Multi-beam laser weld seam identification and welding path planning method for cylinder and cover plate welding encapsulation

Abstract

Disclosed in the present invention is a multi-beam laser weld seam identification and welding path planning method for cylinder and cover plate welding encapsulation, comprising: simultaneously projecting n parallel line-structured laser stripes onto the surfaces of a cylinder and a cover plate that are to be welded, n being greater than or equal to 2, and photographing and acquiring an image containing all the line-structured laser stripes; identifying inflection point coordinates of all the line-structured laser stripes in the acquired image, and fitting the outer circle of the cover plate and the inner circle of an outer cylinder on the basis of the identified inflection point coordinates; calculating the inner wall circle of the cylinder on the basis of the inner circle of the outer cylinder and the wall thickness of the cylinder, and taking the center ellipse of a figure between the inner wall circle of the cylinder and the outer circle of the cover plate as a welding trajectory; and taking the widest portion of the overlapping area between the cover plate and the cylinder wall as the starting point of the welding trajectory. The present invention does not require scanning a workpiece by using line-structured laser to obtain a three-dimensional surface profile, and the weld seam center path can be directly identified from a single image, thereby achieving high efficiency.

Description

A Multi-Beam Laser Weld Seam Recognition and Welding Path Planning Method for Welding and Encapsulation of Cylindrical Cover Plates Technical Field

[0001] This invention relates to the field of welding automation technology, and in particular to a multi-beam laser weld seam recognition and welding path planning method for welding and packaging cylindrical cover plates. Background Technology

[0002] Cylindrical structures are widely used in various pressure vessels and reaction vessels in industries such as shipbuilding, chemical engineering, and military equipment. In recent years, with the increasing demand for lightweight industrial containers, the need for small-sized or thin-walled cylindrical structural components has grown significantly. Cylindrical containers typically require high strength and sealing performance. The welding of small-sized or thin-walled cylindrical cover plates is characterized by minute weld seams and high welding precision. This type of welding often involves a lock-bottom butt joint, where a certain width is recessed into the inner wall of the cylinder end to form a step. The cover plate is then installed within this step to complete the welded sealing.

[0003] However, because the central axes of the cylinder and the cover plate cannot be guaranteed to coincide when clamping the cylinder wall and cover plate before welding, positional errors occur between the cover plate and the cylinder, causing the overlapping area of ​​the cover plate and the cylinder wall edge to deviate from the preset welding trajectory. Since the lap joint is located below the cover plate and is blocked by it, this deviation cannot be directly observed. For welding ultra-thin-walled cylinders, to reduce the heat impact of welding, a short-duration, high-power, highly concentrated welding heat source is mainly used to heat the metal to be welded. The deviation between the area to be welded and the preset welding trajectory will seriously affect the welding of the thin-walled cylinder cover plate, making it unable to meet the strength and sealing requirements, and even leading to welding defects and failure of the overall welded structure. Therefore, the welding trajectory should be aligned with the center of the lap area between the cylinder wall and the cover plate. Furthermore, the high heat input during welding will cause thermal deformation of the cover plate. The starting and ending points of such arc welds are at the same location, and repeated heating during welding easily causes deformation, affecting the overall structure of the part. If the welding starting point is set at a narrow lap width between the cover plate and the cylinder wall, repeated heating will further increase the likelihood of thermal deformation. Therefore, it is necessary to plan the starting point of the welding trajectory.

[0004] Currently, single-line laser scanning is mainly used to identify weld seams. However, for the encapsulation and welding of small-sized or thin-walled cylindrical cover plates, the welding area is small, and continuous scanning with single-line laser is time-consuming, labor-intensive, and has low accuracy, which significantly reduces production efficiency. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a multi-beam laser weld seam identification and welding path planning method for the welding and encapsulation of cylindrical cover plates.

[0006] Technical solution: The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation described in this invention includes the following steps:

[0007] Simultaneously project onto the surfaces of the cylinder and cover plate to be welded Parallel line structure laser stripes, Capture and acquire images of all line structure laser stripes;

[0008] Identify the inflection point coordinates of all line structure laser stripes in the acquired image, and fit the outer circle of the cover plate and the inner circle of the outer cylinder based on the identified inflection point coordinates;

[0009] The inner wall circle of the cylinder is calculated based on the inner circle of the outer cylinder and the wall thickness of the cylinder. The ellipse between the inner wall circle of the cylinder and the outer circle of the cover plate is taken as the welding trajectory.

