A method and system for measuring the thickness of wear-resistant and anti-stick coating of longitudinal pulling roller

Abstract

The present application relates to the technical field of coating thickness measurement, and specifically to a method and system for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal roller, the method comprising: collecting terahertz time-domain signals from different regions of the longitudinal roller; constructing an objective function using the difference between the predicted terahertz time-domain signals under different coating thicknesses and different refractive indices and the terahertz time-domain signals collected in the corresponding regions, and using an optimization function to obtain the optimal solution obtained in each iteration of the objective function of the corresponding region; the optimal solution includes the optimal coating thickness and refractive index under the corresponding number of iterations; analyzing the characteristics of the terahertz time-domain signals in different regions, and calculating the weight of each region; using the weight to weight the optimal coating thickness obtained in the last iteration of the corresponding region, and obtaining the thickness of the wear-resistant and anti-stick coating of the longitudinal roller. The present application aims to take into account the situation where there are defects in the coating and improve the accuracy of the thickness measurement of the wear-resistant and anti-stick coating of the longitudinal roller.

Description

Technical Field

[0001] The present application relates to the technical field of coating thickness measurement, and in particular to a method and system for measuring the thickness of a wear-resistant and anti-stick coating on a longitudinal pulling roller. Background Art

[0002] With the development of industrial technology, the progress of precision manufacturing and materials science has put forward higher requirements on the performance of production equipment. In many industrial applications, longitudinal pulling rollers are key components and are widely used in the processing of metal sheets, plastic films, paper and other materials. In order to ensure the quality and production efficiency of the products, the surface of the longitudinal pulling roller is usually coated with a wear-resistant and anti-stick coating to reduce wear and prevent material adhesion. Terahertz technology has shown great potential in the field of coating thickness measurement due to its non-destructive, high sensitivity and strong penetration. According to the reflection and transmission of terahertz pulses at the interfaces of different materials, the propagation time in the coating is determined by combining the reflection time delay, thereby determining the coating thickness.

[0003] However, due to the production process of the coating, there may be some defects such as pores in the coating area, and these defective locations will also reflect. In the original terahertz detection, the possibility of defects in the coating was not considered, resulting in redundant reflection information, which makes the final measured thickness have a certain error. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a method and system for measuring the thickness of the wear-resistant and anti-stick coating of a longitudinal pull roller. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller, the method comprising the following steps:

[0006] Collect terahertz time domain signals from different areas of the longitudinal pulling roller;

[0007] The objective function is constructed by using the difference between the predicted terahertz time domain signals under different coating thicknesses and different refractive indices and the terahertz time domain signals collected in the corresponding area, and the optimal solution obtained by each iteration of the objective function of the corresponding area is obtained by using the optimization function; the optimal solution includes the optimal coating thickness and refractive index under the corresponding number of iterations;

[0008] Analyze the terahertz time domain signal characteristics of different regions and calculate the weight of each region, specifically:

[0009] A1, determining the characteristic coefficient of the terahertz time domain signal in each area according to the numerical variation trend and position distribution of all peak values ​​in the terahertz time domain signal in each area;

[0010] A2, according to the optimal solution of all iterations in each region, the refractive index and the coating thickness are sorted in ascending order, and the change trend of the first peak, the second peak and the time difference between the first peak and the second peak in the corresponding predicted terahertz time domain signal is obtained to determine the trend change coefficient of each region;

[0011] A3, combining the characteristic coefficient and trend change coefficient to determine the weight of each area;

[0012] The optimal coating thickness obtained in the last iteration of the corresponding area is weighted by using the weight to obtain the wear-resistant and anti-stick coating thickness of the longitudinal pulling roller.

[0013] Preferably, the process of determining the characteristic coefficient is as follows: the characteristic coefficient of the terahertz time domain signal in region i is recorded as , ; In the formula, is the minimum value of the flight time series of region i except the first element, is the first element in the flight time series of region i, is the symbolic function, is the monotonicity trend measure of the peak sequence of region i, is the set of remaining elements except the first element in the flight time series of region i, is the variance function, To avoid the default tuning coefficients with denominator equal to 0.

