New energy lithium battery welding height measurement method and measurement system

Abstract

The present disclosure provides a new energy lithium battery welding height measurement method and system, which comprises: using the new energy lithium battery welding height measurement system to scan the lithium battery pole piece with a line structured light, obtaining a light bar image; grayscale the light bar image to obtain a grayscale image; bilateral filter the grayscale image to obtain a filtered image; threshold segmentation and extract the region of interest based on the maximum inter-class variance method to obtain a target image; extract the sub-pixel center of the target image based on the line center extraction algorithm to obtain the sub-pixel coordinates of the light bar center line; based on the predetermined relationship and the sub-pixel coordinates, the height of the lithium battery pole piece welding corresponding to the sub-pixel coordinates is obtained.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of computer vision and the technical field of precision engineering measurement, and more particularly, to a measurement method and system for the height of a welding mark of a new energy lithium battery. BACKGROUND

[0002] High-precision measurement technology has a wide range of needs in advanced manufacturing and cutting-edge scientific research. With the progress of science and technology and industrial manufacturing, especially the booming development of new energy vehicles, integrated circuits and other industries, the detection accuracy of key geometric parameters such as size and topography of key components in related fields is increasingly demanding, and higher demands are placed on high-precision detection technology.

[0003] With the rapid development of the new energy vehicle industry, the demand for new energy lithium batteries has grown significantly. Lithium batteries are mainly composed of positive and negative electrode sheets, separators, electrolytes and the like, among which the positive and negative electrode sheets realize the charging and discharging function of lithium batteries and are the core components of lithium batteries. The welding process of the electrode sheet is a key part of the lithium battery production process chain. In the welding process of new energy lithium batteries, defects such as welding surface protrusions inevitably occur, which can affect the quality and service life of the battery. When the welding mark height of the lithium battery electrode sheet is inconsistent, it can cause the welding mark to break through the medium layer, leading to battery failure and causing major safety hazards. Therefore, it is necessary to measure the welding mark height of the lithium battery electrode sheet to monitor and detect the welding quality and ensure the quality of the welding process.

[0004] At present, the degree of automation of lithium battery production workshops is not high, and the detection of lithium batteries after welding in China is mainly manual detection, which generally uses a micrometer to measure the welding mark height. The measurement mode is contact measurement, which can affect the actual height of the welding point during the measurement process. Manual detection is heavily dependent on the technical level and experience of the detection personnel, is affected by human subjective factors, has great uncertainty, poor measurement repeatability, and is difficult to ensure the quality and efficiency of detection. SUMMARY

[0005] Therefore, the present disclosure provides a measurement method and system for the height of a welding mark of a new energy lithium battery.

[0006] According to one aspect of the present disclosure, a new energy lithium battery welding height measurement method is provided, comprising: performing line structured light scanning on a lithium battery pole piece by using a new energy lithium battery welding height measurement system to obtain a light strip image, wherein the spatial positions of each device included in the new energy lithium battery welding height measurement system are determined based on system parameters of the new energy lithium battery welding height measurement system, the system parameters of the new energy lithium battery welding height measurement system are calculated by using a Monte Carlo optimization algorithm with system sensitivity as an objective function, the system sensitivity represents the movement distance of an image point corresponding to an object point on the lithium battery pole piece from a reference point when the object point moves a unit distance in the depth direction; performing grayscale processing on the light strip image to obtain a grayscale image; performing bilateral filtering on the grayscale image to obtain a filtered image; performing threshold segmentation on the filtered image based on the maximum inter-class variance method and extracting a region of interest to obtain a target image, wherein the target image includes a lithium battery pole piece welding; performing sub-pixel center extraction on the target image based on a line center extraction algorithm to obtain sub-pixel coordinates of a light strip center line; and based on a predetermined relationship and the sub-pixel coordinates, obtaining the height of the lithium battery pole piece welding corresponding to the sub-pixel coordinates.

[0007] According to an embodiment of the present disclosure, the system parameters of the new energy lithium battery welding height measurement system are obtained according to the following operations: determining a target function according to a working angle, an object distance and a lens focal length, wherein the working angle represents an included angle between an optical axis of a laser in the new energy lithium battery welding height measurement system and an optical axis of a camera in the new energy lithium battery welding height measurement system, the object distance represents a distance between a center of a lens of the camera and a point on the lithium battery pole piece where the optical axis of the laser is projected, and the lens focal length represents a focal length of the lens of the camera; determining constraint functions corresponding to the working angle, an image distance and a height measurement range respectively according to the working angle, the object distance and the lens focal length; generating M groups of random numbers corresponding to the working angle, the object distance and the lens focal length respectively according to a Monte Carlo optimization algorithm, wherein M is a positive integer; and determining the system parameters according to the M groups of random numbers, the target function and the constraint functions.

[0008] According to an embodiment of the present disclosure, each group of random numbers includes a working angle random number corresponding to the working angle, an object distance random number corresponding to the object distance, and a lens focal length random number corresponding to the lens focal length, and the determination of the system parameters according to the M groups of random numbers, the target function, and the constraint function includes: performing the following operations in a loop until m is equal to M to obtain an updated maximum system sensitivity value, a working angle, an object distance, and a lens focal length, where m is a positive integer less than or equal to M; in a case where the mth working angle random number, the mth object distance random number, and the mth lens focal length random number satisfy the constraint function, an mth system sensitivity value is calculated according to the mth working angle random number, the mth object distance random value, the mth receiving lens focal length random value, and the target function; in a case where the mth system sensitivity value is greater than the maximum system sensitivity value, the maximum system sensitivity value is updated using the mth system sensitivity value, and the working angle, the object distance, and the lens focal length are updated using the mth working angle random number, the mth object distance random number, and the mth lens focal length random number, respectively, where the initial value of the maximum system sensitivity value is a predetermined value; and the system parameters are determined according to the updated maximum system sensitivity value, working angle, object distance, and lens focal length.

