WO2023050064A1 - 偏移检测方法及偏移检测装置 - Google Patents

偏移检测方法及偏移检测装置 Download PDF

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Publication number
WO2023050064A1
WO2023050064A1 PCT/CN2021/121336 CN2021121336W WO2023050064A1 WO 2023050064 A1 WO2023050064 A1 WO 2023050064A1 CN 2021121336 W CN2021121336 W CN 2021121336W WO 2023050064 A1 WO2023050064 A1 WO 2023050064A1
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Prior art keywords
distance
image
pole piece
camera
offset
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PCT/CN2021/121336
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English (en)
French (fr)
Inventor
王绪明
陈继伟
张园园
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宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to CN202180068098.2A priority Critical patent/CN116348734A/zh
Priority to KR1020237015604A priority patent/KR102574401B1/ko
Priority to PCT/CN2021/121336 priority patent/WO2023050064A1/zh
Priority to EP21958663.3A priority patent/EP4230953A4/en
Priority to JP2023527050A priority patent/JP7407339B2/ja
Publication of WO2023050064A1 publication Critical patent/WO2023050064A1/zh
Priority to US18/332,491 priority patent/US11933598B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/028—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring lateral position of a boundary of the object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/022—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by means of tv-camera scanning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/03—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring coordinates of points
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0404—Machines for assembling batteries
    • H01M10/0409—Machines for assembling batteries for cells with wound electrodes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/40—Caliper-like sensors
    • G01B2210/44—Caliper-like sensors with detectors on both sides of the object to be measured
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of battery manufacturing, and in particular to an offset detection method and an offset detection device, which are used to detect the position offset of the electrode assembly when the electrode assembly is manufactured by winding.
  • the electrode assembly as a part of the battery cell where the electrochemical reaction occurs, is generally formed by winding or stacking the first pole piece, the second pole piece and the separator.
  • the first pole piece, the second pole piece and the separator are prone to deflection, which makes the first pole piece, the second pole piece and the separator deviate from their normal positions.
  • the quality of the electrode assembly winding directly affects the performance of the battery cell. Therefore, how to accurately detect the offset of the electrode assembly is very important for battery manufacturing.
  • the present invention provides an offset detection method and an offset detection device, which can accurately detect the position offset when the electrode assembly is wound.
  • a displacement detection method which is used to detect the position displacement of an electrode assembly during winding, the electrode assembly includes a first pole piece, a second pole piece and a separator, the displacement detection method
  • the method includes: acquiring 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 the electrode assembly The image of the second pole piece during the winding process of the component; the camera offset determination step, according to the reference point in the first image and the distance from the reference point in the second image to a specific position, determine the first Whether the camera and the second camera are offset, the specific position is the position of the same object appearing in the first image and the second image; the electrode assembly offset determination step, when determining the first When the camera and the second camera are not offset, according to the vertical distance from the reference point in the first image to the boundary of the first pole piece and the reference point in the second image to the boundary of the second pole piece to determine whether the
  • the prerequisite for accurately determining the positional displacement of the electrode assembly is that the first camera and the second camera are in the correct position.
  • only the first image acquired by the first camera and the second image acquired by the second camera can be used to determine the camera position offset and the electrode assembly position offset, without the need for a separate Camera position offset determination additionally acquires images. Therefore, it is possible to ensure that the first camera and the second camera are in the correct position with low cost and high efficiency, and on this premise, the positional deviation of the electrode assembly can be accurately judged.
  • the camera offset determination step includes: acquiring a first distance according to the first image, the first distance being the distance from the first reference point to the specific position; acquiring a second distance according to the second image , the second distance is the distance from the 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 the first camera and the second Relative displacement between cameras.
  • 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 particular location appears in both the first image and the second image, and also corresponds to a 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.
  • the difference with the first threshold it can be easily determined whether a relative displacement occurs between the first camera and the second camera.
  • the camera offset determining step includes: obtaining a first distance in the first image, the first distance being the distance from the first reference point to the specific position, and obtaining in the second image Acquiring a second distance, the second distance being the distance from the 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 is offset; when the When the second distance exceeds the range of the second distance reference value, it is determined that the second camera is offset.
  • the specific position is the boundary of the separator, or, the specific position is the position where the laser is irradiated on the electrode assembly, wherein the laser is emitted by the laser and irradiated on the battery assembly, for A pixel boundary is generated in the first image and the second image.
  • the isolation film appears in both the first image and the second image, and the edge of the isolation film exceeds the edge of the first pole piece and the second pole piece, which is easy to identify. Therefore, by setting the boundary of the isolation film at a specific position, it is possible to easily determine the positional displacement of the first camera and the second camera without additionally introducing other devices.
  • a specific position can also be generated in the first image and the second image by means of laser light, and the positional offset of the first camera and the second camera can be determined.
  • the electrode assembly offset determination step includes: acquiring a third distance in the first image, the third distance being the vertical distance from the third reference point to the boundary of the first pole piece, A fourth distance is obtained from the second image, the fourth distance is the vertical distance from the 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 (absolute value) obtained by subtracting the preset distance between the first pole piece boundary and the second pole piece boundary from the difference between the third distance and the fourth distance When it is greater than the second threshold, it is determined that the electrode assembly is offset. Therefore, under the premise of ensuring that the first camera and the second camera are in the correct position, it is still possible to accurately determine whether the position of the electrode assembly is shifted when it is wound, through the first image and the second image,
  • the electrode assembly offset determination step includes: acquiring a third distance in the first image, the third distance being the vertical distance from the third reference point to the boundary of the first pole piece, A fourth distance is obtained from the second image, the fourth distance is the vertical distance from the 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, and when the difference between the first distance and the second distance is less than or equal to the When the first threshold is set and the fourth distance exceeds the range of a fourth distance reference value, it is determined that the second pole piece is offset.
  • the electrode assembly offset determination step includes: acquiring a third distance in the first image, the third distance being the vertical distance from the third reference point to the boundary of the first pole piece, A fourth distance is obtained from the second image, and the fourth distance is the vertical distance from the fourth reference point to the boundary of the second pole piece.
  • the difference between the third distance and the fourth distance is subtracted After the preset distance between the first pole piece boundary and the second pole piece boundary, the difference (absolute value) obtained by 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.
  • 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.
  • the second camera uses an infrared light source to penetrate a layer of the isolation film to take pictures of the second pole piece thereafter. In this way, the second pole piece can be identified in the second image, and the fourth distance can be obtained to compare with the third distance to determine whether the electrode assembly is displaced during winding.
  • the separator includes a first separator and a second separator
  • the first image includes the first pole piece and the first separator
  • the second image includes the second pole piece and the second
  • the specific position is a boundary where the second isolation film is exposed to the first isolation film or a boundary where the first isolation film is exposed to the second isolation film.
  • an offset detection device for detecting position offset of an electrode assembly during winding, the electrode assembly includes a first pole piece, a second pole piece and a separator, and the offset detection device includes : a first camera and a second camera, respectively acquire a first image and a second image, the first image includes the image of the first pole piece of the electrode assembly during the winding process, and the second image includes the electrode An image of the second pole piece during the winding process of the assembly; and an offset determination unit, which determines the distance between the reference point in the first image and the reference point in the second image to a specific position Whether the camera and the second camera are offset, when it is determined that the first camera and the second camera are not offset, according to the vertical distance from the reference point in the first image to the boundary of the first pole piece The distance and the vertical distance from the reference point in the second image to the boundary of the second pole piece are used to determine whether the electrode assembly is offset.
  • FIG. 1 is a schematic diagram of an electrode assembly manufacturing equipment including an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a wound electrode assembly according to an embodiment of the present application.
  • FIG 3 is a cross-sectional view including an X-Y cross-section of a wound electrode assembly according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of an expanded electrode assembly according to an embodiment of the present application.
  • FIG. 5 is a flowchart of an offset detection method according to an embodiment of the present application.
  • Fig. 6 is a schematic diagram of a first image and a second image according to an embodiment of the present application.
  • FIG. 7 is a diagram showing the displacement of the actual electrode assembly when the position of the first camera and the second camera deviate within an acceptable range according to an embodiment of the present application.
  • FIG. 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.
