Method and system for detecting water content of material based on dual-wavelength infrared light

Abstract

The invention provides a material water content detection method and system based on dual-wavelength infrared light, and relates to the technical field of material detection.The method comprises the steps that an infrared light source is controlled to emit at least two infrared light of different wavelengths to irradiate the surface of a to-be-detected material; receiving reflected light signals of the surface of the to-be-detected material to the infrared light, and acquiring light intensity information of the reflected light signals corresponding to different wavelengths; the average absorbance value of the water content characteristic of the to-be-detected material is constructed according to the ratio relation between the light intensity information of different wavelengths; and performing environmental disturbance compensation on the average absorbance value to obtain a compensated average absorbance value, and inputting the compensated average absorbance value into a preset calibration model to output the water content of the to-be-detected material. According to the scheme, the stability and the reliability of the water content detection of the material in an actual application environment are improved, and the problem of measurement errors caused by environmental changes is solved.

Description

A method and system for detecting the moisture content of materials based on dual-wavelength infrared light Technical Field

[0001] This application relates to the technical field of material detection, and in particular to a method and system for detecting the moisture content of materials based on dual-wavelength infrared light. Background Technology

[0002] Moisture content is a key quality control indicator in industries such as grain storage, feed processing, timber processing, tobacco processing, and chemical raw material handling. Moisture content not only affects the storage safety and processing stability of materials but also directly relates to product quality, energy consumption control, and production costs. Therefore, accurate detection of moisture content has become a critical issue requiring research and resolution.

[0003] In existing solutions, dual-wavelength infrared light is often used to irradiate the material. One wavelength is set as the moisture absorption sensitive band, and the other wavelength is set as the relatively insensitive band as the reference band. By detecting the reflection or transmission intensity of the material to the two wavelengths of infrared light, and calculating the intensity ratio or difference between the two, and then combining it with a pre-established calibration curve, the moisture content of the material can be estimated quickly.

[0004] Although the dual-wavelength intensity ratio calculation can achieve rapid measurement of material moisture content under ideal conditions, in actual industrial applications, when the ambient temperature changes or the measurement distance between the sensor and the material fluctuates, the infrared light intensity will change accordingly, resulting in a deviation in the ratio result and thus affecting the accuracy of the moisture content calculation, leading to insufficient stability of the detection results. Summary of the Invention

[0005] To overcome measurement errors caused by environmental changes, this application provides a method and system for detecting material moisture content based on dual-wavelength infrared light. By compensating for environmental disturbances in the absorbance results, the stability and accuracy of moisture content detection are improved.

[0006] On one hand, the present invention provides a method for detecting the moisture content of materials based on dual-wavelength infrared light, comprising: controlling an infrared light source to emit infrared light of at least two different wavelengths and irradiating the surface of the material to be tested with the infrared light; receiving the reflected light signals of the surface of the material to be tested to each of the infrared lights, and acquiring the light intensity information of each reflected light signal corresponding to different wavelengths; constructing an average absorbance value of the moisture content characteristics of the material to be tested by means of the ratio relationship between the light intensity information of different wavelengths; performing environmental disturbance compensation on the average absorbance value to obtain a compensated average absorbance value, wherein the environmental disturbance compensation includes correcting the signal deviation caused by temperature changes and / or measurement distance changes; and inputting the compensated average absorbance value into a preset calibration model to output the moisture content of the material to be tested.

[0007] Optionally, the step of controlling the infrared light source to emit infrared light of at least two different wavelengths and irradiating the surface of the material to be tested includes: the control IC outputting driving pulse signals with preset frequencies and duty cycles to the first and second infrared light-emitting diodes of the infrared light source respectively; using the driving pulse signals to alternately turn on the first and second infrared light-emitting diodes according to a preset timing sequence, so that either the first or second infrared light-emitting diode is in a luminous state at any time, resulting in a sequence of light pulses that are spaced apart; and converging the outgoing light paths of the first and second infrared light-emitting diodes through the same optical collimating component, and irradiating the same measurement area on the surface of the material to be tested with a preset fixed outgoing angle and the light pulse sequence.

[0008] Optionally, the step of receiving the reflected light signals of each infrared light from the surface of the material to be tested and obtaining the light intensity information of each reflected light signal corresponding to different wavelengths includes: receiving the reflected light signals from the surface of the material to be tested through a photodiode; converting the reflected light signals into current signals in the photodiode; inputting the current signals into a transimpedance amplifier to convert them into voltage signals; filtering the voltage signals using a bandpass filter to obtain a filtered signal; inputting the filtered signal into an analog-to-digital converter to complete digital sampling; obtaining the sampling sequence of each filtered signal in the analog-to-digital converter; extracting the sampling value corresponding to the conduction time of the first infrared light-emitting diode of the infrared light source in the sampling sequence as the first channel light intensity sampling data; extracting the sampling value corresponding to the conduction time of the second infrared light-emitting diode of the infrared light source in the sampling sequence as the second channel light intensity sampling data; performing dark-state correction on the first channel light intensity sampling data and the second channel light intensity sampling data to obtain the first channel net light intensity value and the second channel net light intensity value as light intensity information.

[0009] Optionally, the step of performing dark-state correction on the first channel light intensity sampling data and the second channel light intensity sampling data to obtain the first channel net light intensity value and the second channel net light intensity value as light intensity information includes: acquiring the dark-state sampling values ​​of the first infrared light-emitting diode and the second infrared light-emitting diode before and after their conduction time, and taking the average of the dark-state sampling values ​​as the channel dark-state reference value of the first infrared light-emitting diode and the second infrared light-emitting diode; subtracting the channel dark-state reference value of the first infrared light-emitting diode from the first channel light intensity sampling data to obtain the dark-state corrected first channel net light intensity value; subtracting the channel dark-state reference value of the second infrared light-emitting diode from the second channel light intensity sampling data to obtain the dark-state corrected second channel net light intensity value; and using the first channel net light intensity value and the second channel net light intensity value as light intensity information.

