阅读说明：本技术 一种基于激光定位的塔脚节点姿态确定方法及系统 (Tower foot node posture determination method and system based on laser positioning ) 是由 刘海锋 李茂华 刘亚多 于 2021-07-01 设计创作，主要内容包括：一种基于激光定位的塔脚节点姿态确定方法及系统,包括：在节点板上的有限个不共面定位圆环处安装靶标；用激光扫描设备采集节点板表面点云信息并从点云信息中识别靶标信息；基于靶标信息确定形心位置作为源点云；将塔脚数字模型中对应形心位置信息作为目标点云并结合源点云利用点云配准算法计算位置转换矩阵作为塔脚节点姿态矩阵；其中,所述塔脚数字模型是通过软件生成的塔脚节点精细化三维模型,所述塔脚数字模型中定位圆环的位置与节点板上定位圆环位置相同。本发明通过采用输电塔塔脚节点上若干个关键点的位置信息,利用点云配准计算节点空间姿态矩阵,相比人工尺具测量或激光点云三维重构方法,提高了精度和效率,避免求解不收敛。(A tower foot node posture determining method and system based on laser positioning comprises the following steps: mounting targets at a limited number of non-coplanar positioning rings on the gusset plate; collecting node plate surface point cloud information by using laser scanning equipment and identifying target information from the point cloud information; determining a centroid position as a source point cloud based on the target information; taking the corresponding centroid position information in the tower foot digital model as a target point cloud, and calculating a position conversion matrix by combining a source point cloud and utilizing a point cloud registration algorithm as a tower foot node attitude matrix; the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate. According to the invention, the position information of a plurality of key points on the tower foot node of the power transmission tower is adopted, and the node space attitude matrix is calculated by point cloud registration, so that compared with a manual ruler measurement or laser point cloud three-dimensional reconstruction method, the precision and efficiency are improved, and the problem of solution non-convergence is avoided.)

1. A tower foot node posture determining method based on laser positioning is characterized by comprising the following steps:

installing targets at a limited preset non-coplanar positioning circular ring on the gusset plate;

utilizing point cloud information of the surface of the node plate acquired by laser scanning equipment, and identifying the target information from the point cloud information according to the contrast;

determining centroid position information of a target as a source point cloud based on the target information;

using centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud and utilizing a point cloud registration algorithm;

taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

2. The method of claim 1, wherein the step of using centroid position information of a positioning ring in the tower foot digital model as a target point cloud and computing a position transformation matrix using a point cloud registration algorithm in combination with a source point cloud comprises:

step 1: establishing a target function with the least square of the difference between a source point cloud and a target point cloud after Euclidean transformation;

step 2: calculating an extreme value by using an objective function to calculate a translation amount t, and substituting the calculated translation amount t into the objective function to obtain a new objective function;

and step 3: calculating and simplifying the new objective function to obtain a key item function, and solving a rotation matrix R by utilizing SVD (singular value decomposition) on the basis of the key item function;

and 4, step 4: performing Euclidean transformation on the source point cloud by using the rotation matrix R and the translation quantity t to obtain a new point cloud, and taking the new point cloud as the source point cloud;

and 5: and (3) calculating the square of the difference value between the source point cloud and the target point cloud, if the square of the difference value is greater than a set threshold value, executing the step (1), and otherwise, taking the rotation matrix R as a position conversion matrix.

3. The determination method of claim 2, wherein the source point cloud and the target point cloud are as follows:

P＝{p₁，p₂，…，p_n}

Q＝{q₁，q₂，…，q_n}

wherein: p is the point cloud of the actual tower foot target, Q is the point cloud of the virtual tower foot target, n is the total number of data points in the point cloud, P_nAnd q is_nAre data points in the point cloud.

4. The determination method of claim 3, wherein the objective function is as follows:

wherein: t is the translation amount of the point cloud;the rotation amount of the point cloud; i is the number of data in the point cloud, q_iAs data points of the target point cloud, p_iThe data points of the source point cloud.

5. The determination method of claim 4, wherein the translation amount t of the point cloud is as follows:

wherein:is the coordinates of the center of mass of the target point cloud,the centroid coordinate of the source point cloud is the rotation matrix.

6. The method of determining of claim 5, wherein the centroid coordinates of the target point cloudAs follows:

centroid coordinates of the source point cloudAs follows:

wherein: n is the total number of data points in the point cloud.

7. The determination method of claim 6, wherein the new objective function is as follows:

wherein: x is the number of_iIs the x coordinate of the ith data point; y is_iIs the y coordinate of the ith data point;is the amount of rotation of the data point.

