A method for measuring the size of a battery using CCD vision

Abstract

A method for measuring the size of a battery using a CCD vision system, the specific steps are as follows: Build a CCD vision measurement system; accurately measure the distances between the reference edges and the reference origin on the test bench; the CCD camera passes directly above the right-angle coordinate systems 1 / 2 / 3 / 4 on the test bench in sequence, generating 4 rectangular coordinate windows of the measured points; place the battery to be measured on the test bench and establish 4 right-angle coordinate systems through the reference edges and the reference origin; after the right-angle coordinate systems are established, it is necessary to calibrate the scale of the optical ruler on the CCD image using a gauge block of known size, and establish a functional relationship between the actual size and the size represented by a single pixel on the image; after the CCD measurement system calibrates the scale of the right-angle coordinate system, a measurement quadrant interface will be formed. The CCD camera takes a photo of the battery to be measured to generate a black-and-white image, selects the corresponding measurement points on the black-and-white image, and quickly obtains the position coordinates of the corresponding measurement points on the right-angle coordinate system. The size data of each part of the battery required is obtained through the position coordinates of each measurement point.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery size measurement, and particularly relates to a method for measuring battery size by CCD vision measurement. Background Art

[0002] At the end of the production and manufacturing process of lithium-ion soft-pack batteries, a CCD vision measurement system is required to measure the external dimensions of the batteries, including data such as the length, width, tab size, and corner cut size of the batteries. Measuring the battery size with traditional contact sensors will cause defects in the appearance of soft-pack batteries. Therefore, the non-contact size measurement system is the preferred method for detecting the external dimensions of soft-pack batteries. CCD vision measurement is a commonly used non-contact method for measuring the external dimensions of batteries, which consists of components such as a CCD camera, vision measurement software, light source, test platform, and size standard block.

[0003] There are problems with the CCD vision measurement system installed on-site equipment, such as the CMK index of battery external dimension measurement < 1.67 (unqualified), the MSA of the size measurement system is unqualified, the measured values of battery size are discrete, and there is a large deviation between the measured value and the actual value. This is because the method for calibrating the image size on the vision software after the CCD vision measurement system is installed and debugged is not good enough, relying too much on the processing and manufacturing accuracy of the size standard block and the placement position of the battery on the test platform. If the placement position of the battery on the test bench deviates greatly, the CCD image size cannot be accurately measured; if the processing and manufacturing accuracy of the size standard block is insufficient, the CCD vision measurement error after calibration with the standard block will also increase, ultimately resulting in a large deviation between the measured value of the battery size and the actual value, the CMK index being unqualified, and the MSA measurement system analysis not being accepted. Summary of the Invention

[0004] To solve the above problems existing in the current technology, the present invention provides a method for measuring battery size by CCD vision, which solves the problems that the traditional CCD vision measurement system relies too much on the high processing and manufacturing accuracy of the size standard block and the high positioning accuracy of the battery on the test bench, and is relatively cost-saving.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for measuring battery size by CCD vision, the specific steps are as follows:

[0007] S1, Set up a CCD vision measurement system;

[0008] S2, Accurately measure the distances between each reference edge and the reference origin on the test platform;

[0009] S3, debug the servo motion program so that the CCD camera passes directly above the rectangular coordinate systems 1 / 2 / 3 / 4 on the test bench in sequence, and four rectangular coordinate windows of the measured points are generated on the test software respectively;

[0010] S4, placing the battery to be tested on the test bench, establishing four rectangular coordinate systems on the CCD measurement software using the reference edges P1 to P8 and the reference origins O1 to O4, and obtaining the required dimensional data of the battery using the above point coordinates to obtain the corresponding preset formula;

[0011] S5, use a high-precision block gauge to calibrate the CCD measurement system. After the rectangular coordinate system is established, a block gauge of known size is used to calibrate the scale of the optical ruler on the CCD image, and a functional relationship is established between the actual size and the size represented by the unit pixel on the image;

[0012] S6. After the CCD measurement system is calibrated with the rectangular coordinate system, a measurement quadrant interface will be formed. The CCD camera takes a picture of the battery under test to generate a black and white image. The CCD vision software captures the image outline, selects the corresponding measurement points on the black and white image, and quickly obtains the point coordinates of the corresponding measurement points on the rectangular coordinate system. The point coordinates of each measurement point are then imported into the preset formula to obtain the required battery size data.

