Thickness testing method for large-scale production of lithium battery diaphragm

Abstract

The invention relates to the technical field of thickness testing, in particular to a thickness testing method for large-scale production of lithium battery diaphragms. The method comprises the following steps: determining a standard characteristic difference degree by analyzing thickness fluctuation characteristics in a CD direction in a historical lithium battery diaphragm thickness detection process; analyzing the thickness non-uniformity degree in the CD direction and the MD direction in the detection process before the rotation speed of the feeding screw is adjusted, combining the adjustment degree of the rotation speed of the feeding screw, analyzing the effective condition of each adjustment, and further screening out reference adjustment; and finally, adjusting and judging according to the difference between the thickness condition in the current test and the standard characteristic, and carrying out real-time adjustment circulation according to the reference adjustment condition to carry out thickness test. According to the invention, more reliable real-time adjustment is realized by combining the thickness detection condition in the multi-advance direction with the correlation analysis of rotating speed adjustment and thickness, so that a complete thickness test circulation system of'detection-analysis-control-re-detection 'in the thickness test process is met.

Description

Technical Field

[0001] This invention relates to the field of thickness testing technology, and more specifically to a thickness testing method for the mass production of lithium battery separators. Background Technology

[0002] The separator in a lithium-ion battery is one of the key internal components. It separates the positive and negative electrodes, preventing short circuits caused by contact between them, while allowing lithium ions to pass through. It directly impacts the battery's capacity, cycle life, and safety performance. Large-scale production places higher demands on thickness testing.

[0003] To ensure the stability of diaphragm thickness, online thickness gauges are typically installed on production lines to monitor the uniformity of diaphragm thickness. The online thickness gauge works by converting the attenuation of X-rays after passing through the diaphragm into diaphragm thickness; therefore, accuracy and stability must be guaranteed during the measurement process. However, existing thickness monitoring systems lack deep integration with process control systems, resulting in the inability to translate thickness measurement data into real-time process parameter adjustment commands. Furthermore, traditional adjustment mechanisms fail to consider multi-stability fluctuations in the CD and MD directions, making it easy for local parameter adjustments to trigger systemic thickness imbalances. This restricts the ability to consistently ensure thickness uniformity and makes it difficult to form a complete cyclical thickness measurement system of "detection-analysis-control-re-detection". Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a thickness testing method for the large-scale production of lithium battery separators, the specific technical solution of which is as follows: This invention provides a thickness testing method for the large-scale production of lithium battery separators, the method comprising: Obtain the different thickness distribution curves in the CD direction and the continuous thickness curves in the MD direction in each historical thickness detection, as well as the feed screw speed; In thickness detection without adjusting the screw speed, standard characteristic difference index is obtained by combining the degree of difference in thickness value distribution between different thickness distribution curves for each thickness detection. In each thickness detection when the screw speed of the feeder changes, the thickness non-uniformity of each adjustment is obtained by considering the degree of difference in thickness values ​​between different thickness distribution curves before each adjustment and the deviation from the standard characteristic difference index, combined with the degree of difference between the continuous thickness curves before each adjustment and all continuous thickness curves in the thickness detection when the screw speed of the feeder is not adjusted. Based on the screw speed change and thickness non-uniformity of each adjustment, the effectiveness of each adjustment is analyzed. Combined with the number of times the adjustment occurs in the thickness detection at the adjustment location, a reference adjustment is selected from all adjustments. Based on the deviation between the thickness distribution differences of different thickness distribution curves in the current thickness test and the standard characteristic difference index, the current feeding screw speed is adjusted according to the adjustment of the reference adjustment, and the thickness test is repeated.

[0005] Furthermore, the method for obtaining the standard feature difference index includes: For any thickness measurement when the screw speed is not adjusted, the mean of the absolute values ​​of all slopes on each thickness distribution curve is taken as the fluctuation stability characteristic of each thickness distribution curve; the mean of all thickness values ​​on each thickness distribution curve is taken as the thickness characteristic of each thickness distribution curve. The fluctuation stability feature and the thickness feature of each thickness distribution curve are combined into a binary pair, which is taken as the feature group of each thickness distribution curve. After analyzing the difference of the feature group between each two adjacent thickness distribution curves in time series, the mean of all differences is taken as the thickness fluctuation difference degree of the thickness detection. The average thickness fluctuation difference of all thickness tests without adjusting the screw speed is used as the standard characteristic difference index.

