Offset Detection Method and Offset Detection Device

Abstract

The present application provides a method and a device for offset detection, which relate to the field of battery manufacturing. The method includes: obtaining a first image and a second image through a first camera and a second camera, where the first image includes an image of a first pole piece during the winding process of an electrode assembly, and the second image includes an image of a second pole piece during the winding process of the electrode assembly; determining whether the first camera and the second camera are offset according to the distances from the reference points in the first image and the reference points in the second image to a specific position, and when it is determined that the first camera and the second camera are not offset, determining whether the electrode assembly is offset according to the vertical distance from the reference point in the first image to the boundary of the first pole piece and the vertical distance from the reference point in the second image to the boundary of the second pole piece. Thus, through the first image and the second image, it is possible to determine whether the first camera and the second camera are positionally offset, and on the premise that the cameras are not offset, further determine the positional offset of the electrode assembly.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing, and particularly to a method and device for detecting offset, which are used to detect the position offset of an electrode assembly during winding manufacturing. Background Art

[0002] As a component in a battery cell where electrochemical reactions occur, an electrode assembly is generally formed by winding or laminating a first pole piece, a second pole piece, and a separator. During the winding process of the electrode assembly, the first pole piece, the second pole piece, and the separator are prone to yaw, causing the first pole piece, the second pole piece, and the separator to deviate from their normal positions. And the quality of the winding of the electrode assembly directly affects the performance of the battery cell. Therefore, how to accurately detect the offset of the electrode assembly is crucial for battery manufacturing. Summary of the Invention

[0003] In view of the above problems, the present invention provides a method and device for detecting offset, which can accurately detect the position offset during the winding of the electrode assembly.

[0004] In a first aspect, a method for detecting offset is provided, which is used to detect the position offset during the winding of an electrode assembly. The electrode assembly includes a first pole piece, a second pole piece, and a separator. The method for detecting offset includes: respectively obtaining a first image and a second image through a first camera and a second camera. The first image includes an image of the first pole piece of the electrode assembly during the winding process, and the second image includes an image of the second pole piece of the electrode assembly during the winding process; a camera offset determination step of determining whether the first camera and the second camera are offset according to the distances from the reference points in the first image and the reference points in the second image to a specific position, where the specific position is the position of the same object that appears in the first image and the second image; an electrode assembly offset determination step of determining whether the electrode assembly is offset according to the vertical distance from the reference point in the first image to the boundary of the first pole piece and the vertical distance from the reference point in the second image to the boundary of the second pole piece when it is determined that the first camera and the second camera are not offset.

[0005] After the electrode assembly is wound, the first electrode sheet, the second electrode sheet, and the separator are stacked. And due to the limitation of the imaging unit, it is necessary to use the first image obtained by the first camera and the second image obtained by the second camera to detect the position offset during the winding of the electrode assembly. Therefore, the prerequisite for accurately determining the position offset of the electrode assembly is that the first camera and the second camera are in the correct positions. In the technical solution of the embodiment of the present application, the position offset of the cameras and the position offset of the electrode assembly can be determined only by the first image obtained by the first camera and the second image obtained by the second camera, without the need to separately obtain additional images for determining the position offset of the cameras. Thus, it is possible to ensure that the first camera and the second camera are in the correct positions with relatively low cost and high efficiency, and on this premise, accurately determine the position offset of the electrode assembly.

[0006] In some embodiments, the camera offset determination step includes: obtaining a first distance according to the first image, where the first distance is the distance from a first reference point to the specific position; obtaining a second distance according to the second image, where the second distance is the distance from a second reference point to the specific position; when the difference between the first distance and the second distance is greater than a first threshold, it is determined that a relative displacement occurs between the first camera and the second camera. In the technical solution of the embodiment of the present application, as long as the first camera and / or the second camera does not shift, the first reference point of the first image and the second reference point of the second image respectively correspond to the fixed points of the electrode assembly, and the specific position appears in both the first image and the second image and also corresponds to the fixed point of the electrode assembly. Therefore, the difference between the distance from the first reference point to the specific position and the distance from the second reference point to the specific position is constant. Thus, by comparing this difference with the first threshold, it is easy to determine whether a relative displacement occurs between the first camera and the second camera.

[0007] In some embodiments, the camera offset determination step includes: obtaining a first distance in the first image, where the first distance is the distance from a first reference point to the specific position, obtaining a second distance in the second image, where the second distance is the distance from a second reference point to the specific position, when the first distance exceeds the range of the first distance reference value, it is determined that the first camera shifts; when the second distance exceeds the range of the second distance reference value, it is determined that the second camera shifts. Thus, by comparing the first distance and the second distance with the preset values respectively, it is possible to determine whether the first camera and the second camera shift respectively. Compared with determining the relationship between the first distance and the second distance, it is possible to more accurately determine which camera shifts.

[0008] In some embodiments, the specific position is the boundary of the isolation film, or the specific position is the position where the laser irradiates the electrode assembly, where the laser is emitted by a laser and irradiates the electrode assembly to generate a pixel boundary between the first image and the second image. In the technical solution of the embodiments of the present application, the isolation film appears in both the first image and the second image, and the edge of the isolation film exceeds the edges of the first and second pole pieces, making it easy to identify. Therefore, by setting the boundary of the isolation film as the specific position, the position offset between the first camera and the second camera can be easily determined without the need to additionally introduce other devices. In addition, a specific position can also be generated in the first image and the second image by the laser, and the position offset between the first camera and the second camera can be determined.

