A method for measuring thickness of synthetic leather online

Abstract

The invention discloses an online thickness measurement method for synthetic leather, comprising the following steps: S1, taking a roller attached to the back of the synthetic leather as a reference, collecting data through a sensor, and performing data preprocessing; S2, using an error compensation algorithm to calculate a roller error compensation value, and correcting the measured data in real time; S3, filtering vibration data to obtain a thickness after vibration compensation; S4, based on a speed and tension compensation model, obtaining a thickness after speed and tension compensation; S5, performing data fitting on the sampled data of each point; S6, combining the corrected measurement data, vibration compensation, speed and tension compensation, and data fitting results to calculate the final thickness value of each point; the method can perform real-time high-precision measurement of the thickness of synthetic leather in a dynamic production environment by taking the roller surface as a reference plane and utilizing multi-sensor redundant design, error compensation algorithm, data filtering, and speed and tension compensation model.

Description

Technical Field

[0001] The invention relates to the technical field of industrial measurement, and in particular to an online thickness measurement method for synthetic leather. Background Art

[0002] In the production process of synthetic leather, accurate measurement of material thickness is crucial, which is directly related to the quality and consistency of the product, as well as the effective control of production costs. Existing synthetic leather thickness measurement methods mainly rely on manually operated mechanical contact measurement, which has the following limitations: manual measurement is easily affected by the operator's subjective judgment, resulting in inconsistent measurement results, poor stability and low precision; contact measurement is easy to damage the surface of synthetic leather, and there is a risk of damage to synthetic leather; traditional methods are difficult to achieve online real-time monitoring, and cannot timely reflect the thickness changes in the production process, so that production parameters cannot be quickly adjusted to maintain product quality, and the real-time performance is insufficient. In addition, the traditional dual laser beam thickness measurement method is prone to large measurement errors when there is fluff on the back of the synthetic leather due to the presence of fluff or irregular fabric texture on the back of the synthetic leather, which cannot meet the needs of quality monitoring in the production process. At the same time, in the production process of synthetic leather, due to the influence of ground vibration and equipment operation, the sensor measurement results are easily disturbed by vibration, affecting the measurement stability, and the speed and tension changes of the rollers during the production process will have a dynamic impact on the thickness measurement, resulting in measurement errors, which is difficult to meet the actual measurement needs. Summary of the invention

[0003] To solve the above problems, the present invention proposes a method for online thickness measurement of synthetic leather. The method uses the roller surface as the reference plane and utilizes multi-sensor redundant design, error compensation algorithm, data filtering, speed and tension compensation model to perform real-time and high-precision measurement of the thickness of synthetic leather in a dynamic production environment.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A synthetic leather online thickness measurement method comprises the following steps:

[0006] S1, using the roller attached to the back of the synthetic leather as a reference, collecting data through a sensor, and performing data preprocessing;

[0007] The data collection in step S1 includes the following process:

[0008] S11. Install laser displacement sensors at the left, middle and right positions of the outer side of the roller. The three laser displacement sensors measure the distance from the curved surface of the roller to the optical displacement sensors at a frequency of 100 times per second, which are respectively recorded as D Left1 , D Center1 and D Right1 ;

[0009] S12, three laser displacement sensors collect the distance from the upper surface of the synthetic leather to the optical displacement sensor at a frequency of 100 times per second, respectively, and are recorded as D Left2 , D Center2 and D Right2 ;

[0010] S13, two vibration sensors are installed on the outer sides of the rollers, and the two vibration sensors collect environmental vibration data at the same frequency, which are recorded as A1(t) and A2(t) respectively;

[0011] The data preprocessing in step S1 includes the following process:

[0012] S14, synchronizing the data time of the three laser displacement sensors and the two vibration sensors to achieve consistent data acquisition timestamps;

[0013] S15, performing moving average filtering on the laser displacement sensor data at each point to reduce the impact of high-frequency noise. The specific calculation formula is: , where D avg (t) is the output value of the moving average filter at time point t, that is, the average thickness value of the synthetic leather at time point t; D(t-1) is the original data sequence at time point t-1, that is, the thickness value of the synthetic leather measured at time point t-1; N is the window size of the filter, that is, when calculating D avg (t) is the number of consecutive data points considered; i is the index variable in the summation process, ranging from 0 to N-1;

