrects the parameters of the embedded reinforcing bars in the 3D BIM model building module. When embedded reinforcing bars are being poured, construction workers wearing AR glasses move the electromagnetic detection device to a designated location according to the detection guidelines displayed on the AR glasses. When the AR glasses identify that the coordinates of the electromagnetic detection device match the detection guide position, the AR module sends a signal to the detection module, which then controls the electromagnetic detection device to turn on. When the AR glasses identify that the coordinates of the electromagnetic detection device leave the detection guide position, the detection module controls the electromagnetic detection device to turn off; alternatively, construction workers can control the electromagnetic detection device to turn on and off. The AR module calculates and renders the chiseling range through the AR glasses, including the chiseling range on the concrete surface. Regarding the excavation depth (burial depth), construction workers wear AR glasses and move the excavation tools to the excavation area. They then precisely excavate according to the excavation depth (burial depth), solving the problems in the background technology such as "blindness of manual excavation, poor positioning accuracy, excessive excavation range, failure to consider rebar displacement, and over-excavation due to inaccurate identification of burial depth". With the help of electromagnetic detection equipment and the detection guidance of AR glasses and the excavation range, construction workers can accurately identify the location and burial depth of mistakenly buried rebars, avoid the fluctuation error of blind manual excavation, achieve precise excavation, save manpower and time, and avoid structural damage caused by excessive excavation range or over-excavation.

[0076] The AR module includes a calibration submodule, a communication submodule, a SLAM submodule, an analysis submodule, a display and rendering submodule, and an interaction submodule;

[0077] The calibration submodule scans the site environment using SLAM technology and matches the station construction coordinate system to ensure that the coordinates are consistent with those of the 3D BIM model. At the same time, the detection module associates and calibrates the electromagnetic detection equipment with the station construction coordinate system to ensure that the 3D BIM model, AR glasses, and electromagnetic detection equipment are under the same coordinate system.

[0078] The communication submodule interacts and transmits data with the 3D BIM model construction module and the detection module.

[0079] The SLAM submodule performs environmental anchoring on the end face coordinates of the aforementioned reserved steel bars (i.e., marks the end face coordinates on the map of the SLAM submodule), and renders the end face coordinate data with green crosshairs through the display rendering submodule. It also enables virtual touch and voice interaction with construction personnel through the interaction module. For example, when construction personnel touch the virtual coordinates, the coordinate values ​​are displayed. Of course, the coordinate values ​​can also be rendered and displayed in AR.

[0080] The analysis submodule receives the end face coordinate data of the reserved rebar transmitted by the communication module, and the map and location data from the SLAM submodule. Using the center coordinate data of the rebar end face as the theoretical position, it calculates the horizontal plane on which the center coordinates lie. A 1m×1m square focusing area is defined with the theoretical position center, and the square focusing area is divided into grids. The coordinates and range of each grid are determined, and the grid is projected upward onto the concrete surface. The display and rendering submodule renders the grid projected onto the concrete surface in a visual manner onto the display screen of the AR glasses for construction personnel to view. At the same time, it displays a text description of the rendered grid as a guide, such as "electromagnetic sensor moving grid". Construction personnel move the electromagnetic sensor at a constant speed according to the AR coordinate guide to accurately traverse all grid nodes and avoid blind detection.

[0081] The analysis submodule receives the signal strength E of each node in the aforementioned grid transmitted by the detection module. 节点 The dataset {E} is obtained. 节点 The analysis submodule will analyze the signal strength E of each node. 节点 With the pre-stored rebar threshold E in the AR module 钢筋 When E is compared, 节点 ≥E 钢筋 At that time, the three-dimensional coordinates of the grid node are anchored and recorded as a suspected node. The coordinates of the reinforcing steel below the concrete corresponding to the signal intensity of the suspected node are calculated using the "signal strength-burial depth" calibration curve, and the dataset {E} is obtained. 疑似节点 - Coordinates}, and render and display them in the AR glasses (with special colors or accompanying text descriptions). Suspected nodes mean that there may be steel bars below the node, but it is not yet possible to determine whether it is the end face or the side face; the analysis submodule compares and selects the grid node M with the strongest signal strength from multiple of the above suspected nodes (the point below which is most likely the end face of the steel bar, which is conducive to quickly finding the end face of the steel bar), anchors the three-dimensional coordinates of the grid node, and renders it in a visual way on the display screen of the AR glasses through the display rendering submodule (with special colors or accompanying text descriptions).

[0082] Then, the location of the reinforcing bar below the aforementioned grid node M is further determined using the following principle: The end face of the reinforcing bar is a circular plane perpendicular to its direction, with a concentrated metal cross-sectional area and a symmetrical structure. When the electromagnetic detection device rotates around it 360°, the coupling strength between the electromagnetic field and the end face is uniform, and the signal has no obvious fluctuations (usually the fluctuation amplitude is ≤10%, but it can be flexibly set according to the actual situation), and there will be no single prominent peak. On the other hand, the side wall of the reinforcing bar is a long cylindrical surface, with the strongest coupling only along the direction of its direction. When rotated, the signal will fluctuate significantly and there will be a significant single peak. By judging the characteristics of "low fluctuation amplitude + no single prominent peak", the end face of the reinforcing bar and the side wall can be accurately distinguished, and then it can be determined whether the strongest grid node M is above the end face of the reinforcing bar. Based on this, the construction personnel rotate the electromagnetic detection device around the strongest grid node 360° in a preset step size according to the AR prompts. The analysis submodule receives the signal strength collected by the electromagnetic detection device throughout the 360° rotation of the strongest grid node M in a preset step size, forming a dataset {E}. 旋转}, and identify the maximum signal strength E from it. max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, determine if the fluctuation amplitude is ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar.