[0010] Optionally, the step of constructing the average absorbance value of the water content characteristics of the material to be tested by the ratio relationship between light intensity information of different wavelengths includes: taking the net light intensity value of the first channel in the light intensity information as the reference channel intensity, and taking the net light intensity value of the second channel in the light intensity information as the measurement channel intensity; calculating the quotient of the measurement channel intensity and the reference channel intensity to obtain the original intensity ratio, and analyzing the preliminary absorbance value based on the original intensity ratio; continuously collecting N sets of the preliminary absorbance values ​​within a preset collection period, and calculating the arithmetic mean of the remaining values ​​after removing the maximum and minimum values ​​from the N sets of values ​​to obtain the average absorbance value.

[0011] Optionally, the step of performing environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value includes: the control IC reading the current ambient temperature in real time through the built-in temperature sensor, retrieving the temperature correction coefficient corresponding to the current ambient temperature from a pre-stored temperature compensation lookup table; and multiplying the average absorbance value by the temperature correction coefficient to obtain the compensated average absorbance value after temperature correction.

[0012] Optionally, the step of performing environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value includes: estimating the measurement distance between the current sensor and the material to be measured based on the intensity of the reference channel using a preset intensity-distance calibration relationship, and finding the distance correction coefficient corresponding to the measurement distance in a preset distance compensation coefficient table; multiplying the average absorbance value by the distance correction coefficient to obtain the compensated average absorbance value after distance correction.

[0013] Optionally, the step of inputting the compensated average absorbance value into a preset calibration model to output the moisture content of the material to be tested includes: the control IC substituting the compensated average absorbance value into the preset calibration model for item-by-item calculation and accumulation to obtain a calculated moisture content value; comparing the calculated moisture content value with a preset upper limit and lower limit of the effective range; if the lower limit of the effective range ≤ the calculated moisture content value ≤ the upper limit of the effective range, then directly outputting the calculated moisture content value as the moisture content of the material to be tested; if the calculated moisture content value is greater than the upper limit of the effective range or less than the lower limit of the effective range, then outputting an over-limit flag and triggering an abnormal alarm.

[0014] Optionally, the preset calibration model is stored in the non-volatile memory of the control IC in the form of a polynomial regression function. Specifically, the polynomial regression function is expressed as: in, The moisture content of the material to be tested. The compensated average absorbance value is... to For polynomial coefficients, The order of the polynomial and Greater than or equal to 2.

[0015] On the other hand, a material moisture content detection system based on dual-wavelength infrared light is also provided, comprising: a control module for controlling an infrared light source to emit infrared light of at least two different wavelengths and irradiating the surface of the material to be tested with the infrared light; a receiving module for receiving the reflected light signals of the surface of the material to be tested to each of the infrared lights and acquiring the light intensity information of each reflected light signal corresponding to different wavelengths; a construction module for constructing an average absorbance value of the moisture content characteristics of the material to be tested through the ratio relationship between the light intensity information of different wavelengths; a compensation module for performing environmental disturbance compensation on the average absorbance value to obtain a compensated average absorbance value, wherein the environmental disturbance compensation includes correcting the signal deviation caused by temperature changes and / or measurement distance changes; and an output module for inputting the compensated average absorbance value into a preset calibration model to output the moisture content of the material to be tested.

[0016] This application provides a material moisture content detection method based on dual-wavelength infrared light, which has the following technical effects: By controlling an infrared light source to emit at least two different wavelengths of infrared light, and irradiating the surface of the material to be tested with the infrared light, the different wavelengths of infrared light interact with the material through absorption and reflection; the reflected light signals from the surface of the material to be tested are received, and the light intensity information corresponding to each wavelength of the reflected light signal is obtained; after obtaining the light intensity information of different wavelengths, the average absorbance value of the moisture content characteristics of the material to be tested is constructed through the ratio relationship between the light intensity information of different wavelengths, so as to characterize the relative absorption degree of the material to be tested by a specific wavelength of infrared light; after obtaining the average absorbance value, environmental disturbance compensation is performed on the average absorbance value, including correction of signal deviations caused by temperature changes and / or measurement distance changes, to obtain a compensated average absorbance value; the compensated average absorbance value is input into a preset calibration model to output the moisture content of the material to be tested, thereby improving the stability and reliability of moisture content detection in practical application environments and overcoming the measurement error problem caused by environmental changes. Attached Figure Description

[0017] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a flowchart illustrating a material moisture content detection method based on dual-wavelength infrared light according to an embodiment of the present invention; Figure 2 is a schematic diagram illustrating the time-sequential alternating conduction according to an embodiment of the present invention; Figure 3 is a schematic diagram illustrating the signal processing flow of the reflected light signal according to an embodiment of the present invention; Figure 4 is a schematic diagram illustrating the calculation of absorbance after compensation according to an embodiment of the present invention; Figure 5 is a schematic diagram illustrating the moisture content output of the polynomial calibration model according to an embodiment of the present invention; Figure 6 is a schematic block diagram illustrating the structure of a material moisture content detection system based on dual-wavelength infrared light according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or sub-modules is not necessarily limited to those steps or sub-modules explicitly listed, but may include other steps or sub-modules not explicitly listed or inherent to such processes, methods, products, or devices.

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] As shown in Figure 1, this application provides a method for detecting the moisture content of materials based on dual-wavelength infrared light. This method can be applied to online or offline moisture content detection scenarios for grain pellets, sawdust pellets, powdered feed, or flake materials. It mainly includes the following steps: Step S1, controlling the infrared light source to emit at least two different wavelengths of infrared light, and irradiating the surface of the material to be tested with the infrared light.