  • connection In the description of this application, it should be noted that, unless otherwise clearly stipulated and limited, the terms “installation”, “connection”, “connection” and “attachment” should be understood in a broad sense, for example, it may be a fixed connection, It can also be detachably connected or integrally connected; it can be directly connected or indirectly connected through an intermediary, and it can be internal communication between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application according to specific situations.
  • Multiple appearing in this application refers to more than two (including two), similarly, “multiple groups” refers to more than two groups (including two groups), and “multi-piece” refers to more than two (Includes two pieces).
  • FIG. 1 is a schematic diagram of an electrode assembly manufacturing equipment including an embodiment of the present application.
  • FIG. 2 illustrates the electrode assembly 100 formed by winding.
  • the electrode assembly manufacturing equipment includes a conveying device and a winding device, that is, a winding needle 5 .
  • the conveying device Through the conveying device, the belt-shaped first pole piece 1, second pole piece 2 and separator 3 are transported to the winding needle 5, and the first pole piece 1, separator 3, second pole piece 2 and separator 3 are stacked in sequence. Then wind it on the winding needle 5 and form the electrode assembly 100 (refer to FIG. 2 ).
  • the winding pin 5 in Fig. 1 is only for illustration. According to the type of the battery cell and the shape of the battery case, the electrode assembly can be wound into a cylindrical electrode assembly or an oval electrode assembly (as shown in Fig. 2, Fig. 3).
  • FIG. 3 is a cross-sectional view of the electrode assembly 100 shown in FIG. 2 on the X-Y plane. As shown in FIG.
  • the first separator 31 and the second separator 32 separate the second pole piece 2 from the first pole piece 1 .
  • FIG. 4 is a development view along the Y direction of the stacked and wound electrode assembly 100 .
  • the separator 3 including the first separator 31, the second separator 32
  • the second Pole piece 2 and first pole piece 1.
  • the electrode assembly manufacturing device further includes a photographing unit 4 .
  • the shooting unit takes pictures of the wound electrode assembly 100, and identifies the second pole piece 2 and the first pole piece 1 in the obtained image, so as to determine the relative positional relationship between the second pole piece 2 and the first pole piece 1 .
  • the second separator 32 , the second pole piece 2 and the first separator 31 need to be penetrated. Due to the limitation of the existing shooting unit, for example, the penetrating ability of the infrared shooting unit is very limited, it is difficult to accurately identify the second Pole piece 2 and first pole piece 1 and determine their relative positional relationship. Therefore, it is necessary to use the images of the first pole piece 1 and the second pole piece 2 respectively, corresponding to the first image T1 and the second image T2, respectively, to determine the pole piece position offset.
  • the first image T1 and the second image T2 are captured by the shooting units of the first camera 41 and the second camera 42 respectively.
  • the first image T1 includes the first pole piece 1 of the electrode assembly 100 during the winding process
  • the second image T2 includes the second pole piece 2 of the electrode assembly 100 during the winding process.
  • the ensuing problem is that it must first ensure that the relative relationship between the coordinate system 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 the preset position without offset.
  • FIG. 5 is a flowchart of an offset detection method 200 according to an embodiment of the present application.
  • Fig. 6 is a schematic diagram of a first image and a second image according to an embodiment of the present application. As shown in FIG. 5 and FIG.
  • the offset detection method 200 includes: acquiring a first image T1 and a second image T2 through the first camera 41 and the second camera 42 respectively, the first image T1 includes the electrode assembly 100 being wound The image of the first pole piece 1 during the winding process, the second image T2 includes the image of the second pole piece 2 during the winding process of the electrode assembly 100; the camera offset determination step, according to the reference point in the first image T1 and the second image The distance from the reference point in T2 to the specific position 6 determines whether the first camera 41 and the second camera 42 are offset, and the specific position 6 is the position of the same object appearing in the first image T1 and the second image T2; Component offset determination step, when it is determined that the first camera 41 and the second camera 42 are not 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 in the second image T2 The vertical distance from the reference point to the boundary of the second pole piece 2 is used to determine whether the electrode assembly 100 is offset.
  • the specific position 6 appears in both the first image T1 and the second image T2 , and corresponds to a fixed point of the electrode assembly 100 .
  • reference points with corresponding relationships are set in the first image T1 and the second image T2 in advance, as long as the first camera 41 and the second camera 42 do not shift, the reference points in the first image T1 and the second image T2
  • the points respectively correspond to fixed points of the electrode assembly 100 , that is, the difference between the distance from the reference point to the specific position 6 in the first image T1 and the distance from the reference point to the specific position 6 in the second image T2 is fixed. Therefore, according to the distance from the reference point to the specific position 6 in the first image T1 and the distance from the reference point to the specific position 6 in the second image T2, it can be determined whether the first camera 41 and the second camera 42 are offset.
  • the electrode assembly 100 is shifted by using the first image T1 and the second image T2. That is, there is no need to additionally acquire an image separately for camera position shift determination. Therefore, it is possible to ensure that the first camera 41 and the second camera 42 are in the correct position with low cost and high efficiency, and on this premise, the positional deviation of the electrode assembly can be accurately judged.
  • the specific position 6 is the boundary of the separator 3, or, the specific position 6 is the position where the laser is irradiated on the electrode assembly, wherein the laser is emitted by the laser and irradiated on the battery assembly, for the first image T1 and the second image T2 produce pixel boundaries. It is shown in Fig. 6 that the specific position 6 is the boundary of the isolation film 3 on the side away from the tabs 11, 22, but the application is not limited thereto, and the specific position 6 may also be the boundary of the isolation film 3 on the side of the tabs 11, 22 .
  • the specific position 6 is the position where the laser is irradiated on the electrode assembly
  • Two lasers can also be used in this application, but issues such as alignment of the two lasers need to be considered.
  • the first pole piece 1 is located on the outermost side along the X-axis direction, and the first pole piece 1 is followed by the first separator 31, The second pole piece 2 and the second isolation film 32 .
  • the first pole piece 1 and the first separating membrane 31 can be recognized.
  • the second separator 32 is located on the outermost side along the X-axis direction, and below the second separator 32 are the second pole piece 2 and the first separator 31 in sequence. and the first pole piece 1.
  • the second separating membrane 32 and the second pole piece 2 can be recognized in the second image T2 .
  • the edge of the first isolation film 31 exceeds the edge of the first pole piece 1
  • the edge of the second isolation film 32 exceeds the edge of the second pole piece 2 Therefore, it is easy to
  • the boundary of the first isolation film 31 and the boundary of the second isolation film 32 are recognized in the first image T1 and the second image T2.
  • the boundary of the first isolation film 31 and the boundary of the second isolation film 32 are aligned in the Z-axis direction, that is, the boundary of the first isolation film 31 on the first image T1 corresponds to the second Border 32 of the second isolation film on image T2. Therefore, the boundary of the isolation film 3 appears in both the first image T1 and the second image T2 , and corresponds to the same position as the electrode assembly 100 . Thus, by setting the boundary of the isolation film 3 at a specific position, it is possible to easily determine the positional displacement of the first camera 41 and the second camera 42 without additionally introducing other devices.
  • the camera offset determination step of the offset detection method 200 includes: according to the first image T1, obtain a first distance d1, the first distance d1 is from the first reference point A1 to the specific position 6 along the Z axis The distance in the direction; according to the second image T2, obtain the second distance d2, 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 When the first threshold is reached, it is determined that a relative displacement occurs between the first camera 41 and the second camera 42 .
  • the first distance d1 is the pixel point from the first reference point A1 to the specific position 6 along the Z-axis direction multiplied by the pixel equivalent
  • the second distance d2 is the pixel point from the second reference point A2 to the specific position 6 along the Z-axis direction multiplied by in pixel equivalents.
  • the pixel equivalent is the actual distance represented by one pixel point. For example, in the first image T1, it can be divided by the actual width of the first pole piece 1 on the Z axis by the total distance of the first pole piece 1 in the first image T1. obtained from the pixel value.
  • the first reference point A1 always corresponds to the fixed point of the first pole piece 1, that is, in the first image, the first reference point A1
  • the distance d1 in the Z-axis direction to the specific position 6 is fixed.
  • the distance d2 along the Z-axis direction from the second reference point A2 to the specific position 6 is also fixed. Therefore, the difference between the first distance d1 and the second distance d2 is also fixed.