[0083] If the analysis submodule determines that the above-mentioned condition of "fluctuation amplitude ≤ 10% and no single prominent peak" is not met, it determines that the strongest grid node M is located above the side of the buried rebar, and outputs "Rotate the electromagnetic detection device at point M around the axis perpendicular to the concrete surface until the signal strength reaches the maximum value E" through the display rendering submodule. max The system prompted the construction workers to rotate the electromagnetic detection equipment around an axis perpendicular to the concrete surface until the signal strength reached its maximum value, E, according to the system's instructions. max At this point (using the signal strength value displayed in real-time by the AR glasses as a prompt), the central axis of the electromagnetic detection device (i.e., an electromagnetic sensor with a central axis of symmetry) is aligned with the axis of the reserved rebar. The principle is "maximum matching of electromagnetic coupling directions": the central axis of the electromagnetic detection device is the "main energy direction" of its emitted electromagnetic field. The rebar, being a slender metallic body, exhibits the strongest magnetic and electrical conductivity along its own axis. When the device axis is parallel to the rebar axis, the electromagnetic field can penetrate the rebar to the maximum extent and excite strong eddy currents. The secondary magnetic field generated by these eddy currents can also be fully captured by the device, at which point the signal strength reaches its peak value E. maxIf the axes of the two are not parallel, the "fit" between the electromagnetic field and the reinforcing steel decreases, the magnetic field coupling weakens, and the signal weakens. When rotating the equipment, the maximum signal value will only occur when the axis is precisely parallel to the axis of the reinforcing steel. Therefore, E max The direction of the equipment axis at that location can be used as a reference for the direction of the reinforcing bar axis.

[0084] Knowing the rebar axis, the next step is to detect the rebar end using the rebar axis. The principle is as follows: The rebar sidewall is a long, cylindrical sidewall that extends along the rebar direction. The structure is continuous and uniform. When the electromagnetic sensor scans along the rebar direction, the emitted electromagnetic field can continuously and stably couple with the sidewall—the eddy current intensity is stable, and the secondary magnetic field is also stable. Therefore, the signal strength captured by the receiving coil will remain in a "stable high value range" (i.e., a "stable peak range") without significant fluctuations. The end is the "end point" of the rebar. Beyond the end, there is no more rebar. When the device continues to scan forward from the end (away from the rebar area), the electromagnetic field loses the rebar as a "conductor target" and can no longer generate eddy currents. The secondary magnetic field will disappear instantly, and the corresponding signal strength will drop rapidly from the peak value at the end, with an attenuation of more than 80%, eventually dropping to a "stable background signal" (only capturing weak signals of environmental interference, with no actual target response). When the device scans along the rebar direction, the complete process of signal change is: "stable peak range → rapid attenuation (beyond the end, attenuation ≥ 80%) → stable background signal (away from the rebar)" fluctuation. Based on this, in order to locate the rebar ends, the analysis submodule projects the axis onto the concrete surface to obtain the projected axis. The display rendering submodule then renders this projected axis onto the concrete surface displayed on the AR glasses. Construction workers wearing AR glasses control an electromagnetic detection device to move precisely along this axis at a specific scanning speed and step size. The analysis submodule receives the real-time signal strength collected by the electromagnetic detection device as it moves along the axis of the reserved rebar, obtaining the dataset {E}. 轴线 The coordinates of the reinforcing steel bars below the concrete corresponding to the signal strength are calculated using the "signal strength-burial depth" calibration curve, resulting in the dataset {E}. 轴线 -coordinates}, dataset {E 轴线 The change curve is obtained through real-time synchronous fitting of the coordinate system. The horizontal axis represents the three-dimensional coordinate system, and the vertical axis represents the signal strength. Analysis is performed to determine when the signal strength curve exhibits the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥ 80%) → stable background signal." The critical point A(x) at which the signal begins to attenuate is recorded. 峰 ,y 峰 ,z 峰 This point is the axial boundary point of the rebar end (the junction between the rebar end and the sidewall). Anchor it and render the result (text or symbols can be added for explanation). The specific steps for locating critical point A are as follows:

[0085] 1) The AR module visualizes the determined rebar axis direction in the AR glasses. Construction workers wear AR glasses and hold the device with integrated electromagnetic sensors and move at a constant speed with reference to this direction. During the movement, the SLAM submodule tracks the device coordinates in real time to ensure that the device always moves along the axis direction and avoids deviation that would cause signal acquisition distortion. At the same time, the sensor continuously collects signals and transmits them to the analysis submodule in real time.

[0086] 2) The analysis submodule receives the real-time signal strength data transmitted by the electromagnetic sensor as it moves along the axis, and calculates the corresponding coordinates (the electromagnetic sensor moves along the axis in preset step sizes, detecting once at each step size node). The data is then sorted by acquisition time and device coordinates to form {E... 轴线 The dataset (containing the correspondence between "location and signal strength") is transformed into a continuous "location-signal strength" change curve through a data fitting algorithm, which intuitively presents the fluctuation pattern of the signal with the distance of movement, facilitating subsequent feature identification.

[0087] 3) The analysis submodule uses a "sliding window + threshold judgment" algorithm to perform segmented analysis on the fitted curve. The sliding window algorithm divides the continuous signal curve into multiple "windows" of fixed length (e.g., 10 data points), and calculates the average value and standard deviation (fluctuation amplitude) of the signal within each window. The threshold judgment presets thresholds for the stable interval (fluctuation ≤ 5%), the attenuation interval (decline ≥ 80%), and the background signal (low intensity + fluctuation ≤ 3%). Segmentation is achieved by comparing the window data with the thresholds: when multiple consecutive signal intensity values ​​remain at a high level and the fluctuation amplitude is ≤ 5%, it is marked as a "stable peak interval", corresponding to the sensor being above the rebar sidewall; when multiple consecutive signal intensity values ​​drop rapidly from the stable peak and the attenuation amplitude is ≥ 80% within a 10cm movement distance, it is marked as a "rapid attenuation interval", corresponding to the sensor moving from the sidewall towards the end; when the attenuated signal intensity value remains at a low level and the fluctuation is ≤ 3%, it is marked as a "stable background signal interval", corresponding to the sensor being removed from the rebar.