[0023] The infrared light source comprises at least two infrared light-emitting diodes (LEDs) with different emission center wavelengths, each of which can be independently driven by a control IC. The control IC integrates a timing control module and a pulse width modulation module. The timing control module generates a fixed-period timing control signal, while the pulse width modulation module generates a drive pulse signal with a set frequency and duty cycle. The two different wavelengths of infrared light correspond to the moisture absorption sensitive band and the moisture absorption weak sensitive band, respectively, causing the test material to exhibit different reflection intensity responses at the two wavelengths. The infrared light is emitted onto the surface of the test material through an optical window, illuminating a fixed-area measurement region. This measurement region is defined by the optical structure as a circular area with a diameter of 5mm to 20mm to ensure consistent illumination range for each test.

[0024] For example, in a grain moisture content detection scenario, an infrared LED with an emission center wavelength of 1050nm can be selected as the reference wavelength light source, and an infrared LED with an emission center wavelength of 1450nm can be selected as the moisture absorption sensitive wavelength light source. The control IC sets the driving frequency to 1kHz, the duty cycle to 40%, and the width of a single emission pulse to 400μs, so that the two wavelengths of infrared light are in the conducting state within a 1ms period, to ensure that a stable reflected signal is obtained per unit time.

[0025] In another example, step S1 may preferably be implemented as follows: the control IC outputs drive pulse signals with preset frequencies and duty cycles to the first infrared LED and the second infrared LED of the infrared light source, respectively, wherein the emission wavelength of the first infrared LED is 1050nm and the emission wavelength of the second infrared LED is 1450nm.

[0026] The preset frequency is set by the timer register inside the control IC. The timer clock frequency is 8MHz, and a drive frequency in the range of 1kHz to 5kHz is obtained through frequency division. The duty cycle is set between 20% and 60% by the pulse width modulation module to control the average emission power of the infrared LEDs. The drive pulse signal output by the control IC is input to the first and second infrared LEDs after passing through a current-limiting resistor or a constant current drive circuit, so that both operate within their rated current range of 50mA to 150mA.

[0027] For example, the driving current of the first infrared LED is set to 100mA and the driving current of the second infrared LED is set to 120mA. Through experimental calibration, it is determined that the reflection intensity of the two wavelengths on the standard white board is on the same order of magnitude, thereby avoiding oversaturation or undersaturation of the single-channel signal.

[0028] As shown in Figure 2, the first infrared LED and the second infrared LED are alternately turned on according to a preset timing sequence by using a driving pulse signal, so that either the first infrared LED or the second infrared LED is in the emitting state at any time, thus obtaining a 1050nm light pulse sequence and a 1450nm light pulse sequence that are spaced apart in the time dimension.

[0029] The control IC internally sets a complementary phase relationship between the two output ports, ensuring that the conduction time periods of the first and second infrared LEDs do not overlap. The timing control logic uses a complete cycle T as a reference, dividing T into two equal-length or unequal-length time periods, corresponding to a 1050nm light pulse sequence and a 1450nm light pulse sequence, respectively. This alternating conduction method avoids the simultaneous illumination of the test material by two different wavelengths of infrared light within the same measurement cycle, reducing signal crosstalk.

[0030] For example, when the driving frequency is 2kHz and the period T is 500μs, the first 250μs is set as the conduction interval of the 1050nm optical pulse sequence, and the last 250μs is set as the conduction interval of the 1450nm optical pulse sequence. A dead time of 5μs is set between the two intervals to avoid transient interference during switching.

[0031] The emitted light paths of the first infrared LED and the second infrared LED are converged by the same optical collimating component and then irradiated onto the same measurement area on the surface of the material to be measured at a preset fixed emission angle and light pulse sequence.

[0032] The optical collimation assembly includes a lens or reflector cup structure. The lens focal length is 10mm to 30mm, and the emission angle is limited to 10° to 30°, ensuring that the two wavelengths of infrared light have a consistent spatial divergence angle. The first and second infrared LEDs are mounted on the same optical support, which ensures that the optical axis distance between them is less than 3mm, and the collimation assembly ensures that the two infrared beams coincide in space. The fixed emission angle is locked by a mechanical structure to ensure that the optical path geometry between the sensor and the material being measured remains consistent.

[0033] For example, a convex lens with a diameter of 15 mm is used as an optical collimation component. The first infrared light-emitting diode and the second infrared light-emitting diode are placed near the focal plane of the lens. By adjusting the installation position, the two infrared beams form an overlapping spot with a diameter of 8 mm at a distance of 50 mm from the lens and are aligned with the same measurement area on the surface of the material to be measured, thereby ensuring that the two infrared beams of different wavelengths are completely consistent in spatial position.

[0034] Step S2: Receive the reflected light signals of each infrared light from the surface of the material to be tested, and obtain the light intensity information of each reflected light signal corresponding to different wavelengths.

[0035] A photoelectric detection component is installed on one side of the outgoing light path of the infrared light source. The receiving optical axis of the photoelectric detection component forms a fixed angle with the outgoing optical axis of the infrared light source, which is 15° to 45°, so as to receive the diffuse reflection light signals of each infrared light from the surface of the material to be tested. The effective receiving area of ​​the photoelectric detection component covers the reflection range of the measurement area, and the light-shielding structure suppresses the direct incidence of external ambient light, thereby ensuring that the received reflected light signals mainly come from the reflection response of the material to be tested to infrared light.

[0036] For example, in the grain particle detection scenario, the photoelectric detection component is installed at a distance of 50mm from the surface of the material to be tested, with the receiving angle set to 30°, and a narrow-band optical filter is set at the front end of the photoelectric detection component so that the transmitted spectral range covers the 1050nm and 1450nm bands respectively, thereby improving the signal-to-noise ratio.

[0037] As shown in Figure 3, in another example, step S2 can also be preferably performed as follows: receiving the reflected light signal from the surface of the material to be tested through a photodiode, and converting the reflected light signal into a current signal in the photodiode.

