Tension control method and system for film coating production line

Abstract

A tension detection and control method and system for a film production line, comprising the following steps: periodically obtaining the real-time moisture content of the paperboard substrate being transported to the moisture content monitoring station to obtain the moisture content distribution data of the paperboard substrate in the paper running direction; determining whether a deviation section deviating from the preset reference moisture content appears on the paperboard substrate according to the moisture content distribution data; and adjusting the tension on the paperboard substrate in the target tension isolation section according to the moisture content distribution data of the paperboard substrate in the target tension isolation section to minimize the material damage caused by the tension difference on the paperboard substrate in the target tension isolation section. Through the above scheme, the irreversible stretching, wrinkling, fiber breakage and other material damage problems caused by the mismatch between the tension and the mechanical properties of the material in the moisture content abnormal section are solved. Ultimately, the present application can significantly improve the quality stability of the film product, make the thickness of the paperboard substrate uniform and the surface smooth, and help improve the bonding quality of the subsequent film or foil.

Description

Technical Field

[0001] This application relates to the field of cold chain product transportation, specifically to a tension detection and control method and system for a film coating production line. Background Technology

[0002] The cigarette packaging cardboard lamination production line is a production line that laminates cardboard substrate with materials such as OPP film, PET film, and aluminum foil. During the lamination process, the cardboard substrate passes sequentially along the paper feeding direction through the unwinding station, adhesive coating station, lamination station, and rewinding station. Appropriate tension must be maintained between each station to ensure smooth feeding of the cardboard substrate and the quality of the lamination. Tension control is a key technical indicator of this production line, directly affecting the flatness of the lamination, dimensional stability, and the final product yield.

[0003] In existing technologies, tension control in laminating production lines mainly employs constant tension control or closed-loop feedback control based on tension sensors. Constant tension control sets a fixed tension value, which is maintained constant by actuators such as drive rollers or floating rollers. Closed-loop feedback control, on the other hand, places tension sensors along the paper feeding path to detect the actual tension in real time and compare it with the set value. PID control algorithms are then used to adjust the actuators, ensuring the actual tension tracks the set value. Furthermore, some production lines utilize segmented independent tension control schemes. This involves setting multiple tension isolation zones along the paper feeding direction, with tension isolation achieved between each zone via active drive rollers or floating rollers. Each zone independently controls its internal tension value, improving the precision of tension control for different sections of the cardboard substrate.

[0004] However, as a cellulose-based material, the mechanical properties of cardboard substrate change significantly with variations in moisture content. During production, factors such as fluctuations in ambient temperature and humidity, batch differences in cardboard, and moisture penetration during the adhesive coating process can cause uneven moisture content distribution along the paper feed direction, potentially resulting in sections with localized moisture content deviations from the normal range. Current tension control processes only focus on stabilizing or tracking the tension value itself, neglecting the impact of moisture content changes on the mechanical properties of the cardboard substrate and failing to differentiate tension adjustments based on the actual moisture content distribution. When abnormal moisture content sections pass through tension control sections, using a uniform tension setting will lead to a mismatch between the actual stress on different parts of the cardboard substrate within that section and its inherent mechanical properties. Some areas may experience irreversible tensile deformation or fiber breakage due to excessive tension, while other areas may exhibit loosening or wrinkling due to insufficient tension. These material damages will further lead to uneven thickness, reduced flatness, warping and deformation of the cardboard substrate after lamination, as well as lamination quality defects such as poor adhesion between the film or foil and the cardboard substrate, resulting in bubbles or delamination, which seriously affect the product qualification rate and production efficiency. Summary of the Invention

[0005] This application provides a method and system for tension detection and control in a film coating production line, which can solve the technical problems existing in the above-mentioned related technologies.

[0006] In a first aspect, embodiments of this application provide a method for tension detection and control in a lamination production line, employing the following technical solution:

[0007] A method for tension detection and control in a film coating production line, comprising the following steps:

[0008] The real-time moisture content of the cardboard substrate being transported to the moisture content monitoring station is periodically acquired to obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction;

[0009] Based on the moisture content distribution data, determine whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset benchmark moisture content;

[0010] If such a deviation zone exists within the target tension isolation zone, the tension on the paperboard substrate within the target tension isolation zone is adjusted based on the moisture content distribution data of the paperboard substrate within the target tension isolation zone, so as to minimize the material damage caused by tension differences to the paperboard substrate within the target tension isolation zone; wherein, the target tension isolation zone is any one of a plurality of tension isolation zones set along the paper feeding direction between the moisture content monitoring station and the lamination station.

[0011] In conjunction with the first aspect, in one embodiment, when the deviation section exists within the target tension isolation section, adjusting the tension on the cardboard substrate within the target tension isolation section based on the moisture content distribution data of the cardboard substrate within the target tension isolation section includes the following steps:

[0012] Based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section, the characteristic type of the target tension isolation section is determined; wherein, the characteristic type includes a steady-state type in which the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type in which the real-time moisture content changes monotonically along the paper feeding direction within a continuous section.

