Method, equipment and device for detecting moisture content of wood board

Abstract

The invention relates to the technical field of moisture content detection, in particular to a wood board moisture content detection method, detection equipment and detection device.The method comprises the steps that all frequency spectrum signals and moisture content of all wood board samples are obtained; according to the average level of the data volume difference of the frequency spectrum signals before and after smoothing processing, obtaining the average retention coefficient of the single wood board sample under the single sampling frequency; obtaining a first characteristic value and a second characteristic value of all the wood board samples under a single sampling frequency according to whether the attenuation amount and the phase shift amount of the wood board samples under each frequency spectrum signal are in direct proportion to the moisture content and the frequency; acquiring a comprehensive interference coefficient of each wood board sample under a single sampling frequency; obtaining a standard frequency according to the average retention coefficient, the first characteristic value and the second characteristic value; and obtaining a calibration equation of the wooden board, and further detecting the moisture content of the wooden board to be detected. According to the method, the accuracy of the calibration equation is improved by screening the most accurate attenuation amount and phase shift amount of the wooden board.

Description

Technical Field

[0001] The present application relates to the technical field of moisture content detection, and particularly relates to a method, a device, and an apparatus for detecting the moisture content of a wood board. Background Art

[0002] Wood is a hygroscopic material, and its moisture content will change with the change of environmental humidity. If the moisture content of the wood board is too high or too low, it is easy to cause problems such as deformation and cracking of the wood board. Therefore, it is necessary to detect the moisture content of the wood board to reasonably control the moisture content in the wood board and reduce the loss of the wood board during storage and transportation.

[0003] For the moisture content detection method based on microwave technology, such as using a transmissive microwave radar moisture sensor to detect the moisture content, compared with the traditional moisture detection methods based on techniques such as drying and weighing, resistance, and capacitance, it can achieve rapid, non-destructive, integral, and production-line moisture content detection of wood boards. This method quickly measures the moisture content in the measured substance by obtaining the calibration equation between the amplitude attenuation and phase shift of the transmitted microwave signal of the measured substance and the moisture content of the measured substance. However, noise easily exists during the acquisition and transmission of microwave signals, so that redundant or irrelevant information will be introduced at inferior frequencies in the microwave signals, which will affect the accurate acquisition of the amplitude attenuation and phase shift in the microwave signals of the wood board, and further affect the reliability of the finally obtained calibration equation, resulting in low accuracy when detecting the moisture content of the wood board. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present application is to provide a method, a device, and an apparatus for detecting the moisture content of a wood board, and the specific technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for detecting the moisture content of a wood board, and the method includes the following steps:

[0006] Obtain the attenuation spectrum signal, phase shift spectrum signal, and moisture content of each wood board sample;

[0007] Record both the attenuation spectrum signal and the phase shift spectrum signal as spectrum signals; obtain the average retention coefficient of a single wood board sample at a single sampling frequency according to the average level of the difference between the data amounts of all spectrum signals of a single wood board sample at a single sampling frequency before and after smoothing processing.

[0008] Obtain the moisture fitting lines of the data volume corresponding to the single sampling frequency of all wood board samples under various spectral signals, and obtain the first eigenvalue of all wood board samples at the single sampling frequency according to the slope of each moisture fitting line and the difference between the actual value and the fitting value corresponding to each moisture fitting line; Obtain the frequency fitting lines of the data volume in each spectral signal of each wood board sample, and obtain the second eigenvalue of all wood board samples at the single sampling frequency according to the slope of each frequency fitting line of all wood board samples and the residuals corresponding to all wood board samples in each frequency fitting line at the single sampling frequency; According to the average level of the squared residuals corresponding to each wood board sample in all moisture fitting lines at the single sampling frequency, and the residuals corresponding to the single sampling frequency of each wood board sample in the frequency fitting lines corresponding to each spectral signal, obtain the comprehensive interference coefficient of each wood board sample at the single sampling frequency.

[0009] Obtain the standard frequency according to the average level of the average retention coefficient, the first eigenvalue, and the second eigenvalue of all wood board samples at each sampling frequency; According to the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency, combined with the moisture content of each wood board sample and the attenuation rate and phase shift amount at the standard frequency, obtain the calibration equation of the wood board, and then detect the moisture content of the wood board to be measured.

[0010] Preferably, the process of obtaining the average retention coefficient of a single wood board sample at a single sampling frequency is as follows: Denote the reciprocal of the absolute value of the difference between the data volume corresponding to the single sampling frequency in the smoothed spectral signal of the single wood board sample and the data volume corresponding to the single sampling frequency in the unsmoothed spectral signal as the smoothing retention coefficient of the single wood board sample at the single sampling frequency under the single spectral signal; Denote the mean of the normalized results of the smoothing retention coefficients of all spectral signals of the single wood board sample at the single sampling frequency as the average retention coefficient of the single wood board sample at the single sampling frequency.