[0009] In some embodiments, the electrode assembly offset determination step includes: obtaining a third distance in the first image, where the third distance is the vertical distance from a third reference point to the boundary of the first pole piece, obtaining a fourth distance in the second image, where the fourth distance is the vertical distance from a fourth reference point to the boundary of the second pole piece. When the difference between the first distance and the second distance is less than or equal to the first threshold, and the absolute value of the difference between the third distance and the fourth distance minus the preset distance between the boundary of the first pole piece and the boundary of the second pole piece is greater than the second threshold, it is determined that the electrode assembly is offset. Thus, on the premise of ensuring that the first camera and the second camera are in the correct positions, the position offset of the electrode assembly during winding can still be accurately determined through the first image and the second image.

[0010] In some embodiments, the electrode assembly offset determination step includes: obtaining a third distance in the first image, where the third distance is the vertical distance from a third reference point to the boundary of the first pole piece, obtaining a fourth distance in the second image, where the fourth distance is the vertical distance from a fourth reference point to the boundary of the second pole piece. When the difference between the first distance and the second distance is less than or equal to the first threshold, and the third distance exceeds the range of the third distance reference value, it is determined that the first pole piece is offset. When the difference between the first distance and the second distance is less than or equal to the first threshold, and the fourth distance exceeds the range of the fourth distance reference value, it is determined that the second pole piece is offset. Thus, by comparing the third distance and the fourth distance with the preset values respectively, it can be determined whether the first pole piece and the second pole piece are offset in position respectively. Compared with determining the relationship between the third distance and the fourth distance, it can more accurately determine which pole piece is offset in position.

[0011] In some embodiments, the electrode assembly offset determination step includes: obtaining a third distance in the first image, where the third distance is the perpendicular distance from a third reference point to the boundary of the first pole piece, obtaining a fourth distance in the second image, where the fourth distance is the perpendicular distance from a fourth reference point to the boundary of the second pole piece, and when the difference between the third distance and the fourth distance, after subtracting the preset distance between the boundary of the first pole piece and the boundary of the second pole piece, and then subtracting the difference between the first distance and the second distance, the obtained difference (absolute value) is greater than a third threshold, it is determined that the electrode assembly is offset. In the technical solution of the embodiments of the present application, the difference between the first distance and the second distance is the coordinate system deviation between the first image and the second image introduced by the first camera and the second camera. By further subtracting the difference between the first distance and the second distance from the difference between the third distance and the fourth distance, the position deviation of the first camera and the second camera can be excluded when determining the position during the winding of the electrode assembly, and the distance between the actual boundaries of the first pole piece and the second pole piece can be obtained, thereby more accurately determining the position offset of the electrode assembly.

[0012] In some embodiments, the second camera uses an infrared light source to penetrate one layer of the separator film to photograph the second pole piece behind it. Thereby, it is possible to ensure the identification of the second pole piece in the second image, and further obtain the fourth distance for comparison with the third distance to determine whether the electrode assembly is offset during winding.

[0013] In some embodiments, the separator film includes a first separator film and a second separator film, the first image includes the first pole piece and the first separator film, the second image includes the second pole piece and the second separator film, and the specific position is the boundary where the second separator film is exposed from the first separator film or the boundary where the first separator film is exposed from the second separator film. Thus, even if the first separator film and / or the second separator film is offset, it is possible to ensure the correspondence between the specific position in the first image and the specific position in the second image.

[0014] Second aspect, there is provided a deviation detection device for detecting the position deviation during the winding of an electrode assembly. The electrode assembly includes a first pole piece, a second pole piece, and a separator. The deviation detection device includes: a first camera and a second camera that respectively acquire a first image and a second image. The first image includes an image of the first pole piece of the electrode assembly during the winding process, and the second image includes an image of the second pole piece of the electrode assembly during the winding process; and a deviation determination unit that determines whether the first camera and the second camera are deviated according to the distances from the reference points in the first image and the reference points in the second image to a specific position. When it is determined that the first camera and the second camera are not deviated, it is determined whether the electrode assembly is deviated according to the vertical distance from the reference point in the first image to the boundary of the first pole piece and the vertical distance from the reference point in the second image to the boundary of the second pole piece. Description of the Drawings

[0015] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0016] Figure 1 is a schematic diagram of an electrode assembly manufacturing device including an embodiment of the present application.

[0017] Figure 2 is a schematic diagram of a wound electrode assembly according to an embodiment of the present application.

[0018] Figure 3 is a cross-sectional view of the X-Y cross-section of a wound electrode assembly according to an embodiment of the present application.

[0019] Figure 4 is a schematic diagram of an unfolded electrode assembly according to an embodiment of the present application.

[0020] Figure 5 is a flowchart of a deviation detection method according to an embodiment of the present application.

[0021] Figure 6 is a schematic diagram of a first image and a second image according to an embodiment of the present application.

[0022] Figure 7 is a diagram showing the deviation amount of the actual electrode assembly when the first camera and the second camera have a position deviation within an acceptable range according to an embodiment of the present application.

[0023] Figure 8 is a diagram showing a specific position when a first separator is exposed from a second separator according to an embodiment of the present application.

[0024] Description of the Reference Numerals:

[0025] 100 Electrode assembly, 1 First electrode tab, 11 First tab, 2 Second electrode tab, 22 Second tab, 3 Separator, 31 First separator, 32 Second separator, 4 Imaging unit, 41 First camera, 42 Second camera, 5 Winding needle, 6 Specific position, T1 First image, T2 Second image, A1 First reference point, A2 Second reference point, d1 First distance, d2 Second distance, d3 Third distance, d4 Fourth distance, 200 Offset detection method. Detailed implementation

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0027] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs; the terms used in the description of the present application in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the description and claims of the present application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of the present application or the above drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship.

