Soil moisture information sensing system based on electromagnetic wave signals
阅读说明：本技术 一种基于电磁波信号的土壤水分信息感知系统 (Soil moisture information sensing system based on electromagnetic wave signals ) 是由 胡必玲 仝钰 谢飞 陈澳迎 吴玉杰 于驰 于 2021-06-29 设计创作，主要内容包括：本发明涉及农业土壤采样技术领域,特别涉及一种基于电磁波信号的土壤水分信息感知系统,包括：电磁波信号发射器、若干个电磁波信号接收天线、上位机；所述电磁波信号接收天线与上位机连接；所述系统的工作步骤为S1、电磁波信号发射器发射数据包；S2、土壤中的电磁波信号接收天线阵列接收信号并发送到上位机中；S3、上位机对数据进行处理后得到土壤水分信息。本发明的有益效果在于：商用土壤湿度传感器的高成本限制了土壤感知技术的和精准灌溉技术在大部分发展中地区和中小农场中的使用,本发明提出的土壤信息感知系统为他们提供了一种更加低成本的选择,在让小农户采用数据驱动的农业技术方面迈出了一步。(The invention relates to the technical field of agricultural soil sampling, in particular to a soil moisture information sensing system based on electromagnetic wave signals, which comprises: the device comprises an electromagnetic wave signal transmitter, a plurality of electromagnetic wave signal receiving antennas and an upper computer; the electromagnetic wave signal receiving antenna is connected with an upper computer; the working steps of the system are S1, the electromagnetic wave signal emitter emits a data packet; s2, receiving the signals by the electromagnetic wave signal receiving antenna array in the soil and sending the signals to the upper computer; and S3, processing the data by the upper computer to obtain soil moisture information. The invention has the beneficial effects that: the high cost of commercial soil moisture sensors limits the use of soil sensing technology and precision irrigation technology in most developing regions and small and medium-sized farms, and the soil information sensing system provided by the invention provides a lower-cost choice for the small and medium-sized farms, and makes a step in the aspect of enabling small farmers to adopt data-driven agricultural technology.)
1. A soil moisture information sensing system based on electromagnetic wave signals is characterized by comprising an electromagnetic wave signal transmitter, an electromagnetic wave signal receiving antenna array and an upper computer; the electromagnetic wave signal receiving antenna array is connected with an upper computer; the working steps of the system are
S1, the electromagnetic wave signal emitter emits an electromagnetic wave signal;
s2, receiving the signals by the electromagnetic wave signal receiving antenna array and sending the signals to an upper computer;
and S3, processing the data by the upper computer to obtain soil moisture information.
2. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 1, wherein said upper computer supports MIMO technology.
3. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 1, wherein said array of electromagnetic wave signal receiving antennas is disposed in the soil to be measured.
4. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 1, further comprising a sealed box; the electromagnetic wave signal receiving antenna array is arranged in the sealed box.
5. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 1, wherein said electromagnetic wave signal receiving antenna array comprises a plurality of electromagnetic wave signal receiving antennas, said electromagnetic wave signal receiving antennas being arranged in a straight line at equal distances to form a receiving antenna array.
6. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 5, wherein said plurality of electromagnetic wave receiving antennas are connected to the upper computer through cables having the same length.
7. The soil moisture information sensing system based on electromagnetic wave signals, as claimed in claim 1, wherein the frequency range of the electromagnetic wave emitted by the electromagnetic wave signal emitter is 2400MHz to 2483.5 MHz.
8. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 1, wherein the step S3 is specifically:
s31, the upper computer acquires channel state information of each antenna in the electromagnetic wave signal receiving antenna array;
s32, obtaining the shortest path in the multipath channel based on the MUSIC algorithm, and calculating the relative TOF of the adjacent antenna;
s33, establishing an air-soil signal propagation model;
s34, calculating the apparent dielectric constant of the soil according to the relative TOF and the air-soil signal propagation model;
and S35, converting the apparent dielectric constant into soil humidity.
9. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 8, wherein the step S32 is specifically: relative TOF of shortest path on adjacent antennas is Δ T ═ Tl,m-tl,n；
Wherein t isl,mAbsolute time of arrival, t, for the mth antenna path ll,nThe absolute arrival time of the nth antenna path l, wherein the path l is the path along which the signal propagation on each antenna is shortest.
