A mobile factory box girder formwork intelligent positioning method based on laser targeting

Abstract

The application discloses a kind of mobile factory box girder template intelligent positioning method based on laser target, including establishing BIM model in BIM software, and inputting the design absolute coordinates of multiple measurement control points on each corresponding template;After mobile factory moves template to set position, the design absolute coordinates of multiple measurement control points on corresponding template are recalled in BIM software;The offset of multiple directions of the current each measurement control point of template and the inclination angle of template are obtained by the sensor arranged on template;The offset of multiple directions of each measurement control point and the inclination angle of template are solved to obtain the actual absolute coordinates of each measurement control point, and compared with the design absolute coordinates of corresponding measurement control point, obtain three-dimensional deviation;Based on three-dimensional deviation value, drive hydraulic system to adjust template, until deviation is zero.The application realizes that template is positioned without measurement, automatic calculation difference, automatic positioning, completely replaces artificial total station instrument guard adjustment.

Description

Technical Field

[0001] This invention relates to the field of mobile factory construction technology for cast-in-place box girders. More specifically, this invention relates to an intelligent positioning method for box girder formwork in a mobile factory based on laser targets. Background Technology

[0002] Currently, in the construction of mobile factories for cast-in-place box girders in railways, formwork measurement mainly employs a manual total station method, measuring point by point. This requires setting prisms at both ends of the formwork, collecting three-dimensional coordinates with the total station, comparing them with design values, calculating the horizontal position and elevation deviations, and then manually adjusting the hydraulic system to millimeter-level precision. Some projects use laser leveling instruments to assist in elevation measurement, but manual reading, recording, and adjustment are still necessary. Because mobile factory formwork needs frequent relocation and reuse, traditional measurement methods require surveyors to be on-site throughout the process and repeatedly verify the measurements, which cannot match the pace of assembly-line construction. Overall, the automation level is low, time-consuming, and labor costs are high. The main problems include: 1. Extremely low measurement efficiency: Manual measurement, alignment and adjustment of a single box girder formwork takes more than 40 minutes and requires 2-3 people to operate, which seriously restricts the continuous construction progress of the mobile factory; 2. Insufficient coverage of measurement benchmarks and multiple accuracy transfer links: Due to project cost and overall route planning constraints, the project control network and densified control points are usually deployed uniformly, making it impossible to set up dedicated measurement control points for each box girder. Some construction sections are limited by terrain conditions, and there are even no available direct control points. In actual construction, multiple point transfers and measurement transfers are required before formwork positioning can be carried out. The accuracy gradually decreases during the transfer process, resulting in unstable formwork positioning accuracy and making it difficult to control the box girder alignment. 3. Inability to achieve automatic adjustment: The measurement data is disconnected from the hydraulic adjustment system, and adjustments can only be made through manual feedback of deviations and manual commands, which cannot form a closed-loop control; 4. High labor intensity and poor environmental adaptability: In field construction, strong light and dust environments, manual measurement is difficult and unsafe, making it difficult to achieve standardized operations around the clock.

[0003] To address the aforementioned issues, this application proposes a three-dimensional automatic positioning method based on ground-based benchmark targets and laser displacement sensing, namely, an intelligent positioning method for mobile factory box girder templates based on laser targets. This method fundamentally solves the industry problems of slow positioning, poor accuracy, and lack of automation in mobile factory templates. Summary of the Invention

[0004] One objective of this invention is to provide an intelligent positioning method for box girder formwork in mobile factories based on laser targets, which enables unmanned measurement, automatic difference calculation, and automatic positioning after the formwork is in place, completely replacing manual total station monitoring and adjustment, and fundamentally solving the industry problems of slow, inaccurate, and non-automatic positioning of mobile factory formwork.