  • the probability that the first camera 41 and the second camera 42 are shifted at the same time is very small. Therefore, it is not necessary to determine the positional deviation of the first camera 41 and the second camera 42 separately, thereby improving the determination efficiency.
  • the first reference point A1 can be determined as follows: When the first cameras 41 and 42 are line-scan cameras, adjust the field of view of the first camera 41 so that the center of the first pole piece 1 in the Z-axis direction The point appears in the middle position of the first image T1, that is, the midpoint on the Z-axis direction of the first pole piece 1 coincides with the pixel median point on the Z-axis direction of the first image T1 (for example, the first image T1 is at There are 4096 pixels in the Z-axis direction, the pixel median point is the 2048th pixel point), and the first reference point A1 is set as the pixel median point of the first image T1 in the Z-axis direction.
  • the second reference point A2 can also be determined: adjust the field of view of the second camera 42 so that the midpoint on the Z-axis direction of the second pole piece 2 coincides with the pixel median point on the Z-axis direction of the second image T2, and
  • the second reference point A2 is set as the pixel median point in the Z-axis direction of the second image T2.
  • 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
  • the second reference point A2 is the pixel point corresponding to the Z-axis direction of the second pole piece 2
  • the specific position 6 of the first image T1 and the second image T2 all corresponds to the boundary of the isolation film 3, and in an ideal case, the midpoint of the first pole piece 1 coincides with the midpoint of the second pole piece 2, then ideally
  • 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 2 to the specific position 6 .
  • the first threshold for example, 0.15 mm
  • first reference point A1 and the second reference point A2 are not limited to the pixel median point, the first reference point A1 and the second reference point A2 can be selected arbitrarily, as long as the first distance d1 and The relationship between the second distances d2 only needs to be determined.
  • the obtained first image T1 and second image T2 are a one-dimensional line.
  • the first camera 41 and the second camera 42 may not be line-scan cameras.
  • the first image T1 and the second image T2 are two-dimensional images, that is, have a certain length in the Y direction.
  • the same operation as that of the line scan camera can be performed on the same position in the Y direction in the first image T1 and the second image T2, or Let the first distance d1 and the second distance d2 be average distances in the entire Y direction.
  • the camera offset determination step of the offset detection method 200 includes: obtaining a first distance d1 in the first image T1, the first distance d1 is from the first reference point A1 to a specific position 6 along the Z axis The distance in the direction, the second distance d2 is obtained in the second image T2, 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 is offset; when the second distance d2 exceeds the second distance reference value range d2_ref, it is determined that the second camera 42 is offset.
  • the first distance d1 and the second distance d2 can be determined whether the position of the first camera 41 and the second camera 42 has shifted, compared to the determination of the first distance d1
  • the relationship between the distance d2 and the second distance can more accurately determine which camera has a position offset.
  • the comparison between the first distance d1 and the first distance preset value d1_ref and the second distance d2 and the second distance preset value d2_ref is performed, so as to be more accurate It is possible to accurately know which camera has shifted in position.
  • the electrode assembly offset determination step of the offset detection method 200 includes: acquiring a third distance d3 in the first image T1, the third distance d3 being the third reference point A3 to the first pole piece 1 The vertical distance of the border, obtain the fourth distance d4 in the second image T2, the fourth distance d4 is the vertical distance from the fourth reference point A4 to the border of the second pole piece 2, when the first distance d1 and the second distance d2 When the difference 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 1 and the boundary of the second pole piece 2 from the difference between the third distance d3 and the fourth distance d4 is greater than the second threshold, It was determined that the electrode assembly 100 was shifted.
  • the more important parameter in the process of winding the electrode assembly is the alignment of the electrode assembly 100 in the Z-axis direction after winding, especially the perpendicularity between the boundary of the first pole piece 1 and the boundary of the second pole piece 2.
  • distance Under the premise of ensuring that the first camera 41 and the second camera 42 are in the correct position (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, through the second The difference between the three distances d3 and the fourth distance d4 can obtain the vertical distance between the boundary of the first pole piece 1 and the boundary of the second pole piece 2, and then the obtained boundary of the first pole piece 1 and the boundary of the second pole piece 2 By comparing the vertical distance between them with its preset distance, it can be accurately determined whether the position of the electrode assembly 100 is shifted when it is wound.
  • the third reference point A3 may coincide with the first reference point A1 .
  • the fourth reference point A4 may coincide with the second reference point A2.
  • the third reference point A3 and the fourth reference point A4 are not limited thereto, as long as the relationship between the third distance d3 and the fourth distance d4 thus obtained is determined.
  • the electrode assembly offset determination step of the offset detection method 200 includes: acquiring a third distance d3 in the first image T1, the third distance d3 being the third reference point A3 to the first pole piece 1 The vertical distance of the border, obtain the fourth distance d4 in the second image T2, the fourth distance d4 is the vertical distance from the fourth reference point A4 to the border of the second pole piece 2, when the first distance d1 and the second distance d2 When the difference is less than or equal to the first threshold, and the third distance d3 exceeds the range of the third distance reference value d3_ref, it is determined that the first pole piece 1 is offset.
  • the third distance d3 and the fourth distance d4 first to determine whether the electrode assembly 100 has a positional shift during winding.
  • the third distance d3 is compared with the third distance preset value d3_ref and the fourth distance d4 is compared with the fourth distance preset value d4_ref, so as to know more accurately Which pole piece is shifted in position.
  • the position of the electrode assembly 100 does not shift during winding, there is no need to compare the third distance d3 and the fourth distance d4 with the preset values d3_ref and d4_ref, thereby improving the efficiency of shift determination.
  • the electrode assembly offset determination step of the offset detection method 200 includes: acquiring a third distance d3 in the first image T1, the third distance d3 being the third reference point A3 to the first pole piece 1 The vertical distance of the border, obtain the fourth distance d4 in the second image T2, the fourth distance d4 is the vertical distance from the fourth reference point A4 to the border of the second pole piece 2, when the third distance d3 and the fourth distance d4 When the difference obtained by subtracting the preset distance between the first pole piece boundary and the second pole piece boundary and then subtracting 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 shifted.
  • the offset between the boundary of the first pole piece 1 and the boundary of the second pole piece 2 includes two parts, that is, in the first and second images T1 and T2 caused by the first camera 41 and the second camera 42 The coordinate system deviation d1-d2, and the actual offset between the boundary of the first pole piece 1 and the boundary of the second pole piece 2.
  • the actual offset between the boundary of the first pole piece 1 and the boundary of 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.
  • the influence of the positional deviation of the first camera 41 and the second camera 42 can be eliminated, and the positional deviation of the electrode assembly 100 can be determined more accurately.
  • FIG. 7 a case 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 is shown.
  • the present application is not limited thereto, and the first to fourth reference points A1 to A4 can be selected arbitrarily, as long as it is satisfied that d3 and d4 obtained from the third reference point A3 and the fourth reference point A4 have a definite corresponding relationship, d1 and d2 obtained from the first reference point A1 and the second reference point A2 have a definite corresponding relationship, and d1-d2 is the first and second images T1 and T2 caused by the first camera 41 and the second camera 42 The coordinate system deviation of .
  • the second camera 42 uses an infrared light source to penetrate a layer of isolation film to take pictures of the second pole piece 2 thereafter.
  • the second pole piece 2 is located under the second isolation film 32 . Therefore, using an infrared camera that can penetrate the second isolation film 32 can ensure that the second pole piece 2 is identified in the second image T2, and then obtain the fourth distance d4, which can be compared with the third distance d3 to determine the electrode assembly 100 Whether positional deviation occurs during winding.
  • the isolation membrane 3 includes a first isolation membrane 31 and a second isolation membrane 32
  • the first image T1 includes the first pole piece 1 and the first isolation membrane 31
  • the second image T2 includes the second pole piece 2 and the second isolation film 32
  • the specific position 6 is the boundary where the second isolation film 32 is exposed to the first isolation film 31 or the boundary where the first isolation film 31 is exposed to the second isolation film 32 .
  • FIG. 8 shows an example in which the first isolation film 31 is exposed from the second isolation film 32 .
  • the first isolation film 31 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 taken as the specific position 6 .
