Intersecting line welding seam extraction method, medium and equipment

Abstract

The invention relates to an intersecting line welding seam extraction method, a medium and equipment. The method comprises the following steps: constructing an initial intersecting line welding seam model, collecting workpiece contour point clouds, obtaining a plurality of main pipe local point clouds and a plurality of branch pipe local point clouds, fitting elliptic equations for the local point clouds, obtaining circle centers corresponding to the local point clouds, fitting straight lines according to the circle centers, and extracting intersecting line welding seams. Obtaining the surface parameters of the main pipe according to the elliptic equations, updating the initial intersecting line welding seam model according to the axis equations and the surface parameters of the main pipe, obtaining an optimized intersecting line model, obtaining the included angle between the axis equations of the main pipe and the branch pipes and a conversion matrix, and substituting the included angle and the conversion matrix into the optimized intersecting line model. And obtaining an intersecting line parameter equation so as to extract an intersecting line welding seam. The problems that in the prior art, machining precision is low, adaptability is insufficient, meanwhile, collection precision is low due to high workpiece reflective rate, and welding quality is affected are solved.

Description

Technical Field

[0001] The invention relates to the technical field of automated welding, and in particular to a method, medium and equipment for extracting an intersecting weld. Background Art

[0002] Intersecting line welding is a common welding process, mainly used for the connection of two pipes or similar cylindrical workpieces. In the early days, intersecting line welding mainly relied on manual operation, but with the development of robot technology, robot welding gradually replaced manual welding and became the mainstream welding method. At present, there are two main methods for robot welding of intersecting lines: the first is teaching trajectory welding. This method requires manual compilation of a welding trajectory for each specification of workpiece. Although this method can ensure high-precision welding of a single part, it has extremely high requirements for processing and tooling accuracy, and each different part needs to be individually arranged for welding trajectories, resulting in high labor costs. The second method is to guide robot welding by establishing a mathematical model of the intersecting line and sampling weld points on the relevant curve. The labor cost of this method is relatively low, and the parametric equations of various workpieces can be obtained by CAD drawings or idealized workpieces, and it is also relatively easy to expand to other parts later. However, this method also has high requirements for the processing accuracy and tooling accuracy of the parts, and cannot dynamically adapt to subtle changes in the parts, which may affect the welding quality. Due to the limitations of existing robot welding technology, neither teaching programming nor model-based welding methods can flexibly adapt to changes in parts, and at the same time, they require extremely high processing and tooling accuracy. In order to solve these problems, more and more machine vision-based solutions have been proposed. However, for stainless steel parts, due to their strong reflectivity, it is difficult to obtain clear and complete images using either 3D cameras or line scan cameras, making it difficult to accurately extract weld information.

[0003] Therefore, how to improve the existing technology's low processing accuracy, insufficient adaptability, and high workpiece reflectivity leading to low collection accuracy, affecting welding quality, and other problems, is a technical problem that needs to be urgently solved in this field. Summary of the invention

[0004] Based on this, the purpose of this application is to provide a method, medium and equipment for extracting intersecting line welds to solve at least one technical problem mentioned in the above background technology.

[0005] In a first aspect, the present application provides a method for extracting an intersecting weld, comprising:

[0006] Construct the initial intersection weld model;

[0007] Collect the workpiece contour point cloud to obtain several main local point clouds and several sub-local point clouds;

[0008] Fitting an elliptic equation to each local point cloud to obtain the center of the circle corresponding to each local point cloud;

[0009] Fitting a straight line according to the center of the circle to obtain the axis equations of the main pipe and the branch pipe, and obtaining the surface parameters of the main pipe according to each elliptic equation, so as to update the initial intersecting line weld model according to the axis equations and the surface parameters of the main pipe to obtain an optimized intersecting line model;

[0010] Obtaining the included angle between the axis equations of the main pipe and the branch pipe and the transformation matrix, substituting them into the optimized intersecting line model to obtain the parametric equation of the intersecting line, so as to extract the intersecting line weld.

[0011] Further, the steps of constructing the initial intersecting line weld model include:

[0012] Obtaining the axis of the main pipe, the radius of the main pipe, the axis of the branch pipe, and the radius of the branch pipe, and obtaining the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system according to the axis of the main pipe and the axis of the branch pipe;

[0013] Constructing the main pipe coordinate system and the branch pipe coordinate system according to the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system, and constructing the main pipe cylinder equation and the branch pipe cylinder equation according to the radius of the main pipe and the radius of the branch pipe;

[0014] Obtaining the origin distance between the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system, and the axis included angle between the axis of the main pipe and the axis of the branch pipe, so as to obtain the rotation matrix between the main pipe coordinate system and the branch pipe coordinate system according to the origin distance and the axis included angle;

[0015] Obtaining the linear transformation relationship between the main pipe coordinate system and the branch pipe coordinate system according to the rotation matrix, the main pipe cylinder equation and the branch pipe cylinder equation, so as to construct the initial intersecting line weld model according to the linear transformation relationship and the prior geometric constraint relationship of the intersecting line.

