A method for measuring the length of stayed cables based on three-dimensional laser point clouds

Abstract

The present invention discloses a method for measuring the length of a stay cable based on a three-dimensional laser point cloud. This method uses high-precision laser scanning to obtain a three-dimensional point cloud model of the stay cable, enabling automatic identification and accurate calculation of the cable length. First, a three-dimensional laser scanner is used to scan the cable surface of the cable-stayed bridge to obtain a point cloud model of a single stay cable. The point cloud model of the stay cable is then segmented into multiple point cloud segments. The point cloud segments are then coordinate-converted, and the center coordinates of the point cloud segments are calculated. The cable length of the three-dimensional laser point cloud portion is then determined based on the center coordinates of all the point cloud segments. Finally, the anchorage length of the stay cable within the beam and tower is obtained based on the design data, and the cable length is calculated, enabling rapid and efficient measurement of the stay cable length.

Description

Technical Field

[0001] The present invention relates to the field of bridge engineering measurement, and in particular to a method for measuring the length of a stay cable based on three-dimensional laser point clouds. Background Art

[0002] With the rapid development of transportation construction, my country has built a large number of long-span cable-stayed bridges. Cable-stayed bridges, with several symmetrically distributed cables, present a relatively complex load-bearing structure among bridge structures. Responsible for transferring loads between the towers and the main beam, the cables are crucial load-bearing components of cable-stayed bridges. Before replacing cables on a cable-stayed bridge, it is necessary to determine their length. However, because the cables of a cable-stayed bridge are curved in normal operation, and due to internal wire slack and cable tension variations, the actual length of cables in long-term operation differs from the length specified in the design data, making it difficult to meet actual requirements.

[0003] Currently, traditional methods for measuring the length of stay cables rely primarily on manual measurement and on-site construction data, which is not only time-consuming and labor-intensive, but also subject to large measurement errors. With the development of laser scanning technology, the acquisition of high-precision 3D point cloud data has become more convenient and efficient. Measurement methods based on point cloud models can provide detailed structural geometry information and highly accurate measurement results without contacting the structure, and are gradually becoming an important tool for structural health monitoring and inspection of bridge projects. Therefore, it is of great significance to utilize 3D laser scanning technology to determine the length of stay cables, reduce the measurement error of the stay cables, and ensure that the measured values ​​of the stay cables are consistent with the actual situation. Summary of the Invention

[0004] The problem to be solved by the present invention is: in view of the shortcomings of the traditional method for measuring the length of the inclined cable, the present invention provides a method for measuring the length of the inclined cable based on three-dimensional laser point cloud, which can quickly and efficiently complete the measurement of the length of the inclined cable.

[0005] The present invention adopts the following technical solution: a method for measuring the length of a stay cable based on a three-dimensional laser point cloud, comprising the following steps:

[0006] Step 1: Use a 3D laser scanner to scan the cable surface of the cable-stayed bridge to obtain a point cloud model of a single cable. x , y , z};

[0007] Step 2: Point cloud model of a single cable x , y , z}Segment to obtain multiple point cloud segments{ x i , y i ,z i};

[0008] Step 3: Segment the point cloud x i , y i , z i} Perform coordinate transformation to obtain cross-sectional point cloud { y w , z w};

[0009] Step 4: Cross-section point cloud y w , z w} Fit the coordinates of the center of the cross section and calculate the point cloud segment { x i , y i , z i}'s center coordinates;

[0010] Step 5: Calculate the cable length of the 3D laser point cloud using the center coordinates of all point cloud segments L 0, combined with the anchorage length of the inclined cable in the beam and tower body in the design data L 1 and L 2. Get the cable length L .

[0011] Preferably, step 1 specifically includes the following steps:

[0012] Step 1.1: Determine the location of the ground-based 3D laser scanner station based on the cable size and accuracy requirements of the cable-stayed bridge.

[0013] Step 1.2: Use a 3D laser scanner to scan the cable surface of the cable-stayed bridge to collect point cloud data of the cable surface. The cable scanning range is the cable between the intersection of the cable with the main beam and the intersection with the main tower.

[0014] Step 1.3: After scanning the cable surface to be measured and obtaining the cable surface point cloud data, preprocess the cable surface point cloud data;

[0015] Convert the surface point cloud data into x The axis corresponds to the direction of the cable length, y The axis corresponds to the horizontal direction perpendicular to the length of the cable. z The axis corresponds to the direction of the cable height. Then, the point cloud model of a single cable is extracted from the cable surface point cloud data. x , y ,z}.