[0038] The photodiode is selected from silicon photodiodes or indium gallium arsenide photodiodes that have response characteristics to the near-infrared band. The photodiode operates in reverse bias to improve response speed and linearity. When infrared light of different wavelengths irradiates the material under test and is reflected to the photodiode, a photocurrent proportional to the intensity of the reflected light is generated inside the photodiode, thereby realizing the conversion of optical signal to current signal.

[0039] For example, by setting the reverse bias voltage of the photodiode to 5V, the response time is less than 1μs, and it maintains a linear response range in both the 1050nm and 1450nm wavelength bands, so that the output current signal and the reflected light intensity are linearly related.

[0040] The current signal is input to the transimpedance amplifier and converted into a voltage signal. The voltage signal is then filtered using a bandpass filter to suppress noise interference in non-target frequency bands, resulting in a filtered signal. The filtered signal is then input to the analog-to-digital converter to complete digital sampling.

[0041] The feedback resistor of the transimpedance amplifier is matched and selected according to the output current range of the photodiode to ensure that the output voltage signal is within the input range of the analog-to-digital converter; the center frequency of the bandpass filter is consistent with the frequency of the drive pulse signal, and the bandwidth is set within ±10% of the drive frequency to suppress the DC component of ambient light and high-frequency interference; the sampling frequency of the analog-to-digital converter is at least 10 times the drive frequency to ensure that the filtered signal is fully sampled.

[0042] For example, when the driving frequency is 2kHz, the center frequency of the bandpass filter is set to 2kHz, the bandwidth is set to 400Hz, the sampling frequency of the analog-to-digital converter is set to 20kHz, and the resolution is 12 bits, so that no less than 10 sampling points are obtained in each driving cycle.

[0043] The control IC obtains the sampling sequence of each filtered signal in the analog-to-digital converter based on the timing control logic synchronized with the drive pulse signal, and extracts the sampling value corresponding to the conduction time of the first infrared light-emitting diode of the infrared light source in the sampling sequence as the light intensity sampling data of the first channel.

[0044] The control IC internally sets a timing reference signal that is of the same origin as the drive pulse signal. The data output by the analog-to-digital converter is marked by a timestamp or counter. The corresponding sampling point is extracted within the conduction time window of the first infrared light-emitting diode, and the sampled values ​​within the time window are averaged to reduce the impact of instantaneous fluctuations.

[0045] For example, if the conduction time of the first infrared LED is 250 μs, five consecutive sample values ​​are extracted from this time period, and their arithmetic mean is calculated as the first channel light intensity sampling data in one detection cycle.

[0046] The sampled values ​​corresponding to the turn-on time of the second infrared light-emitting diode of the infrared light source in the sampling sequence are extracted as the light intensity sampling data of the second channel.

[0047] The control IC extracts the corresponding sampled values ​​within the conduction time window of the second infrared LED according to the same timing control logic, and performs average or median processing on the extracted sampled values ​​to obtain stable second channel light intensity sampling data.

[0048] For example, when the conduction time of the second infrared light-emitting diode is 250μs, five consecutive sample values ​​are extracted and the average value is calculated to obtain the second channel light intensity sampling data corresponding to the 1450nm band.

[0049] Dark-state correction is performed on the light intensity sampling data of the first channel and the light intensity sampling data of the second channel to obtain the net light intensity value of the first channel and the net light intensity value of the second channel, which are used as light intensity information.

[0050] Dark-state correction is used to eliminate dark current in photodiodes, zero-point drift in transimpedance amplifiers, and baseline shift caused by ambient background radiation. It is achieved by measuring and subtracting the sampled values ​​when not exposed to infrared light, thus extracting the effective reflected light signal.

[0051] For example, dark state sampling values ​​are acquired during the dead time of each drive cycle and used for subsequent net light intensity calculations.

[0052] Furthermore, the step of performing dark-state correction on the light intensity sampling data of the first channel and the light intensity sampling data of the second channel to obtain the net light intensity value of the first channel and the net light intensity value of the second channel as light intensity information can also be preferably performed as follows: obtaining the dark-state sampling values ​​of the first infrared light-emitting diode and the second infrared light-emitting diode before and after the conduction time of the infrared light source, and taking the average value of the dark-state sampling values ​​as the channel dark-state reference value of the first infrared light-emitting diode and the second infrared light-emitting diode.

[0053] The control IC collects multiple sample values ​​during the time interval when both the first infrared LED and the second infrared LED are in the off state, and divides them into dark state sample sets corresponding to the first infrared LED and the second infrared LED according to the principle of time proximity. By calculating the mean of each set, the channel dark state reference value is obtained.

[0054] For example, a 10μs dark state sampling window is set for each period, and three sampling points are collected within this window. The average value is calculated and used as the dark state reference value for the corresponding channel.

[0055] By subtracting the channel dark-state reference value of the first infrared light-emitting diode from the light intensity sampling data of the first channel, the net light intensity value of the first channel after dark-state correction is obtained.

[0056] By eliminating the influence of dark current and background signal through difference calculation, the net light intensity value of the first channel reflects only the effective reflection intensity of the material under test to 1050nm infrared light.

[0057] If the light intensity sampling data of the first channel is 1.25V, and the corresponding dark state reference value of the channel is 0.15V, then the net light intensity value of the first channel is 1.10V.

[0058] By subtracting the dark-state reference value of the second infrared LED from the light intensity sampling data of the second channel, the net light intensity value of the second channel after dark-state correction is obtained.

[0059] Similarly, the effective signal intensity formed solely by the reflection of 1450nm infrared light by the test material is obtained through difference calculation, thereby improving the comparability between the two channels.

[0060] If the light intensity sampling data of the second channel is 0.95V, and the corresponding dark state reference value of the channel is 0.14V, then the net light intensity value of the second channel is 0.81V.

[0061] The net light intensity values ​​of the first and second channels are used as light intensity information.