[0016] Further, the steps of collecting the workpiece contour point cloud to obtain several main pipe local point clouds and several branch pipe local point clouds include:

[0017] Collecting the workpiece contour point cloud to obtain the coordinates of each point cloud and obtaining the curvature of each point cloud;

[0018] Extracting the main pipe end face points and the branch pipe end face points according to the coordinates of each point cloud, and obtaining the first intersection point between the main pipe and the branch pipe according to the point cloud curvature;

[0019] Obtaining the second intersection point between the main pipe and the branch pipe according to the prior branch pipe radius and the first intersection point coordinates;

[0020] Uniformly sampling the workpiece contour point cloud according to the main pipe end face points, the branch pipe end face points, and the first intersection point between the main pipe and the branch pipe to obtain several main pipe local point clouds and several branch pipe local point clouds.

[0021] Further, the steps to obtain the optimized intersection curve model include:

[0022] Fit a straight line according to the center coordinates to obtain the axis equations of the main pipe and the branch pipe;

[0023] Obtain the arithmetic mean of the parameters of each cross-section equation, construct the equation of the main pipe elliptic cylinder, and obtain the parameters of the main pipe surface;

[0024] Obtain the actual elliptical contour according to the equation of the main pipe elliptic cylinder, and obtain the distance between any point on the actual elliptical contour and the corresponding center according to the first intersection point, the second intersection point and the parameters of the main pipe surface;

[0025] Obtain the calculation formula for the z-axis coordinate of each point in the world coordinate system according to the distance between any point on the actual elliptical contour and the corresponding center, and substitute it into the initial intersection curve weld model to obtain the optimized intersection curve model.

[0026] Further, the steps of obtaining the actual elliptical contour according to the equation of the main pipe elliptic cylinder and obtaining the distance between any point on the actual elliptical contour and the corresponding center according to the first intersection point, the second intersection point and the parameters of the main pipe surface include:

[0027] Determine the actual elliptical contour according to the equation of the main pipe elliptic cylinder;

[0028] Substitute the parameters of the main pipe surface into the elliptical calculation formula to obtain the major and minor axes of the actual elliptical contour;

[0029] Connect the first intersection point and the second intersection point to the corresponding center to obtain the first connection line and the second connection line;

[0030] Obtain the angular values between the first connection line, the second connection line and the major axis, and obtain the angular difference between them;

[0031] Substitute the angular difference into the angular conversion formula to obtain the intersection curve angle between the connection line of any point on the intersection curve of the actual elliptical contour and the corresponding center and the major axis;

[0032] Substitute the major and minor axes of the actual elliptical contour and the intersection curve angle into the distance calculation formula to obtain the distance from any point on the actual elliptical contour to the center.

[0033] Further, the optimized intersection curve model is expressed as:

[0034]

[0035] where (x, y, z) are the coordinates of the intersection curve weld point in the world coordinate system, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

[0036] Further, after obtaining the optimized intersection curve model, it also includes:

[0037] Calculate the compensation amount by back-calculating based on the trajectory result, and modify the optimized intersection line model according to the compensation amount to obtain the final intersection line model:

[0038]

[0039] Among them, the f function is a linear function, expressed as Equation 4-12:

[0040] Δz = k1θ + k2α + k3R + k4r 4-12

[0041] Among them, Δz is the compensation amount, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the included angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

[0042] Further, after obtaining the parametric equation of the intersection line, it also includes:

[0043] Substitute the branch pipe angle parameter into the parametric equation of the intersection line to obtain the intersection line weld;

[0044] Or, evenly divide the branch pipe angle parameter to obtain several angle values, and substitute them into the parametric equation of the intersection line in sequence to obtain several intersection line weld points.

[0045] In a second aspect, the present application also provides a computer storage medium storing executable program code; the executable program code is used to execute the intersection line weld extraction method according to any one of the first aspects.

[0046] In a third aspect, the present application also provides a terminal device including a memory and a processor; the memory stores program code executable by the processor; the program code is used to execute the intersection line weld extraction method according to any one of the first aspects.

