A method for measuring battery edge thickness based on a double-line scanning camera

Abstract

This invention relates to the field of battery testing technology and discloses a method for measuring the edge thickness of a battery seal based on a dual-line scanning camera. The method includes the following steps: the user selects the battery model to be measured and places the battery on a stage. As the stage moves, the line scanning camera is triggered to synchronously scan the edge to be measured, acquiring depth data from the upper and lower cameras. The edge thickness is then calculated using the following algorithm. The proposed battery edge thickness measurement scheme has a simple structure and is easy to operate. Only one system calibration is required to measure various battery models. Furthermore, based on the line scanning camera scanning the battery edge, the measurement results are accurate, reliable, and stable. In addition, the device of this invention has a simple structure and is easy to operate; it is a non-contact measurement, which will not cause deformation or damage to the battery; it has high measurement efficiency, allowing multiple measurement points to be detected simultaneously in one measurement; and the measurement accuracy is repeatable and reliable.

Description

Technical Field

[0001] This invention relates to the field of battery testing technology, specifically a method for measuring the thickness of battery sealing edges based on a dual-line scanning camera. Background Technology

[0002] Soft-pack batteries typically have three sealing edges, and their sealing effect directly affects the battery's safety and lifespan. Over-sealing and under-sealing can easily lead to poor quality. Therefore, ensuring the sealing and welding quality of soft-pack batteries is one of the prerequisites for producing high-quality soft-pack batteries.

[0003] Currently, most measurements of the edge sealing thickness of pouch batteries are done manually, using a micrometer. This method is a contact measurement, which can only measure a single point at a time. Furthermore, the results are greatly affected by human error, making it impossible to accurately measure the thickness at a specific point and potentially causing deformation of the battery edge sealing. A new 2D non-contact method for measuring edge sealing thickness has emerged in the market. This method is less efficient, requires complex equipment, and is more expensive.

[0004] Therefore, this invention provides a method for measuring the thickness of battery sealing edges based on a dual-line scanning camera. This method can solve the problem that manual measurement can only measure one point at a time and the measurement results are inaccurate. At the same time, it can solve the problems of low measurement efficiency, complex equipment structure, difficult operation, and high measurement cost of non-contact measurement of sealing edge thickness based on 2D method. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for measuring battery edge thickness based on a dual-line scanning camera, thus solving the problems mentioned in the background technology.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for measuring the edge thickness of a battery based on a dual-line scanning camera, comprising the following steps: the user selects the battery model to be measured and places the battery on the stage. As the stage moves, the line scanning camera is triggered to synchronously scan the edge to be measured, obtain the depth data of the upper and lower cameras, and obtain the edge thickness through the following algorithm.

[0009] After the camera positions are fixed, the distance between the upper and lower cameras is determined. If the thickness of the sealing edge to be measured is h, then...

[0010] (1)

[0011] in, , Let h represent the distances from the surface of the object to be measured to the upper and lower cameras, respectively. C is the distance constant between the upper and lower cameras. If h is known, the distance constant can be calibrated.

[0012] To calibrate the distance constant C of the measurement system, a calibration block with a known thickness is used. The upper and lower cameras scan synchronously to obtain depth data. The distance constant can be calibrated according to formula (1). The battery sealing thickness can then be expressed as:

[0013] (2)

[0014] Formula (1) implicitly requires that the stage and the camera be perpendicular to each other and that the upper and lower cameras be aligned. In reality, the camera and the stage are not completely perpendicular. There is a three-dimensional rotational relationship between them. Ideally, the distance from any point on the surface of the calibration block to the camera is equal. In reality, the distance from the calibration block to the camera is not exactly the same. In reality, the axis of motion of the stage cannot be completely parallel to the camera, and there are slight protrusions at different positions. The distance from the calibration block to the camera is linear, indicating that there is a certain angle between the stage and the camera.