[0010] The widest point where the cover plate overlaps with the cylindrical wall is taken as the start and end point of the welding trajectory.

[0011] Furthermore, the parallel line structure laser stripes are generated by a line structure laser, and the image of the line structure laser stripes is captured by a camera at a set angle to the laser projection direction. The geometric features of the line structure laser stripes are then reconstructed based on the principle of triangulation.

[0012] Furthermore, the inflection points include outer inflection points and inner inflection points. The outer inflection point is the intersection of the linear laser stripe with the cylindrical boss and the gap's adjacent surface. The inner inflection point is the intersection of the linear laser stripe with the cover plate and the gap's adjacent surface. The total number of inflection points is... .

[0013] Furthermore, according to The outer inflection point fits the inner circle of the outer cylinder. equation:

[0014]

[0015] in, , The coordinates of the inner circle of the outer cylinder are: The radius of the inner circle of the outer cylinder is... , The x and y coordinates of a point on the inner circle of the outer cylinder;

[0016] according to The inner inflection point fits the outer circle of the cover plate. equation:

[0017]

[0018] in, , The coordinates of the center of the outer circle of the cover plate; The outer radius of the cover plate is 1. , The coordinates of the points on the outer circle of the cover plate are x and y.

[0019] Furthermore, the equation for the inner wall circle of the cylinder is:

[0020]

[0021] in, , The coordinates of the inner circle of the outer cylinder are: , Let x and y be the coordinates of a point on the inner wall circle of the cylinder. Let t be the inner radius of the outer cylinder, and t is obtained by subtracting the thickness of the cylinder boss from the total wall thickness of the cylinder.

[0022] Furthermore, the welding trajectory calculation method is as follows:

[0023] First, connect the center of the inner wall of the cylinder. and the outer center of the cover plate ,calculate The four intersection points of the line with the outer circle of the cover plate and the inner circle of the cylinder are denoted as follows: , , , ,Pick , midpoint and , midpoint The endpoints of the major axis of the ellipse; passing through the centers of the two circles. and midpoint The perpendicular line intersects the two circles at the following points: , , , ;Pick , midpoint and , midpoint The endpoints of the minor axis of the ellipse; according to , , , Calculate the ellipse, that is, the central ellipse of the figure between the inner wall circle of the cylinder and the outer circle of the cover plate, as the welding trajectory.

[0024] Furthermore, if Then the start and end points of the welding trajectory are Conversely, it is .

[0025] The system corresponding to the method includes:

[0026] The laser stripe image acquisition unit is used to simultaneously project images onto the surfaces of the cylinder and the cover plate to be welded. Parallel line structure laser stripes, Capture and acquire images of all line structure laser stripes;

[0027] The fitting unit is used to identify the inflection point coordinates of all line structure laser stripes in the acquired image, and to fit the outer circle of the cover plate and the inner circle of the outer cylinder based on the identified inflection point coordinates.

[0028] The welding trajectory calculation unit is used to calculate the inner wall circle of the cylinder based on the inner circle of the outer cylinder and the cylinder wall thickness, and takes the central ellipse of the figure between the inner wall circle of the cylinder and the outer circle of the cover plate as the welding trajectory.

[0029] The welding trajectory start point determination unit is used to determine the widest point of the overlapping part between the cover plate and the cylindrical wall as the start and end points of the welding trajectory.

[0030] An electronic device for storing and executing the method includes:

[0031] Memory containing executable program code;

[0032] A processor coupled to the memory;

[0033] The processor calls the executable program code stored in the memory to execute the steps of the multi-beam laser weld seam recognition and welding path planning method for cylindrical cover plate welding and encapsulation.

[0034] A computer-readable storage medium for storing and executing the method, the computer-readable storage medium storing computer instructions, which, when invoked, are used to execute the steps of the multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation.

[0035] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: It takes into account the positional error caused by the misalignment of the central axes of the cylinder and the cover plate, overcomes the problem that the lap joint is covered by the cover plate and the deviation of different axes cannot be directly observed, and makes reasonable planning of the welding start and end points, which can reduce the generation of welding defects; and only one photo is needed to identify the weld and plan the welding trajectory, which significantly improves production efficiency. It is particularly suitable for welding thin-walled cylindrical cover plates or micro-sized cylindrical cover plates with high welding precision requirements. Attached Figure Description

[0036] Figure 1 is a flowchart illustrating the method described in this invention;

[0037] Figure 2 is a schematic diagram of a multi-beam laser weld seam recognition system for cylindrical cover plate welding and encapsulation provided in an embodiment of the present invention.