[0014] Preferably, the peak sequence consists of values ​​of all peaks in the terahertz time-domain signal of region i.

[0015] Preferably, the flight time series consists of the time differences between the moments of all adjacent peaks in the terahertz time domain signal of region i.

[0016] Preferably, the monotonicity trend measure of the peak sequence of region i is The calculation formula is: ,in, is the number of negative numbers in the first-order difference sequence of the peak sequence of region i, p is the length of the first-order difference sequence of the peak sequence of region i, is the absolute value symbol.

[0017] Preferably, the process of determining the trend change coefficient includes:

[0018] The refractive indices are arranged in ascending order to form a refractive index sequence, and the first peak value, the second peak value and the time difference in the predicted terahertz time domain signal corresponding to each element in the refractive index sequence are obtained to form a refractive first peak sequence, a refractive second peak sequence and a refractive flight time sequence respectively;

[0019] According to the same method as the refractive index acquisition of four sequences, a thickness sequence, a thickness first peak sequence, a thickness second peak sequence and a thickness flight time sequence of the coating thickness are acquired;

[0020] The trend change coefficient of region i is recorded as , ; In the formula, , are the refractive index variation coefficient and thickness variation coefficient of region i, It is the average level of the correlation between the refraction flight time series and the refractive index series, and between the thickness flight time series and the thickness series.

[0021] Preferably, the determination expressions of the refractive index variation coefficient and the thickness variation coefficient are:

[0022] ,in, , are the slopes of the fitted straight lines of the first refraction peak sequence and the second refraction peak sequence, respectively. , are the determination coefficients of the fitting lines of the first peak sequence of refraction and the second peak sequence of refraction, is a symbolic function;

[0023] ,in, , are the slope and determination coefficient of the second peak sequence fitting line of thickness, is the first peak sequence of thickness, is the variance function.

[0024] Preferably, the weight is determined by: recording the weight of region i as , ; In the formula, It is a region The characteristic coefficient of is the average value of the characteristic coefficients of all regions, It is a region The trend coefficient of change, is the set of trend change coefficients of all regions, is the maximum value function.

[0025] Preferably, the thickness of the wear-resistant and anti-stick coating of the longitudinal pulling roller is determined by weighted averaging the optimal coating thickness obtained in the last iteration of all regions.

[0026] In the second aspect, an embodiment of the present application also provides a system for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pulling roller, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned methods for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pulling roller are implemented.

[0027] This application has at least the following beneficial effects:

[0028] According to the characteristics of reflection and transmission of terahertz waves between different media, the present application analyzes the numerical variation trend and position distribution of the peak value in the terahertz time domain signal collected in each area, and calculates the characteristic coefficient of each area. The characteristic coefficient improves the accuracy of identifying obvious defects in the regional coating, thereby improving the accuracy of subsequent coating thickness measurement; and then calculates the trend variation coefficient of each area based on the variation trend characteristics of the first peak, the second peak, and the time difference between the first peak and the second peak in the terahertz time domain signal caused by the refractive index change and the coating thickness change, thereby improving the accuracy of identifying small anomalies in the regional coating, thereby further improving the accuracy of subsequent coating thickness measurement. The accuracy of coating thickness measurement was further improved; finally, the weight of each area was calculated, and the accuracy of the predicted coating thickness of the optimal solution in each area was quantified. In this way, when using terahertz waves for coating thickness detection, the problem of defects in the coating affecting the accuracy of thickness measurement was considered, and the coating conditions in different areas were evaluated and weighted. Finally, the final measured coating thickness was obtained by weighted average of all areas, which not only ensured the detection effect of terahertz waves, but also avoided the measurement error caused by defective coatings, further enhancing the accuracy of thickness measurement of wear-resistant and anti-stick coatings of longitudinal pulling rollers using terahertz technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A flow chart of a method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller provided in one embodiment of the present application;

