Grain pile temperature detection method and system based on electromagnetic waves

Abstract

The invention relates to the technical field of grain temperature detection, discloses a grain pile temperature detection method and system based on electromagnetic waves, and aims at solving the problems that an existing method is high in cost and poor in accuracy, and the scheme mainly comprises the steps that the mapping relation between temperature and electromagnetic parameters is constructed; installing a sensor matrix in the grain pile; the temperature of the point position detected by the temperature probe of each sensor is obtained, each sensor is controlled to transmit and receive electromagnetic wave signals, and the frequency of the electromagnetic wave signals transmitted by each sensor corresponds to the temperature of the point position; constructing an electromagnetic wave propagation equation between any two sensors in the grain pile, and generating an electromagnetic wave propagation equation set; generating an electromagnetic wave distribution field according to the frequency of the electromagnetic wave signal transmitted by each sensor and the amplitude and phase of the received electromagnetic wave signal based on the electromagnetic wave propagation equation set; and generating a temperature distribution field according to the electromagnetic wave distribution field. The method reduces the cost, improves the accuracy, and is especially suitable for granaries.

Description

Technical Field

[0001] The present invention relates to the technical field of grain temperature detection, and particularly to a method and system for detecting the temperature of a grain pile based on electromagnetic waves. Background Art

[0002] Grain pile temperature detection refers to the process of real-time or periodic monitoring of the temperature inside and on the surface of a grain pile during the grain storage process. Through grain pile temperature detection, grain spoilage can be prevented, pest risk can be controlled, storage conditions can be optimized, and the safety and stability of stored grain can be ensured. However, as a porous granular medium, the temperature field distribution of a grain pile is affected by multiple factors such as environmental humidity, microbial activity, and stacking density, resulting in significant temperature differences inside, and uneven heat transfer of the grain, making it difficult for a single detection point to reflect the overall temperature distribution.

[0003] In the prior art, the main solution for grain pile temperature detection is to set up a temperature sensor matrix in the grain pile. First, the temperatures at different positions of the grain pile are collected by multiple temperature sensors in the temperature sensor matrix, and then a three-dimensional temperature distribution map of the grain pile is generated based on an interpolation algorithm. However, this method has at least the following problems: First, the accuracy of the temperature field completely depends on the number and distribution of temperature sensors. A large number of temperature sensors need to be buried inside the grain pile, which may damage the airtightness of the grain pile, and the probes are vulnerable to mechanical damage and fumigation corrosion, resulting in high maintenance costs. If the temperature sensors are sparsely arranged, the interpolation algorithm will cause a smoothing effect due to insufficient data and cannot capture local anomalies. At the same time, the temperature sensors may be sparsely or densely arranged due to installation limitations. In this case, the interpolation results are prone to problems such as over-weighting in the central region and error amplification in the edge region, resulting in a decrease in the accuracy of temperature field reconstruction. Second, the interpolation algorithm only depends on mathematical statistical laws and ignores the physical characteristics of the grain pile, and cannot reflect the dynamic changes of the actual temperature field. Third, if there are local high-temperature or low-temperature abnormal points in a certain part of the grain pile, the interpolation algorithm is prone to form a concentric circular temperature distribution around the abnormal temperature point, which does not conform to the actual heat conduction law of the grain pile and has poor accuracy. Summary of the Invention

[0004] The present invention aims to solve the problems of high cost and poor accuracy existing in the existing grain pile temperature detection methods, and proposes a method and system for detecting the temperature of a grain pile based on electromagnetic waves.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: In a first aspect, the present invention provides a method for detecting the temperature of a grain pile based on electromagnetic waves, and the method includes: Under an experimental environment, detect the electromagnetic parameters of the grain pile at different temperatures, and construct a mapping relationship between the temperature and the electromagnetic parameters; Install a sensor matrix in the grain pile, and each sensor in the sensor matrix includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module; Obtain the temperature at the location detected by the temperature probe of each sensor, and control each sensor to transmit and receive electromagnetic wave signals. The frequency of the electromagnetic wave signal transmitted by each sensor corresponds to the temperature at the location. Construct the electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set. Based on the frequency of the electromagnetic wave signal transmitted by each sensor, as well as the amplitude and phase of the received electromagnetic wave signal, and based on the electromagnetic wave propagation equation set, generate an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters. Based on the electromagnetic wave distribution field and based on the mapping relationship between temperature and electromagnetic parameters, generate a temperature distribution field for representing the temperature distribution, and determine the temperature at any location in the grain pile according to the temperature distribution field.