[0047] A method, medium, and device for extracting intersecting line welds provided by the present invention can adapt to changes in part components by constructing an initial intersecting line weld model, improving the adaptability of the method. Then, by collecting the contour point cloud of the workpiece, a number of local point clouds of the main pipe and a number of local point clouds of the branch pipe are obtained. The elliptic equations are respectively fitted to each local point cloud to obtain the center points corresponding to each local point cloud. By collecting the contour point cloud of the workpiece, the influence of the reflective area of the workpiece on the collection of the point cloud of the workpiece by the collection device is avoided, improving the collection accuracy. Then, a straight line is fitted according to the center points to obtain the axis equations of the main pipe and the branch pipe, and the surface parameters of the main pipe are obtained according to each elliptic equation. The initial intersecting line weld model is updated according to the axis equations and the surface parameters of the main pipe to obtain an optimized intersecting line model. Finally, the included angle and transformation matrix between the axis equations of the main pipe and the branch pipe are obtained and substituted into the optimized intersecting line model to obtain the parametric equation of the intersecting line, so as to extract the intersecting line weld. This solves the problems in the prior art such as low machining accuracy, insufficient adaptability, and low collection accuracy caused by the high reflectivity of the workpiece, which affects the welding quality, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a flowchart of the method for extracting intersecting line welds according to an embodiment of the present invention;

[0049] Figure 2 It is a schematic flow diagram of the method for extracting intersecting line welds according to an embodiment of the present invention;

[0050] Figure 3 It is a schematic diagram of the initial intersecting line weld model according to an embodiment of the present invention;

[0051] Figure 4 It is a projection diagram of the initial intersecting line weld model according to an embodiment of the present invention;

[0052] Figure 5 It is a schematic diagram of the first intersection point, the second intersection point, and the sampling points according to an embodiment of the present invention

[0053] Figure 6 It is a schematic diagram of the main pipe roundness correction according to an embodiment of the present invention;

[0054] Figure 7 It is a schematic diagram of the intersecting line weld angle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] It should be noted that if there are directional indications involved in the embodiments of the present invention, such as up, down, left, right, front, back..., then such directional indications are only used to explain the relative positional relationship and movement conditions between components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly. In addition, if there are descriptions such as "first, second", "S1, S2", "step one, step two" in the embodiments of the present invention, then such descriptions are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features or indicating the execution order of the method, etc. Those skilled in the art can understand that all those that do not violate the invention key points under the inventive concept of the invention should be included in the protection scope of the present invention.

[0057] The intersection of multiple cylindrical workpieces is called an intersection curve. When welding the intersection curve, it is necessary to obtain its weld track. However, the existing teaching track welding method has high labor costs and extremely high requirements for processing and fixture accuracy, and it is difficult to adapt to the changes of parts. Although the welding method based on a mathematical model has lower labor costs, it has high requirements for the machining accuracy and fixture accuracy of parts and cannot dynamically adapt to the subtle changes of parts, affecting the welding quality. At the same time, for stainless steel parts, due to their strong reflectivity, the existing machine vision technology is difficult to obtain clear and complete images, so the weld information cannot be accurately extracted, restricting the application of the welding solution based on machine vision. Therefore, as Figure 1 , Figure 2 shown, the present invention provides an intersection curve weld extraction method, including:

[0058] S1: Construct an initial intersection curve weld model;

[0059] Specifically, since it is known that the weld at each intersection curve is formed by the intersection of two cylindrical workpieces, the two cylindrical workpieces after intersection are called intersecting bodies, and the intersection line between them is called the intersection curve. Therefore, an initial intersection curve weld model can be selected to provide a theoretical basis, and then it is optimized by collecting actual parameters, so as to extract the intersection curve weld in the real scene, dynamically adapt to the workpiece processing error and assembly error, and ensure the high precision of the weld track. It should be noted that this step is a preparatory work, which can be pre-constructed and trained, or can be synchronized with any subsequent step, as long as it is constructed before correcting the initial intersection curve weld model.

[0060] Exemplarily, as Figure 3As shown, it is optional but not limited to use a relatively large cylindrical workpiece as the main pipe and a relatively small cylindrical workpiece as the branch pipe to construct an initial intersecting weld model. Set the length direction of the main pipe and the branch pipe as the y-axis direction of the world coordinate system. The axis of the main pipe is e1 with a radius of R, and the axis of the branch pipe is e2 with a radius of r. Arbitrarily select a point on the axis e1 of the main pipe as the origin o1 of the main pipe coordinate system, and arbitrarily select a point on the axis e2 of the branch pipe as the origin o2 of the branch pipe coordinate system. Then, construct the main pipe coordinate system {M} and the branch pipe coordinate system {B} with the origins o1 and o2 respectively, and the main pipe cylindrical equation 1-1 and the branch pipe cylindrical equation 1-2 can be obtained:

[0061]

[0062] Where x m , y m are the coordinates in the main pipe coordinate system, and x b , y b are the coordinates in the branch pipe coordinate system.

[0063] As Figure 4 shown, project the initial intersecting line model onto the XOZ plane of the main pipe. Let the origin distance between o1 and o2 be L, and the axis angle between e1 and e2 be α. According to the angle α between e1 and e2 and the distance L between o1 and o2, the rotation matrix between the main pipe coordinate system {M} and the branch pipe coordinate system {B} can be obtained as shown in Equation 1-3, and the linear transformation relationship between the two can be obtained as shown in Equation 1-4:

[0064]

[0065] X M = RT * X B 1-4

[0066] Where RT is the rotation matrix between the main pipe coordinate system {M} and the branch pipe coordinate system {B}, α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe, X M is the point {x m , y m , z m , 1} on the main pipe cylindrical equation, and X B is the point {x b , y b , z b , 1} on the branch pipe cylindrical equation.

