A patrol positioning device and method based on low-frequency induction

Abstract

A patrol positioning method based on low-frequency induction is used to locate a source to be located using a beacon, comprising the following steps: Step 1. Setting a standard beacon for sensitivity normalization; Step 2. Establishing an RSSI-distance model f between the standard beacon and the source to be located; Step 3. The source to be located continuously transmits a low-frequency signal for communicating with the beacon, and when the beacon establishes a high-frequency signal connection with the source to be located, the source to be located is located. The present invention also discloses a patrol positioning device based on low-frequency induction, comprising a plurality of beacons, at least one source to be located, and a PC terminal. The present invention utilizes a probability distribution function to locate the source to be located, thereby solving the problem of large positioning errors when multiple beacons are located in the presence of strong metal interference. At the same time, the computational cost of multiple beacon positioning is reduced by the probability superposition method, thereby increasing the flexibility of positioning and also improving positioning accuracy.

Description

Technical Field

[0001] The present invention belongs to the field of information technology and relates to positioning technology, and in particular to a patrol positioning device and method based on low-frequency induction. Background Art

[0002] With the improvement of the accuracy of indoor positioning technology, more and more industries are applying indoor positioning technology to provide accurate positioning information. This includes the need to detect the location of patrol personnel in certain scenarios to determine whether they have reached certain key locations and obtain patrol routes. However, these common indoor positioning technologies on the market, such as UWB positioning technology, often require the deployment of base stations. For special scenarios such as hazardous chemical production, simple installation methods using beacon positioning have emerged on the market, such as Bluetooth beacon positioning. This method only requires beacons to be attached to key areas for positioning. However, in industrial production scenarios, metal interference from large industrial equipment often leads to inaccurate Bluetooth beacon positioning, and positioning accuracy is very low. Summary of the Invention

[0003] In order to overcome the defects of the prior art, the present invention discloses a patrol and positioning device and method based on low-frequency induction.

[0004] The inspection and positioning method based on low-frequency induction of the present invention is used to locate a source to be located using a beacon, and is characterized by comprising the following steps:

[0005] Step 1. Set a standard beacon and normalize the sensitivity of other beacons based on the standard beacon;

[0006] Step 2. Establish the RSSI-distance model f of the standard beacon and the source to be located;

[0007] Specifically:

[0008] Step 2-1. Fix the standard beacon, set the step size and movement range, and move the low-frequency transmitting antenna of the source to be located from the starting point, moving one step at a time until the entire movement range is covered;

[0009] Step 2-2. Calculate the RSSI value each time you move using the following formula:

[0010] p=p0+10n*log(r / r0);

[0011] Where p0 is the RSSI value sensed by the beacon when the distance between the beacon and the source to be located and the standard beacon is r0, n is the path loss index, r is the distance between the standard beacon and the source to be located, and p is the RSSI value sensed when the distance between the standard beacon and the source to be located is r;

[0012] Step 2-3. Fit the point set consisting of all points obtained in step 2-2 to obtain the RSSI-distance model f;

[0013] Step 3. The source to be located continuously transmits a low-frequency signal for communicating with the beacon. When the beacon establishes a high-frequency signal connection with the source to be located, the source to be located is located.

[0014] The positioning method is specifically as follows:

[0015] The measurement value of the beacon received signal strength RSSI is According to the RSSI-distance model f obtained in step 2, the distance measurement between the corresponding beacon and the source to be located is

[0016] Use the following formula:

[0017]

[0018] Traverse all coordinates (x, y) within the beacon sensing range and search for the coordinates (x) corresponding to the point with the maximum probability W(x, y). max ,y max ), which is the location of the source to be located;

[0019] The beacon coordinates are (x i ,y i ), subscript i represents different beacons;

[0020] k is the probability distribution constant under the same scenario,

[0021] log represents the logarithm sign, n is the path loss exponent; exp represents the exponential function with a natural constant as the base, ln represents the natural logarithm, σ is the variance of the normal distribution of the signal measurement error, and m represents the total number of beacons.

[0022] Preferably, step 3 further includes modifying the swing parameters of the low-frequency transmitting antenna of the source to be located; specifically, the following steps:

[0023] Multiple beacons are symmetrically arranged around a low-frequency transmitting antenna, with the beacons and antennas at the same height. The direction perpendicular to the plane where the beacons and antennas are located is defined as the Z axis. The low-frequency transmitting antenna is randomly swung multiple times around the Z axis at an angle α. The positioning method is used to locate the source to be positioned for each swing.