[0016] Preferably, in step 2, the cable point cloud data is divided into a plurality of straight line point cloud segments, and in the cable point cloud data { x , y , z} along the x-axis direction by the horizontal length every Δ L Cut out the point cloud segment x i , y i , z i},as follows:

[0017] ;

[0018] in, m is the number of point cloud segments, rounded up. i =1,2,... , m ; Δ L The value is in the range of 0.1m to 1m, ensuring that there are enough points when fitting the circular curve of the cross section of the point cloud to reduce the random error of fitting; x max For point cloud model { x , y , z}middle x The maximum value of x min For point cloud model { x , y , z}middle x The minimum value of .

[0019] Preferably, step 3 specifically includes the following steps:

[0020] Step 3.1: Use a cubic polynomial to fit the point cloud model of the entire cable to obtain an approximate cable linear curve. The polynomial equation is as follows:

[0021] ;

[0022] in, A 、 B 、 C 、 D are the polynomial coefficients, x 、 z for{ x , y , z}middle x 、 z .

[0023] Step 3.2: Calculate the linear tangent angle of the point cloud segment based on the polynomial equation α 0, calculated as follows:

[0024] ;

[0025] in, x A Segment the point cloud x i , y i , z i}middle z The x-axis coordinate value of the point corresponding to the axis minimum value (point A).

[0026] Step 3.3: Point cloud segmentation x i , y i , z i}Rotate in the xz-axis plane with point A as the reference point α 0, get the rotated point cloud fragment { x w , y w , z w}, then project the rotated point cloud fragment onto the yz axis plane to obtain the cross-sectional point cloud { y w , z w}, the calculation is as follows:

[0027] .

[0028] Preferably, step 4 specifically includes the following steps:

[0029] Step 4.1: Based on the cross-section point cloud { y w , z w}, the least square method is used to fit the cross-section center, and the fitting circle equation is:

[0030] ;

[0031] Where, n is the number of points in the cross-sectional point cloud, a 、 b 、 c 、 d 、 e are fitting coefficients.

[0032] Step 4.2: According to the radius of the fitted circle r and the coordinates of the center of the fitted circle ( y r , z r ), calculate the segment of the point cloud after rotation { x w , y w , z w}Inner center of mass coordinates( x 0, y 0, z 0), calculated as follows:

[0033] ;

[0034] Where, α 0 is the linear tangent angle of the point cloud segment, x A is the x-axis coordinate value of point A.

[0035] Step 4.3: In the xz-axis plane, the center of mass coordinates ( x 0, y 0, y 0) Rotate back to the initial point cloud fragment { x i , y i , z i} position, obtain the center coordinates of the point cloud fragment ( x c , y c , z c );

[0036] The rotation is based on point A and the rotation angle is - α 0, the formula is as follows:

[0037] .

[0038] Preferably, step 5 specifically includes the following steps:

[0039] Step 5.1: Calculate the center coordinates of all point cloud segments ( x c , y c , z c ), the center coordinates of all point cloud segments ( x c , y c , zc ) form the precise linear coordinate points of the inclined cable { x ci , y ci , z ci}, the formula is as follows:

[0040] ;

[0041] Where, m is the number of point cloud segments.

[0042] Step 5.2: According to the linear coordinate point of the inclined cable { x ci , y ci , z ci}Calculate the cable length of the 3D laser point cloud L 0, the specific calculation formula is as follows:

[0043] .

[0044] Step 5.3: Obtain the anchorage length of the cable inside the beam and tower according to the design data L 1 and L 2. Calculate the cable length L ,as follows:

[0045] .

[0046] The technical solution of the present invention further provides: an electronic device, comprising:

[0047] one or more processors;

[0048] a storage device having one or more programs stored thereon;

[0049] When the one or more programs are executed by the one or more processors, the one or more processors implement any of the above-mentioned methods for measuring the length of a stayed cable based on three-dimensional laser point clouds.

[0050] The technical solution of the present invention also provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps in any of the above-mentioned methods for measuring the length of a cable-stayed cable based on three-dimensional laser point clouds are implemented.