10. The system for sensing soil moisture information based on electromagnetic wave signals as claimed in claim 8, wherein the step S34 is specifically: in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The angle of inclination of the antenna array is theta4；
Electromagnetic wave signalTime difference of arrival at two adjacent receiving antennasΔt＝Δl1-nΔl2+nΔl3；
Can be obtained from the above formula
The propagation velocity of the electromagnetic wave signal in the soil isRefractive index
From Δ T ═ Δ l/c, calculate ∈aA value of (d);
in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The included angle between the antenna array and the horizontal plane is theta4(ii) a The propagation speed of the electromagnetic wave in the air is c, and the apparent dielectric constant of the soil is epsilona，Δl1、Δl2、Δl3The path difference of the electromagnetic wave signals received by the adjacent receiving antennas entering the soil, the path difference after the soil refraction and the path difference entering the receiving antennas are respectively.
Technical Field
The invention relates to the technical field of agricultural soil sampling, in particular to a soil moisture information sensing system based on electromagnetic wave signals.
Background
At present, the soil sensing technology based on wireless signals at home and abroad is mainly divided into two types: sensing soil by utilizing radio frequency; and collecting soil information by using a sensor network.
In the field of soil sensing by using radio frequency, radio frequency sensing technologies can be divided into two types, namely remote sensing technologies and ToF-based technologies. Remote sensing has proven to be a successful method of estimating soil moisture over the past two decades by estimating soil dielectric properties from soil surface emissivity, and thus soil moisture. Various low frequencies (X, C and L-band) are commonly used to detect the moisture content of bare or vegetation soil surfaces. C-band and X-band sensors (e.g., AMSR-E, ASCAT, RADARSAT, WindSAT) onboard various satellites have shown potential for global surface (skin) moisture measurement. Several satellite-based L-band radiometers and radars including SMOS, bottle base ocean salinity and SMAP and 1.26GHz instrumentation were placed on orbit to monitor near surface soil moisture and ocean salinity (0-5 cm) globally over the past few years. The remote sensing technology senses the soil humidity by utilizing the dependence of the soil reflectivity on the soil humidity. However, these methods have low spatial resolution, from 1m to 10km, and can only detect moisture on a shallow surface of soil with a depth of several centimeters. ToF-based technologies such as ground penetrating radar and TDR. The method for measuring soil humidity by using ground penetrating radar mainly comprises four methods: measuring soil humidity by using the speed of the reflected wave; measuring the water content of the soil by using the ground wave velocity; determining the water content of the soil according to the transmission wave velocity between the drill holes; and determining the water content of the soil according to the surface reflection coefficient. Time Domain Reflectometry (TDR) is a non-destructive method of measuring soil moisture content developed by Davis and Chudobiak (1975). It is based on the method proposed by Vernam-Fei-Er-Ge (1969). The Time Domain Reflectometry (TDR) method enables us to obtain soil moisture content and conductivity simultaneously with a single probe with minimal disturbance to the soil. Both methods can provide good spatial resolution, but these methods rely on specialized ultra-wideband systems to obtain accurate ToF estimates and are therefore very expensive. An underground sensor network is generally composed of underground soil probes and wireless communication nodes, wherein wireless signals are responsible for communication, not sensing. Soil probes are typically commercially available soil sensors, the high cost of which limits the size of the sensor network. However, low cost soil probes are not an ideal choice in terms of accuracy and performance.
Disclosure of Invention
In order to solve the problem that the cost is increased by designing an expensive special soil detector, the invention provides a soil moisture information sensing system based on electromagnetic wave signals, and the specific scheme is as follows:
a soil moisture information sensing system based on electromagnetic wave signals comprises an electromagnetic wave signal transmitter, an electromagnetic wave signal receiving antenna array and an upper computer; the electromagnetic wave signal receiving antenna array is connected with an upper computer; the working steps of the system are
S1, the electromagnetic wave signal emitter emits an electromagnetic wave signal;
s2, receiving the signals by the electromagnetic wave signal receiving antenna array and sending the signals to an upper computer;
and S3, processing the data by the upper computer to obtain soil moisture information.