[0005] To address the aforementioned technical problems, this invention provides an intelligent positioning method for mobile factory box girder formwork based on a laser target, comprising the following steps: Step 1: Create a complete digital BIM model of the box girder and mobile factory in BIM software, and input the absolute coordinates of multiple measurement control points on each corresponding template. Step 2: After moving the template to the set position via the mobile factory, retrieve the design absolute coordinates of multiple measurement control points on the corresponding template in the BIM software; Step 3: Use the sensors installed on the template to obtain the offset of each measurement control point in multiple directions and the tilt angle of the template. Step 4: Calculate the offsets of each measurement control point in multiple directions and the tilt angle of the template to obtain the actual absolute coordinates of each measurement control point, and compare them with the design absolute coordinates of the corresponding measurement control points to obtain the three-dimensional deviation. Step 5: Based on the above three-dimensional deviation values, drive the hydraulic system to adjust the template until the deviation returns to zero.

[0006] Preferably, an inclination sensor is installed on the template to obtain the inclination angle of the template. A dual-axis laser displacement sensor is installed on the template for each measurement control point. At the same time, a corresponding ground target is pre-embedded on the ground for each measurement control point, and the geodetic coordinates of the center of each ground target are measured. The geodetic coordinates are then input into the BIM model and bound to the design target point position in the BIM model. This ensures that the target point in the BIM model has absolute coordinate values ​​(X0, Y0, Z0) that are completely consistent with the actual site. The actual absolute coordinates of each measurement control point are calculated by using the absolute coordinate values ​​of the ground targets, the offsets of each measurement control point in multiple directions obtained by the sensors, and the inclination angle of the template.

[0007] Preferably, the coordinate transformation solution method for obtaining the actual absolute coordinates of the template through sensor data is as follows: The calculation includes: First, the displacement deviations ΔX and ΔY of a certain measurement control point on the template relative to the ground target in the X and Y directions are obtained using a dual-axis laser displacement sensor; Second, the real-time absolute plane coordinates (X1, Y1) of the measurement control point on the template are calculated, where X1 = X0 + ΔX + Cx; Y1 = Y0 + ΔY + Cy; where (X0, Y0) are the known absolute coordinates of the ground target; Cx and Cy are the fixed installation deviations in the X and Y directions between the sensor installation point and the template measurement control point, respectively. This also includes elevation coordinate calculation: First, the vertical distance D from the laser displacement sensor to the ground target is measured synchronously; the tilt sensor measures the tilt angles α and β of the template in the longitudinal and transverse directions; second, the real-time absolute elevation of the control point on the template is calculated as Z1 = Z0 + D + ΔZ(α, β); where Z0 is the known absolute elevation of the ground target; ΔZ(α, β) is a value derived from the current tilt angle and the elevation deviation between the sensor and the target. Cz is the fixed installation deviation value in the Z direction between the sensor mounting point and the template measurement control point.

[0008] Preferably, multiple measurement control points are installed at the corresponding design positions on the wing plates, side molds, and end molds of the template. The dual-axis laser displacement sensor is vertically aligned with the ground target pre-embedded in the ground. The dual-axis laser displacement sensor is rigidly connected to the template and moves synchronously with the template. The tilt sensor is set at the center of the template. The sensor is connected to the data acquisition and control box on the side of the template to realize real-time data acquisition and transmission.

[0009] Preferably, in step one, the establishment of the BIM model benchmark database is as follows: First, a dataset is created using spans as the index. Specifically, based on the starting position of the first span, and according to the fixed span length, a unique number is defined for each span in the BIM model as the Nth span, and an independent data record is created for each span. Secondly, for each span, the basic information is pre-calculated and entered into the BIM software system to form a three-dimensional design benchmark dataset for that span. The basic information includes: ground benchmark coordinates, that is, the absolute coordinates (X0-L, Y0-L, Z0-L) and (X0-R, Y0-R, Z0-R) of the permanent ground targets on the left and right sides within each span; and template design state values, that is, when the template is accurately positioned in the span, the design absolute coordinates (X, Y, Z) and design attitude angles (α, β) of each measurement control point on it.

[0010] Preferably, the method for retrieving data from the BIM system is as follows: First, after the mobile factory carrying the template moves to the target span and is initially positioned, the number N corresponding to the target span is selected on the system's control interface, and an indexing command is issued. Secondly, the system uses the Nth span corresponding to the target span as a unique index to automatically retrieve and load the entire benchmark dataset of the Nth span in the BIM model benchmark database. Finally, the system uses the entire reference dataset of the Nth span, including the absolute coordinates of the ground target, the design absolute coordinates and design attitude angles of each measurement control point of the template, as a reference to directly start the measurement, comparison, and adjustment closed-loop control in steps three to five, driving the template to adjust to the design position of the Nth span.