[0028] Referring to "embodiments" in the present application means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments.

[0029] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "attached" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0030] In this application, the term "and / or" is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, in this application, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0031] In this application, "a plurality of" means two or more (including two). Similarly, "a plurality of groups" means two or more groups (including two groups), and "a plurality of sheets" means two or more sheets (including two sheets).

[0032] Figure 1 It is a schematic diagram of an electrode assembly manufacturing device including an embodiment of this application. Figure 2 It shows the electrode assembly 100 formed by winding. As Figure 1 shown, the electrode assembly manufacturing device includes a conveying device and a winding device, and the winding device is the winding pin 5. Through the conveying device, the strip-shaped first electrode tab 1, second electrode tab 2, and separator film 3 (including the first separator film 31 and the second separator film 32) are conveyed to the winding pin 5, and the first electrode tab 1, the first separator film 31, the second electrode tab 2, and the second separator film 32 are sequentially stacked and wound around the winding pin 5 to form the electrode assembly 100 (refer to Figure 2 ). Figure 1 The winding pin 5 in Figure 2 is only for illustration. According to the type of battery cell and the shape of the battery housing, the electrode assembly can be wound into an electrode assembly with a cylindrical cross-section or an elliptical electrode assembly (as shown in Figure 3 ).

[0033] Each time the winding pin 5 rotates one week (360°), one layer is added to the electrode assembly 100. As shown in Figure 2 , as the winding pin 5 rotates, the thickness of the electrode assembly 100 in the X direction gradually increases. In addition, the width of the strip-shaped first electrode tab 1, second electrode tab 2, and separator film 3 determines the height of the electrode assembly 100 in the Z-axis direction. Figure 3 It is Figure 2 a cross-sectional view of the electrode assembly 100 shown in the X-Y plane. As shown in Figure 3 , for each winding layer, from the outside to the inside along the X direction, they are the second separator film 32, the second electrode tab 2, the first separator film 31, and the first electrode tab 1 in sequence. Thus, for each winding layer, the first separator film 31 and the second separator film 32 separate the second electrode tab 2 and the first electrode tab 1.

[0034] A relatively important parameter during the process of winding the electrode assembly is the alignment degree of the wound electrode assembly 100 in the Z-axis direction. Specifically, the alignment degree of the wound electrode assembly 100 in the Z-axis direction is the relative position of the second electrode tab 2 and the first electrode tab 1 in the Z-axis direction. Figure 4It is an unfolded view of the electrode assembly 100 after stacked winding along the Y direction. As Figure 4 shown, in the Z-axis direction (i.e., the width direction of the unfolded electrode assembly 100), from the outside to the inside, it should be in turn: the separator 3 (including the first separator 31 and the second separator 32), the second electrode sheet 2, and the first electrode sheet 1. That is, in the Z-axis direction, the boundaries of the first separator 31 and the second separator 32 are flush and located on the outermost side, while the first electrode sheet 1 is located on the innermost side, and the second electrode sheet 2 extends beyond the first electrode sheet 1 by a specified distance (predetermined distance). Since during the winding process of the wound electrode assembly 100, the second electrode sheet 2 and the first electrode sheet 1 are prone to yaw phenomena, the relative positions of the second electrode sheet 2 and the first electrode sheet 1 are shifted, thus affecting the quality and performance of the manufactured battery cells. Therefore, in order to monitor the relative position shift of the second electrode sheet 2 and the first electrode sheet 1, the electrode assembly manufacturing device further includes a photographing unit 4.

[0035] Ideally, the photographing unit photographs the wound electrode assembly 100 and identifies the second electrode sheet 2 and the first electrode sheet 1 in the obtained image to determine the relative position relationship between the second electrode sheet 2 and the first electrode sheet 1. However, as described above, for each winding layer of the electrode assembly, in order to photograph the first electrode sheet 1, it is necessary to penetrate through the second separator 32, the second electrode sheet 2, and the first separator 31. Due to the limitations of the existing photographing unit, for example, the penetration ability of the infrared photographing unit is very limited, it is difficult to accurately identify the second electrode sheet 2 and the first electrode sheet 1 and determine their relative position relationship in the photographed images of the wound first electrode sheet 1 or second electrode sheet 2. Therefore, it is necessary to use the images respectively photographing the first electrode sheet 1 and the second electrode sheet 2, corresponding to the first image T1 and the second image T2 respectively, to determine the position shift of the electrode sheets.

[0036] Therefore, usually, the photographing units of the first camera 41 and the second camera 42 are used to photograph the first image T1 and the second image T2 respectively. The first image T1 includes the first electrode sheet 1 during the winding process of the electrode assembly 100, and the second image T2 includes the second electrode sheet 2 during the winding process of the electrode assembly 100. However, the subsequent problem is that it is necessary to first ensure that the relative relationship between the coordinate systems in the first image T1 and the coordinate system in the second image T2 is fixed, that is, the first camera 41 and the second camera 42 are in preset positions and have not shifted.