[0067] Substituting any coordinate in the main pipe coordinate system or the branch pipe coordinate system into Equation 1-4 gives:

[0068]

[0069] Where, (x m , ym , z m ), which are the coordinates in the main pipe coordinate system, (x b , y b , z b ), which are the coordinates in the branch pipe coordinate system, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

[0070] According to the prior geometric constraint relationships 1 - 6 of the intersection line, an initial intersection line weld model can be constructed as shown in Equation 1 - 7:

[0071]

[0072] Among them, z m is the coordinate in the main pipe coordinate system, R is the radius of the main pipe, r is the radius of the branch pipe, α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe, and θ is the angle of rotation around the center of the circle.

[0073] In the initial intersection line weld model, the main pipe and the branch pipe are regarded as standard cylindrical workpieces. However, in actual production, due to various factors such as process conditions or environmental impacts, the roundness of the main pipe and the branch pipe may be insufficient, resulting in an elliptical surface, which has a gap compared with the ideal situation. And the assembly error will also affect the calculation results of the mathematical model. Therefore, it is necessary to correct each workpiece that needs to extract the intersection line weld through subsequent steps to obtain the angle α between the axis e1 of the main pipe and the axis e2 of the branch pipe and the distance L between the origin o1 of the main pipe coordinate system and the origin o2 of the branch pipe in each workpiece respectively, so as to eliminate the influence of the assembly error on the model calculation.

[0074] S2: Collect the workpiece contour point cloud to obtain a number of main pipe local point clouds and a number of branch pipe local point clouds;

[0075] Specifically, due to the strong reflection on the surface of the workpiece, it is difficult for the acquisition equipment to clearly and completely reconstruct its surface. Therefore, it is optional but not limited to avoid the strong reflection area, and discretely collect the workpiece contour point cloud through the acquisition equipment to segment and obtain a number of main pipe local point clouds and a number of branch pipe local point clouds; The acquisition equipment includes any equipment that can obtain 3D information of the workpiece surface, such as a line scan camera, a 3D camera, a 3D line laser sensor, etc.

[0076] Preferably, the step of collecting the workpiece contour point cloud to obtain a number of main pipe local point clouds and a number of branch pipe local point clouds may optionally include:

[0077] S21: Collect the workpiece contour point cloud to obtain the coordinates of each point cloud and acquire the curvature of each point cloud;

[0078] S22: Extract the main pipe end face points and the branch pipe end face points according to the coordinates of each point cloud, and obtain the first intersection point between the main pipe and the branch pipe according to the point cloud curvature;

[0079] Specifically, it is optional but not limited to use a line scan camera to scan the surface of the workpiece to obtain the contour point cloud of the workpiece, and then calculate the curvature of each point cloud according to the coordinates of each point cloud. Since the main pipe end face point and the branch pipe end face point are located at the edge of the workpiece, it is optional to respectively obtain the points with the largest coordinates on the x-axis and y-axis, which are the main pipe end face point and the branch pipe end face point. At the same time, the change at the intersection of the main pipe and the branch pipe is the most drastic, so it is optional to obtain the point with the largest curvature, which is the first intersection point P between the main pipe and the branch pipe. I1 。

[0080] Preferably, assuming the equation of the contour curve is z = f(x), it is optional to calculate the curvature of each point cloud according to Equations 2-1, 2-2, and 2-3:

[0081]

[0082] K = {K1, K2…K n} 2-2

[0083] index = argmax(K) 2-3

[0084] Where K i is the curvature of the i-th point in the workpiece contour point cloud, 0 < i ≤ n, and n is the total number of point clouds. is the derivative of the i-th point cloud on the equation of the contour curve, K is the set of curvatures of all point clouds, and index is the first intersection point P between the main pipe and the branch pipe. I1 , and argmax() represents obtaining the maximum value in the set.

[0085] S23: Obtain the second intersection point between the main pipe and the branch pipe according to the prior branch pipe radius and the coordinates of the first intersection point;

[0086] Specifically, it is optional but not limited to perform piecewise linear fitting on the workpiece contour point cloud to obtain the workpiece contour, and then translate the contour line of the branch pipe part 2r in the direction perpendicular to the main pipe contour. At this time, the intersection point of the branch pipe contour and the main pipe contour is the second intersection point P between the main pipe and the branch pipe. I2 As Figure 5 shown.

[0087] S24: Uniformly sample the workpiece contour point cloud according to the main pipe end face point, the branch pipe end face point, and the first intersection point between the main pipe and the branch pipe to obtain a number of main pipe local point clouds and a number of branch pipe local point clouds.