[0011] Preferably, the system is equipped with a convergence threshold parameter library, which can be selected and matched autonomously according to the specific requirements of the project. During the real-time adjustment process, when the system detects that the deviation of all measurement control points reaches the preset threshold range at the same time, it automatically determines that the positioning is complete, locks the hydraulic system and sends a positioning signal.

[0012] Preferably, when the mobile factory carries multiple templates simultaneously, the templates achieve collaborative positioning. The specific method is as follows: First, using the first template as the absolute reference, after the first template is accurately positioned, record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the first template; Next, move the adjacent second template to the design position, and follow steps three to five to measure, compare, and adjust the closed-loop control to position the second template within the set deviation range. Record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the second template. Next, the actual distance between the front end of the second template and the rear end of the first template is measured using a laser rangefinder; at the same time, the height difference between the two templates is calculated based on the corner elevation coordinates of the first and second templates; and the axial deviation between the two templates is calculated based on the plane coordinates of the centerline measuring points of the first and second templates. Then, the theoretical design values ​​of the first and second templates are obtained from the BIM model, the theoretical deviation is calculated, and the relative positioning error value is calculated by comparing it with the actual distance, height difference and axis deviation between the two templates as measured and calculated above, and it is determined whether the relative positioning error value exceeds the preset threshold. Finally, if the preset threshold is exceeded, a collaborative adjustment mode is activated until the relative positioning error value is within the preset threshold; if the preset threshold is not exceeded, the positioning of the adjacent third template and subsequent templates is completed in sequence, with each new template based on the previous positioned template.

[0013] Preferably, the collaborative adjustment mode calculates the compensation adjustment amount and then sends the calculated compensation adjustment amount to the hydraulic system to drive the template to adjust. The actual spacing compensation adjustment amount is the actual spacing relative positioning error value × w, where w is the adjustment weight coefficient of the second template, set to 0.6-0.9. The actual height difference and axis compensation adjustment amount are the calculated actual height difference and axis relative positioning error values, adjusted until the relative positioning error value does not exceed the preset threshold.

[0014] The present invention has at least the following beneficial effects: 1. Achieve truly unmanned measurement: No need for manual setup of the total station, manual reading, or manual command and adjustment; one operator can remotely monitor, greatly saving manpower. 2. Significantly improved positioning speed: The measurement and adjustment time for a single span template has been reduced from 40 minutes to less than 5 minutes, increasing efficiency several times over and fully adapting to the construction rhythm of a mobile factory assembly line; 3. Stable and reliable positioning accuracy: The laser sensor has a measurement accuracy of ±0.1mm, and the template positioning deviation is controlled within the requirements of the construction specifications; 4. Forming a closed-loop automatic control system: Measurement, calculation, and adjustment are completed in an integrated manner, without manual intervention, avoiding human error and reducing rework rate; 5. Strong environmental adaptability and reusability: The ground target is buried once and used for a long time. The sensor and template are integrated into one unit and can be reused repeatedly with the template. It is suitable for complex construction environments such as strong light and dust.

[0015] Other advantages, objectives and features of the present invention will be apparent in part from the following description, and in part from the understanding of those skilled in the art through study and practice of the invention. Detailed Implementation

[0016] To better understand the purpose, structure, and function of this invention, the following detailed description is provided in conjunction with embodiments, so that those skilled in the art can implement it based on the description.