[0037] Based on the above considerations, through in-depth research, the inventor proposed an offset detection method 200 for detecting the position offset during the winding of the electrode assembly 100. Figure 5 It is a flowchart of the offset detection method 200 according to an embodiment of the present application. Figure 6 It is a schematic diagram of the first image and the second image according to an embodiment of the present application. As Figure 5 、 Figure 6As shown, the offset detection method 200 includes: acquiring a first image T1 and a second image T2 through a first camera 41 and a second camera 42 respectively. The first image T1 includes an image of the first pole piece 1 during the winding process of the electrode assembly 100, and the second image T2 includes an image of the second pole piece 2 during the winding process of the electrode assembly 100; a camera offset determination step of determining whether the first camera 41 and the second camera 42 are offset according to the distances from the reference points in the first image T1 and the reference points in the second image T2 to a specific position 6, where the specific position 6 is the position of the same object appearing in the first image T1 and the second image T2; an electrode assembly offset determination step of determining whether the electrode assembly 100 is offset according to the vertical distance from the reference point in the first image T1 to the boundary of the first pole piece 1 and the vertical distance from the reference point in the second image T2 to the boundary of the second pole piece 2 when it is determined that the first camera 41 and the second camera 42 are not offset.

[0038] As described above, to determine whether the electrode assembly 100 is offset, it is necessary to use the first image T1 including the first pole piece 1 captured by the first camera 41 and the second image T2 including the second pole piece 2 captured by the second camera 42. In an embodiment of the present application, the specific position 6 appears in both the first image T1 and the second image T2 and corresponds to the fixed point of the electrode assembly 100. In addition, reference points with a corresponding relationship are pre-set in the first image T1 and the second image T2. As long as the first camera 41 and the second camera 42 are not offset, the reference points in the first image T1 and the second image T2 respectively correspond to the fixed point of the electrode assembly 100, that is, the difference between the distance from the reference point in the first image T1 to the specific position 6 and the distance from the reference point in the second image T2 to the specific position 6 is fixed. Therefore, according to the distances from the reference points in the first image T1 to the specific position 6 and from the reference points in the second image T2 to the specific position 6, it can be determined whether the first camera 41 and the second camera 42 are offset. Then, on the basis of determining that the first camera 41 and the second camera 42 are not offset, the first image T1 and the second image T2 are still used to determine whether the electrode assembly 100 is offset. That is, there is no need to separately acquire additional images for determining the offset of the camera position. Thus, it is possible to ensure that the first camera 41 and the second camera 42 are in the correct positions at a relatively low cost and efficiently, and on this premise, accurately determine the position offset of the electrode assembly.

[0039] According to some embodiments of the present application, the specific position 6 is the boundary of the separator 3, or the specific position 6 is the position where the laser irradiates the electrode assembly, where the laser is emitted by a laser and irradiates the electrode assembly to generate pixel boundaries in the first image T1 and the second image T2. Figure 6It is shown that the specific position 6 is the boundary of the separator 3 on the side away from the tabs 11 and 22, but the present application is not limited thereto. The specific position 6 can also be the boundary of the separator 3 on the side of the tabs 11 and 22. When the specific position 6 is the position where the laser irradiates the electrode assembly, it is preferable to use one laser, and the irradiation point of the laser can be acquired by both the first camera 41 and the second camera 42. The present application can also adopt two lasers, but problems such as the position alignment of the two lasers need to be considered.

[0040] As Figure 6 shown, in the first image T1 of the electrode assembly 100 before winding, the first electrode tab 1 is located on the outermost side in the X-axis direction, and below the first electrode tab 1 are the first separator 31, the second electrode tab 2, and the second separator 32 in sequence. Depending on the penetration ability of the imaging unit 4, in the first image T1, the first electrode tab 1 and the first separator 31 can be identified. In the second image T2 of the electrode assembly 100 after winding, the second separator 32 is located on the outermost side in the X-axis direction, and below the second separator 32 are the second electrode tab 2, the first separator 31, and the first electrode tab 1 in sequence. Depending on the penetration ability of the imaging unit 4, in the second image T2, at least the second separator 32 and the second electrode tab 2 can be identified. In addition, in the first image T1, the edge of the first separator 31 extends beyond the first electrode tab 1, and in the second image T2, the edge of the second separator 32 extends beyond the edge of the second electrode tab 2. Therefore, it is easy to identify the boundaries of the first separator 31 and the second separator 32 in the first image T1 and the second image T2. In addition, as Figure 4 shown, the boundaries of the first separator 31 and the second separator 32 are flush in the Z-axis direction, that is, the boundary of the first separator 31 on the first image T1 corresponds to the boundary of the second separator 32 on the second image T2. Therefore, the boundary of the separator 3 appears in both the first image T1 and the second image T2 and corresponds to the same position of the electrode assembly 100. Thus, by setting the boundary of the separator 3 as the specific position, it is possible to easily determine the position offset between the first camera 41 and the second camera 42 without introducing additional devices.

[0041] The specific position 6 can also be generated in the first image T1 and the second image T2 by a laser. Thereby, the influence caused by manufacturing errors of the first separator 31 and / or the second separator 32 or the offset of the first separator 31 and / or the second separator 32 can be excluded. When the specific position 6 is the position where the laser irradiates the electrode assembly, it is preferable to use one laser, and the irradiation point of the laser can be acquired by both the first camera 41 and the second camera 42.

[0042] According to some embodiments of the present application, the camera offset determination step of the offset detection method 200 includes: obtaining a first distance d1 according to the first image T1, where the first distance d1 is the distance from the first reference point A1 to the specific position 6 along the Z-axis direction; obtaining a second distance d2 according to the second image T2, where the second distance d2 is the distance from the second reference point A2 to the specific position 6 along the Z-axis direction; when the difference between the first distance d1 and the second distance d2 is greater than the first threshold, it is determined that a relative displacement occurs between the first camera 41 and the second camera 42.

