Grain moisture detection system and method based on circularly polarized microwaves
By using circularly polarized microwave technology and data processing algorithms, the measurement error caused by the anisotropy of grain particles has been solved, enabling high-precision and rapid grain moisture detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-16
- Publication Date
- 2026-04-07
AI Technical Summary
Existing microwave detection technologies suffer from poor repeatability and low accuracy when detecting grain particles due to anisotropy, and cannot effectively overcome the measurement errors caused by the random stacking of grain particles.
Using circularly polarized microwave technology, and utilizing a circularly polarized microwave transceiver module, a signal acquisition and processing module, a detection chamber, and a calculation and control module, the moisture content of the grain is calculated by penetrating the grain sample through the circularly polarized microwave signal and combining a quadratic approximation mean filtering algorithm and a temperature-compensated polynomial regression model.
It improves the repeatability and accuracy of measurements, reflects the overall moisture content of grain samples, suppresses surface reflection interference, and enables rapid online non-destructive testing.
Smart Images
Figure CN121805288A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of non-destructive testing technology for grain quality, specifically to a system and method for rapid, online, and high-precision detection of the moisture content of grain particles using microwave technology, particularly circularly polarized microwaves. Background Technology
[0002] The moisture content of grains is a core indicator determining their storage safety and processing quality. Existing online moisture detection technologies mainly include near-infrared spectroscopy and capacitance methods. However, near-infrared light has weak penetrating power and can only detect moisture on the surface of materials; capacitance methods are easily affected by temperature, density, and variety differences, resulting in insufficient accuracy and stability.
[0003] Microwave technology has attracted attention due to its strong penetrating power and ability to reflect the overall moisture content of materials. Traditional microwave moisture detection often uses linearly polarized waves. However, grain pellets are non-uniform, anisotropic, and strongly scattering media composed of solid particles and air. When linearly polarized waves propagate in such media, they experience severe depolarization effects, and their propagation parameters (such as attenuation and phase) strongly depend on the particle alignment and shape, resulting in poor repeatability and low accuracy of measurement results. Currently, there is a lack of microwave detection solutions that can effectively overcome the measurement errors caused by the anisotropy of grain particles. Summary of the Invention
[0004] This invention is made to solve the above-mentioned problems, and aims to provide a grain moisture detection system and method based on circularly polarized microwaves, so as to solve the problems of poor repeatability and low accuracy of microwave measurement caused by the anisotropy and random stacking of grain particles.
[0005] This invention provides a grain moisture detection system based on circularly polarized microwaves, characterized by the following features: a circularly polarized microwave transceiver module for transmitting circularly polarized microwave signals to a grain sample and receiving microwave signals after they penetrate the sample; a signal acquisition and processing module connected to the circularly polarized microwave transceiver module for acquiring microwave signal attenuation parameters; a detection chamber for containing the grain sample, with the circularly polarized microwave transceiver module positioned on both sides; and a calculation and control module for calculating the moisture content of the grain sample based on the attenuation parameters and a preset moisture prediction model.
[0006] The grain moisture detection system based on circularly polarized microwave provided by the present invention may also have the following feature: wherein the circularly polarized microwave transceiver module includes a pair of right-hand or left-hand circularly polarized antennas.
[0007] The grain moisture detection system based on circularly polarized microwave provided by the present invention may also have the following feature: wherein the circularly polarized antenna is a conical horn antenna.
[0008] The grain moisture detection system based on circularly polarized microwave provided by the present invention may also have the following feature: the detection chamber is a cavity structure with a circular cross-section.
[0009] The grain moisture detection system based on circularly polarized microwave provided by the present invention may also have the following feature: wherein the calculation and control module is further configured to control the circularly polarized microwave transceiver module to perform frequency scanning within a selected frequency band to obtain attenuation data at multiple frequency points.
[0010] The grain moisture detection system based on circularly polarized microwave provided by the present invention may also have the following feature: wherein the calculation and control module is further configured to perform a filtering algorithm on the attenuation data of the multiple frequency points to eliminate outliers before calculating the moisture content.
[0011] The grain moisture detection system based on circularly polarized microwave provided by this invention may also have the following feature: the filtering algorithm is a quadratic approximation average filtering algorithm.
[0012] The grain moisture detection system based on circularly polarized microwave provided by this invention may also have the following feature: the moisture prediction model is a multinomial regression model with temperature compensation.
[0013] This invention also provides a method for detecting grain moisture based on circularly polarized microwaves, comprising the following steps: Step S1, placing the grain sample to be tested in a detection chamber; Step S2, using circularly polarized microwaves to penetrate the grain sample to be tested and scanning within a specific frequency band to obtain attenuation data at multiple frequency points; Step S3, filtering the attenuation data to obtain a stable representative attenuation value; Step S4, inputting the representative attenuation value into a preset moisture prediction model to output the moisture content value.
