Method and equipment for visual positioning and automatic compensation gluing of photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic module positioning and gluing, in particular to a photovoltaic module visual positioning and automatic compensation gluing method and equipment thereof.The method comprises the steps that after a photovoltaic module is restored, a visual camera is triggered to obtain image sources at the four corners of the photovoltaic module; when the image source is analyzed, analyzing the images of the vertexes at the four corners of the photovoltaic module by adopting a Sauvola binarization method, and then obtaining coordinate values of the vertexes at the four corners of the photovoltaic module and the mark points; obtaining a first compensation value by subtracting the coordinate values of the vertexes at the four corners of the photovoltaic module obtained by calculation from the coordinate values of a preset template; obtaining a second compensation value by subtracting the coordinate values of the mark points at the four corners of the photovoltaic module obtained through calculation from the coordinate values of the preset mark positions; the difference between the obtained first compensation value and the obtained second compensation value is obtained, the final compensation value is obtained, the final gluing track is formed, and the gluing precision is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic component positioning and gluing, and in particular to a method and equipment for photovoltaic component visual positioning and automatic compensation gluing. Background Art

[0002] Conventional photovoltaic modules are composed of a glass substrate, solar cells placed on the glass substrate, and a film covering the solar cells. During the preparation of the photovoltaic module, it is necessary to apply sealant to the edge where the film contacts the glass substrate to encapsulate the solar cells between the glass and the film to protect the solar cells. Since butyl rubber has the characteristics of low water vapor permeability, electrical insulation, and high adhesion, in actual use, butyl rubber is often used as a sealant to coat photovoltaic modules. When applying the glue, the glue is usually applied along the edges around the surface of the photovoltaic module. In order to improve the accuracy of the glue application, a correction positioning mechanism is required to position the glass substrate before applying the glue, so as to position the glass substrate to a preset position to avoid the phenomenon of glue application deviation.

[0003] In the prior art, a aligning wheel is usually used to align and position the photovoltaic module along its circumference. However, due to the deviation in the size of the incoming glass substrate of the automated production line and the deviation in the positioning, there is bound to be more or less coordinate deviation between the actual position of the glass substrate and the preset template during each glue application operation, which in turn causes the glue application robot arm to fail to accurately apply glue to seal the edge of the photovoltaic module when applying glue according to the preset glue application trajectory. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose a method and equipment for visual positioning and automatic compensation of gluing of photovoltaic modules, so as to solve the problem that there are more or less gluing deviations when gluing existing photovoltaic modules, resulting in failure to accurately seal the edges of photovoltaic modules.

[0005] Based on the above purpose, the present invention provides a method for visual positioning and automatic compensation of gluing of photovoltaic modules, comprising the following steps:

[0006] S1, after the photovoltaic module is aligned, the visual system is triggered to take pictures. Marking points are fixed at the four corners of the photovoltaic module. The visual system includes visual cameras located above the four corners of the photovoltaic module. The image sources at the four corners of the photovoltaic module are obtained through the visual cameras.

[0007] S2, analyzing the image source, obtaining the coordinate values ​​of the vertices at the four corners of the photovoltaic module, and the coordinate values ​​of the marking points;

[0008] S3, calculating and subtracting the coordinate values ​​of the vertices at the four corners of the photovoltaic module from the coordinate values ​​of the preset template to obtain a first compensation value;

[0009] S4, calculating and subtracting the coordinate values ​​of the marking points at the four corners of the photovoltaic module from the coordinate values ​​of the preset marking positions to obtain a second compensation value;

[0010] S5, subtracting the obtained first compensation value from the obtained second compensation value to obtain a final compensation value, and feeding the final compensation value back to the gluing robot arm to form a final gluing trajectory.

[0011] Preferably, when analyzing the image source in S2, the Sauvola binarization method is used to analyze the image of the vertices at the four corners of the photovoltaic component, and the image is filtered, and then line-to-line measurement is performed to obtain the coordinate values ​​of the vertices at the four corners of the photovoltaic component.