[0038] Figure 3 is a schematic diagram of a cylindrical cover plate workpiece to be welded according to an embodiment of the present invention;

[0039] Figure 4 is an image obtained by a multi-beam laser weld seam recognition and welding path planning method for welding and packaging cylindrical cover plates provided in an embodiment of the present invention.

[0040] Figure 5 is a schematic diagram of fitting the inner circle of the outer cylinder and the outer circle of the cover plate to a multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation provided in an embodiment of the present invention.

[0041] Figure 6 is a schematic diagram of the geometric features of the end of the cylinder to be welded, provided in an embodiment of the present invention, for a multi-beam laser weld seam identification and welding path planning method for welding and encapsulating cylindrical cover plates.

[0042] Figure 7 is a schematic diagram of welding trajectory calculation for a multi-beam laser weld seam recognition and welding path planning method for cylindrical cover plate welding and encapsulation provided in an embodiment of the present invention.

[0043] Figure 8 is a schematic diagram of a cylindrical cover plate welding process provided in an embodiment of the present invention. Embodiments of the present invention

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] This invention uses a multi-beam laser detection method to identify the cylindrical cover plate to be welded. Only one image needs to be taken to identify the weld and plan the welding trajectory. This is of great significance and value for improving the production efficiency and welding quality of thin-walled cylindrical cover plate welding.

[0047] As shown in Figure 1, the multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to the present invention includes the following steps:

[0048] S1, simultaneously project onto the surfaces of the cylinder and cover plate to be welded. ( Parallel line structure laser stripes. A typical scenario is shown in Figure 2, where the line structure laser generator 1 projects parallel line structure laser stripes onto the surface of the cylinder and cover plate 3 to be welded. The structure of the workpiece to be welded is shown in Figure 3, consisting of an outer cylinder 31 and a cover plate 32. There is a gap 33 between the cover plate and the outer cylinder. The inner wall 34 of the cylinder is blocked by the cover plate 32. The thickness of the cylinder wall is represented as 35, and the thickness of the cylinder boss is 36.

[0049] S2. As shown in Figure 2, a camera 2 at a set angle to the laser projection direction captures and acquires an image of the line-structured laser stripes, as shown in Figure 4, consisting of three parallel line-structured laser stripes 5. The angle between the camera and the incident direction of the line-structured laser is determined according to the actual situation, preferably to capture clear line-structured laser stripes; in this embodiment, 30° is used. The computer 4 processes the acquired image data, extracts the coordinates of high-brightness pixels in the image, and reconstructs the geometric features of the laser stripes based on the principle of triangulation.

[0050] S3. Identify the inflection point coordinates of the laser stripes in the acquired image. The relationship between the number of inflection points m and the number of stripes n is m=4n. Inflection points include outer inflection points and inner inflection points. The outer inflection point is the intersection of the line-structured laser stripe with the adjacent surface of the cylindrical boss and the gap. The inner inflection point is the intersection of the line-structured laser stripe with the adjacent surface of the cover plate and the gap. As shown in Figure 5, the three stripes projected onto the cover plate surface result in 12 inflection points. Identify the inflection points in the image. , , , , , , , , , , , There are a total of 12 points. The geometric features of the end of the cylinder to be welded are shown in Figure 6, which consists of the inner circle of the outer cylinder 6, the outer circle of the cover plate 7, the inner wall circle of the cylinder 8, and the outer circle of the outer cylinder 9. 10 is the welding trajectory.

[0051] S4. Fit equation 6 for the inner circle of the outer cylinder based on the outer inflection point, and equation 7 for the outer circle of the cover plate based on the inner inflection point. The specific implementation is shown in Figure 5. , , , , , Point fitting equation for the inner circle of the outer cylinder (6 equations):

[0052]

[0053] in, , The coordinates of the inner circle of the outer cylinder are: The radius of the inner circle of the outer cylinder is... , The x and y coordinates are the coordinates of a point on the inner circle of the outer cylinder.

[0054] according to , , , , , Point fitting equation for the outer circle of the cover plate (7 equations):

[0055]

[0056] in, , Let these be the coordinates of the center of the outer circle of the cover plate. The outer radius of the cover plate is 1. , The coordinates of the points on the outer circle of the cover plate are x and y.