[0062] The net light intensity values ​​of the first and second channels correspond to the effective reflection intensities of two different wavelengths of infrared light in the same measurement area, respectively. These values ​​serve as input data for constructing the average absorbance value by comparing the ratios between light intensity information of different wavelengths.

[0063] For example, if the net light intensity value of the first channel is 1.10V and the net light intensity value of the second channel is 0.81V in a detection cycle, these two values ​​are stored in the internal register of the control IC and transmitted to the subsequent processing module for the calculation of the average absorbance value.

[0064] Step S3: Construct the average absorbance value of the water content characteristics of the material to be tested by the ratio relationship between light intensity information of different wavelengths.

[0065] The control IC performs a ratio calculation on the net light intensity values ​​of the first channel and the second channel. By constructing a ratio relationship between light intensity information of different wavelengths, the influence of common-mode factors such as fluctuations in the overall emission intensity of the infrared light source and changes in the gain of the photoelectric detection component is eliminated. This ensures that the obtained characteristic quantity mainly reflects the absorption difference of the infrared light in the moisture-sensitive band of the material being tested, thereby improving the correlation with moisture content.

[0066] For example, if the net light intensity of the first channel is 1.10V and the net light intensity of the second channel is 0.81V within a detection cycle, the calculation result is no longer directly dependent on the absolute light intensity value, but on the relative change relationship between the two wavelengths by performing ratio processing on the two channels.

[0067] As shown in Figure 4, in another example, step S3 can also preferably be implemented as follows: using the net light intensity value of the first channel in the light intensity information as the reference channel intensity, and using the net light intensity value of the second channel in the light intensity information as the measurement channel intensity; using the net light intensity value of the 1050nm channel as the reference channel intensity. The net light intensity of the 1450nm channel was used as the measurement channel intensity. The original intensity ratio is obtained by calculating the quotient of the measured channel intensity and the reference channel intensity. .

[0068] Reference channel strength Corresponding to the weakly sensitive wavelength band of moisture absorption, it is used to characterize the reference reflectance level of the material under test; measuring channel intensity Corresponding to the moisture absorption sensitive band, it is used to characterize the reflection change of the analyte near the moisture absorption peak; by calculating the original intensity ratio This allows the ratio between the two channels to serve as the basis for subsequent absorbance calculations.

[0069] For example, when =1.10V, When the voltage is 0.81V, the original strength ratio R = 0.81 / 1.10 ≈ 0.736.

[0070] The quotient of the intensity of the measured channel and the intensity of the reference channel is calculated to obtain the original intensity ratio. The preliminary absorbance value is analyzed based on the original intensity ratio. The negative logarithm of the original intensity ratio R to base 10 is taken to obtain the preliminary absorbance value A = -lg(R), where the preliminary absorbance value characterizes the relative absorption of the material to be tested by infrared light with a wavelength of 1450nm.

[0071] By performing a logarithmic transformation on the original intensity ratio R, the ratio relationship is converted into absorbance form, making it more closely related to the substance concentration in an approximately linear manner, thus facilitating the establishment of subsequent calibration models. A negative logarithmic operation with base 10 is used to make the initial absorbance value A change monotonically with the increase of moisture content.

[0072] When R≈0.736, then A=-lg(0.736)≈0.133, and the obtained preliminary absorbance value A is used to characterize the moisture absorption characteristics of the material to be tested within this detection period.

[0073] Within a preset acquisition period, N sets of preliminary absorbance values ​​are continuously acquired. The arithmetic mean of the remaining values ​​after removing the maximum and minimum values ​​from the N sets is calculated to obtain the average absorbance value. Here, N is a positive integer greater than or equal to 5.

[0074] By repeatedly sampling within a preset acquisition period, N sets of preliminary absorbance values ​​are obtained to reduce random errors caused by instantaneous fluctuations, uneven particle distribution, or mechanical vibration. By removing the maximum and minimum values, the influence of abnormal sampling points on the results is eliminated. Then, the remaining values ​​are arithmetically averaged to make the average absorbance value more stable and representative.

[0075] For example, if N=7 is set within a single acquisition cycle, seven preliminary absorbance values ​​are obtained: 0.130, 0.133, 0.135, 0.132, 0.180, 0.129, and 0.131. After removing the maximum value of 0.180 and the minimum value of 0.129, the arithmetic mean of the remaining five values ​​is calculated, resulting in an average absorbance value of approximately 0.132. This average absorbance value is used as a characterization parameter for the moisture content of the material under test and is subsequently used for environmental disturbance compensation and calibration model calculations.

[0076] Step S4: Perform environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value. The environmental disturbance compensation includes correcting the signal deviation caused by temperature changes and / or measurement distance changes.

[0077] The control IC is based on the average absorbance value and is modified according to environmental parameters to reduce the impact of changes in external conditions on the detection results. Environmental disturbances mainly come from temperature changes causing the infrared light source emission power to drift and the photoelectric detection component sensitivity to change, as well as the difference in diffuse reflection light intensity attenuation caused by changes in measurement distance. By establishing a corresponding correction relationship between environmental parameters and the average absorbance value, the compensated average absorbance value is made more stable.

[0078] For example, if the ambient temperature rises from 25°C to 40°C without correction, the average absorbance value will show a systematic shift; by introducing temperature compensation, this shift can be controlled within a preset error range.

[0079] In another example, step S4 can also preferably be implemented as follows: the control IC reads the current ambient temperature in real time through the built-in temperature sensor and retrieves the temperature correction coefficient corresponding to the current ambient temperature from a pre-stored temperature compensation lookup table; the temperature compensation lookup table is established from the data obtained from calibration experiments on standard samples with known water content under different temperature conditions.

[0080] Temperature sensors are integrated into the control IC or installed near the photoelectric detection components to obtain temperature data consistent with the working state of the infrared light source and the photoelectric detection components. The temperature compensation lookup table uses temperature as an index to store the temperature correction coefficients corresponding to different temperature points, covering a temperature range from 0℃ to 60℃, with intervals of 5℃ or 10℃. When the actual temperature is between two temperature points, the corresponding temperature correction coefficient can be obtained by linear interpolation.

