Online measurement and testing system for uniformity of power battery pole piece coating

Abstract

The present invention discloses an online measurement and testing system for the uniformity of coating on a power battery pole piece, which mainly includes an optical imaging system, a computer, and an image acquisition card connecting the optical imaging system and the computer; the optical imaging system is used to generate a light source whose uniformity, stability and brightness meet the detection requirements, including a first laser module, a second laser module, an infrared LED module, and a binocular camera shooting device; the first laser module and the second laser module are used for thickness uniformity detection, and the infrared LED module is used to detect defects on the surface of the power battery pole piece; the computer includes a control unit and an image processing unit; the output end of the control unit is connected to the optical imaging system, which is used to set and optimize the parameter values ​​of the optical imaging system, calculate the accurate thickness of the pole piece, and detect defects on the surface of the pole plate. The present invention can realize the simultaneous detection of the uniformity of the thickness of the power battery pole piece and the defect detection.

Description

Technical Field

[0001] The present invention relates to the field of optical detection, and in particular to an online measurement and testing system for uniformity of a power battery pole piece coating. Background Art

[0002] In recent years, with the promotion and application of new energy vehicles, power batteries have entered a large-scale practical stage. In the coating process of power battery pole pieces, defects such as voids and scratches are prone to occur on the surface, and the coating thickness is uneven, which will seriously affect the quality and service life of the battery. At present, some lithium battery pole piece detection technologies based on machine vision can realize the detection of defects such as voids and scratches, but the image quality requirements of optical imaging are relatively high; for the thickness measurement of non-transparent films such as power battery pole pieces, the more commonly used online thickness measurement method is the upper and lower differential laser triangulation method. This method requires the upper and lower laser heads to be precisely synchronized. The widely used thickness measurement form based on the C-frame scanning thickness measurement design will cause the upper and lower beams of the C-frame to vibrate or even slightly deform during the actual measurement process, making the distance between the upper and lower laser heads unstable, which will cause large deviations in micron-level thickness measurement. At present, there is no solution that can simultaneously realize the uniformity of power battery pole piece thickness and the simultaneous detection of defects. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an online measurement and testing system for the uniformity of coating on a power battery pole piece, which can realize the simultaneous detection of thickness uniformity and defect detection on the power battery pole piece.

[0004] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide an online measurement and testing system for the uniformity of a power battery pole piece coating, which mainly includes an optical imaging system, a computer, and an image acquisition card connecting the optical imaging system and the computer;

[0005] The optical imaging system is used to generate a light source whose uniformity, stability and brightness meet the detection requirements, and includes a first laser module, a second laser module, an infrared LED module, and a binocular camera shooting device; the first laser module and the second laser module are used for thickness uniformity detection, the infrared LED module is used to detect defects on the surface of the power battery pole piece, and the binocular camera shooting device uses two cameras that combine bright field and dark field imaging receiving modes to obtain the surface image of the pole piece to be detected;

[0006] The computer includes a control unit and an image processing unit; the output end of the control unit is connected to the optical imaging system, which is used to set and optimize the parameter values ​​of the optical imaging system, calculate the accurate thickness of the electrode piece, and detect defects on the surface of the electrode plate;

[0007] The image acquisition card is used to convert the image data collected by the camera into a data format recognizable by a computer, and send it to the image processing unit, which analyzes, processes and recognizes the detection target features.

[0008] In a preferred embodiment of the present invention, the optical imaging system uses an in-line C-shaped fixed bracket as the main structure, including a bracket body, an upper beam installed at the upper end of the bracket body, and a lower beam installed at the lower end of the bracket body, and the upper beam and the lower beam are located on the same side of the bracket body;

[0009] The first laser module, the infrared LED module, and the binocular camera shooting device are arranged on the lower surface of the upper beam and in a straight line; the second laser module is arranged on the upper surface of the lower beam.

[0010] Furthermore, the optical imaging system also includes a sliding guide rail arranged between the upper beam and the lower beam, and a stage is arranged on the sliding guide rail, and the pole piece to be measured is fixed on the stage.

[0011] In a preferred embodiment of the present invention, the control unit sets and optimizes the parameter values ​​of the optical imaging system including parameters of the defect type to be detected, LED infrared light source parameters, and binocular camera shooting device parameters. The LED infrared light source parameters include illumination angle and brightness, and the binocular camera shooting device parameters include light and dark domain positions and scanning frequency.