[0017] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0018] This invention provides an intelligent positioning method for box girder formwork in a mobile factory based on a laser target, comprising the following steps: Step 1: Create a complete digital BIM model of the box girder and mobile factory in BIM software, and input the absolute coordinates of multiple measurement control points on each corresponding template. Before construction, a complete digital model of the box girder and mobile factory was created in BIM software. The system adopts a benchmark data management system based on the construction span as the basic unit. The BIM model benchmark database was established as follows: First, a dataset is created using spans as the index. Specifically, based on the starting position of the first span, and according to the fixed span length, a unique number is defined for each span in the BIM model as the Nth span (e.g., the 1st span, the 2nd span, the 3rd span, etc.), and an independent data record is created for each span. Secondly, for each span, the basic information is pre-calculated and entered into the BIM software system to form a three-dimensional design benchmark dataset for that span. The basic information includes: ground benchmark coordinates, that is, the absolute coordinates (X0-L, Y0-L, Z0-L) and (X0-R, Y0-R, Z0-R) of the permanent ground targets on the left and right sides within each span, forming the absolute coordinate values ​​(X0, Y0, Z0) of the ground targets; and template design status values, that is, when the template is accurately positioned in the span, the design absolute coordinates (X, Y, Z) and design attitude angles (α, β) of each measurement control point on it.

[0019] Step 2: After moving the template to the set position via the mobile factory, retrieve the design absolute coordinates of multiple measurement control points on the corresponding template in the BIM software; The specific method for retrieving data from a BIM system is as follows: First, once the mobile factory carrying the template has moved to the target span and is initially in place, the operator selects the number corresponding to the target span on the system's control interface, such as the Nth span, or the mobile factory's span sequence control system automatically issues a command to locate the Nth span and issues an index command. Secondly, the system uses the Nth span corresponding to the target span as a unique index to automatically retrieve and load the entire benchmark dataset of the Nth span in the BIM model benchmark database. Finally, the system uses the entire reference dataset of the Nth span, including the absolute coordinates of the ground target, the design absolute coordinates and design attitude angles of each measurement control point of the template, as a reference to directly start the measurement, comparison, and adjustment closed-loop control in steps three to five, driving the template to adjust to the design position of the Nth span, and the template is precisely locked from the rough position to the design position of this span.

[0020] Step 3: Use the sensors installed on the template to obtain the offset of each measurement control point in multiple directions and the tilt angle of the template. On the corresponding measurement sections on both sides of the mobile factory's walking track, bidirectional positioning targets for the X and Y axes are pre-embedded. These targets are made of highly reflective material and fixed to concrete bases, forming permanent ground measurement benchmarks. The target coordinates are pre-entered into the BIM model as the design's three-dimensional coordinate benchmark. At the construction site, a high-precision total station is used to measure the geodetic coordinates (X0, Y0, Z0) of the center of each pre-embedded ground target. These coordinates are unique and absolute. These precise (X0, Y0, Z0) values ​​are then entered into the BIM software and bound to the corresponding design locations in the model. At this point, the target points in the BIM model possess absolute coordinate values ​​completely consistent with those on-site.

[0021] Tilt sensors are installed on the template to obtain its tilt angle. A dual-axis laser displacement sensor is installed on the template for each measurement control point. At the same time, ground targets are pre-embedded on the ground for each measurement control point, and the geodetic coordinates of the center of each ground target are measured. The geodetic coordinates are then input into the BIM model and bound to the design target point position in the BIM model. This ensures that the target points in the BIM model have absolute coordinate values ​​(X0, Y0, Z0) that are completely consistent with the actual site. The actual absolute coordinates of each measurement control point are calculated by using the absolute coordinate values ​​of the ground targets, the offsets of each measurement control point in multiple directions obtained by the sensors, and the tilt angle of the template.

[0022] Multiple measurement control points are installed at the corresponding design positions on the wing plates, side molds, and end molds of the mobile factory's formwork template. Dual-axis laser displacement sensors and high-precision tilt sensors are fixedly installed. The dual-axis laser displacement sensors are vertically aligned with the ground targets embedded in the ground. The dual-axis laser displacement sensors are rigidly connected to the template and move synchronously with the template. The tilt sensor is set at the center of the template. The sensors are connected to the data acquisition and control box on the side of the template through cables to realize real-time data acquisition and transmission.