[0013] Based on the characteristic types existing within the target tension isolation section, a corresponding calculation method for calculating the tension set value of the target tension isolation section is determined;

[0014] Based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, the tension setting value is calculated and determined, and the tension of the target tension isolation section is adjusted based on the tension setting value.

[0015] In conjunction with the first aspect, in one embodiment, the step of calculating and determining the tension setpoint based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, and adjusting the tension of the target tension isolation section based on the tension setpoint, includes the following steps:

[0016] If only the steady-state cardboard substrate exists within the target tension isolation zone, the representative moisture content is determined based on the moisture content distribution data of the cardboard substrate within the target tension isolation zone.

[0017] The tension setpoint is calculated and determined based on the representative moisture content.

[0018] In conjunction with the first aspect, in one embodiment, the tension setpoint is calculated and determined based on the representative moisture content using the following calculation formula:

[0019] .

[0020] Wherein, T0 is the reference tension setting value corresponding to the preset reference moisture content ω0;

[0021] ω rep To represent moisture content;

[0022] K is a pre-calibrated tension-moisture content compensation coefficient, which is determined according to the type of material of the cardboard substrate.

[0023] In conjunction with the first aspect, in one embodiment, the step of calculating and determining the tension setpoint based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, and adjusting the tension of the target tension isolation section based on the tension setpoint, includes the following steps:

[0024] If there is a transitional cardboard substrate in the target tension isolation section, the required tension sequence corresponding to each point in the target tension isolation section is determined based on the moisture content distribution data of each point in the cardboard substrate in the target tension isolation section at the current time.

[0025] Based on the required tension sequence and the preset comprehensive impact score model reflecting the overall damage of the cardboard substrate, the tension setting value corresponding to the target tension isolation section at the current moment is solved with the goal of minimizing the total material damage caused by the deviation between the actual tension borne at each point and the required tension.

[0026] In conjunction with the first aspect, in one implementation, the comprehensive influence score model, which reflects the overall damage to the cardboard substrate based on the required tension sequence and a preset comprehensive influence score model, aims to minimize the total material damage caused by the deviation between the actual tension at each point and the required tension. The calculation formula for the comprehensive influence score model in the tension setting value corresponding to the target tension isolation section at the current moment is as follows:

[0027]

[0028] In the formula, T(t) i ) for t i The set value of the target tension isolation section at any given time;

[0029] ΔT i For t i The required tension corresponding to the cardboard substrate point that reaches the end of this section at any given moment;

[0030] w i These are the weighting coefficients;

[0031] f is the damage function, and when When > 0, the first sub-function f1 is used for calculation. When the value is less than 0, the second sub-function f2 is used for calculation to characterize the differential damage characteristics of the cardboard substrate when the tension is too high and the tension is too low.

[0032] In conjunction with the first aspect, in one implementation, the first sub-function f1 is calculated using the following formula:

[0033]

[0034] The second sub-function f2 is calculated using the following formula:

[0035]

[0036] Wherein, δ_rev is the reversible elastic window, representing the maximum tension deviation that the paperboard substrate can fully recover its elastic deformation after unloading;

[0037] δ_irr is the irreversible damage threshold, representing the critical value of tension deviation corresponding to the permanent deformation of the cardboard substrate;

[0038] α1, β1, p1, q1, α2, β2, p2, and q2 are all non-negative constants determined according to the material type of the cardboard substrate, and the penalty coefficients satisfy α1 not less than α2 and β1 not less than β2.

[0039] M1 is the penalty value approaching infinity, and M2 is the penalty value approaching infinity.

[0040] In conjunction with the first aspect, in one implementation, determining the deviation zone based on the moisture content distribution data specifically includes:

[0041] Starting from the moisture content monitoring station, the local average moisture content is calculated using a sliding window along the paper feeding direction;

[0042] When the deviation of the average value of multiple consecutive windows from the preset benchmark moisture content exceeds a set threshold, a deviation segment is determined to have occurred, and the position of the window that first exceeds the first set threshold is recorded as the starting position of the deviation segment.

[0043] Secondly, embodiments of this application provide a tension detection and control system for a laminating production line, employing the following technical solution:

[0044] A tension detection and control system for a laminating production line, comprising:

[0045] A moisture content monitoring module is configured to periodically acquire the real-time moisture content of the cardboard substrate being transported to the moisture content monitoring station, and obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction.

[0046] The judgment module is configured to determine, based on the moisture content distribution data, whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset reference moisture content.

[0047] A tension control module is configured to, if present, adjust the tension on the cardboard substrate within the target tension isolation section based on the moisture content distribution data of the cardboard substrate within the target tension isolation section, so as to minimize the material damage to the cardboard substrate caused by tension differences within the target tension isolation section; wherein the target tension isolation section is any one of a plurality of tension isolation intervals set along the paper feeding direction between the moisture content monitoring station and the lamination station.