[0011] Preferably, the process of obtaining the first eigenvalue of all wood board samples at the single sampling frequency is as follows:

[0012] When the slope of the fitting line is greater than 0, equal to 0, or less than 0, respectively take the preset first constant a, the preset second constant b, and the preset third constant c as the slope sign values of the fitting line, where a > b > c and all are positive numbers;

[0013] Denote the ratio of the slope sign value of the single moisture fitting line at the single sampling frequency to the sum of the squared residuals corresponding to it as the moisture proportional eigenvalue of the single spectral signal of all wood board samples at the single sampling frequency.

[0014] The mean of the normalization results of the moisture proportional eigenvalues of all class spectrum signals of all wood board samples at a single sampling frequency is denoted as the first eigenvalue of all wood board samples at the single sampling frequency.

[0015] Preferably, the calculation formula for the second eigenvalue of all wood board samples at a single sampling frequency is: In the formula, F p is the second eigenvalue of all wood board samples at the sampling frequency p, H is the total number of categories of spectrum signals, N is the total number of wood board samples, s p,q,i represents the frequency proportional eigenvalue of the q-th spectrum signal of the i-th wood board sample at the sampling frequency p; among them, the process of obtaining the frequency proportional eigenvalue of a single spectrum signal of a single wood board sample at a single sampling frequency is: the ratio of the slope sign value of the frequency fitting line corresponding to the single wood board sample under the single spectrum signal to the residual square of the single sampling frequency in the frequency fitting line is denoted as the frequency proportional eigenvalue of the single spectrum signal of the single wood board sample at the single sampling frequency.

[0016] Preferably, the process of obtaining the comprehensive interference coefficient of each wood board sample at the single sampling frequency is:

[0017] The residual square of a single data volume in the single moisture fitting line at the single sampling frequency is denoted as the moisture interference coefficient of the corresponding single wood board sample in a single class of spectrum signals at the single sampling frequency; the mean of the normalization results of the moisture interference coefficients of each wood board sample at the single sampling frequency in all classes of spectrum signals is denoted as the first interference coefficient of each wood board sample at the single sampling frequency.

[0018] The sum of the residual squares corresponding to the single sampling frequency of a single wood board sample in the frequency fitting lines of the corresponding spectrum signals is denoted as the frequency interference coefficient of the single wood board sample at the single sampling frequency; the normalization result of the frequency interference coefficients of each wood board sample at the single sampling frequency is denoted as the second interference coefficient of each wood board sample at the single sampling frequency.

[0019] The mean of the first interference coefficient and the second interference coefficient of each wood board sample at the single sampling frequency is denoted as the comprehensive interference coefficient of each wood board sample at the single sampling frequency.

[0020] Preferably, the process of obtaining the standard frequency is:

[0021] The mean of the first eigenvalue and the second eigenvalue of all wood board samples at a single sampling frequency is denoted as the comprehensive eigenvalue of all wood board samples at the single sampling frequency.

[0022] The mean of the average retention coefficients of all wood board samples at a single sampling frequency and the sum of the comprehensive characteristic values corresponding to the single sampling frequency are denoted as the frequency selection coefficient of all wood board samples at the single sampling frequency;

[0023] The sampling frequency corresponding to the maximum frequency selection coefficient among all sampling frequencies is denoted as the standard frequency.

[0024] Preferably, the specific process for obtaining the calibration equation of the wood board is as follows:

[0025] The ratio between the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency is denoted as the confidence level of each wood board sample; taking the attenuation amount and phase shift amount of all wood board samples at the standard frequency as the X and Y coordinates, and the moisture content of all wood board samples as the Z coordinate to construct a three-dimensional coordinate system, using a three-dimensional line fitting algorithm based on the weighted least squares method to perform line fitting on all data points in the three-dimensional coordinate system, where the confidence levels of each wood board sample are respectively used as the weights of the corresponding data points of each wood board sample in the three-dimensional line fitting algorithm based on the weighted least squares method, to obtain the calibration equation of the wood board under the current specification: Z = f(X, Y), where Z represents the moisture content of the wood board, and X and Y respectively represent the attenuation rate and phase shift amount of the wood board at the standard frequency.

[0026] Preferably, the specific process for detecting the moisture content of the wood board to be measured is as follows: substituting the attenuation amount and phase shift amount of the wood board to be measured under the current specification at the standard frequency into the calibration equation to obtain the detection result of the moisture content of the wood board to be measured.

[0027] In a second aspect, an embodiment of the present application provides a device for detecting the moisture content of a wood board, and the moisture content detection device includes:

[0028] A data acquisition module, configured to acquire the attenuation spectrum signal, phase shift spectrum signal, and moisture content of each wood board sample;

[0029] A data processing module, configured to analyze the characteristics of the spectrum signals of the wood board samples, obtain the average retention coefficient of a single wood board sample at a single sampling frequency, and combine the spectrum characteristics of the wood board samples at each sampling frequency to obtain the standard frequency, and further obtain the calibration equation of the wood board;

[0030] A moisture content detection module, configured to obtain the moisture content of the wood board to be measured according to the attenuation amount and phase shift amount of the wood board to be measured at the standard frequency and the calibration equation.