Specifically, the upper computer supports the MIMO technology.
Specifically, the electromagnetic wave signal receiving antenna array is arranged in soil to be measured.
Particularly, the device also comprises a sealing box; the electromagnetic wave signal receiving antenna array is arranged in the sealed box.
Specifically, the electromagnetic wave signal receiving antenna array comprises a plurality of electromagnetic wave signal receiving antennas, and the electromagnetic wave receiving antennas are arranged at equal intervals along a straight line to form the receiving antenna array.
Specifically, the electromagnetic wave receiving antennas are connected with an upper computer through cables with the same length.
Specifically, the frequency range of the electromagnetic wave emitted by the electromagnetic wave signal emitter is 2400 MHz-2483.5 MHz.
Specifically, the step S3 specifically includes:
s31, the upper computer acquires channel state information of each antenna in the electromagnetic wave signal receiving antenna array;
s32, obtaining the shortest path in the multipath channel based on the MUSIC algorithm, and calculating the relative TOF of the adjacent antenna;
s33, establishing an air-soil signal propagation model;
s34, calculating the apparent dielectric constant of the soil according to the relative TOF and the air-soil signal propagation model;
and S35, converting the apparent dielectric constant into soil humidity.
Specifically, step S32 specifically includes: relative TOF of shortest path on adjacent antennas is Δ T ═ Tl,m-tl,n；
Wherein t isl,mAbsolute time of arrival, t, for the mth antenna path ll,nThe absolute arrival time of the nth antenna path l, wherein the path l is the path along which the signal propagation on each antenna is shortest.
Specifically, step S34 specifically includes: in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The angle of inclination of the antenna array is theta4；
Time difference of arrival of electromagnetic wave signals on two adjacent receiving antennasΔt＝Δl1-nΔl2+nΔl3；
Can be obtained from the above formula
The propagation velocity of the electromagnetic wave signal in the soil isRefractive index
From Δ T ═ Δ l/c, calculate ∈aA value of (d);
in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The included angle between the antenna array and the horizontal plane is theta4(ii) a The propagation speed of the electromagnetic wave in the air is c, and the apparent dielectric constant of the soil is epsilona，Δl1、Δl2、Δl3The path difference of the electromagnetic wave signals received by the adjacent receiving antennas entering the soil, the path difference after the soil refraction and the path difference entering the receiving antennas are respectively.
The invention has the beneficial effects that:
(1) the high cost of the commercial soil humidity sensor limits the use of the soil sensing technology and the precise irrigation technology in most developing regions and medium and small farms, the soil information sensing system provided by the invention provides a lower-cost choice for the soil information sensing technology and makes a step for small farmers to adopt data-driven agricultural technology.
(2) The cost of the system can be reduced by using the emission frequency of the unlicensed electromagnetic waves of 2400 MHz-2483.5 MHz.
(3) The electromagnetic wave signal receiving antennas are arranged at equal intervals along a straight line, so that subsequent calculation is facilitated.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of the mechanism of the present invention;
FIG. 2 is a flow chart of the working steps of the present invention;
fig. 3 is a schematic view of an air-soil signal propagation model.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 and 2, the invention discloses a soil moisture information sensing system based on electromagnetic wave signals, comprising:
the device comprises an electromagnetic wave signal transmitter, a plurality of electromagnetic wave signal receiving antennas and an upper computer; the electromagnetic wave signal receiving antenna is connected with an upper computer; the working steps of the system are
S1, transmitting a data packet by an electromagnetic wave signal transmitter;
s2, receiving the signals by the electromagnetic wave signal receiving antenna array in the soil and sending the signals to the upper computer;
and S3, processing the data by the upper computer to obtain soil moisture information.
The upper computer supports the MIMO technology.
The electromagnetic wave signal receiving antenna array is arranged in soil to be detected.
The device also comprises a sealing box; the electromagnetic wave signal receiving antenna array is arranged in the sealed box.
The electromagnetic wave receiving antennas are arranged in a straight line to form a receiving antenna array.
The electromagnetic wave receiving antennas are connected with an upper computer through cables with the same length.
The cable is an SMA cable.