[0048] In conjunction with the second aspect, in one embodiment, the tension control module is further configured to determine the characteristic type of the target tension isolation section based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section; wherein, the characteristic type includes a steady-state type in which the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type in which the real-time moisture content monotonically changes along the paper feed direction within a continuous section;

[0049] Based on the characteristic types existing within the target tension isolation section, a corresponding calculation method for calculating the tension set value of the target tension isolation section is determined;

[0050] Based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, the tension setting value is calculated and determined, and the tension of the target tension isolation section is adjusted based on the tension setting value.

[0051] The beneficial effects of the technical solutions provided in this application include:

[0052] This application provides a tension detection and control method and system for a laminating production line. By periodically acquiring the real-time moisture content of the cardboard substrate and constructing moisture content distribution data along the paper feed direction, it achieves online continuous monitoring of the moisture content state of the cardboard substrate. Based on this, it identifies deviation sections where the moisture content deviates from the baseline at multiple consecutive locations based on the moisture content distribution data, thereby accurately locating abnormal areas requiring special tension control. When the deviation section enters the target tension isolation section, the tension setpoint is dynamically adjusted according to the actual moisture content distribution data of the cardboard substrate within that section, with the optimization goal of minimizing material damage caused by tension differences in the cardboard substrate within that section. Compared with existing technologies, this solves the problem of irreversible stretching, wrinkling, fiber breakage, and other material damage caused by the mismatch between tension and material mechanical properties in abnormal moisture content sections. Ultimately, this invention can significantly improve the quality stability of laminated products, making the cardboard substrate thickness uniform and the surface smooth, thus helping to improve the subsequent film or foil lamination quality. Attached Figure Description

[0053] Figure 1 This is a schematic flowchart of an embodiment of the tension detection and control method for the lamination production line of this application;

[0054] Figure 2 This is a functional module diagram of an embodiment of the tension detection and control system for the lamination production line of this application. Detailed Implementation

[0055] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0056] Existing tension control methods in lamination production lines typically employ constant tension, closed-loop feedback, or segmented independent control. However, these methods neglect the impact of variations in the moisture content of the cardboard substrate on its mechanical properties. When the moisture content of the cardboard substrate is unevenly distributed, with localized deviations from the preset range, maintaining a constant tension setting may lead to a mismatch between the stress on different parts of the cardboard substrate and its mechanical properties, resulting in material damage such as tensile deformation, fiber breakage, loosening, or wrinkling. This damage, in turn, affects lamination quality, reducing product yield and production efficiency.

[0057] In response to this problem, this application proposes a tension detection and control method and system for a film coating production line.

[0058] Firstly, referring to Figure 1 This application proposes a method for tension detection and control in a film coating production line, which includes the following steps:

[0059] S100: Periodically acquire the real-time moisture content of the cardboard substrate that is transported to the moisture content monitoring station, and obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction;

[0060] Specifically, a moisture content sensor, such as an infrared spectral sensor or a capacitive sensor, can be installed at the moisture content monitoring station. This sensor is configured to continuously or discretely measure the moisture content of the cardboard substrate at fixed time intervals or fixed distance intervals along the paper feed direction. As a result, a series of real-time moisture content data points are collected, sorted, and stored according to their position in the paper feed direction, thus forming distribution data reflecting the change in moisture content of the cardboard substrate along its length. For example, the moisture content can be measured every 10 centimeters, and these data can be recorded.

[0061] S200. Based on the moisture content distribution data, determine whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset reference moisture content.

[0062] After obtaining the moisture content distribution data, the moisture content value of each measurement point can be compared with a preset reference moisture content. When the absolute deviation of the moisture content at a certain point from the reference moisture content exceeds a preset fixed threshold, that point is marked as having an abnormal moisture content. If several consecutive abnormal points are identified along the paper feed direction, these consecutive abnormal points are determined to constitute a deviation section.

[0063] S300. If the deviation section exists within the target tension isolation section, adjust the tension on the cardboard substrate within the target tension isolation section according to the moisture content distribution data of the cardboard substrate within the target tension isolation section, so as to minimize the material damage caused by the tension difference to the cardboard substrate within the target tension isolation section.

[0064] The target tension isolation section is any one of multiple tension isolation intervals located along the paper feed direction between the moisture content monitoring station and the laminating station. Specifically, a laminating production line typically has one or more independent tension isolation intervals. These intervals are physically isolated by mechanisms such as drive rollers or floating rollers, allowing independent control of the tension in different parts of the production line. The target tension isolation section refers to any one of these independently controllable tension intervals located downstream of the moisture content monitoring station and upstream of the laminating station.

[0065] When a deviation in moisture content is periodically detected within the target tension isolation zone, the tension setting for that zone needs to be corrected. Since the mechanical properties of the cardboard substrate change with moisture content, the tension setting needs to be dynamically adjusted to avoid material damage caused by abnormal moisture content. For example, when the moisture content is high, the cardboard substrate becomes more flexible, and the tension setting can be lowered to avoid overstretching; when the moisture content is low, the material is harder and may become loose and wrinkled due to insufficient tension. Both situations can lead to material damage and a decrease in the quality of the final laminated product. Therefore, this step optimizes the tension so that the cardboard substrate can be stretched with a more suitable tension when passing through this zone, thereby reducing material damage such as tensile deformation, wrinkles, or breakage caused by tension mismatch, and ultimately improving the quality of the final laminated product.