[0031] In a third aspect, an embodiment of the present application further provides a moisture content detection device for a wooden board. The system includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the moisture content detection method for a wooden board described in any one of the above are implemented.

[0032] As can be seen from the above embodiments, the moisture content detection method, detection device, and detection apparatus for a wooden board provided by the embodiments of the present application have at least the following beneficial effects:

[0033] 1. The present application uses the frequency selection coefficient constructed based on the obtained average retention coefficient and comprehensive eigenvalue to screen out the standard frequency for subsequent construction of the calibration equation. It considers the overall retention degree of the data information carried by the attenuation amount and phase shift amount in the microwave signals received by the transmission microwave radar moisture sensor from all wooden board samples during data smoothing processing, and the characteristics of the attenuation amount and phase shift amount at each sampling frequency in the microwave signal that are proportional to the moisture content of the wooden board samples and the microwave signal frequency. It can effectively obtain the attenuation amount and phase shift amount at a sampling frequency with the highest retention degree and the least influence from noise components from the microwave signals of all wooden board samples, so as to minimize the influence of noise in the microwave signal on the subsequent construction of the calibration equation and improve the accuracy of the calibration equation.

[0034] 2. The present application obtains the confidence level of each wooden board sample according to the smoothing retention coefficient and comprehensive interference coefficient, and assigns different weights to the attenuation amount and phase shift amount of each wooden board sample at the standard frequency subsequently. It can effectively evaluate the accuracy of the attenuation amount and phase shift amount of each wooden board sample used in the subsequent construction of the calibration equation, improve the reliability of the subsequently constructed calibration equation, and thus accurately detect the moisture content of wooden boards of the same specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a flowchart of the steps of a moisture content detection method for a wooden board provided by an embodiment of the present application;

[0037] Figure 2 It is a schematic structural diagram of a moisture content detection device for a wooden board provided by an embodiment of the present application. Detailed implementation manners

[0038] In order to further elaborate on the technical means and effects adopted by the present application to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and effects of a method, a detection device and a detection apparatus for detecting the moisture content of a wood board proposed according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0039] Unless otherwise specified and limited, terms such as "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a circuit structure, an article or a device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such an article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element 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 of the related listed items. All technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs.

[0040] The following specifically describes the specific solutions of a method, a detection device and a detection apparatus for detecting the moisture content of a wood board provided by the present application with reference to the accompanying drawings.

[0041] Please refer to Figure 1 , which shows a flowchart of the steps of a method for detecting the moisture content of a wood board provided by an embodiment of the present application. The method includes the following steps:

[0042] Step 1: Obtain the attenuation spectrum signal, phase shift spectrum signal and moisture content of each wood board sample.

[0043] The present application accurately detects the moisture content of wood boards of different specifications by constructing a calibration equation for each wood board under different specifications, so as to avoid the situation that wood boards with the same moisture content are measured to have different moisture contents when using the same calibration equation due to different attenuations and phase shifts of the same microwave signal.

[0044] This embodiment takes the moisture content detection of a certain specification of wood board as an example for the following analysis. First, the staff humidifies the wood board. During the humidification process, a resistive humidity sensor is used to monitor the moisture content of the wood board, and multiple wood board samples with a certain moisture content increment at a certain interval are obtained under the current specification. In this embodiment, the number of the wood board samples is 10, and the moisture content interval is 5%, which can be set by the implementer himself.

[0045] The attenuation spectrum signal and the phase shift spectrum signal of each wood board sample are respectively obtained by using the vector detection module in the transmissive microwave radar moisture sensor. The attenuation spectrum signal and the phase shift spectrum signal are obtained by comparing the microwave signal penetrating the wood board sample received by the transmissive microwave radar moisture sensor with the microwave signal it emits. Among them, the horizontal and vertical coordinates of the attenuation spectrum signal are frequency and attenuation amount respectively, and the horizontal and vertical coordinates of the phase shift spectrum signal are frequency and phase shift amount respectively. At the same time, the drying and weighing method is used to accurately obtain the moisture content of each wood board sample. It should be noted that the resistive humidity sensor can only roughly detect the moisture content of the wood board and cannot accurately detect the moisture content of the wood board. Using the drying and weighing method can accurately obtain the moisture content of the wood board. Therefore, using the drying and weighing method helps to improve the accuracy of the subsequent calibration equation construction.

[0046] Among them, the frequency range of the microwave signal used in the transmissive microwave radar moisture sensor is 8 GHz - 12 GHz, and the frequency step interval is 20 MHz, which can be set by the implementer himself.

[0047] So far, the attenuation spectrum signal, the phase shift spectrum signal and the moisture content of each wood board sample are obtained.

[0048] Step 2: Denote both the attenuation spectrum signal and the phase shift spectrum signal as spectrum signals; according to the average level of the difference between the data amounts of all spectrum signals of a single wood board sample before and after smoothing processing at a single sampling frequency, obtain the average retention coefficient of the single wood board sample at the single sampling frequency.