[0009] According to an embodiment of the present disclosure, the threshold segmentation and the extraction of the region of interest of the filtered image based on the maximum inter-class variance method to obtain the target image include: performing inter-class variance calculation and intra-class variance calculation on the filtered image by using the maximum inter-class variance method to obtain a target threshold; performing binaryzation on the target image according to the target threshold to obtain a segmented image; and performing region of interest extraction on the segmented image to obtain the target image.

[0010] According to an embodiment of the present disclosure, the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinate is obtained based on the predetermined relationship and the sub-pixel coordinate, including: calculating a target movement distance according to the sub-pixel coordinate and a reference coordinate of a reference point corresponding to the sub-pixel coordinate; and calculating the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinate according to the target movement distance and the predetermined relationship.

[0011] According to an embodiment of the present disclosure, the line structure light projected by the measurement system for the welding mark height of the new energy lithium battery on the lithium battery pole piece is blue line structure light or red line structure light.

[0012] According to another aspect of the present disclosure, a new energy lithium battery welding height measurement system is provided for implementing the new energy lithium battery welding height measurement method described above, comprising: a laser for projecting line structured light on a lithium battery pole piece; a camera for collecting the lithium battery pole piece with the line structured light projected thereon to obtain a light bar image, wherein the spatial positions of the laser, the lens of the camera, and the photosensitive detector of the camera are determined by system parameters of the new energy lithium battery welding height measurement system, the system parameters of the new energy lithium battery welding height measurement system are calculated by using a Monte Carlo optimization algorithm with system sensitivity as an objective function, and the system sensitivity represents the movement distance of an image point corresponding to an object point on the lithium battery pole piece from a reference point when the object point moves a unit distance in the depth direction; a processor for grayscale processing of the light bar image to obtain a grayscale image, bilateral filtering of the grayscale image to obtain a filtered image, threshold segmentation of the filtered image based on the maximum inter-class variance method to extract a region of interest and obtain a target image, wherein the target image includes a lithium battery pole piece welding; sub-pixel center extraction of the target image based on a line center extraction algorithm to obtain sub-pixel coordinates of a light bar center line; and obtaining the height of the lithium battery pole piece welding corresponding to the sub-pixel coordinates based on a predetermined relationship and the sub-pixel coordinates.

[0013] According to an embodiment of the present disclosure, the lens of the camera is an aspherical lens.

[0014] According to an embodiment of the present disclosure, the new energy lithium battery welding height measurement system further comprises a moving platform for placing the lithium battery pole piece and moving the lithium battery pole piece in a direction perpendicular to the light bar on the lithium battery pole piece based on a predetermined speed.

[0015] According to an embodiment of the present disclosure, the new energy lithium battery welding height measurement system further comprises a narrowband filter for filtering the line structured light reflected by the lithium battery pole piece before the line structured light passes through the lens of the camera.

[0016] According to the embodiment of the present disclosure, since the spatial positions of the devices included in the new energy lithium battery welding height-oriented measurement system are determined based on the system parameters of the new energy lithium battery welding height-oriented measurement system, and the system parameters of the new energy lithium battery welding height-oriented measurement system are calculated by using the Monte Carlo optimization algorithm with the system sensitivity as the objective function, the system parameters are optimized based on the intelligent optimization algorithm, and the system building efficiency is improved. By using the new energy lithium battery welding height-oriented measurement system to scan the lithium battery pole piece with a line structured light, a light bar image is obtained, the light bar image is grayed to obtain a gray image, the gray image is bilateral filtered to obtain a filtered image, the filtered image is threshold segmented based on the maximum interclass variance method and the region of interest is extracted to obtain a target image, the target image is sub-pixel center extracted based on the line center extraction algorithm to obtain the sub-pixel coordinates of the light bar center line. The technical means realizes the characteristics of the new energy lithium battery pole piece welding high reflection, adopts the bilateral filtering combined with the maximum interclass variance method to denoise and segment the image, and then adopts the line center extraction algorithm to extract the light bar center, and realizes the sub-pixel level image processing. Then, based on the predetermined relationship and the sub-pixel coordinates, the height of the lithium battery pole piece welding corresponding to the sub-pixel coordinates is obtained, the non-contact automatic measurement of the lithium battery pole piece welding height is realized, the damage to the lithium battery pole piece welding caused by the contact measurement is avoided, the manual measurement error is reduced, and the measurement accuracy and efficiency are improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure, taken in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A flowchart of a new energy lithium battery welding height-oriented measurement method according to an embodiment of the present disclosure is schematically shown;

[0019] Figure 2 A schematic diagram of a new energy lithium battery welding height-oriented measurement system according to an embodiment of the present disclosure is schematically shown;

[0020] Figure 3 A schematic diagram of laser triangulation based on a new energy lithium battery welding height-oriented measurement system according to an embodiment of the present disclosure is schematically shown; and

[0021] Figure 4 A flowchart of optimizing system parameters according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0022] Embodiments of the present disclosure will be described below with reference to the drawings. However, it should be understood that these descriptions are merely exemplary, and are not intended to limit the scope of the present disclosure. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it will be apparent to those skilled in the art that the embodiments can be practiced without these specific details. In addition, in the following description, descriptions of well-known structures and techniques have been omitted to avoid unnecessarily obscuring the concepts of the present disclosure.