[0013] Furthermore, the hardware construction steps of the CCD vision measurement system in step S1 are as follows:

[0014] S11, a servo motion system for driving the CCD camera to move so that the CCD camera is located above the test bench;

[0015] S12, the test bench is made of a flat high-transmittance glass plate, with measurement reference edges and reference origins for CCD visual positioning at the four corners, and a battery under test with tabs;

[0016] S13. A light source is set below the test bench;

[0017] S14, the CCD camera is connected to a CCD controller for storing the collected battery size data via a data cable;

[0018] S15, CCD controller is connected to the working computer with a communication line, and the working computer is equipped with CCD visual measurement software for calibrating the dimensions of the rectangular coordinate system and performing image analysis using a high-precision block gauge.

[0019] Furthermore, the servo motion system in step S11 includes an X-axis direction control system composed of an X-axis servo motor, an X-axis coupling and an X-axis servo module, and a Y-axis direction control system composed of a Y-axis servo motor, a Y-axis coupling and a Y-axis servo module. The X-axis direction control system and the Y-axis direction control system together constitute a planar motion control system.

[0020] Further, the color of the reference edge in step S12 is black.

[0021] Further, in step S4, it also includes debugging the parameters of the light source and the CCD camera to make the image of the battery under test being photographed clear and accurate, and the contrast between the black and white images being obvious.

[0022] Further, the dimensions of the battery to be measured in step S4 include: the corner cutting dimensions of the battery with four corner cuts, the battery width dimension, the length dimension of the battery without tabs, and the length dimension of the battery with tabs.

[0023] Further, for each corner cutting dimension of the battery with a corner cut, the length and width dimensions of the cut-off part of the corner cut can be obtained through the coordinate differences between the point position coordinates at both ends.

[0024] Further, for the battery width dimension, by measuring the point position coordinates of the points on the two opposite boundaries in the width direction of the battery under test, and then based on the distance between the reference edges on the Y-axis, the battery width dimension can be calculated.

[0025] Further, for the length dimension of the battery without tabs and the length dimension of the battery with tabs, by measuring the point position coordinates of the points on the two opposite boundaries in the corresponding length direction of the battery under test, and then based on the distance between the reference edges on the X-axis, the corresponding length dimension of the battery without tabs and the length dimension of the battery with tabs can be calculated.

[0026] Further, in step S5, a high-precision gauge is used to repeatedly calibrate the scale of the coordinate system.

[0027] Advantages of the present invention: Since the measurement points on the image of the battery under test are converted into the point position coordinates of the rectangular coordinate system, and then the linear distances are calculated between the coordinates of each measurement point to obtain the battery size data, this eliminates the influence of the placement position of the battery on the test bench on the size measurement result. Using a high-precision gauge to repeatedly calibrate the scale of the coordinate system, this method improves the accuracy by several orders of magnitude compared to the original method of calibrating the optical scale with a size standard block, and the size measurement value will be more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the hardware structure of the CCD vision measurement system of the present invention.

[0029] Figure 2 It is a schematic diagram of the structure for setting the point position coordinates to be measured of the battery under test of the present invention.

[0030] Figure 3 It is a schematic diagram of repeatedly calibrating the scale of the coordinate system with a high-precision gauge of the present invention.

[0031] Figure 4 It is a schematic diagram of the point position coordinates of the measurement point of the A corner cut of the present invention in the direct coordinate system.

[0032] Figure 5 This is an example diagram of the measured data of the length of the chamfered corner of the battery under test of the present invention.

[0033] Figure 6 This is an example diagram of the measured data of the width of the chamfered corner of the battery under test of the present invention. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific implementation manners. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions and equivalent solutions that may be included within the scope of the claims.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more, unless otherwise clearly defined.

[0036] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed" and other terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0038] Professional terms:

[0039] CCD camera: CCD is a semiconductor device that can convert optical images into digital signals. A camera equipped with such a semiconductor device is called a CCD camera.

[0040] CMK index: Machine capability index, which is used to evaluate the applicability of a machine to a special requirement.

[0041] MSA: Measurement System Analysis.

[0042] Gauge block: A gauge with a certain shape but different sizes.