[0049] Since the attenuation spectrum signal and the phase shift spectrum signal are obtained by comparing the transmitted and received microwave signals collected by a transmissive microwave radar moisture sensor, and the microwave signal is affected by various noises during the signal collection and transmission processes, such as thermal noise, amplifier noise, and environmental noise, etc., this will introduce redundant or irrelevant information in the collected microwave signal at inferior frequencies, thereby affecting the accuracy of the data in the obtained attenuation spectrum signal and phase shift spectrum signal. Therefore, in this application, a suitable frequency is selected to minimize the degree of noise interference on the attenuation and phase shift amounts of all obtained attenuation spectrum signals and phase shift spectrum signals at this frequency, and different weights are assigned to the attenuation and phase shift amounts of all wood board samples at this frequency to construct the final calibration equation, so as to reduce the influence of the redundant or irrelevant information introduced by the noise in the microwave signal at its inferior frequencies on the finally constructed calibration equation.

[0050] The Savitzky-Golay (SG) smoothing filter algorithm is used to smooth the attenuation spectrum signal and the phase shift spectrum signal of each wood board sample respectively, so as to reduce the influence of the noise information carried therein on the subsequent construction of the calibration equation, and the smoothed attenuation spectrum signal and phase shift spectrum signal of each wood board sample are obtained respectively. The SG smoothing filter algorithm is a well-known technology, and the specific process will not be elaborated.

[0051] Both the attenuation spectrum signal and the phase shift spectrum signal are denoted as the spectrum signal. The attenuation amount or the phase shift amount in the spectrum signal is denoted as the data amount. Taking any sampling frequency p in the frequency range of the microwave signal used in the transmissive microwave radar moisture sensor as an example, the reciprocal of the absolute value of the difference between the data amount corresponding to the sampling frequency p in the smoothed spectrum signal of a single wood board sample and the data amount corresponding to the sampling frequency p in the unsmoothed spectrum signal is denoted as the smoothing retention coefficient of the single spectrum signal of the single wood board sample at the sampling frequency p, which is used to evaluate the degree of retention of the data information carried by the data corresponding to the sampling frequency p in the spectrum signal of the wood board sample M after smoothing.

[0052] The Min-Max normalization method is used to normalize all the smoothing retention coefficients of all sampling frequencies. The mean value of the normalization results of the smoothing retention coefficients of the sampling frequency p under all spectrum signals is denoted as the average retention coefficient of the wood board sample M at the sampling frequency p, which is used to evaluate the overall degree of retention of the data information carried by the data corresponding to the sampling frequency p in the attenuation spectrum signal and the phase shift spectrum signal of the wood board sample M after smoothing. The Min-Max normalization method is a well-known technology, and the specific process will not be elaborated.

[0053] Step 3: Obtain the moisture fitting lines of the data volume corresponding to the single sampling frequency of all wood board samples under various spectral signals, and obtain the first eigenvalue of all wood board samples at the single sampling frequency according to the slopes of the moisture fitting lines and the differences between the actual values and the fitting values corresponding to the moisture fitting lines; obtain the frequency fitting lines of the data volume in the spectral signals of each wood board sample, and obtain the second eigenvalue of all wood board samples at the single sampling frequency according to the slopes of the frequency fitting lines of all wood board samples and the residuals corresponding to all wood board samples in the frequency fitting lines at the single sampling frequency; according to the average level of the squared residuals corresponding to each wood board sample in all moisture fitting lines at the single sampling frequency and the residuals corresponding to the single sampling frequency of each wood board sample in the frequency fitting lines corresponding to the spectral signals, obtain the comprehensive interference coefficient of each wood board sample at the single sampling frequency.

[0054] Since the attenuation and phase shift generated by the microwave signal inside the wood board sample are usually only related to the wavelength of the microwave signal and the thickness and dielectric constant of the wood board sample, where both the attenuation and phase shift are inversely proportional to the wavelength and directly proportional to the thickness and dielectric constant. In the wood board under the current specification, the thickness of the wood board sample is fixed, and at high-frequency electromagnetic waves, moisture mainly determines the dielectric constant of the wood board sample, so that the dielectric constant of the wood board sample increases with the increase of its moisture content, which in turn leads to the attenuation and phase shift of the microwave signal inside different wood board samples being directly proportional to the moisture content of the wood board sample. When an electromagnetic wave propagates in a given medium, the wavelength and frequency are inversely proportional to each other, so that the attenuation and phase shift of the microwave signal received by the sensor inside the wood board sample are also directly proportional to the frequency of the microwave signal, that is, the attenuation and phase shift of the microwave signals received from all wood board samples by the sensor at the same frequency are directly proportional to the moisture content of the wood board sample, and the attenuation and phase shift of the microwave signal received by the sensor inside the wood board sample are directly proportional to the frequency of the microwave signal, while the noise in the microwave signal will destroy these characteristics.