[0043] The first distance d1 is the number of pixel points from the first reference point A1 to the specific position 6 along the Z-axis direction multiplied by the pixel equivalent, and the second distance d2 is the number of pixel points from the second reference point A2 along the Z-axis direction to the specific position 6 multiplied by the pixel equivalent. Here, the pixel equivalent is the actual distance represented by one pixel point. For example, in the first image T1, it can be obtained by dividing the actual width of the first pole piece 1 along the Z-axis by the total number of pixel values of the first pole piece 1 in the first image T1.

[0044] If the first camera 41 does not shift, once the first reference point A1 is determined, the first reference point A1 always corresponds to a fixed point on the first pole piece 1. That is, in the first image, the first distance d1 from the first reference point A1 to the specific position 6 along the Z-axis direction is fixed. Similarly, if the second camera 42 does not shift, the second distance d2 from the second reference point A2 to the specific position 6 along the Z-axis direction is also fixed. Therefore, the difference between the first distance d1 and the second distance d2 is also fixed. Generally, the probability that the first camera 41 and the second camera 42 shift simultaneously is very small. Therefore, it is not necessary to separately determine the position offsets of the first camera 41 and the second camera 42, thereby improving the determination efficiency.

[0045] Such as Figure 6As shown in the figure, the first reference point A1 can be determined as follows: when the first camera 41 and the second camera 42 are line-scan cameras, adjust the field of view of the first camera 41 so that the midpoint of the first pole piece 1 in the Z-axis direction appears at the middle position of the first image T1, that is, the midpoint of the first pole piece 1 in the Z-axis direction coincides with the pixel median point in the Z-axis direction of the first image T1 (for example, if the first image T1 has 4096 pixels in the Z-axis direction, the pixel median point is the 2048th pixel point), and set the first reference point A1 as the pixel median point in the Z-axis direction of the first image T1. The second reference point A2 can be determined in the same way: adjust the field of view of the second camera 42 so that the midpoint of the second pole piece 2 in the Z-axis direction coincides with the pixel median point in the Z-axis direction of the second image T2, and set the second reference point A2 as the pixel median point in the Z-axis direction of the second image T2. Thus, the first reference point A1 is the pixel point (the 2048th pixel point) corresponding to the midpoint of the first pole piece 1 in the Z-axis direction, and the second reference point A2 is the pixel point (the 2048th pixel point) corresponding to the midpoint of the second pole piece 2 in the Z-axis direction. The specific position 6 of the first image T1 and the second image T2 both corresponds to the boundary of the separator 3, and in an ideal situation, the midpoint of the first pole piece 1 coincides with the midpoint of the second pole piece 2. Then, in an ideal situation, if the first camera 41 and the second camera 42 do not shift, the first distance d1 from the first reference point A1 to the specific position 6 is equal to the second distance d2 from the second reference point A2 to the specific position 6. Thus, by comparing the difference between the first distance d1 and the second distance d2 with the first threshold (for example, 0.15 mm), it is possible to easily determine whether there is a relative displacement between the first camera and the second camera. It should be noted that the first reference point A1 and the second reference point A2 are not limited to the pixel median point, and the first reference point A1 and the second reference point A2 can be arbitrarily selected as long as the relationship between the first distance d1 and the second distance d2 obtained thereby is determined. In addition, when the first camera 41 and the second camera 42 are line-scan cameras, the obtained first image T1 and second image T2 are one-dimensional lines. However, the first camera 41 and the second camera 42 may also not be line-scan cameras. In this case, the first image T1 and the second image T2 are two-dimensional images, that is, they have a certain length in the Y direction. In the case where the first image T1 and the second image T2 are two-dimensional, the same operations as those for the line-scan cameras can be performed on the positions in the same Y direction of the first image T1 and the second image T2, or the first distance d1 and the second distance d2 can be set as the average distances in the entire Y direction.

[0046] According to some embodiments of the present application, the camera offset determination step of the offset detection method 200 includes: obtaining a first distance d1 in the first image T1, where the first distance d1 is the distance from the first reference point A1 to the specific position 6 along the Z-axis direction; obtaining a second distance d2 in the second image T2, where the second distance d2 is the distance from the second reference point A2 to the specific position 6 along the Z-axis direction. When the first distance d1 exceeds the first distance reference value range d1_ref, it is determined that the first camera 41 has an offset; when the second distance d2 exceeds the second distance reference value range d2_ref, it is determined that the second camera 42 has an offset.

[0047] Thus, by comparing the first distance d1 and the second distance d2 with the preset values d1_ref and d2_ref respectively, it can be determined whether the first camera 41 and the second camera 42 have position offsets. Compared with determining the relationship between the first distance d1 and the second distance d2, it can more accurately determine which camera has a position offset.

[0048] Alternatively, first determine the relationship between the first distance d1 and the second distance d2 to determine whether the first camera 41 and the second camera 42 have position offsets. When it is determined that the first camera 41 and the second camera 42 have position offsets, then compare the first distance d1 with the first distance reference value range d1_ref and the second distance d2 with the second distance reference value range d2_ref, so as to more accurately know which camera has a position offset. When it is determined that the first camera 41 and the second camera 42 do not have position offsets, there is no need to compare the first distance d1 with the first distance reference value range d1_ref and the second distance d2 with the second distance reference value range d2_ref. Thus, the offset determination efficiency can be improved.