[0012] Preferably, when analyzing the image source in S2, a hard threshold binarization method is used to analyze the image of the marked points at the four corners of the photovoltaic module, and the image is filtered, and then line measurement is performed to obtain the coordinate values ​​of the marked points at the four corners of the photovoltaic module.

[0013] Preferably, the marking point includes a black light-shielding film substrate, and a white self-adhesive paper adhered to the black light-shielding film substrate, and the white self-adhesive paper is designed in the shape of a cross line segment.

[0014] Preferably, the photovoltaic components are fed, aligned and glued through a transfer platform. An avoidance hole is opened on the transfer platform at the glue coating area, and a fixed column is independently erected below the avoidance hole. The top of the fixed column is rotatably connected to a marking seat, and the marking point is set on the top surface of the marking seat. A connecting rope is connected between the marking seat and the avoidance hole. When the glue coating area itself is offset, the marking seat is pulled to rotate by the connecting rope.

[0015] Preferably, the marking seat is designed to be in a disc shape, with first fixing positions respectively provided on both sides of the outer circumference of the marking seat, and second fixing positions respectively provided on both sides of the inner circle of the avoidance hole, and two connecting ropes are symmetrically arranged, one end of the connecting rope is connected to one of the first fixing positions, and the other end is arranged along the outer circumference of the marking seat and connected to the second fixing position on the side away from the first fixing position.

[0016] The present invention also provides a device for visual positioning and automatic compensation of gluing of photovoltaic modules, including a transfer platform for driving the feeding, alignment and gluing of photovoltaic modules:

[0017] A visual system is provided above the glue coating area on the transfer platform. The visual system includes visual cameras located above the four corners of the photovoltaic modules in the glue coating area, and is used to obtain image sources at the four corners of the photovoltaic modules.

[0018] An avoidance hole is opened on the transfer platform at the gluing area, and a fixed column is independently erected below the avoidance hole. The top of the fixed column is rotatably connected to a marking seat, and a marking point for visual camera recognition is provided on the top surface of the marking seat. A connecting rope is connected between the marking seat and the avoidance hole. When the gluing area itself deviates, the marking seat is pulled to rotate by the connecting rope.

[0019] Preferably, the marking seat is designed to be in a disc shape, with first fixing positions respectively provided on both sides of the outer circumference of the marking seat, and second fixing positions respectively provided on both sides of the inner circle of the avoidance hole, and two connecting ropes are symmetrically arranged, one end of the connecting rope is connected to one of the first fixing positions, and the other end is arranged along the outer circumference of the marking seat and connected to the second fixing position on the side away from the first fixing position.

[0020] The beneficial effects of the present invention are as follows: after the photovoltaic assembly is corrected, the visual system is triggered to take pictures, and marking points are fixed at the four corners of the photovoltaic assembly. The visual system includes a visual camera located above the four corners of the photovoltaic assembly, and the image source at the four corners of the photovoltaic assembly is obtained through the visual camera; when analyzing the image source, the Sauvola binarization method is used to analyze the image of the vertices at the four corners of the photovoltaic assembly, and then the coordinate values ​​of the vertices at the four corners of the photovoltaic assembly and the coordinate values ​​of the marking points at the four corners of the photovoltaic assembly are obtained; the first compensation value is obtained by calculating the difference between the coordinate values ​​of the vertices at the four corners of the photovoltaic assembly obtained and the coordinate values ​​of the preset template; the second compensation value is obtained by calculating the difference between the coordinate values ​​of the marking points at the four corners of the photovoltaic assembly obtained and the coordinate values ​​of the preset marking position; the first compensation value obtained is subtracted from the second compensation value obtained to obtain the final compensation value, and the final compensation value is fed back to the glue coating robot arm to form the final glue coating trajectory. Therefore, in view of the errors existing in the incoming glass substrate itself, the errors existing in the repeated correction positioning, and the error influence caused by the displacement jitter of the visual camera, a positioning error detection method is designed and an error compensation model is constructed, which greatly improves the glue coating accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A flow chart of the method for visually positioning and automatically compensating for gluing of photovoltaic modules of the present invention;