[0088] Specifically, it is optional but not limited to connect the branch pipe end face point and the first intersection point, obtain the normal of the connection line, and move the connection line a distance r in the normal direction to obtain the position of the branch pipe axis. Obtain a number of sampling points P between the main pipe end face point and the first intersection point and on the branch pipe axis. C1 -P 10 As Figure 5As shown in the figure, the contour point clouds of the main pipe or branch pipe are collected at each sampling point along the direction perpendicular to the main pipe or branch pipe, and several local point clouds of the main pipe and several local point clouds of the branch pipe can be obtained.

[0089] S3: Fit the ellipse equation to each local point cloud to obtain the center of the circle corresponding to each local point cloud;

[0090] Specifically, it is optional but not limited to set the length direction of the main pipe or branch pipe as the z direction of the corresponding coordinate system, and the cross-sectional equation of the main pipe or branch pipe can be obtained as shown in Equation 3-1:

[0091] Ax 2 +Bxy+Cy 2 +Dx+Ey=1 3-1

[0092] Among them, A, B, C, D, and E are the parameters of the cross-sectional equation. Then, the objective function 3-2 is constructed according to Equation 3-1, and each local point cloud is substituted into the objective function for iterative optimization to obtain the values of the cross-sectional equation parameters corresponding to each local point cloud:

[0093]

[0094] Among them, argmin() means to obtain the values of the cross-sectional equation parameters A, B, C, D, and E when F takes the minimum value.

[0095] Finally, the values of the cross-sectional equation parameters corresponding to each local point cloud can be substituted into the ellipse calculation formulas 3-3, 3-4, 3-5, and 3-6 to obtain the center coordinates corresponding to each local point cloud:

[0096] x p =(B*E-2C*D) / (4*A*C-B 2 ) 3-3

[0097] y p =(B*D-2*A*E) / (4*A*C-B 2 ) 3-4

[0098]

[0099] Among them, (x p , y p ) is the center coordinate, a is the value of the major axis, and b is the value of the minor axis.

[0100] S4: Fit a straight line according to the center of the circle to obtain the axis equations of the main pipe and the branch pipe, and obtain the surface parameters of the main pipe according to each ellipse equation, so as to update the initial intersecting line weld model according to the axis equation and the surface parameters of the main pipe to obtain an optimized intersecting line model;

[0101] Specifically, optionally but not limited to, performing a linear fitting on the centers of the main pipe local point cloud and the branch pipe local point cloud, the linear equations of the main pipe and the branch pipe can be obtained, and the arithmetic mean values of the parameters of each ellipse equation are calculated to construct the main pipe elliptic cylinder equation, and the surface parameters of the main pipe are obtained, so as to update the initial intersection weld model according to the axis equation and the main pipe surface parameters to obtain an optimized intersection model.

[0102] S41: Fit a straight line based on the center coordinates to obtain the axis equations of the main pipe and the branch pipe;

[0103] Specifically, optionally establish a space straight line equation as shown in Equation 4-1:

[0104]

[0105] Transform Equation 4-1 to obtain the objective function 4-2:

[0106]

[0107] Solve the objective function 4-2 to obtain Equations 4-3 and 4-4:

[0108]

[0109] Among them, (x0, y0, z0) is the coordinate of any center, m, n, t are the parameters of the axis equation, (x i , y i , z i ) is the coordinate of the i-th center, 0 < i ≤ n, n is the number of centers corresponding to the main pipe local point cloud or the number of centers corresponding to the branch pipe local point cloud, argmin() means that when F x or F y takes the minimum value, obtain the values of the axis equation parameters m, n, t.

[0110] S42: Obtain the arithmetic mean value of the parameters of each cross-section equation, construct the main pipe elliptic cylinder equation, and obtain the main pipe surface parameters;

[0111] Specifically, optionally but not limited to obtaining the arithmetic mean values of the cross-section equation parameters A, B, C, D, E corresponding to all the main pipe local point clouds in step S3, the final main pipe elliptic cylinder equation can be constructed:

[0112]

[0113] Among them, the main pipe surface parameters are respectively the arithmetic mean values of the cross-section equation parameters A, B, C, D, E.

[0114] S43: Obtain the actual elliptical contour according to the main pipe elliptical cylinder equation, and obtain the distance between any point on the actual elliptical contour and the corresponding center according to the first intersection point, the second intersection point and the main pipe surface parameters;

[0115] Preferably, the specific steps of obtaining the actual elliptical contour according to the main pipe elliptical cylinder equation and obtaining the distance between any point on the actual elliptical contour and the corresponding center may include:

[0116] S431: Determine the actual elliptical contour according to the main pipe elliptical cylinder equation;

[0117] Specifically, it is optional but not limited to obtaining any cross-section according to the main pipe elliptical cylinder equation in step S42, and the actual elliptical contour can be obtained.