[0006] Furthermore, detect the electromagnetic parameters of the grain pile at different temperatures, including: At different temperatures, measure the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile through a vector network analyzer, determine the attenuation coefficient and phase delay of the electromagnetic wave according to the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile, and calculate the electromagnetic parameters at the corresponding temperature according to the attenuation coefficient and phase delay.

[0007] Furthermore, the electromagnetic parameters are permittivity, permeability or conductivity.

[0008] Furthermore, constructing the electromagnetic wave propagation equation between any two sensors in the grain pile includes: Based on Maxwell's equations, determine the wave equation of the electric field strength of the electromagnetic wave in the grain pile, and construct the electromagnetic wave propagation equation according to the wave equation of the electric field strength of the electromagnetic wave in the grain pile.

[0009] Furthermore, Maxwell's equations are as follows: ; ; ; ; The wave equation of the electric field strength in the grain pile is as follows: ; Wherein, represents the divergence operator, represents the curl operator, represents the Laplace operator, represents the electric displacement vector, represents the magnetic induction intensity, represents the electric field strength, represents the magnetic field strength, represents the current density, represents the magnetic permeability, represents the permittivity, represents the conductivity, represents the first-order derivative of the magnetic induction intensity with respect to time, represents the first-order derivative of the electric displacement vector with respect to time, represents the second-order derivative of the electric field strength with respect to time, represents the first-order derivative of the electric field strength with respect to time.

[0010] Furthermore, the electromagnetic wave propagation equation between any two sensors is as follows: ; ; ; ; ; where, represents the phase delay when the electromagnetic wave of the th sensor propagates to the th sensor, represents the propagation path of the electromagnetic wave of the th sensor propagating to the th sensor, represents the arc length parameter of the propagation path, used to describe the position on the propagation path, represents the position at the phase constant, represents the integration variable, represents the amplitude attenuation when the electromagnetic wave of the th sensor propagates to the th sensor, represents the natural exponential function, represents the position at the attenuation coefficient, represents the real part of the permittivity at the position at, represents the angular frequency of the electromagnetic wave signal, represents the pi, represents the frequency of the electromagnetic wave signal.

[0011] Furthermore, an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters is generated, including: Discretize the space where the grain pile is located into a grain pile grid, calculate the electromagnetic parameters corresponding to each grain pile grid according to the frequency of the electromagnetic wave signal emitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and based on the electromagnetic wave propagation equations, and generate an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters according to the electromagnetic parameters corresponding to each grain pile grid.

[0012] Further, generating a temperature distribution field for representing the temperature distribution includes: Determine the temperature corresponding to each grain pile grid according to the electromagnetic parameters corresponding to each grain pile grid and based on the mapping relationship between temperature and electromagnetic parameters, and generate a temperature distribution field for representing the temperature distribution according to the temperature corresponding to each grain pile grid.

[0013] Further, each sensor in the sensor matrix is encapsulated with a wave-transparent material.

[0014] In a second aspect, the present invention provides a grain pile temperature detection system based on electromagnetic waves, and the system includes: An experimental device for detecting the electromagnetic parameters of a grain pile at different temperatures in an experimental environment and constructing a mapping relationship between temperature and electromagnetic parameters; A sensor matrix installed in the grain pile, and each sensor includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module respectively; A main control device for obtaining the temperature of the location detected by the temperature probe of each sensor, and controlling each sensor to emit and receive electromagnetic wave signals, where the frequency of the electromagnetic wave signal emitted by each sensor corresponds to the temperature of the location; constructing an electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set; generating an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters according to the frequency of the electromagnetic wave signal emitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and based on the electromagnetic wave propagation equation set; generating a temperature distribution field for representing the temperature distribution according to the electromagnetic wave distribution field and based on the mapping relationship between temperature and electromagnetic parameters, and determining the temperature of any location in the grain pile according to the temperature distribution field.