8. The method of claim 7, wherein the x coordinate of the ith data point is x_iAs follows:

y coordinate y of the ith data point_iAs follows:

9. the determination method of claim 8, wherein the key term function is as follows:

10. a tower foot node attitude determination system based on laser positioning, comprising: the system comprises a target installation module, a target information identification module, a source point cloud determination module and a tower foot node attitude matrix determination module;

the target mounting module is used for mounting targets at a limited preset non-coplanar positioning circular ring on the node board;

the target information identification module is used for utilizing point cloud information of the surface of the node plate acquired by the laser scanning equipment and identifying the target information from the point cloud information according to the contrast;

the source point cloud determining module is used for determining centroid position information of the target as a source point cloud based on the target information;

the tower foot node attitude matrix determination module is used for taking centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud by using a point cloud registration algorithm;

the tower foot node attitude matrix determination module is used for taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

Technical Field

The invention relates to the field of steel pipe power transmission tower processing, in particular to a method and a system for determining tower foot node postures based on laser positioning.

Background

The tower foot node of the power transmission tower is composed of a plurality of steel plates which need to be welded together to form a whole so as to transmit the axial force of the main material and the diagonal material to the foundation of the power transmission tower. For a long time, the tower feet of the power transmission tower are all welded manually. At present, with the rapid development of information technology, advanced numerical control equipment such as a welding robot arm and the like is beginning to replace manual welding. When the tower foot nodes of the power transmission tower are welded by means of advanced numerical control equipment such as a robot arm and the like, the node plates on the tower foot nodes are generally connected into a whole in a spot welding mode; then determining the space position of the node, establishing a digital model of the node according to the position, finally generating a welding instruction of the node by using a computer program, and completing the welding operation by the welding robot. Wherein the accurate determination of the spatial position of the weldment has a significant impact on the weld quality.

At present, the posture of a node is determined mainly by manpower according to various rulers, so that the workload is large and the node is not accurate; methods have also been proposed for scanning nodes with laser light and performing three-dimensional reconstruction to determine the node poses. However, this method has the following 2 disadvantages: 1) the scanning and data processing time is long, and the welding efficiency is influenced. When the operations such as laser point cloud registration, identification and the like are carried out, the calculation time is in direct proportion to the square of the number of data points, and considering that the number of the data points of the laser point cloud is generally more than 5000, the processing time of a computer using the method can be more than one hour, so that the welding efficiency is seriously influenced; 2) at present, a laser point cloud registration algorithm is an iterative algorithm, and has no analytic solution, so that the iteration of the laser point cloud registration algorithm often fails, and the laser point cloud registration algorithm has a high probability and cannot converge to an accurate solution, so that the solution fails.

Disclosure of Invention

In order to solve the above problems in the prior art, the present invention provides a method for determining a tower foot node posture based on laser positioning, which includes:

installing targets at a limited preset non-coplanar positioning circular ring on the gusset plate;

utilizing point cloud information of the surface of the node plate acquired by laser scanning equipment, and identifying the target information from the point cloud information according to the contrast;

determining centroid position information of a target as a source point cloud based on the target information;

using centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud and utilizing a point cloud registration algorithm;

taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

Preferably, the step of calculating the position conversion matrix by using the centroid position information of the positioning ring in the tower foot digital model as the target point cloud and combining the source point cloud and the point cloud registration algorithm includes:

step 1: establishing a target function with the least square of the difference between a source point cloud and a target point cloud after Euclidean transformation;

step 2: calculating an extreme value by using an objective function to calculate a translation amount t, and substituting the calculated translation amount t into the objective function to obtain a new objective function;

and step 3: calculating and simplifying the new objective function to obtain a key item function, and solving a rotation matrix R by utilizing SVD (singular value decomposition) on the basis of the key item function;

and 4, step 4: performing Euclidean transformation on the source point cloud by using the rotation matrix R and the translation quantity t to obtain a new point cloud, and taking the new point cloud as the source point cloud;

and 5: and (3) calculating the square of the difference value between the source point cloud and the target point cloud, if the square of the difference value is greater than a set threshold value, executing the step (1), and otherwise, taking the rotation matrix R as a position conversion matrix.

Preferably, the source point cloud and the target point cloud are as follows:

P＝{p₁，p₂,…,p_n}

Q＝{q₁,q₂，…，q_n}

wherein: p is the point cloud of the actual tower foot target, Q is the point cloud of the virtual tower foot target, n is the total number of data points in the point cloud, P_nAnd q is_nAre data points in the point cloud.