  • the first isolation film 31 in the second image T2, although the first isolation film 31 is located under the second isolation film 32, since the first isolation film 31 is exposed from the second isolation film 32, the first isolation film 31 can also be recognized in the second image T2. Boundary of film 31 and set it as specific position 6. Therefore, the specific position 6 in the first image T1 corresponds to the specific position 6 in the second image T2 , and both are boundaries of the first isolation film 31 .
  • the time of acquiring the second image T2 is later than the time of acquiring the first image T1, and the 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 Certainly.
  • the captured first image T1 and second image T2 can display the first pole piece 1 and the second pole piece 2 at the same position after winding, so that the first pole piece at the same position can be 1 and the second pole piece 2 to perform position offset detection, which can make the detection result more accurate.
  • an offset detection device for detecting the position offset of the electrode assembly during winding.
  • the electrode assembly 100 includes a first pole piece 1, a second pole piece 2 and a separator 3.
  • the displacement detection device includes: a first camera 41 and a second camera 42, which respectively acquire 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 The image T2 includes the image of the second pole piece 2 during the winding process of the electrode assembly 100; and the offset determination unit, according to the distance from the reference point in the first image T1 and the reference point in the second image T2 to a specific position 6, Determine whether the first camera 41 and the second camera 42 have shifted, and when it is judged that the first camera 41 and the second camera 42 have not shifted, according to the distance between the reference point in the first image T1 and the boundary of the first pole piece 1 The vertical distance and the vertical distance from the reference point in the second image T2 to the boundary of
  • the present application provides an offset detection method 200, including the following steps:
  • the first image T1 and the second image T2 are acquired by the first camera 41 and the second camera 42, the first image T1 includes the image of the first pole piece 1 during the winding process of the electrode assembly 100, and the second image T2 includes the electrode assembly 100 Image of the second pole piece 2 during winding;
  • the first reference point A1 in the first image T1 is set 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, among the pixels The value point is the 2096th pixel point), the second reference point A2 in the second image T2 is set as the pixel median point in the Z-axis direction of the second image T2, and the specific position 6 is set as the boundary of the isolation film 3 .
  • a first distance d1 from the first reference point A1 in the first image T1 to the boundary of the isolation film 2 and a second distance d2 from the second reference point A2 in the second image T2 to the specific position 6 are obtained.
  • first distance d1 and the second distance d2 By comparing the first distance d1 and the second distance d2 with a first threshold, it is determined whether the first camera 41 and/or the second camera 42 is offset. When the first camera 41 and or the second camera 42 deviate, further compare d1 with the first distance preset value d1_ref and d2 with the second distance preset value d1_ref, so as to more accurately determine the first camera 41 and the second camera 42 which camera is offset.
  • the electrode assembly 100 is offset.
  • the third reference point A3 is set to coincide with the first reference point A1
  • the fourth reference point A4 is set to coincide with the second reference point A2.
  • the first distance d3 from the third reference point A3 (first reference point A1) in the first image T1 to the boundary of the first pole piece 1 and the fourth reference point A4 (second reference point A4) in the second image T2 are obtained.