[0014] S2, using error compensation algorithm to calculate roller error compensation value and correct measurement data in real time;

[0015] S3, filtering the vibration data to obtain the thickness after vibration compensation;

[0016] S4, based on the speed and tension compensation model, obtaining the thickness after speed and tension compensation;

[0017] S5, performing data fitting on the sampled data of each point;

[0018] S6. The corrected measurement data, vibration compensation, speed and tension compensation, and data fitting results are combined to calculate the final thickness value of each point.

[0019] Preferably, the specific process of step S2 is:

[0020] S21, as the roller rotates, a laser displacement sensor is used to measure displacement data of the roller surface, wherein the displacement data represents a deviation between an actual shape of the roller and an ideal circle;

[0021] S22, the collected displacement data is subjected to Fourier transform, and the displacement data is converted from the time domain or space domain to the frequency domain. The complex periodic error is decomposed into the superposition of sine and cosine waveforms of different frequencies through Fourier transform. The calculation formula is: , where E(f) is the Fourier transform of the error; e(x) is the error function of the roller shape; j is an imaginary unit that satisfies = -1; f is the frequency; x is the position along the roller axis;

[0022] S23, using the Fourier coefficients obtained in step S21, calculate the roller shape error at any position x in the roller axis, and the error function is expressed as: , where e(x) is the error function of the roller shape, and e(x) represents the roller shape error calculated by Fourier coefficients; a n is the Fourier coefficient, representing the amplitude of the sine wave at different frequencies; b n is the Fourier coefficient, representing the amplitude of the cosine wave at different frequencies; n is the frequency index in the Fourier series; x is the position along the roller axis;

[0023] S24, subtracting the roller shape error at the corresponding position x from the real-time measurement data to obtain corrected measurement data.

[0024] Preferably, the specific process of step S3 is:

[0025] S31. Design Kalman filters for the left, middle and right points respectively to estimate and compensate for vibration effects. The state space model of the Kalman filter is: , where x k+1 is the state vector at time step k+1; A is the state transfer matrix; x k is the state vector; w k is the process noise; z k is the observed thickness data vector; H is the observation matrix; v k is the observation noise;

[0026] S32, using the estimated value of the Kalman filter, the thickness data of the left, middle and right points are corrected respectively to obtain the thickness after vibration compensation. The specific calculation formula is: T compL =T L -x k , T compC =T C -x k , T compR =T R -x k , where T compL is the thickness of the left synthetic leather after vibration compensation; TL The original thickness of the synthetic leather on the left side; T compC is the thickness of the middle synthetic leather after vibration compensation; T C The thickness of the middle synthetic leather measured originally; T compR is the thickness of the right synthetic leather after vibration compensation; T R The original thickness of the synthetic leather on the right; x k is the estimated value of the Kalman filter;

[0027] S33, performing Fourier transform on the filtered vibration data to identify the main vibration frequency and amplitude;

[0028] S34. Detect peaks in the Fourier transformed spectrum, the peaks corresponding to the main vibration frequencies.

[0029] Preferably, the specific process of step S4 is:

[0030] S41, the calculation formula of speed and tension compensation model is: ΔT=K1V+K2T+ , where ΔT is the thickness deviation of the synthetic leather; V is the conveying speed of the synthetic leather; T is the tension of the synthetic leather; multiple sets of measured data of ΔT, V and T are input into the calculation formula of the speed and tension compensation model, and the parameters K1, K2 and ;

[0031] S42, according to the real-time measured speed and tension data, respectively calculate the thickness deviation ΔT of the synthetic leather at the left, middle and right points, and subtract the thickness deviation of the synthetic leather from the thickness data after vibration compensation to obtain the thickness after speed and tension compensation. The specific calculation formula is: , , ,in, is the thickness of the synthetic leather on the left after speed and tension compensation; T compL This is the thickness of the left synthetic leather after vibration compensation; is the thickness of the intermediate synthetic leather after speed and tension compensation; T compC The thickness of the middle synthetic leather after vibration compensation; is the thickness of the synthetic leather on the right after speed and tension compensation; T compR This is the thickness of the synthetic leather on the right after vibration compensation.