[0088] 4) The analysis submodule checks each data point from the identified "stable peak interval" to the subsequent data points one by one, and records the difference between each step node and the average signal strength of the previous window. When the signal value of a data point decreases by ≥5% compared to the average value of the previous window (a preset small threshold is used to ensure the capture of the initial attenuation), and the signal value continues to decrease for the next 3 consecutive step nodes, the step node is marked as a "potential boundary point". Then, it checks whether the signal within a range of 10cm after the step node meets the requirement of "total decrease from stable peak to background signal ≥80%". If it meets the requirement, it is confirmed as the final boundary point A. The three-dimensional coordinates of the step node are recorded, and it is determined to be the axial boundary point between the end of the rebar and the side wall, thus completing the end position locking.

[0089] The analysis submodule calculates an axis passing through point A and perpendicular to the axis of the reinforcing bar, projects it onto the concrete surface, and then renders this projected axis visually onto the AR glasses display via the display rendering submodule. This projected axis is required to be sufficiently long, for example, 10cm-20cm, to ensure coverage of the end face. Construction workers wearing AR glasses move the electromagnetic sensor precisely along the projected axis at preset step lengths and speeds, following prompts. The analysis submodule receives the signal strength from the detection module and calculates the coordinate data, obtaining a signal strength-coordinate dataset {E}. 垂直 The dataset contains a one-to-one correspondence between "real-time 3D coordinates of the sensor and corresponding signal strength". The coordinates are tracked and synchronized to the dataset in real time by the SLAM submodule and transmitted to the analysis submodule. The analysis submodule iterates through the dataset to identify the strongest signal strength, and then retrieves the real-time 3D coordinates of the sensor associated with the strongest signal strength value in the dataset, i.e., the peak point coordinates O(x) 峰 ,y 峰 ,z 峰 And anchor and render the display;

[0090] The analysis submodule contains a pre-set "signal strength-burial depth" calibration curve for the electromagnetic detection equipment (established from previous experiments, such as a specific signal strength corresponding to a fixed burial depth). The detection module calculates the burial depth z at that location based on the actual measured signal strength. 深 Since the sensor is in close contact with the concrete surface, its three-dimensional coordinates are (x... 表 ,y 表 ,z 表 ), to surface z 表 Subtract the burial depth z 深 The actual three-dimensional coordinates (x, y) below the concrete corresponding to this signal intensity are obtained. 表 ,y 表 ,z 表 -z 深 The analysis submodule binds the signal strength to the corresponding three-dimensional coordinates O(x,y,z) in a one-to-one correspondence.

[0091] The analysis submodule uses the strongest grid node M or the strongest peak point O as the center to calculate a multi-ringed, concentric virtual ring path on the same horizontal plane, and projects it upwards onto the concrete surface. The area of ​​this multi-ringed, concentric virtual ring is required to be large enough to cover the rebar end faces as much as possible. Construction workers wear AR glasses and move electromagnetic detection equipment to accurately detect along the virtual ring path at preset step sizes, obtaining the signal strength dataset {E}. 环}, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面At that time, this point is a valid contour point. The coordinates corresponding to the valid contour point are calculated using the "signal strength-burial depth" calibration curve, and the dataset {E} is obtained. 有效轮廓 - Coordinates}, anchoring the coordinates corresponding to all valid contour points, the analysis submodule performs surface fitting on all valid contour points to generate the actual contour line of the rebar end face, and the analysis submodule projects the actual contour line of the rebar end face upward onto the concrete surface to generate a "virtual projection column".

[0092] The display rendering submodule renders and displays the "virtual projection column". The projection area of ​​the virtual projection column on the concrete surface is the boundary of the chiseling range. The area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the end face of the steel bar in real time, and calculate the average value (buried depth). The virtual projection column constitutes the chiseling range guide.

[0093] The display rendering submodule transmits the "virtual projection column" data to the interaction submodule for virtual interaction with construction personnel. For example, when construction personnel touch different coordinate points of the virtual projection column, the data such as the value of the coordinate point, the corresponding burial depth, the unique code of the reinforcing bar, the end face area, the volume of the virtual projection column, the highlighted edge outline of the end face, and the highlighted projection area on the concrete surface can be displayed, which is convenient for construction personnel to refer to when excavating.

[0094] When the construction workers excavate the reserved steel bar, the SLAM submodule will detect the actual end face center coordinates of the reserved steel bar and transmit them back to the 3D BIM model building module. The 3D BIM model building module will automatically correct the end face center coordinates by combining the unique identifier of the reserved steel bar.

[0095] Furthermore, this invention also discloses a BIM-based rapid positioning method for reserved steel bars in subway station construction, based on the aforementioned BIM rapid positioning system, comprising the following steps:

[0096] S1: Based on the subway station design drawings, construct a 3D BIM model in BIM software, assign a unique identifier to each reserved steel bar and enter the steel bar parameters;

[0097] S2: Export the above model to an AR-compatible format and synchronize it to the AR glasses database. Alternatively, the program of the 3D BIM model building module can be directly edited in the AR glasses chip and connected to a computer for model building. The electromagnetic detection device can be integrated into the AR glasses, and the functions of the detection module, etc., can be edited into the chip of the AR glasses through the program. That is, the present invention preferably edits all the functions of the above BIM rapid positioning system into the chip of the AR glasses, and preferably controls the external device wirelessly.

[0098] S3: Construction workers bind the steel bars to the preset positions according to the reserved steel bar parameters in the 3D BIM model, and calibrate the tilt direction and end face center to complete the concrete pouring;

[0099] S4: After the concrete has initially set, construction workers wearing AR glasses and carrying electromagnetic detection equipment (preferably electromagnetic sensors with a central axis of symmetry) enter the preset position of the reserved steel bars according to the coordinate guidance of the BIM model.