[0006] Furthermore, the method for obtaining the thickness non-uniformity includes: For any thickness detection where the screw speed of the feeder changes, each adjustment in the thickness detection is taken as an analysis adjustment; based on the difference between the fluctuation difference of the analysis adjustment and the standard characteristic difference index, the instability of the analysis adjustment in the CD direction is obtained. By combining the degree of difference between the continuous thickness curve obtained from the analysis and adjustment and the continuous thickness curve obtained from the thickness detection when the speed of each feeding screw is not adjusted, the instability of the analysis and adjustment in the MD direction is obtained. By combining the analysis and adjustment of instability in the CD direction and instability in the MD direction, the thickness non-uniformity of the analysis and adjustment is obtained.

[0007] Furthermore, the method for obtaining the instability in the CD direction through analysis includes: The mean of the absolute values ​​of all slopes and the mean of the thickness values ​​on each thickness distribution curve before analysis and adjustment are combined into a pair to obtain the characteristic pair. After calculating the difference between the characteristic pairs of adjacent thickness distribution curves before analysis and adjustment, the mean of the difference is used as the fluctuation difference index of analysis and adjustment. The difference between the fluctuation difference index of the analysis regulation and the standard characteristic difference index is used as the instability of the analysis regulation in the CD direction.

[0008] Furthermore, the method for obtaining the instability in the MD direction through analysis includes: For any continuous thickness curve in thickness detection when the screw speed of the feeder is not adjusted, calculate the Euclidean distance between the continuous thickness curve and the continuous thickness curve before analysis and adjustment, and use it as the degree of difference between the analysis and adjustment and the continuous thickness curve. The average value of the difference between all continuous thickness curves in the thickness detection when the analysis and adjustment are not adjusted and the screw speed of the feed is not adjusted is taken as the instability of the analysis and adjustment in the MD direction.

[0009] Furthermore, the method for obtaining the adjustment effectiveness includes: The difference in screw speed before and after each adjustment is taken as the speed change degree of each adjustment; the product of the speed change degree and thickness unevenness of each adjustment is taken as the correlation performance degree of each adjustment. Arrange all adjustments in descending order of correlation performance to obtain the first adjustment sequence; arrange all adjustments in descending order of thickness non-uniformity to obtain the second adjustment sequence. For any given adjustment, the adjustment is negatively correlated with the difference in sequence number between the first and second adjustment sequences to obtain the adjustment effectiveness.

[0010] Furthermore, the method for obtaining the reference adjustment includes: In thickness detection where the screw speed of the feeder changes, the average number of adjustments in the thickness detection is calculated as the average adjustment number; the ratio of the number of adjustments in the thickness detection at each adjustment point to the average adjustment number is negatively correlated to obtain the reference degree for each adjustment. The product of the reference degree and the adjustment effectiveness is used as the optimization degree for each adjustment; the adjustment with the highest optimization degree among all adjustments is used as the reference adjustment.

[0011] Furthermore, adjusting the current feeding screw speed based on the deviation between the thickness distribution differences of different thickness distribution curves in the current thickness detection and the standard characteristic difference index, according to the adjustment of the reference adjustment, includes: Before the current moment of the current thickness detection, the mean of the absolute values ​​of all slopes on each thickness distribution curve and the mean of the thickness value are combined into a pair. After calculating the difference between the pairs of temporally adjacent thickness distribution curves before the current moment, the mean of the difference is used as the current fluctuation index. When the volatility index is greater than the standard characteristic difference index, the current time is recorded as the adjustment time; based on the adjustment of the volatility index at the adjustment time and the adjustment of the reference adjustment, the current degree of adjustment is obtained; The sum of the feed screw speed at the adjustment time and the current adjustment degree is taken as the feed screw speed after adjustment at the adjustment time.