[0024] The density distribution of all positioning points is calculated using two-dimensional kernel density estimation. The coordinates of the point with the largest density are the position point with the maximum probability of antenna swing. The swing parameter correction value (x kde ,y kde );

[0025] After considering the above swing parameter correction in step 3, the final position of the source to be located is

[0026] (x max -x kde ,y max -y kde ).

[0027] Preferably, the step 2 further includes correcting the beacon distance weighting coefficient;

[0028] Specifically, the actual distances between all beacons and the source to be located are set to be the same, all r0, and the corresponding measured RSSIs are p 0_m (m=1,2,3…); the distances obtained by RSSI-distance model are f(p 0_m ), the distance weighting coefficients are r0 / f(p 0_m ); f represents the distance model obtained in step 2;

[0029] For m different beacons, at RSSI value p m When the distance between the beacon and the source to be located is r m , the corresponding final RSSI-distance model is

[0030] r m =r0 / f(p 0_m )*f(p m ).

[0031] Preferably, in step 3, the process of establishing a high-frequency signal connection between the beacon and the source to be located is that the source to be located transmits a signal at a fixed interval. When it approaches a certain beacon, the RSSI value received by the low-frequency receiving antenna of the beacon is greater than the set fixed threshold, then the beacon is awakened and transmits a high-frequency signal after awakening.

[0032] Preferably, the beacon received signal strength RSSI measurement value in step 3 is obtained as follows: the beacon converts the sensed magnetic field strength into a corresponding RSSI value, and then uses the beacon's own high-frequency transmitter to send the RSSI value and the beacon number to the source to be located through the high-frequency transmitting antenna.

[0033] The present invention also discloses a patrol and positioning device based on low-frequency induction, comprising a plurality of beacons, at least one source to be positioned, and a PC terminal; the beacons and the source to be positioned, and the source to be positioned and the PC terminal can communicate with each other;

[0034] Each of the beacons comprises: a beacon microcontroller and a high-frequency transmitting module and a low-frequency receiving module connected thereto, wherein the high-frequency transmitting module and the low-frequency receiving module are respectively connected to a high-frequency transmitting antenna and a low-frequency receiving antenna;

[0035] The source to be located includes a microcontroller of the source to be located and a high-frequency receiving module, a low-frequency transmitting module and a first communication module connected thereto; the high-frequency receiving module and the low-frequency transmitting module are respectively connected to a high-frequency receiving antenna and a low-frequency transmitting antenna, and the microcontroller of the source to be located can control the low-frequency transmitting module to generate a voltage square wave;

[0036] The PC terminal includes a second communication module capable of communicating with the first communication module, and a computer for processing received data.

[0037] Preferably, the low-frequency receiving antenna A31 is a 3D receiving antenna, and the 3D receiving antenna is composed of a capacitor and an inductor connected in parallel.

[0038] Preferably, the low-frequency transmitting antenna is a flat magnetic rod antenna, which is composed of a capacitor and an inductor connected in series.

[0039] Preferably, the first communication module and the second communication module are LORA communication modules

[0040] The beneficial effects of the present invention are:

[0041] 1. The present invention uses a probability distribution function to locate the source to be located, and at the same time reduces the computational cost of multi-beacon positioning through the probability superposition method, increases the flexibility of positioning and also improves the positioning accuracy.

[0042] 2. The positioning method described in the present invention locates the source to be located by establishing an RSSI-distance model of a standard beacon and the source to be located, correcting the beacon distance weighting coefficient, correcting the low-frequency transmitting antenna swing parameters and other technical means, and using a probability distribution function to locate the source to be located, so that all beacons and their models tend to be consistent; by correcting the low-frequency transmitting antenna swing parameters, the positioning error of the antenna swing when the source to be located is worn by the inspection personnel and the positioning error caused by the antenna's own process characteristics are reduced.

[0043] 3. It adopts a combination of low frequency and high frequency, has the characteristics of strong diffraction ability and strong anti-interference ability, can easily pass through objects such as the human body and bricks, and solves the problem of large positioning error when multiple beacons are positioned under strong metal interference. It has little impact on the human body and is very suitable for use in complex scenarios such as industrial production. The equipment has high reliability.

