CN114383517A - Battery expansion real-time detection method and device based on optical imaging - Google Patents
Battery expansion real-time detection method and device based on optical imaging Download PDFInfo
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- CN114383517A CN114383517A CN202111639683.1A CN202111639683A CN114383517A CN 114383517 A CN114383517 A CN 114383517A CN 202111639683 A CN202111639683 A CN 202111639683A CN 114383517 A CN114383517 A CN 114383517A
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- lithium ion
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/028—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring lateral position of a boundary of the object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/03—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring coordinates of points
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The device based on the traditional mechanical mechanics detection method has the technical problems of complex structure, low detection flux, complex detection and high detection cost of the existing optical method; the invention aims to provide a real-time battery swelling detection method based on an optical detection device, wherein the optical detection device comprises a lithium ion battery to be detected, a light-emitting diode arranged in front of the lithium ion battery and an electronic coupling element arranged behind the lithium ion battery, the light-emitting diode, the lithium ion battery and the electronic coupling element are aligned along the front-back direction, the light-emitting diode is used as a light source, and the electronic coupling element performs real-time optical imaging on the thickness of the battery in a transmission type imaging mode.
Description
Technical Field
The invention belongs to the field of lithium ion battery detection, and particularly relates to a method and a device for detecting battery expansion.
Background
Since the invention in the 90 s of the 20 th century, lithium ion batteries have been widely used in the field of energy storage, and the lithium ion batteries have the greatest advantages of high energy density and long-term cyclic charge and discharge. Meanwhile, with the reduction of the service life, the lithium ion battery is easy to catch fire and even explode, and how to improve the safety of the lithium ion battery becomes the most concerned problem in the field. It is gradually recognized that the volume expansion of lithium ion batteries during charging and discharging is closely related to the aging of the batteries. Therefore, there is a need for effective real-time detection of the volumetric expansion of the battery. The existing methods mainly comprise two types, one is a mechanical detection method based on mechanical sensing, and the other is an optical tomography imaging method based on X-rays. In the mechanical detection method, a flat lithium ion battery is fixed between two opposing pressure sensors (or micrometers), and a change in battery thickness is obtained as the battery is charged and discharged. The main drawbacks of this method are: (1) the device has a complex structure and is difficult to popularize in practical application; (2) the detection flux is low, and one device can only detect one battery at the same time; (3) the device has poor compatibility, is suitable for the soft package battery, but cannot detect the columnar battery; (4) the lack of spatial resolution, which detects thickness as an average thickness, does not reflect the thickness variation at different locations of the cell. For the optical tomography imaging method, the device is more complex, a set of X-ray generating and detecting device is needed, the battery is subjected to tomography scanning at different stages of charging and discharging, real-time detection is difficult, and the cost is extremely high.
Disclosure of Invention
The device based on the traditional mechanical mechanics detection method has the technical problems of complex structure, low detection flux, complex detection and high detection cost of the existing optical method; the invention aims to provide a real-time battery swelling detection method based on an optical detection device, wherein the optical detection device comprises a lithium ion battery to be detected, a light-emitting diode arranged in front of the lithium ion battery and an electronic coupling element arranged behind the lithium ion battery, the light-emitting diode, the lithium ion battery and the electronic coupling element are aligned along the front-back direction, the light-emitting diode is used as a light source, and the electronic coupling element performs real-time optical imaging on the thickness of the battery in a transmission type imaging mode;
the detection method comprises the following steps:
s01: image recording
Turning on switches of the light emitting diode and the electronic coupling element, starting recording an image of the lithium ion battery by the electronic coupling element, then starting a charge and discharge test of the lithium ion battery, stopping recording the image by the electronic coupling element after the charge and discharge test is finished, wherein the recorded image comprises a black orthographic projection area of the lithium ion battery and a white light source area surrounding the orthographic projection area, and a left transition area and a right transition area are formed between the left side and the right side of the orthographic projection area and the light source area;
s02: image processing
The method specifically comprises the following steps:
1) the height extension direction of the lithium ion battery is taken as the Y axis, the thickness extension direction thereof is taken as the X axis,
selecting the image of the left transition area, averaging the selected image along the Y-axis direction to obtain an original curve, wherein the selected image is changed from white to black from left to right, and the optical intensity of the corresponding original curve is changed from large to small along with the increase of the X-axis coordinate;
2) obtaining a first-order differential curve by deriving the original curve obtained in the step 1), and performing one-dimensional Gaussian fitting on the differentiated curve, wherein a fitting formula is as follows:
G(x)＝A*exp((x-B)^2/C^2)+D
in the above equation, a represents the first order differential curve height, B represents the first order differential curve center coordinate, C represents the first order differential curve standard deviation, and D represents the first order differential curve baseline height;
the edge position of the battery 1 is the parameter B in the formula, so that the limitation of pixels can be broken through by Gaussian fitting to obtain an accurate center coordinate, namely the left edge position X of the battery 1L；
3) Obtaining the right edge position X of the battery 1 by the methods of the step 1) and the step 2)RThickness d of the battery 11Can be expressed as d1＝XR-XL。
In some embodiments, an 80 x 80 pixel size image is manually selected at a location centered on the Y-axis at the left edge of the image.