  • d3-d4-(d1-d2) is the offset between the boundary of the actual first pole piece 1 and the boundary of the second pole piece 2, that is, the influence of the first camera 41 and the second camera 42 has been excluded , the offset of the actual electrode assembly 100 . Accordingly, it is possible to more accurately determine whether the electrode assembly 100 is shifted.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same function and effect are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供一种用于检测电极组件卷绕时的位置偏移的偏移检测方法，其包括：通过第一相机和第二相机获取第一图像和第二图像，第一图像包括电极组件在卷绕过程中第一极片的图像，第二图像包括电极组件在卷绕过程中第二极片的图像；根据第一图像中的基准点和第二图像中的基准点到特定位置的距离，判定第一相机和第二相机是否发生偏移，当判定第一相机和第二相机未发生偏移时，根据第一图像中的基准点到第一极片的边界的垂直距离和第二图像中的基准点到第二极片的边界的垂直距离，判定电极组件是否发生偏移。由此，通过第一图像和第二图像，既可以判定第一相机、第二相机是否发生位置偏移，又可以在相机未发生偏移的前提下进一步判定电极组件的位置偏移。

Description

偏移检测方法及偏移检测装置 技术领域
本申请涉及电池制造领域，尤其涉及一种偏移检测方法及偏移检测装置，用于在卷绕制造电极组件时检测电极组件的位置偏移。
背景技术
电极组件作为电池单体中发生电化学反应的部件，一般由第一极片、第二极片和隔离膜卷绕或层叠放置形成。在电极组件卷绕过程中，第一极片、第二极片和隔离膜容易出现偏摆现象，使得第一极片、第二极片和隔离膜偏离正常位置。而电极组件卷绕的好坏直接影响电池单体的性能。因此，如何能准确地对电极组件进行偏移检测对于电池制造至关重要。
发明内容
鉴于上述问题，本发明提供了一种偏移检测方法及偏移检测装置，可以准确地检测卷绕电极组件时的位置偏移。
第一方面，提供了一种偏移检测方法，用于检测电极组件卷绕时的位置偏移，所述电极组件包括第一极片、第二极片和隔离膜，所述偏移检测方法包括：通过第一相机和第二相机获取第一图像和第二图像，所述第一图像包括所述电极组件在卷绕过程中第一极片的图像，所述第二图像包括所述电极组件在卷绕过程中第二极片的图像；相机偏移判定步骤，根据所述第一图像中的基准点和所述第二图像中的基准点到特定位置的距离，判定所述第一相机和所述第二相机是否发生偏移，所述特定位置是出现在所述第一图像和所述第二图像中的相同对象的位置；电极组件偏移判定步骤，当判定所述第一相机和所述第二相机未发生偏移时，根据所述第一图像中的基准点到第一极片的边界的垂直距离和所述第二图像中的基准点到第二极片的边界的垂直距离，判定所述电极组件是否发生偏移。
由于电极组件卷绕后，第一极片、第二极片和隔离膜叠覆，并且受拍摄单元的限制，需要利用第一相机获取的第一图片和第二相机获取的第二图片，来检测电极组件卷绕时的位置偏移。因此，精确判定电极组 件位置偏移的前提是第一相机和第二相机处于正确的位置。本申请实施例的技术方案中，仅通过第一相机获取的第一图像和第二相机获取的第二图像，就可以对相机位置偏移和电极组件位置偏移进行判定，而不需要单独为相机位置偏移判定额外获取图像。由此，可以以较小的成本且高效地确保第一相机、第二相机处于正确位置，并在此前提下精确地判电极组件的位置偏移。
在一些实施例中，相机偏移判定步骤包括：根据第一图像，获取第一距离，所述第一距离为第一基准点到所述特定位置的距离；根据第二图像，获取第二距离，所述第二距离为第二基准点到所述特定位置的距离；当所述第一距离和所述第二距离之差大于第一阈值时，判定所述第一相机和所述第二相机之间产生相对位移。本申请实施例的技术方案中，只要第一相机和/或第二相机未发生偏移，则第一图像的第一基准点和第二图像的第二基准点分别对应于电极组件的固定点，并且特定位置既出现在第一图像也出现在第二图像，也对应于电极组件的固定点。因此，第一基准点到特定位置的距离和第二基准点到特定位置的距离之差一定。由此，通过将该差值与第一阈值比较，可以容易地判定第一相机和第二相机之间是否产生相对位移。
在一些实施例中，相机偏移判定步骤包括：在所述第一图像中获取第一距离，所述第一距离为第一基准点到所述特定位置的距离，在所述第二图像中获取第二距离，所述第二距离为第二基准点到所述特定位置的距离，当所述第一距离超出第一距离参考值范围时，判定所述第一相机发生偏移；当所述第二距离超出第二距离参考值范围时，判定所述第二相机发生偏移。由此，通过分别将第一距离、第二距离与预设值比较，可以分别判定第一相机和第二相机是否发生位置偏移，相比于判定第一距离和第二距离之间的关系，可以更精确的判定哪个相机发生位置偏移。
在一些实施例中，所述特定位置为所述隔离膜的边界，或者，所述特定位置为激光照射于所述电极组件的位置，其中，所述激光由激光器发出并照射于电池组件，用于在所述第一图像和所述第二图像产生像素边界。本申请实施例的技术方案中，隔离膜既出现在第一图像中也出现在第二图像中，且隔离膜的边缘超过第一极片和第二极片的边缘，很容易识别。因此，通过将隔离膜的边界设为特定位置，无需额外引入其他 装置就可以容易地判定第一相机和第二相机的位置偏移。此外，通过激光也可以在第一图像和第二图像中产生特定位置，并判定第一相机和第二相机的位置偏移。
在一些实施例中，电极组件偏移判定步骤包括：在所述第一图像中获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，在所述第二图像中获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所述第三距离和所述第四距离之差减去所述第一极片边界与所述第二极片边界的预设距离而取得的差值(绝对值)大于第二阈值时，判定所述电极组件发生偏移。由此，在确保第一相机和第二相机处于正确位置的前提下，仍然通过第一图像和第二图像，就可以精确地判定电极组件卷绕时的位置是否发生偏移，
在一些实施例中，电极组件偏移判定步骤包括：在所述第一图像中获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，在所述第二图像中获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所述第三距离超出第三距离参考值范围时，判定所述第一极片发生偏移，当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所述第四距离超出第四距离参考值范围时，判定所述第二极片发生偏移。由此，通过分别将第三距离、第四距离与预设值比较，可以分别判定第一极片和第二极片是否发生位置偏移，相比于判定第三距离和第四距离之间的关系，可以更精确的判定哪个极片发生位置偏移。
在一些实施例中，电极组件偏移判定步骤包括：在所述第一图像中获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，在所述第二图像中获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，当所述第三距离和所述第四距离之差减去所述第一极片边界与所述第二极片边界的预设距离之后，再减去所述第一距离和所述第二距离之差而取得的差值(绝对值)大于第三阈值时，判定所述电极组件发生偏移。本申请实施例的技术方案中，第一距离和第二距离之差为第一相机和第二相机所引入的第一图像和第二图 像间的坐标系偏差。通过在第三距离和第四距离之差中进一步减去第一距离和第二距离之差，可以在进行电极组件卷绕时的位置判定时排除第一相机和第二相机的位置偏差，获得实际的第一极片边界和第二极片边界的距离，由此可以更精确地判定电极组件的位置偏移。
在一些实施例中，所述第二相机使用红外光源穿透一层所述隔离膜拍摄其后的所述第二极片。由此，可以确保在第二图像中识别第二极片，进而获得第四距离，以和第三距离进行比较，判定电极组件在卷绕时是否发生位置偏移。
在一些实施例中，所述隔离膜包括第一隔离膜和第二隔离膜，所述第一图像包括第一极片和第一隔离膜，所述第二图像包括第二极片和第二隔离膜，所述特定位置为所述第二隔离膜露出于所述第一隔离膜的边界或所述第一隔离膜露出于所述第二隔离膜的边界。由此，即使第一隔离膜和/或第二隔离膜发生位置偏移，也可以确保第一图像中的特定位置和第二图像中的特定位置相对应。
第二方面，提供一种偏移检测装置，用于检测电极组件卷绕时的位置偏移，所述电极组件包括第一极片、第二极片和隔离膜，所述偏移检测装置包括：第一相机和第二相机，分别获取第一图像和第二图像，所述第一图像包括所述电极组件在卷绕过程中第一极片的图像，所述第二图像包括所述电极组件在卷绕过程中第二极片的图像；以及偏移判定单元，根据所述第一图像中的基准点和所述第二图像中的基准点到特定位置的距离，判定所述第一相机和所述第二相机是否发生偏移，当判定所述第一相机和所述第二相机未发生偏移时，根据所述第一图像中的基准点到第一极片的边界的垂直距离和所述第二图像中的基准点到第二极片的边界的垂直距离，判定所述电极组件是否发生偏移。
附图说明
此处所说明的附图用来提供对本申请的进一步理解，构成本申请的一部分，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1是包含本申请一实施例的电极组件制造设备的示意图。