[0032] Preferably, the specific process of step S5 is:

[0033] S51, polynomial fitting is performed on the sampled data of the left, middle and right points respectively to identify the trend of thickness change. The fitting model is expressed as: T fit (t) = a 0+ a1t1+ a2t 2+…+ a n t n Among them, T fit (t) is the fitted model, a 0， a 1， a 2，…， a n are polynomial coefficients, which are determined through the fitting process; t is the independent variable; t 1， t 2，…， t n are different powers of the independent variable t, used to construct the polynomial model; n is the highest degree of the polynomial;

[0034] S52, use the least squares method to fit the polynomial coefficients, and get the T corresponding to the left, middle and right points respectively. fitL (t)、T fitC (t) and T fitR (t).

[0035] Preferably, the specific calculation formula of step S6 is:

[0036] , , ,in, This is the final thickness of the synthetic leather on the left; The final thickness of the intermediate synthetic leather; This is the final thickness of the synthetic leather on the right.

[0037] After adopting the above technical scheme, the present invention has the following beneficial effects: the present invention can solve the problem of real-time thickness detection in the production process of synthetic leather. If an error is found in the thickness of the synthetic leather, the relevant production parameters can be adjusted in time to ensure product quality and consistency, while controlling production costs. It is particularly suitable for scenarios where the back of the synthetic leather has fluff or irregular fabric textures. These characteristics make traditional measurement methods difficult to implement accurately. Specifically, the present application uses a roller as a reference plane, allowing the back of the leather to fit the roller and rotate, thereby avoiding measurement errors caused by textures such as the fuzz on the back of the synthetic leather; laser displacement sensors are installed at the left, middle, and right positions of the roller, respectively, to achieve multi-dimensional thickness measurement and adapt to the non-ideal circular characteristics of the roller shape; the roller error compensation value is calculated based on the current angle and the result of Fourier transform, and the measurement data is corrected in real time, thereby eliminating the influence of the roller shape error on the thickness measurement; environmental vibration data is recorded by vibration sensors such as accelerometers, and the thickness data is corrected in real time in combination with the Kalman filter algorithm, thereby eliminating the influence of vibration on the measurement results; the measurement errors caused by speed and tension changes can be corrected through the speed and tension compensation model; therefore, the present invention uses the roller surface as the reference plane, utilizes multi-sensor redundant design, error compensation algorithm, data filtering, speed and tension compensation model, and can perform real-time and high-precision measurement of the thickness of synthetic leather in a dynamic production environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the process of the present invention;

[0039] Figure 2 It is a schematic diagram of the structure of the laser displacement sensor, the vibration sensor and the roller of the present invention;

[0040] Figure 3 It is a structural schematic diagram of the distance from the curved surface of the roller to the optical displacement sensor and the distance from the upper surface of the synthetic leather to the optical displacement sensor of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] like Figures 1 to 3 As shown, a synthetic leather online thickness measurement method comprises the following steps:

[0043] S1, using the roller attached to the back of the synthetic leather as a reference, collecting data through a sensor, and performing data preprocessing;

[0044] The data collection in step S1 includes the following process:

[0045] S11. Install laser displacement sensors at the left, middle and right positions of the outer side of the roller. The three laser displacement sensors measure the distance from the curved surface of the roller to the optical displacement sensors at a frequency of 100 times per second, which are respectively recorded as D Left1 , D Center1 and D Right1 ;like Figure 3 As shown in , D1 represents the distance from the curved surface of the roller to the optical displacement sensor;

[0046] S12, three laser displacement sensors collect the distance from the upper surface of the synthetic leather to the optical displacement sensor at a frequency of 100 times per second, respectively, and are recorded as D Left2 , D Center2 and D Right2 ;like Figure 3 As shown in , D2 represents the distance from the upper surface of the synthetic leather to the optical displacement sensor;

[0047] S13, two vibration sensors are installed on the outer sides of the rollers, and the two vibration sensors collect environmental vibration data at the same frequency, which are recorded as A1(t) and A2(t) respectively;