[0031] Figure 2 A flow chart of a calculation process of the weight of each region provided in one embodiment of the present application;

[0032] Figure 3A schematic diagram of the propagation of terahertz waves in a single-layer structure when there are no defects in the coating area provided for one embodiment of the present application;

[0033] Figure 4 A schematic diagram of a terahertz time domain signal under normal conditions provided by an embodiment of the present application;

[0034] Figure 5 A schematic diagram of a terahertz time domain signal in the presence of defects provided by one embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of the method and system for measuring the thickness of the wear-resistant and anti-stick coating of a longitudinal pull roller proposed in the present application, its specific implementation, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0036] Unless defined otherwise, 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 application belongs.

[0037] The following is a detailed description of a method and system for measuring the thickness of a wear-resistant and anti-stick coating on a longitudinal pulling roller provided by the present application in conjunction with the accompanying drawings.

[0038] An embodiment of the present application provides a method and system for measuring the thickness of a wear-resistant and anti-stick coating on a longitudinal pulling roller.

[0039] Specifically, the following method for measuring the thickness of the wear-resistant and anti-stick coating of a longitudinal pull roller is provided. Figure 1 , the method comprises the following steps:

[0040] The first step is to collect the terahertz time domain signals from different areas of the longitudinal pulling roller.

[0041] The entire longitudinal pull roller is divided into In each area, a terahertz time-domain spectroscopy system is used to detect the terahertz time-domain signal of each area.

[0042] In the embodiment of the present application, the number of regions The value is 5; the terahertz time-domain spectroscopy system used uses a fiber pulse laser as the laser source, with an output power of 20mW, a pulse power of 1.25kW, a pulse duration of 80fs, a repetition frequency of 100MHz, a wavelength of 1064nm, a detection spectrum width of 0.1~2THz, a signal-to-noise ratio of 50dB, a delay window of 320ps, a spectrum resolution of 6.25GHz, and a time resolution of 0.2ps.

[0043] At this point, the terahertz time domain signals of different regions of the longitudinal pulling roller can be obtained by the above method.

[0044] The second step is to construct an objective function using the difference between the predicted terahertz time-domain signals under different coating thicknesses and different refractive indices and the terahertz time-domain signals collected in the corresponding area, and use the optimization function to obtain the optimal solution obtained in each iteration of the objective function in the corresponding area; the optimal solution includes the optimal coating thickness and refractive index under the corresponding number of iterations.

[0045] The reflection coefficient model is constructed using Fresnel's law and propagation matrix. The parameters required for the reflection coefficient model construction are the refractive index of the terahertz wave in the air. , the refractive index in the coating medium , coating thickness d, wavelength and frequency of the terahertz wave, where the wavelength and frequency of the terahertz wave are fixed values, and the refractive index is the refractive index of terahertz waves in air, which remains basically unchanged; is the refractive index in the coating medium. Due to the unevenness of coating coverage and the fact that the coating thickness may not be completely consistent, and even if the same coating material has certain differences in internal microstructure (pores, grain distribution, microscopic defects), these reasons will cause the refractive index of the same coating material to be different. Therefore, the coating thickness d and the refractive index in the coating medium are Not fixed.

[0046] Output of different coating thicknesses d and the refractive index in the coating medium through the reflection coefficient model Then, by The product of the reflection coefficient is inversely Fourier transformed to obtain the predicted terahertz time domain signal. The process of constructing the reflection coefficient model and the process of inverse Fourier transform are both well-known technologies, and the specific process will not be repeated.

[0047] Set the number of particles to m (in this example, m=50), the particle dimension to u (in this example, u=2, and the refractive index of the coating medium, respectively). , coating thickness d), maximum number of system iterations l (l=100 in this embodiment), inertia weight ω (ω=0.5 in this embodiment), initial learning factor , ( ), the objective function is the difference between the predicted terahertz time-domain signal and the actually collected terahertz time-domain signal, and the optimal solution of the objective function is to obtain the minimum value.