[0015] Calculate the rotation angles of the calibration block relative to the camera's x-axis and y-axis respectively, and then the 3D rotation matrix can be expressed as:

[0016] (3)

[0017] (4)

[0018] Use formula (5) to perform planar correction on the inclined calibration surface:

[0019] (5)

[0020] After leveling the image, in order to measure the edge sealing thickness, it is also necessary to calibrate the rotation angles of the top and bottom edges about the z-axis to ensure that the images from the top and bottom cameras are aligned; find the horizontal and vertical edges of the calibration block in the images from the top and bottom cameras respectively, and calculate the corner points; calculate the angle of the horizontal edge in the image:

[0021] (6)

[0022] Where k is the slope of the line, the difference in rotation angle between the upper and lower cameras about the z-axis is:

[0023] (7)

[0024] in, , These represent the angles of the horizontal edge of the calibration block in the lower and upper cameras, respectively.

[0025] After the calibration block is leveled, ideally the height distribution on the surface of the calibration block should be horizontal. However, in reality, the motion axis is not strictly parallel to the camera, and the distance from the camera to different positions is different. In order to further improve the measurement accuracy, partition calibration is adopted, that is, the calibration block is gridded, and the local compensation value in each grid is calculated. In actual measurement, the thickness of each pixel is calculated based on the bilinear interpolation method of table lookup.

[0026] After the system is calibrated, the calibration parameters are written into the configuration file so that calibration is not performed for each measurement. During actual measurement, the depth maps of the upper and lower cameras are aligned according to formulas (5) to (7). The battery sealing edge position is located based on threshold binarization technology. The horizontal and vertical edges of the battery sealing edge are found using straight line search technology. Based on the horizontal and vertical edges of the battery sealing edge, N measurement points are selected at equal intervals. The battery sealing edge thickness is evaluated using formula (2).

[0027] Preferably, before measuring the edge thickness of the battery, a normal range of edge thickness for each battery model is pre-set and set as a threshold range. When measuring the edge thickness of the battery, N measurement points are selected at equal intervals, and the battery edge thickness is evaluated using formula (2). After obtaining the data of N measurement points, the N data are analyzed using an algorithm to obtain the optimal parameters. Then, the corresponding threshold range is matched according to the model of the battery being measured, and the obtained optimal parameters are compared with the threshold position to determine whether the optimal parameters fall within the threshold range. If they are within the threshold range, the edge of the battery being measured is judged to be normal; otherwise, the edge of the battery being measured is judged to be abnormal.

[0028] In the testing line, if the sealing edge of the battery under test is found to be abnormal, the battery with abnormal sealing edge is removed from the testing line by the rejection mechanism, and the model of the battery is recorded. At the same time, the feedback is sent to the control terminal so that the managers can understand the defect rate of each model of battery on the testing line.

[0029] Preferably, after obtaining the data from N measurement points on the battery under test, the data from each of the N measurement points is compared with the corresponding threshold range. If it is found that the data from one or more measurement points has a large degree of dispersion from the threshold range, no further operation is performed, and the data from the measurement points with a large degree of dispersion and their locations are recorded.

[0030] This allows managers to identify problems with the battery sealing process or equipment by using the recorded signals of the tested battery and the measurement point data and locations, which have a large degree of dispersion.

[0031] (III) Beneficial Effects

[0032] This invention provides a method for measuring the thickness of battery sealing edges based on a dual-line scanning camera, which has the following advantages:

[0033] The proposed method for measuring battery seal thickness is simple in structure and easy to operate. It requires only one system calibration to measure various battery models. Furthermore, based on a line-scan camera scanning the battery seal, the measurement results are accurate, reliable, and stable. In addition, the device is simple in structure and easy to operate; the non-contact measurement will not cause deformation or damage to the battery; it has high measurement efficiency, allowing multiple measurement points to be detected simultaneously in a single measurement; and the measurement accuracy is repeatable and reliable.

[0034] When measuring each type of battery, the optimal parameter data of N measurement points for each tested battery is obtained. Then, the obtained optimal parameter data is compared with its corresponding threshold range. If the optimal parameter data falls within its corresponding threshold range, the battery sealing is judged to be normal; otherwise, the battery sealing is judged to be abnormal. During the measurement of battery sealing thickness, it is possible to simultaneously determine whether the sealing of different battery types is normal. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the measurement process;

[0036] Figure 2 This is a schematic diagram illustrating the measurement principle.

[0037] Figure 3 This is a schematic diagram illustrating the depth trend of the calibration block.