[0023] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting of the present disclosure. As used herein, the term "includes" and tautological expressions thereof, such as "including," "includes," "include," "contains," "containing," and so on, mean the presence of stated features, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0024] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the specification, and should not be interpreted in an idealized or overly formal manner.

[0025] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should generally be interpreted to include at least one of each item enumerated, in addition to combinations of these items (e.g., "a system having at least one of A, B, and C" should include, but not be limited to, a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C, etc.).

[0026] In recent years, with the development of digital image processing technology, photoelectric precision detection technology based on line structured light is widely used in the field of precision engineering measurement. However, photoelectric precision detection technology based on line structured light still faces some challenges in the detection of new energy lithium battery welding height, mainly in the selection of system optimal parameters and image processing. The selection of system parameters affects the final measurement accuracy of the system. The determination of the optimal parameters of the traditional line structured light measurement system needs a large number of experiments, which is low in efficiency. And due to the characteristics of high reflectivity of new energy lithium battery welding, the image collected by the measurement system has much noise and is difficult to identify and extract features, resulting in low accuracy of the measurement system.

[0027] In view of this, the embodiments of the present disclosure provide a measurement method and a measurement system for the height of new energy lithium battery welding, which can be applied to the fields of computer vision technology and precision engineering measurement technology.

[0028] Figure 1 A flowchart of a measurement method for the height of new energy lithium battery welding according to an embodiment of the present disclosure is schematically shown.

[0029] As shown in the method for measuring the height of a new energy lithium battery welding mark, the method comprises operations S110-S160. Figure 1

[0030] In operation S110, a line structured light scanning is performed on the lithium battery pole piece by using the measurement system for the height of the new energy lithium battery welding mark to obtain a light strip image. The spatial positions of the devices included in the measurement system for the height of the new energy lithium battery welding mark are determined based on system parameters of the measurement system for the height of the new energy lithium battery welding mark. The system parameters of the measurement system for the height of the new energy lithium battery welding mark are calculated by using a Monte Carlo optimization algorithm with the system sensitivity as the objective function. The system sensitivity represents the moving distance of the image point deviating from the reference point when the object point on the lithium battery pole piece moves a unit distance along the depth direction.

[0031] According to the embodiment of the present disclosure, the lithium battery welding mark is included on the lithium battery pole piece.

[0032] According to the embodiment of the present disclosure, the spatial position distribution of the devices included in the measurement system for the height of the new energy lithium battery welding mark satisfies the Scheimpflug principle, which has the physical meaning that the object plane, the image plane and the plane where the lens is located are collinear, so that the lithium battery welding marks of different heights are constantly focused on the camera to obtain a clear image, thereby expanding the imaging depth of field and improving the measurement range.

[0033] In operation S120, the light strip image is grayed to obtain a gray image.

[0034] For example, the light strip image collected by the board-level camera can be read by the upper computer, and the gray image can be obtained by graying the light strip image by using the processor in the upper computer.

[0035] After obtaining the gray image, the gray image can be preprocessed. The preprocessing may, for example, include image filtering, threshold segmentation and extraction of the region of interest.

[0036] In operation S130, the gray image is subjected to bilateral filtering to obtain a filtered image.

[0037] According to the embodiment of the present disclosure, due to the high reflection characteristics of the lithium battery welding mark, the light strip edge collected by the camera appears to have a halo. When the gray image is subjected to image filtering, the filtering effects of the traditional mean filtering, median filtering, Gaussian filtering and frequency domain filtering methods are all not ideal. The embodiment of the present disclosure selects appropriate spatial standard deviation and intensity standard deviation and adopts a bilateral filter to perform bilateral filtering on the gray image according to the characteristics of the actual light strip image, which can effectively eliminate the halo of the light strip edge.

[0038] ​In operation S140, the filtered image is threshold segmented based on the maximum inter-class variance method, and a region of interest is extracted to obtain a target image.

[0039] According to an embodiment of the present disclosure, when threshold segmenting the filtered image, the maximum inter-class variance method OTSU can be used to segment the filtered image, that is, the OTSU algorithm finds the optimal threshold according to the characteristics of the filtered image, so that the inter-class variance of the light bar main body and the background after threshold segmentation is maximized, thereby realizing the best threshold segmentation of the light bar image and the background. Then, the region of interest is extracted, only the image feature region of interest, that is, the target image, is retained, so as to reduce the image processing region and improve the measurement efficiency. The target image includes the lithium battery tab weld mark.

[0040] According to an embodiment of the present disclosure, after the gray-scale image is preprocessed, most of the noise in the gray-scale image can be filtered out, and the interference of the noise on the light bar center extraction is reduced. At the same time, through the region of interest extraction, the calculation amount during image processing can be greatly reduced, and the speed of subsequent light bar center extraction is improved.

[0041] In operation S150, the target image is sub-pixel center extracted based on a line center extraction algorithm to obtain a sub-pixel coordinate of the light bar center line.

[0042] According to an embodiment of the present disclosure, when the light bar sub-pixel center of the target image is extracted by using the line center extraction algorithm, that is, the Steger algorithm, the normal direction of the light bar center line is solved by the Hessian matrix, and the light bar gray-scale distribution is Taylor expanded in the normal direction, so that the sub-pixel coordinate of the light bar center line can be obtained.

[0043] In operation S160, based on a predetermined relationship and the sub-pixel coordinate, a height of the lithium battery tab weld mark corresponding to the sub-pixel coordinate is obtained.