[0051] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0052] The present invention applies 3D laser scanning technology to the cable length measurement. Leveraging the non-contact measurement, high accuracy, and high efficiency of 3D laser scanning, the method accurately calculates the cable length. By segmenting the cable's point cloud model into multiple point cloud segments, calculating the center coordinates of the point cloud segments, and determining the cable length based on the center coordinates of all the point cloud segments, the method then calculates the cable length based on the anchorage length of the cable within the beam and tower body based on design data. This method enables rapid and efficient cable length measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of the steps of the method for measuring the length of a stay cable based on three-dimensional laser point cloud of the present invention;

[0054] Figure 2 Schematic diagram of the point cloud model of a single stay cable of the present invention;

[0055] Figure 3 The linear angle of the point cloud segment of the present invention α 0 calculation diagram;

[0056] Figure 4 A flow chart of the steps for calculating cross-sectional point clouds according to the present invention;

[0057] Figure 5 This is a schematic diagram of the center coordinates of the point cloud segment calculated by the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the application are further elaborated in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in the present invention. All non-innovative embodiments of other researchers in this field on this embodiment fall within the scope of protection of the present invention. At the same time, the step numbers in the embodiments of the present invention are only set for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0059] In one embodiment of the present invention, a method for measuring the length of a stay cable based on a three-dimensional laser point cloud is provided. Figure 1 As shown, the following steps are included:

[0060] Step 1: Use a 3D laser scanner to scan the cable surface of the cable-stayed bridge to obtain a point cloud model of a single cable. x , y , z}.

[0061] This embodiment applies 3D laser scanning technology to the measurement of the length of the stay cable. The specific method is as follows: Figure 2 As shown, the sub-steps are as follows:

[0062] Step 1.1: Determine the location of the ground-based 3D laser scanner station based on the size and accuracy requirements of the cable surface where the cables to be measured are located on the cable-stayed bridge;

[0063] Step 1.2: Use a 3D laser scanner to scan the cable surface to be measured and collect point cloud data of the cable surface. The cable scanning range is the cable between the intersection point with the main beam and the intersection point with the main tower;

[0064] Step 1.3: After scanning the cable surface to be measured and obtaining the cable surface point cloud data, pre-process the cable surface point cloud data. Convert the cable surface point cloud data into x The axis corresponds to the direction of the cable length, y The axis corresponds to the horizontal direction perpendicular to the length of the cable. z The axis corresponds to the direction of the cable height; then, the point cloud model of a single cable is extracted from the cable surface point cloud data { x , y , z}.

[0065] Step 2: Segmentation of the cable point cloud data.

[0066] Since the linear shape of the cable is a curve, in order to facilitate calculation, the linear shape of the cable can be fitted using multiple straight lines. Therefore, in this embodiment, the point cloud data of the cable is divided into multiple straight line point cloud segments.

[0067] Specifically, for the point cloud model of a single cable { x , y , z} is segmented, and the cable point cloud model { x , y , z} in the x-axis direction and cut out point cloud segments at a horizontal length of 1 meter. x i , y i , z i}, the calculation is as follows:

[0068] ;

[0069] in, m is the number of point cloud segments, rounded up. i =1,2,... , m ; x max For point cloud model { x ,y , z}middle x The maximum value of x min For point cloud model { x , y , z}middle x The minimum value of .

[0070] Step 3: Point cloud segment coordinate conversion, point cloud segment { x i , y i , z i} Perform coordinate transformation to obtain cross-sectional point cloud { y w , z w}, the specific sub-steps are as follows:

[0071] Step 3.1: Accurately calculating the linear tangent of each point cloud segment is crucial for obtaining a reliable cross-sectional point cloud. In this embodiment, a cubic polynomial is used to fit the point cloud model of the entire cable segment to obtain an approximate linear curve of the cable. The polynomial equation is as follows:

[0072] ;

[0073] in, A 、 B 、 C 、 D are the polynomial coefficients, x 、 z For point cloud model { x , y , z}middle x 、 z .

[0074] Step 3.2: Calculate the linear tangent angle of the point cloud segment based on the polynomial equation α 0, such as Figure 3 As shown, the calculation is as follows:

[0075] ;

[0076] in, x A Segment the point cloud x i , y i , z i}middle z The x-axis coordinate value of the point corresponding to the axis minimum value (point A).

[0077] Step 3.3: Cross-section point cloud y w , z w}calculate;

[0078] like Figure 4 As shown, point cloud segmentation { x i , y i , z i}Rotate in the xz-axis plane with point A as the reference point α 0, get the rotated point cloud fragment { x w , y w , z w}.

[0079] Then, the rotated point cloud fragment is projected onto the yz axis plane to obtain the cross-sectional point cloud { y w , z w}, the calculation is as follows:

[0080] .