[0012] Furthermore, the binocular camera shooting device includes a bright domain camera and a dark domain camera, and adopts a linear array CCD multi-spectral integrated camera to capture images of different defects on the surface of the lithium battery plate.

[0013] In a preferred embodiment of the present invention, the first laser module is used to emit a laser beam vertically to the upper surface of the pole piece to be tested, and the second laser module is used to emit a laser beam vertically to the lower surface of the pole piece to be tested, and the laser beam emitted by the first laser module and the laser beam emitted by the second laser module are on the same straight line and in the vertical direction.

[0014] Furthermore, the configuration parameters of the first laser module and the second laser module, including laser source wavelength, spot diameter, scanning frequency, light source interval, and light source number, are completely the same.

[0015] Furthermore, the first laser module and the second laser module include a plurality of laser sources that are linearly distributed at intervals. The laser sources in the first laser module and the second laser module that are located in the same vertical direction constitute a group. Each group of light sources synchronously irradiates the same horizontal position on the upper and lower surfaces of the pole piece, thereby realizing simultaneous thickness measurement of multiple positions on the upper and lower surfaces of the pole piece.

[0016] Furthermore, the interval between the laser sources is determined by the recognition resolution of the pole piece.

[0017] In a preferred embodiment of the present invention, the computer further comprises a display unit, an execution unit, and an alarm unit connected in sequence, and the input end of the display unit is connected to the image processing unit. The test results can be viewed on terminals such as mobile phones and tablets, and on-site warnings and emergency operations can be performed on unqualified electrodes, making the system more convenient to use and highly intelligent.

[0018] The beneficial effects of the present invention are:

[0019] (1) The optical imaging system designed in the present invention focuses on solving the speed matching and recognition matching problems of the two scanning states of the power battery plate coating uniformity detection and defect detection, and realizes the full-surface detection of thickness uniformity detection and defect detection simultaneously. The development of this system will reduce production costs and greatly improve product quality for power battery manufacturers. First, it can synchronize the detection work with the production equipment, and it can make the online detection of the plate more accurate through full-area detection; secondly, the detection work is automatically detected without human intervention, and the detection data can be uploaded to the remote server in real time. The system software can complete the subsequent data error analysis based on these data, thereby saving a lot of manpower and material resources for on-site testing; finally, it can greatly improve product quality, so that the power battery can obtain product quality data in the early stage of production, avoiding the discovery of product quality defects after the product production is completed;

[0020] (2) All laser sources in the optical imaging system are vertically irradiated onto the upper and lower surfaces of the pole piece. When arranged, they are located in the same scanning plane and there is no scanning blind area. There is a repeated scanning area between the upper and lower multiple laser sources, so that the same position can be scanned by multiple laser sources, thereby obtaining multiple thickness measurement values ​​at the same scanning position on the pole piece surface. This can not only cope with random disturbances such as the upper and lower vibrations of the stage that affect the thickness measurement, but also provide a more accurate measurement method for the thickness measurement of the pole piece; the upper and lower uniformity detection accuracy is ≤±0.002mm (single side); by optimizing the parameters of the deep convolutional neural network and the image acquisition card when working synchronously with the camera and the pole piece movement by the control unit, good system performance is obtained, the plate recognition rate is ≥50m / min, the designed scanning width is ≥650mm, and the defect recognition accuracy is ≤0.05mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural block diagram of a preferred embodiment of the online measurement and testing system for the uniformity and property of the power battery pole piece coating of the present invention;

[0022] Figure 2 It is a structural block diagram of the optical imaging system. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0024] See also Figure 1 , the embodiment of the present invention includes:

[0025] An online measurement and testing system for the uniformity of the coating on a power battery pole piece mainly includes an optical imaging system, a computer, and an image acquisition card connecting the optical imaging system and the computer. The computer includes a control unit and an image processing unit; the output end of the control unit is connected to the optical imaging system for setting and optimizing the parameter values ​​of the optical imaging system, calculating the accurate thickness of the pole piece, and detecting defects on the surface of the pole plate. The image acquisition card is used to convert the image data collected by the camera into a data format recognized by the computer, and send it to the image processing unit, which analyzes, processes and recognizes the characteristics of the detection target.