[0100] S5: After the construction personnel arrive at the predetermined coordinates, they use the SLAM submodule of the AR glasses to check whether the coordinates of the reserved steel bar end face meet the requirements. Combined with the analysis submodule, they determine whether the reserved length meets the requirements. If it is found that the reserved steel bar at the preset position is mistakenly covered by concrete, the electromagnetic detection device scanning mode is turned on according to the detection guidance generated by the AR module. After the information of the detected reserved steel bar is analyzed and processed, it is anchored and rendered in the AR glasses' field of view to generate a chiseling range guide.

[0101] S6: Construction workers chisel the reserved steel bars to the reserved positions according to the chiseling range guide;

[0102] S7: Compare the actual location of the detected reserved steel bars with the location parameters in the BIM model, calculate the deviation value and correct it.

[0103] Step S2, integrating the electromagnetic detection device into the AR glasses, includes the following sub-steps:

[0104] S21. Combine the concrete strength parameters to preset the electromagnetic field attenuation coefficient of the electromagnetic detection equipment to ensure that the detection accuracy of the steel bars after penetrating the concrete is ≤ ±5mm, and eliminate the interference of concrete strength on the signal.

[0105] S22. Select an electromagnetic detection device with low-frequency electromagnetic field emission and secondary magnetic field reception functions, and connect it to the AR glasses via Bluetooth.

[0106] S23. Calibrate the electromagnetic detection equipment using steel bars at known locations and depths. That is, have the electromagnetic detection equipment scan the steel bars at the known locations and depths, and record the difference between the detection signal and the actual location (e.g., the signal shows a depth of 5cm, but the actual depth is 6cm, a difference of 1cm). The AR glasses' built-in system automatically adjusts the signal conversion parameters, and subsequent detections are corrected accordingly to ensure accurate results.

[0107] Step S5 includes the following sub-steps:

[0108] S51. Coordinate calibration: Before starting the scanning mode, the AR glasses scan the site environment using SLAM technology, match the station construction coordinate system, ensure that the coordinates are of the same origin as the 3D BIM model, and calibrate the calculation coordinate system of the detection module with the station construction coordinate system.

[0109] S52. Peak Threshold Calibration and "Signal Strength-Buried Depth" Calibration Curve Fitting: Various specifications of reinforcing bars, consistent with on-site construction, were selected as calibration samples. An adjustable-thickness concrete sheet was placed over each end of the reinforcing bar and anchored at the end center. The electromagnetic detection equipment was placed against the projection point on the surface of the concrete sample block directly above the end center. Using this point as the center, the surrounding area was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain the signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 端面 Multiple specifications of steel bars, consistent with those used in on-site construction, were selected as calibration samples. Their sidewalls were covered with thin, adjustable-thickness concrete sheets. The electromagnetic detection equipment was placed directly above the concrete sample surface, and the projection area of ​​the sidewall onto the concrete sample surface was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 钢筋 ;

[0110] The "signal strength-buried depth" calibration curve was established through preliminary tests simulating on-site construction conditions. Concrete test blocks with the same strength grade and aggregate ratio as the actual construction were selected. Reinforcing bars of the same specifications (diameter and material) as the pre-reserved reinforcing bars were embedded in the test blocks. The positions of the reinforcing bars were fixed according to a preset buried depth gradient (e.g., 5mm, 10mm, 15mm…100mm, covering common erroneous buried depths), ensuring that the vertical distance between the center of the reinforcing bar and the concrete surface accurately corresponded to each buried depth value. Then, the electromagnetic sensor to be calibrated was placed directly above the corresponding reinforcing bar on the test block surface, and the device was turned on to collect stable signal strength values ​​at each buried depth. Each buried depth was repeatedly sampled three times, and the average value was taken to reduce errors. Finally, a smooth curve was generated by fitting data (e.g., linear fitting, polynomial fitting) with the buried depth value on the x-axis and the corresponding average signal strength on the y-axis. After removing outlier data points and marking confidence intervals, the calibration curves for different signal strengths and corresponding buried depths were obtained, ensuring matching with the actual on-site detection environment. The analysis submodule called this curve and associated it with the station construction coordinate system for calibration, calculating the buried depth z based on the measured signal strength. 深 Because the sensor is in close contact with the concrete surface, its three-dimensional coordinates (x, y, z) are... 表 ,y 表 ,z 表 Subtract the embedment depth to obtain the actual coordinates (x) of the reinforcing bar. 表 ,y 表 ,z 表 -z 深 ), and lightly bound to the corresponding signal;

[0111] S53. Initial Grid Scan to Confirm Reinforcement Presence: Construction workers wear AR glasses. The system's AR module uses green crosshairs to anchor the theoretical positions of the reinforcing bars in the 3D BIM model. The system's AR module calculates a 1m×1m square focusing area centered on the theoretical position on the same horizontal plane and divides it into grids. The coordinates and range of each grid are determined, and the grid is projected upwards onto the concrete surface. The grid projected onto the concrete surface is then rendered visually onto the AR glasses' display screen: 1) For example, the display screen divides the area into a uniform 20mm×20mm grid (50×50 nodes in total); 2) Construction workers hold sensors and move them at a constant speed along the grid nodes (moving speed ≤5cm / s to avoid missed signal detection). The bottom surface of the sensor is in close contact with the concrete surface, and the signal strength E of each node is recorded in real time. 节点 3) The system's AR module automatically generates a signal strength heatmap and automatically determines when a certain E 节点 ≥E 钢筋 When the grid node is a suspected node (i.e., there is a steel bar in the range of 0-200mm below, and the detection depth is different for different models of electromagnetic sensors), calculate and anchor the coordinates of the corresponding grid node. If no suspected area is detected, the scanning range can be expanded to 2m×2m and the operation can be repeated.

[0112] S54. The system's AR module compares and selects the grid node M with the strongest signal strength from multiple suspected nodes. This point is projected onto the concrete surface. Construction personnel hold an electromagnetic detection device and slowly rotate it 360° around an axis perpendicular to the concrete surface at this projection point, with rotation increments of 5°, collecting the signal strength dataset {E} throughout the process. 旋转 The system's AR module identifies the maximum signal strength E from this. max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, if the fluctuation amplitude is judged to be ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar, and the mesh node M is marked and visualized for recognition.