[0081] Step 4: Cross-section point cloud y w , z w} Fit the coordinates of the center of the cross section and calculate the point cloud segment { x i , y i , z i}, such as Figure 5 As shown, the specific steps include:

[0082] Step 4.1: Fit the center of the cross-section point cloud.

[0083] According to the cross-section point cloud { y w , z w}, the least square method is used to fit the cross-section center, and the fitting circle equation is:

[0084] ;

[0085] Where, n is the number of points in the cross-sectional point cloud, a 、 b 、c 、 d 、 e All are coefficients. In this embodiment, the coefficients are set as follows:

[0086] .

[0087] Step 4.2: Calculate the centroid coordinates of the point cloud segment;

[0088] According to the radius of the fitted circle r and the coordinates of the center of the fitted circle ( y r , z r ), calculate the segment of the point cloud after rotation { x w , y w , z w}Inner center of mass coordinates( x 0, y 0, z 0), the formula is as follows:

[0089] ;

[0090] Where, α 0 is the linear tangent angle of the point cloud segment, x A is the x-axis coordinate value of point A.

[0091] Step 4.3: Calculate the center coordinates of the point cloud segment;

[0092] In the xz-axis plane, the center of mass coordinates ( x 0, y 0, y 0) Rotate back to the initial point cloud fragment { x i , y i , z i} position, obtain the center coordinates of the point cloud fragment ( x c , y c , z c );

[0093] The rotation is based on point A and the rotation angle is - α 0, the formula is as follows:

[0094] .

[0095] Step 5: Cable length calculation, use the center coordinates of all point cloud segments to calculate the cable length of the 3D laser point cloud part L 0, combined with the anchorage length of the inclined cable in the beam and tower body in the design data L 1 and L 2. Get the cable length L , specifically including the following steps:

[0096] Step 5.1: Calculate the center coordinates of all point cloud segments ( x c , y c , z c ), the center coordinates of all point cloud segments ( x c , y c , z c ) form the precise linear coordinate points of the inclined cable { x ci , y ci , z ci}, the calculation formula is as follows:

[0097] ;

[0098] Where, m is the number of point cloud segments.

[0099] Step 5.2: According to the linear coordinate point of the inclined cable { x ci , y ci , z ci}, calculate the cable length of the 3D laser point cloud part L 0, the formula is as follows:

[0100] .

[0101] Step 5.3: Obtain the anchorage length of the cable inside the beam and tower according to the design data L 1 and L 2. Calculate the cable length L ,as follows:

[0102] ;

[0103] In the formula, { x ci , y ci , zci}and{ x c(i+1) , y c(i+1) , z c(i+1)} respectively i and i +1 center coordinate of the linear coordinate point of the inclined cable.

[0104] An embodiment of the present invention also provides an electronic device, comprising: one or more processors; a storage device on which one or more programs are stored; when the one or more programs are executed by the one or more processors, the one or more processors implement the method for measuring the length of a cable based on three-dimensional laser point cloud described in any of the above embodiments.

[0105] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the steps of any one of the methods for measuring the length of a stay cable based on a three-dimensional laser point cloud in the above embodiments are implemented.

[0106] In summary, the present invention applies three-dimensional laser scanning technology to the measurement of the length of the inclined cable. Based on the three-dimensional laser point cloud model, it realizes the rapid and efficient measurement of the length of the inclined cable without contacting the specific inclined cable structure.