[0015] The beneficial effects of the present invention are as follows: The method and system for detecting the temperature of a grain heap based on electromagnetic waves provided by the present invention dynamically correlate the propagation characteristics of electromagnetic wave signals with the temperature field. Based on the propagation characteristics of electromagnetic waves, using the phase delay and amplitude attenuation data between multiple pairs of sensors, and combining with the electromagnetic wave propagation model constructed based on Maxwell's equations, the electromagnetic parameters in the grain heap are inversely calculated, and then the electromagnetic parameters are converted into temperature. The electromagnetic wave propagation path covers the entire grain heap, and a single path can penetrate multiple regions. Combining the cross data of multiple pairs of sensors, even if the number of sensors is limited, temperature detection with a resolution of millimeters to centimeters can still be achieved, reducing the equipment cost and maintenance cost of the sensors, and reducing the degree of damage to the airtightness of the grain heap by the sensors; determining the temperature by inversely calculating the electromagnetic parameters is more in line with the real physical process. When the temperature gradient in the grain heap changes sharply due to uneven ventilation, electromagnetic inversion can accurately reflect the mutation boundary, further improving the accuracy of temperature detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a schematic flow chart of the method for detecting the temperature of a grain heap based on electromagnetic waves provided by the embodiment; Figure 2 FIG. is a schematic installation structure diagram of the sensor matrix provided by the embodiment; Figure 3 FIG. is a schematic transmission diagram of the electromagnetic wave signal provided by the embodiment; Figure 4 FIG. is a schematic structure diagram of the system for detecting the temperature of a grain heap based on electromagnetic waves provided by the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the present embodiment will be clearly and completely described below in conjunction with the accompanying drawings in the present embodiment.

[0018] In some processes described in the specification of the present invention and the above-mentioned accompanying drawings, there are multiple operations that appear in a specific order. However, it should be clearly understood that these operations may not be executed in the order in which they appear in this document or may be executed in parallel. The serial numbers of the operations are only used to distinguish different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations may be executed in sequence or in parallel.

[0019] The technical solution of the present invention is applicable to application scenarios that require temperature detection of grain heaps, such as temperature detection of rice, wheat, corn, etc. in granaries.

[0020] Since the existing solutions for detecting the temperature of a grain pile usually use a temperature sensor matrix to collect the temperatures at multiple points in the grain pile, and then use an interpolation algorithm to determine the temperatures at other points, and then generate the temperature distribution field of the grain pile. According to the research on the existing methods for detecting the temperature of a grain pile, the inventor found that the accuracy of the temperature distribution field in the existing technology completely depends on the number and distribution of temperature sensors, a large number of temperature sensors need to be arranged, the equipment cost and maintenance cost are high, the degree of damage to the airtightness of the grain pile is large, and the accuracy is poor.

[0021] Based on this, the technical solution of the present invention is proposed. In the present invention, in an experimental environment, the electromagnetic parameters of the grain pile at different temperatures are detected, and the mapping relationship between the temperature and the electromagnetic parameters is constructed; a sensor matrix is installed in the grain pile, and each sensor in the sensor matrix respectively includes a temperature probe, an electromagnetic wave transmitting module and an electromagnetic wave receiving module; the temperature of the point where each sensor is located detected by the temperature probe of each sensor is obtained, and each sensor is controlled to transmit and receive electromagnetic wave signals, and the frequency of the electromagnetic wave signal transmitted by each sensor corresponds to the temperature of the point where it is located; the electromagnetic wave propagation equation between any two sensors in the grain pile is constructed to generate an electromagnetic wave propagation equation set; according to the frequency of the electromagnetic wave signal transmitted by each sensor and the amplitude and phase of the received electromagnetic wave signal and based on the electromagnetic wave propagation equation set, an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters is generated; according to the electromagnetic wave distribution field and based on the mapping relationship between the temperature and the electromagnetic parameters, a temperature distribution field for representing the temperature distribution is generated, and the temperature of any point in the grain pile is determined according to the temperature distribution field.