[0026] The optical imaging system is used to generate a light source whose uniformity, stability and brightness meet the detection requirements, and includes a first laser module, a second laser module, an infrared LED module, and a binocular camera shooting device. The first laser module and the second laser module are used for thickness uniformity detection, the infrared LED module is used to detect defects on the surface of the power battery pole piece, and the binocular camera shooting device uses two cameras that combine bright field and dark field imaging receiving modes to obtain the surface image of the pole piece to be detected.

[0027] Combination Figure 2 The optical imaging system adopts an in-line C-shaped fixed bracket as the main structure, including a bracket body, an upper beam installed at the upper end of the bracket body, a lower beam installed at the lower end of the bracket body, and a sliding guide rail arranged between the upper beam and the lower beam, and the upper beam and the lower beam are located on the same side of the bracket body. The first laser module, the infrared LED module, and the binocular camera shooting device are arranged on the lower surface of the upper beam and are arranged in a straight line, and the second laser module is arranged on the upper surface of the lower beam. The binocular camera shooting device includes a bright field camera and a dark field camera. Preferably, a linear array CCD multi-spectral integrated camera is used to capture images of different defects on the surface of the lithium battery plate. A stage is provided on the sliding guide rail, and the pole piece to be tested is fixed on the stage to move back and forth horizontally in a Z shape, so that the thickness and defects at different positions on the surface of the pole piece can be given. Preferably, the stage uses a square stage, and the size can be flexibly replaced according to the size of the pole plate to be tested.

[0028] Specifically, the first laser module is used to emit a laser beam vertically to the upper surface of the pole piece to be tested, and the second laser module is used to emit a laser beam vertically to the lower surface of the pole piece to be tested. The laser beam emitted by the first laser module and the laser beam emitted by the second laser module are on the same straight line and in the vertical direction. The configuration parameters of the first laser module and the second laser module include the laser source wavelength, spot diameter, scanning frequency, light source interval, and number of light sources are exactly the same. The infrared LED module is used to generate an infrared light source to irradiate the upper surface of the pole piece to be tested at a certain angle, and the two linear array CCD cameras are used to receive bright domain and dark domain imaging.

[0029] The optical imaging system uses the control unit to set various control parameters, including parameters of the defect type to be detected; LED infrared light source parameters, including irradiation angle and brightness; and linear array CCD camera parameters, including light and dark domain positions and scanning frequency.

[0030] Specifically, the control unit receives the pole plate transmission speed information sensed by the encoder on the pole piece transmission device, and uses the built-in new information adaptive Kalman filter algorithm to perform high-precision speed measurement, and searches the built-in dictionary of the relationship between the defect type to be detected, the pole plate transmission speed, the LED infrared light source, and the linear array CCD camera parameters to obtain the current LED infrared light source and linear array CCD camera parameter values ​​and set them.

[0031] The parameter relationship dictionary is established by transmitting electrode samples of different defect types (such as wrinkles, pitting defects or scratch defects) at different speeds, and then adjusting the LED infrared light source parameters and the linear array CCD camera parameters until the collected defect image meets the preset detection conditions. At this time, the relevant parameters are stored to establish the parameter relationship dictionary.

[0032] In principle, the preset detection conditions should satisfy that the acquired defect detection image is helpful to more accurately identify the defect feature points. In actual operation, when the defect detection accuracy of the acquired defect detection image given by the built-in electrode surface defect recognition model is not lower than a specific threshold, it is considered that the preset detection conditions are met at this time. At this time, a set of defect types to be detected, electrode transmission speed, LED infrared light source and linear array CCD camera parameters are stored in the parameter relationship dictionary.

[0033] In order to obtain high-efficiency thickness measurement, the first laser module and the second laser module include a number of laser sources distributed linearly at intervals. The laser sources located in the same vertical direction in the first laser module and the second laser module constitute a group. Each group of light sources synchronously irradiates the same horizontal position on the upper and lower surfaces of the pole piece, thereby realizing simultaneous thickness measurement of multiple positions on the upper and lower surfaces of the pole piece.

[0034] Preferably, the thickness measurement accuracy is also affected by the stability of the laser module and the reasonable ratio of the structural parameters. The laser source wavelength, spot diameter, scanning frequency, light source interval, number of light sources and other configurations are also set by the control unit. The built-in optimization control algorithm is used to calculate the economic minimum configuration parameters that meet the thickness measurement index requirements. By default, a millimeter-level high-resolution laser source is selected, and the light source interval is linearly evenly arranged. The default number configuration is 18 (a total of 36). The thickness measurement indicators include thickness uniformity detection accuracy, scanning width, plate recognition rate and resolution, etc.