[0048] The objective function, the initial position of each particle, the initial velocity of each particle (the initial velocity is 0), the refractive index of the terahertz wave in the air , the wavelength and frequency of the terahertz wave are used as input, and the particle swarm optimization algorithm is used to output the optimal solution obtained in each iteration and the final optimal solution, and the optimal solutions obtained in previous iterations are combined into an optimal solution set. Among them, the optimal solution obtained in each iteration includes the predicted terahertz time domain signal, the coating thickness d, and the refractive index in the coating medium. The final optimal solution is the optimal solution obtained in the last iteration of the region. The particle swarm optimization algorithm is a well-known technology, and the specific process is not repeated here.

[0049] Using the particle swarm optimization algorithm, the optimal solution set for each region and the final optimal solution can be obtained.

[0050] The third step is to analyze the terahertz time domain signal characteristics of different regions and calculate the weight of each region.

[0051] Under normal circumstances, when a terahertz pulse irradiates a coating material, partial reflection and transmission will occur at the surface and bottom interface of the coating. Based on the time delay of the reflected wave, the propagation time of the terahertz wave in the coating material can be determined, and this time delay is proportional to the thickness of the coating. However, when there are defects in the coating (such as bubbles), reflection will also occur. At this time, only using the reflection delay time to judge the thickness will cause errors in the thickness measurement results.

[0052] In order to avoid this situation, the present application performs terahertz detection in multiple areas separately. Since the propagation of terahertz waves in materials has relatively fixed characteristics, these characteristics make the terahertz time-domain signals finally collected also have certain characteristics. Therefore, by analyzing the terahertz time-domain signals in each area, the situation in each area can be judged relatively accurately, thereby making the final calculated coating thickness more accurate.

[0053] In the embodiment of the present application, the calculation process of the weight of each region is as shown in the attached Figure 2 As shown, specifically:

[0054] A1, according to the numerical variation trend and position distribution of all peak values ​​in the terahertz time domain signal in each area, determine the characteristic coefficient of the terahertz time domain signal in each area.

[0055] In the embodiment of the present application, under normal circumstances, when there are no defects in the coating area, the propagation diagram of the terahertz wave in the single-layer structure is as shown in the attached figure. Figure 3 shown.

[0056] exist Figure 3 middle, represents the interface between air and coating, Indicates the coating area, Indicates the interface between the coating and the substrate. Terahertz waves will reflect and transmit between different materials. The interface between air and coating First, a reflection occurs, and the reflected wave It can be reflected in the first peak of the collected terahertz time domain signal and transmitted into the coating area. The terahertz wave at the interface between the coating and the substrate Reflected again, where it is transmitted into the coating area The incident angle of the terahertz wave is , at the interface between the coating and the substrate The incident angle of the terahertz wave is , the final reflected wave It becomes a peak in the collected terahertz time domain signal. By analogy, all reflected waves and their corresponding peaks can be collected. d is the thickness of the wear-resistant and anti-stick coating of the longitudinal pull roller.

[0057] Under normal circumstances, terahertz waves are reflected and transmitted between different materials, and the path length experienced by each transmission and reflection is basically the same. Transmission and reflection will cause the attenuation of terahertz wave energy, so the peaks corresponding to the collected reflected waves have a strict monotonically decreasing trend, and the flight time of the first reflected wave (the time difference between the initial moment and the first peak moment) is less than the flight time of the subsequent reflected waves. Starting from the second reflected wave, the flight time of two adjacent reflected waves should be basically consistent.

[0058] In the embodiment of the present application, the schematic diagram of the terahertz time domain signal under normal conditions is as shown in the attached Figure 4 On the contrary, when there are defects in the coating area, reflection will occur in the middle part, so that the corresponding reflection and transmission paths are relatively shortened, the energy attenuation is small, the strict decreasing trend of the wave crest will be destroyed, and the consistency of the flight time between two adjacent reflected waves will be destroyed.