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring the length of a stay cable based on three-dimensional laser point cloud, characterized in that: The steps include: Step 1: Use a 3D laser scanner to scan the cable surface of the cable-stayed bridge to obtain a point cloud model of a single cable. x , y , z }; Step 2: Point cloud model of a single cable x , y , z }Segment to obtain multiple point cloud segments{ x i , y i , z i }; Step 3: Segment the point cloud x i , y i , z i } Perform coordinate transformation to obtain cross-sectional point cloud { y w , z w }, specifically including the following steps: Step 3.1: Use a cubic polynomial to fit the point cloud model of the entire cable to obtain an approximate cable linear curve. The cubic polynomial equation is expressed as follows: ； in, A 、 B 、 C 、 D are the polynomial coefficients, x 、 z for{ x , y , z }middle x 、 z ; Step 3.2: Calculate the linear tangent angle of the point cloud segment based on the cubic polynomial equation α 0, calculated as follows: ； in, x A Segment the point cloud x i , y i , z i }middle z The minimum axis value corresponds to the x-axis coordinate value of point A; Step 3.3: Segment the point cloud x i , y i , z i }Rotate in the xz-axis plane with point A as the reference point α 0, get the rotated point cloud fragment { x w , y w , z w }, project the rotated point cloud fragment onto the yz axis plane to obtain the cross-sectional point cloud { y w , z w }, the calculation is as follows: ； in, z A Segment the point cloud x i , y i , z i }middle z The minimum axis value corresponds to the z-axis coordinate value of point A; Step 4: Cross-section point cloud y w , z w } Fit the coordinates of the center of the cross section and calculate the point cloud segment { x i , y i , z i }, specifically including the following steps: Step 4.1: Based on the cross-section point cloud { y w , z w }, the least square method is used to fit the cross-section center, and the radius of the fitting circle is r , the coordinates of the fitting circle center are ( y r , z r ); Step 4.2: Calculate the segment of the rotated point cloud according to the radius of the fitted circle and the coordinates of the center of the fitted circle { x w , y w , z w }Inner center of mass coordinates( x 0, y 0, z 0), calculated as follows: ； Step 4.3: In the xz-axis plane, the center of mass coordinates ( x 0, y 0, y 0) Rotate back to the initial point cloud fragment { x i , y i , z i } position, obtain the center coordinates of the point cloud fragment ( x c , y c , z c ), the rotation is based on point A, and the rotation angle is - α 0, the formula is as follows: ； Step 5: Calculate the cable length of the 3D laser point cloud using the center coordinates of all point cloud segments L 0, combined with the anchorage length of the inclined cable in the beam and tower body in the design data L 1 and L 2. Get the cable length L , specifically including the following steps: Step 5.1: Calculate the center coordinates of all point cloud segments ( x c , y c , z c ), the center coordinates of all point cloud segments ( x c , y c , z c ) form accurate linear coordinate points of the inclined cable { x ci , y ci , z ci }, the formula is as follows: ； Step 5.2: According to the linear coordinate point of the inclined cable { x ci , y ci , z ci }Calculate the cable length of the 3D laser point cloud L 0, the formula is as follows: ； in,{ x ci , y ci , z ci }and{ x c(i+1) , y c(i+1) , z c(i+1) } respectively i and i +1 linear coordinate point of the inclined cable, m is the number of point cloud segments, rounded up. i =1,2,... , m ; Step 5.3: Obtain the anchorage length of the cable in the beam and tower according to the design data, and calculate the cable length L , the formula is as follows: ； in, L 1 is the anchorage length of the cable inside the beam, L 2 is the anchorage length of the inclined cable inside the tower body.

2. The method for measuring the length of a stay cable based on three-dimensional laser point cloud according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 1.1: Determine the location of the ground-based 3D laser scanner station based on the cable-stayed bridge cable size and accuracy requirements. Step 1.2: Use a 3D laser scanner to scan the cable surface of the cable-stayed bridge to collect point cloud data of the cable surface. The cable scanning range is the cable between the intersection of the cable with the main beam and the intersection with the main tower; Step 1.3: After scanning the cable surface to be measured and obtaining the cable surface point cloud data, pre-process the cable surface point cloud data and convert the cable surface point cloud data into x The axis corresponds to the direction of the cable length, y The axis corresponds to the horizontal direction perpendicular to the length of the cable. z The axis corresponds to the direction of the cable height, and the point cloud model of a single cable is extracted from the cable surface point cloud data { x , y , z }.

3. The method for measuring the length of a stay cable based on three-dimensional laser point cloud according to claim 1, characterized in that: In step 2, the cable point cloud data is divided into multiple straight line point cloud segments by fitting the cable line shape through multiple straight line segments. x , y , z } along the x-axis direction by the horizontal length every Δ L Cut out the point cloud segment x i , y i , z i },as follows: ； in, x max For point cloud model { x , y , z }middle x The maximum value of x min For point cloud model { x , y , z }middle x The minimum value of .

4. The method for measuring the length of a stay cable based on three-dimensional laser point cloud according to claim 1, characterized in that: In step 4.1, the least squares method is used to fit the center of the cross section. The fitting circle equation is as follows: ； Where, n is the number of points in the cross-sectional point cloud, a 、 b 、 c 、 d 、 e are fitting coefficients.

5. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the method for measuring the length of a stay cable based on three-dimensional laser point cloud as described in any one of claims 1 to 4.

6. A computer-readable storage medium, characterized in that A computer program is stored thereon, and when the program is executed by a processor, the steps in the method for measuring the length of a stay cable based on a three-dimensional laser point cloud as described in any one of claims 1 to 4 are implemented.

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