[0118] Exemplarily, the actual elliptical contour equation can be optionally expressed as Equation 4-6:

[0119]

[0120] Wherein, Z1 and Z2 are the heights of the top surface and the bottom surface of the elliptical cylinder, and z is the height at which the actual elliptical contour is located in the elliptical cylinder.

[0121] S432: Substitute the main pipe surface parameters into the elliptical calculation formula to obtain the major and minor axes of the actual elliptical contour;

[0122] Specifically, it is optional but not limited to substituting the main pipe surface parameters into Equations 3-5 and 3-6 in step S3, and the major axis value a m and the minor axis value b m of the main pipe elliptical equation can be obtained, that is, the major and minor axes of the actual elliptical contour.

[0123] S433: Connect the first intersection point and the second intersection point with the corresponding center to obtain the first connection line and the second connection line;

[0124] S434: Obtain the angle value between the first connection line, the second connection line and the major axis, and obtain the angle difference between the two;

[0125] S435: Substitute the angle difference into the angle conversion formula 4-8 to obtain the intersection angle between the connection line between any point on the intersection line of the actual elliptical contour and the corresponding center and the major axis;

[0126] S436: Substitute the major and minor axes of the main pipe elliptical equation and the intersection angle into the distance calculation formula 4-6 to obtain the distance from any point on the actual elliptical contour to the center of the circle.

[0127] Specifically, since the branch pipe has a small volume, it can be directly regarded as a right circular cylinder. The ideal cross-section of the main pipe can be obtained from the CAD model or engineering documents, which is an ideal circular contour. According to the equation of the main pipe elliptic cylinder, the actual cross-section in the actual scenario can be obtained, which is an actual elliptical contour. Thus, based on the positional relationship between the points on the ideal circular contour and the actual elliptical contour, the initial intersecting line weld model is optimized to obtain the optimized intersecting line model.

[0128] For example, as Figure 6 shown, point P is an arbitrary point on the intersecting line of the ideal circular contour, and point P2 is the point on the intersecting line of the actual elliptical contour. Optionally, the distance R' from any point on the actual elliptical contour to the center of the circle can be calculated according to the distance calculation formula 4-7:

[0129]

[0130] where a m and b m respectively represent the major axis value and minor axis value of the equation of the main pipe elliptic cylinder, and γ is the angle between the line connecting point P2 and the center of the circle OP2 and the major axis of the ellipse. As Figure 7 shown, P I1 represents the first intersection point between the main pipe and the branch pipe, and P I2 represents the second intersection point between the main pipe and the branch pipe. Thus, the angle γ between the line connecting point P2 and the center of the circle OP2 and the major axis of the ellipse can be calculated according to Equation 4-8:

[0131]

[0132] where γ1 and γ2 respectively represent the values of the angles between P I1 O and P I2 O and the major axis, and θ is the prior branch pipe angle parameter.

[0133] S44: Obtain the calculation formula for the z-axis coordinate of each point in the world coordinate system according to the distance from any point on the actual elliptical contour to the corresponding center of the circle, and substitute it into the initial intersecting line weld model to obtain the optimized intersecting line model;

[0134] Specifically, optionally but not limited to, according to the distance R' from any point on the ellipse to the center of the circle, the calculation method for the z coordinate of the corrected intersecting line weld is obtained:

[0135]

[0136] where z is the z coordinate of the intersecting line weld, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

[0137] Thus, substituting Equation 4-9 into the initial intersecting line weld model, the corrected intersecting line model 4-10 is obtained:

[0138]

[0139] Among them, (x, y, z) are the coordinates of the intersection weld points in the world coordinate system, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

[0140] S45: Calculate the compensation amount Δz based on the trajectory result, and then correct the optimized intersection curve model according to the compensation amount to obtain the final intersection curve model.

[0141] Preferably, if there is a large amount of data for the intersection curve workpiece, the compensation amount Δz can also be calculated based on the trajectory result, and the functional relationship can be obtained through data fitting to correct the mathematical model to obtain the final intersection curve model formula 4-11:

[0142]

[0143] Among them, the f function is a linear function, which can be optionally expressed as formula 4-12:

[0144] Δz = k1θ + k2α + k3R + k4r 4-12

[0145] Among them, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe; then the coefficients are solved by the least squares method to obtain the compensation amount Δz.

[0146] S5: Obtain the angle between the axis equations of the main pipe and the branch pipe and the transformation matrix, substitute them into the optimized intersection curve model to obtain the parametric equation of the intersection curve, and extract the intersection weld.