[0023] Step 4: Calculate the offsets of each measurement control point in multiple directions and the tilt angle of the template to obtain the actual absolute coordinates of each measurement control point, and compare them with the design absolute coordinates of the corresponding measurement control points to obtain the three-dimensional deviation. After the template is moved into position, the system automatically activates the laser displacement sensor to perform non-contact measurement on the target. The offset of the laser displacement sensor's installation position relative to a certain measurement control point on the template (such as the side template edge point) is precisely calibrated in advance. The dual-axis laser displacement sensor illuminates the ground target perpendicularly and directly reads the displacement deviation ΔX and ΔY of the template relative to the target at that point in the X and Y directions (i.e., the sensor reading itself is two-dimensional).

[0024] The system obtains the coordinate transformation of the template's actual absolute coordinates through sensor data. It then compares the measured 3D data with the BIM design baseline in real time, automatically calculating the comprehensive deviation values ​​of planar position, axis, and elevation. The real-time calculation method is as follows: The calculation includes the following: First, a dual-axis laser displacement sensor is used to obtain the displacement deviations ΔX and ΔY of a corresponding measurement control point on the template relative to a ground target in the X and Y directions. Second, the real-time absolute plane coordinates (X1, Y1) of the measurement control point on the template are calculated, where X1 = X0 + ΔX + Cx; Y1 = Y0 + ΔY + Cy. Here, X0 and Y0 are the known absolute coordinates of the ground target; Cx and Cy are the fixed installation deviations in the X and Y directions between the sensor installation point and the template measurement control point, respectively, and are fixed calibration constants (determined during integrated installation). This also includes elevation coordinate calculation: First, the vertical distance D from the laser displacement sensor to the ground target is measured synchronously; the tilt sensor measures the tilt angles α and β of the template in the longitudinal and transverse directions; second, the real-time absolute elevation of the control point on the template is calculated as Z1 = Z0 + D + ΔZ(α, β); where Z0 is the known absolute elevation coordinate of the ground target; ΔZ(α, β) is a value derived from the current tilt angle and the elevation deviation between the sensor and the target. Cz is the fixed installation deviation value in the Z direction between the sensor mounting point and the template measurement control point.

[0025] The system compares the current absolute coordinates (X1, Y1, Z1) of the template calculated in real time with the design absolute coordinates (X0, Y0, Z0) of the point in the BIM model to obtain the three-dimensional deviation, and drives the hydraulic system to adjust until the deviation returns to zero.

[0026] Step 5: Based on the above three-dimensional deviation values, drive the hydraulic system to adjust the template until the deviation returns to zero.

[0027] The system converts the deviation value into control commands, which are directly output to the hydraulic adjustment system of the mobile factory. This drives the template to perform millimeter-level automatic translation, lifting, and correction until the measured coordinates completely match the BIM design coordinates. After the adjustment is in place, the system automatically locks and sends a positioning signal, completing the entire process of unmanned measurement and positioning.

[0028] The system forms a real-time closed loop based on a multivariable PID control algorithm. The control parameters are tuned on-site during system commissioning to achieve a fast and stable dynamic response.

[0029] During the adjustment process, the system executes a closed-loop process of measurement → calculation → control → output at high frequency, driving the hydraulic system to achieve millimeter-level fine adjustment of the template.

[0030] Convergence Determination: The system has a configurable convergence threshold parameter library. The thresholds are set according to design and construction acceptance specifications (such as allowable deviations for the installation of cast-in-place beam formwork in railways). Users can select and match the thresholds according to the specific requirements of the project. During real-time adjustment, when the system detects that the deviation of all control points simultaneously reaches the preset threshold range, it automatically determines that the positioning is complete, locks the hydraulic system, and sends a positioning signal. The entire process requires no manual intervention.

[0031] When a mobile factory simultaneously carries multiple templates, the templates achieve collaborative positioning. The specific method is as follows: First, using the first template as the absolute reference, after the first template is accurately positioned, record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the first template; Next, move the adjacent second template to the design position, and follow steps three to five to measure, compare, and adjust the closed-loop control to position the second template within the set deviation range. Record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the second template. Next, the actual distance between the front end of the second template and the rear end of the first template is measured using a laser rangefinder; at the same time, the height difference between the two templates is calculated based on the corner elevation coordinates of the first and second templates; and the axial deviation between the two templates is calculated based on the plane coordinates of the centerline measuring points of the first and second templates. Then, the theoretical design values ​​of the first and second templates are obtained from the BIM model, the theoretical deviation is calculated, and the relative positioning error value is calculated by comparing it with the actual distance, height difference and axis deviation between the two templates as measured and calculated above, and it is determined whether the relative positioning error value exceeds the preset threshold. Finally, if the preset threshold is exceeded, a collaborative adjustment mode is activated until the relative positioning error value is within the preset threshold; if the preset threshold is not exceeded, the positioning of the adjacent third template and subsequent templates is completed in sequence, with each new template based on the previous positioned template.