[0043] Test bench: A highly transparent glass plate on which the battery under test is placed. The light source is below the test bench. The light irradiates on the test bench, and the light blocked by the battery is reflected away, while the unblocked light is transmitted to the CCD camera to form a black-and-white distinct image.

[0044] Servo module: Driven by a servo motor, it converts the pulse signal of the servo motor into a position coordinate and drives the CCD camera to move.

[0045] This embodiment provides a method for measuring the size of a battery by CCD vision, and the specific steps are as follows:

[0046] S1. Build the hardware of the CCD vision measurement system;

[0047] See Figure 1 and the specific steps are as follows:

[0048] S11. A servo motion system that drives the CCD camera 7 to move, so that the CCD camera 7 is located above the test bench 8; wherein the servo motion system includes an X-axis direction control system composed of an X-axis servo motor 1, an X-axis coupling 2 and an X-axis servo module 3, and a Y-axis direction control system composed of a Y-axis servo motor 4, a Y-axis coupling 5 and a Y-axis servo module 6. The X-axis direction control system and the Y-axis direction control system jointly form a planar motion control system.

[0049] S12, the test bench 8 is made of a flat high-transmittance glass plate, with measurement reference edges 81 and reference origins 82 for CCD visual positioning at the four corners, and a battery under test 9 with tabs 91;

[0050] The present invention uses a test bench 8 with a measurement reference edge, and the color of the reference edge 81 is black for easy observation, so that it can be used for the CCD visual measurement system to establish a high-precision rectangular coordinate system;

[0051] S13, a light source 10 is set below the test bench 8;

[0052] S14, the CCD camera 7 is connected to a CCD controller 12 for storing the collected battery size data via a data line 11;

[0053] S15, the CCD controller 12 is connected to the working computer 14 by a communication line 13. The working computer 14 is equipped with CCD visual measurement software for calibrating the dimensions of the rectangular coordinate system and performing image analysis using a high-precision block gauge.

[0054] S2, accurately measuring the distance between each reference edge 81 and the reference origin 82 on the test bench 8;

[0055] S3: Debug the servo motion program so that the CCD camera 7 passes sequentially over the rectangular coordinate systems 1 / 2 / 3 / 4 on the test bench 8, generating four rectangular coordinate windows for the measured points in the test software. The servo module drives the CCD camera 7 to sequentially position itself over the four corners of the battery to take pictures, obtaining the coordinate data of the four corners of the battery. The battery's dimensional data is then calculated using the measurement software. The spacing between the origins of the four rectangular coordinate systems on the test bench is measured in advance with high precision. The parallelism of the corresponding reference edges on the test bench is very high, and the test bench is manufactured with very high precision.

[0056] S4, place the battery 9 under test on the test table 8, and establish four rectangular coordinate systems on the CCD measurement software through the reference edges P1 to P8 and the reference origins O1 to O4, see Figure 2 , obtain the size data of the battery that needs to be measured through the above point coordinates and obtain the corresponding preset formula;

[0057] The dimensions of the battery that need to be measured include: the battery corner cutting dimensions of the four corners, the battery width dimension, the battery length dimension without the tabs, the battery length dimension with the tabs, and other dimensions are also possible.

[0058] 1. The length and width of the cut-off portion of each corner of the battery can be obtained by the coordinate difference between the coordinates of the points at both ends. Specifically, the battery has four corners, namely A, B, C, and D. Taking corner A as an example, the length and width of the cut-off portion of corner A can be calculated by the coordinate difference between points B and C;

[0059] 2. The battery width dimension can be calculated by measuring the position coordinates of points on two relatively set boundaries in the width direction of the battery under test, and then based on the distance between the reference edges on the Y-axis. Specifically, by measuring the coordinates of point d and point m, and knowing the length of S4, the width dimension of the left side of the battery can be easily obtained. Similarly, by measuring the coordinates of point e, point l, and the length of S2, the width dimension of the right side of the battery can be quickly obtained.

[0060] 3. The dimension of the battery without tabs and the dimension of the battery with tabs can be calculated by measuring the position coordinates of points on two relatively set boundaries in the corresponding length direction of the battery under test, and then based on the distance between the reference edges on the X-axis. Specifically, for the dimension of the battery without tabs, by measuring the coordinates of point a and point h, and knowing the length of S1, the length dimension of the battery can be easily obtained. Or by measuring the coordinates of point i and point q, and knowing the length of S3, the length dimension of the battery can be easily obtained. For the dimension of the battery with tabs, by measuring the coordinates of point u and point v, and knowing the length of S1, the length dimension of the battery can be easily obtained.