[0055] Based on the above analysis, taking the moisture content of all wood board samples as the abscissa and taking all data amounts corresponding to a single sampling frequency in the single-class frequency spectrum signals of all wood board samples after smoothing processing (where the data amount refers to the attenuation amount or phase shift amount) as the ordinate, a linear fitting algorithm based on the least squares method is used to perform linear fitting on all data amounts corresponding to a single sampling frequency of all wood board samples under various frequency spectrum signals. The fitting straight lines of a single sampling frequency of all wood board samples under various frequency spectrum signals obtained are denoted as moisture fitting straight lines. When the slope of the fitting straight line is greater than 0, equal to 0, or less than 0, the preset first constant a, the preset second constant b, and the preset third constant c are respectively taken as the slope symbol values of the fitting straight line, where a > b > c and all are positive numbers. In this embodiment, the values of a, b, and c are taken as 3, 2, and 1 respectively, and the implementer can take values by himself / herself.

[0056] The ratio of the slope symbol value of a single moisture fitting straight line at a single sampling frequency to the corresponding sum of squared residuals is denoted as the moisture proportionality eigenvalue of the single-class frequency spectrum signal of all wood board samples at the single sampling frequency, which is used to evaluate whether the attenuation amount or phase shift amount of the microwave signals of all wood board samples at the single sampling frequency has the characteristic of being proportional to the moisture content of the wood board samples. It should be noted that when the sum of squared residuals corresponding to the moisture fitting straight line is 0, the sum of squared residuals corresponding to the moisture fitting straight line is set equal to the preset first constant. In this embodiment, the preset first constant is taken as 0.01.

[0057] The sum of squared residuals of a single data amount in a single moisture fitting straight line at a single sampling frequency is denoted as the moisture interference coefficient of the corresponding single wood board sample in the single-class frequency spectrum signal at the single sampling frequency, which is used to evaluate the interference degree of the noise component in the microwave signals received by the sensor from each wood board sample on the characteristic that the attenuation amount or phase shift amount at the single sampling frequency is proportional to the moisture content of the wood board sample. The linear fitting algorithm based on the least squares method is a well-known technology, and the specific process will not be elaborated here.

[0058] The moisture proportional eigenvalues of all class spectrum signals at all sampling frequencies are normalized using the Min-Max normalization method, and at the same time, the moisture interference coefficients of all wood board samples at all sampling frequencies in all class spectrum signals are normalized. The mean of the normalization results of the moisture proportional eigenvalues of all class spectrum signals of all wood board samples at a single sampling frequency is denoted as the first eigenvalue of all wood board samples at a single sampling frequency, which is used to evaluate whether the attenuation amount and phase shift amount of the microwave signals of all wood board samples at a single sampling frequency are both characteristic of being proportional to the moisture content of the wood board samples. The mean of the normalization results of the moisture interference coefficients of each wood board sample at all class spectrum signals at a single sampling frequency is denoted as the first interference coefficient of each wood board sample at a single sampling frequency, which is used to evaluate the overall interference degree of the attenuation amount and phase shift amount of the noise components in the microwave signals of each wood board sample at a single sampling frequency being proportional to the moisture content. Among them, the Min-Max normalization method is a well-known technology, and the specific process will not be elaborated.

[0059] Furthermore, a linear fitting algorithm based on the least squares method is used to linearly fit the data amounts corresponding to all frequencies in the spectrum signals of each wood board sample, and the fitting straight lines of the spectrum signals of each wood board sample obtained are denoted as frequency fitting straight lines. The ratio of the slope symbol value of the frequency fitting straight line corresponding to a single wood board sample in a single spectrum signal to the sum of the squares of the residuals of a single sampling frequency in the frequency fitting straight line is denoted as the frequency proportional eigenvalue of the single spectrum signal of the single wood board sample at the single sampling frequency, which is used to evaluate whether the attenuation amount or phase shift amount of the microwave signal of the single wood board sample at the single sampling frequency is characteristic of being proportional to the microwave signal frequency. It should be noted that when the sum of the squares of the residuals of a single sampling frequency of a single wood board sample in the frequency fitting straight line is 0, the sum of the squares of the residuals of this sampling frequency of this wood board sample in the frequency fitting straight line is set to a preset second constant. In this embodiment, the value of the preset second constant is 0.1.

[0060] At the same time, the sum of the squares of the residuals corresponding to a single sampling frequency of a single wood board sample in the frequency fitting straight lines of the corresponding spectrum signals is denoted as the frequency interference coefficient of the single wood board sample at the single sampling frequency, which is used to evaluate the interference degree of the noise components in the microwave signal of the single wood board sample on the characteristic that the attenuation amount and phase shift amount at the single sampling frequency are proportional to the microwave signal frequency. Among them, the linear fitting algorithm based on the least squares method is a well-known technology, and the specific process will not be elaborated.

[0061] The frequency proportional eigenvalues of all sampling frequencies of all wood board samples in all spectrum signals are normalized using the Min-Max normalization method, and at the same time, the frequency interference coefficients of all wood board samples at all sampling frequencies are normalized.

[0062] As a preferred embodiment, according to the average level of the frequency proportional eigenvalues of all spectral signals of all wood board samples at a single sampling frequency, the second eigenvalue of all wood board samples at the single sampling frequency is obtained, which is used to evaluate the significant degree that the attenuation amount and phase shift amount of the microwave signals of all wood board samples at the single sampling frequency are proportional to the microwave signal frequency.