[0032] The collaborative adjustment mode calculates the compensation adjustment amount and then sends it to the hydraulic system to drive the template movement for adjustment. The actual spacing compensation adjustment amount is the actual spacing relative positioning error value × w, where w is the adjustment weight coefficient of the second template, set to 0.6-0.9, generally 0.7. The actual height difference and axis compensation adjustment amounts are the calculated actual height difference and axis relative positioning error values, adjusted until the relative positioning error value does not exceed the preset threshold. The spacing error is jointly determined by the positions of the two templates and is shared by both templates because a weight allocation is applied to the second template. The height difference and axis error are mainly errors caused by the position deviation of the second template and are entirely adjusted by the second template.

[0033] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention, and other modifications can be easily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for intelligent positioning of a mobile factory box girder formwork based on laser targeting, characterized in that, Includes the following steps: Step 1: Create a complete digital BIM model of the box girder and mobile factory in BIM software, and input the absolute coordinates of multiple measurement control points on each corresponding template. Step 2: After moving the template to the set position via the mobile factory, retrieve the design absolute coordinates of multiple measurement control points on the corresponding template in the BIM software; Step 3: Use the sensors installed on the template to obtain the offset of each measurement control point in multiple directions and the tilt angle of the template. Step 4: Calculate the offsets of each measurement control point in multiple directions and the tilt angle of the template to obtain the actual absolute coordinates of each measurement control point, and compare them with the design absolute coordinates of the corresponding measurement control points to obtain the three-dimensional deviation. Step 5: Based on the above three-dimensional deviation values, drive the hydraulic system to adjust the template until the deviation returns to zero.

2. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 1, characterized in that, Tilt sensors are installed on the template to obtain its tilt angle. A dual-axis laser displacement sensor is installed on the template for each measurement control point. At the same time, ground targets are pre-embedded on the ground for each measurement control point, and the geodetic coordinates of the center of each ground target are measured. The geodetic coordinates are then input into the BIM model and bound to the design target point position in the BIM model. This ensures that the target points in the BIM model have absolute coordinate values ​​(X0, Y0, Z0) that are completely consistent with the actual site. The actual absolute coordinates of each measurement control point are calculated by using the absolute coordinate values ​​of the ground targets, the offsets of each measurement control point in multiple directions obtained by the sensors, and the tilt angle of the template.

3. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 2, characterized in that, The coordinate transformation solution method for obtaining the actual absolute coordinates of the template from sensor data is as follows: The calculation includes: First, the displacement deviations ΔX and ΔY of a certain measurement control point on the template relative to the ground target in the X and Y directions are obtained using a dual-axis laser displacement sensor; Second, the real-time absolute plane coordinates (X1, Y1) of the measurement control point on the template are calculated, where X1 = X0 + ΔX + Cx; Y1 = Y0 + ΔY + Cy; where (X0, Y0) are the known absolute coordinates of the ground target; Cx and Cy are the fixed installation deviations in the X and Y directions between the sensor installation point and the template measurement control point, respectively. This also includes elevation coordinate calculation: First, the vertical distance D from the laser displacement sensor to the ground target is measured synchronously; the tilt sensor measures the tilt angles α and β of the template in the longitudinal and transverse directions; second, the real-time absolute elevation of the control point on the template is calculated as Z1 = Z0 + D + ΔZ(α, β); where Z0 is the known absolute elevation of the ground target; ΔZ(α, β) is a value derived from the current tilt angle and the elevation deviation between the sensor and the target. Cz is the fixed installation deviation value in the Z direction between the sensor mounting point and the template measurement control point.

4. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 2, characterized in that, Multiple measurement control points are installed at the corresponding design positions on the wing plates, side molds, and end molds of the template. The dual-axis laser displacement sensor is vertically aligned with the ground target pre-embedded in the ground. The dual-axis laser displacement sensor is rigidly connected to the template and moves synchronously with the template. The tilt sensor is set at the center of the template. The sensor is connected to the data acquisition and control box on the side of the template to realize real-time data acquisition and transmission.

5. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 2, characterized in that, In step one, the establishment of the BIM model benchmark database is as follows: First, a dataset is created using spans as the index. Specifically, based on the starting position of the first span, and according to the fixed span length, a unique number is defined for each span in the BIM model as the Nth span, and an independent data record is created for each span. Secondly, for each span, the basic information is pre-calculated and entered into the BIM software system to form a three-dimensional design benchmark dataset for that span. The basic information includes: ground benchmark coordinates, that is, the absolute coordinates (X0-L, Y0-L, Z0-L) and (X0-R, Y0-R, Z0-R) of the permanent ground targets on the left and right sides within each span; and template design state values, that is, when the template is accurately positioned in the span, the design absolute coordinates (X, Y, Z) and design attitude angles (α, β) of each measurement control point on it.

6. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 5, characterized in that, The specific method for retrieving data from a BIM system is as follows: First, after the mobile factory carrying the template moves to the target span and is initially positioned, the number N corresponding to the target span is selected on the system's control interface, and an indexing command is issued. Secondly, the system uses the Nth span corresponding to the target span as a unique index to automatically retrieve and load the entire benchmark dataset of the Nth span in the BIM model benchmark database. Finally, the system uses the entire reference dataset of the Nth span, including the absolute coordinates of the ground target, the design absolute coordinates and design attitude angles of each measurement control point of the template, as a reference to directly start the measurement, comparison, and adjustment closed-loop control in steps three to five, driving the template to adjust to the design position of the Nth span.

7. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 1, characterized in that, The system is equipped with a convergence threshold parameter library, which can be selected and matched autonomously according to the specific requirements of the project. During the real-time adjustment process, when the system detects that the deviation of all measurement control points reaches the preset threshold range at the same time, it automatically determines that the positioning is complete, locks the hydraulic system and sends a positioning signal.

8. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 6, characterized in that, When a mobile factory simultaneously carries multiple templates, the templates achieve collaborative positioning. The specific method is as follows: First, using the first template as the absolute reference, after the first template is accurately positioned, record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the first template; Next, move the adjacent second template to the design position, and follow steps three to five to measure, compare, and adjust the closed-loop control to position the second template within the set deviation range. Record the final actual absolute coordinates of multiple measurement control points at the front and rear ends of the second template. Next, the actual distance between the front end of the second template and the rear end of the first template is measured using a laser rangefinder; at the same time, the height difference between the two templates is calculated based on the corner elevation coordinates of the first and second templates; and the axial deviation between the two templates is calculated based on the plane coordinates of the centerline measuring points of the first and second templates. Then, the theoretical design values ​​of the first and second templates are obtained from the BIM model, the theoretical deviation is calculated, and the relative positioning error value is calculated by comparing it with the actual distance, height difference and axis deviation between the two templates as measured and calculated above, and it is determined whether the relative positioning error value exceeds the preset threshold. Finally, if the preset threshold is exceeded, a collaborative adjustment mode is activated until the relative positioning error value is within the preset threshold. If the preset threshold is not exceeded, the positioning of the adjacent third template and subsequent templates will be completed in sequence, with each new template based on the previously positioned template.

9. The intelligent positioning method for mobile factory box girder formwork based on laser target as described in claim 8, characterized in that, The collaborative adjustment mode calculates the compensation adjustment amount and then sends the calculated compensation adjustment amount to the hydraulic system to drive the template to adjust. The actual spacing compensation adjustment amount is the actual spacing relative positioning error value × w, where w is the adjustment weight coefficient of the second template, set to 0.6-0.

9. The actual height difference and axis compensation adjustment amount are the calculated actual height difference and axis relative positioning error values, adjusted until the relative positioning error value does not exceed the preset threshold.