Preferably, the objective function is as follows:

wherein: t is the translation amount of the point cloud; r_piThe rotation amount of the point cloud; i is the number of data in the point cloud, q_iAs data points of the target point cloud, p_iThe data points of the source point cloud.

Preferably, the translation amount t of the point cloud is as follows:

wherein:is the coordinates of the center of mass of the target point cloud,is the centroid coordinate of the source point cloud, and R is the rotation matrix.

Preferably, the coordinates of the center of mass of the target point cloudAs follows:

centroid coordinates of the source point cloudAs follows:

wherein: n is the total number of data points in the point cloud.

Preferably, the new objective function is as follows:

wherein: x is the number of_iIs the x coordinate of the ith data point; y is_iIs the y coordinate of the ith data point;is the amount of rotation of the data point.

Preferably, the x coordinate x of the ith data point_iAs follows:

y coordinate y of the ith data point_iAs follows:

preferably, the key term function is as follows:

based on the same invention concept, the invention provides a tower foot node attitude determination system based on laser positioning, which comprises: the system comprises a target installation module, a target information identification module, a source point cloud determination module and a tower foot node attitude matrix determination module;

the target mounting module is used for mounting targets at a limited preset non-coplanar positioning circular ring on the node board;

the target information identification module is used for utilizing point cloud information of the surface of the node plate acquired by the laser scanning equipment and identifying the target information from the point cloud information according to the contrast;

the source point cloud determining module is used for determining centroid position information of the target as a source point cloud based on the target information;

the tower foot node attitude matrix determination module is used for taking centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud by using a point cloud registration algorithm;

the tower foot node attitude matrix determination module is used for taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

Compared with the prior art, the invention has the beneficial effects that:

a tower foot node posture determining method based on laser positioning comprises the following steps: installing targets at a limited preset non-coplanar positioning circular ring on the gusset plate; utilizing point cloud information of the surface of the node plate acquired by laser scanning equipment, and identifying the target information from the point cloud information according to the contrast; determining centroid position information of a target as a source point cloud based on the target information; using centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud and utilizing a point cloud registration algorithm; taking the position conversion matrix as a tower foot node attitude matrix; the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate. The invention adopts laser scanning equipment to collect the position information of a plurality of key points on the foot node of the power transmission tower, and calculates the space attitude matrix of the node by point cloud allocation. Compared with a method based on manual ruler measurement or laser point cloud three-dimensional reconstruction, the method has high precision and efficiency, and the situation of solution non-convergence can be avoided.

Drawings

FIG. 1 is a flow chart of the tower foot node pose determination steps for laser positioning of the present invention;

fig. 2 is a schematic view of the position of the target of the present invention on the tower foot node.

Detailed Description

For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples.

Example 1:

in order to solve the above problems in the prior art, the present invention provides a method for determining a tower foot node pose based on laser positioning, as shown in fig. 1, including:

step 1: installing targets at a limited preset non-coplanar positioning circular ring on the gusset plate;

step 2: utilizing point cloud information of the surface of the node plate acquired by laser scanning equipment, and identifying the target information from the point cloud information according to the contrast;

and step 3: determining centroid position information of a target as a source point cloud based on the target information;

and 4, step 4: using centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud and utilizing a point cloud registration algorithm;

and 5: taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

Step 1 is as shown in fig. 2, 4 circular rings are printed and positioned on a steel plate, the diameter of each circular ring is about 10mm, the distance between every two circular rings needs to be larger than 10cm, and the 4 circular rings cannot be coplanar. The position of the positioning ring is arbitrary as long as the above requirements are met.

The base of the magnetic target installed at the positioning circular ring is circular, and the base of the magnetic target needs to be placed in the laser marking circular ring when laser point cloud collection is carried out. Since the tower foot nodes are generally gray black, the target is white in color to enhance the contrast of the gray scale.

And 2, acquiring point cloud information of the node board by using three-dimensional laser scanning equipment, wherein the equipment is placed obliquely above a power transmission tower foot node and can emit surface laser, and the main purpose is to acquire the point cloud information of key points on the node and further determine the centroid of the target.

Step 3, collecting point clouds on the surface of the node plate according to laser scanning equipment, and identifying a hemispherical target in the point clouds; then, determining the spherical centers of the targets;

and 4, calculating a position conversion matrix of the target sphere center in the actual tower foot and the target sphere center in the digital model by using a point cloud registration algorithm. In this way, the spatial attitude of the actual tower foot is determined, providing the necessary data for the welding job at that node. The digital model of the node refers to a refined three-dimensional model of the node, and can be generated by software such as TEKLA and SOLIDWORKS.