[0012] Furthermore, the method for obtaining the current adjustment degree includes: Obtain the fluctuation difference index of the reference adjustment; take the ratio of the current fluctuation index to the fluctuation difference index of the reference adjustment as the adjustment stability; take the difference in screw speed before and after the reference adjustment as the reference adjustment degree. The current regulation is the product of the regulation stability and the reference regulation.

[0013] Furthermore, the method for obtaining the thickness fluctuation difference includes: calculating the difference of the feature group between every two adjacent thickness distribution curves in the time series using Euclidean distance, and then taking the mean of all Euclidean distances in the time series as the thickness fluctuation difference.

[0014] The present invention has the following beneficial effects: This invention analyzes the fluctuation characteristics of different thickness curves distributed in the CD and MD directions during historical lithium battery separator thickness testing. It measures the degree of difference in standard characteristics determined by the fluctuation characteristics in the CD direction without screw speed adjustment, serving as a data basis for thickness stability unaffected by process variations and providing a foundation for subsequent instability analysis. Then, by analyzing the thickness non-uniformity in the CD and MD directions during testing before screw speed adjustment, and combining this with the degree of screw speed adjustment, the effectiveness of each speed adjustment is analyzed. Through correlation analysis between thickness uniformity and speed adjustment, the most valuable adjustment is selected from all adjustments, providing a better reference for subsequent adjustments. Finally, adjustment judgment is made based on the difference between the current thickness and the standard characteristics. Real-time adjustments can be made based on the reference adjustment, resulting in a more ideal adjustment process for thickness testing. This invention achieves more reliable real-time adjustment by combining thickness detection data in multiple directions with correlation analysis between speed adjustment and thickness, thus fulfilling a complete thickness testing cycle system of "detection-analysis-control-re-detection" in the thickness testing process. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating a thickness testing method for the mass production of lithium battery separators according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a configuration structure for lithium battery separator thickness detection provided in one embodiment of the present invention; Figure 3A schematic diagram of the thickness distribution curve on a lithium battery separator provided in one embodiment of the present invention; Figure 4 This is a flowchart illustrating a method for obtaining thickness non-uniformity according to an embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a thickness testing method for the large-scale production of lithium battery separators according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details a specific scheme for a thickness testing method for the mass production of lithium battery separators provided by this invention.

[0020] A scanning frame is installed at a key location in the production process. The scanning frame is equipped with an online thickness gauge, such as a laser or X-ray transducer, and performs multiple scans along the diaphragm width direction (CD direction) and longitudinal thickness direction (MD direction). The CD direction is the cross-section perpendicular to the material movement direction, and the MD direction is the longitudinal section parallel to the movement direction, acquiring thickness data. In this embodiment, the scanning frame measures every 20-50 mm. Please refer to [link to relevant documentation]. Figure 2 The diagram illustrates a configuration structure for lithium battery separator thickness detection according to an embodiment of the present invention.

[0021] After the separator is extruded, a base film scanning frame obtains the thickness of the separator in its uncoated state through preliminary scanning. Then, after the separator is coated, the thickness of the coated separator is obtained again through the scanning frame. In the mass production of lithium-ion battery separators, the thickness of the separator is adjusted by regulating the speed of the feeding screw, thereby achieving cyclical control of thickness testing during the mass production of lithium-ion battery separators.

[0022] For more reliable thickness test cycle control, please refer to [link / reference]. Figure 1 The diagram illustrates a thickness testing method for the mass production of lithium battery separators according to an embodiment of the present invention. The method includes the following steps: S1: Obtain the different thickness distribution curves in the CD direction and the continuous thickness curve in the MD direction in each historical thickness detection, as well as the feed screw speed.

[0023] In this embodiment, the historical thickness detection process is extracted. During each detection process, multiple thickness distribution curves in the CD direction and one continuous thickness curve in the MD direction can be obtained. When the thickness is uneven, manual experience is required to adjust production parameters, such as the screw speed. To analyze the changes in adjustment later, the screw speed is obtained, and the adjustment of the screw speed reflects the adjustment of production parameters.

[0024] S2: In thickness detection without adjusting the screw speed, the standard characteristic difference index is obtained by combining the degree of difference in thickness value distribution between different thickness distribution curves for each thickness detection.