[0063] In this embodiment, the second eigenvalue of all wood board samples at the sampling frequency p is denoted as F p , and its specific expression is: In the formula, F p is the second eigenvalue of all wood board samples at the sampling frequency p, H is the total number of categories of spectral signals, N is the total number of wood board samples, and s p,q,i represents the frequency proportional eigenvalue of the qth spectral signal of the ith wood board sample at the sampling frequency p. The larger the value of F p , the more obvious the characteristics that the attenuation amount and phase shift amount at the sampling frequency p are both proportional to the microwave signal frequency.

[0064] The normalization result of the frequency interference coefficient of each wood board sample at the single sampling frequency is denoted as the second interference coefficient of each wood board sample at the single sampling frequency, which is used to evaluate the interference degree of the noise component in the microwave signal of each wood board sample on the overall characteristics that the attenuation amount and phase shift amount at the single sampling frequency are proportional to the microwave signal frequency. Among them, the Min-Max normalization method is a well-known technology, and the specific process will not be elaborated.

[0065] The mean value of the first eigenvalue and the second eigenvalue of all wood board samples at the single sampling frequency is denoted as the comprehensive eigenvalue of all wood board samples at the single sampling frequency, which is used to evaluate whether the attenuation amount and phase shift amount of the microwave signals of all wood board samples at the single sampling frequency both have the characteristics of being proportional to the moisture content of the wood board samples and the microwave signal frequency. The mean value of the first interference coefficient and the second interference coefficient of each wood board sample at the single sampling frequency is denoted as the comprehensive interference coefficient of each wood board sample at the single sampling frequency, which is used to evaluate the interference degree of the noise component in the microwave signal of each wood board sample on the overall characteristics that the attenuation amount and phase shift amount at the single sampling frequency are proportional to the moisture content of the wood board samples and the microwave signal frequency.

[0066] Step four: Obtain the standard frequency according to the average level of the average retention coefficients of all wood board samples at each sampling frequency, the first eigenvalue, and the second eigenvalue; according to the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency, combined with the moisture content of each wood board sample and the attenuation rate and phase shift amount at the standard frequency, obtain the calibration equation of the wood board, and then detect the moisture content of the wood board to be measured.

[0067] As a preferred embodiment, in this embodiment, the mean of the average retention coefficients of all wood board samples at a single sampling frequency and the sum of the comprehensive characteristic values corresponding to the single sampling frequency are denoted as the frequency selection coefficient of all wood board samples at the single sampling frequency. The larger the frequency selection coefficient, the more the attenuation amount and phase shift amount of the microwave signals of all wood board samples at the single sampling frequency should be used in the construction of the subsequent calibration equation, so as to reduce the overall loss degree of the data information carried by the attenuation amount and phase shift amount in the microwave signals during data smoothing processing, and reduce the influence of the residual noise information in the microwave signals on the accuracy of the attenuation amount and phase shift amount used for constructing the subsequent calibration equation in the microwave signals.

[0068] The sampling frequency corresponding to the largest frequency selection coefficient among all sampling frequencies is denoted as the standard frequency, which is used to construct the calibration equation of the wood board under the current specification subsequently.

[0069] The ratio between the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency is denoted as the confidence level of each wood board sample, which is used to evaluate the accuracy of the data information carried by the attenuation amount and phase shift amount of the microwave signal of each wood board sample used in the construction of the subsequent calibration equation.

[0070] Furthermore, the attenuation amount and phase shift amount corresponding to the standard frequency in the smoothed attenuation spectrum signal and phase shift spectrum signal of each wood board sample are respectively obtained, and are denoted as the attenuation amount and phase shift amount of each wood board sample at the standard frequency.

[0071] Taking the attenuation amount and phase shift amount of all wood board samples at the standard frequency as the X and Y coordinates, and taking the moisture content of all wood board samples as the Z coordinate to construct a three-dimensional coordinate system, using a three-dimensional linear fitting algorithm based on the weighted least squares method to perform linear fitting on all data points in the three-dimensional coordinate system, where the confidence level of each wood board sample is respectively used as the weight of the corresponding data point of each wood board sample in the three-dimensional linear fitting algorithm based on the weighted least squares method, to obtain a calibration equation for measuring the moisture content of the wood board under the current specification with respect to the attenuation amount and phase shift amount: Z = f(X, Y), where Z represents the moisture content of the wood board, and X and Y respectively represent the attenuation rate and phase shift amount of the wood board at the standard frequency. The higher the accuracy of the data information carried by the attenuation amount and phase shift amount of the microwave signal received by the transmission type microwave radar moisture sensor from a single wood board sample at the standard frequency, that is, the greater the confidence level of the single wood board sample, the greater the weight of the corresponding data point of the wood board sample in the three-dimensional coordinate system during the linear fitting of the data points in the three-dimensional coordinate system. The three-dimensional linear fitting algorithm based on the weighted least squares method is a well-known technology, and the specific process will not be elaborated here.