[0023] Figure 2 It is a structural schematic diagram of the avoidance hole, the fixed column and the marking seat of the present invention;

[0024] Figure 3It is a structural schematic diagram of the connecting rope when the marking seat of the present invention is located below the avoidance hole;

[0025] Figure 4 It is a structural schematic diagram of the connecting rope when the marking seat of the present invention is located in the avoidance hole;

[0026] Figure 5 It is a schematic diagram of the top view structure of the marking seat and the avoidance hole of the present invention;

[0027] Figure 6 It is a schematic diagram of the structure of the glue coating area and the avoidance hole when they are offset.

[0028] The markings in the figure are:

[0029] 100, marking point; 101, black shading film base; 102, white self-adhesive tape; 200, avoidance hole; 201, second fixed position; 300, fixed column; 400, marking seat; 401, first fixed position; 500, connecting rope. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0031] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0032] A method for visually positioning and automatically compensating for gluing of photovoltaic modules, such as Figure 1 As shown, the following steps are included:

[0033] S1, after the photovoltaic module is aligned, the visual system is triggered to take pictures. Marking points 100 are fixed at the four corners of the photovoltaic module. The visual system includes visual cameras located above the four corners of the photovoltaic module. The image sources at the four corners of the photovoltaic module are obtained through the visual cameras.

[0034] S2, analyzing the image source, obtaining the coordinate values ​​of the vertices at the four corners of the photovoltaic module, and the coordinate value of the marking point 100;

[0035] S3, calculating and subtracting the coordinate values ​​of the vertices at the four corners of the photovoltaic module from the coordinate values ​​of the preset template to obtain a first compensation value;

[0036] S4, calculating and subtracting the coordinate values ​​of the marking points 100 at the four corners of the photovoltaic module from the coordinate values ​​of the preset marking positions to obtain a second compensation value;

[0037] S5, subtracting the obtained first compensation value from the obtained second compensation value to obtain a final compensation value, and feeding the final compensation value back to the gluing robot arm to form a final gluing trajectory.

[0038] Among them, in actual production situations, the glass substrate of photovoltaic modules is a quadrilateral shape close to a rectangle. In the absence of visual compensation, a version of standard process parameters is debugged based on the glass substrate that is more in line with the standard. According to the template glass, the displacement of the four corners of the glass is taught, that is, visual compensation (hereinafter referred to as compensation), so that the compensation of the template glass is approximately zero when the template glass is repeatedly photographed; before each glue application, take a photo to identify the compensation, and add the compensation to the starting and ending points of each edge.