[0014] The grain moisture detection method based on circularly polarized microwave provided by the present invention may also have the following features: step S2 includes scanning within a selected frequency band to obtain attenuation data at multiple frequency points, and step S3 includes using a filtering algorithm to process the multiple attenuation data to eliminate outliers. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the overall structure of the grain moisture detection system based on circularly polarized microwave in an embodiment of the present invention; Figure 2 This is a schematic diagram of a grain moisture detection method based on circularly polarized microwaves in an embodiment of the present invention; Figure 3 is a comparison of the S21 parameters of linearly polarized waves and circularly polarized waves penetrating corn piles with different stacking methods in an embodiment of the present invention. Figure 3(a) shows the S21 sweep curves after linearly polarized waves penetrate the two stacking models respectively, and Figure 3(b) shows the S21 sweep curves after circularly polarized waves penetrate the two stacking models respectively. Detailed Implementation
[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate a grain moisture detection system and method based on circularly polarized microwaves.
[0017] This embodiment provides a grain moisture detection system based on circularly polarized microwaves.
[0018] Figure 1 This is a schematic diagram of the overall structure of the grain moisture detection system based on circularly polarized microwave in an embodiment of the present invention.
[0019] like Figure 1 As shown, the grain moisture detection system based on circularly polarized microwave provided in this embodiment includes a circularly polarized microwave transceiver module, a signal acquisition and processing module, a detection chamber, and a calculation and control module.
[0020] The circularly polarized microwave transceiver module is used to generate and transmit circularly polarized microwave signals to the grain sample to be tested, and to receive the microwave signals after they penetrate the sample. In this embodiment, the circularly polarized microwave transceiver module includes a pair of right-hand circularly polarized conical horn antennas.
[0021] The signal acquisition and processing module is connected to the circularly polarized microwave transceiver module and is used to acquire the attenuation parameters of the microwave signal. In this embodiment, the signal acquisition and processing module is a vector network analyzer.
[0022] The testing chamber is used to hold the grain sample to be tested, with circularly polarized microwave transceiver modules placed on both sides. In this embodiment, the testing chamber is a cavity structure with a circular cross-section. The circular structure helps to reduce specular reflection interference, and the grain sample to be tested is placed inside.
[0023] The calculation and control module is used to calculate the moisture content of the grain sample to be tested based on the attenuation parameter and a preset moisture prediction model. In this embodiment, the calculation and control module performs the following steps: Step a: Control the circularly polarized microwave transceiver module to scan within the selected frequency band.
[0024] Step b: Obtain attenuation data for multiple frequency points from the signal acquisition and processing module.
[0025] Step c involves using a quadratic approximation average filtering algorithm to process the attenuated data in order to eliminate outliers.
[0026] Step d: Substitute the processed attenuation data into the temperature-compensated multinomial regression model to calculate the moisture content of the grain.
[0027] Figure 2 This is a schematic diagram of a grain moisture detection method based on circularly polarized microwaves in an embodiment of the present invention.
[0028] like Figure 2 As shown, the working process of the grain moisture detection system based on circularly polarized microwaves in this embodiment is as follows: First, grain particles fall from the feed hopper into the circular detection chamber. The calculation and control module (which can be an industrial computer or a processor integrated into the main control module; in this embodiment, it is an industrial computer) controls the circularly polarized microwave transceiver module to perform frequency scanning within a specific frequency range in specific steps. The transmitting antenna emits right-hand circularly polarized microwaves, which penetrate the grain layer and are received by the receiving antenna. The calculation and control module records the amplitude (i.e., attenuation Att) of the transmission coefficient S21.
[0029] Figure 3 is a comparison of the S21 parameters of linearly polarized waves and circularly polarized waves penetrating corn piles with different stacking methods in an embodiment of the present invention. Figure 3(a) shows the S21 sweep curves after linearly polarized waves penetrate the two stacking models respectively, and Figure 3(b) shows the S21 sweep curves after circularly polarized waves penetrate the two stacking models respectively.
[0030] The data processing then proceeds as follows: At each preset preferred frequency point, 10 rapid scans are performed. A "secondary approximation mean filtering algorithm" is applied to these 10 data points: First, the initial mean is calculated, and outliers exceeding a threshold (±2 standard deviations in this embodiment) are removed. The mean is then calculated again for the remaining data, and values with excessive deviations are removed again. Finally, the mean of the remaining data is used as the final attenuation value for that frequency point. Then, the final attenuation values from multiple preferred frequency points are averaged or weighted to obtain the characteristic attenuation amount used to calculate moisture content.