[0081] When the current ambient temperature is 38℃, the temperature correction factor for 35℃ is found to be 0.985 and the temperature correction factor for 40℃ is 0.972 in the temperature compensation lookup table. Therefore, the temperature correction factor for 38℃ is approximately 0.977 calculated by linear interpolation.

[0082] Multiply the average absorbance value by the temperature correction factor to obtain the temperature-corrected average absorbance value.

[0083] The average absorbance value is proportionally adjusted by multiplication correction to restore it to the equivalent value under the reference temperature condition, thereby reducing the systematic error caused by temperature drift.

[0084] When the average absorbance is 0.132 and the temperature correction factor is 0.977, the compensated average absorbance after temperature correction is approximately 0.132 × 0.977 ≈ 0.129.

[0085] In another example, step S4 may also be preferably performed as follows: the measurement distance between the current sensor and the material to be measured is estimated based on the reference channel intensity using a preset intensity-distance calibration relationship, and the distance correction coefficient corresponding to the measurement distance is found in a preset distance compensation coefficient table, wherein the distance compensation coefficient table is established based on the attenuation law of diffuse reflection light intensity of the sensor at different installation distances.

[0086] The reference channel intensity is used to estimate the measurement distance because the reference channel intensity mainly reflects the geometric attenuation characteristics and is not sensitive to moisture absorption. During the equipment factory calibration stage, the correspondence between the reference channel intensity and the actual distance is recorded under different fixed measurement distance conditions to establish the intensity-distance calibration relationship. At the same time, a distance compensation coefficient table is established based on the variation law of the average absorbance value under different distances.

[0087] For example, during the calibration phase, when the measurement distances are 40mm, 50mm, and 60mm, the corresponding reference channel strengths are recorded as 1.30V, 1.10V, and 0.95V, respectively, and an interpolation model is established for distance estimation during runtime. If the current reference channel strength is 1.00V, the estimated measurement distance is approximately 55mm, and the distance correction coefficient corresponding to 55mm is found to be 1.015 in the distance compensation coefficient table.

[0088] Multiply the average absorbance value by the distance correction factor to obtain the compensated average absorbance value after distance correction.

[0089] The average absorbance value is geometrically compensated by a proportional correction method to correspond to the equivalent value under the reference installation distance, thereby reducing the impact of installation deviation or material surface undulation on the test results.

[0090] When the average absorbance value is 0.132 and the distance correction factor is 1.015, the compensated average absorbance value after distance correction is 0.132×1.015≈0.134. If temperature correction and distance correction are performed simultaneously, they are corrected in a preset order to obtain the final compensated average absorbance value used for calibrating the model input.

[0091] Step S5: Input the compensated average absorbance value into the preset calibration model to output the moisture content of the material to be tested.

[0092] The control IC reads the compensated average absorbance value and uses it as an input variable to calculate the optical characteristic value into the corresponding moisture content value of the material to be tested. The preset calibration model establishes a functional mapping relationship between the compensated average absorbance value and the actual moisture content of the material to be tested, thereby realizing the quantitative conversion from optical detection results to moisture content results.

[0093] When the compensated average absorbance value is 0.134, the control IC calls the calibration model parameters stored in the internal memory, calculates the corresponding water content value as 14.8%, and uses it as a test result.

[0094] As shown in Figure 5, in another example, step S5 can also be preferably performed as follows: the control IC substitutes the compensated average absorbance value into the preset calibration model to perform item-by-item calculations and sums them up to obtain the water content calculation value.

[0095] The control IC performs multiplication and addition operations sequentially according to the coefficients of each term of the polynomial. It multiplies the different powers of the compensated average absorbance value with the corresponding polynomial coefficients and accumulates the results to obtain the water content calculation value. To improve calculation efficiency, a recursive method from high order to low order can be used to complete the power calculation and accumulation operation.

[0096] When the polynomial order n is 3, the calibration model is: The control IC calculates sequentially. and and multiply by respectively and , and then with and The values ​​are accumulated to obtain the calculated water content.

[0097] The calculated moisture content is compared with the preset upper and lower limits of the effective range. If the lower limit of the effective range ≤ the calculated moisture content ≤ the upper limit of the effective range, the calculated moisture content is directly output as the moisture content of the material to be tested.

[0098] The upper and lower limits of the effective range are preset according to the specific type of material to be measured. For example, for grain particles, the lower limit of the effective range can be set to 5% and the upper limit of the effective range to 35%. The control IC determines whether the calculated moisture content value is within the range by comparison calculation. If it is within the range, the calculated moisture content value is output to the display module or communication interface.

[0099] When the calculated moisture content is 14.8% and the effective range is 5% to 35%, 14.8% is directly output as the moisture content of the material to be tested and sent to the host computer system via serial port or wireless module.

[0100] If the calculated moisture content is greater than the upper limit of the effective range or less than the lower limit of the effective range, an over-limit flag will be output and an abnormal alarm will be triggered, thus completing the final output of the moisture content to be measured.

[0101] When the control IC detects that the calculated water content exceeds the effective range, it writes the over-limit flag into the status register and drives the alarm module to issue an audible and visual alarm signal or send abnormal status data to the host computer to indicate that the current detection result is not within the applicable range of the calibration model.

[0102] When the calculated moisture content is 38% and the upper limit of the effective range is 35%, the control IC outputs an over-limit flag at a high level, simultaneously controls the buzzer to sound for 2 seconds, and adds an exception code to the communication data frame to prompt the operator to retest or calibrate.

[0103] The preset calibration model is stored in the non-volatile memory of the control IC in the form of a polynomial regression function. Specifically, the polynomial regression function is expressed as: in, The moisture content of the material to be tested. The average absorbance value after compensation. to For polynomial coefficients, The order of the polynomial and The polynomial coefficients are greater than or equal to 2 and are determined by fitting data obtained from calibration of the test materials with different moisture content gradients using the drying and weighing method under controlled laboratory conditions.