[0022] It can be understood that a grain pile is composed of grain particles, and the change of temperature will change the molecular polarization characteristics (such as water activity, ion mobility) of the grain particles, resulting in the change of electromagnetic parameters. Based on this, the present invention first dynamically correlates the temperature of the grain pile with the electromagnetic parameters in an experimental environment, then uses sensors to detect the temperature of the point where they are located, and transmit and receive electromagnetic wave signals, and finally, based on the propagation characteristics of electromagnetic waves, uses the phase delay and amplitude attenuation data between multiple pairs of sensors, combined with the electromagnetic wave propagation model constructed based on Maxwell's equations, to invert the electromagnetic parameters in the grain pile, and then convert the electromagnetic parameters into temperature. The electromagnetic wave propagation path covers the entire grain pile, and a single path can penetrate multiple regions. Combining the cross data of multiple pairs of sensors, even if the number of sensors is limited, the temperature detection with a resolution of millimeters to centimeters can still be achieved, reducing the equipment cost and maintenance cost of the sensors, and reducing the degree of damage to the airtightness of the grain pile by the sensors; by inverting the electromagnetic parameters to determine the temperature, it is more in line with the real physical process. When the temperature gradient in the grain pile changes suddenly due to uneven ventilation, the electromagnetic inversion can accurately reflect the mutation boundary, further improving the accuracy of temperature detection.

[0023] Next, the technical solutions in this embodiment will be clearly and completely described in conjunction with the accompanying drawings in this embodiment. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0024] Figure 1 The flowchart of a method for detecting the temperature of a grain pile based on electromagnetic waves is shown. Please refer to Figure 1 This method includes the following steps: Step 1: Under an experimental environment, detect the electromagnetic parameters of the grain pile at different temperatures, and establish a mapping relationship between the temperature and the electromagnetic parameters.

[0025] It can be understood that the temperature dependence of the electromagnetic parameters of the grain pile stems from the coupling effect of multiple physical fields. The temperature change of the grain pile will cause moisture phase change, thermal expansion, biological metabolism, and changes in the electromagnetic wave propagation characteristics, thereby changing the electromagnetic parameters. Based on this, in this embodiment, a mapping relationship between the temperature and the electromagnetic parameters is established under an experimental environment.

[0026] In this embodiment, the electromagnetic parameters can be permittivity, permeability, or conductivity. Specifically, when the grains are heated and expanded, the porosity will be reduced and the bulk density will be increased, which leads to an increase in the number of scattering interfaces in the electromagnetic wave propagation path and an increase in the equivalent permittivity; high temperature (>20 °C) activates the respiration of microorganisms in the grain pile, releases CO2 and moisture, and at the same time increases the ion concentration, significantly enhancing the conductivity; the permeability of trace metal impurities (such as iron filings) in the grain pile will be slightly adjusted due to temperature changes. For example, high temperature may reduce the ordered arrangement of magnetic impurities, resulting in a decrease in permeability.

[0027] In this embodiment, to detect the electromagnetic parameters of the grain pile at different temperatures, at different temperatures, the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile can be measured by a vector network analyzer, the attenuation coefficient and phase delay of the electromagnetic wave can be determined according to the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile, and the electromagnetic parameters at the corresponding temperature can be calculated according to the attenuation coefficient and phase delay.

[0028] In practical applications, the grain pile can be compacted into a uniform cuboid or cylinder. At different temperatures, when electromagnetic waves vertically penetrate the grain pile, by measuring the transmission coefficient of the grain pile at a specific frequency and combining the amplitude and phase of the electromagnetic waves before and after penetration, the attenuation coefficient and phase delay of the electromagnetic waves can be calculated, and then the electromagnetic parameters of the grain pile can be inversely deduced. The amplitude attenuation is directly related to the loss characteristics of the medium. The greater the loss, the more obvious the amplitude attenuation of the electromagnetic waves. The phase change is related to the influence of the medium on the propagation speed of the electromagnetic waves. Different electromagnetic parameters will change the propagation speed of the electromagnetic waves, resulting in a phase change. Using a vector network analyzer, accurately measuring the amplitude and phase differences between the incident wave and the penetrated wave, and then through mathematical processing, the electromagnetic parameters such as the complex permittivity and complex permeability of the medium can be accurately calculated. At the same time, by measuring the ambient temperature of the grain medium, corresponding the temperature to the electromagnetic parameters, and finally constructing the mapping relationship between the temperature and electromagnetic parameters of the grain pile.