[0059] In the embodiment of the present application, a schematic diagram of a terahertz time domain signal in the presence of a defect is shown in the attached Figure 5 shown.

[0060] exist Figure 4 and Figure 5In the figure, the horizontal axis is time, the unit is ps (picoseconds), and the vertical axis is the terahertz time domain signal, the unit is au (arbitrary unit).

[0061] The flight time of other reflected waves except the first reflected wave refers to the time difference between the moment of the peak of the current reflected wave and the moment of the peak of the previous adjacent reflected wave.

[0062] The terahertz time domain signal collected in a region is used as input, and an automatic peak-finding algorithm is used to output each peak value and the corresponding time in the signal. All peak values ​​are organized into a peak sequence of the corresponding region in time order, and a first-order difference sequence of the peak sequence is obtained; the time difference between the moments of all adjacent elements in the peak sequence is organized into a flight time sequence of the corresponding region in the order of acquisition time. In this way, the first-order difference sequence and flight time sequence of the peak sequence of each region are obtained. Among them, the automatic peak-finding algorithm is a well-known technology and will not be repeated.

[0063] Based on the above analysis, the characteristic coefficient of the terahertz time domain signal in each area is determined according to the numerical change trend and position distribution of all peak values ​​in the terahertz time domain signal in each area. It is used to measure the degree to which the terahertz time domain signal in a region conforms to the reflection and transmission characteristics of the terahertz wave, and then judge whether there are obvious defects in the coating of the area.

[0064] In the embodiment of the present application, taking region i as an example for analysis, the characteristic coefficient of the terahertz time domain signal of region i is recorded as , ; In the formula, is the minimum value of the flight time series of region i except the first element, is the first element in the flight time series of region i, is the symbolic function, is the monotonicity trend measure of the peak sequence of region i, is the set of remaining elements except the first element in the flight time series of region i, is the variance function, To avoid the preset parameter adjustment coefficient with the denominator being 0. Among them, the sign function and the variance function are both well-known technologies and will not be described in detail.

[0065] In the embodiments of the present application, The value is 1. ,in, is the number of negative numbers in the first-order difference sequence of the peak sequence of region i, p is the length of the first-order difference sequence of the peak sequence of region i, is the absolute value symbol.

[0066] It can be understood that when there is no obvious defect in the coating area corresponding to a region, each peak in the terahertz time domain signal shows a strictly monotonically decreasing trend, so that the elements in the first-order difference sequence of the peak sequence are all negative, that is, is 0; secondly, the flight time of the first reflected wave is the smallest, and the flight time between adjacent peaks after the peak of the second reflected wave is basically the same, that is, is always greater than 0, and the fluctuation of the elements of the flight time series except the first element is small, that is, Therefore, when there is no obvious defect in the coating area corresponding to a region, the characteristic coefficient of the region is positive and large. On the contrary, when there is an obvious defect in the coating area corresponding to a region, the characteristic coefficient of the region is small, and the more obvious the defect, the smaller the characteristic coefficient.

[0067] A2, according to the optimal solution under all iteration times in each area, the refractive index and coating thickness are sorted in ascending order, and the change trend of the first peak, the second peak and the time difference between the first peak and the second peak in the corresponding predicted terahertz time domain signal is obtained to determine the trend change coefficient of each area.

[0068] Using the particle swarm optimization algorithm, the optimal coating thickness of each area can be obtained. Under normal circumstances, the coating thickness of each area should be relatively uniform, so the average of the optimal coating thickness of each area is calculated and further smoothed to make the obtained coating thickness more accurate.

[0069] However, in practice, the coating conditions in different regions are not completely consistent, so the terahertz time domain signals in different regions are not completely the same, and some coating regions may even have defects. The characteristic coefficients calculated above can identify larger defects in the coating region, but when the defects are small, they cannot be accurately identified. Therefore, it is necessary to combine the refractive index, coating thickness, first peak and second peak of each region to further measure the coating thickness. Since this change trend takes into account the peak changes corresponding to different refractive indices and coating thicknesses, it can more accurately measure the conditions of the coating area.