[0066] Furthermore, in some embodiments, step S300, when the deviation section exists within the target tension isolation section, adjusting the tension on the cardboard substrate within the target tension isolation section based on the moisture content distribution data of the cardboard substrate within the target tension isolation section, includes the following steps:

[0067] S310. Based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section, determine the characteristic type of the target tension isolation section; wherein, the characteristic type includes a steady-state type where the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type where the real-time moisture content changes monotonically along the paper feeding direction within a continuous section.

[0068] S320. Based on the characteristic types existing in the target tension isolation section, determine the corresponding calculation method for calculating the tension set value of the target tension isolation section;

[0069] S330. Based on the calculation method and the moisture content distribution data of the cardboard substrate in the target tension isolation section, calculate and determine the tension setting value, and adjust the tension of the target tension isolation section based on the tension setting value.

[0070] Because the moisture content of cardboard substrate is not constant along the paper feed direction during production, deviations in the moisture content distribution typically exhibit two distinct patterns: a steady-state pattern and a transitional pattern. The steady-state pattern occurs when the moisture content at various points within the deviation section roughly stabilizes at a new level, with minimal fluctuations. For example, the overall moisture content of the cardboard decreases from the normal 7.5% to 6.0% and remains stable. The transitional pattern, on the other hand, refers to a continuous, monotonous change (increasing or decreasing) in the moisture content at various points within the deviation section along the paper feed direction. For example, it gradually decreases from 7.5% to 6.0%.

[0071] For steady-state deviation sections, the mechanical properties of each point on the cardboard substrate are basically the same, and only the tension needs to be adjusted to a new constant value to match them. However, for transitional deviation sections, the mechanical properties of each point on the cardboard substrate change continuously along the paper feeding direction, and it is impossible to satisfy all points with a constant tension value at the same time. It is necessary to find an optimal compromise value through optimization algorithms to minimize the total damage to the entire material.

[0072] Therefore, this application further proposes that in step S330, the tension setting value is calculated and determined according to the calculation method and the moisture content distribution data of the cardboard substrate in the target tension isolation section, and the tension of the target tension isolation section is adjusted based on the tension setting value, including the following steps:

[0073] S331. If only the steady-state cardboard substrate exists within the target tension isolation zone, determine the representative moisture content based on the moisture content distribution data of the cardboard substrate within the target tension isolation zone.

[0074] When only a stable cardboard substrate exists within the target tension isolation zone, the moisture content at various points within the zone, while stable, may still exhibit slight random fluctuations. To match the entire material with a uniform tension setpoint, a representative value, ω, representing the moisture content, needs to be extracted from these fluctuation data. rep This is used to characterize the overall moisture content level of this section. ω represents the moisture content. rep There are many methods for determining the mean, such as the arithmetic mean method, the median method, and the weighted average method, and this application does not impose any restrictions on these methods.

[0075] S332. Calculate and determine the tension setting value based on the representative moisture content.

[0076] When calculating the tension setpoint, the cardboard substrate, as a cellulose-based material, exhibits a certain functional relationship between its mechanical properties (such as elastic modulus and tensile strength) and moisture content. Within a small range (e.g., moisture content deviating from the baseline value by no more than 2% to 3%), this relationship can be approximated as linear. Therefore, in this embodiment, the following calculation formula is used to calculate the representative tension setpoint:

[0077] .

[0078] Wherein, T0 is the reference tension setting value corresponding to the preset reference moisture content ω0;

[0079] ωrep represents the moisture content;

[0080] K is a pre-calibrated tension-moisture content compensation coefficient, which is determined according to the material type of the cardboard substrate. Specifically, it can be calibrated experimentally: the minimum damage tension value of the cardboard substrate is measured under different moisture content conditions, and the tension-moisture content linear relationship is obtained by fitting, and its slope is the K value.

[0081] Furthermore, when representing moisture content equal to the reference moisture content When the cardboard substrate is in a standard state, the reference tension T0 should be used. When the representative moisture content is higher than the reference, the material becomes softer and the required tension decreases, so the tension setting should be compensated downward. When the representative moisture content is lower than the reference, the material becomes harder and the required tension increases, so the tension setting should be compensated upward.

[0082] For example, this application provides a method for calibrating the coefficient K:

[0083] A composite experiment was conducted using a certain brand of cigarette packaging cardboard (230g / m² basis weight) and OPP film.

[0084] (1) Preparation of cardboard substrate samples with different moisture contents: The samples were placed in constant temperature and humidity chambers with different humidity for 24 hours to obtain samples with moisture contents of 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5% and 8.0% respectively.

[0085] (2) Perform tensile tests on each sample: determine the stress-strain curve of each sample in the elastic deformation stage, and determine its elastic modulus and yield point.