[0049] According to some embodiments of the present application, the electrode assembly offset determination step of the offset detection method 200 includes: obtaining a third distance d3 in the first image T1, where the third distance d3 is the vertical distance from the third reference point A3 to the boundary of the first electrode tab 1; obtaining a fourth distance d4 in the second image T2, where the fourth distance d4 is the vertical distance from the fourth reference point A4 to the boundary of the second electrode tab 2. When the difference between the first distance d1 and the second distance d2 is less than or equal to the first threshold, and the difference between the third distance d3 and the fourth distance d4 minus the preset distance between the boundary of the first electrode tab 1 and the boundary of the second electrode tab 2 is greater than the second threshold, it is determined that the electrode assembly 100 has an offset.

[0050] As described above, during the winding of the electrode assembly, an important parameter is the alignment of the wound electrode assembly 100 in the Z-axis direction, especially the vertical distance between the boundary of the first electrode sheet 1 and the boundary of the second electrode sheet 2. On the premise that the first camera 41 and the second camera 42 are in the correct positions (the difference between the first distance d1 and the second distance d2 is less than or equal to the first threshold), the first image T1 and the second image T2 are still used. The vertical distance between the boundary of the first electrode sheet 1 and the boundary of the second electrode sheet 2 can be obtained through the difference between the third distance d3 and the fourth distance d4. Then, by comparing the obtained vertical distance between the boundary of the first electrode sheet 1 and the boundary of the second electrode sheet 2 with its preset distance, it can be accurately determined whether the position of the electrode assembly 100 is offset during winding.

[0051] It should be noted that, as Figure 6 shown, in the first image T1, the third reference point A3 can coincide with the first reference point A1. In the second image T2, the fourth reference point A4 can coincide with the second reference point A2. However, the third reference point A3 and the fourth reference point A4 are not limited to this, as long as the relationship between the obtained third distance d3 and the fourth distance d4 is determined.

[0052] According to some embodiments of the present application, the electrode assembly offset determination step of the offset detection method 200 includes: obtaining the third distance d3 in the first image T1, where the third distance d3 is the vertical distance from the third reference point A3 to the boundary of the first electrode sheet 1, and obtaining the fourth distance d4 in the second image T2, where the fourth distance d4 is the vertical distance from the fourth reference point A4 to the boundary of the second electrode sheet 2. When the difference between the first distance d1 and the second distance d2 is less than or equal to the first threshold, and the third distance d3 exceeds the third distance reference value range d3_ref, it is determined that the first electrode sheet 1 is offset. When the difference between the first distance d1 and the second distance d2 is less than or equal to the first threshold, and the fourth distance d4 exceeds the fourth distance reference value range d4_ref, it is determined that the second electrode sheet 2 is offset. Thus, by comparing the third distance d3 and the fourth distance d4 with the preset values d3_ref and d4_ref respectively, it can be determined whether the first electrode sheet 1 and the second electrode sheet 2 are offset in position respectively. Compared with determining the relationship between the third distance d3 and the fourth distance d4, it can more accurately determine which electrode sheet is offset in position.

[0053] Alternatively, the relationship between the third distance d3 and the fourth distance d4 can be determined first to determine whether the electrode assembly 100 is displaced during winding. When it is determined that the electrode assembly 100 is displaced during winding, the third distance d3 and the third distance reference value range d3_ref, and the fourth distance d4 and the fourth distance reference value range d4_ref are further compared, so as to more accurately know which pole piece is displaced. When it is determined that the electrode assembly 100 is not displaced during winding, there is no need to compare the third distance d3, the fourth distance d4 with the preset values d3_ref, d4_ref. Thus, the efficiency of displacement determination can be improved.

[0054] According to some embodiments of the present application, the electrode assembly displacement determination step of the displacement detection method 200 includes: obtaining a third distance d3 in the first image T1, where the third distance d3 is the vertical distance from the third reference point A3 to the boundary of the first pole piece 1, and obtaining a fourth distance d4 in the second image T2, where the fourth distance d4 is the vertical distance from the fourth reference point A4 to the boundary of the second pole piece 2. When the difference between the third distance d3 and the fourth distance d4 minus the preset distance between the boundaries of the first pole piece and the second pole piece, and then minus the difference between the first distance d1 and the second distance d2 is greater than the third threshold, it is determined that the electrode assembly is displaced.

[0055] As Figure 7 shown, when the positions of the first camera 41 and / or the second camera 42 are slightly displaced, but d1 - d2 is less than the first threshold, at this time, the displacement amount between the boundaries of the first pole piece 1 and the second pole piece 2 obtained from the difference between the third distance d3 and the fourth distance d4 includes two parts, that is, the coordinate system deviation d1 - d2 in the first image T1 and the second image T2 caused by the first camera 41 and the second camera 42, and the actual displacement amount between the boundaries of the first pole piece 1 and the second pole piece 2. Therefore, the actual displacement amount between the boundaries of the first pole piece 1 and the second pole piece 2 is equal to the difference between the third distance d3 and the fourth distance d4 minus the difference between the first distance d1 and the second distance d2. Thus, the influence caused by the position deviation of the first camera 41 and the second camera 42 can be excluded, and the position displacement of the electrode assembly 100 can be more accurately determined.

[0056] In Figure 7In this case, a situation is shown where the first reference point A1 and the third reference point A3 coincide, and the second reference point A2 and the fourth reference point A4 coincide. It should be understood that the present application is not limited thereto, and the first reference point to the fourth reference point A1 - A4 can be arbitrarily selected, as long as it satisfies: the third distance d3 and the fourth distance d4 obtained from the third reference point A3 and the fourth reference point A4 have a definite corresponding relationship, the first distance d1 and the second distance d2 obtained from the first reference point A1 and the second reference point A2 have a definite corresponding relationship, and d1 - d2 is the coordinate system deviation in the first image T1 and the second image T2 caused by the first camera 41 and the second camera 42.