[0104] The polynomial coefficients are written into the non-volatile memory of the control IC through a calibration process before the equipment leaves the factory and stored in correspondence with the material type. When different types of test materials are detected, the polynomial coefficient group of the corresponding material can be called for calculation. By adopting a polynomial form with n greater than or equal to 2, the calibration model can fit the nonlinear relationship between the compensated average absorbance value and the moisture content.

[0105] For example, when calibrating a certain grain variety, 10 groups of samples with different moisture content gradients are selected, the corresponding compensated average absorbance values ​​are measured, and the least squares method is used for fitting to obtain the polynomial coefficients when n=3. and After writing the set of polynomial coefficients into the non-volatile memory of the control IC, the moisture content of the material to be tested can be calculated based on the real-time compensated average absorbance value during actual detection, thus completing the entire process of material moisture content detection based on dual-wavelength infrared light.

[0106] In this embodiment, by controlling the infrared light source to emit infrared light of two different wavelengths, 1050nm and 1450nm, and using a control IC to achieve alternating conduction of the two different wavelengths of infrared light in the time dimension, the two different wavelengths of infrared light are illuminated by the same optical collimation component onto the same measurement area on the surface of the material to be tested, thereby ensuring the consistency of the detection conditions. The reflected light signals of the material to be tested to each infrared light are received by a photodiode, and processed by a transimpedance amplifier, a bandpass filter, and an analog-to-digital converter. Combined with timing control logic synchronized with the drive pulse signal, the light intensity sampling data of the first channel and the second channel are extracted respectively, and dark state correction is performed to obtain the light intensity sampling data of the second channel. The net light intensity values ​​of the first and second channels are used as light intensity information. The initial absorbance value is obtained by calculating the original intensity ratio between the intensity of the measured channel and the intensity of the reference channel and taking the negative logarithm. Multiple acquisitions are performed within a preset acquisition period, and extreme values ​​are removed to obtain the average absorbance value. The average absorbance value is further corrected for signal deviations caused by temperature changes and measurement distance changes to obtain a compensated average absorbance value. This value is then substituted into a preset calibration model stored in the form of a polynomial regression function to output the moisture content of the material to be tested. This improves the stability and accuracy of the moisture content detection results while ensuring a relatively simple structure, and overcomes the measurement error problem caused by environmental changes.

[0107] As shown in Figure 6, this application also provides a material moisture content detection system 10 based on dual-wavelength infrared light. The system mainly includes a control module 11, a receiving module 12, a construction module 13, a compensation module 14, and an output module 15. The control module 11 is used to control the infrared light source to emit infrared light of at least two different wavelengths and to make the infrared light irradiate the surface of the material to be tested.

[0108] The receiving module 12 is used to receive the reflected light signals of each infrared light from the surface of the material to be tested, and to obtain the light intensity information of each reflected light signal corresponding to different wavelengths.

[0109] Module 13 is used to construct the average absorbance value of the water content characteristics of the material to be tested by using the ratio relationship between light intensity information of different wavelengths.

[0110] The compensation module 14 is used to perform environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value. The environmental disturbance compensation includes correcting the signal deviation caused by temperature changes and / or measurement distance changes.

[0111] The output module 15 is used to input the compensated average absorbance value into the preset calibration model to output the moisture content of the material to be tested.

[0112] In this embodiment, by functionally dividing and modularly integrating the control module 11, receiving module 12, construction module 13, compensation module 14, and output module 15, a clear data processing link is formed, encompassing infrared light emission control, reflected light signal acquisition, light intensity information processing, average absorbance value construction, environmental disturbance compensation, and moisture content output. The control module 11 performs timing control and stable driving of at least two different wavelengths of infrared light, ensuring that the infrared light illuminates the surface of the material to be measured within the same measurement area. The receiving module 12 converts and extracts the reflected light signals from each infrared light source on the surface of the material to be measured, obtaining... The system obtains light intensity information corresponding to different wavelengths; the average absorbance value is formed by the construction module 13 based on the ratio relationship between the light intensity information of different wavelengths to reduce the impact of light source fluctuations and device drift; the average absorbance value is corrected by the compensation module 14 for signal deviation caused by temperature changes and / or measurement distance changes to improve the stability of the characteristic quantity; and the moisture content is calculated and the result is output by calling the preset calibration model through the output module 15, thereby realizing the modular implementation and collaborative operation of the detection process. Under the premise of ensuring a relatively simple system structure, the accuracy, stability and engineering application adaptability of material moisture content detection are improved.

[0113] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are also possible or may be advantageous.

[0114] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device, equipment, and storage medium embodiments are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0115] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware, or by a program instructing the relevant hardware to implement them. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0116] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for detecting the moisture content of materials based on dual-wavelength infrared light, characterized in that, include: An infrared light source is controlled to emit infrared light of at least two different wavelengths, and the infrared light is directed onto the surface of the material to be tested. The reflected light signals from the surface of the material to be tested for each of the infrared lights are received, and the light intensity information corresponding to each reflected light signal at different wavelengths is obtained. An average absorbance value of the moisture content of the material to be tested is constructed based on the ratio relationship between the light intensity information of different wavelengths. Environmental disturbance compensation is applied to the average absorbance value to obtain a compensated average absorbance value, wherein the environmental disturbance compensation includes correcting signal deviations caused by temperature changes and / or changes in measurement distance. The compensated average absorbance value is input into a preset calibration model to output the moisture content of the material to be tested.

2. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 1, characterized in that, The step of controlling the infrared light source to emit infrared light of at least two different wavelengths and irradiating the surface of the material to be tested includes: a control IC outputting driving pulse signals with preset frequencies and duty cycles to the first and second infrared light-emitting diodes of the infrared light source; using the driving pulse signals to alternately turn on the first and second infrared light-emitting diodes according to a preset timing sequence, so that either the first or second infrared light-emitting diode is in an emitting state at any time, resulting in a sequence of light pulses that are spaced apart; and converging the emitted light paths of the first and second infrared light-emitting diodes through the same optical collimating component, and irradiating the same measurement area on the surface of the material to be tested with a preset fixed emission angle and the light pulse sequence.

3. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 1, characterized in that, The step of receiving the reflected light signals of the infrared light from the surface of the material under test and acquiring the light intensity information of each reflected light signal corresponding to different wavelengths includes: receiving the reflected light signals from the surface of the material under test through a photodiode; converting the reflected light signals into current signals in the photodiode; inputting the current signals into a transimpedance amplifier to convert them into voltage signals; filtering the voltage signals using a bandpass filter to obtain a filtered signal; inputting the filtered signal into an analog-to-digital converter to complete digital sampling; acquiring the sampling sequence of each filtered signal in the analog-to-digital converter; extracting the sampling value corresponding to the conduction time of the first infrared light-emitting diode of the infrared light source in the sampling sequence as the first channel light intensity sampling data; extracting the sampling value corresponding to the conduction time of the second infrared light-emitting diode of the infrared light source in the sampling sequence as the second channel light intensity sampling data; performing dark-state correction on the first channel light intensity sampling data and the second channel light intensity sampling data to obtain the first channel net light intensity value and the second channel net light intensity value as light intensity information.

4. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 3, characterized in that, The step of performing dark-state correction on the first channel light intensity sampling data and the second channel light intensity sampling data to obtain the first channel net light intensity value and the second channel net light intensity value as light intensity information includes: acquiring the dark-state sampling values ​​of the first infrared light-emitting diode and the second infrared light-emitting diode of the infrared light source before and after their conduction time, and taking the average of the dark-state sampling values ​​as the channel dark-state reference value of the first infrared light-emitting diode and the second infrared light-emitting diode; subtracting the channel dark-state reference value of the first infrared light-emitting diode from the first channel light intensity sampling data to obtain the dark-state corrected first channel net light intensity value; subtracting the channel dark-state reference value of the second infrared light-emitting diode from the second channel light intensity sampling data to obtain the dark-state corrected second channel net light intensity value; and using the first channel net light intensity value and the second channel net light intensity value as light intensity information.

5. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 3, characterized in that, The step of constructing the average absorbance value of the water content characteristics of the material to be tested by the ratio relationship between light intensity information of different wavelengths includes: taking the net light intensity value of the first channel in the light intensity information as the reference channel intensity, and taking the net light intensity value of the second channel in the light intensity information as the measurement channel intensity; calculating the quotient of the measurement channel intensity and the reference channel intensity to obtain the original intensity ratio, and analyzing the preliminary absorbance value based on the original intensity ratio; continuously collecting N sets of the preliminary absorbance values ​​within a preset collection period, and calculating the arithmetic mean of the remaining values ​​after removing the maximum and minimum values ​​from the N sets of values ​​to obtain the average absorbance value.

6. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 1, characterized in that, The step of performing environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value includes: the control IC reads the current ambient temperature in real time through the built-in temperature sensor, retrieves the temperature correction coefficient corresponding to the current ambient temperature from the pre-stored temperature compensation lookup table, and multiplies the average absorbance value by the temperature correction coefficient to obtain the temperature-corrected compensated average absorbance value.

7. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 5, characterized in that, The step of performing environmental disturbance compensation on the average absorbance value to obtain the compensated average absorbance value includes: estimating the measurement distance between the current sensor and the material to be measured based on the intensity of the reference channel using a preset intensity-distance calibration relationship, and finding the distance correction coefficient corresponding to the measurement distance in a preset distance compensation coefficient table; multiplying the average absorbance value by the distance correction coefficient to obtain the compensated average absorbance value after distance correction.

8. The method for detecting the moisture content of materials based on dual-wavelength infrared light according to claim 1, characterized in that, The step of inputting the compensated average absorbance value into a preset calibration model to output the moisture content of the material to be tested includes: the control IC substituting the compensated average absorbance value into the preset calibration model for item-by-item calculation and accumulation to obtain a calculated moisture content value; comparing the calculated moisture content value with a preset upper limit and lower limit of the effective range; if the lower limit of the effective range ≤ the calculated moisture content value ≤ the upper limit of the effective range, then directly outputting the calculated moisture content value as the moisture content of the material to be tested; if the calculated moisture content value is greater than the upper limit of the effective range or less than the lower limit of the effective range, then outputting an over-limit flag and triggering an abnormal alarm.

9. The method for detecting material moisture content based on dual-wavelength infrared light according to claim 1, characterized in that, The preset calibration model is stored in the non-volatile memory of the control IC in the form of a polynomial regression function. Specifically, the polynomial regression function is expressed as: in, The moisture content of the material to be tested. The compensated average absorbance value is... to For polynomial coefficients, The order of the polynomial and Greater than or equal to 2.

10. A material moisture content detection system based on dual-wavelength infrared light, characterized in that, include: The control module is used to control the infrared light source to emit infrared light of at least two different wavelengths and to make the infrared light irradiate the surface of the material to be tested; the receiving module is used to receive the reflected light signals of each infrared light from the surface of the material to be tested and to obtain the light intensity information of each reflected light signal corresponding to different wavelengths; the construction module is used to construct the average absorbance value of the water content characteristics of the material to be tested by the ratio relationship between the light intensity information of different wavelengths. The compensation module is used to compensate for environmental disturbances in the average absorbance value to obtain a compensated average absorbance value. The environmental disturbance compensation includes correcting signal deviations caused by temperature changes and / or measurement distance changes. The output module is used to input the compensated average absorbance value into a preset calibration model to output the moisture content of the material to be tested.

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