[0044] According to an embodiment of the present disclosure, the light reflected at different heights of the lithium battery tab weld mark corresponds to different light bar pixel positions in the light bar image, and the height of the new energy lithium battery tab weld mark can be solved by calculating the distance between the sub-pixel coordinates of different light bar center lines and the corresponding reference coordinates and combining the predetermined relationship.

[0045] According to embodiments of this disclosure, before operation S160, a high-precision step calibration block can be used to calibrate the measurement system for soldering height of new energy lithium batteries. System calibration can be, for example, by using the measurement system for soldering height of new energy lithium batteries to measure the high-precision step calibration block, obtaining the actual measured distance of the object point along the depth direction and the distance of the image point from the reference point. The relationship between the actual measured distance of the object point along the depth direction and the distance of the image point from the reference point is expressed as a polynomial. By solving the parameters of the polynomial, the mapping relationship between the actual measured distance of the object point along the depth direction and the distance of the image point from the reference point is obtained, thereby completing the system calibration and obtaining a predetermined relationship.

[0046] According to embodiments of this disclosure, the spatial positions of the components included in the measurement system for the soldering height of new energy lithium batteries are determined based on the system parameters of the measurement system. These system parameters are calculated using a Monte Carlo optimization algorithm with system sensitivity as the objective function. Therefore, the system parameters are optimized using an intelligent optimization algorithm, improving system construction efficiency. The system employs a line structured light scanning method on the lithium battery electrode using the measurement system to obtain a light stripe image. This image is then converted to grayscale to obtain a grayscale image. A bilateral filter is applied to the grayscale image to obtain a filtered image. Threshold segmentation is performed on the filtered image using the maximum inter-class variance method to extract the region of interest, resulting in a target image. Finally, a line center extraction algorithm is used to extract the sub-pixel center of the target image, obtaining the sub-pixel coordinates of the light stripe center line. This method addresses the high reflectivity of the soldering on new energy lithium battery electrode sheets by using bilateral filtering combined with the maximum inter-class variance method for image denoising and segmentation, and then using the line center extraction algorithm to extract the light stripe center, achieving sub-pixel-level image processing. Then, based on the predetermined relationship and subpixel coordinates, the height of the lithium battery electrode solder mark position corresponding to the subpixel coordinates is obtained, realizing non-contact automated measurement of the height of the lithium battery electrode solder mark. This avoids damage to the lithium battery electrode solder mark caused by contact measurement, reduces manual measurement errors, and improves measurement accuracy and efficiency.

[0047] According to embodiments of this disclosure, for Figure 1 Operation S140, which performs threshold segmentation on the filtered image and extracts the region of interest based on the maximum inter-class variance method to obtain the target image, may include the following operations: calculating the inter-class variance and intra-class variance of the filtered image using the maximum inter-class variance method to obtain the target threshold; binarizing the target image according to the target threshold to obtain the segmented image; and extracting the region of interest from the segmented image to obtain the target image.

[0048] For example, a threshold value can be initialized according to the filtered image, pixels are classified into two categories of background and target according to the threshold value, and the intra-class variance and the inter-class variance are calculated. By traversing each threshold value (0~255), the optimal threshold value that makes the inter-class variance maximum is found as the target threshold value

[0049] According to an embodiment of the present disclosure, by using the maximum inter-class variance method to perform inter-class variance calculation and intra-class variance calculation on the filtered image, the target threshold value is obtained; according to the target threshold value, the target image is binarized to obtain a segmentation image; the region of interest of the segmentation image is extracted to obtain the target image, so that compared with directly performing sub-pixel center extraction on the filtered image, the calculation amount during image processing can be greatly reduced, and the speed of subsequent sub-pixel center extraction of the light bar center is improved.

[0050] According to an embodiment of the present disclosure, for the operation S160 in Figure 1 , based on the predetermined relationship and the sub-pixel coordinates, the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinates can include the following operations: calculating a target movement distance according to the sub-pixel coordinates and the reference coordinates of the reference point corresponding to the sub-pixel coordinates; and calculating the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinates according to the target movement distance and the predetermined relationship.

[0051] According to an embodiment of the present disclosure, by calculating a target movement distance according to the sub-pixel coordinates and the reference coordinates of the reference point corresponding to the sub-pixel coordinates; and calculating the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinates according to the target movement distance and the predetermined relationship, the height of the lithium battery pole piece welding mark is automatically calculated based on the target movement distance and the predetermined relationship, which avoids the influence of human error caused by manual detection of the lithium battery pole piece welding mark, and effectively improves the detection quality and detection efficiency.

[0052] Figure 2 A schematic diagram of a new energy lithium battery welding height measurement system according to an embodiment of the present disclosure is shown schematically.

[0053] As shown in Figure 2 , the new energy lithium battery welding height measurement system 200 includes a laser 210, a camera 220, and a processor 230. The new energy lithium battery welding height measurement system 200 can be used to implement the new energy lithium battery welding height measurement method in Figure 1 .

[0054] The laser 210 can be used to project line structured light on the lithium battery pole piece 201.

[0055] Camera 220 can be used to acquire light stripe images of lithium battery electrode 201 through which structured light is projected. The spatial positions of laser 210, the lens of camera 220, and the photosensitive detector of the camera are determined by the system parameters of the measurement system 200 for measuring the soldering height of new energy lithium batteries. The system parameters of the measurement system 200 for measuring the soldering height of new energy lithium batteries are calculated using a Monte Carlo optimization algorithm with system sensitivity as the objective function. System sensitivity characterizes the distance the corresponding image point on the lithium battery electrode 201 moves from the reference point when the object point moves a unit distance along the depth direction.