[0061] In step S4, it also includes debugging the parameters of the light source and the CCD camera to make the image of the battery under test clear and accurate, and the contrast between black and white images is obvious.

[0062] S5. Calibrate the CCD measurement system using a high-precision gauge block. After the rectangular coordinate system is established, it is necessary to calibrate the scale of the optical ruler on the CCD image using a gauge block with a known size to establish a functional relationship between the actual size and the size represented by a unit pixel on the image; in step S5, use a high-precision gauge block to repeatedly calibrate the coordinate system scale to improve the accuracy of the measurement system. See Figure 3 Taking the A-angle rectangular coordinate system as an example, the specific operation is as follows:

[0063] 1. When the battery is in the position of battery A, use gauge block K1 to calibrate the scale in the X-axis direction and use gauge block K2 to calibrate the scale in the Y-axis direction;

[0064] 2. When the battery is in the position of battery B, use gauge block K3 to calibrate the scale in the X-axis direction and use gauge block K4 to calibrate the scale in the Y-axis direction;

[0065] 3. When the battery is in the position of battery C, use gauge block K5 to calibrate the scale in the X-axis direction and use gauge block K6 to calibrate the scale in the Y-axis direction;

[0066] 4. And so on. After repeatedly calibrating with a sufficient number of gauge blocks, the scale of the rectangular coordinate system on the CCD measurement system will be more accurate, and the measured size value will be closer to the true value.

[0067] After calibrating the scale of the rectangular coordinate system in the S6, CCD measurement system, a measurement quadrant interface will be formed. Refer to Figure 4 , taking the A-angle rectangular coordinate system as an example, the CCD camera takes pictures of the battery under test to generate black and white images. The CCD vision software captures the image contour and selects measurement points a, b, c, and d. The above measurement points quickly obtain the point coordinates on the rectangular coordinate system, and then the coordinates of each measurement point are imported into a preset formula to obtain the required size data of each battery.

[0068] Refer to Figure 5 、 Figure 6 , the measured data of the corner cut size length and width of the battery under test obtained by the present invention show that the CMKs are CMK = 2.26 and 2.52 respectively, both meeting the technical requirement of being greater than 1.67. The offset coefficients K are 0.0408 and 0.0371, and the standard deviations are 0.0531 and 0.0478. It can be seen that the CMK index of the battery appearance size measurement > 1.67, the size measurement system MSA is qualified, the battery size measurement values are continuous, and there is a small deviation between the measurement values and the actual values, greatly improving the measurement accuracy.

[0069] The present invention replaces the original test bench with a test bench with high-precision dimensions and a positioning reference edge, replaces the original size standard block with a high-precision gauge commonly used in laboratory metrology, establishes a rectangular coordinate system at the four corners of the battery, maps the battery CCD image to the coordinate system, and then the CCD measurement software captures each measurement point of the battery. The various size data of the battery are quickly calculated through the rectangular coordinate system. In this way, the CCD vision measurement system has a test reference, and then the high-precision gauge is used to calibrate the CCD optical scale to establish a high-precision measurement coordinate system. The distance between each coordinate system is measured in advance, and various size data on the battery are calculated through software, improving the measurement accuracy and completely solving the problems that the traditional CCD vision measurement system overly relies on the high processing accuracy of the size standard block and the high positioning accuracy of the battery on the test bench. When the size of the produced product changes, there is no need to make a standard block corresponding to the size, but only a gauge corresponding to the size needs to be used for calibration. Of course, the gauges used in the laboratory are a complete set, including various common size specifications; the servo module is used to drive the CCD camera to move above the four corners of the battery in turn to take pictures to collect images for CCD vision measurement. This method can reduce the original 2 CCD cameras to 1 camera, saving the equipment procurement cost. By using a test bench with high production accuracy and a positioning reference edge to establish a rectangular coordinate system on the CCD vision measurement software, and mapping each measurement point of the battery image to the coordinate system, the battery size measurement becomes very intuitive; with the rectangular coordinate system, it is convenient, fast, and accurate to collect the plane coordinates of each measurement point, and the number of measured points can be freely increased, making the battery size measurement flexible and efficient.