[0048] The data preprocessing in step S1 includes the following process:

[0049] S14, synchronizing the data time of the three laser displacement sensors and the two vibration sensors to achieve consistent data acquisition timestamps;

[0050] S15, performing moving average filtering on the laser displacement sensor data at each point to reduce the impact of high-frequency noise. The specific calculation formula is: , where D avg (t) is the output value of the moving average filter at time point t, that is, the average thickness value of the synthetic leather at time point t; D(t-1) is the original data sequence at time point t-1, that is, the thickness value of the synthetic leather measured at time point t-1; N is the window size of the filter, that is, when calculating D avg (t) is the number of consecutive data points considered; i is the index variable in the summation process, ranging from 0 to N-1;

[0051] S2, using error compensation algorithm to calculate roller error compensation value and correct measurement data in real time;

[0052] The specific process of step S2 is:

[0053] S21, as the roller rotates, a laser displacement sensor is used to measure displacement data of the roller surface, wherein the displacement data represents a deviation between an actual shape of the roller and an ideal circle;

[0054] S22, the collected displacement data is subjected to Fourier transform, and the displacement data is converted from the time domain or space domain to the frequency domain. The complex periodic error is decomposed into the superposition of sine and cosine waveforms of different frequencies through Fourier transform. The calculation formula is: , where E(f) is the Fourier transform of the error; e(x) is the error function of the roller shape; j is an imaginary unit that satisfies = -1; f is the frequency; x is the position along the roller axis;

[0055] S23, using the Fourier coefficients obtained in step S21, calculate the roller shape error at any position x in the roller axis, and the error function is expressed as: , where e(x) is the error function of the roller shape, and e(x) represents the roller shape error calculated by Fourier coefficients; a n is the Fourier coefficient, representing the amplitude of the sine wave at different frequencies; b n is the Fourier coefficient, representing the amplitude of the cosine wave at different frequencies; n is the frequency index in the Fourier series; x is the position along the roller axis;

[0056] S24, subtracting the roller shape error at the corresponding position x from the real-time measurement data to obtain corrected measurement data;

[0057] S3, filtering the vibration data to obtain the thickness after vibration compensation;

[0058] The specific process of step S3 is:

[0059] S31. Design Kalman filters for the left, middle and right points respectively to estimate and compensate for vibration effects. The state space model of the Kalman filter is: , where x k+1 is the state vector at time step k+1; A is the state transfer matrix; x k is the state vector; w k is the process noise; z k is the observed thickness data vector; H is the observation matrix; v k is the observation noise;

[0060] S32, using the estimated value of the Kalman filter, the thickness data of the left, middle and right points are corrected respectively to obtain the thickness after vibration compensation. The specific calculation formula is: T compL =T L -x k , T compC =T C -x k , T compR =T R -x k, where T compL is the thickness of the left synthetic leather after vibration compensation; T L The original thickness of the synthetic leather on the left side; T compC is the thickness of the middle synthetic leather after vibration compensation; T C The thickness of the middle synthetic leather measured originally; T compR is the thickness of the right synthetic leather after vibration compensation; T R The original thickness of the synthetic leather on the right; x k is the estimated value of the Kalman filter;

[0061] S33, performing Fourier transform on the filtered vibration data to identify the main vibration frequency and amplitude;

[0062] S34, detecting a peak in the Fourier transformed spectrum, the peak corresponding to a main vibration frequency;

[0063] The specific process of step S4 is:

[0064] S41, the calculation formula of speed and tension compensation model is: ΔT=K1V+K2T+ , where ΔT is the thickness deviation of the synthetic leather; V is the conveying speed of the synthetic leather; T is the tension of the synthetic leather; multiple sets of measured data of ΔT, V and T are input into the calculation formula of the speed and tension compensation model, and the parameters K1, K2 and ;