[0057] According to some embodiments of the present application, the second camera 42 uses an infrared light source to penetrate a layer of isolation film to photograph the second pole piece 2 behind it. As described above (refer to Figure 6 ), in the second image T2, the second pole piece 2 is located below the second isolation film 32. Thus, by using an infrared camera that can penetrate the second isolation film 32, it is possible to ensure the identification of the second pole piece 2 in the second image T2, and further obtain the fourth distance d4 for comparison with the third distance d3 to determine whether the electrode assembly 100 has a position offset during winding.

[0058] According to some embodiments of the present application, the isolation film 3 includes a first isolation film 31 and a second isolation film 32, the first image T1 includes the first pole piece 1 and the first isolation film 31, the second image T2 includes the second pole piece 2 and the second isolation film 32, and the specific position 6 is the boundary where the second isolation film 32 is exposed from the first isolation film 31 or the boundary where the first isolation film 31 is exposed from the second isolation film 32.

[0059] Figure 8 An example showing the first isolation film 31 exposed from the second isolation film 32 is shown. As can be seen from Figure 8 in the first image T1, the first isolation film 31 is above the second isolation film 32, so the boundary of the first isolation film 31 can be identified and used as the specific position 6. In the second image T2, although the first isolation film 31 is below the second isolation film 32, since the first isolation film 31 is exposed from the second isolation film 32, the boundary of the first isolation film 31 can also be identified in the second image T2 and used as the specific position 6. Thus, the specific position 6 in the first image T1 corresponds to the specific position 6 in the second image T2, and both are the boundaries of the first isolation film 31. The same is true when the boundary of the second isolation film 32 is exposed from the boundary of the first isolation film 31. Thus, even if the first isolation film 31 and / or the second isolation film 32 have a position offset, it is possible to ensure that the specific position 6 in the first image T1 corresponds to the specific position 6 in the second image T2, and corresponds to the same position of the electrode assembly 100.

[0060] According to some embodiments of the present application, the time to obtain the second image T2 is later than the time to obtain the first image T1, and this time difference is set according to the shooting positions of the first camera 41 and the second camera 42 and the winding speed of the electrode assembly 100. Thus, by adjusting this time difference, it is possible to make the first image T1 and the second image T2 taken show the first pole piece 1 and the second pole piece 2 at the same position after winding, so that it is possible to detect the position offset of the first pole piece 1 and the second pole piece 2 at the same position, and the detection result can be made more accurate.

[0061] According to some embodiments of the present application, there is provided an offset detection device for detecting the position offset during the winding of an electrode assembly. The electrode assembly 100 includes a first pole piece 1, a second pole piece 2, and a separator 3. The offset detection device includes: a first camera 41 and a second camera 42 that respectively obtain a first image T1 and a second image T2. The first image T1 includes an image of the first pole piece 1 of the electrode assembly 100 during the winding process, and the second image T2 includes an image of the second pole piece 2 of the electrode assembly 100 during the winding process; and an offset determination unit that determines whether the first camera 41 and the second camera 42 are offset according to the distances from the reference points in the first image T1 and the reference points in the second image T2 to a specific position 6. When it is determined that the first camera 41 and the second camera 42 are not offset, it determines whether the electrode assembly 100 is offset according to the vertical distance from the reference point in the first image T1 to the boundary of the first pole piece 1 and the vertical distance from the reference point in the second image T2 to the boundary of the second pole piece 2.

[0062] According to some embodiments of the present application, refer to Figures 1 to 6 , the present application provides an offset detection method 200, including the following steps:

[0063] Obtain a first image T1 and a second image T2 through the first camera 41 and the second camera 42. The first image T1 includes an image of the first pole piece 1 of the electrode assembly 100 during the winding process, and the second image T2 includes an image of the second pole piece 2 of the electrode assembly 100 during the winding process;

[0064] Set the first reference point A1 in the first image T1 as the pixel median point in the Z-axis direction of the first image T1 (for example, for a line scan camera with 4096 pixels in the Z-axis direction, the pixel median point is the 2096th pixel point), set the second reference point A2 in the second image T2 as the pixel median point in the Z-axis direction of the second image T2, and set the specific position 6 as the boundary of the separator 3. Thus, obtain the first distance d1 from the first reference point A1 in the first image T1 to the boundary of the separator 3 and the second distance d2 from the second reference point A2 in the second image T2 to the specific position 6. By comparing the first distance d1 and the second distance d2 with the first threshold, determine whether the first camera 41 and / or the second camera 42 is / are offset. When the first camera 41 and / or the second camera 42 is / are offset, further compare d1 with the first distance reference value range d1_ref and d2 with the second distance reference value range d1_ref, so as to more accurately determine which camera of the first camera 41 and the second camera 42 is offset.

[0065] When it is determined that the first camera 41 and the second camera 42 are not offset, determine whether the electrode assembly 100 is offset. In the first image T1, set the third reference point A3 to coincide with the first reference point A1, and in the second image T2, set the fourth reference point A4 to coincide with the second reference point A2. Thus, obtain the third distance d3 from the third reference point A3 (the first reference point A1) in the first image T1 to the boundary of the first electrode tab 1 and the fourth distance d4 from the fourth reference point A4 (the second reference point A2) in the second image T2 to the boundary of the second electrode tab 2. At this time, d3 - d4 - (d1 - d2) is the offset amount between the actual boundaries of the first electrode tab 1 and the second electrode tab 2, that is, the offset amount of the actual electrode assembly 100 excluding the influence of the first camera 41 and the second camera 42. Based on this, it is possible to more accurately determine whether the electrode assembly 100 is offset.