Claims

1. A method for measuring the size of a battery using a CCD vision system, the specific steps are as follows: S1. Build a CCD vision measurement system; S2. Accurately measure the distances between the reference edges and the reference origin points on the test bench; S3. Debug the servo motion program so that the CCD camera passes directly above the right-angle coordinate systems 1 / 2 / 3 / 4 on the test bench in sequence, and 4 measured point rectangular coordinate windows are generated on the test software respectively; S4. Place the battery to be measured on the test bench, establish 4 right-angle coordinate systems on the CCD measurement software through the reference edges P1 to P8 and the reference origin points O1 to O4, obtain the size data of the battery to be measured through the above point coordinates, and obtain the corresponding preset formula; S5. Calibrate the CCD measurement system using a high-precision gauge block. After the right-angle coordinate system is established, it is necessary to calibrate the scale of the optical ruler on the CCD image through the gauge block with a known size, and establish a functional relationship between the actual size and the size represented by a single pixel on the image; S6. After the CCD measurement system calibrates the scale of the right-angle coordinate system, a measurement quadrant interface will be formed. The CCD camera takes a photo of the battery to be measured to generate a black-and-white image. The CCD vision software captures the image contour, selects the corresponding measurement points on the black-and-white image, and quickly obtains the point coordinates of the corresponding measurement points on the right-angle coordinate system. Then, import the point coordinates of each measurement point into the preset formula to obtain the size data of each required battery size.

2. A method for measuring the size of a battery using a CCD vision, according to claim 1, characterized in that: The hardware building steps of the CCD vision measurement system in step S1 are as follows: S11. A servo motion system that drives the CCD camera to move, so that the CCD camera is located above the test bench; S12. The test bench is made of a flat high-transparency glass plate, with measurement reference edges and reference origin points for CCD vision positioning at the four corners, and a battery to be measured with tabs; S13. A light source is set below the test bench; S14. The CCD camera is connected to a CCD controller through a data cable for storing the collected battery size data; S15. The CCD controller is connected to a working computer through a communication cable. The working computer is equipped with CCD vision measurement software for calibrating the size of the right-angle coordinate system and image analysis using a high-precision gauge block.

3. A method for measuring the size of a battery using a CCD vision, according to claim 2, characterized in that: The servo motion system in step S11 includes an X-axis direction control system composed of an X-axis servo motor, an X-axis coupling, and an X-axis servo module, and a Y-axis direction control system composed of a Y-axis servo motor, a Y-axis coupling, and a Y-axis servo module. The X-axis direction control system and the Y-axis direction control system together form a planar motion control system.

4. A method for measuring the size of a battery using a CCD vision, according to claim 2, characterized in that: The color of the reference edge in step S12 is black.

5. A method for measuring the size of a battery using a CCD vision, as claimed in claim 1, wherein: Step S4 also includes debugging the light source and CCD camera parameters to make the image of the battery to be photographed clear and accurate, and the contrast between the black-and-white images is obvious.

6. A method for measuring the size of a battery using CCD vision according to claim 1, characterized in that: The sizes of the battery to be measured in step S4 include: the corner cut sizes of the 4 corner-cut batteries, the battery width size, the length size of the battery without tabs, and the length size of the battery with tabs.

7. A method for measuring the size of a battery using a CCD vision, according to claim 6, characterized in that: The corner cut size of each corner-cut battery can obtain the length and width sizes of the cut-off part of the corner cut through the coordinate difference between the point coordinates at both ends.

8. A method for measuring the size of a battery using CCD vision according to claim 6, characterized in that: The battery width dimension can be obtained by measuring the point coordinates of points on two relatively arranged boundaries in the width direction of the battery under test, and then calculating according to the distance between the reference edges on the Y-axis.

9. A method for measuring the size of a battery using a CCD vision, according to claim 6, characterized in that: The length dimension of the battery without tabs and the length dimension of the battery with tabs can be obtained by measuring the point coordinates of points on two relatively arranged boundaries in the corresponding length direction of the battery under test, and then calculating according to the distance between the reference edges on the X-axis.

10. A method for measuring the size of a battery using CCD vision according to claim 1, characterized in that: In step S5, a high-precision gauge block is used to calibrate the coordinate system scale repeatedly.

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