[0029] Step 2: Install a sensor matrix in the grain pile. Each sensor in the sensor matrix respectively includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module.

[0030] Please refer to Figure 2 , in practical applications, multiple sensors can be distributed and set in the grain pile. The spacing between adjacent sensors can be dynamically adjusted according to the size of the grain pile and the requirements of the monitoring resolution. Each sensor integrates a temperature probe (such as a thermocouple or a thermistor), an electromagnetic wave transmitting module, and an electromagnetic wave receiving module. The temperature probe is used to detect the temperature at its own location. The electromagnetic wave transmitting module is used to transmit electromagnetic wave signals. The electromagnetic wave receiving module is used to receive electromagnetic wave signals. Each sensor is respectively communicatively connected to the main control device. The main control device is used to receive the temperature detected by the sensor, control the sensor to emit electromagnetic wave signals, and receive the relevant data of the received electromagnetic wave signals sent by the sensor.

[0031] In this embodiment, each sensor in the sensor matrix adopts a passive sensor, which does not require battery power supply, and the sensor is encapsulated with a wave-transparent material (such as polypropylene) to reduce the interference to the electromagnetic wave signal and further improve the accuracy of temperature detection.

[0032] Step 3: Obtain the temperature at the location detected by the temperature probe of each sensor, and control each sensor to emit and receive electromagnetic wave signals. The frequency of the electromagnetic wave signals emitted by each sensor corresponds to the temperature at its location.

[0033] The temperature probe of each sensor real-time detects the temperature at its location. The temperature data is transmitted to the main control device through analog-to-digital conversion or a direct digital interface. Please refer to Figure 3, for any two sensors, the main control device generates an excitation signal corresponding to the electromagnetic wave frequency according to the temperature value to control the electromagnetic wave transmitting module of the sensor to transmit an electromagnetic wave signal of the corresponding frequency. The electromagnetic wave receiving module of each sensor receives the electromagnetic wave signals transmitted by other sensors and returns the relevant data of the received electromagnetic wave signals to the main control device.

[0034] Step 4: Construct the electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set.

[0035] In this embodiment, constructing the electromagnetic wave propagation equation between any two sensors in the grain pile specifically includes: Based on Maxwell's equations, determine the wave equation of the electric field strength of the electromagnetic wave in the grain pile, and construct the electromagnetic wave propagation equation according to the wave equation of the electric field strength of the electromagnetic wave in the grain pile.

[0036] Maxwell's Equations is a set of partial differential equations describing the relationship between electric fields, magnetic fields, charge density, and current density. This set of equations consists of four equations, namely Gauss's law describing how charges generate electric fields, Gauss's magnetic law indicating the non-existence of magnetic monopoles, Faraday's law of electromagnetic induction explaining how time-varying magnetic fields generate electric fields, and Maxwell-Ampere's law showing how currents and time-varying electric fields generate magnetic fields.

[0037] In this embodiment, in a passive, linear, and isotropic grain pile medium, the differential form of Maxwell's equations is as follows: ; ; ; ; From Maxwell's equations, the wave equation of the electric field strength of the electromagnetic wave in the grain pile can be deduced as follows: ; Among them, represents the divergence operator, represents the curl operator, represents the Laplace operator, represents the electric displacement vector, represents the magnetic induction intensity, represents the electric field strength, represents the magnetic field strength, represents the current density, represents the magnetic permeability, represents the permittivity, represents the conductivity, represents the first derivative of the magnetic induction intensity with respect to time, represents the first derivative of the electric displacement vector with respect to time, represents the second derivative of the electric field strength with respect to time, represents the first derivative of the electric field strength with respect to time.