[0086] (3) Determine the minimum damaging tension for each sample: Apply different levels of tension to the cardboard substrate of each sample and measure the residual strain after unloading. When the residual strain is less than 0.1%, the tension value is considered to minimize material damage. Record the minimum damaging tension value corresponding to each moisture content.

[0087] (4) Fitting the linear relationship: Perform linear regression with moisture content as the abscissa and minimum damage tension as the ordinate. The slope of the regression line is the compensation coefficient K, the moisture content corresponding to the intercept is the reference moisture content ω0, and the minimum damage tension at this moisture content is the reference tension T0.

[0088] Ultimately, the experiment yielded the following results: ω0 = 6.5%, T0 = 70 N, K = -5 N / %. This means that for every 1% increase in moisture content, the tension setting should be reduced by 5 N.

[0089] When a transitional cardboard substrate exists within the target tension isolation zone, meaning the moisture content of the cardboard substrate in this zone exhibits a monotonically increasing or decreasing trend along the paper feed direction, the mechanical properties (such as elastic modulus, tensile strength, and elongation) at each point continuously change, resulting in different ideal tension values ​​(i.e., required tension) at each point. In this scenario, it is impossible to simultaneously meet the needs of all points with a constant tension setting. If simple constant tension control is still used, some points will inevitably be overstretched due to excessive tension, while others will be loose and wrinkled due to insufficient tension, thus causing material damage. Therefore, an optimization method is needed to find a tension setting value that minimizes overall material damage while considering the needs of all points.

[0090] It should also be noted that since the moisture content of the cardboard substrate is a continuously changing physical quantity along the paper feed direction, there must exist a transitional range between the normal moisture content range and the steady-state deviation range, i.e., a transitional range. In other words, as long as a deviation range exists within the target tension isolation range, the type of deviation range within the target tension isolation range can be directly distinguished by the presence or absence of a transitional range.

[0091] Based on the above, further, in some embodiments, step S330, calculating and determining the tension setting value according to the calculation method and the moisture content distribution data of the cardboard substrate in the target tension isolation section, and adjusting the tension of the target tension isolation section based on the tension setting value, further includes the following steps:

[0092] S333. If there is a transitional cardboard substrate in the target tension isolation section, determine the required tension sequence corresponding to each point in the target tension isolation section based on the moisture content distribution data of each point in the cardboard substrate in the target tension isolation section at the current time.

[0093] Demand tension refers to the ideal tension value that minimizes material damage to the cardboard substrate at a given moisture content. The correspondence between demand tension and moisture content can be obtained through prior experimental calibration, for example, by measuring the minimum damage tension of the cardboard substrate at different moisture contents and establishing a moisture content demand tension mapping function or lookup table. Alternatively, it can be calculated using the method described in step S332 above, which is not limited in this application. Thus, the moisture content of each point within the zone is converted into the corresponding demand tension, forming a demand tension sequence arranged along the paper feed direction.

[0094] S334. Based on the required tension sequence and the preset comprehensive influence score model reflecting the overall damage of the cardboard substrate, with the goal of minimizing the total material damage caused by the deviation between the actual tension borne at each point and the required tension, solve for the tension setting value corresponding to the target tension isolation section at the current moment.

[0095] Specifically, the comprehensive influence score model converts tension deviation into material damage values, and obtains the total damage score for that section under the current tension setting by weighted summation of the damage values ​​at all points within the area. The goal of the optimization solution is to find a tension setting that minimizes this total damage score. In this embodiment, the calculation formula for the comprehensive influence score model is as follows:

[0096]

[0097] In the formula, T(t) i ) for t i The set value of the target tension isolation section at any given time;

[0098] ΔT i For t i The required tension corresponding to the cardboard substrate point that reaches the end of this section at any given moment;

[0099] w i These are the weighting coefficients;

[0100] f is the damage function, and when When > 0, the first sub-function f1 is used for calculation. When the value is less than 0, the second sub-function f2 is used for calculation to characterize the differentiated damage characteristics of the cardboard substrate under high and low tension. This is because, under the transitional moisture content distribution scenario, the actual tension setpoint T and the required tension ΔT at each point within the target tension isolation section are different. i There is a deviation T - ΔT i This deviation is the direct cause of damage to the cardboard substrate material. However, the cardboard substrate is more susceptible to damage under excessive tension (T - ΔT). i > 0) and tension is too small (T - ΔT) i< 0) The damage characteristics differ significantly between the two conditions. Specifically, regardless of whether the moisture content of the cardboard substrate is high or low, higher tension is a more dangerous direction: when the moisture content is high, the material softens, and higher tension can lead to excessive stretching and permanent fiber deformation; when the moisture content is low, the material becomes brittle, and higher tension can lead to brittle fracture or even paper breakage. Lower tension, on the other hand, is relatively less harmful, mainly manifesting as loosening, wrinkles, and other appearance defects, and usually does not cause irreversible material damage. Therefore, to accurately quantify the degree of damage caused by tension deviation to the cardboard substrate, this invention designs an asymmetric damage function, using different sub-functions f1 and f2 for calculations of higher and lower tension, respectively.