[0035] In order to obtain high-precision thickness measurement, objects of different known thicknesses can be placed on the stage for measurement to obtain compensation offsets at different thicknesses, where compensation offset = true thickness - measured thickness, and the compensation amount is set in the control unit. Preferably, the compensation offset can be calculated using a least squares fitting method to give a more precise compensation offset at a finer thickness.

[0036] Specifically, when the thickness of the same batch of power battery pole pieces is measured for the first time, a compensation offset calibration is required. When the thickness is measured again, the positions of the two laser modules are kept fixed, and the compensation offset is a fixed value, and no recalibration is required.

[0037] In order to cope with random disturbances that affect thickness measurement, such as the up and down vibration of the stage, all the laser sources are vertically irradiated onto the upper and lower surfaces of the pole piece. They are arranged in the same scanning plane and there is no scanning blind area. There is a repeated scanning area between the upper and lower multiple laser sources, so that the same position can be scanned by multiple laser sources, thereby obtaining multiple thickness measurement values ​​at the same scanning position on the pole piece surface. On this basis, the final thickness measurement value is given by looking up the compensation offset calculated in advance in the control unit, that is, the final thickness measurement value = measurement value + compensation offset, and the measurement value can be a weighted average given by multiple measurement values.

[0038] The present invention can measure the thickness of multiple positions on the upper and lower surfaces of the pole piece at the same time, and has a high thickness measurement efficiency; the proposed compensation offset fitting method can calculate and give a refined thickness measurement value, and the upper and lower uniformity detection accuracy is ≤±0.002mm (single side).

[0039] Furthermore, a starting position sensor and an end position sensor are provided on the stage, corresponding to the starting position and the end position of the pole piece. Under the signal identification of the sensor, according to the set size of the repeated scanning area, the sliding guide rail aligns the starting position point of the pole piece with the corresponding laser source, and turns on / off the corresponding laser source during the movement of the pole piece. The position interval of each scanning point of the pole piece (i.e., the recognition resolution) is determined by the laser source interval, and the coordinates of each scanning point are calibrated using Zhang You's plane calibration method. The laser source interval is determined by the minimum step distance of the sliding guide rail. When configuring the laser module, it is necessary to ensure that the laser source interval is the same as the minimum step distance. The sliding guide rail is controlled by a stepper motor, and the minimum step distance is set using subdivision drive technology.

[0040] The image acquisition card is the transmission bridge between the camera and the computer. To ensure the synchronization of the image acquisition card with the camera and the movement of the pole piece, the image acquisition frequency and transmission speed parameters are optimized and calculated by the control unit and adjusted in real time.

[0041] The computer image processing unit is used to verify the image after the data conversion is completed, and use image processing algorithms such as coordinate transformation, image graying, image enhancement, image filtering, image segmentation and edge detection, etc., to analyze, process and identify the detection target features. Specifically, a comprehensive analysis of multiple bright and dark domain image information obtained from multiple illumination angles is used to perform defect detection. After generating a grayscale image of the surface of the power battery pole piece, a sample enhanced image and image annotation processing, the computer image processing unit uses it as a sample data set to train a deep convolutional neural network based on the cross entropy function. The grayscale image of the surface of the power battery pole piece to be detected is input into the trained deep convolutional neural network to realize the surface defect detection of the power battery pole piece.

[0042] In another embodiment, the computer further comprises a display unit, an execution unit, and an alarm unit which are connected in sequence, and an input end of the display unit is connected to the image processing unit.

[0043] The display unit is used to visualize the surface inspection status of each power battery pole piece on a large screen, including the batch number, system number, inspection time, operator information, etc. of the current inspection pole piece, as well as the number of inspected pole pieces, the number of pole pieces to be inspected, the number of qualified pole pieces, etc. The display unit also supports display on mobile phones, tablets, computers and other terminals, and can give the batch number of unqualified power batteries with one click, and supports data export.

[0044] The execution unit is used to perform operations after detecting unqualified power battery plates. The execution unit can be customized according to customer needs, such as automatic shutdown, providing an abnormal identification signal, or marking the plate coating.