图2是本申请一实施例的卷绕后的电极组件的示意图。
图3是包含本申请一实施例的卷绕后的电极组件的X-Y截面的截面图。
图4是展开的本申请一实施例的电极组件的示意图。
图5是本申请一实施例的偏移检测方法的流程图。
图6是本申请一实施方式的第一图像和第二图像的示意图。
图7是示出本申请一实施方式的、第一相机和第二相机发生可接受范围内的位置偏移时实际电极组件的偏移量的图。
图8是示出本申请一实施方式的、第一隔离膜从第二隔离膜露出时特定位置的图。
附图标记说明：
100 电极组件
1 第一极片
11 第一极耳
2 第二极片
22 第二极耳
3 隔离膜
31 第一隔离膜
32 第二隔离膜
4 拍摄单元
41 第一相机
42 第二相机
5 卷针
6 特定位置
T1 第一图像
T2 第二图像
A1 第一基准点
A2 第二基准点
d1 第一距离
d2 第二距离
d3 第三距离
d4 第四距离
200 偏移检测方法
具体实施例
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
除非另有定义，本申请所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本申请中在申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。本申请的说明书和权利要求书或上述附图中的术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
在本申请中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本申请所描述的实施例可以与其它实施例相结合。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“附接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本申请中术语“和/或”，仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本申请中字符“/”，一般表示前后关联对象是一种“或”的关系。
本申请中出现的“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
图1是包含本申请一实施例的电极组件制造设备的示意图。图2示出通过卷绕形成的电极组件100。如图1所述，电极组件制造设备括输送装置和卷绕装置，即卷针5。通过输送装置，将带状的第一极片1、第二极片2和 隔离膜3输送至卷针5，第一极片1、隔离膜3、第二极片2以及隔离膜3依次叠置卷绕于卷针5并成型出电极组件100(参照图2)。图1中的卷针5仅为示意，按照电池单体的类型及电池壳体的形状，电极组件可以卷绕成截面为圆柱形的电极组件、或椭圆形的电极组件(如图2、图3所示)。
卷针5每旋转一周(360°)，电极组件100增加一层。如图2所示，随着卷针5的旋转，电极组件100在X方向上的厚度逐渐增加。此外，带状第一极片1、第二极片2和隔离膜3(包括第一隔离膜31和第二隔离膜32)的宽度决定了电极组件100在Z轴方向上的高度。图3是图2所示的电极组件100在X-Y平面上的截面图。如图3所示，对于每一卷绕层，沿X方向从外到内，依次为第二隔离膜32、第二极片2、第一隔离膜31以及第一极片1。由此，对于每一卷绕层，第一隔离膜31和第二隔离膜32隔开第二极片2和第一极片1。
在卷绕电极组件过程中较为重要的参数为卷绕后电极组件100在Z轴方向上的对齐度。具体而言，卷绕后的电极组件100在Z轴方向上的对齐度是第二极片2与第一极片1在Z轴方向上的相对位置。图4是叠置卷绕后的电极组件100沿Y方向的展开图。如图所示，在Z轴方向上(即，展开的电极组件100的宽度方向)，从外向内依次应为：隔离膜3(包括第一隔离膜31、第二隔离膜32)、第二极片2和第一极片1。即，在Z轴方向上，第一隔离膜31和第二隔离膜32边界平齐且位于最外侧，而第一极片1位于最内侧，并且第二极片2超出第一极片1规定距离(预设距离)。由于在卷绕电极组件100的过程中，第二极片2、第一极片1容易出现偏摆现象，使得第二极片2和第一极片1的相对位置发生偏移，从而影响制造的电池单体的质量和性能。因此，为了监测第二极片2和第一极片1的相对位置偏移情况，电极组件制造装置还包括拍摄单元4。
理想情况为拍摄单元拍摄卷绕后的电极组件100，并在获得的图像中识别第二极片2和第一极片1，以判定第二极片2和第一极片1的相对位置关系。但如上所述，对于电极组件的每一卷绕层，为拍摄第一极片1，需透过第二隔离膜32、第二极片2以及第一隔离膜31。由于现有拍摄单元的局限性，例如，红外线拍摄单元的穿透能力十分有限，在拍摄的卷绕后的第一极片1或第二极片2的图像中，很难准确识别出第二极片2和第一极片1并判定其相对位置关系。因此，需要利用分别拍摄有第一极片1和第 二极片2的图像，分别对应于第一图像T1和第二图像T2，进行极片位置偏移判定。
因此，通常利用第一相机41和第二相机42的拍摄单元分别拍摄第一图像T1和第二图像T2。第一图像T1包括电极组件100在卷绕过程中的第一极片1，第二图像T2包括电极组件100在卷绕过程中的第二极片2。但随之而来的问题是，必须首先确保第一图像T1中的坐标系和第二图像T2中的坐标系间的相对关系固定，即，第一相机41和第二相机42处于预设的位置，未发生偏移。
基于以上考虑，发明人经过深入研究，提出了一种用于检测电极组件100卷绕时的位置偏移的偏移检测方法200。图5是本申请的一实施例的偏移检测方法200的流程图。图6是本申请一实施方式的第一图像和第二图像的示意图。如图5、图6所示，该偏移检测方法200包括：通过第一相机41和第二相机42分别获取第一图像T1和第二图像T2，第一图像T1包括电极组件100在卷绕过程中第一极片1的图像，第二图像T2包括电极组件100在卷绕过程中第二极片2的图像；相机偏移判定步骤，根据第一图像T1中的基准点和第二图像T2中的基准点到特定位置6的距离，判定第一相机41和第二相机42是否发生偏移，特定位置6是出现在第一图像T1和第二图像T2中的相同对象的位置；电极组件偏移判定步骤，当判定第一相机41和第二相机42未发生偏移时，根据第一图像T1中的基准点到第一极片1的边界的垂直距离和第二图像T2中的基准点到第二极片2的边界的垂直距离，判定电极组件100是否发生偏移。
如上所述，为判定电极组件100是否发生偏移需要利用第一相机41拍摄的包含第一极片1的第一图像T1和第二相机42拍摄的包含第二极片2的第二图像T2。在本申请的实施例中，特定位置6既出现在第一图像T1中又出现在第二图像T2，并对应于电极组件100的固定点。此外，预先在第一图像T1和第二图像T2中设置具有对应关系的基准点，只要第一相机41和第二相机42未发生偏移，则第一图像T1和第二图像T2中的基准点就分别对应于电极组件100的固定点，即，第一图像T1中的基准点到特定位置6的距离与第二图像T2中的基准点到特定位置6的距离的差值是固定的。因此，根据第一图像T1中的基准点到特定位置6的距离与第二图像T2中的基准点到特定位置6的距离，可以判定第一相机 41和第二相机42是否发生偏移。然后，在判定第一相机41和第二相机42未发生偏移的基础上，仍然利用第一图像T1和第二图像T2，判定电极组件100是否发生偏移。即，不需要单独为相机位置偏移判定额外获取图像。由此，可以以较小的成本且高效的确保第一相机41、第二相机42处于正确位置，并在此前提下精确地判电极组件的位置偏移。
根据本申请的一些实施例，特定位置6为隔离膜3的边界，或者，特定位置6为激光照射于电极组件的位置，其中，激光由激光器发出并照射于电池组件，用于在第一图像T1和第二图像T2产生像素边界。图6中示出特定位置6是远离极耳11、22一侧的隔离膜3的边界，但本申请不限于此，特定位置6也可以是极耳11、22一侧的隔离膜3的边界。在特定位置6为激光照射于电极组件的位置的情况下，优选使用一个激光器，该激光器的照射点既可以被第一相机41也可以被第二相机42获取。本申请也可采用两个激光器，但需要考虑两个激光器的位置对准等的问题。
如图6所示，在拍摄有卷绕前电极组件100的第一图像T1中，第一极片1沿X轴方向位于最外侧，第一极片1的下方依次为第一隔离膜31、第二极片2以及第二隔离膜32。取决于拍摄单元4的穿透能力，在第一图像T1中，可以识别第一极片1和第一隔离膜31。在拍摄有卷绕后电极组件100的第二图像T2中，第二隔离膜32沿X轴方向位于最外侧，第二隔离膜32的下方的依次为第二极片2、第一隔离膜31以及第一极片1。取决于拍摄单元4的穿透能力，在第二图像T2中，至少可以识别第二隔离膜32和第二极片2。此外，在第一图像T1中，第一隔离膜31的边缘超过第一极片1，在第二图像T2中，第二隔离膜32的边缘超过第二极片2的边缘，因此，很容易在第一图像T1和第二图像T2中识别第一隔离膜31的边界和第二隔离膜32的边界。此外，如图4所示，第一隔离膜31的边界和第二隔离膜32的边界在Z轴方向上平齐，即，第一图像T1上的第一隔离膜31的边界对应于第二图像T2上的第二隔离膜的边界32。因此，隔离膜3的边界既出现在第一图像T1中又出现在第二图像T2中，且对应与电极组件100的同一位置。由此，通过将隔离膜3的边界设为特定位置，无需额外引入其他装置就可以容易地判定第一相机41和第二相机42的位置偏移。
也可以通过激光在第一图像T1和第二图像T2中产生特定位置6。由此，可以排除如第一隔离膜31和/或第二隔离膜32的制造误差或由第一隔离膜31和/或第二隔离膜32的偏移所带来的影响。在特定位置6为激光照射于电极组件的位置的情况下，优选使用一个激光器，该激光器的照射点既可以被第一相机41也可以被第二相机42获取。