[0038] When an electromagnetic wave propagates in the grain heap medium, the phase and amplitude changes are related to the path integral. Based on this, according to the wave equation of the electric field strength of the electromagnetic wave in the grain heap, for any two sensors , an electromagnetic wave propagation equation can be established to describe the electromagnetic wave propagation characteristics (phase delay and amplitude attenuation) from the -th sensor to the -th sensor as follows: ; ; ; ; ; where, represents the phase delay when the electromagnetic wave of the -th sensor propagates to the -th sensor, represents the propagation path of the electromagnetic wave of the -th sensor to the -th sensor, represents the arc length parameter of the propagation path, used to describe the position on the propagation path, represents the position at which the phase constant is located, characterizing the phase change per unit length when the electromagnetic wave propagates in the medium, represents the integration variable, represents the amplitude attenuation when the electromagnetic wave of the -th sensor propagates to the -th sensor, represents the natural exponential function, represents the position at which the attenuation coefficient is located, characterizing the energy attenuation per unit length when the electromagnetic wave propagates in the medium, represents the real part of the dielectric constant at the position , represents the angular frequency of the electromagnetic wave signal, represents the pi, represents the frequency of the electromagnetic wave signal.

[0039] In the above electromagnetic wave propagation equation, the phase delay and amplitude attenuation of electromagnetic wave propagation are related to the medium characteristics at each point on the path. By integrating along the path, the propagation characteristics of electromagnetic waves in inhomogeneous media can be accurately described, further improving the accuracy of temperature detection. In addition, the attenuation of electromagnetic waves is determined by the absorption characteristics of the medium, and the absorption process usually follows an exponential law. Therefore, the linear integral can be mapped to the actual attenuation amplitude through an exponential function. Through integration and exponential function, the propagation behavior of electromagnetic waves in complex media can be accurately modeled, providing a mathematical basis for subsequent temperature inversion.

[0040] Step 5: Generate an electromagnetic wave distribution field representing the electromagnetic parameter distribution based on the frequency of the electromagnetic wave signal emitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and the electromagnetic wave propagation equation set.

[0041] In this embodiment, generating an electromagnetic wave distribution field representing the electromagnetic parameter distribution includes: Discretize the space where the grain pile is located into grain pile grids, calculate the electromagnetic parameters corresponding to each grain pile grid based on the frequency of the electromagnetic wave signal emitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and the electromagnetic wave propagation equation set, and generate an electromagnetic wave distribution field representing the electromagnetic parameter distribution according to the electromagnetic parameters corresponding to each grain pile grid.

[0042] In practical applications, first divide the grain pile space into grain pile grids, where represents the length of the grain pile grid, represents the width of the grain pile grid, represents the height of the grain pile grid. The specific size of the grain pile grid can be set according to the detection resolution requirements (such as 1 cm³). At the same time, it is necessary to determine the position information of each grain pile grid relative to the sensor to determine the position of the electromagnetic wave on the propagation path. Then, for any two sensors, discretize the path integral for each grain pile grid on the electromagnetic wave propagation path. Then, determine the phase delay and amplitude attenuation of the electromagnetic wave signal on the propagation path according to the amplitude and phase of the received electromagnetic wave signal. Substitute the frequency of the electromagnetic wave signal emitted by each sensor and the phase delay and amplitude attenuation of the electromagnetic wave signal on the propagation path into the corresponding equations in the electromagnetic wave propagation equation set, and the electromagnetic parameters of each grain pile grid can be inversely obtained. Finally, map the electromagnetic parameters of each grain pile grid obtained by inversion to the three-dimensional space coordinates of the grain pile, and an electromagnetic wave distribution field representing the electromagnetic parameter distribution of the grain pile can be obtained.

[0043] By discretizing the grain pile into grids, constructing an electromagnetic wave propagation equation set, and inversely solving, the finally generated electromagnetic parameter distribution field can reflect the electromagnetic parameter distribution inside the grain pile with high resolution.

[0044] Step 6: Generate a temperature distribution field for representing the temperature distribution based on the electromagnetic wave distribution field and the mapping relationship between temperature and electromagnetic parameters, and determine the temperature at any point in the grain pile according to the temperature distribution field.