[0072] Obtain the attenuation amount and phase shift amount of the wooden board to be measured under the current specification at the standard frequency, and use the Z coordinate value of the corresponding data point of the obtained attenuation amount and phase shift amount in the calibration equation as the moisture content detection result of the wooden board to be measured, thereby completing the detection of the moisture content of the wooden board to be measured under the current specification.

[0073] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of a moisture content detection device for wooden boards provided by an embodiment of the present application. In this embodiment, each unit included in the terminal is used to execute each step in the corresponding embodiment of a method for detecting the moisture content of wooden boards. Refer to Figure 2 , the load flexible adjustment device includes: a data acquisition module, a data processing module, and a moisture content detection module.

[0074] The data acquisition module is used to obtain the attenuation spectrum signal, phase shift spectrum signal, and moisture content of each wooden board sample;

[0075] The data processing module is used to analyze the characteristics of the spectrum signal of the wooden board sample, obtain the average retention coefficient of a single wooden board sample at a single sampling frequency, and combine the spectrum characteristics of the wooden board sample at each sampling frequency to obtain the standard frequency, and then obtain the calibration equation of the wooden board;

[0076] The moisture content detection module is used to obtain the moisture content of the wooden board to be measured according to the attenuation amount and phase shift amount of the wooden board to be measured at the standard frequency, and the calibration equation.

[0077] Based on the same inventive concept as the above method, an embodiment of the present application also provides a moisture content detection device for wooden boards, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the method for detecting the moisture content of wooden boards described in any one of the above.

[0078] Each embodiment in the present application is described in a progressive manner. The same or similar parts between each embodiment can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

[0079] It should be noted that, unless otherwise specified or limited, terms such as "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the article or device comprising said element. Additionally, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0080] Those skilled in the art will readily conceive of 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 general knowledge or conventional technical means in the technical field not invented by the present application.

[0081] It should be understood that the present application is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A method for detecting the moisture content of a wooden board, characterized in that, The method includes the following steps: Obtain the attenuation spectrum signal, phase shift spectrum signal, and moisture content of each wood board sample; Both the attenuation spectrum signal and the phase shift spectrum signal are denoted as spectrum signals; according to the average level of the difference between the data amounts of all spectrum signals of a single wood board sample at a single sampling frequency before and after smoothing processing, obtain the average retention coefficient of the single wood board sample at the single sampling frequency; Obtain the moisture fitting straight line of the data amount corresponding to the single sampling frequency of all wood board samples under various spectrum signals, and obtain the first eigenvalue of all wood board samples at the single sampling frequency according to the slope of each moisture fitting straight line and the difference between the actual value and the fitted value corresponding to each moisture fitting straight line; obtain the frequency fitting straight line of the data amount in each spectrum signal of each wood board sample, and obtain the second eigenvalue of all wood board samples at the single sampling frequency according to the slope of each frequency fitting straight line of all wood board samples and the residuals corresponding to each frequency fitting straight line of all wood board samples at the single sampling frequency; according to the average level of the sum of the squares of the residuals corresponding to each wood board sample in all moisture fitting straight lines at the single sampling frequency and the residuals corresponding to the single sampling frequency of each wood board sample in the frequency fitting straight lines corresponding to each spectrum signal, obtain the comprehensive interference coefficient of each wood board sample at the single sampling frequency; Obtain the standard frequency according to the average level of the average retention coefficients, the first eigenvalue, and the second eigenvalue of all wood board samples at each sampling frequency; according to the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency, combined with the moisture content of each wood board sample and the attenuation rate and phase shift amount at the standard frequency, obtain the calibration equation of the wood board, and then detect the moisture content of the wood board to be measured.

2. The moisture content detection method of a wood board according to claim 1, characterized in that, The process of obtaining the average retention coefficient of the single wood board sample at the single sampling frequency is as follows: Denote the reciprocal of the absolute value of the difference between the data amount corresponding to the single sampling frequency in the spectrum signal after smoothing processing of the single wood board sample and the data amount corresponding to the single sampling frequency in the spectrum signal without smoothing processing as the smoothing retention coefficient of the single wood board sample at the single sampling frequency under the single spectrum signal; Denote the mean of the normalized results of the smoothing retention coefficients of all spectrum signals of the single wood board sample at the single sampling frequency as the average retention coefficient of the single wood board sample at the single sampling frequency.

3. The moisture content detection method of a wood board according to claim 1, wherein, The process of obtaining the first eigenvalue of all wood board samples at the single sampling frequency is as follows: When the slope of the fitting straight line is greater than 0, equal to 0, or less than 0, respectively use the preset first constant a, preset second constant b, and preset third constant c as the slope sign value of the fitting straight line, where a > b > c and all are positive numbers; Denote the ratio of the slope sign value of the single moisture fitting straight line at the single sampling frequency to the sum of the squares of its corresponding residuals as the moisture proportional eigenvalue of the single type of spectrum signal of all wood board samples at the single sampling frequency; Denote the mean of the normalized results of the moisture proportional eigenvalues of all types of spectrum signals of all wood board samples at the single sampling frequency as the first eigenvalue of all wood board samples at the single sampling frequency.