根据本申请的一些实施例，偏移检测方法200的相机偏移判定步骤包括：根据第一图像T1，获取第一距离d1，第一距离d1为第一基准点A1到特定位置6沿Z轴方向的距离；根据第二图像T2，获取第二距离d2，第二距离d2为第二基准点A2到特定位置6沿Z轴方向的距离；当第一距离d1和第二距离d2之差大于第一阈值时，判定第一相机41和第二相机42之间产生相对位移。
第一距离d1为从第一基准点A1到特定位置6沿Z轴方向的像素点乘以像素当量，第二距离d2为从第二基准点A2沿Z轴方向到特定位置6的像素点乘以像素当量。此处，像素当量为一个像素点代表的实际距离，例如在第一图像T1中，可以通过第一极片1的Z轴的实际宽度除以第一极片1在第一图像T1中的总像素值而获得。
如果第一相机41未发生偏移，一旦确定第一基准点A1，则第一基准点A1就一直对应于第一极片1的固定点，即，在第一图像中，第一基准点A1到特定位置6沿Z轴方向的距离d1是固定的。同理，如果第二相机42未发生偏移，则第二基准点A2到特定位置6沿Z轴方向的距离d2也是固定的。因此，第一距离d1和第二距离d2之差也是固定的。一般情况下，第一相机41和第二相机42同时发生偏移的概率很小。因此，不必分别对第一相机41和第二相机42的位置偏移进行判定，从而提高判定效率。
如图6所示，可以如下确定第一基准点A1：当第一相机41、42为线扫相机时，调整第一相机41的视野范围，使得第一极片1的Z轴方向上的中点出现在第一图像T1的中间位置，即，第一极片1的Z轴方向上的中点和第一图像T1的Z轴方向上的像素中值点重合(例如，第一图像T1在Z轴方向上具有4096个像素，则像素中值点为第2048像素点)，将第一基准点A1设为第一图像T1的Z轴方向上的像素中值点。可以同样确定第二基准点A2：调整第二相机42的视野范围，使得第二极片2 的Z轴方向上的中点和第二图像T2的Z轴方向上的像素中值点重合，并将第二基准点A2设为第二图像T2的Z轴方向上的像素中值点。由此，第一基准点A1为对应于第一极片1的Z轴方向上的中点的像素点(第2048像素点)，第二基准点A2为对应第二极片2的Z轴方向上的中点的像素点(第2048像素点)。第一图像T1和第二图像T2的特定位置6均对应于隔离膜3的边界，并且在理想情况下，第一极片1的中点与第二极片2的中点重合，则理想情况下，如果第一相机41和第二相机42未发生偏移，则第一基准点A1到特定位置6的第一距离d1等于第二基准点2到特定位置6的第二距离d2。由此，通过将该差值与第一阈值(例如，0.15mm)比较，可以容易地判定第一相机和第二相机之间是否产生相对位移。应当注意的是，第一基准点A1和第二基准点A2并不局限于像素中值点，可以任意选择第一基准点A1和第二基准点A2，只要由此得到的第一距离d1和第二距离d2之间的关系确定即可。此外，当第一相机41、第二相机42是线扫相机时，所获得的第一图像T1和第二图像T2为一维的一条线。但第一相机41、第二相机42也可以不是线扫相机，此时，第一图像T1和第二图像T2为二维图像，即，在Y方向有一定长度。在第一图像T1和第二图像T2为二维的情况下，可以对第一图像T1和第二图像T2中某一相同的Y方向上的位置，进行与线扫相机相同的操作，也可以将第一距离d1和第二距离d2设为整个Y方向上的平均距离。
根据本申请的一些实施例，偏移检测方法200的相机偏移判定步骤包括：在第一图像T1中获取第一距离d1，第一距离d1为第一基准点A1到特定位置6沿Z轴方向的距离，在第二图像T2中获取第二距离d2，第二距离d2为第二基准点A2到特定位置6沿Z轴方向的距离，当第一距离d1超出第一距离参考值范围d1_ref时，判定第一相机41发生偏移；当第二距离d2超出第二距离参考值范围d2_ref时，判定第二相机42发生偏移。
由此，通过分别将第一距离d1、第二距离d2与预设值d1_ref、d2_ref比较，可以分别判定第一相机41和第二相机42是否发生位置偏移，相比于判定第一距离d1和第二距离d2之间的关系，可以更精确的判定哪个相机发生位置偏移。
也可以，先判定第一距离d1和第二距离d2之间的关系，确定第一 相机41和第二相机42是否发生位置偏移。当确定第一相机41和第二相机42发生位置偏移时，再进行第一距离d1和第一距离预设值d1_ref以及第二距离d2和第二距离预设值d2_ref的比较，从而更准确地获知哪个相机发生位置偏移。当确定第一相机41和第二相机42未发生位置偏移时，则无需进行第一距离d1和第一距离预设值d1_ref以及第二距离d2和第二距离预设值d2_ref的比较，由此，可以提高偏移判定效率。
根据本申请的一些实施例，偏移检测方法200的电极组件偏移判定步骤包括：在第一图像T1中获取第三距离d3，第三距离d3为第三基准点A3到第一极片1的边界的垂直距离，在第二图像T2中获取第四距离d4，第四距离d4为第四基准点A4到第二极片2的边界的垂直距离，当第一距离d1和第二距离d2之差小于等于第一阈值，且第三距离d3和第四距离d4之差减去第一极片1边界与第二极片2边界的预设距离而取得的差值大于第二阈值时，判定电极组件100发生偏移。
如上所述，在卷绕电极组件过程中较为重要的参数为卷绕后电极组件100在Z轴方向上的对齐度，尤其是第一极片1边界与第二极片边界2之间的垂直距离。在确保第一相机41和第二相机42处于正确位置的前提下(第一距离d1和第二距离d2之差小于等于第一阈值)，仍然利用第一图像T1和第二图像T2，通过第三距离d3和第四距离d4之差即可获得第一极片1边界与第二极片边界2之间的垂直距离，再将所获得的第一极片1边界与第二极片边界2之间的垂直距离与其预设距离比较，就可以精确地判定电极组件100卷绕时的位置是否发生偏移。
值得注意的是，如图6所示，在第一图像T1中，第三基准点A3可以和第一基准点A1重合。在第二图像T2中，第四基准点A4可以和第二基准点A2重合。但第三基准点A3和第四基准点A4不限于此，只要由此得到的第三距离d3和第四距离d4之间的关系确定的即可。
根据本申请的一些实施例，偏移检测方法200的电极组件偏移判定步骤包括：在第一图像T1中获取第三距离d3，第三距离d3为第三基准点A3到第一极片1的边界的垂直距离，在第二图像T2中获取第四距离d4，第四距离d4为第四基准点A4到第二极片2的边界的垂直距离，当第一距离d1和第二距离d2之差小于等于第一阈值，且第三距离d3超出第三距离参考值d3_ref范围时，判定第一极片1发生偏移，当第一距离 d1和第二距离d2之差小于等于第一阈值，且第四距离d4超出第四距离参考值d4_ref范围时，判定第二极片2发生偏移。由此，通过分别将第三距离d3、第四距离d4与预设值d3_ref、d4_ref比较，可以分别判定第一极片1和第二极片2是否发生位置偏移，相比于判定第三距离d3和第四距离d4之间的关系，可以更精确的判定哪个极片发生位置偏移。
也可以，先判定第三距离d3和第四距离d4之间的关系，确定电极组件100在卷绕时是否发生位置偏移。当确定电极组件100在卷绕时发生位置偏移时，再进行第三距离d3和第三距离预设值d3_ref以及第四距离d4和第四距离预设值d4_ref的比较，从而更准确地获知哪个极片发生位置偏移。当确定电极组件100在卷绕时未发生位置偏移时，则无需进行第三距离d3、第四距离d4与预设值d3_ref、d4_ref的比较，由此，可以提高偏移判定效率。
根据本申请的一些实施例，偏移检测方法200的电极组件偏移判定步骤包括：在第一图像T1中获取第三距离d3，第三距离d3为第三基准点A3到第一极片1的边界的垂直距离，在第二图像T2中获取第四距离d4，第四距离d4为第四基准点A4到第二极片2的边界的垂直距离，当第三距离d3和第四距离d4之差减去所述第一极片边界与所述第二极片边界的预设距离之后，再减去第一距离d1和第二距离d2之差而取得的差值大于第三阈值时，判定电极组件发生偏移。
如图7所示，当第一相机41和/或第二相机42的位置发生微小偏移，但d1-d2小于第一阈值，此时，通过第三距离d3和第四距离d4之差得到的第一极片1的边界和第二极片2的边界间的偏移量包括两部分，即，由第一相机41和第二相机42所引起的第一、第二图像T1、T2中的坐标系偏差d1-d2、以及实际第一极片1的边界和第二极片2的边界间的偏移量。因此，实际第一极片1的边界和第二极片2的边界间的偏移量等于第三距离d3和第四距离d4之差减去第一距离d1和第二距离d2之差。由此，可以排除第一相机41和第二相机42的位置偏差带来影响，而更精确地判定电极组件100的位置偏移。
在图7中，示出了第一基准点A1和第三基准点A3重合并且第二基准点A2和第四基准点A4重合的情况。应当理解的是，本申请不限于此，可以任意选取第一～第四基准点A1～A4，只要满足：由第三基准点A3和 第四基准点A4获得d3和d4具有确定的对应关系，由第一基准点A1和第二基准点A2获得d1和d2具有确定的对应关系，并且d1-d2为由第一相机41和第二相机42所引起的第一、第二图像T1、T2中的坐标系偏差即可。
根据本申请的一些实施例，第二相机42使用红外光源穿透一层隔离膜拍摄其后的第二极片2。如上所述(参照图6)，在第二图像T2中，第二极片2位于第二隔离膜32的下方。由此，采用可穿透第二隔离膜32的红外线相机，可以确保在第二图像T2中识别第二极片2，进而获得第四距离d4，以和第三距离d3进行比较，判定电极组件100在卷绕时是否发生位置偏移。
根据本申请的一些实施例，隔离膜3包括第一隔离膜31和第二隔离膜32，第一图像T1包括第一极片1和第一隔离膜31，第二图像T2包括第二极片2和第二隔离膜32，特定位置6为第二隔离膜32露出于第一隔离膜31的边界或第一隔离膜31露出于第二隔离膜32的边界。