[0147] Specifically, the included angle value α2 between the two can be obtained according to the axis equation e1 of the main pipe and the axis equation e2 of the branch pipe obtained in step S41, and the transformation matrix RT2 between e1 and e2 is calculated, and then substituted into the optimized intersection curve model to obtain the final parametric equation of the intersection curve 5-1:

[0148]

[0149] Preferably, since the intersection weld may be offset in the z-axis direction in the actual scenario, the parametric equation of the intersection curve can be corrected according to the compensation amount Δz to obtain the corrected parametric equation of the intersection curve 5-2:

[0150]

[0151] More specifically, after obtaining the final parametric equation of the intersection curve, the coordinates of the intersection curve weld or several weld points on the intersection curve weld can be calculated based on the connection lines between the first intersection point, the second intersection point, and the center of the actual elliptical contour between the main pipe and the branch pipe. Therefore, this step further includes:

[0152] S51: Substitute the branch pipe angle parameter into the parametric equation of the intersection curve to obtain the intersection curve weld;

[0153] Specifically, the branch pipe angle parameter θ can be optionally substituted into the final parametric equation of the intersection curve to extract the intersection curve weld in the actual scenario.

[0154] Preferably, after obtaining the branch pipe angle parameter, it may also optionally include:

[0155] S51: Divide the branch pipe angle parameter evenly to obtain several angle values, and substitute them into the parametric equation of the intersection curve in sequence to obtain several intersection curve weld points.

[0156] Specifically, since robotic welding generally requires specific welding points, several angle values can be obtained by evenly dividing the branch pipe angle parameter according to the number of weld points to be acquired as needed, and then substituting them into the parametric equation of the intersection curve in sequence, so as to obtain several corresponding intersection curve weld points, enabling the robot to weld the surface of the workpiece to be welded according to each intersection curve weld point.

[0157] In this embodiment, a method for extracting the intersection curve weld of the present invention is given. By constructing an initial intersection curve weld model to adapt to the changes of the part, the adaptability of the method is improved. Then, the contour point cloud of the workpiece is collected to obtain several local point clouds of the main pipe and several local point clouds of the branch pipe. The elliptical equations are respectively fitted to each local point cloud to obtain the centers corresponding to each local point cloud. By collecting the contour point cloud of the workpiece, the influence of the reflective area of the workpiece on the acquisition of the point cloud of the workpiece by the acquisition device is avoided, and the acquisition accuracy is improved. Then, the axis equations of the main pipe and the branch pipe are obtained by fitting straight lines according to the centers, and the surface parameters of the main pipe are obtained according to each elliptical equation, so as to update the initial intersection curve weld model according to the axis equations and the surface parameters of the main pipe to obtain an optimized intersection curve model. Finally, the included angle and transformation matrix between the axis equations of the main pipe and the branch pipe are obtained and substituted into the optimized intersection curve model to obtain the parametric equation of the intersection curve, so as to extract the intersection curve weld. It solves the problems of low machining accuracy, insufficient adaptability in the prior art, and low acquisition accuracy caused by high reflectivity of the workpiece, which affects the welding quality.

[0158] On the other hand, the present invention also provides a computer storage medium storing executable program code; the executable program code is used to execute any of the above intersection curve weld extraction methods.

[0159] On the other hand, the present invention also provides a terminal device, including a memory and a processor; the memory stores program code executable by the processor; the program code is used to execute any of the above-mentioned intersecting line weld extraction methods.

[0160] Exemplarily, the program code can be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the program code in the terminal device.

[0161] The terminal device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that the terminal device may further include input / output devices, network access devices, a bus, etc.

[0162] The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0163] The memory may be an internal storage unit of the terminal device, such as a hard disk or a memory. The memory may also be an external storage device of the terminal device, such as a plug-in hard disk equipped on the terminal device, a SmartMedia Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory may also include both an internal storage unit and an external storage device of the terminal device. The memory is used to store the program code and other programs and data required by the terminal device. The memory may also be used to temporarily store data that has been output or will be output.

[0164] The above computer storage medium and terminal device are created based on the above intersecting line weld extraction method, and their technical effects and beneficial effects will not be elaborated here. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0165] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for extracting an intersection weld, characterized in that, Including: Construct an initial intersecting weld seam model; Collect the workpiece contour point cloud to obtain several local point clouds of the main pipe and several local point clouds of the branch pipe; Fit the ellipse equation to each local point cloud to obtain the center of the circle corresponding to each local point cloud; Fit a straight line according to the center of the circle to obtain the axis equations of the main pipe and the branch pipe, and obtain the main pipe surface parameters according to each ellipse equation, so as to update the initial intersecting weld seam model according to the axis equations and the main pipe surface parameters to obtain an optimized intersecting line model; Obtain the included angle and transformation matrix between the axis equations of the main pipe and the branch pipe, substitute them into the optimized intersecting line model to obtain the parametric equation of the intersecting line, so as to extract the intersecting weld seam.