[0056] For example, the plane in which the line structured light emitted by the laser 210 is located, the plane in which the lens of the camera 220 is located, and the image plane in which the image formed by the photosensitive detector of the camera are collinear, such that the spatial position distribution of the laser 210, the lens of the camera 220, and the photosensitive detector of the camera satisfies the Scheimpflug principle.

[0057] Processor 230 can be used to convert the light stripe image to grayscale to obtain a grayscale image. Bilateral filtering is then applied to the grayscale image to obtain a filtered image. Thresholding segmentation is performed on the filtered image using the Otsu's method to extract the region of interest, resulting in the target image. Sub-pixel center extraction is performed on the target image using a line center extraction algorithm to obtain the sub-pixel coordinates of the light stripe centerline. Based on a predetermined formula and the sub-pixel coordinates, the height of the lithium battery electrode solder joint corresponding to the sub-pixel coordinates is obtained.

[0058] According to embodiments of this disclosure, processor 230 can be used to execute operations S120 to S160, which will not be described in detail here for simplicity.

[0059] For example, processor 230 can be a processor in a host computer.

[0060] The measurement system 200 for measuring the soldering height of new energy lithium batteries may also include a moving platform 240. The moving platform 240 can be used to place the lithium battery electrode 201 and move the lithium battery electrode 201 along a direction perpendicular to the light strip on the lithium battery electrode 201 based on a predetermined speed.

[0061] like Figure 2 As shown, the lithium battery electrode 201 is mounted on the mobile platform 240. When the mobile platform 240 moves at a constant speed based on a predetermined speed, the measurement system 200 for the solder height of new energy lithium batteries can scan the lithium battery electrode 201 to obtain the three-dimensional morphology of the solder on the lithium battery electrode 201 and realize the measurement of the solder height.

[0062] like Figure 2As shown, the process of the new energy lithium battery weld height facing measurement system 200 measuring the lithium battery pole piece can be: the laser 210 emits line structured light to the lithium battery pole piece 201, and the line structured light is diffused or reflected, the reflected light is received by the camera 220, and the light bar image received by the camera 220 is processed by the processor 230, and the measurement result of the weld height of the lithium battery pole piece is obtained by combining the predetermined relationship obtained by system calibration.

[0063] According to the embodiment of the present disclosure, the new energy lithium battery weld height facing measurement system 200 is built based on the laser triangulation principle, and can realize non-contact measurement of the weld height of the new energy lithium battery pole piece.

[0064] Figure 3 The schematic diagram of laser triangulation based on the new energy lithium battery weld height facing measurement system according to the embodiment of the present disclosure is schematically shown.

[0065] In Figure 3 , the camera 220 can include a lens 221 and a photosensitive detector 222. 202 is a reference plane, and 203 is a measured plane.

[0066] When the new energy lithium battery weld height facing measurement system 200 performs laser triangulation, the line structured light emitted by the laser 210 is reflected after being irradiated to the A point on the measured object on the reference plane 202, the reflected light is received by the photosensitive detector 222 after passing through the lens 221, and the image point A' is formed. When the measured object moves along the depth direction and reaches the B point on the measured plane 203, the image point on the photosensitive detector 222 moves correspondingly, and the image point B' is formed. The moving distance x of the image point, that is, the distance between the image point A' and the image point B', combined with the geometric triangular relationship, can calculate the moving distance y of the measured object along the depth direction.

[0067] The line structured light projected by the new energy lithium battery weld height facing measurement system 200 to the lithium battery pole piece 201 can be blue line structured light of 400nm-470nm or red line structured light of 605nm-700nm.

[0068] For example, the line structured light projected by the new energy lithium battery weld height facing measurement system 200 to the lithium battery pole piece 201 can be blue line structured light of 405nm.

[0069] According to the embodiment of the present disclosure, under the same conditions, the beam of blue light is thinner than that of red light, therefore, when the new energy lithium battery weld height facing measurement system 200 performs three-dimensional measurement, the 405nm blue line structured light is projected to the lithium battery pole piece 201, and higher precision measurement can be realized.

[0070] The camera 220 can be a high-resolution CMOS (Complementary Metal Oxide Semiconductor) board-level camera. The photosensitive detector of the camera 220 can be a photosensitive detector in the high-resolution CMOS board-level camera. For example, the size of the photosensitive detector can be 5472x3648 pixels.

[0071] According to an embodiment of the present disclosure, the board-level camera can avoid the problem of CMOS being blocked due to excessive Scheimpflug angle, so that the full-size CMOS can receive reflected light, and the measurement range of the system is improved.

[0072] According to an embodiment of the present disclosure, in actual use, different wavelengths of light sources and different sizes and types of photosensitive detectors can be selected according to the characteristics of the measured object.

[0073] The lens of the camera 220 is an aspherical lens.

[0074] For example, the lens of the camera 220 can use a large-aperture aspherical lens, which can greatly improve the amount of light entering.

[0075] The measurement system 200 for the height of the welding mark of the new energy lithium battery can also include a narrow-band filter. The narrow-band filter can be used to filter the line structured light reflected by the lithium battery pole piece 201 before the line structured light reflected by the lithium battery pole piece 201 passes through the lens of the camera 220.

[0076] According to an embodiment of the present disclosure, placing a narrow-band filter in front of the lens can reduce the interference of ambient light.