[0039] The position of the visual camera in the hardware solution is not strictly fixed, but there is a displacement process, that is, when applying glue, the visual camera and the connecting frame connected to the visual camera are retracted to avoid the gluing robot arm. After gluing, when entering the positioning of the next batch, the visual camera is extended again. Therefore, it is necessary to eliminate the error caused by the displacement jitter of the visual camera. In this regard, in the present invention, after the photovoltaic component is corrected, the visual system is triggered to take pictures. Marking points 100 are fixed at the four corners of the photovoltaic component. The visual system includes a visual camera located above the four corners of the photovoltaic component. The image source at the four corners of the photovoltaic component is obtained through the visual camera; when analyzing the image source, the Sauvola binarization method is used to analyze the image of the vertices at the four corners of the photovoltaic component, and the image is filtered, and then line measurement is performed to confirm The coordinate information of the intersection is determined, and then the coordinate values ​​of the vertices at the four corners of the photovoltaic module are obtained. At the same time, the hard threshold binarization method is used to analyze the image of the mark point 100 at the four corners of the photovoltaic module, and the image is filtered, and then line measurement is performed to determine the coordinate information of the intersection, and then the coordinate values ​​of the mark point 100 at the four corners of the photovoltaic module are obtained; the first compensation value is obtained by calculating the difference between the coordinate value of the vertex at the four corners of the photovoltaic module and the coordinate value of the preset template; the second compensation value is obtained by calculating the difference between the coordinate value of the mark point 100 at the four corners of the photovoltaic module and the coordinate value of the preset mark position; the first compensation value obtained is subtracted from the second compensation value obtained to obtain the final compensation value, and the final compensation value is fed back to the glue coating robot arm to form the final glue coating trajectory. There are 8 groups of final compensation values. For example, the final compensation value at the 4 groups of vertex positions A, B, C, and D at the four corners of the photovoltaic module is ΔA x , ΔAy , ΔB x , ΔB y , ΔC x , ΔC y , ΔD x , ΔD y Therefore, in view of the errors existing in the incoming glass substrate itself, the errors existing in the repeated correction positioning, and the errors caused by the displacement jitter of the visual camera, a positioning error detection method is designed and an error compensation model is constructed, which greatly improves the glue coating accuracy.

[0040] Among them, the marking point 100 is designed to be a non-reflective high-contrast black and white material. More preferably, the marking point 100 includes a black shading film base 101, and a white self-adhesive paper 102 pasted on the black shading film base 101, and the white self-adhesive paper 102 is designed in the shape of a cross line segment.

[0041] As another embodiment of the present invention, Figure 2 As shown, the photovoltaic components are fed, aligned and glued through the transfer platform. An avoidance hole 200 is opened on the transfer platform at the glue coating area, and a fixed column 300 is independently erected below the avoidance hole 200. The top of the fixed column 300 is rotatably connected to a marking seat 400, and the marking point 100 is set on the top surface of the marking seat 400, so that the visual camera captures the image of the marking point 100 through the avoidance hole 200. Since the fixed column 300 is independently fixed on the supporting ground, the marking seat 400 and the marking point 100 are equivalent to being firmly fixed in a fixed position. Even if the transfer platform and the glue coating area have a slight offset during long-term use, the marking point 100 will not be offset accordingly. If the marking point 100 is selected to be directly set on the glue coating area, when it is synchronously offset with the glue coating area, the offset will be repeatedly calculated into the first compensation value and the second compensation value, resulting in repeated compensation, which will then lead to errors in gluing. On this basis, Figure 3 , Figure 4 , Figure 5 , Figure 6As shown, a connecting rope 500 is also connected between the marking seat 400 and the avoidance hole 200. When the gluing area itself is offset, the marking seat 400 is pulled to rotate by the connecting rope 500. The marking point 100, for example, is in the shape of a cross located at the center of the marking seat 400, and the visual camera obtains the cross intersection position coordinates of the marking point 100, so it will not deviate with the avoidance hole 200, but the cross-shaped marking point 100 rotates, which leads to changes in its shape, which will also be captured by the visual camera. When the visual camera captures that the shapes of the marking points 100 at the four corners have all undergone the same obvious changes, it means that the gluing area has undergone a fixed offset during long-term use, which can remind the operator to check and maintain the equipment itself in time to avoid more serious problems with the equipment hardware. If there is no problem with the maintenance equipment, the position of the fixed column 300 can be adjusted or the orientation of the rotating marking seat 400 can be reset to the initial cross shape to avoid repeated detection of shape changes and repeated warnings. At the same time, the coordinate value of the preset template can be corrected to avoid the displacement of the gluing area being repeatedly calculated into the first compensation value.