[0057] S5. Calculate the equation of the inner wall circle 8 of the cylinder:

[0058]

[0059] in, , Let t be the x and y coordinates of a point on the inner wall of the cylinder, as shown in Figure 6. t is obtained by subtracting the thickness of the cylinder boss 36 from the cylinder wall thickness 35.

[0060] S6. Calculate the welding trajectory 10, as shown in Figure 7. When the cover plate and the cylinder are not coaxial, the welding trajectory 10 should be an ellipse. The welding trajectory 10 is calculated as follows: First, connect the centers of the inner walls of the cylinder. and the outer center of the cover plate ,calculate The line intersects the two circles at four points. , , , ,Pick , midpoint and , midpoint Let A be the endpoint of the major axis of the ellipse. Draw a line through the center of the two circles. A perpendicular line intersecting the two circles at a point. , , , .Pick , midpoint and , midpoint This is the endpoint of the minor axis of the ellipse. According to... , , , Calculate the ellipse.

[0061] S7. Determine the start and end points of the welding path. If Then the starting and ending points of the welding trajectory are 11. Conversely, it is .

[0062] As shown in Figure 8, the cylindrical cover plate encapsulation welding method provided in this embodiment is laser welding. Laser 12 penetrates the cover plate and fuses it with the cylindrical wall. Since the inner wall of the cylinder at point 13 and the overlapping portion between the cylinder wall and the cover plate are obscured by the cover plate, the overlapping portion cannot be directly observed and the welding trajectory cannot be planned. Therefore, it is necessary to obtain the inner circle contour of the outer cylinder. The inner circle of the cylinder and the inner circle of the outer cylinder are concentric, and the difference in radii between the two circles is the difference between the cylinder wall thickness and the wall thickness of the area to be welded. Based on this, the equation of the inner circle of the cylinder is derived. The equation of the outer circle of the cover plate is obtained, and an ellipse located inside the outer circle of the cover plate and in the middle of the outer region of the inner circle of the cylinder is taken as the welding trajectory. This ensures that the weld is always located at the center of the overlapping area between the cover plate and the cylinder wall. The starting and ending points of the elliptical welding trajectory are located at the same position. During the welding process, it is repeatedly heated, resulting in a large heat-affected zone. If the starting point is set at a narrower position in the overlapping portion between the cover plate and the cylinder wall, it is more likely to cause severe thermal deformation, affecting the welding quality. Therefore, the widest point of overlap between the cover plate and the cylindrical wall is selected as the starting and ending point of welding.

[0063] The method proposed in this invention takes into account the positional error caused by the misalignment of the central axes of the cylinder and the cover plate due to assembly, thereby reducing welding defects. It is particularly suitable for welding cylindrical cover plates with high welding precision requirements or welding micro-sized cylindrical cover plates. Compared with the prior art, this invention does not require the use of line structure laser to scan the workpiece to obtain the three-dimensional contour of the surface; a single image can directly identify the center path of the weld, resulting in high efficiency.

[0064] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. [Amended according to Rule 26, 16.10.2025] A method for multi-beam laser weld seam identification and welding path planning for cylindrical cover plate welding and encapsulation, characterized in that, Includes the following steps: Simultaneously project n parallel line structured laser stripes onto the surface of the cylinder and cover plate to be welded, n≥2, and capture and acquire images of all line structured laser stripes; Identify the inflection point coordinates of all line structure laser stripes in the acquired image, and fit the outer circle of the cover plate and the inner circle of the outer cylinder based on the identified inflection point coordinates; The inner circle of the cylinder is calculated based on the inner circle of the outer cylinder and the cylinder wall thickness. The ellipse between the inner circle of the cylinder and the outer circle of the cover plate is taken as the welding trajectory. The calculation method for the welding trajectory is as follows: First, connect the center O of the inner wall of the cylinder. i and the outer circle center O of the cover plate r Calculate O i O r The four intersection points of the line with the outer circle of the cover plate and the inner circle of the cylinder are denoted as A1, B1, A2, and B2, respectively. The midpoint C1 of A1 and B1 and the midpoint C2 of A2 and B2 are taken as the endpoints of the major axis of the ellipse; the line passes through the center O of the two circles. i and O r Midpoint as O i O r The perpendicular line intersects the two circles at points A3, B3, A4, and B4 respectively; the midpoints C3 and C4 of A3 and B3 and the midpoints C4 of A4 and B4 are taken as the endpoints of the minor axis of the ellipse; the ellipse is calculated based on C1, C2, C3, and C4, which is the central ellipse of the figure between the inner wall circle of the cylinder and the outer circle of the cover plate, and is used as the welding trajectory. The widest point where the cover plate overlaps with the cylindrical wall is taken as the start and end point of the welding trajectory.