2. The method according to claim 1, characterized in that The steps of constructing the initial intersecting weld seam model include: Obtain the axis of the main pipe, the radius of the main pipe, the axis of the branch pipe, the radius of the branch pipe, and obtain the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system according to the axis of the main pipe and the axis of the branch pipe; Construct the main pipe coordinate system and the branch pipe coordinate system according to the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system, and construct the main pipe cylinder equation and the branch pipe cylinder equation according to the radius of the main pipe and the radius of the branch pipe; Obtain the origin distance between the origin of the main pipe coordinate system and the origin of the branch pipe coordinate system, and the axis included angle between the axis of the main pipe and the axis of the branch pipe, so as to obtain the rotation matrix between the main pipe coordinate system and the branch pipe coordinate system according to the origin distance and the axis included angle; Obtain the linear transformation relationship between the main pipe coordinate system and the branch pipe coordinate system according to the rotation matrix, the main pipe cylinder equation and the branch pipe cylinder equation, so as to construct the initial intersecting weld seam model according to the linear transformation relationship and the prior geometric constraint relationship of the intersecting line.

3. The method according to claim 1, wherein The steps of collecting the workpiece contour point cloud to obtain several local point clouds of the main pipe and several local point clouds of the branch pipe include: Collect the workpiece contour point cloud to obtain the coordinates of each point cloud and obtain the curvature of each point cloud; Extract the end face points of the main pipe and the end face points of the branch pipe according to the coordinates of each point cloud, and obtain the first intersection point between the main pipe and the branch pipe according to the point cloud curvature; Obtain the second intersection point between the main pipe and the branch pipe according to the prior branch pipe radius and the coordinates of the first intersection point; Perform uniform sampling on the workpiece contour point cloud according to the main pipe end face points, the branch pipe end face points, and the first intersection point between the main pipe and the branch pipe to obtain several local point clouds of the main pipe and several local point clouds of the branch pipe.

4. The method according to claim 3, characterized in that, The steps of obtaining the optimized intersecting line model include: Fit a straight line according to the center of the circle coordinates to obtain the axis equations of the main pipe and the branch pipe; Obtain the arithmetic mean of the parameters of each cross-section equation, construct the main pipe elliptic cylinder equation, and obtain the main pipe surface parameters; Obtain the actual elliptical contour according to the main pipe elliptic cylinder equation, and obtain the distance between any point on the actual elliptical contour and the corresponding center of the circle according to the first intersection point, the second intersection point and the main pipe surface parameters; Obtain the calculation formula of the z-axis coordinate of each point in the world coordinate system according to the distance between any point on the actual elliptical contour and the corresponding center of the circle, and substitute it into the initial intersecting weld seam model to obtain the optimized intersecting line model.

5. The method according to claim 4, characterized in that, The steps of obtaining the actual elliptical contour according to the main pipe elliptic cylinder equation, and obtaining the distance between any point on the actual elliptical contour and the corresponding center of the circle according to the first intersection point, the second intersection point and the main pipe surface parameters include: Determine the actual elliptical contour according to the main pipe elliptic cylinder equation; Substitute the main pipe surface parameters into the ellipse calculation formula to obtain the major and minor axes of the actual elliptical contour; Connect the first intersection point and the second intersection point to the corresponding center of the circle to obtain a first connection line and a second connection line; Obtain the angular values between the first connection line, the second connection line and the major axis, and obtain the angular difference between them; Substitute the angular difference into the angular conversion formula to obtain the intersection angle between the connection line of any point on the intersection line of the actual elliptical contour and the corresponding center of the circle and the major axis; Substitute the major and minor axes of the actual elliptical contour and the intersection angle into the distance calculation formula to obtain the distance from any point on the actual elliptical contour to the center of the circle.

6. The method according to claim 4, wherein The optimized intersection line model is expressed as: Where, (x, y, z) are the coordinates of the intersection line weld point in the world coordinate system, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

7. The method according to claim 6, characterized in that After obtaining the optimized intersection line model, it further includes: Back-calculate the compensation amount according to the trajectory result, so as to correct the optimized intersection line model according to the compensation amount to obtain the final intersection line model: Where, the f function is a linear function, expressed as Equation 4-12: Δz = k1θ + k2α + k3R + k4r 4-12 Where, Δz is the compensation amount, r is the radius of the branch pipe, R is the radius of the main pipe, θ is the branch pipe angle parameter, and α is the angle between the axis e1 of the main pipe and the axis e2 of the branch pipe.

8. The method according to claim 7, wherein Extract the intersection line weld, including: Substitute the branch pipe angle parameter into the intersection line parameter equation to obtain the intersection line weld; Or, evenly divide the branch pipe angle parameter to obtain several angular values, and substitute them into the intersection line parameter equation in turn to obtain several intersection line weld points.

9. A computer storage medium, characterized in that, Store executable program code; the executable program code is used to execute the intersection line weld extraction method according to any one of claims 1-8.

10. A terminal device, characterized in that, Include a memory and a processor; the memory stores program code executable by the processor; the program code is used to execute the intersection line weld extraction method according to any one of claims 1-8.

Images