[0042] Specific options, such as Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, the marking seat 400 is designed to be in a disc shape, and first fixing positions 401 are respectively provided on both sides of the outer circumference of the marking seat 400. The avoidance hole 200 can be designed to be in a rectangular shape, and second fixing positions 201 are respectively provided on both sides of the inner circle of the avoidance hole 200. Two connecting ropes 500 are symmetrically arranged, one end of the connecting rope 500 is connected to one of the first fixing positions 401, and the other end is arranged along the outer circumference of the marking seat 400 and connected to the second fixing position 201 on the side away from the first fixing position 401, so that when the glue coating area itself deviates, as shown in FIG. Figure 6 As shown, the marking seat 400 is rotated by pulling the connecting rope 500 on the avoidance hole 200. Specifically, an elastic component such as a torsion spring may be provided at the rotating connection between the marking seat 400 and the top of the fixed column 300, which is used to drive the marking seat 400 to rotate and reset when the avoidance hole 200 moves and resets.

[0043] Among them, Figure 3 As shown, if the avoidance hole 200 has a large displacement deviation with the glue coating area, so that the avoidance hole 200 completely deviates from the marking seat 400, the marking point 100 is then covered, and then the visual camera fails to obtain the marking point 100, thereby alerting the operator to timely maintenance. Figure 4 , Figure 5 , Figure 6 As shown, the marking seat 400 penetrates into the avoidance hole 200. When the avoidance hole 200 has a large displacement deviation with the glue coating area, it abuts against the marking seat 400 to avoid further displacement.

[0044] Optional, such as Figure 3 As shown, when the marking seat 400 is located below the avoidance hole 200, connecting rods can be connected on both sides of the fixed column 300, and a through hole for guiding the connecting rope 500 to pass through is opened at the top of the connecting rod. At the same time, a wire groove for winding the connecting rope 500 can be opened around the outer circle of the marking seat 400.

[0045] The present invention also provides a device for visually positioning photovoltaic modules and automatically compensating for glue coating, such as Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, it includes a transfer platform for driving the feeding, alignment and gluing of photovoltaic modules;

[0046] A visual system is provided above the glue coating area on the transfer platform. The visual system includes visual cameras located above the four corners of the photovoltaic modules in the glue coating area, and is used to obtain image sources at the four corners of the photovoltaic modules.

[0047] An avoidance hole 200 is provided on the transfer platform at the gluing area, and a fixed column 300 is independently erected below the avoidance hole 200. The top end of the fixed column 300 is rotatably connected to a marking seat 400, and a marking point 100 for identification by a visual camera is provided on the top surface of the marking seat 400. A connecting rope 500 is connected between the marking seat 400 and the avoidance hole 200. When the gluing area itself is offset, the marking seat 400 is pulled to rotate by the connecting rope 500.

[0048] In an embodiment of the present invention, Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, the marking seat 400 is designed to be in a disc shape, and first fixing positions 401 are respectively provided on both sides of the outer circumference of the marking seat 400. The avoidance hole 200 can be designed to be in a rectangular shape, and second fixing positions 201 are respectively provided on both sides of the inner circle of the avoidance hole 200. Two connecting ropes 500 are symmetrically arranged, one end of the connecting rope 500 is connected to one of the first fixing positions 401, and the other end is arranged along the outer circumference of the marking seat 400 and connected to the second fixing position 201 on the side away from the first fixing position 401, so that when the glue coating area itself deviates, as shown in FIG. Figure 6 As shown, the marking seat 400 is rotated by pulling the connecting rope 500 on the avoidance hole 200.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for visual positioning and automatic compensation of gluing of photovoltaic modules, characterized in that: The steps include: S1, after the photovoltaic assembly is aligned, triggering the visual system to take pictures, the four corners of the photovoltaic assembly are fixed with marking points (100), the visual system includes a visual camera located above the four corners of the photovoltaic assembly, and the image source at the four corners of the photovoltaic assembly is obtained through the visual camera; S2, analyzing the image source, obtaining the coordinate values ​​of the vertices at the four corners of the photovoltaic module, and the coordinate value of the marking point (100); S3, calculating and subtracting the coordinate values ​​of the vertices at the four corners of the photovoltaic module from the coordinate values ​​of the preset template to obtain a first compensation value; S4, calculating and subtracting the coordinate values ​​of the marking points (100) at the four corners of the photovoltaic module obtained by calculation from the coordinate values ​​of the preset marking positions to obtain a second compensation value; S5, subtracting the obtained first compensation value from the obtained second compensation value to obtain a final compensation value, and feeding the final compensation value back to the gluing robot arm to form a final gluing trajectory.