[0038] Figure 4 This is a schematic diagram of the height distribution on the surface of the calibration block after leveling. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, the present invention provides a technical solution: a method for measuring the edge thickness of a battery based on a dual-line scanning camera, comprising the following steps: the user selects the battery model to be measured and places the battery on the stage. As the stage moves, the line scanning camera is triggered to synchronously scan the edge to be measured, obtain the depth data of the upper and lower cameras, and obtain the edge thickness through the following algorithm.

[0041] like Figure 2 As shown, after the camera position is fixed, the distance between the upper and lower cameras is determined. If the thickness of the sealing edge to be measured is h, then...

[0042] (1)

[0043] in, , Let h represent the distances from the surface of the object to be measured to the upper and lower cameras, respectively. C is the distance constant between the upper and lower cameras. If h is known, the distance constant can be calibrated.

[0044] To calibrate the distance constant C of the measurement system, a calibration block with a known thickness is used. The upper and lower cameras scan synchronously to obtain depth data. The distance constant can be calibrated according to formula (1). The battery sealing thickness can then be expressed as:

[0045] (2)

[0046] Formula (1) implicitly requires that the stage and the camera be perpendicular to each other and that the upper and lower cameras be aligned. In reality, the camera and the stage are not perfectly perpendicular; there is a three-dimensional rotational relationship between them. Ideally, the distance from any point on the surface of the calibration block to the camera is equal. However, in reality, the distance from the calibration block to the camera is not exactly the same. In fact, the axis of motion of the stage cannot be completely parallel to the camera, and there are slight protrusions at different positions, such as... Figure 3 As shown, the distance from the calibration block to the camera is linear, indicating that there is a certain angle between the stage and the camera.

[0047] Calculate the rotation angles of the calibration block relative to the camera's x-axis and y-axis respectively, and then the 3D rotation matrix can be expressed as:

[0048] (3)

[0049] (4)

[0050] Use formula (5) to perform planar correction on the inclined calibration surface:

[0051] (5)

[0052] After leveling the image, in order to measure the edge sealing thickness, it is also necessary to calibrate the rotation angles of the top and bottom edges about the z-axis to ensure that the images from the top and bottom cameras are aligned; find the horizontal and vertical edges of the calibration block in the images from the top and bottom cameras respectively, and calculate the corner points; calculate the angle of the horizontal edge in the image:

[0053] (6)

[0054] Where k is the slope of the line, the difference in rotation angle between the upper and lower cameras about the z-axis is:

[0055] (7)

[0056] in, , These represent the angles of the horizontal edge of the calibration block in the lower and upper cameras, respectively.

[0057] After the calibration block is leveled, the height distribution on the surface of the calibration block is as follows: Figure 4 As shown, ideally, the height distribution on the calibration block surface should be horizontal, but... Figure 4 This indicates that the motion axis is not strictly parallel to the camera, and the distance from the camera to different positions is different. In order to further improve the measurement accuracy, this invention proposes partitioned calibration, that is, the calibration block is gridded, and the local compensation value in each grid is calculated. In actual measurement, the thickness of each pixel is calculated based on the bilinear interpolation method of table lookup.

[0058] After the system is calibrated, the calibration parameters are written into the configuration file so that calibration is not performed for each measurement. During actual measurement, the depth maps of the upper and lower cameras are aligned according to formulas (5) to (7). The battery sealing edge position is located based on threshold binarization technology. The horizontal and vertical edges of the battery sealing edge are found using straight line search technology. Based on the horizontal and vertical edges of the battery sealing edge, N measurement points are selected at equal intervals. The battery sealing edge thickness is evaluated using formula (2).

[0059] Before measuring the edge thickness of the battery, the normal range of edge thickness for each battery model is pre-set and set as the threshold range. When measuring the edge thickness of the battery, N measurement points are selected at equal intervals. The battery edge thickness is evaluated using formula (2). After obtaining the data of N measurement points, the optimal parameters are obtained from the N data using the analysis algorithm. Then, the corresponding threshold range is matched according to the model of the battery being measured, and the obtained optimal parameters are compared with the threshold position to determine whether the optimal parameters fall within the threshold range. If they are within the threshold range, the edge of the battery being measured is judged to be normal. Otherwise, the edge of the battery being measured is judged to be abnormal.

[0060] After obtaining the data from N measurement points on the battery under test, the data from each of the N measurement points will be compared with the corresponding threshold range. If it is found that the data from one or more measurement points has too large a dispersion from the threshold range, no further operation will be performed, and the data of the measurement points with too large a dispersion and their locations will be recorded.