[0065] S42, according to the real-time measured speed and tension data, respectively calculate the thickness deviation ΔT of the synthetic leather at the left, middle and right points, and subtract the thickness deviation of the synthetic leather from the thickness data after vibration compensation to obtain the thickness after speed and tension compensation. The specific calculation formula is: , , ,in, is the thickness of the synthetic leather on the left after speed and tension compensation; T compL This is the thickness of the left synthetic leather after vibration compensation; is the thickness of the intermediate synthetic leather after speed and tension compensation; T compC The thickness of the middle synthetic leather after vibration compensation; is the thickness of the synthetic leather on the right after speed and tension compensation; T compR This is the thickness of the right synthetic leather after vibration compensation;

[0066] S5, performing data fitting on the sampled data of each point;

[0067] The specific process of step S5 is:

[0068] S51, polynomial fitting is performed on the sampled data of the left, middle and right points respectively to identify the trend of thickness change. The fitting model is expressed as: T fit (t) = a 0+ a1t 1+ a2t 2+…+ a n t n Among them, T fit (t) is the fitted model, a 0， a 1， a 2，…， a n are polynomial coefficients, which are determined through the fitting process; t is the independent variable; t 1， t 2，…， t n are different powers of the independent variable t, used to construct the polynomial model; n is the highest degree of the polynomial;

[0069] S52, use the least squares method to fit the polynomial coefficients, and get the T corresponding to the left, middle and right points respectively. fitL (t)、T fitC (t) and T fitR (t);

[0070] S6, combining the corrected measurement data, vibration compensation, speed and tension compensation, and data fitting results to calculate the final thickness value of each point;

[0071] The specific calculation formula of step S6 is:

[0072] , , ,in, This is the final thickness of the synthetic leather on the left; The final thickness of the intermediate synthetic leather; This is the final thickness of the synthetic leather on the right.

[0073] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for measuring thickness of synthetic leather online, characterized in that: The following steps are involved: S1, using the roller attached to the back of the synthetic leather as a reference, collecting data through a sensor, and performing data preprocessing; The data collection in step S1 includes the following process: S11. Install laser displacement sensors at the left, middle and right positions of the outer side of the roller. The three laser displacement sensors measure the distance from the curved surface of the roller to the optical displacement sensors at a frequency of 100 times per second, which are respectively recorded as D Left1 , D Center1 and D Right1 ; S12, three laser displacement sensors collect the distance from the upper surface of the synthetic leather to the optical displacement sensor at a frequency of 100 times per second, respectively, and are recorded as D Left2 , D Center2 and D Right2 ; S13, two vibration sensors are installed on the outer sides of the rollers, and the two vibration sensors collect environmental vibration data at the same frequency, which are recorded as A1(t) and A2(t) respectively; The data preprocessing in step S1 includes the following process: S14, synchronizing the data time of the three laser displacement sensors and the two vibration sensors to achieve consistent data acquisition timestamps; S15, performing moving average filtering on the laser displacement sensor data at each point to reduce the impact of high-frequency noise. The specific calculation formula is: , where D avg (t) is the output value of the moving average filter at time point t, that is, the average thickness value of the synthetic leather at time point t; D(t-1) is the original data sequence at time point t-1, that is, the thickness value of the synthetic leather measured at time point t-1; N is the window size of the filter, that is, when calculating D avg (t) is the number of consecutive data points considered; i is the index variable in the summation process, ranging from 0 to N-1; S2, using error compensation algorithm to calculate roller error compensation value and correct measurement data in real time; The specific process of step S2 is: S21, as the roller rotates, a laser displacement sensor is used to measure displacement data of the roller surface, wherein the displacement data represents a deviation between an actual shape of the roller and an ideal circle; S22, the collected displacement data is subjected to Fourier transform, and the displacement data is converted from the time domain or space domain to the frequency domain. The complex periodic error is decomposed into the superposition of sine and cosine waveforms of different frequencies through Fourier transform. The calculation formula is: , where E(f) is the Fourier transform of the error; e(x) is the error function of the roller shape; j is an imaginary unit that satisfies = -1; f is the frequency; x is the position along the roller axis; S23, using the Fourier coefficients obtained in step S21, calculate the roller shape error at any position x in the roller axis, and the error function is expressed as: , where e(x) is the error function of the roller shape, and e(x) represents the roller shape error calculated by Fourier coefficients; a n is the Fourier coefficient, representing the amplitude of the sine wave at different frequencies; b n is the Fourier coefficient, representing the amplitude of the cosine wave at different frequencies; n is the frequency index in the Fourier series; S24, subtracting the roller shape error at the corresponding position x from the real-time measurement data to obtain corrected measurement data; S3, filtering the vibration data to obtain the thickness after vibration compensation; S4, based on the speed and tension compensation model, obtaining the thickness after speed and tension compensation; S5, performing data fitting on the sampled data of each point; S6. The corrected measurement data, vibration compensation, speed and tension compensation, and data fitting results are combined to calculate the final thickness value of each point.