The frequency of the electromagnetic wave emitted by the electromagnetic wave signal emitter is 2.4GHZ
The step S3 specifically includes:
s31, the upper computer acquires channel state information of each antenna in the electromagnetic wave signal receiving antenna array;
s32, obtaining the shortest path in the multipath channel based on the MUSIC algorithm, and calculating the relative TOF of the adjacent antenna;
s33, establishing an air-soil signal propagation model;
s34, calculating the apparent dielectric constant of the soil according to the relative TOF and the air-soil signal propagation model;
and S35, converting the apparent dielectric constant into soil humidity.
Step S32 specifically includes: relative TOF of shortest path on adjacent antennas is Δ T ═ Tl,m-tl,n；
Wherein t isl,mAbsolute time of arrival, t, for the mth antenna path ll,nThe absolute arrival time of the nth antenna path l, wherein the path l is the path along which the signal propagation on each antenna is shortest.
Step S34 specifically includes: in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The angle of inclination of the antenna array is theta4
Time difference of arrival of electromagnetic wave signals on two adjacent receiving antennasΔt＝Δl1-nΔl2+nΔl3；
Can be obtained from the above formula
The propagation velocity of the electromagnetic wave signal in the soil isRefractive index
By Δ T ═ Δl/c, calculating eaA value of (d);
in the air-soil interface, the incident angle of the electromagnetic wave signal from the air to the soil is theta1Angle of refraction theta2(ii) a The incident angle of the electromagnetic wave signal entering the receiving antenna from the soil is theta3(ii) a The antenna array forms an included angle theta with the horizontal plane4(ii) a The propagation speed in the air is c, and the apparent dielectric constant of the soil is epsilona，Δl1、Δl2、Δl3The path difference of the electromagnetic wave signals received by the adjacent receiving antennas entering the soil, the path difference after the soil refraction and the path difference entering the receiving antennas are respectively.
The host computer is the computer that has the MIMO function, electromagnetic wave signal transmitter is that WIFI signal transmitter transmit frequency is 70MHZ for 2.4GHZ bandwidth, adopts three WIFI signal receiver to constitute electromagnetic wave signal reception antenna array, and WIFI signal receiver equidistance is arranged, and three WIFI signal receiver sets up respectively in the soil apart from ground 4.5cm, 9cm, 13.5cm, and the antenna array is 88 degrees with the contained angle of horizontal plane, and the synchronous as example of sending end and receiving end:
and acquiring the absolute arrival time ToF of the signal under different frequency subcarriers of each path of each antenna by using an MUSIC algorithm based on the collected CSI data, namely the CSI matrix acquired by the three antennas under different frequency f subcarriers. Defining the absolute arrival time of the signal on the mth antenna path as tl,mAnd the path l is the path with the shortest signal propagation on the mth antenna, and the path with the lowest absolute arrival time is the shortest path because the time of the sending end and the receiving end is synchronous. Calculating the relative ToF of the shortest path between two adjacent antennas as T ═ Tl,m-tl,n
As shown in fig. 3 below, based on an air-soil signal propagation model, where d is the distance between antennas on an antenna array, θ1Is the angle of incidence, θ2Angle of refraction, θ3Is the angle of incidence, θ, of the antenna array4Is the rotation angle of the antenna array. And establishing a relation between the relative ToF and the dielectric constant of the soil by using the geometry and the Snell's law of refraction, and calculating the apparent dielectric constant of the soil.The method comprises the following specific steps:
the path difference between two adjacent antennas is composed of three parts, Deltal1，Δl2，Δl3. Defining the propagation speed of the signal in the air as c, and the apparent dielectric constant of the soil as EaThe propagation velocity of the signal in the soil isDefining refractive index
The time difference of arrival Δ l of the signal on two adjacent antennas can be expressed asΔl＝Δl1- nΔl2+nΔl3。
From the geometric knowledge and Snell's law of refraction, it can be deduced
By Δ T ═ Δ l/c, and θ at the time of experimental deployment1D is fixed to 4.5cm,. theta.4Fixed at 88 deg., then can deduce ∈a。
The apparent dielectric constant was converted to a soil moisture value based on the model in the GS3 sensor manual.
vwc is defined as the water content of the soil.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
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