2. A method for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 1, characterized in that: When analyzing the image source in S2, the Sauvola binarization method is used to analyze the image of the vertices at the four corners of the photovoltaic module, and the image is filtered, and then line-to-line measurement is performed to obtain the coordinate values ​​of the vertices at the four corners of the photovoltaic module.

3. A method for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 1, characterized in that: When analyzing the image source in S2, a hard threshold binarization method is used to analyze the image of the marked points (100) at the four corners of the photovoltaic module, and the image is filtered, and then line measurement is performed to obtain the coordinate values ​​of the marked points (100) at the four corners of the photovoltaic module.

4. The method for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 1, characterized in that: The marking point (100) comprises a black light-shielding film substrate (101), and a white self-adhesive paper (102) adhered to the black light-shielding film substrate (101), wherein the white self-adhesive paper (102) is designed in the shape of a cross line segment.

5. The method for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 1, characterized in that: The photovoltaic components are fed, aligned and glued via a transfer platform. An avoidance hole (200) is provided on the transfer platform at the glue-coating area. A fixed column (300) is independently erected below the avoidance hole (200). The top end of the fixed column (300) is rotatably connected to a marking seat (400). A marking point (100) is provided on the top end surface of the marking seat (400). A connecting rope (500) is connected between the marking seat (400) and the avoidance hole (200). When the glue-coating area itself deviates, the marking seat (400) is pulled to rotate by the connecting rope (500).

6. A method for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 5, characterized in that: The marking seat (400) is designed to be in the shape of a disc, and first fixing positions (401) are respectively provided on both sides of the outer circumference of the marking seat (400), and second fixing positions (201) are respectively provided on both sides of the inner circle of the avoidance hole (200), and two connecting ropes (500) are symmetrically arranged, one end of the connecting rope (500) is connected to one of the first fixing positions (401), and the other end is arranged along the outer circumference of the marking seat (400) and connected to the second fixing position (201) on the side away from the first fixing position (401).

7. A device for visual positioning and automatic compensating gluing of photovoltaic modules, which uses the method for visual positioning and automatic compensating gluing of photovoltaic modules as described in any one of claims 1 to 6 for gluing, and includes a transfer platform for driving the feeding, alignment and gluing of photovoltaic modules, characterized in that: A visual system is provided on the transfer platform above the glue coating area, and the visual system includes visual cameras located above the four corners of the photovoltaic modules in the glue coating area, and is used to obtain image sources at the four corners of the photovoltaic modules; An avoidance hole (200) is provided on the transfer platform at the gluing area, a fixed column (300) is independently provided below the avoidance hole (200), the top end of the fixed column (300) is rotatably connected to a marking seat (400), a marking point (100) for identification by a visual camera is provided on the top surface of the marking seat (400), a connecting rope (500) is connected between the marking seat (400) and the avoidance hole (200), and when the gluing area itself deviates, the marking seat (400) is pulled to rotate by the connecting rope (500).

8. The device for visual positioning and automatic compensation of gluing of photovoltaic modules according to claim 7, characterized in that: The marking seat (400) is designed to be in the shape of a disc, and first fixing positions (401) are respectively provided on both sides of the outer circumference of the marking seat (400), and second fixing positions (201) are respectively provided on both sides of the inner circle of the avoidance hole (200), and two connecting ropes (500) are symmetrically arranged, one end of the connecting rope (500) is connected to one of the first fixing positions (401), and the other end is arranged along the outer circumference of the marking seat (400) and connected to the second fixing position (201) on the side away from the first fixing position (401).

Images