[0101] The first sub-function f1 is calculated using the following formula:

[0102]

[0103] The second sub-function f2 is calculated using the following formula:

[0104]

[0105] Where, δ rev The reversible elastic window represents the maximum allowable tension deviation for the paperboard substrate to fully recover its elastic deformation after unloading; when the absolute value of the tension deviation does not exceed δ rev At this time, the deformation of the cardboard substrate is purely elastic; the material can fully recover after unloading without permanent damage. δ rev The method for determining δ is as follows: different levels of tension deviation are applied to the cardboard substrate sample and held for a certain period of time before being unloaded. The residual strain is measured, and the maximum tension deviation corresponding to a residual strain of less than 0.1% is taken as δ. rev .

[0106] δ irr The irreversible damage threshold represents the critical value of tension deviation corresponding to permanent deformation of the cardboard substrate; when the absolute value of the tension deviation exceeds δ... irr At this time, the cardboard substrate will undergo irreversible plastic deformation or fiber breakage, causing permanent material damage. irr The method for determining δ is as follows: a tensile test is performed on the cardboard substrate sample to determine its yield point, and the tension deviation corresponding to the yield point is taken as δ. irr .

[0107] M1 is the penalty value approaching infinity, and M2 is the penalty value approaching infinity.

[0108] α1, β1, p1, q1, α2, β2, p2, and q2 are all non-negative constants determined according to the material type of the cardboard substrate, and the penalty coefficients satisfy α1 not less than α2 and β1 not less than β2.

[0109] Where α1 is the damage penalty coefficient in the reversible elastic stage, reflecting the material's sensitivity to excessive tension within the reversible elastic range; p1 is the damage power in the reversible elastic stage, reflecting the nonlinearity of damage as deviation increases; β1 is the damage penalty coefficient in the irreversible damage stage, reflecting the degree of accelerated damage accumulation after the material enters the irreversible damage stage; and q1 is the damage power in the irreversible damage stage. The calibration method for these parameters is as follows: within the reversible elastic window (0 < x ≤ δ... rev ), measured the cumulative damage under different deviations, and fitted a power-law relationship to obtain α1 and p1; within the irreversible damage zone (δ rev <x ≤δ irr The damage accumulation under different excess deviations was measured, and β1 and q1 were obtained by fitting.

[0110] α2, β2, p2, and q2 are parameters of the second sub-function f2. They are all non-negative constants calibrated according to the type of cardboard substrate material. Their physical meaning and calibration method are similar to the corresponding parameters of the first sub-function, but they are calibrated independently to reflect the differences in material damage characteristics under low tension.

[0111] For example, taking a certain brand of cigarette packaging cardboard (basis weight 230g / m²) and an OPP film composite experiment as an example, the parameters of the asymmetric damage function of the present invention are calibrated.

[0112] (1) Reversible elastic window δ rev Determination: Different levels of tension deviation were applied to the cardboard substrate sample, held for 10 seconds, and then unloaded. The residual strain was measured. Experimental data showed that when the tension deviation did not exceed 3N, the residual strain after unloading was less than 0.1%. Therefore, δ was determined. rev = 3N.

[0113] (2) Irreversible damage threshold δ irr Measurement: With continued increase in tension deviation, when the deviation reaches 8N, the residual strain after unloading exceeds 0.5%, and the material undergoes significant permanent deformation. Therefore, δ is determined. irr = 8N.

[0114] (3) Calibration of the parameters of the first sub-function f1: In the range of 0 < x ≤ 3N, the damage score under different deviations was measured, and the fitting yielded α1 = 0.5 and p1 = 2.0. In the range of 3N < x ≤ 8N, the damage score was measured, and the fitting yielded β1 = 1.2 and q1 = 1.5.

[0115] (4) Calibration of the second sub-function parameters: Similarly, when the tension is small, the damage score is measured and fitted to obtain α2= 0.2, p2= 2.0, β2 = 0.4, q2= 1.5.

[0116] (5) Asymmetry verification: α1 / α2 = 2.5, β1 / β2 = 3.0, satisfying β ≥ α2 and β1 ≥ β2, verifying the physical fact that the damage risk of larger tension is significantly higher than that of smaller tension.

[0117] Furthermore, in some embodiments, step S200, determining the deviation section based on the moisture content distribution data, specifically includes:

[0118] S210. Starting from the moisture content monitoring station, calculate the local average moisture content along the paper feeding direction using a sliding window.

[0119] Specifically, a sliding window is set up along the paper feeding direction, starting from the moisture content monitoring station. The sliding window covers a predetermined length of cardboard substrate, corresponding to a fixed number of sampling points. For example, if the moisture content sensor's sampling period is 10ms and the feeding speed is 100m / min, then the cardboard substrate advances approximately 16.7mm every 10ms. Setting the window length to 100 sampling points means each window covers approximately 1.67 meters of cardboard substrate. Subsequently, the local mean of the moisture content at all sampling points within the current window is calculated. This mean represents the average moisture content level of the cardboard substrate within the window's coverage area.