[0077] According to an embodiment of the present disclosure, when the measurement system 200 for the height of the welding mark of the new energy lithium battery is built, the positions and angles of the devices included in the measurement system 200 for the height of the welding mark of the new energy lithium battery need to be determined. However, since there is a mathematical relationship between the system parameters, only the working angle a, the object distance a, and the lens focal length f need to be determined to calculate other parameters, and the positions and angles of the devices in the system are determined. To improve the efficiency of determining the system parameters, when determining the system parameters, the present disclosure uses an intelligent optimization algorithm to directly give the optimal system parameters that meet the constraint conditions. Then, according to the optimal system parameter values, the measurement system 200 for the height of the welding mark of the new energy lithium battery is built, and the highest measurement accuracy is achieved under the constraint condition of meeting the measurement range.

[0078] For example, Figure 3As shown, the working angle α represents the angle between the optical axis of the laser 210 in the measurement system 200 for measuring the soldering height of new energy lithium batteries and the optical axis of the camera 220 in the measurement system 200 for measuring the soldering height of new energy lithium batteries. The object distance a represents the distance between the center of the lens 221 of the camera 220 and the point on the lithium battery electrode projected onto the optical axis of the laser 210. The lens focal length f represents the focal length of the lens 221 of the camera 220. The Schahm angle β is the angle between the photodetector 222 and the optical axis of the camera 220.

[0079] According to embodiments of this disclosure, the system parameters of the measurement system 200 for the soldering height of new energy lithium batteries are obtained by the following operations: determining an objective function based on the working angle α, object distance a, and lens focal length f; determining constraint functions corresponding to the working angle α, image distance b, and height measurement range R based on the working angle α, object distance a, and lens focal length f, where the image distance b represents the distance between the center of the lens 221 of the camera 220 and the image point A'; generating M sets of random numbers corresponding to the working angle α, object distance a, and lens focal length f based on the Monte Carlo optimization algorithm, where M is a positive integer; and determining the system parameters based on the M sets of random numbers, the objective function, and the constraint functions.

[0080] Depend on Figure 3 It can be seen that when the measured object moves a distance of y along the depth direction, the corresponding moving distance of the image point on the photodetector is x. According to geometric trigonometric operations, formula (1) can be obtained.

[0081] (1)

[0082] The inverse function of formula (1) can be used to obtain formula (2).

[0083] (2)

[0084] The derivative of formula (2) yields the system sensitivity δ in formula (3).

[0085] (3)

[0086] With the size of the photosensitive detector being (-X,X), substituting it into formula (1) yields the system height measurement range R in formula (4).

[0087] (4)

[0088] According to an embodiment of the present disclosure, the system sensitivity δ reflects a movement distance of an image point from a reference point when an object point moves a unit distance along a depth direction. In order to improve the system measurement accuracy, the system sensitivity δ should be made to have a larger value. Since the system measurement accuracy and the measurement range are in a negative correlation relationship, when the measurement accuracy is improved, the system measurement range also needs to be considered, and the system measurement accuracy is the highest when the measurement range meets the measurement requirement.

[0089] It can be known from the formula (3) and the formula (4) that the parameters a, b, α and β affect the system sensitivity δ and the height measurement range R. According to the formula (5) of the Sham law and the formula (6) of the Gaussian imaging formula, the parameters a, b, α and β and f are in an operation relationship and can be converted with each other. Then, by simplifying, only the parameters a, α and f need to be determined to determine the system sensitivity δ and the system height measurement range R, that is, the objective function and the constraint function corresponding to the height measurement range R can be determined according to the parameters a, α and f.

[0090] (5)

[0091] (6)

[0092] The constraint function corresponding to the working angle α can be 0<α<60°. The constraint function corresponding to the image distance b can be 0<b<200mm. The height measurement range R can be 0<R<4mm.

[0093] According to an embodiment of the present disclosure, each group of random numbers includes a working angle random number corresponding to a working angle, an object distance random number corresponding to an object distance and a lens focal length random number corresponding to a lens focal length. According to the M groups of random numbers, the objective function and the constraint function, the system parameters are determined, including:

[0094] The following operations are performed in a loop until m is equal to M, to obtain an updated maximum system sensitivity value, a working angle, an object distance and a lens focal length, where m is a positive integer less than or equal to M;

[0095] In a case where the mth working angle random number, the mth object distance random number and the mth lens focal length random number satisfy the constraint function, a mth system sensitivity value is calculated according to the mth working angle random number, the mth object distance random value, the mth receiving lens focal length random value and the objective function;

[0096] In a case where the mth system sensitivity value is greater than the maximum system sensitivity value, the maximum system sensitivity value is updated by using the mth system sensitivity value, and the working angle, the object distance and the lens focal length are updated by using the mth working angle random number, the mth object distance random number and the mth lens focal length random number respectively, where an initial value of the maximum system sensitivity value is a predetermined value;

[0097] According to the updated maximum system sensitivity value, the working angle, the object distance and the lens focal length, the system parameters are determined.

[0098] For example, the updated maximum system sensitivity value can be determined as the optimal system sensitivity, the updated working angle can be determined as the optimal working angle, the updated object distance can be determined as the optimal object distance, and the updated lens focal length can be determined as the optimal lens focal length, and then according to the optimal working angle, the optimal object distance and the optimal lens focal length and formula (5) and formula (6), the optimal b and the optimal β are determined, and the optimal system parameters are obtained.

[0099] According to embodiments of the present disclosure, M can be selected according to actual conditions, which is not limited herein. The predetermined value can be selected according to actual conditions, which is not limited herein. For example, M can be 10000, 50000, 100000 or 1000000, and the predetermined value can be -∞ or 0.