4. The moisture content detection method of a wood board according to claim 3, wherein The calculation formula for the second eigenvalue of all the wood board samples at a single sampling frequency is as follows: In the formula, F p is the second eigenvalue of all the wood board samples at the sampling frequency p, H is the total number of categories of the spectrum signals, N is the total number of the wood board samples, and s p,q,i represents the frequency proportional eigenvalue of the q-th spectrum signal of the i-th wood board sample at the sampling frequency p; among them, the process of obtaining the frequency proportional eigenvalue of a single spectrum signal of a single wood board sample at a single sampling frequency is: taking the ratio of the slope sign value of the frequency fitting straight line corresponding to the single wood board sample under the single spectrum signal to the residual square of the single sampling frequency in the frequency fitting straight line as the frequency proportional eigenvalue of the single spectrum signal of the single wood board sample at the single sampling frequency.

5. The moisture content detection method of a wooden board according to claim 1, characterized in that, The process of obtaining the comprehensive interference coefficient of each wood board sample at a single sampling frequency is as follows: Denote the sum of squared residuals of a single data volume in a single moisture fitting line at a single sampling frequency as the moisture interference coefficient of the corresponding single wood board sample in a single type of frequency spectrum signal at the single sampling frequency; Denote the mean of the normalization results of the moisture interference coefficients of each wood board sample in all types of frequency spectrum signals at a single sampling frequency as the first interference coefficient of each wood board sample at the single sampling frequency. Denote the sum of squared residuals corresponding to the single sampling frequency of a single wood board sample in the frequency fitting lines of the corresponding frequency spectrum signals as the frequency interference coefficient of the single wood board sample at the single sampling frequency; Denote the normalization result of the frequency interference coefficients of each wood board sample at the single sampling frequency as the second interference coefficient of each wood board sample at the single sampling frequency. Denote the mean of the first interference coefficient and the second interference coefficient of each wood board sample at a single sampling frequency as the comprehensive interference coefficient of each wood board sample at the single sampling frequency.

6. The moisture content detection method of a wooden board according to claim 1, characterized in that, The process of obtaining the standard frequency is as follows: Denote the mean of the first eigenvalue and the second eigenvalue of all wood board samples at a single sampling frequency as the comprehensive eigenvalue of all wood board samples at the single sampling frequency. Denote the sum of the mean of the average retention coefficients of all wood board samples at a single sampling frequency and the comprehensive eigenvalue corresponding to the single sampling frequency as the frequency selection coefficient of all wood board samples at the single sampling frequency. Denote the sampling frequency corresponding to the largest frequency selection coefficient among all sampling frequencies as the standard frequency.

7. The moisture content detection method of a wooden board as claimed in claim 1, wherein, The specific process of obtaining the calibration equation of the wood board is as follows: Denote the ratio between the average retention coefficient and the comprehensive interference coefficient of each wood board sample at the standard frequency as the confidence level of each wood board sample; Construct a three-dimensional coordinate system with the attenuation amount and phase shift amount of all wood board samples at the standard frequency as the X and Y coordinates and the moisture content of all wood board samples as the Z coordinate, and use a three-dimensional line fitting algorithm based on the weighted least squares method to perform line fitting on all data points in the three-dimensional coordinate system, where the confidence levels of each wood board sample are used as the weights of the corresponding data points of each wood board sample in the three-dimensional line fitting algorithm based on the weighted least squares method, to obtain the calibration equation of the wood board under the current specification: Z = f(X, Y), where Z represents the moisture content of the wood board, and X and Y represent the attenuation rate and phase shift amount of the wood board at the standard frequency respectively.

8. The moisture content detection method of a wooden board according to claim 1, characterized in that, The specific process of detecting the moisture content of the wood board to be measured is as follows: Substitute the attenuation amount and phase shift amount of the wood board to be measured under the current specification at the standard frequency into the calibration equation to obtain the detection result of the moisture content of the wood board to be measured.

9. A moisture content detection device for a wooden board, characterized in that, Implement a method for detecting the moisture content of a wood board as described in any one of claims 1-8, and the moisture content detection device includes: A data acquisition module for obtaining the attenuation frequency spectrum signal, phase shift frequency spectrum signal and moisture content of each wood board sample. A data processing module, which is used to analyze the characteristics of the frequency spectrum signal of the wood board sample, obtain the average retention coefficient of a single wood board sample at a single sampling frequency, and combine the frequency spectrum characteristics of the wood board sample at each sampling frequency to obtain a standard frequency, and further obtain a calibration equation for the wood board; A moisture content detection module, which is used to obtain the moisture content of the wood board to be measured according to the attenuation amount and phase shift amount of the wood board to be measured at the standard frequency and the calibration equation.

10. A moisture content detection device for a wooden board, 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, it implements a method for detecting the moisture content of a wood board according to any one of claims 1-8.

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