[0120] S220. When the deviation between the average value of multiple consecutive windows and the preset benchmark moisture content exceeds a set threshold, a deviation segment is determined to have occurred, and the position of the window that first exceeds the first set threshold is recorded as the starting position of the deviation segment.

[0121] The number of consecutive windows judged is typically 3 to 5 to ensure the statistical significance of the identification results and avoid misjudgments due to accidental deviations of a single window. When recording the starting position of the deviation segment, the window position that first exceeds the first set threshold is recorded as the starting position of the deviation segment. This starting position is the distance or time offset relative to the moisture content monitoring station. Combined with the material feeding speed, it can be used to predict when the deviation segment will reach the subsequent target tension isolation segments.

[0122] In actual production processes, the data collected by moisture content sensors inevitably contains noise and random fluctuations. Directly comparing a single-point moisture content value with a benchmark moisture content to determine deviation can easily lead to misjudgments due to individual noise points, misidentifying normal fluctuations as deviations, or missing genuine deviations due to rebound at individual points. Therefore, this application employs a sliding window method, which effectively filters out high-frequency noise by locally averaging the moisture content values ​​of multiple consecutive sampling points, improving the stability and reliability of the identification. Furthermore, the judgment conditions for multiple consecutive windows further ensure that the identified deviation segments have sufficient length and significance, making them worthy of special tension control.

[0123] Information about the identified deviation sections, such as their starting position, length, and moisture content distribution, will be transmitted to the subsequent control module. Combined with the material feed rate, the system can accurately calculate the moment when the deviation section reaches each target tension isolation zone, thus triggering the corresponding tension adjustment operation when the deviation section enters the target tension isolation zone. Simultaneously, the moisture content distribution data within the deviation section will also serve as input parameters for feature type identification and tension setpoint calculation.

[0124] Secondly, referring to Figure 2 This application proposes a tension detection and control system for a film coating production line, the system comprising:

[0125] A moisture content monitoring module is configured to periodically acquire the real-time moisture content of the cardboard substrate being transported to the moisture content monitoring station, and obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction.

[0126] The judgment module is configured to determine, based on the moisture content distribution data, whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset reference moisture content.

[0127] A tension control module is configured to, if present, adjust the tension on the cardboard substrate within the target tension isolation section based on the moisture content distribution data of the cardboard substrate within the target tension isolation section, so as to minimize the material damage to the cardboard substrate caused by tension differences within the target tension isolation section; wherein the target tension isolation section is any one of a plurality of tension isolation intervals set along the paper feeding direction between the moisture content monitoring station and the lamination station.

[0128] The specific processes, principles, and beneficial effects of the methods and steps performed by the above modules have been introduced in the foregoing and will not be repeated here.

[0129] Furthermore, in some embodiments, the tension control module is also configured to determine the characteristic type of the target tension isolation section based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section; wherein, the characteristic type includes a steady-state type in which the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type in which the real-time moisture content changes monotonically along the paper feed direction within a continuous section;

[0130] Based on the characteristic types existing within the target tension isolation section, a corresponding calculation method for calculating the tension set value of the target tension isolation section is determined;

[0131] Based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, the tension setting value is calculated and determined, and the tension of the target tension isolation section is adjusted based on the tension setting value.

[0132] It should be noted that the sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0133] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0134] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0135] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0136] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0137] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device to execute the methods described in the various embodiments of this application.

[0138] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for tension detection and control in a film coating production line, characterized in that, It includes the following steps: The real-time moisture content of the cardboard substrate being transported to the moisture content monitoring station is periodically acquired to obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction; Based on the moisture content distribution data, determine whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset benchmark moisture content; If such a deviation zone exists within the target tension isolation zone, the tension on the cardboard substrate within the target tension isolation zone is adjusted based on the moisture content distribution data of the cardboard substrate within the target tension isolation zone, so as to minimize the material damage caused by tension differences to the cardboard substrate within the target tension isolation zone; wherein, the target tension isolation zone is any one of a plurality of tension isolation zones set along the paper feeding direction between the moisture content monitoring station and the lamination and compounding station.

2. The tension detection and control method for a coating production line as described in claim 1, characterized in that, When the deviation section exists within the target tension isolation section, the tension on the cardboard substrate within the target tension isolation section is adjusted based on the moisture content distribution data of the cardboard substrate within the target tension isolation section, including the following steps: Based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section, the characteristic type of the target tension isolation section is determined; wherein, the characteristic type includes a steady-state type in which the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type in which the real-time moisture content changes monotonically along the paper feeding direction within a continuous section. Based on the characteristic types existing within the target tension isolation section, a corresponding calculation method for calculating the tension set value of the target tension isolation section is determined; Based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, the tension setting value is calculated and determined, and the tension of the target tension isolation section is adjusted based on the tension setting value.