[0070] According to the influence of coating material parameters on terahertz time domain signals, as the refractive index increases, the first peak gradually increases, and the increasing trend is close to linear; the second peak decreases as the refractive index increases, but there is no linear relationship in the change trend; the flight time between the two peaks is positively correlated with the refractive index. As the thickness increases, the first peak remains basically unchanged or shows an insignificant slight change, and the second peak decreases as the thickness increases, but the decreasing trend is nonlinear, and the flight time between the two peaks is also positively correlated with the thickness.

[0071] It can be understood that a positive correlation means that the dependent variable will increase as the independent variable increases, and the dependent variable will decrease as the independent variable decreases. This is determined by actual application and is not specifically limited in this application.

[0072] All elements in the optimal solution set of a region are sorted according to the refractive index. , thickness d in order from small to large, forming the refractive index solution sequence and the thickness solution sequence.

[0073] In the refractive index solution set sequence, the terahertz time domain signal predicted by the optimal solution under the corresponding iteration number of each element is obtained, and the first peak value, the second peak value and the time difference between the first peak value and the second peak value in each predicted terahertz time domain signal are obtained; all the refractive indices, the first peak value, the second peak value and the time difference are respectively formed into a refractive index sequence, a refraction first peak value sequence, a refraction second peak value sequence and a refraction flight time sequence in the order of the size of the refractive index.

[0074] Similarly, the thickness solution sequence can be processed in the same way to obtain the thickness sequence, the thickness first peak sequence, the thickness second peak sequence, and the thickness flight time sequence.

[0075] The first refraction peak sequence, the second refraction peak sequence and the second thickness peak sequence are linearly fitted respectively, and the fitting straight line of each sequence is output. The embodiment of the present application adopts the least square method for straight line fitting, and the least square method is a well-known technology, and the specific process is not repeated. In other embodiments of the present application, other straight line fitting algorithms such as polynomial regression and Bayesian regression can also be used for straight line fitting.

[0076] Based on the above analysis, the trend change coefficient of each region is calculated to measure the change characteristics of the terahertz time domain signal in each region, and further measure whether there are abnormal defects in the coating of the region. The calculation expression of the trend change coefficient in the embodiment of the present application is:

[0077] The trend change coefficient of region i is recorded as , ; In the formula, , are the refractive index variation coefficient and thickness variation coefficient of region i, It is the average level of the correlation between the refraction flight time series and the refractive index series, and between the thickness flight time series and the thickness series.

[0078] In the embodiment of the present application, the correlation between the two sequences is calculated by the Pearson correlation coefficient, wherein the calculation process of the Pearson correlation coefficient is a well-known technique and will not be described in detail. In other embodiments of the present application, the inverse of the DTW distance may also be used to reflect the correlation between the two sequences.

[0079] In the embodiments of the present application, ,in, , are the slopes of the fitted straight lines of the first refraction peak sequence and the second refraction peak sequence, respectively. , are the determination coefficients of the fitting lines of the first peak sequence of refraction and the second peak sequence of refraction, is a symbolic function; ,in, , are the slope and determination coefficient of the second peak sequence fitting line of thickness, is the first peak sequence of thickness, is the variance function.

[0080] It can be understood that, under normal circumstances, as the refractive index increases, the first peak sequence of refraction presents a linear monotonically increasing trend, that is, is positive and The second peak sequence of refraction shows a nonlinear monotonically decreasing trend, that is, is negative and Smaller, so is negative and small; as the thickness increases, the first peak sequence of thickness remains basically unchanged, so The second peak sequence of thickness is nonlinearly decreasing, that is, is negative and Smaller, so is negative and small; the flight time is positively correlated with the refractive index and thickness, that is, C is positive and large; so under normal circumstances, the area The trend coefficient of change Negative and small.