The device comprises a lithium ion battery to be detected, a light emitting diode placed in front of the lithium ion battery and an electronic coupling element placed behind the lithium ion battery, wherein the light emitting diode, the lithium ion battery and the electronic coupling element are aligned in the front-back direction.
The invention takes a Light Emitting Diode (LED) as a light source, adopts a transmission type imaging mode, and performs real-time optical imaging on the thickness of a battery on an electronic coupling element (CCD). During the charging and discharging process of the lithium ion battery, the battery volume expands/contracts, so that the thickness of the battery is increased/reduced, and the displacement of the edge position on the battery image is reflected. And then, extracting the sub-pixel level displacement change through an edge fitting positioning algorithm to obtain the expansion characteristic of the battery.
Compared with the prior art, the invention has the following beneficial effects:
firstly, compared with the traditional mechanical method and optical method, the method disclosed by the invention has the advantages that the edge coordinates of the image are obtained by processing the battery orthographic projection image through the edge fitting algorithm, and further the expansion or contraction change of the battery is obtained, the battery only needs to be imaged in the process, and the non-contact nondestructive detection is completely realized.
Secondly, the detection device provided by the invention is simple and convenient to operate, low in cost and wide in application range; and the detection device can realize real-time expansion detection of a plurality of batteries simultaneously and has high flux.
Thirdly, the method has good compatibility and can carry out expansion detection on lithium ion batteries with different shapes. The method can be used for simultaneously detecting the expansion of a plurality of batteries in the charging and discharging processes in real time, and further detecting the states of the batteries (such as the SOC and the SOH) by using the parameters, thereby providing the battery state information besides the electrical parameters.
Figures and description
FIG. 1 is a schematic diagram of an optical detection device for detecting swelling of a lithium ion battery provided by the present invention;
FIG. 2 is a schematic view of an imaging of a lithium ion battery provided by the present invention;
FIG. 3 is a schematic diagram of an image processing process provided by the present invention;
fig. 4 is a lithium ion battery current, voltage, SOC and expansion detection curve provided in embodiment 1 of the present invention.
Detailed Description
Referring to fig. 1, an optical detection apparatus for detecting expansion of a lithium ion battery according to an embodiment of the present invention includes a light emitting diode 1 disposed in front of a lithium ion battery 2 and an electronic coupling element disposed behind the lithium ion battery 2, where the light emitting diode 1 is used as a light source and the electronic coupling element 3 is used as an image collector; the light emitting diode 1, the lithium ion battery 3 and the electronic coupling element 3 are aligned along the front and back directions, the light emitting diode is used as a light source, and the electronic coupling element performs real-time optical imaging on the thickness of the battery in a transmission type imaging mode;
according to the optical detection device for detecting the expansion of the lithium ion battery, the invention further provides an optical detection method for detecting the expansion of the lithium ion battery, which comprises the following steps:
s01: image recording
Turning on switches of the light emitting diode 1 and the electronic coupling element 3, setting appropriate parameters to enable the imaging of the lithium ion battery to be stable, and after the working state of the lithium ion battery is stable, firstly, starting to record an image of the lithium ion battery by using the electronic coupling element 3; then, carrying out a charge-discharge test on the lithium ion battery 2, and stopping recording the image of the electronic coupling element 3 after the charge-discharge test of the battery is finished; the whole process is carried out in an incubator at 25 ℃.
In the optical image, the size of each pixel value represents the number of photons received by the position, and is called optical intensity; as shown in fig. 2, in the aforementioned imaging mode, the recorded image includes a black forward projection area of the lithium ion battery and a white light source area surrounding the forward projection area, and a left transition area and a right transition area are formed between the left and right sides of the forward projection area and the light source area; the left transition area and the right transition area refer to the following parts: the area where the forward projection area and the white light source area are intersected covers the left edge and the right edge.
The optical intensity value of the white light source area is larger, the optical intensity value of the black orthographic projection area is smaller, and the boundary of the black and white area is the edge of the lithium ion battery.
S02: image processing
The image obtained in the step S01 is processed on an electronic computer, and because the battery expansion is very small and is often smaller than one pixel, the battery edge needs to be accurately positioned.
The edge fitting algorithm specifically comprises the following steps:
1) as shown in fig. 2, taking the left edge of the battery 1 as an example, the height extending direction of the lithium ion battery is taken as the Y axis, the thickness extending direction thereof is taken as the X axis, and an image with the size of 80 × 80 pixels is selected at the position centered on the Y axis in the left transition region of the image of the battery 1, as shown by the white frame in fig. 2; the images in the white frame are then averaged along the Y direction to obtain an 80 x 1 curve, as shown by the "original curve" labeled below in fig. 3. The purpose here in the Y direction is to eliminate image noise, the image in the white frame is changed from white to black from left to right, and the optical intensity corresponding to the original curve is changed from large to small as the X-axis coordinate is increased.