[0025] First, we analyze the thickness detection when there is no adjustment in the feeding screw speed. This indicates stable production parameters. Through this type of thickness detection analysis, we can obtain the thickness fluctuation under normal and stable production, providing a data basis for subsequent thickness analysis during adjustments. Since the thickness in the CD direction is more immediate—for example, when the extruder die is clogged or the air knife cooling is uneven—it will immediately manifest as a sudden change in thickness in the width direction. In contrast, the thickness in the MD direction drifts slowly, such as with gradual changes in raw material viscosity, typically taking several minutes to become apparent. Therefore, we consider the direct correlation between feeding screw speed adjustment and the CD direction. By analyzing the degree of difference in thickness values ​​between different thickness distribution curves in the CD direction, we obtain a standard characteristic difference index.

[0026] Preferably, in this embodiment of the invention, the method for obtaining the standard feature difference index includes: For any thickness measurement when the screw speed is not adjusted, the mean of the absolute values ​​of all slopes on each thickness distribution curve is used as the fluctuation stability characteristic of each thickness distribution curve, with the slope reflecting the stability of the fluctuation. The mean of all thickness values ​​on each thickness distribution curve is normalized and used as the thickness characteristic of each thickness distribution curve, reflecting the thickness value characteristics on the curve. It should be noted that normalization is a technique well-known to those skilled in the art. Normalization removes the influence of dimensions on subsequent calculations. The choice of normalization can be linear normalization or standard normalization, etc., and the specific normalization method is not limited here.

[0027] Furthermore, the binary combination of the fluctuation stability characteristic and the thickness characteristic of each thickness distribution curve is used as the feature set of each thickness distribution curve, reflecting the overall characteristics of each thickness distribution curve. Since the thickness distribution curves were obtained in chronological order, please refer to [link to relevant documentation]. Figure 3 The diagram illustrates a thickness distribution curve on a lithium battery separator according to an embodiment of the present invention, with each dashed line representing the location of each available thickness distribution curve.

[0028] Therefore, after analyzing the differences in characteristic groups between every two adjacent thickness distribution curves in the time series, the average of all differences is used as the thickness fluctuation difference degree of the thickness detection. The characteristic differences are analyzed by the adjacent order of the time series. In this embodiment of the invention, the thickness fluctuation difference degree is calculated using Euclidean distance to determine the differences in characteristic groups between every two adjacent thickness distribution curves in the time series. The average of all Euclidean distances in the time series is used as the thickness fluctuation difference degree. The larger the Euclidean distance, the more significant the difference. It should be noted that the method for obtaining the Euclidean distance is a numerical technique used by those skilled in the art, and will not be elaborated or limited here.

[0029] Ultimately, the average thickness fluctuation difference of all thickness measurements without adjusting the screw speed is used as the standard characteristic difference index, reflecting the acceptable fluctuation under normal, unadjusted production conditions. The greater the thickness fluctuation exceeds this index, the more necessary adjustment is needed in the production process.

[0030] S3: In each thickness detection when the feeding screw speed changes, the thickness non-uniformity for each adjustment is obtained by considering the degree of difference in thickness values ​​between different thickness distribution curves before each adjustment and the deviation from the standard characteristic difference index, combined with the degree of difference between the continuous thickness curves before each adjustment and all continuous thickness curves in the thickness detection when the feeding screw speed is not adjusted.

[0031] Thickness testing during process parameter adjustments indicates significant thickness fluctuations, necessitating further adjustments before production and testing resumes. Therefore, analyzing the thickness distribution before each adjustment yields thickness non-uniformity, characterizing the instability before adjustment, providing a data foundation for evaluating the adjustment effect.

[0032] Combining deviations across multiple dimensions to reflect thickness instability, preferably, in this embodiment of the invention, the method for obtaining thickness non-uniformity is described in [reference needed]. Figure 4 The diagram illustrates a flowchart of a method for obtaining thickness non-uniformity according to an embodiment of the present invention, the method comprising the following steps: S301: For any thickness detection where the feed screw speed changes, each adjustment in the thickness detection is taken as an analysis adjustment; based on the difference between the fluctuation difference of the analysis adjustment and the standard characteristic difference index, the instability of the analysis adjustment in the CD direction is obtained.