The calculation method of the position conversion matrix R of the target sphere center in the actual tower foot and the target sphere center in the digital model comprises the following steps:

(1) determining the target positions of the tower foot nodes and the corresponding positions of the digital model to form two groups of corresponding point sets:

P＝{p₁，p₂，…，p_n}

Q＝{q₁，q₂，…，q_n}

wherein: p is the point cloud of the actual tower foot target, Q is the point cloud of the virtual tower foot target, n is the total number of data points in the point cloud, P_nAnd q is_nAre data points in the point cloud.

The euclidean transformation R, t is solved such that:

t is the translation amount of the point cloud; r_piIs the amount of rotation of the point cloud. And i is the serial number of the data in the point cloud. q. q.s_iAs data points of the target point cloud, p_iThe data points of the source point cloud.

Iterative calculation is carried out based on a least square method, so that the sum of squared errors reaches a minimum value:

(2) solving translation amount

F (t) partial derivatives are calculated for t, so as to obtain:

order toObtaining:

defining the centroids of the actual point cloud and the virtual point cloud as follows:

thus, the number of the first and second electrodes,

wherein:is the coordinates of the center of mass of the target point cloud,is the centroid coordinate of the source point cloud, and R is the rotation matrix.

Substituting t into F (t) can obtain:

defining the centroid-removing coordinates:

thus, the objective function becomes:

wherein: x is the number of_iIs the x coordinate of the ith data point; y is_iIs the y coordinate of the ith data point;is the amount of rotation of the data point.

(3) Solving rotation matrix

Is a scalar quantity, and for any scalar quantity alpha, alpha is satisfied^TThus, therefore, it is

Bringing it into the objective function yields:

therefore, the temperature of the molten metal is controlled,

as can be seen from the above, the present invention,

wherein X and Y are 3 Xn dimensional matrices.

Defining a covariance matrix S-XY^TAnd performing SVD on S:

S＝U∑V^T

thus, solving the problem becomes maximizing the following:

tr(RXY^T)＝tr(RS)＝tr(RU∑V^T)＝tr(∑V^TRU)

let M be V^TRU ofIs an orthogonal array, the column vector m of which_jAre orthonormal vectors, i.e.Thus, there is M for all elements of M_ij≤1。

When m is_iiWhen 1, tr (Σ M) is maximum; m is again an orthogonal array, so M must be a unit array.

Thus, the position and orientation R of the tower foot node is obtained.

The patent provides a method for determining the posture of a tower foot by scanning key points of the tower foot nodes by laser and comparing the key points with key points of a digital model. Because the patent only scans and processes 4 points and provides an analytic formula for determining the node posture according to the 4 points, the patent has extremely high operation speed and does not have the problem of inconvergence of iteration. Therefore, the working efficiency and the calculation accuracy of the method are far higher than those of manual and existing three-dimensional reconstruction methods.

The invention adopts laser scanning equipment to collect the position information of a plurality of key points on the foot node of the power transmission tower, and calculates the space attitude matrix of the node by using a correlation formula. Compared with a method based on manual ruler measurement or laser point cloud three-dimensional reconstruction, the method has high precision and efficiency, and the situation of solution non-convergence can be avoided.

Example 2:

based on the same invention concept, the invention also provides a tower foot node attitude determination system based on laser positioning, which comprises: the system comprises a target installation module, a target information identification module, a source point cloud determination module and a tower foot node attitude matrix determination module;

the target mounting module is used for mounting targets at a limited preset non-coplanar positioning circular ring on the node board;

the target information identification module is used for utilizing point cloud information of the surface of the node plate acquired by the laser scanning equipment and identifying the target information from the point cloud information according to the contrast;

the source point cloud determining module is used for determining centroid position information of the target as a source point cloud based on the target information;

the tower foot node attitude matrix determination module is used for taking centroid position information of a positioning ring in the tower foot digital model as target point cloud and calculating a position conversion matrix by combining with source point cloud by using a point cloud registration algorithm;

the tower foot node attitude matrix determination module is used for taking the position conversion matrix as a tower foot node attitude matrix;

the tower foot digital model is a tower foot node refined three-dimensional model generated through software, and the position of a positioning ring in the tower foot digital model is the same as the position of a positioning ring on a node plate.

It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.