[0100] Figure 4 A flowchart for optimizing system parameters according to embodiments of the present disclosure is schematically shown.

[0101] As shown in Figure 4 , the method for optimizing system parameters comprises operations S410-S419.

[0102] In Figure 4 , in operation S410, the method for optimizing system parameters starts.

[0103] In operation S411, a target function corresponding to system sensitivity δ is determined, and constraint functions corresponding to working angle α, image distance b and height measurement range R respectively are determined.

[0104] In operation S412, the mth group of random numbers corresponding to working angle α, object distance a and lens focal length f respectively are generated.

[0105] In operation S413, it is judged whether the mth working angle random number, the mth object distance random number and the mth lens focal length random number satisfy the constraint functions. If yes, operation S414 is executed, and if no, m is added by 1, i.e. m is incremented, so that m=m+1, and then operation S413 is returned to be executed.

[0106] In operation S414, the mth system sensitivity value δ m is calculated according to the mth working angle random number, the mth object distance random value, the mth receiving lens focal length random value and the target function.

[0107] In operation S415, it is judged whether δ m > δ max . Wherein, δ maxThis is the maximum system sensitivity value. If yes, then execute operation S416_2; otherwise, execute operation S416_1.

[0108] In operation S416_1, the output δ m The m-th working angle is a random number, the m-th object distance is a random value, and the m-th lens focal length is a random value.

[0109] In operation S416_2, δ max =δ m α max = Random number of the m-th working angle, a max =The m-th random number of object distance, f max =The random value of the focal length of the m-th lens. Where, α max Let a be the working angle updated in the m-th iteration. max f is the updated object distance in the m-th iteration. max is the updated lens focal length in the m-th iteration.

[0110] In operation S417, determine if m > M. If yes, then execute operation S418; otherwise, return to execute operation S413.

[0111] During operation S418, the output δ max α max a max and f max And according to δ max α max a max and f max Determine the system parameters.

[0112] The method of optimizing system parameters by operating S419 has ended.

[0113] Depend on Figure 4 As can be seen, the embodiments of this disclosure employ an intelligent optimization algorithm, namely the Monte Carlo optimization algorithm, which obtains the optimal system sensitivity value by randomly sampling parameter values ​​and iteratively obtaining the optimal system sensitivity value.

[0114] According to embodiments of this disclosure, in practical use, other similar intelligent optimization algorithms can also be used to optimize system parameters, with the measurement range, system size, etc., as the objective function.

[0115] According to the embodiments of the present disclosure, the present disclosure can quickly and accurately solve the optimal parameters of the system by optimizing the system parameters through an intelligent optimization algorithm, such as a Monte Carlo optimization algorithm. The traditional selection of system parameters needs a large number of experiments to find a set of parameters that meet the requirements, and the process is cumbersome and susceptible to human interference, and is limited by experimental conditions, and it is impossible to experiment on all parameter values. The intelligent optimization algorithm adopted by the present disclosure can quickly find the global optimal solution of the system parameters through the parameter traversal method, avoiding the cumbersome experimental process and improving the efficiency and quality of the selection of system parameters.

[0116] According to the embodiments of the present disclosure, although the present disclosure fixes the lithium battery pole piece on the moving platform that can move at a constant speed, and fixes the measurement system for the welding print height of the new energy lithium battery above the moving platform to realize scanning, in actual use, the lithium battery pole piece can also be fixed, and the measurement system for the welding print height of the new energy lithium battery can be fixed on the moving platform to realize scanning.

[0117] The measurement method and system for the welding print height of the new energy lithium battery provided by the embodiments of the present disclosure improve the automation level of the lithium battery production workshop, avoid the influence of human error caused by manual detection of lithium batteries, and effectively improve the detection quality and detection efficiency.

[0118] The flowcharts and block diagrams in the drawings illustrate the possible implementation architecture, function and operation of the system, method and computer program product according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram can represent a module, a program segment, or a part of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different order from that shown in the drawings. For example, two blocks that are shown in succession can actually be executed substantially in parallel, and sometimes they can be executed in reverse order, depending on the function involved. It should also be noted that each block in the block diagram or flowchart, and the combination of blocks in the block diagram or flowchart, can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions. Those skilled in the art can understand that the features described in various embodiments and / or claims of the present disclosure can be combined and / or integrated in various combinations, even if such combinations or integrations are not explicitly described in the present disclosure. In particular, the features described in various embodiments and / or claims of the present disclosure can be combined and / or integrated in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or integrations fall within the scope of the present disclosure.

[0119] The above describes embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Those skilled in the art can make various substitutions and modifications without departing from the scope of the present disclosure, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A method for measuring the height of a new energy lithium battery welding mark, comprising: scanning a lithium battery pole piece by using a new energy lithium battery welding mark height measurement system to obtain a light strip image, wherein the spatial positions of the devices included in the new energy lithium battery welding mark height measurement system are determined based on system parameters of the new energy lithium battery welding mark height measurement system, the system parameters of the new energy lithium battery welding mark height measurement system are calculated by using a Monte Carlo optimization algorithm with system sensitivity as an objective function, and the system sensitivity represents the movement distance of an image point corresponding to an object point on the lithium battery pole piece from a reference point when the object point moves a unit distance in the depth direction; graying the light strip image to obtain a gray image; performing bilateral filtering on the gray image to obtain a filtered image; performing threshold segmentation on the filtered image based on the maximum inter-class variance method and extracting a region of interest to obtain a target image, wherein the target image includes a lithium battery pole piece welding mark; performing sub-pixel center extraction on the target image based on a line center extraction algorithm to obtain sub-pixel coordinates of a light strip center line; obtaining the height of the lithium battery pole piece welding mark corresponding to the sub-pixel coordinates based on a predetermined relationship and the sub-pixel coordinates.