[0033] In the CD direction, the degree of instability can be directly analyzed using standard characteristic difference indicators. When comparing with standard characteristic difference indicators, the method for obtaining thickness fluctuation difference in step S2 can be used. In this embodiment of the invention, the mean of the absolute values ​​of all slopes and the mean of thickness values ​​on each thickness distribution curve before analysis and adjustment are normalized to form a binary tuple, which is used to obtain a characteristic binary tuple. After calculating the difference between the characteristic binary tuples of temporally adjacent thickness distribution curves before analysis and adjustment, the mean of the difference is used as the fluctuation difference indicator for analysis and adjustment.

[0034] By analyzing the fluctuation stability characteristics and thickness value characteristics of the thickness distribution curve before adjustment, a binary tuple is formed. That is, the binary tuple is formed by normalizing the mean of the absolute value of the slope and the mean of the thickness value. Similarly, the difference between the binary tuples can be analyzed by Euclidean distance and the mean can be calculated to obtain the fluctuation difference index, which characterizes the thickness fluctuation.

[0035] The difference between the fluctuation difference index of the analysis and adjustment and the standard characteristic difference index is then used as the instability of the analysis and adjustment in the CD direction. The higher the deviation, the more unstable the thickness detection result in the CD direction before this adjustment.

[0036] S302: By combining the degree of difference between the continuous thickness curve of the analysis and adjustment and the continuous thickness curve of the thickness detection when the speed of each feeding screw is not adjusted, the instability of the analysis and adjustment in the MD direction is obtained.

[0037] Considering the degree of thickness fluctuation in the MD direction, in this embodiment of the invention, for any continuous thickness curve in the thickness detection when the feeding screw speed is not adjusted, the Euclidean distance between the continuous thickness curve and the continuous thickness curve before the adjustment is calculated as the degree of difference between the adjustment and the continuous thickness curve. The deviation between the continuous thickness curve and the continuous thickness curve without parameter adjustment is directly analyzed. The larger the Euclidean distance, the higher the degree of difference.

[0038] Furthermore, the average value of the difference between all continuous thickness curves in the thickness detection under both the analysis adjustment and the unadjusted screw speed is used as the instability of the analysis adjustment in the MD direction. By combining the difference values ​​under all unadjusted conditions, the instability in the MD direction is obtained comprehensively.

[0039] S303: By combining the analysis and adjustment of the instability in the CD direction and the instability in the MD direction, the thickness non-uniformity of the analysis and adjustment is obtained.

[0040] Finally, by combining the instabilities in both directions, the uneven fluctuation of the thickness during each adjustment is obtained. In this embodiment of the invention, the average of the instabilities in the CD direction and the MD direction is calculated to obtain the thickness unevenness of the adjustment.

[0041] S4: Based on the screw speed change and thickness non-uniformity of each adjustment, analyze the effectiveness of each adjustment, and select a reference adjustment from all adjustments by combining the number of times the adjustment occurs in the thickness detection.

[0042] By combining the changes in rotational speed during each adjustment to reflect the degree of adjustment, and through joint analysis of rotational speed adjustment and thickness non-uniformity, the effectiveness of the adjustment is reflected. In this embodiment of the invention, the method for obtaining the effectiveness of the adjustment includes: The difference in screw speed before and after each adjustment is normalized and used as the speed change degree for each adjustment, representing the degree of adjustment. The product of the speed change degree and the thickness non-uniformity for each adjustment is used as the correlation performance degree for each adjustment. When the speed change degree is larger and the corresponding thickness non-uniformity is higher, it indicates that the direct correlation between the adjustment and the thickness non-uniformity is stronger, and the participation of the adjustment degree is higher.

[0043] Then, all the moderating states are arranged in descending order of correlation performance to obtain the first moderating sequence. All the moderating states are arranged in descending order of thickness non-uniformity to obtain the second moderating sequence. The sequence order reflects the degree of consistency between the moderating participation and the thickness non-uniformity. The more consistent the order between the two sequences, the more consistent the moderating correlation with the thickness non-uniformity, and the higher the moderating effectiveness.