2. A synthetic leather online thickness measurement method as claimed in claim 1, characterized in that: The specific process of step S3 is: S31. Design Kalman filters for the left, middle and right points respectively to estimate and compensate for vibration effects. The state space model of the Kalman filter is: , where x k+1 is the state vector at time step k+1; A is the state transfer matrix; x k is the state vector; w k is the process noise; z k is the observed thickness data vector; H is the observation matrix; v k is the observation noise; S32, using the estimated value of the Kalman filter, the thickness data of the left, middle and right points are corrected respectively to obtain the thickness after vibration compensation. The specific calculation formula is: T compL =T L -x k , T compC =T C -x k , T compR =T R -x k , where T compL is the thickness of the left synthetic leather after vibration compensation; T L The original thickness of the synthetic leather on the left side; T compC is the thickness of the middle synthetic leather after vibration compensation; T C The thickness of the middle synthetic leather measured originally; T compR is the thickness of the right synthetic leather after vibration compensation; T R The original thickness of the synthetic leather on the right; x k is the estimated value of the Kalman filter; S33, performing Fourier transform on the filtered vibration data to identify the main vibration frequency and amplitude; S34. Detect peaks in the Fourier transformed spectrum, the peaks corresponding to the main vibration frequencies.

3. A synthetic leather online thickness measurement method as claimed in claim 2, characterized in that: The specific process of step S4 is: S41, the calculation formula of speed and tension compensation model is: ΔT=K1V+K2T+ , where ΔT is the thickness deviation of the synthetic leather; V is the conveying speed of the synthetic leather; T is the tension of the synthetic leather; multiple sets of measured data of ΔT, V and T are input into the calculation formula of the speed and tension compensation model, and the parameters K1, K2 and ; S42, according to the real-time measured speed and tension data, respectively calculate the thickness deviation ΔT of the synthetic leather at the left, middle and right points, and subtract the thickness deviation of the synthetic leather from the thickness data after vibration compensation to obtain the thickness after speed and tension compensation. The specific calculation formula is: , , ,in, is the thickness of the synthetic leather on the left after speed and tension compensation; T compL This is the thickness of the left synthetic leather after vibration compensation; is the thickness of the intermediate synthetic leather after speed and tension compensation; T compC The thickness of the middle synthetic leather after vibration compensation; is the thickness of the synthetic leather on the right after speed and tension compensation; T compR This is the thickness of the synthetic leather on the right after vibration compensation.

4. A synthetic leather online thickness measurement method as claimed in claim 3, characterized in that: The specific process of step S5 is: S51, polynomial fitting is performed on the sampled data of the left, middle and right points respectively to identify the trend of thickness change. The fitting model is expressed as: T fit (t) = a 0+ a1t 1+ a2t 2+…+ a n t n Among them, T fit (t) is the fitted model, a 0， a 1， a 2，…， a n are polynomial coefficients, which are determined through the fitting process; t is the independent variable; t 1， t 2，…， t n are different powers of the independent variable t, used to construct the polynomial model; n is the highest degree of the polynomial; S52, use the least squares method to fit the polynomial coefficients, and get the T corresponding to the left, middle and right points respectively. fitL (t)、T fitC (t) and T fitR (t).

5. A synthetic leather online thickness measurement method as claimed in claim 4, characterized in that: The specific calculation formula of step S6 is: , , ,in, This is the final thickness of the synthetic leather on the left; The final thickness of the intermediate synthetic leather; This is the final thickness of the synthetic leather on the right.

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