3. The tension detection and control method for a coating production line as described in claim 2, characterized in that, The step of calculating and determining the tension setpoint based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, and adjusting the tension of the target tension isolation section based on the tension setpoint, includes the following steps: If only the steady-state cardboard substrate exists within the target tension isolation zone, the representative moisture content is determined based on the moisture content distribution data of the cardboard substrate within the target tension isolation zone. The tension setpoint is calculated and determined based on the representative moisture content.

4. The tension detection and control method for a coating production line as described in claim 3, characterized in that, The tension setpoint is calculated and determined based on the representative moisture content using the following formula: ; Wherein, T0 is the reference tension setting value corresponding to the preset reference moisture content ω0; ω rep To represent moisture content; K is a pre-calibrated tension-moisture content compensation coefficient, which is determined according to the type of material of the cardboard substrate.

5. The tension detection and control method for a coating production line as described in claim 2, characterized in that, The step of calculating and determining the tension setpoint based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, and adjusting the tension of the target tension isolation section based on the tension setpoint, includes the following steps: If there is a transitional cardboard substrate in the target tension isolation section, the required tension sequence corresponding to each point in the target tension isolation section is determined based on the moisture content distribution data of each point in the cardboard substrate in the target tension isolation section at the current time. Based on the required tension sequence and the preset comprehensive impact score model reflecting the overall damage of the cardboard substrate, the tension setting value corresponding to the target tension isolation section at the current moment is solved with the goal of minimizing the total material damage caused by the deviation between the actual tension borne at each point and the required tension.

6. The tension detection and control method for a coating production line as described in claim 5, characterized in that, The comprehensive impact score model, based on the required tension sequence and a preset comprehensive impact score model reflecting the overall damage to the cardboard substrate, aims to minimize the total material damage caused by the deviation between the actual tension at each point and the required tension. The calculation formula for the comprehensive impact score model is as follows: ; In the formula, T(t) i ) for t i The set value of the target tension isolation section at any given time; ΔT i For t i The required tension corresponding to the cardboard substrate point that reaches the end of this section at any given moment; w i These are the weighting coefficients; f is the damage function, and when When > 0, the first sub-function f1 is used for calculation. When the value is less than 0, the second sub-function f2 is used for calculation to characterize the differential damage characteristics of the cardboard substrate under high tension and low tension.

7. The tension detection and control method for a coating production line as described in claim 6, characterized in that, The first sub-function f1 is calculated using the following formula: ; The second sub-function f2 is calculated using the following formula: ; Wherein, δ_rev is the reversible elastic window, representing the maximum tension deviation that the paperboard substrate can fully recover its elastic deformation after unloading; δ_irr is the irreversible damage threshold, representing the critical value of tension deviation corresponding to the permanent deformation of the cardboard substrate; α1, β1, p1, q1, α2, β2, p2, and q2 are all non-negative constants determined according to the material type of the cardboard substrate, and the penalty coefficients satisfy α1 not less than α2 and β1 not less than β2. M1 is the penalty value approaching infinity, and M2 is the penalty value approaching infinity.

8. The tension detection and control method for a coating production line as described in claim 1, characterized in that, The step of determining the deviation section based on the moisture content distribution data specifically includes: Starting from the moisture content monitoring station, the local average moisture content is calculated using a sliding window along the paper feeding direction; When the deviation of the average value of multiple consecutive windows from the preset benchmark moisture content exceeds a set threshold, a deviation segment is determined to have occurred, and the position of the window that first exceeds the first set threshold is recorded as the starting position of the deviation segment.

9. A tension detection and control system for a coating production line, characterized in that, It includes: A moisture content monitoring module is configured to periodically acquire the real-time moisture content of the cardboard substrate being transported to the moisture content monitoring station, and obtain the moisture content distribution data of the cardboard substrate in the paper feeding direction. The judgment module is configured to determine, based on the moisture content distribution data, whether there are multiple consecutive deviation sections on the cardboard substrate where the moisture content deviates from the preset reference moisture content. A tension control module is configured to, if present, adjust the tension on the cardboard substrate within the target tension isolation section based on the moisture content distribution data of the cardboard substrate within the target tension isolation section, so as to minimize the material damage to the cardboard substrate caused by tension differences within the target tension isolation section; wherein the target tension isolation section is any one of a plurality of tension isolation intervals set along the paper feeding direction between the moisture content monitoring station and the lamination station.

10. The tension detection and control system for the coating production line as described in claim 9, characterized in that, The tension control module is further configured to determine the characteristic type of the target tension isolation section based on the changing trend of the moisture content distribution data of the cardboard substrate within the target tension isolation section; wherein, the characteristic type includes a steady-state type in which the real-time moisture content fluctuates within a continuous section without exceeding a preset fluctuation range, and a transitional type in which the real-time moisture content changes monotonically along the paper feed direction within a continuous section. Based on the characteristic types existing within the target tension isolation section, a corresponding calculation method for calculating the tension set value of the target tension isolation section is determined; Based on the calculation method and the moisture content distribution data of the cardboard substrate within the target tension isolation section, the tension setting value is calculated and determined, and the tension of the target tension isolation section is adjusted based on the tension setting value.

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