[0113] S55. If condition S54 is not met, according to the system prompts, the construction personnel should rotate the electromagnetic detection equipment around an axis perpendicular to the concrete surface until the signal strength reaches its maximum value E. maxAt this location, the axial direction of the electromagnetic detection equipment (the central axis of symmetry of the equipment) is the axial direction of the reinforcing bar. The AR module projects this axial direction onto the concrete surface. Then, following the projection axis guidance generated by the system's AR module, the construction personnel hold the electromagnetic detection equipment and move it along both sides of this axial direction, with a scanning speed of 3cm / s and a step size of 2mm. The signal strength and corresponding coordinates are recorded in real time, resulting in a signal strength-coordinate dataset {E}. 轴线 -coordinates}, the system AR module will use the above dataset {E} 轴线 - Coordinates} are fitted to obtain the change curve. When the system analysis curve shows the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥80%) → stable background signal", the system records the critical point A (x peak, y peak, z peak) where the signal begins to attenuate and marks and renders it. This point is the axial boundary point of the rebar end (the junction between the rebar end and the side wall). To verify the accuracy, the construction personnel repeat the scan once in reverse according to the system prompts. If the coordinate deviation of point A in the two detections is ≤3mm, the average value is taken as the final boundary point, and the coordinates of this point are recorded.

[0114] S56. Following the axis guidance of the system in the AR glasses, the construction personnel move the electromagnetic detection device along point A in a direction perpendicular to the axis of the steel bar, with a scanning range of ±100mm and a moving step of 1mm, ensuring complete coverage of the end section, and obtain the signal strength-coordinate dataset {E}. 垂直 - Coordinates}, the system's AR module automatically identifies the strongest peak point O (x peak, y peak, z peak) from it and anchors it for rendering and display. This point is located at the end face of the buried steel bar;

[0115] S57. Using the strongest grid node M from S54 or the strongest peak point O from step S56 as the center, the AR module sets up multiple virtual ring paths, with a fixed distance between adjacent rings. The electromagnetic detection device scans each projected ring path sequentially from the inside out, with a rotation step of 3° and a scanning speed of 5° / s, to obtain the signal strength dataset {E}. 环}, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面 At that time, mark the point as a valid contour point, calculate the corresponding three-dimensional coordinates, and obtain the dataset {E}. 有效轮廓 - Coordinates}, anchor all valid contour points and render the display;

[0116] S58. After scanning, the AR module automatically removes abnormal contour points: Abnormal contour points include: 1) Points with signal fluctuation amplitude > 8% (excluding interference from concrete impurities); 2) Points with a deviation from the 3D BIM model section contour > 5mm (excluding interference from adjacent metals); 3) The AR module performs surface fitting on the remaining valid contour points to generate the actual contour line of the steel bar end face, with a fitting error ≤ ±2mm.

[0117] S59. The AR module projects the fitted actual outline of the rebar end face upwards onto the concrete surface, generating a "virtual projection column" which is then rendered and displayed in the AR glasses. The projection area of ​​this virtual projection column on the concrete surface is the boundary of the chiseling range, and the area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the rebar end face, calculating the average value (buried depth). This virtual projection column serves as a guide for the chiseling range for construction workers. The AR module enables virtual interaction between the "virtual projection column" data and the construction workers. For example, when the construction workers touch different coordinate points of the virtual projection column, the numerical value of that coordinate point, the corresponding buried depth, the unique code of the rebar, the end face area, the volume of the virtual projection column, the highlighted edge outline of the end face, and the highlighted projection area on the concrete surface can be displayed, which is convenient for construction workers to refer to during excavation.

[0118] S60. When the construction workers excavate the reserved steel bar, the SLAM submodule will detect the actual end face center coordinates of the reserved steel bar and transmit them back to the 3D BIM model construction module. The 3D BIM model construction module will automatically correct the end face center coordinates by combining the unique identity of the reserved steel bar.

[0119] The selection of specific parameters in the above implementation plan is only for clearly illustrating how the concept is implemented, and is not a limitation on the concept embodied in the plan. That is, within the scope of the concept protection, the specific parameters can be adjusted according to the actual situation.

Claims

1. A BIM-based rapid positioning system for pre-reserved steel reinforcement in subway station construction, characterized in that: Includes a 3D BIM model building module, a laser projection module, a detection module, and an AR module; The 3D BIM model building module builds a 3D BIM model based on the subway station design drawings, assigns a unique identifier to each reserved steel bar and enters the steel bar parameters; The laser projection module controls the laser to position the tilt direction and end face center of the reserved steel bars according to the reserved steel bar parameters in the 3D BIM model, and calibrates the tilt direction and end face center. The detection module is used to control the start and stop of the electromagnetic detection equipment for the reserved steel bars and to transmit data. The AR module interacts with the 3D BIM model construction module and the detection module to generate detection guidelines, calculate the chiseling range of the buried reserved steel bars, control the AR eyes to synchronously display the detection guidelines and chiseling range, and correct the reserved steel bar parameters of the 3D BIM model construction module.

2. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 1, characterized in that, The unique code includes region-axis-serial number, and the rebar parameters include the diameter, length, shape, and three-dimensional coordinates of the center point of the rebar end face.

3. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 2, characterized in that, The laser projection module receives the spatial vector parameters of the steel bar axis and the center coordinates P0 of the steel bar end face transmitted by the three-dimensional BIM model construction module. The laser line laying instrument calibrates the laser point at the center of the steel bar end face and projects the inclined laser line L0 of the steel bar in combination with the spatial vector parameters. The spatial vector parameters include the elevation angle α with the horizontal plane, the horizontal deviation angle β with the station reference axis, and the length L of the steel bar. The laser projection module receives the center coordinates P2 of the rebar end face projected from the calibration point P1, and calculates the distance deviation P between P0 and P2. 偏 If P 偏 If the distance deviation threshold is not met, the center positioning accuracy of the rebar end face meets the requirements. The midpoint between P0 and P2 is taken as the final coordinates of the end face center. If P... 偏 >Distance deviation threshold, the device automatically backtracks the coordinate system transformation parameters, recalculates the projection angle, and corrects it; Two verification points are selected on L0, denoted as M1 and M2 respectively. The angles α1 and α2 between the laser line and the horizontal plane at M1 and M2, and the horizontal deflection angles β1 and β2 between the laser line and the station reference axis are measured using a three-dimensional angle meter. The laser projection module receives the above angles α1 and α2 and the horizontal deflection angles β1 and β2. If |α1-α|≦angle deviation threshold one and |α2-α|≦angle deviation threshold two, |β1-β|≦angle deviation threshold three and |β2-β|≦angle deviation threshold four, then the result is acceptable. If the deviation exceeds the threshold, the equipment automatically adjusts the pitch motor and rotation motor of the laser transmitter, reprojects the laser line and verifies it until the above angle deviations meet the thresholds.

4. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 3, characterized in that, The AR module includes a calibration submodule, a communication submodule, a SLAM submodule, an analysis submodule, a display and rendering submodule, and an interaction submodule; The calibration submodule scans the site environment using SLAM technology and matches the station construction coordinate system to ensure that the coordinates are consistent with the 3D BIM model. The communication submodule interacts and transmits data with the 3D BIM model construction module and the detection module. The SLAM submodule is used to anchor data to a virtual environment; The display rendering submodule renders the data using images and enables virtual touch and voice interaction with construction workers through the interaction module. The analysis submodule receives the end face coordinate data of the reserved steel bar and the map and location data of the SLAM submodule through the communication module. Using the center coordinate data of the steel bar end face as the theoretical position, it calculates a 1m×1m square focusing area on the same horizontal plane with the theoretical position center. The square focusing area is then divided into grids, and the coordinates and range of each grid are determined. The grid is then projected upward onto the concrete surface. The display rendering submodule renders the grid projected onto the concrete surface into the display screen of the AR glasses in a visual manner. The analysis submodule also receives the signal strength E of each node in the aforementioned grid transmitted by the detection module. 节点 The dataset {E} is obtained. 节点 The analysis submodule will also analyze the signal strength E of each node. 节点 With the pre-stored rebar threshold E in the AR module 钢筋 When E is compared, 节点 ≥E 钢筋 At that time, the three-dimensional coordinates of the grid node are anchored and recorded as a suspected node. The coordinates of the reinforcing steel below the concrete corresponding to the signal intensity of the suspected node are calculated using the "signal strength-buried depth" calibration curve, and the dataset {E} is obtained. 疑似节点 -coordinate}; The analysis submodule compares and selects the grid node M with the strongest signal strength from multiple suspected nodes, anchors the coordinates of the grid node, and renders it in a visual manner on the display screen of the AR glasses through the display rendering submodule. The analysis submodule receives the signal strength collected by the electromagnetic detection device as it rotates 360° around the strongest grid node M at a preset step size, forming a dataset {E}. 旋转 }, from which the maximum signal strength E is identified max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, determine if the fluctuation amplitude is ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar.

5. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 4, characterized in that, If the analysis submodule determines that the condition of "fluctuation amplitude ≤ 10% and no single prominent peak" is not met, the display rendering submodule will output "Rotate the electromagnetic detection device at point M around the axis perpendicular to the concrete surface until the signal strength reaches its maximum value E". max The text prompt "location"; The analysis submodule calculates the maximum signal strength E when the electromagnetic detection device is rotated to its maximum value. max The axial direction at the time of the event (i.e., the axial direction of the reserved reinforcing bar) is visualized and rendered onto the AR glasses' display screen via the display rendering submodule. The analysis submodule receives the signal strength collected in real time by the electromagnetic detection device moving along the axial direction of the reserved reinforcing bar, and obtains the dataset {E}. 轴线 The coordinates of the reinforcing steel bars below the concrete corresponding to the signal strength are calculated using the "signal strength-burial depth" calibration curve, resulting in the dataset {E}. 轴线 -coordinates}, and {E} 轴线 - Coordinates} are fitted to obtain the change curve. Analysis is performed to determine when the curve exhibits the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥ 80%) → stable background signal". The critical point A(x) at which the signal begins to attenuate is recorded. 峰 ,y 峰 ,z 峰 This point is the axial boundary point of the rebar end (the junction between the rebar end and the side wall). The analysis submodule calculates the axis perpendicular to the axis of the reinforcing bar at point A, projects it onto the concrete surface, and then renders this axis direction visually onto the AR glasses' display screen via the display rendering submodule. The analysis submodule receives electromagnetic detection equipment moving along point A in a direction perpendicular to the axis of the reinforcing bar to obtain the signal strength dataset {E}. 垂直 The data is transmitted to the analysis submodule, which identifies the strongest signal strength and calculates the peak coordinates O(x) corresponding to the strongest signal strength using the "signal strength-burial depth" calibration curve. 峰 ,y 峰 ,z 峰 And anchor the rendering display.

6. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 5, characterized in that, The analysis submodule uses the strongest grid node M or the strongest peak point O as the center to calculate a virtual ring path with multiple concentric rings on the same horizontal plane, and projects it upwards onto the concrete surface. The electromagnetic detection device then detects along the virtual ring path at a preset step size to obtain the signal strength dataset {E}. 环 }, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面 At that time, this point is a valid contour point. The coordinates corresponding to the valid contour point are calculated using the "signal strength-burial depth" calibration curve, and the dataset {E} is obtained. 有效轮廓 - Coordinates}, anchoring the coordinates corresponding to all valid contour points, the analysis submodule performs surface fitting on the valid contour points to generate the actual contour line of the rebar end face, and the analysis submodule projects the actual contour line of the rebar end face upward onto the concrete surface to generate a "virtual projection column". The display rendering submodule renders and displays the "virtual projection column". The projection area of ​​the virtual projection column on the concrete surface is the boundary of the chiseling range. The area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the end face of the steel bar in real time, and calculate the average value (buried depth). The virtual projection column constitutes the chiseling range guide. The display rendering submodule transmits the "virtual projection column" data to the interaction submodule for virtual interaction with construction personnel.