[0031] Finally, the moisture calculation process is as follows: the characteristic attenuation amount and the real-time detected sample temperature are substituted into the pre-calibrated moisture-attenuation-temperature mathematical model (in this embodiment, MC = a(T)*Att^3 + b(T)*Att^2 + c(T)*Att+ d(T)) to calculate the compensated moisture value.
[0032] This embodiment also provides a method for detecting grain moisture based on circularly polarized microwaves, the specific implementation steps of which are as follows: Step S1: Place the grain sample to be tested in the testing chamber.
[0033] Step S2: Use circularly polarized microwaves to penetrate the grain sample to be tested, and scan within the selected frequency band to obtain attenuation data at multiple frequency points.
[0034] Step S3: A filtering algorithm is used to process multiple attenuation data to eliminate outliers, thereby obtaining a stable representative attenuation value.
[0035] Step S4: Input the attenuation representative value into the preset moisture prediction model and output the moisture content value.
[0036] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.
[0037] The present invention has the following technical effects: 1. Resistance to anisotropic interference: Utilizing the rotational symmetry of circularly polarized microwaves, it is insensitive to the random arrangement and shape orientation of grain particles, fundamentally improving the repeatability and accuracy of measurements.
[0038] 2. Suppressing surface reflection: When circularly polarized waves encounter a smooth surface reflection, their rotation direction reverses. Using a co-rotating antenna can effectively suppress surface specular reflection interference, thereby enhancing the ability to extract useful information from the body.
[0039] 3. Overall Moisture Detection: Microwaves have strong penetrating power and can reflect the overall (volume) moisture of grain samples, rather than just surface moisture, making the results more representative.
[0040] 4. Online, non-destructive, and rapid: Enables online, non-destructive testing of grains with a short testing time (<60 seconds), meeting the needs of industrial online testing.
Claims
1. A grain moisture detection system based on circularly polarized microwaves, characterized in that, include: A circularly polarized microwave transceiver module is used to transmit circularly polarized microwave signals to a grain sample to be tested and to receive the microwave signals after they have penetrated the sample. The signal acquisition and processing module is connected to the circularly polarized microwave transceiver module and is used to acquire the attenuation parameters of the microwave signal. The testing chamber is used to hold the grain sample to be tested, and the circularly polarized microwave transceiver modules are placed on both sides of it. The calculation and control module is used to calculate the moisture content of the grain sample to be tested based on the attenuation parameters and the preset moisture prediction model.
2. The grain moisture detection system based on circularly polarized microwave according to claim 1, characterized in that: in, The circularly polarized microwave transceiver module includes a pair of right-hand or left-hand circularly polarized antennas.
3. The grain moisture detection system based on circularly polarized microwave according to claim 2, characterized in that: in, The circularly polarized antenna is a conical horn antenna.
4. The grain moisture detection system based on circularly polarized microwave according to claim 1, characterized in that: in, The detection chamber is a cavity structure with a circular cross-section.
5. The grain moisture detection system based on circularly polarized microwave according to claim 1, characterized in that: in, The calculation and control module is further configured to control the circularly polarized microwave transceiver module to perform frequency scanning within a selected frequency band in order to obtain attenuation data at multiple frequency points.
6. The grain moisture detection system based on circularly polarized microwave according to claim 1, characterized in that: in, The calculation and control module is also configured to perform a filtering algorithm on the attenuation data of the multiple frequency points to eliminate outliers before calculating the moisture content.
7. The grain moisture detection system based on circularly polarized microwave according to claim 6, characterized in that: in, The filtering algorithm is a quadratic approximation average filtering algorithm.
8. The grain moisture detection system based on circularly polarized microwave according to claim 1, characterized in that: in, The moisture prediction model is a multinomial regression model with temperature compensation.
9. A method for detecting grain moisture based on circularly polarized microwaves, characterized in that, Includes the following steps: Step S1: Place the grain sample to be tested in the testing chamber; Step S2: Use circularly polarized microwaves to penetrate the grain sample to be tested and scan within a specific frequency band to obtain attenuation data at multiple frequency points; Step S3: Filter the attenuation data to obtain a stable representative attenuation value; Step S4: Input the attenuation representative value into the preset moisture prediction model and output the moisture content value.
10. The grain moisture detection method based on circularly polarized microwave according to claim 9, characterized in that: in, Step S2 includes scanning within the selected frequency band to obtain attenuation data at multiple frequency points. Step S3 includes using a filtering algorithm to process multiple attenuated data to eliminate outliers.