[0081] It should be understood that when defects appear in the coating of region i, the terahertz time domain signal will be relatively chaotic, so that it cannot completely comply with the change trend of this relative law, thus making the trend change coefficient Larger.

[0082] A3, combine the characteristic coefficient and trend change coefficient to determine the weight of each area.

[0083] The embodiment of the present application uses the characteristic coefficient and trend change coefficient of each region to construct the weight of the region, which is used to evaluate the presence of defects in the region, so as to focus on the thickness of the corresponding region. The larger the defect, the smaller the weight, and the smaller the influence of the measured coating thickness of the region on the overall thickness measurement result; conversely, when there is no defect in the region, the larger the weight, the greater the influence on the overall thickness measurement result.

[0084] Among them, the characteristic coefficient is first used to judge the obvious degree of defects in the whole area, and then the trend change coefficient is used to judge the tiny defects that appear locally, so that the defects in the area can be accurately identified.

[0085] In the embodiment of the present application, taking region i as an example, the calculation expression of the weight of region i is:

[0086]

[0087] In the formula, It is a region The weight of It is a region The characteristic coefficient of is the average value of the characteristic coefficients of all regions, It is a region The trend coefficient of change, is the set of trend change coefficients of all regions, is the maximum value function.

[0088] It can be understood that when the characteristic coefficient of a region is a non-positive number, it means that there are obvious defects in the coating of the region, and there is a large error in the thickness of the region, so its weight is set to 1, so that the coating thickness measured in the region has a smaller impact on the overall thickness measurement result;

[0089] When the characteristic coefficient of a region is greater than the average characteristic coefficient, it means that there are almost no defects in the coating of this region, so its thickness is relatively accurate, so its weight is set to 2, so that the coating thickness measured in this region has a greater impact on the overall thickness measurement result;

[0090] When the characteristic coefficient of a region is greater than 0 and less than the mean When the defect situation in this area cannot be accurately judged, the weight is set in combination with the trend change coefficient. The weight range is , using the changing relationship that the more serious the defect, the smaller the weight, the effect of the coating thickness measured in this area on the overall thickness measurement result is controlled.

[0091] In the fourth step, the optimal coating thickness obtained in the last iteration of the corresponding area is weighted by using the weight to obtain the wear-resistant and anti-stick coating thickness of the longitudinal pulling roller.

[0092] Using the particle swarm optimization algorithm, a final optimal solution is obtained for each area. The final optimal solution is the optimal solution obtained in the last iteration of the area, which includes the optimal coating thickness. Then, according to the weight of each area calculated in the third step, the optimal coating thickness of all areas is weighted averaged, thereby achieving accurate measurement of the wear-resistant and anti-stick coating thickness d of the longitudinal pulling roller.

[0093] In the embodiment of the present application, the calculation formula for the thickness d of the wear-resistant and anti-stick coating of the longitudinal pulling roller is: ; In the formula, is the number of regions, is the weight of region i, is the optimal coating thickness obtained in the last iteration for region i.

[0094] In this way, when using terahertz technology to measure the thickness of the coating, based on the changing characteristics of the terahertz time domain signals collected in different areas and combined with the propagation characteristics of terahertz waves in different media, we can not only achieve accurate measurement of the coating thickness, but also take into account the negative impact of defects in the coating on the accuracy of thickness measurement, making the measurement of coating thickness more accurate.

[0095] Based on the same inventive concept as the above-mentioned method, an embodiment of the present application also provides a system for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pulling roller, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of a method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pulling roller described in any one of the above-mentioned methods are implemented.

[0096] The various embodiments in the present application are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0097] It should be noted that, unless otherwise specified and limited, terms such as "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, an element defined by the sentence "including one..." does not exclude the existence of other identical elements in the article or device including the element. In addition, the term "and\or" used herein includes any and all combinations of one or more related listed items.

[0098] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not invented by the present application.