7. The BIM rapid positioning system for reserved steel bars in subway station construction as described in claim 6, characterized in that, The detection module transmits the actual end face center coordinates of a reserved rebar back to the 3D BIM model construction module. The 3D BIM model construction module, combined with the unique identifier of the reserved rebar, automatically corrects the end face center coordinates.

8. A BIM-based rapid positioning method for reserved steel bars in subway station construction, characterized in that... Based on the aforementioned BIM-based rapid positioning system for reserved reinforcing bars, the following steps are included: S1: Based on the subway station design drawings, construct a 3D BIM model in BIM software, assign a unique identifier to each reserved steel bar and enter the steel bar parameters; S2: Export the above model in an AR-compatible format, synchronize it to the AR glasses database, and integrate the electromagnetic detection device into the AR glasses; S3: Construction workers bind the steel bars to the preset positions according to the reserved steel bar parameters in the 3D BIM model, and calibrate the tilt direction and end face center to complete the concrete pouring; S4: After the concrete has initially set, construction workers carry electromagnetic detection equipment, wear AR glasses, and enter the preset position of the reserved steel bars according to the coordinate guidance of the BIM model. S5: If the reserved steel bars at the preset location are mistakenly covered by concrete, the electromagnetic detection device scanning mode is turned on according to the detection guide generated by the BIM rapid positioning system. After the information of the reserved steel bars is detected is analyzed and processed, it is anchored and rendered in the AR glasses' field of view to generate a chiseling range guide. S6: Construction workers chisel the reserved steel bars to the reserved positions according to the chiseling range guide; S7: Compare the actual location of the detected reserved steel bars with the location parameters in the BIM model, calculate the deviation value and correct it.

9. The BIM-based rapid positioning method for reserved steel bars in subway station construction as described in claim 8, characterized in that, Step S2, integrating the electromagnetic detection device into the AR glasses, includes the following sub-steps: S21. Combine the concrete strength parameters to preset the electromagnetic field attenuation coefficient of the electromagnetic detection equipment to ensure that the detection accuracy of the steel bars after penetrating the concrete is ≤ ±5mm, and eliminate the interference of concrete strength on the signal. S22. Select an electromagnetic detection device with low-frequency electromagnetic field emission and secondary magnetic field reception functions, and connect it to the AR glasses via Bluetooth. S23. The electromagnetic detection equipment is calibrated using steel bars at known locations and depths. This involves having the electromagnetic detection equipment scan the steel bars at the known locations and depths, recording the difference between the detection signal and the actual location, and the AR module's built-in system automatically adjusting the signal conversion parameters. Subsequent detections will be corrected accordingly to ensure accurate results.