2) And (3) carrying out Gaussian fitting on a first-order differential curve obtained by deriving the original curve to obtain edge position coordinates: we define the position where the "raw curve" decays the fastest as the position of the left edge, i.e. the position where the greatest change in the derivative occurs. Therefore, after the "original curve" is differentiated to the first order, the "first order differential curve" in the figure is obtained, and the maximum value of the "first order differential curve" is the position of the left edge.
However, if the maximum value of the first-order differential curve is directly taken, only the positioning accuracy of the pixel level can be obtained; therefore, one-dimensional Gaussian fitting is further performed on the differentiated curve, and the fitting formula is as follows:
G(x)＝A*exp((x-B)^2/C^2)+D
in the above equation, a represents the height of the curve, B represents the coordinates of the center of the curve, C represents the standard deviation, and D represents the height of the base line.
Edge position of the battery 1I.e. the B parameter in the formula, so that the pixel limit can be broken through by gaussian fitting to obtain the accurate center coordinate, i.e. the left edge position X of the battery 1L。
3) Obtaining the right edge position X of the battery 1 by the method of the above stepsRThickness d of the battery 11Can be expressed as d1＝XR-XL。
Example 1
Taking 18650 cylindrical lithium ion batteries of Shenzhen Shenhuo AB3 model produced by Shenzhen Shenhuo Lighting company as an example, an experimental device is firstly constructed according to the method described in S01, the exposure time is set to be 3ms by the parameters of the CCD, and the sampling rate is 1 fps. The battery charge and discharge parameters are as follows (rated capacity 2300 mAh): charging with constant current: 2.3A until the voltage reaches 4.2V; charging at constant voltage: 4.2V charging to the current less than 100 mA; constant current discharge: 2.3A to a voltage of less than 2.75V. The battery charging and discharging control and the recording of the electrical parameters are completed by a blue CT3001C battery testing system. At different moments, the electrical states of the batteries are different, the images recorded at each moment are fitted according to the method of S02, so that the thicknesses of the batteries at different moments can be obtained, and the expansion value is obtained by subtracting the initial thicknesses of the batteries from the thicknesses of the batteries at all moments. Fig. 4 shows the expansion curve of the battery at two charge-discharge cycles for the corresponding current, voltage and SOC.
Claims (3)
1. The battery expansion real-time detection method based on the optical detection device is characterized in that the optical detection device comprises a lithium ion battery to be detected, a light emitting diode arranged in front of the lithium ion battery and an electronic coupling element arranged behind the lithium ion battery, wherein the light emitting diode, the lithium ion battery and the electronic coupling element are aligned along the front-back direction, the light emitting diode is used as a light source, and the electronic coupling element performs real-time optical imaging on the thickness of the battery in a transmission type imaging mode;
the detection method comprises the following steps:
s01: image recording
Turning on switches of the light emitting diode and the electronic coupling element, starting recording an image of the lithium ion battery by the electronic coupling element, then starting a charge and discharge test of the lithium ion battery, stopping recording the image by the electronic coupling element after the charge and discharge test is finished, wherein the recorded image comprises a black orthographic projection area of the lithium ion battery and a white light source area surrounding the orthographic projection area, and a left transition area and a right transition area are formed between the left side and the right side of the orthographic projection area and the light source area;
s02: image processing
The method specifically comprises the following steps:
1) the height extension direction of the lithium ion battery is taken as the Y axis, the thickness extension direction thereof is taken as the X axis,
selecting the image of the left transition area, averaging the selected image along the Y-axis direction to obtain an original curve, wherein the selected image is changed from white to black from left to right, and the optical intensity of the corresponding original curve is changed from large to small along with the increase of the X-axis coordinate;
2) obtaining a first-order differential curve by deriving the original curve obtained in the step 1), and performing one-dimensional Gaussian fitting on the differentiated curve, wherein a fitting formula is as follows:
G(x)＝A*exp((x-B)^2/C^2)+D
in the above equation, a represents the first order differential curve height, B represents the first order differential curve center coordinate, C represents the first order differential curve standard deviation, and D represents the first order differential curve baseline height;
the edge position of the battery 1 is the parameter B in the formula, so that the limitation of pixels can be broken through by Gaussian fitting to obtain an accurate center coordinate, namely the left edge position X of the battery 1L；
3) Obtaining the right edge position X of the battery 1 by the methods of the step 1) and the step 2)RThickness d of the battery 11Can be expressed as d1＝XR-XL。
2. The method of claim 1, wherein an image of 80 x 80 pixels is manually selected at a position centered on the Y-axis at the left edge of the image.
3. The device for detecting the battery expansion in real time based on optical imaging is characterized by comprising a lithium ion battery to be detected, a light emitting diode placed in front of the lithium ion battery and an electronic coupling element placed behind the lithium ion battery, wherein the light emitting diode, the lithium ion battery and the electronic coupling element are aligned in the front-back direction.
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