[0099] It should be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller, characterized in that: The method comprises the following steps: Collect terahertz time domain signals from different areas of the longitudinal pulling roller; The objective function is constructed by using the difference between the predicted terahertz time domain signals under different coating thicknesses and different refractive indices and the terahertz time domain signals collected in the corresponding area, and the optimal solution obtained by each iteration of the objective function of the corresponding area is obtained by using the optimization function; the optimal solution includes the optimal coating thickness and refractive index under the corresponding number of iterations; Analyze the terahertz time domain signal characteristics of different regions and calculate the weight of each region, specifically: A1, determining the characteristic coefficient of the terahertz time domain signal in each area according to the numerical change trend and position distribution of all peak values ​​in the terahertz time domain signal in each area; A2, according to the optimal solution of all iterations in each region, the refractive index and the coating thickness are sorted in ascending order, and the change trend of the first peak, the second peak and the time difference between the first peak and the second peak in the corresponding predicted terahertz time domain signal is obtained to determine the trend change coefficient of each region; A3, combining the characteristic coefficient and trend change coefficient to determine the weight of each area; The optimal coating thickness obtained by the last iteration of the corresponding area is weighted by using the weight to obtain the wear-resistant and anti-stick coating thickness of the longitudinal pulling roller; The process of determining the characteristic coefficient is as follows: the characteristic coefficient of the terahertz time domain signal in region i is recorded as , ; In the formula, is the minimum value of the flight time series of region i except the first element, is the first element in the flight time series of region i, is the symbolic function, is the monotonicity trend measure of the peak sequence of region i, is the set of remaining elements except the first element in the flight time series of region i, is the variance function, To avoid the preset parameter adjustment coefficient with denominator being 0; The process of determining the trend change coefficient includes: The refractive indices are arranged in ascending order to form a refractive index sequence, and the first peak value, the second peak value and the time difference in the predicted terahertz time domain signal corresponding to each element in the refractive index sequence are obtained to form a refractive first peak sequence, a refractive second peak sequence and a refractive flight time sequence respectively; According to the same method as the refractive index acquisition of four sequences, a thickness sequence, a thickness first peak sequence, a thickness second peak sequence and a thickness flight time sequence of the coating thickness are acquired; The trend change coefficient of region i is recorded as , ; In the formula, , are the refractive index variation coefficient and thickness variation coefficient of region i, It is the average level of the correlation between the refraction flight time series and the refractive index series, and between the thickness flight time series and the thickness series.

2. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: The peak sequence is composed of the values ​​of all peaks in the terahertz time domain signal of region i.

3. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: The flight time series is composed of the time differences between the moments of all adjacent peaks in the terahertz time domain signal of region i.

4. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: Monotonicity trend measure of the peak sequence of region i The calculation formula is: ,in, is the number of negative numbers in the first-order difference sequence of the peak sequence of region i, p is the length of the first-order difference sequence of the peak sequence of region i, is the absolute value symbol.

5. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: The determination expressions of the refractive index variation coefficient and the thickness variation coefficient are as follows: ,in, , are the slopes of the fitted straight lines of the first refraction peak sequence and the second refraction peak sequence, respectively. , are the determination coefficients of the fitting lines of the first peak sequence of refraction and the second peak sequence of refraction, is a symbolic function; ,in, , are the slope and determination coefficient of the second peak sequence fitting line of thickness, is the first peak sequence of thickness, is the variance function.

6. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: The weight is determined by: the weight of region i is recorded as , ; In the formula, It is a region The characteristic coefficient of is the average value of the characteristic coefficients of all regions, It is a region The trend coefficient of change, is the set of trend change coefficients of all regions, is the maximum value function.

7. A method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pull roller as claimed in claim 1, characterized in that: The thickness of the wear-resistant and anti-stick coating of the longitudinal pulling roller is determined by weighted averaging the optimal coating thickness obtained in the last iteration of all regions.

8. A longitudinal roller wear-resistant and anti-stick coating thickness measurement system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of a method for measuring the thickness of a wear-resistant and anti-stick coating of a longitudinal pulling roller as described in any one of claims 1-7 are implemented.

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