10. The BIM-based rapid positioning method for reserved steel bars in subway station construction as described in claim 9, characterized in that, Step S5 includes the following sub-steps: S51. Coordinate calibration: Before starting the scanning mode, the AR glasses scan the site environment using SLAM technology, match the station construction coordinate system, ensure that the coordinates are of the same origin as the 3D BIM model, and calibrate the electromagnetic detection equipment with the station construction coordinate system. S52. Peak Threshold Calibration and "Signal Strength-Buried Depth" Calibration Curve Fitting: Various specifications of reinforcing bars, consistent with on-site construction, were selected as calibration samples. An adjustable-thickness concrete sheet was placed over each end of the reinforcing bar and anchored at the end center. The electromagnetic detection equipment was placed against the projection point on the surface of the concrete sample block directly above the end center. Using this point as the center, the surrounding area was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain the signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 端面 ; Multiple specifications of steel bars, consistent with those used in on-site construction, were selected as calibration samples. A thin, adjustable-thickness concrete sheet was placed over the sidewall of each sample. An electromagnetic detection device was positioned directly above the concrete sample surface, and the projection area of ​​the sidewall onto the concrete sample surface was divided into a grid. Scanning was performed at fixed intervals along the grid to obtain signal strength data for each grid node. The lower limit of the signal strength data was set as the end-face threshold E. 钢筋 ; The "signal strength-buried depth" calibration curve was established through preliminary tests simulating on-site construction conditions: Concrete test blocks with the same strength grade and aggregate ratio as the actual construction were selected, and reinforcing bars of the same specifications (diameter and material) as the pre-reserved reinforcing bars were embedded. The positions of the reinforcing bars were fixed according to a preset buried depth gradient (e.g., 5mm, 10mm, 15mm…100mm, covering common erroneous buried depths), ensuring that the vertical distance between the center of the reinforcing bar and the concrete surface accurately corresponded to each buried depth value. Then, the electromagnetic sensor to be calibrated was placed directly above the corresponding reinforcing bar on the test block surface, and the device was turned on to collect stable signal strength values ​​at each buried depth. Each buried depth was repeatedly sampled three times, and the average value was taken to reduce errors. Finally, a smooth curve was generated by fitting data (e.g., linear fitting, polynomial fitting) with the buried depth value on the x-axis and the corresponding average signal strength on the y-axis. After removing outlier data points and marking confidence intervals, the calibration curves for different signal strengths and corresponding buried depths were obtained, ensuring matching with the actual on-site detection environment. The analysis submodule called this curve and associated it with the station construction coordinate system for calibration, calculating the buried depth z based on the measured signal strength. 深 Because the sensor is in close contact with the concrete surface, its three-dimensional coordinates (x, y, z) are... 表 ,y 表 ,z 表 Subtract the embedment depth to obtain the actual coordinates (x) of the reinforcing bar. 表 ,y 表 ,z 表 -z 深 ), and lightly bound to the corresponding signal; S53. Initial Grid Scan Confirms Reinforcement Presence: Construction workers wear AR glasses. The system's AR module uses green crosshairs to anchor the theoretical positions of the reinforcing bars in the 3D BIM model. The system's AR module calculates a 1m×1m square focusing area centered on the theoretical position on the same horizontal plane and divides it into grids. The coordinates and range of each grid are determined, and the grid is projected upwards onto the concrete surface. The grid projected onto the concrete surface is then rendered visually onto the AR glasses' display screen: 1) The display screen divides the area into a uniform 20mm×20mm grid (50×50 nodes in total); 2) Construction workers hold sensors and move them at a constant speed along the grid nodes (moving speed ≤5cm / s to avoid missed signal detection). The bottom surface of the sensor is in close contact with the concrete surface, and the signal strength E of each node is recorded in real time. 节点 3) The system's AR module automatically generates a signal strength heatmap and automatically determines when a certain E 节点 ≥E 钢筋 When the grid node is identified as a suspected node, its coordinates are calculated and anchored. If no suspected area is detected, the scanning range can be expanded to 2m×2m and the operation repeated. S54. The system's AR module compares and selects the grid node M with the strongest signal strength from multiple suspected nodes. This point is projected onto the concrete surface. Construction personnel hold an electromagnetic detection device and slowly rotate it 360° around an axis perpendicular to the concrete surface, with rotation increments of 5°, collecting the signal strength dataset {E} throughout the process. 旋转 The system's AR module identifies the maximum signal strength E from this. max Minimum signal strength E min and average value E avg To calculate the fluctuation range, the formula is: Fluctuation Range = (E max -E min ) / E avg ×100%, if the fluctuation amplitude is judged to be ≤10% and there is no single prominent peak, that is, the signal strength change within a continuous 10° rotation range is ≤3%E. avg The strongest mesh node M is determined to be above the end face of the buried rebar, and the mesh node M is marked and visualized for recognition. S55. If condition S54 is not met, according to the system prompts, the construction personnel should rotate the electromagnetic detection equipment around an axis perpendicular to the concrete surface until the signal strength reaches its maximum value E. max At this location, the axial direction of the electromagnetic detection equipment (the central axis of symmetry of the equipment) is the axial direction of the reinforcing bar. The AR module projects this axial direction onto the concrete surface. Then, following the projection axis guidance generated by the system's AR module, the construction personnel hold the electromagnetic detection equipment and move it along both sides of this projection axis, with a scanning speed of 3cm / s and a step size of 2mm. The signal strength and corresponding coordinates are recorded in real time, resulting in a signal strength-coordinate dataset {E}. 轴线 -coordinates}, the system AR module will use the above dataset {E} 轴线 - Coordinates} are fitted to obtain the change curve. When the system analysis curve exhibits the characteristics of "stable peak range → rapid attenuation (attenuation amplitude ≥ 80%) → stable background signal", the system records the critical point A(x) at which the signal begins to attenuate. 峰 ,y 峰 ,z 峰 The system marks and renders the point, which is the axial boundary point of the rebar end (the junction between the rebar end and the side wall). To verify the accuracy, the construction personnel scan in reverse once according to the system prompts. If the coordinate deviation of point A in the two detections is ≤3mm, the average value is taken as the final boundary point, and the coordinates of the point are recorded. S56. Following the projection axis guidance from the AR glasses, construction personnel move the electromagnetic detection device along point A in a direction perpendicular to the axis of the reinforcing bar, with a scanning range of ±100mm and a movement step of 1mm, ensuring complete coverage of the end section. The signal strength dataset {E} is then obtained. 垂直 The system's AR module automatically identifies the strongest peak point O(x) from it. 峰 ,y 峰 ,z 峰 The image is then anchored and rendered to show that the point is located at the end face of the buried rebar. S57. Using the strongest grid node M from S54 or the strongest peak point O from step S56 as the center, the AR module sets up multiple virtual ring paths and projects them onto the concrete surface. The distance between adjacent rings is constant. The electromagnetic detection device scans each ring path sequentially from the inside out, with a rotation step of 3° and a scanning speed of 5° / s, to obtain the signal strength dataset {E}. 环 }, and compared with the pre-set end face threshold E of the reserved steel bar in the AR module. 端面 Comparison, when E of a certain collection point 环 ≧E 端面 At that time, mark the point as a valid contour point, calculate the corresponding three-dimensional coordinates, and obtain the dataset {E}. 有效轮廓 - Coordinates}, anchor all valid contour points and render the display; S58. After scanning, the AR module automatically removes abnormal contour points: Abnormal contour points include: 1) Points with signal fluctuation amplitude > 8% (excluding interference from concrete impurities); 2) Points with a deviation from the 3D BIM model section contour > 5mm (excluding interference from adjacent metals); 3) The AR module performs surface fitting on the remaining valid contour points to generate the actual contour line of the steel bar end face, with a fitting error ≤ ±2mm. S59. The AR module projects the fitted actual outline of the rebar end face upwards onto the concrete surface, generating a "virtual projection column" which is then rendered and displayed in the AR glasses. The projection area of ​​this virtual projection column on the concrete surface is the boundary of the chiseling range, and the area inside the virtual projection column is the core chiseling area. The AR glasses display the coordinate range of each point in the projection area on the concrete surface in real time, and display the actual coverage thickness from each projection point on the upper surface of the virtual projection column to the rebar end face in real time, calculating the average value (embedding depth). This virtual projection column serves as a guide for the chiseling range for construction workers; the AR module enables virtual interaction between the "virtual projection column" data and the construction workers. S60. When the construction workers excavate the reserved steel bar, the SLAM submodule will detect the actual end face center coordinates of the reserved steel bar and transmit them back to the 3D BIM model construction module. The 3D BIM model construction module will automatically correct the end face center coordinates by combining the unique identity of the reserved steel bar.

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