图8示出第一隔离膜31从第二隔离膜32露出的例子。从图8中可以看出，第一图像T1中，第一隔离膜31在第二隔离膜32的上方，因此可以识别第一隔离膜31的边界，并将其作为特定位置6。在第二图像T2中，第一隔离膜31虽然位于第二隔离膜32的下方，但是由于第一隔离膜31从第二隔离膜32露出，因此也可以在第二图像T2中识别第一隔离膜31的边界，并将其作为特定位置6。由此，第一图像T1中的特定位置6和第二图像T2中的特定位置6相对应，均为第一隔离膜31的边界。当第二隔离膜32的边界从第二隔离膜边界露出时亦然。由此，即使第一隔离膜31和/或第二隔离膜32发生位置偏移，也可以确保第一图像T1中的特定位置6和第二图像T2中的特定位置6相对应，且对应于电极组件100的同一位置。
根据本申请的一些实施例，获取第二图像T2的时间晚于获取第一图像T1的时间，该时间差根据第一相机41和第二相机42的拍摄位置以及电极组件100的卷绕速度来设定。由此，通过调整该时间差，能够使拍摄的第一图像T1和第二图像T2显示卷绕后相同位置的第一极片1和第二极片2，从而能够对相同位置的第一极片1和第二极片2进行位置偏移检测，能够使检测结果更精确。
根据本申请的一些实施例，提供一种偏移检测装置，用于检测电极组件卷绕时的位置偏移，电极组件100包括第一极片1、第二极片2和隔离膜3，偏移检测装置包括：第一相机41和第二相机42，分别获取第一图像T1和第二图像T2，第一图像T1包括电极组件100在卷绕过程中第一极片1的图像，第二图像T2包括电极组件100在卷绕过程中第二极片2的图像；以及偏移判定单元，根据第一图像T1中的基准点和第二图像T2中的基准点到特定位置6的距离，判定第一相机41和第二相机42是否发生偏移，当判定第一相机41和第二相机42未发生偏移时，根据第一图像T1中的基准点到第一极片1的边界的垂直距离和第二图像T2中的基准点到第二极片2的边界的垂直距离，判定电极组件100是否发生偏移。
根据本申请的一些实施例，参见图1至图6，本申请提供了一种偏移检测方法200，包括以下步骤：
通过第一相机41和第二相机42获取第一图像T1和第二图像T2，第一图像T1包括电极组件100在卷绕过程中第一极片1的图像，第二图像T2包括电极组件100在卷绕过程中第二极片2的图像；
将第一图像T1中的第一基准点A1设为第一图像T1的Z轴方向上的像素中值点(例如，对于在Z轴方向上具有4096个像素的线扫相机而言，像素中值点为第2096像素点)，将第二图像T2中的第二基准点A2设为第二图像T2的Z轴方向上的像素中值点，并且将特定位置6设为隔离膜3的边界。由此，获得第一图像T1中的第一基准点A1到隔离膜2的边界的第一距离d1和第二图像T2中的第二基准点A2到特定位置6的第二距离d2。通过比较第一距离d1和第二距离d2与第一阈值，来判定所述第一相机41和/或所述第二相机42是否发生偏移。当第一相机41和或第二相机42发生偏移时，进一步比较d1和第一距离预设值d1_ref以及d2和第二距离预设值d1_ref，从而更准确的判定第相机41和第二相机42中哪个相机发生偏移。
当判定所述第一相机41和所述第二相机42未发生偏移时，判定电极组件100是否发生偏移。在第一图像T1中，将第三基准点A3设为与第一基准点A1重合，并且在第二图像T2中，将第四基准点A4设为与第二基准点A2重合。由此，获得第一图像T1中的第三基准点A3(第一 基准点A1)到第一极片1的边界的第一距离d3和第二图像T2中的第四基准点A4(第二基准点A2)到第二极片2的边界的第二距离d4。此时，d3-d4-(d1-d2)为实际第一极片1的边界和第二极片2的边界间的偏移量，即，排除了第一相机41和第二相机42的影响的、实际电极组件100的偏移量。据此，可以更精确地判定电极组件100是否发生偏移。
最后，需要说明的是，本申请不限定于上述实施例。上述实施例仅为例示，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施例均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施例施加本领域技术人员能够想到的各种变形、将实施例中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (10)

  1. 一种偏移检测方法，其中，
    用于检测电极组件卷绕时的位置偏移，所述电极组件包括第一极片、第二极片和隔离膜，
    所述偏移检测方法包括：
    通过第一相机和第二相机获取第一图像和第二图像，所述第一图像包括所述电极组件在卷绕过程中第一极片的图像，所述第二图像包括所述电极组件在卷绕过程中第二极片的图像；
    相机偏移判断步骤，根据所述第一图像中的基准点和/或所述第二图像中的基准点到特定位置的距离，判定所述第一相机和/或所述第二相机是否发生偏移，所述特定位置是出现在所述第一图像和第二图像中的相同对象的位置，
    电极组件偏移判定步骤，当判定所述第一相机和所述第二相机未发生偏移时，根据所述第一图像中的基准点到第一极片的边界的垂直距离和所述第二图像中的基准点到第二极片的边界的垂直距离，判定所述电极组件是否发生偏移。
  2. 根据权利要求1所述的偏移检测方法，其中，
    所述相机偏移判断步骤包括：
    根据所述第一图像，获取第一距离，所述第一距离为第一基准点到所述特定位置的距离；
    根据所述第二图像，获取第二距离，所述第二距离为第二基准点到所述特定位置的距离；
    当所述第一距离和所述第二距离之差大于第一阈值时，判定所述第一相机和所述第二相机之间产生相对位移。
  3. 根据权利要求1所述的偏移检测方法，其中，
    所述相机偏移判断步骤包括：
    根据所述第一图像，获取第一距离，所述第一距离为第一基准点到所述特定位置的距离，
    根据所述第二图像，获取第二距离，所述第二距离为第二基准点到 所述特定位置的距离，
    当所述第一距离超出第一距离参考值范围时，判定所述第一相机发生偏移；
    当所述第二距离超出第二距离参考值范围时，判定所述第二相机发生偏移。
  4. 根据权利要求1～3中任一项所述的偏移检测方法，其中，
    所述特定位置为所述隔离膜的边界，或者，所述特定位置为激光照射于所述电极组件的位置，
    其中，所述激光由激光器发出并照射于电池组件，用于在所述第一图像和所述第二图像产生像素边界。
  5. 根据权利要求2所述的偏移检测方法，其中，
    所述电极组件偏移判定步骤包括：
    根据所述第一图像，获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，
    根据所述第二图像，获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，
    当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所述第三距离和所述第四距离之差减去所述第一极片的所述边界与所述第二极片的所述边界的预设距离而取得的差值大于第二阈值时，判定所述电极组件发生偏移。
  6. 根据权利要求2所述的偏移检测方法，其中，
    所述电极组件偏移判定步骤包括：
    根据所述第一图像，获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，
    根据所述第二图像，获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，
    当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所述第三距离超出第三距离参考值范围时，判定所述第一极片发生偏移，
    当所述第一距离和所述第二距离之差小于等于所述第一阈值，且所 述第四距离超出第四距离参考值范围时，判定所述第二极片发生偏移。
  7. 根据权利要求2所述的偏移检测方法，其中，
    所述电极组件偏移判定步骤包括：
    在所述第一图像中获取第三距离，所述第三距离为第三基准点到所述第一极片的边界的垂直距离，在所述第二图像中获取第四距离，所述第四距离为第四基准点到所述第二极片的边界的垂直距离，
    当所述第三距离和所述第四距离之差减去所述第一极片边界与所述第二极片边界的预设距离之后，再减去所述第一距离和所述第二距离之差而取得的差值大于第三阈值时，判定所述电极组件发生偏移。
  8. 根据权利要求1～3中任一项所述的偏移检测方法，其中，
    所述第二相机使用红外光源穿透一层所述隔离膜拍摄其后的所述第二极片。
  9. 根据权利要求1～3中任一项所述的偏移检测方法，其中，
    所述隔离膜包括第一隔离膜和第二隔离膜，
    所述第一图像包括第一极片和第一隔离膜，
    所述第二图像包括第二极片和第二隔离膜，
    所述特定位置为所述第二隔离膜露出于所述第一隔离膜的边界或所述第一隔离膜露出于所述第二隔离膜的边界。
  10. 一种偏移检测装置，其中，
    用于检测电极组件卷绕时的位置偏移，所述电极组件包括第一极片、第二极片和隔离膜，
    所述偏移检测装置包括：
    第一相机和第二相机，分别获取第一图像和第二图像，所述第一图像包括所述电极组件在卷绕过程中第一极片的图像，所述第二图像包括所述电极组件在卷绕过程中第二极片的图像；以及
    偏移判定单元，
    根据所述第一图像中的基准点和所述第二图像中的基准点到特定位置的距离，判定所述第一相机和所述第二相机是否发生偏移，
    当判定所述第一相机和所述第二相机未发生偏移时，根据所述第一图像中的基准点到第一极片的边界的垂直距离和所述第二图像中的基准点到第二极片的边界的垂直距离，判定所述电极组件是否发生偏移。
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