[0044] Therefore, for any adjustment, a negative correlation mapping is performed on the difference in the sequence numbers between the first and second adjustment sequences to obtain the adjustment effectiveness. The smaller the difference, the higher the effectiveness. It should be noted that negative correlation mapping is a technique well-known to those skilled in the art, and can be in an inverse proportional form or a negative exponential form, etc., without limitation or elaboration here.

[0045] Since multiple adjustments are made during thickness measurement, the more adjustments are made, the lower the reference value of the adjustments in the thickness measurement becomes. Therefore, combining the number of adjustments in thickness measurement yields a more reliable adjustment. In this embodiment of the invention, the method for obtaining the reference adjustment includes: In thickness detection where the screw speed of the feeding device changes, the average number of adjustments observed in the thickness detection is calculated as the average adjustment number, representing the degree to which adjustments occur on average in thickness detection where adjustments occur. Furthermore, a negative correlation is established between the ratio of the number of adjustments observed in each thickness detection and the average adjustment number to obtain the reference value for each adjustment. The smaller the relative proportion of the number of occurrences, the more reliable the adjustment and the stronger the reference value.

[0046] Therefore, combining the effectiveness, the product of the reference degree and the adjustment effectiveness is used as the optimization degree for each adjustment. The higher the optimization degree, the more reliable the adjustment. The adjustment with the highest optimization degree among all adjustments is used as the reference adjustment. The reference adjustment provides the optimal adjustment reference for the current situation requiring adjustment, making the cycle of thickness detection and process adjustment more efficient.

[0047] S5: Based on the deviation between the thickness distribution differences of different thickness distribution curves in the current thickness test and the standard characteristic difference index, adjust the current feeding screw speed according to the adjustment of the reference adjustment, and then re-perform the thickness test.

[0048] First, based on the current detection fluctuation, it is determined whether adjustment is needed. The need for adjustment is promptly determined by the standard feature difference index. In this embodiment of the invention, before the current moment of the current thickness detection, the mean of the absolute values ​​of all slopes and the mean of thickness values ​​on each thickness distribution curve are normalized to form a tuple. After calculating the difference between the tuples of adjacent thickness distribution curves before the current moment, the mean of the difference is used as the current fluctuation index. According to the method for obtaining the thickness fluctuation difference in step S2, the features of each thickness distribution curve before the current moment are obtained and formed into a tuple. The difference between the tuples of two adjacent thickness distribution curves in time sequence is analyzed to obtain the fluctuation index reflecting the current thickness detection fluctuation.

[0049] When the volatility index exceeds the standard characteristic difference index, it indicates a high degree of instability in the current volatility, requiring adjustment. This current moment is recorded as the adjustment moment. Reference adjustment provides a reference for the current adjustment situation. Based on the volatility index at the adjustment moment and the adjustment status of the reference adjustment, the current degree of adjustment is obtained.

[0050] In this embodiment of the invention, a fluctuation difference index of the reference adjustment is obtained. Based on the process of obtaining the fluctuation difference index for each adjustment in step S301, the fluctuation difference index of the reference adjustment is obtained, reflecting the fluctuation status of the reference adjustment. The ratio of the current fluctuation index to the fluctuation difference index of the reference adjustment is used as the adjustment stability. The higher the current fluctuation level relative to the fluctuation level of the reference adjustment, the higher the degree of speed adjustment is required.

[0051] Therefore, the difference in screw speed before and after the reference adjustment is used as the reference adjustment degree to reflect the reference adjustment degree. Combined with the adjustment stability, the product of the adjustment stability and the reference adjustment degree is used as the current adjustment degree, which represents the optimal adjustment degree based on the reference situation at the current adjustment time.

[0052] Finally, the sum of the feed screw speed at the adjustment time and the current adjustment degree is used as the feed screw speed after adjustment. By adjusting the speed, thickness detection continues, realizing an automatic cycle from detection to control without manual intervention, greatly improving efficiency and response speed, and meeting the complete cycle system of "detection-analysis-control-re-detection" in the thickness testing process.