[0045] Specifically, according to the electromagnetic parameters of each grain pile grid and based on the mapping relationship between temperature and electromagnetic parameters constructed in Step 1, the temperature of each grain pile grid can be obtained. Mapping the temperature of each grain pile grid to the three-dimensional space coordinates of the grain pile can obtain the electromagnetic wave distribution field representing the electromagnetic parameter distribution of the grain pile. When it is necessary to determine the temperature of a certain point in the grain pile, directly take the temperature of the grain pile grid where the point is located to achieve the determination of the temperature at any point in the grain pile.

[0046] In summary, the grain pile temperature detection method based on electromagnetic waves provided in this embodiment dynamically correlates the electromagnetic wave signal propagation characteristics with the temperature field. Based on the propagation characteristics of electromagnetic waves, using the phase delay and amplitude attenuation data between multiple sensor pairs, combined with the electromagnetic wave propagation model constructed based on Maxwell's equations, the electromagnetic parameters in the grain pile are inversely calculated, and then the electromagnetic parameters are converted into temperature. The electromagnetic wave propagation path covers the entire grain pile, and a single path can penetrate multiple regions. Combining the cross data of multiple sensor pairs, even if the number of sensors is limited, temperature detection with a resolution of millimeters to centimeters can still be achieved, reducing the equipment cost and maintenance cost of the sensors, and reducing the degree of damage to the airtightness of the grain pile by the sensors; determining the temperature by inversely calculating the electromagnetic parameters is more in line with the real physical process. When the temperature gradient in the grain pile changes sharply due to uneven ventilation, electromagnetic inversion can accurately reflect the mutation boundary, further improving the accuracy of temperature detection.

[0047] Based on the above solution, this embodiment further provides a grain pile temperature detection system based on electromagnetic waves. Please refer to Figure 4 , the system includes: An experimental device for detecting the electromagnetic parameters of the grain pile at different temperatures in an experimental environment and constructing a mapping relationship between temperature and electromagnetic parameters; A sensor matrix installed in the grain pile, and each sensor includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module; The main control device is used to obtain the temperature of the location detected by the temperature probe of each sensor, and control each sensor to transmit and receive electromagnetic wave signals. The frequency of the electromagnetic wave signal transmitted by each sensor corresponds to the temperature of the location; construct the electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set; based on the frequency of the electromagnetic wave signal transmitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and the electromagnetic wave propagation equation set, generate an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters; based on the electromagnetic wave distribution field and the mapping relationship between temperature and electromagnetic parameters, generate a temperature distribution field for representing the temperature distribution, and determine the temperature of any location in the grain pile according to the temperature distribution field.

[0048] It can be understood that since the grain pile temperature detection system based on electromagnetic waves described in this embodiment is a system for implementing the grain pile temperature detection method described in the embodiment, for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple. For the relevant parts, please refer to the partial description of the method, and details will not be repeated here.

Claims

1. An electromagnetic wave-based method for detecting the temperature of a grain pile, characterized in that, The method includes: Under an experimental environment, detecting the electromagnetic parameters of a grain pile at different temperatures and constructing a mapping relationship between the temperature and the electromagnetic parameters; Installing a sensor matrix in the grain pile, where each sensor in the sensor matrix includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module respectively; Obtaining the temperature of the location where each sensor's temperature probe is located, and controlling each sensor to transmit and receive electromagnetic wave signals, where the frequency of the electromagnetic wave signals transmitted by each sensor corresponds to the temperature of the location; Constructing an electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set; Based on the frequency of the electromagnetic wave signals transmitted by each sensor, as well as the amplitude and phase of the received electromagnetic wave signals and based on the electromagnetic wave propagation equation set, generating an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters; Based on the electromagnetic wave distribution field and based on the mapping relationship between the temperature and the electromagnetic parameters, generating a temperature distribution field for representing the temperature distribution, and determining the temperature of any location in the grain pile according to the temperature distribution field.

2. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 1, wherein Detecting the electromagnetic parameters of the grain pile at different temperatures includes: At different temperatures, measuring the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile through a vector network analyzer, determining the attenuation coefficient and phase delay of the electromagnetic wave according to the amplitude and phase of the electromagnetic wave before and after penetrating the grain pile, and calculating the electromagnetic parameters at the corresponding temperature according to the attenuation coefficient and phase delay.

3. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 1, wherein The electromagnetic parameters are permittivity, permeability, or conductivity.

4. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 3, characterized in that, Constructing an electromagnetic wave propagation equation between any two sensors in the grain pile includes: Based on Maxwell's equations, determining the wave equation of the electric field strength of the electromagnetic wave in the grain pile, and constructing an electromagnetic wave propagation equation according to the wave equation of the electric field strength of the electromagnetic wave in the grain pile.

5. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 4, wherein Maxwell's equations are as follows: ； ； ； ； The wave equation of the electric field strength in the grain pile is as follows: ； Among them, represents the divergence operator, represents the curl operator, represents the Laplace operator, represents the electric displacement vector, represents the magnetic induction intensity, represents the electric field strength, represents the magnetic field strength, represents the current density, represents the magnetic permeability, represents the permittivity, represents the conductivity, represents the first-order derivative of the magnetic induction intensity with respect to time, represents the first-order derivative of the electric displacement vector with respect to time, represents the second-order derivative of the electric field strength with respect to time, represents the first-order derivative of the electric field strength with respect to time.

6. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 5, wherein The electromagnetic wave propagation equation between any two sensors is as follows: ； ； ； ； ； Among them, represents the phase delay when the electromagnetic wave of the th sensor propagates to the th sensor. represents the propagation path of the electromagnetic wave of the th sensor propagating to the th sensor. represents the arc length parameter of the propagation path, which is used to describe the position on the propagation path. represents the position at the phase constant. represents the integration variable. represents the amplitude attenuation when the electromagnetic wave of the th sensor propagates to the th sensor. represents the natural exponential function. represents the attenuation coefficient at the position . represents the real part of the dielectric constant at the position . represents the angular frequency of the electromagnetic wave signal. represents the pi. represents the frequency of the electromagnetic wave signal.

7. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 6, wherein Generating an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters includes: Discretizing the space where the grain pile is located into grain pile grids, calculating the electromagnetic parameters corresponding to each grain pile grid based on the frequency of the electromagnetic wave signals transmitted by each sensor, as well as the amplitude and phase of the received electromagnetic wave signals and based on the electromagnetic wave propagation equation set, and generating an electromagnetic wave distribution field for representing the distribution of electromagnetic parameters according to the electromagnetic parameters corresponding to each grain pile grid.

8. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 7, wherein Generating a temperature distribution field for representing the temperature distribution includes: Determining the temperature corresponding to each grain pile grid based on the electromagnetic parameters corresponding to each grain pile grid and based on the mapping relationship between the temperature and the electromagnetic parameters, and generating a temperature distribution field for representing the temperature distribution according to the temperature corresponding to each grain pile grid.

9. The method for detecting the temperature of a grain pile based on electromagnetic waves according to claim 1, wherein Each sensor in the sensor matrix is encapsulated with a wave-transparent material.

10. The grain pile temperature detection system based on electromagnetic waves is characterized in that, The system includes: An experimental device for detecting the electromagnetic parameters of a grain pile at different temperatures under an experimental environment and constructing a mapping relationship between the temperature and the electromagnetic parameters; A sensor matrix installed in the grain pile, where each sensor includes a temperature probe, an electromagnetic wave transmitting module, and an electromagnetic wave receiving module respectively; The main control device is used to obtain the temperature of the location detected by the temperature probe of each sensor, and control each sensor to transmit and receive electromagnetic wave signals. The frequency of the electromagnetic wave signal transmitted by each sensor corresponds to the temperature of the location; construct the electromagnetic wave propagation equation between any two sensors in the grain pile to generate an electromagnetic wave propagation equation set; generate an electromagnetic wave distribution field representing the electromagnetic parameter distribution based on the frequency of the electromagnetic wave signal transmitted by each sensor, the amplitude and phase of the received electromagnetic wave signal, and based on the electromagnetic wave propagation equation set; generate a temperature distribution field representing the temperature distribution based on the electromagnetic wave distribution field and based on the mapping relationship between temperature and electromagnetic parameters, and determine the temperature of any location in the grain pile according to the temperature distribution field.

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