[0066] Finally, it should be noted that this application is not limited to the above embodiments. The above embodiments are only illustrative, and embodiments having the same structure in essence as the technical idea and achieving the same effect within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that those skilled in the art can think of to the embodiments and other ways of combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. An offset detection method, characterized in that, Used to detect the position offset during the winding of the electrode assembly, the electrode assembly includes a first pole piece, a second pole piece and a separator, and the offset detection method includes: Obtaining a first image and a second image through a first camera and a second camera respectively. The first image includes an image of the first pole piece of the electrode assembly during the winding process, and the second image includes an image of the second pole piece of the electrode assembly during the winding process; A camera offset judgment step, determining whether the first camera and / or the second camera is offset according to the distance from a reference point in the first image and / or a reference point in the second image to a specific position, where the specific position is the position of the same object that appears in the first image and the second image; An electrode assembly offset determination step, when it is determined that the first camera and the second camera have not been offset, determining whether the electrode assembly is offset according to the vertical distance from the reference point in the first image to the boundary of the first pole piece and the vertical distance from the reference point in the second image to the boundary of the second pole piece.

2. The offset detection method according to claim 1, wherein The camera offset judgment step includes: Obtaining a first distance according to the first image, where the first distance is the distance from a first reference point to the specific position; Obtaining a second distance according to the second image, where the second distance is the distance from a second reference point to the specific position; When the difference between the first distance and the second distance is greater than a first threshold, it is determined that a relative displacement occurs between the first camera and the second camera.

3. The offset detection method according to claim 1, wherein The camera offset judgment step includes: Obtaining a first distance according to the first image, where the first distance is the distance from a first reference point to the specific position; Obtaining a second distance according to the second image, where the second distance is the distance from a second reference point to the specific position; When the first distance exceeds the first distance reference value range, it is determined that the first camera is offset; When the second distance exceeds the second distance reference value range, it is determined that the second camera is offset.

4. The offset detection method according to any one of claims 1-3, characterized in that The specific position is the boundary of the separator, or the specific position is the position where the laser irradiates the electrode assembly; Wherein, the laser is emitted by a laser and irradiates the electrode assembly to generate a pixel boundary in the first image and the second image.

5. The offset detection method according to claim 2, wherein The electrode assembly offset determination step includes: Obtaining a third distance according to the first image, where the third distance is the vertical distance from a third reference point to the boundary of the first pole piece; Obtaining a fourth distance according to the second image, where the fourth distance is the vertical distance from a fourth reference point to the boundary of the second pole piece; When the difference between the first distance and the second distance is less than or equal to the first threshold, and the difference obtained by subtracting the preset distance between the boundary of the first pole piece and the boundary of the second pole piece from the difference between the third distance and the fourth distance is greater than a second threshold, it is determined that the electrode assembly is offset.

6. The offset detection method according to claim 2, wherein The electrode assembly offset determination step includes: Obtain a third distance according to the first image, where the third distance is the perpendicular distance from a third reference point to the boundary of the first pole piece; Obtain a fourth distance according to the second image, where the fourth distance is the perpendicular distance from a fourth reference point to the boundary of the second pole piece; When the difference between the first distance and the second distance is less than or equal to the first threshold, and the third distance exceeds the range of the third distance reference value, it is determined that the first pole piece is offset; When the difference between the first distance and the second distance is less than or equal to the first threshold, and the fourth distance exceeds the range of the fourth distance reference value, it is determined that the second pole piece is offset.

7. The offset detection method according to claim 2, wherein The electrode assembly offset determination step includes: Obtain a third distance in the first image, where the third distance is the perpendicular distance from a third reference point to the boundary of the first pole piece, and obtain a fourth distance in the second image, where the fourth distance is the perpendicular distance from a fourth reference point to the boundary of the second pole piece; When the difference obtained by subtracting the preset distance between the boundary of the first pole piece and the boundary of the second pole piece from the difference between the third distance and the fourth distance, and then subtracting the difference between the first distance and the second distance is greater than the third threshold, it is determined that the electrode assembly is offset.

8. The offset detection method according to any one of claims 1-3, characterized in that The second camera uses an infrared light source to penetrate one layer of the separator film to photograph the second pole piece behind it.

9. The offset detection method according to any one of claims 1-3, characterized in that The separator film includes a first separator film and a second separator film; The first image includes the first pole piece and the first separator film; The second image includes the second pole piece and the second separator film; The specific position is the boundary where the second separator film exposes the first separator film or the boundary where the first separator film exposes the second separator film.

10. An offset detection device, characterized in that, For detecting the position offset during the winding of the electrode assembly, the electrode assembly includes a first pole piece, a second pole piece and a separator film, and the offset detection device includes: A first camera and a second camera, which respectively obtain a first image and a second image. The first image includes an image of the first pole piece during the winding process of the electrode assembly, and the second image includes an image of the second pole piece during the winding process of the electrode assembly; And an offset determination unit, which determines whether the first camera and the second camera are offset according to the distances from the reference points in the first image and the reference points in the second image to the specific position. When it is determined that the first camera and the second camera are not offset, it determines whether the electrode assembly is offset according to the perpendicular distance from the reference point in the first image to the boundary of the first pole piece and the perpendicular distance from the reference point in the second image to the boundary of the second pole piece.

Images