[0053] In summary, this invention analyzes the fluctuation characteristics of different thickness curves distributed in the CD and MD directions during historical lithium battery separator thickness testing. It measures the degree of difference in standard characteristics determined by the fluctuation characteristics in the CD direction without screw speed adjustment, serving as a data basis for subsequent instability analysis of thickness unaffected by the process. Then, by analyzing the degree of thickness non-uniformity in the CD and MD directions during the testing process before screw speed adjustment, and combining this with the degree of screw speed adjustment, the effectiveness of each speed adjustment is analyzed. Through correlation analysis between thickness uniformity and speed adjustment, the most valuable adjustment is selected from all adjustments, providing a better reference for subsequent adjustments. Finally, adjustment judgment is made based on the difference between the current thickness and the standard characteristics. During adjustment, real-time adjustments can be made based on the reference adjustment, resulting in a more ideal adjustment process for thickness testing. This invention achieves more reliable real-time adjustment by combining thickness detection data in multiple directions with correlation analysis of speed adjustment and thickness, thus satisfying a complete thickness testing cycle system of "detection-analysis-control-re-detection" in the thickness testing process.

[0054] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0055] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for thickness testing in the mass production of lithium battery separators, characterized in that, The method includes: Obtain the different thickness distribution curves in the CD direction and the continuous thickness curves in the MD direction in each historical thickness detection, as well as the feed screw speed; In thickness detection without adjusting the screw speed, standard characteristic difference index is obtained by combining the degree of difference in thickness value distribution between different thickness distribution curves for each thickness detection. In each thickness detection when the screw speed of the feeder changes, the thickness non-uniformity of each adjustment is obtained by considering the degree of difference in thickness values ​​between different thickness distribution curves before each adjustment and the deviation from the standard characteristic difference index, combined with the degree of difference between the continuous thickness curves before each adjustment and all continuous thickness curves in the thickness detection when the screw speed of the feeder is not adjusted. Based on the screw speed change and thickness non-uniformity of each adjustment, the effectiveness of each adjustment is analyzed. Combined with the number of times the adjustment occurs in the thickness detection at the adjustment location, a reference adjustment is selected from all adjustments. Based on the deviation between the thickness distribution differences of different thickness distribution curves in the current thickness test and the standard characteristic difference index, the current feeding screw speed is adjusted according to the adjustment of the reference adjustment, and the thickness test is repeated.

2. The thickness testing method for the mass production of lithium battery separators according to claim 1, characterized in that, The method for obtaining the standard feature difference index includes: For any thickness measurement when the screw speed is not adjusted, the mean of the absolute values ​​of all slopes on each thickness distribution curve is taken as the fluctuation stability characteristic of each thickness distribution curve; the mean of all thickness values ​​on each thickness distribution curve is taken as the thickness characteristic of each thickness distribution curve. The fluctuation stability feature and the thickness feature of each thickness distribution curve are combined into a binary pair, which is taken as the feature group of each thickness distribution curve. After analyzing the difference of the feature group between each two adjacent thickness distribution curves in time series, the mean of all differences is taken as the thickness fluctuation difference degree of the thickness detection. The average thickness fluctuation difference of all thickness tests without adjusting the screw speed is used as the standard characteristic difference index.

3. The thickness testing method for the mass production of lithium battery separators according to claim 1, characterized in that, The method for obtaining the thickness non-uniformity includes: For any thickness detection where the screw speed of the feeder changes, each adjustment in the thickness detection is taken as an analysis adjustment; based on the difference between the fluctuation difference of the analysis adjustment and the standard characteristic difference index, the instability of the analysis adjustment in the CD direction is obtained. By combining the degree of difference between the continuous thickness curve obtained from the analysis and adjustment and the continuous thickness curve obtained from the thickness detection when the speed of each feeding screw is not adjusted, the instability of the analysis and adjustment in the MD direction is obtained. By combining the analysis and adjustment of instability in the CD direction and instability in the MD direction, the thickness non-uniformity of the analysis and adjustment is obtained.