[0061] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of measuring a cell edge thickness based on a dual-line scanning camera, the method comprising: Includes the following steps: The user selects the battery model to be tested and places the battery on the stage. As the stage moves, the line scan camera is triggered to scan the edge to be tested synchronously, obtain the depth data of the upper and lower cameras, and the background algorithm calculates the edge thickness. The specific settings of the background algorithm are as follows: After the camera position is fixed, the distance between the upper and lower cameras is determined. If the thickness of the sealing edge to be measured is h, then... (1)； wherein, , respectively represent the distance from the surface of the object to be measured to the upper and lower cameras, C is a distance constant between the upper and lower cameras, and if h is known, the distance constant can be calibrated. To calibrate the distance constant C of the measurement system, a calibration block with a known thickness is used. The upper and lower cameras scan synchronously to obtain depth data. The distance constant can be calibrated according to formula (1). The battery sealing thickness can then be expressed as: (2)； Formula (1) implicitly requires that the stage and the camera be perpendicular to each other and that the upper and lower cameras be aligned. In reality, the camera and the stage are not completely perpendicular. There is a three-dimensional rotational relationship between them. Ideally, the distance from any point on the surface of the calibration block to the camera is equal. In reality, the distance from the calibration block to the camera is not exactly the same. In reality, the axis of motion of the stage cannot be completely parallel to the camera, and there are slight protrusions at different positions. The distance from the calibration block to the camera is linear, indicating that there is a certain angle between the stage and the camera. Calculate the rotation angles of the calibration block relative to the camera's x-axis and y-axis respectively, and then the 3D rotation matrix can be expressed as: (3)； (4)； Use formula (5) to perform planar correction on the inclined calibration surface: (5)； After leveling the image, in order to measure the edge sealing thickness, it is also necessary to calibrate the rotation angles of the top and bottom edges about the z-axis to ensure that the images from the top and bottom cameras are aligned; find the horizontal and vertical edges of the calibration block in the images from the top and bottom cameras respectively, and calculate the corner points; calculate the angle of the horizontal edge in the image: (6)； Where k is the slope of the line, the difference in rotation angle between the upper and lower cameras about the z-axis is: (7)； wherein, , respectively denote the angle of the calibrated block horizontal edge in the lower, upper camera. After the calibration block is leveled, ideally the height distribution on the surface of the calibration block should be horizontal. However, in reality, the motion axis is not strictly parallel to the camera, and the distance from the camera to different positions is different. In order to further improve the measurement accuracy, partition calibration is adopted, that is, the calibration block is gridded, and the local compensation value in each grid is calculated. In actual measurement, the thickness of each pixel is calculated based on the bilinear interpolation method of table lookup. After the system is calibrated, the calibration parameters are written into the configuration file so that calibration is not performed for each measurement. During actual measurement, the depth maps of the upper and lower cameras are aligned according to formulas (5) to (7). The battery sealing edge position is located based on threshold binarization technology. The horizontal and vertical edges of the battery sealing edge are found using straight line search technology. Based on the horizontal and vertical edges of the battery sealing edge, N measurement points are selected at equal intervals. The battery sealing edge thickness is evaluated using formula (2).

2. The method of claim 1, wherein: Before measuring the edge thickness of the battery, the normal range of edge thickness for each battery model is pre-set and set as the threshold range. When measuring the edge thickness of the battery, N measurement points are selected at equal intervals. The battery edge thickness is evaluated using formula (2). After obtaining the data of N measurement points, the optimal parameters are obtained from the N data using the analysis algorithm. Then, the corresponding threshold range is matched according to the model of the battery being measured, and the obtained optimal parameters are compared with the threshold position to determine whether the optimal parameters fall within the threshold range. If they are within the threshold range, the edge of the battery being measured is judged to be normal. Otherwise, the edge of the battery being measured is judged to be abnormal.

3. The method of claim 2, wherein: After obtaining the data from N measurement points on the battery under test, the data from each of the N measurement points will be compared with the corresponding threshold range. If it is found that the data from one or more measurement points has too large a dispersion from the threshold range, no further operation will be performed, and the data of the measurement points with too large a dispersion and their locations will be recorded.

Images