2. The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to claim 1, characterized in that, The parallel line structure laser stripes are generated by a line structure laser. The image of the line structure laser stripes is captured by a camera at a set angle to the laser projection direction, and the geometric features of the line structure laser stripes are restored according to the principle of triangulation.

3. The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to claim 1, characterized in that, The inflection points include outer inflection points and inner inflection points. The outer inflection point is the intersection of the linear laser stripe with the adjacent surface of the cylindrical boss and the gap. The inner inflection point is the intersection of the linear laser stripe with the adjacent surface of the cover plate and the gap. The total number of inflection points is... .

4. [Amended according to Rule 26, 16.10.2025] The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to claim 3 is characterized in that, Fit the inner circle C of the outer cylinder based on 2*n outer inflection points. o equation: Where, x o y o Let R be the coordinates of the center of the inner circle of the outer cylinder. o Let x1 be the radius of the inner circle of the outer cylinder, and y1 be the x and y coordinates of a point on the inner circle of the outer cylinder. The outer circle C of the cover plate is fitted based on 2*n inner inflection points. r equation: Where, x r y r R represents the coordinates of the center of the outer circle of the cover plate. r Let x2 be the radius of the outer circle of the cover plate, and y2 be the x and y coordinates of points on the outer circle of the cover plate.

5. [Amended according to Rule 26, 16.10.2025] The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to claim 1 is characterized in that, The equation of the circle on the inner wall of the cylinder is: (x3 - x0) 2 +(y3-y0) 2 =(R o -t) 2 Where, x o y o Let x3 and y3 be the coordinates of the center of the inner circle of the outer cylinder, and let R be the x and y coordinates of points on the inner wall of the cylinder. o Let t be the inner radius of the outer cylinder, and t is obtained by subtracting the thickness of the cylinder boss from the total wall thickness of the cylinder.

6. The multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation according to claim 1, characterized in that, like Then the start and end points of the welding trajectory are Conversely, it is .

7. [Amended according to Rule 26, 16.10.2025] A multi-beam laser weld seam recognition and welding path planning system for cylindrical cover plate welding and encapsulation, characterized in that, include: The laser stripe image acquisition unit is used to simultaneously project n parallel line structure laser stripes onto the surface of the cylinder and cover plate to be welded, n≥2, and capture and acquire images of all line structure laser stripes. The fitting unit is used to identify the inflection point coordinates of all line structure laser stripes in the acquired image, and to fit the outer circle of the cover plate and the inner circle of the outer cylinder based on the identified inflection point coordinates. The welding trajectory calculation unit is used to calculate the inner wall circle of the cylinder based on the inner circle of the outer cylinder and the cylinder wall thickness. The central ellipse of the figure between the inner wall circle of the cylinder and the outer circle of the cover plate is taken as the welding trajectory; specifically: First, connect the center O of the inner wall of the cylinder. i and the outer circle center O of the cover plate r Calculate O i O r The four intersection points of the line with the outer circle of the cover plate and the inner circle of the cylinder are denoted as A1, B1, A2, and B2, respectively. The midpoint C1 of A1 and B1 and the midpoint C2 of A2 and B2 are taken as the endpoints of the major axis of the ellipse; the line passes through the center O of the two circles. i and O r Midpoint as O i O r The perpendicular line intersects the two circles at points A3, B3, A4, and B4 respectively; the midpoints C3 and C4 of A3 and B3 and the midpoints C4 of A4 and B4 are taken as the endpoints of the minor axis of the ellipse; the ellipse is calculated based on C1, C2, C3, and C4, which is the central ellipse of the figure between the inner wall circle of the cylinder and the outer circle of the cover plate, and is used as the welding trajectory. The welding trajectory start point determination unit is used to determine the widest point of the overlapping part between the cover plate and the cylindrical wall as the start and end points of the welding trajectory.

8. An electronic device, characterized in that, The device includes: Memory containing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the steps of the multi-beam laser weld seam recognition and welding path planning method for cylindrical cover plate welding and encapsulation as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions, which, when invoked, are used to perform the steps of the multi-beam laser weld seam identification and welding path planning method for cylindrical cover plate welding and encapsulation as described in any one of claims 1-6.

Images