4. The thickness testing method for the mass production of lithium battery separators according to claim 3, characterized in that, The method for obtaining the instability in the CD direction of the analysis adjustment includes: The mean of the absolute values ​​of all slopes and the mean of the thickness values ​​on each thickness distribution curve before analysis and adjustment are combined into a pair to obtain the characteristic pair. After calculating the difference between the characteristic pairs of adjacent thickness distribution curves before analysis and adjustment, the mean of the difference is used as the fluctuation difference index of analysis and adjustment. The difference between the fluctuation difference index of the analysis regulation and the standard characteristic difference index is used as the instability of the analysis regulation in the CD direction.

5. The thickness testing method for the mass production of lithium battery separators according to claim 3, characterized in that, The method for obtaining the instability in the MD direction of the analysis adjustment includes: For any continuous thickness curve in thickness detection when the screw speed of the feeder is not adjusted, calculate the Euclidean distance between the continuous thickness curve and the continuous thickness curve before analysis and adjustment, and use it as the degree of difference between the analysis and adjustment and the continuous thickness curve. The average value of the difference between all continuous thickness curves in the thickness detection when the analysis and adjustment are not adjusted and the screw speed of the feed is not adjusted is taken as the instability of the analysis and adjustment in the MD direction.

6. The thickness testing method for the mass production of lithium battery separators according to claim 1, characterized in that, The method for obtaining the effectiveness of the regulation includes: The difference in screw speed before and after each adjustment is taken as the speed change degree of each adjustment; the product of the speed change degree and thickness unevenness of each adjustment is taken as the correlation performance degree of each adjustment. Arrange all adjustments in descending order of correlation performance to obtain the first adjustment sequence; arrange all adjustments in descending order of thickness non-uniformity to obtain the second adjustment sequence. For any given adjustment, the adjustment is negatively correlated with the difference in sequence number between the first and second adjustment sequences to obtain the adjustment effectiveness.

7. The thickness testing method for the mass production of lithium battery separators according to claim 1, characterized in that, The method for obtaining the reference adjustment includes: In thickness detection where the screw speed of the feeder changes, the average number of adjustments in the thickness detection is calculated as the average adjustment number; the ratio of the number of adjustments in the thickness detection at each adjustment point to the average adjustment number is negatively correlated to obtain the reference degree for each adjustment. The product of the reference degree and the adjustment effectiveness is used as the optimization degree for each adjustment; the adjustment with the highest optimization degree among all adjustments is used as the reference adjustment.

8. The thickness testing method for the mass production of lithium battery separators according to claim 1, characterized in that, The step of adjusting the current feeding screw speed based on the deviation of the thickness value distribution difference between different thickness distribution curves in the current thickness detection from the standard characteristic difference index, according to the adjustment of the reference adjustment, includes: Before the current moment of the current thickness detection, the mean of the absolute values ​​of all slopes on each thickness distribution curve and the mean of the thickness value are combined into a pair. After calculating the difference between the pairs of temporally adjacent thickness distribution curves before the current moment, the mean of the difference is used as the current fluctuation index. When the volatility index is greater than the standard characteristic difference index, the current time is recorded as the adjustment time; based on the adjustment of the volatility index at the adjustment time and the adjustment of the reference adjustment, the current degree of adjustment is obtained; The sum of the feed screw speed at the adjustment time and the current adjustment degree is taken as the feed screw speed after adjustment at the adjustment time.

9. The thickness testing method for the mass production of lithium battery separators according to claim 8, characterized in that, The method for obtaining the current adjustment degree includes: Obtain the fluctuation difference index of the reference adjustment; take the ratio of the current fluctuation index to the fluctuation difference index of the reference adjustment as the adjustment stability; take the difference in screw speed before and after the reference adjustment as the reference adjustment degree. The current regulation is the product of the regulation stability and the reference regulation.

10. The thickness testing method for the mass production of lithium battery separators according to claim 2, characterized in that, The method for obtaining the thickness fluctuation difference includes: calculating the difference of characteristic groups between every two adjacent thickness distribution curves in the time series using Euclidean distance, and then taking the mean of all Euclidean distances in the time series as the thickness fluctuation difference.

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