2. The measurement method according to claim 1, wherein, The system parameters of the new energy lithium battery welding mark height measurement system are obtained according to the following operations: determining an objective function according to a working angle, an object distance, and a lens focal length, wherein the working angle represents the included angle between the optical axis of a laser in the new energy lithium battery welding mark height measurement system and the optical axis of a camera in the new energy lithium battery welding mark height measurement system, the object distance represents the distance between the center of the lens of the camera and the point on the lithium battery pole piece where the optical axis of the laser is projected, and the lens focal length represents the focal length of the lens of the camera; determining constraint functions corresponding to the working angle, an image distance, and a height measurement range, respectively, according to the working angle, the object distance, and the lens focal length; generating M groups of random numbers corresponding to the working angle, the object distance, and the lens focal length, respectively, according to a Monte Carlo optimization algorithm, wherein M is a positive integer; determining the system parameters according to the M groups of random numbers, the objective function, and the constraint functions.

3. The measurement method according to claim 2, wherein, Each group of random numbers includes a working angle random number corresponding to the working angle, an object distance random number corresponding to the object distance, and a lens focal length random number corresponding to the lens focal length, and the determination of the system parameters according to the M groups of random numbers, the objective function, and the constraint functions includes: recursively performing the following operations until m is equal to M to obtain an updated maximum system sensitivity value, a working angle, an object distance, and a lens focal length, wherein m is a positive integer less than or equal to M; in the case where the mth working angle random number, the mth object distance random number, and the mth lens focal length random number satisfy the constraint functions, calculating the mth system sensitivity value according to the mth working angle random number, the mth object distance random value, the mth received lens focal length random value, and the objective function; In a case where the mth system sensitivity value is greater than a maximum system sensitivity value, the maximum system sensitivity value is updated by using the mth system sensitivity value, and the working angle, the object distance and the lens focal length are updated by using an mth working angle random number, an mth object distance random number and an mth lens focal length random number respectively, wherein an initial value of the maximum system sensitivity value is a predetermined value; The system parameters are determined according to the updated maximum system sensitivity value, working angle, object distance and lens focal length.

4. The measurement method of claim 1, wherein, The threshold segmentation and the extraction of the region of interest are performed on the filtered image based on the maximum inter-class variance method to obtain the target image, and the target image includes the lithium battery electrode tab welding mark. The inter-class variance calculation and the intra-class variance calculation are performed on the filtered image by using the maximum inter-class variance method to obtain a target threshold value; The target image is binarized according to the target threshold value to obtain a segmented image; The region of interest is extracted from the segmented image to obtain the target image.

5. The measuring method according to any one of claims 1 to 4, wherein, The height of the lithium battery electrode tab welding mark corresponding to the sub-pixel coordinate is obtained based on the predetermined relationship and the sub-pixel coordinate, and the height of the lithium battery electrode tab welding mark corresponding to the sub-pixel coordinate is obtained based on the predetermined relationship and the sub-pixel coordinate. The target moving distance is calculated according to the sub-pixel coordinate and the reference coordinate of the reference point corresponding to the sub-pixel coordinate; The height of the lithium battery electrode tab welding mark corresponding to the sub-pixel coordinate is calculated according to the target moving distance and the predetermined relationship.

6. The measurement method according to claim 5, wherein, The line structure light projected on the lithium battery electrode tab by the new energy lithium battery welding height measurement system is blue line structure light or red line structure light.

7. A new energy lithium battery welding height measurement system for implementing the new energy lithium battery welding height measurement method in any one of claims 1-6, comprising: a laser for projecting line structure light on a lithium battery electrode tab; a camera for collecting the lithium battery electrode tab on which the line structure light is projected to obtain a light strip image, wherein the spatial positions of the laser, the lens of the camera and the photosensitive detector of the camera are determined by system parameters of the new energy lithium battery welding height measurement system, the system parameters of the new energy lithium battery welding height measurement system are calculated by using a Monte Carlo optimization algorithm with system sensitivity as an objective function, and the system sensitivity represents a moving distance of an image point corresponding to an object point on the lithium battery electrode tab when the object point moves a unit distance along a depth direction. a processor for performing grayscale on the light strip image to obtain a grayscale image, performing bilateral filtering on the grayscale image to obtain a filtered image, performing threshold segmentation and extracting a region of interest on the filtered image based on a maximum inter-class variance method to obtain a target image, wherein the target image includes a lithium battery electrode tab welding mark, performing sub-pixel center extraction on the target image based on a line center extraction algorithm to obtain sub-pixel coordinates of a light strip center line, and obtaining the height of the lithium battery electrode tab welding mark corresponding to the sub-pixel coordinates based on a predetermined relationship and the sub-pixel coordinates.

8. The measurement system of claim 7, wherein, The lens of the camera is an aspheric lens.

9. The measurement system of claim 7 or 8, wherein, A mobile platform is also included for placing the lithium battery pole piece and moving the lithium battery pole piece in a direction perpendicular to the light bar on the lithium battery pole piece based on a predetermined speed.

10. The measurement system of claim 7 or 8, wherein, Also included are: A narrow band filter is also included for filtering the line structured light reflected by the lithium battery pole piece before the line structured light reflected by the lithium battery pole piece passes through the lens of the camera.

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