[0045] The alarm unit is used to issue an alarm after detecting unqualified power battery electrodes. It supports voice broadcast, large screen pop-up window, sound and light alarm, etc.

[0046] As a further optimization scheme of the present invention, the system can view the test results on terminals such as mobile phones and tablets, and can perform on-site early warning and emergency operations for unqualified electrodes, making the system more convenient to use and highly intelligent.

[0047] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An online measurement and testing system for uniformity of power battery pole piece coating, characterized in that: It mainly includes an optical imaging system, a computer, and an image acquisition card connecting the optical imaging system and the computer; The optical imaging system is used to generate a light source whose uniformity, stability and brightness meet the detection requirements, and includes a first laser module, a second laser module, an infrared LED module, and a binocular camera shooting device; the first laser module and the second laser module are used for thickness uniformity detection, the infrared LED module is used to detect defects on the surface of the power battery pole piece, and the binocular camera shooting device uses two cameras that combine bright field and dark field imaging receiving modes to obtain the surface image of the pole piece to be detected; The first laser module and the second laser module include a plurality of laser sources that are linearly distributed at intervals. The laser sources in the first laser module and the second laser module that are located in the same vertical direction form a group. Each group of light sources synchronously irradiates the same horizontal position on the upper and lower surfaces of the pole piece, thereby realizing thickness measurement of multiple positions on the upper and lower surfaces of the pole piece at the same time. The intervals between the laser sources are determined by the recognition resolution of the pole piece. The computer includes a control unit and an image processing unit; the output end of the control unit is connected to the optical imaging system, which is used to set and optimize the parameter values ​​of the optical imaging system, calculate the accurate thickness of the electrode piece, and detect defects on the surface of the electrode plate; The image acquisition card is used to convert the image data collected by the camera into a data format recognizable by a computer, and send it to the image processing unit, which analyzes, processes and recognizes the detection target features.

2. The power battery pole piece coating uniformity online measurement and testing system according to claim 1 is characterized in that: The optical imaging system adopts an in-line C-shaped fixed bracket as the main structure, including a bracket body, an upper beam installed at the upper end of the bracket body, and a lower beam installed at the lower end of the bracket body, wherein the upper beam and the lower beam are located on the same side of the bracket body; The first laser module, the infrared LED module, and the binocular camera shooting device are arranged on the lower surface of the upper beam and in a straight line; the second laser module is arranged on the upper surface of the lower beam.

3. The power battery pole piece coating uniformity online measurement and testing system according to claim 2 is characterized in that: The optical imaging system further comprises a sliding guide rail arranged between the upper beam and the lower beam, a loading platform is arranged on the sliding guide rail, and the pole piece to be measured is fixed on the loading platform.

4. The power battery pole piece coating uniformity online measurement and testing system according to claim 1 is characterized in that: The control unit sets and optimizes the parameter values ​​of the optical imaging system, including the defect type parameters to be detected, the LED infrared light source parameters, and the binocular camera shooting device parameters. The LED infrared light source parameters include the irradiation angle and brightness, and the binocular camera shooting device parameters include the light and dark domain positions and the scanning frequency.

5. The power battery pole piece coating uniformity online measurement and testing system according to any one of claims 1, 2 or 4, characterized in that: The binocular camera shooting device includes a bright-domain camera and a dark-domain camera, and adopts a linear array CCD multi-spectral integrated camera to shoot images of different defects on the surface of the lithium battery plate.

6. The power battery pole piece coating uniformity online measurement and testing system according to claim 1 is characterized in that: The first laser module is used to emit a laser beam vertically to the upper surface of the pole piece to be tested, and the second laser module is used to emit a laser beam vertically to the lower surface of the pole piece to be tested. The laser beam emitted by the first laser module and the laser beam emitted by the second laser module are on the same straight line and in the vertical direction.

7. The power battery pole piece coating uniformity online measurement and testing system according to any one of claims 1, 2 or 6, characterized in that: The configuration parameters of the first laser module and the second laser module, including laser source wavelength, spot diameter, scanning frequency, light source interval, and light source number, are completely the same.

8. The power battery pole piece coating uniformity online measurement and testing system according to claim 1 is characterized in that: The computer further comprises a display unit, an execution unit and an alarm unit which are connected in sequence, and an input end of the display unit is connected to the image processing unit.

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