[0044] 4. Beacons can be directly attached to key locations such as walls or equipment, making deployment simple and secure, solving the challenge of placing equipment in industrial production areas. Beacons only operate when awakened by a source to be located, eliminating the need for continuous transmission. This reduces power consumption, increases the operating time of the source to be located, and allows inspectors to wear the beacon for extended periods, reducing maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1This is a schematic structural diagram of a specific embodiment of the beacon of the present invention;

[0046] Figure 2 This is a schematic diagram of a specific implementation of the source to be located and the PC terminal in the present invention.

[0047] Figure 3 This is a diagram of the positioning and installation scenario of various components in a specific embodiment of the present invention.

[0048] Figure 4 The figure is a schematic diagram of a specific flow chart of the positioning method of the present invention.

[0049] Figure 5 1 is an RSSI-distance fitting curve of a standard beacon S and a source to be located in a specific embodiment of the present invention.

[0050] Figure 6 Schematic diagram of an antenna swing mode when correcting low-frequency antenna swing parameters in a specific embodiment of the present invention.

[0051] Figure 7 This is a scene diagram of single interference source positioning in a specific embodiment of the present invention.

[0052] Figure 8 This is a distribution diagram of positioning points of a single interference source in a specific embodiment of the present invention.

[0053] Figure 9 This is a diagram of a dual interference source positioning scenario in a specific embodiment of the present invention.

[0054] Figure 10 This is a distribution diagram of dual interference source positioning points in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0055] The specific embodiments of the present invention are described in further detail below.

[0056] Example 1

[0057] The inspection and positioning device based on low-frequency induction described in this embodiment includes multiple beacons, sources to be positioned, and a PC end. The beacons and the sources to be positioned, and the sources to be positioned and the PC end can communicate with each other.

[0058] Each beacon includes a button battery A1, a high-frequency transmitter module A2, a high-frequency transmitter antenna A21, a low-frequency receiver module A3, a low-frequency receiver antenna A31, and a beacon microcontroller A4. The low-frequency receiver antenna A31 is a 3D receiver antenna capable of receiving low-frequency signals in all directions. It consists of a capacitor and an inductor connected in parallel and normally receives 125 kHz low-frequency signals when resonant. The high-frequency transmitter antenna A21 transmits at a frequency of 433 MHz.

[0059] The beacon microcontroller A4 converts the magnetic field strength sensed by the low-frequency receiver A3 through the low-frequency receiving antenna A31 into the corresponding RSSI value (Received Signal Strength Indicator), and then sends the RSSI value and the beacon ID to the source to be located through the high-frequency transmitter A2 through the high-frequency transmitting antenna A21. Figure 1 shown.

[0060] The source to be located includes a power module B1, a high-frequency receiving module B2, a high-frequency receiving antenna B21, a low-frequency transmitting module B3, a low-frequency transmitting antenna B31, a source-to-be-located microcontroller B4, and a LoRa communication module B5. The source-to-be-located microcontroller B4 controls the low-frequency transmitting module B3 to generate a voltage square wave, which is used to control the resonance of the low-frequency transmitting antenna B31. The low-frequency transmitting antenna B31 is a 125kHz flat magnetic rod antenna composed of a capacitor and an inductor connected in series. When the inductor resonates, it radiates a low-frequency signal within a certain range.

[0061] After the low-frequency signal radiated outward by the low-frequency transmitting module B3 through the low-frequency transmitting antenna B31 is received by the beacon, the high-frequency receiving module B2 receives the RSSI value and beacon ID sent back by all beacons through the high-frequency receiving antenna B21, and then sends the RSSI value and beacon ID to the PC through the LoRa communication module B5 with a frequency of 433MHz. Figure 2 shown.

[0062] The PC terminal includes: LoRa communication module C1 and computer C2. Computer C2 is connected to the 433MHz LoRa communication module C1 via a serial port, receives the positioning information transmitted by the source to be located, including RSSI value and beacon ID, and processes the positioning information through MATLAB to achieve positioning. Figure 2 shown.

[0063] To achieve low power consumption, the source to be located transmits a low-frequency signal at a timed interval, such as 0.2s, and wakes up the beacon when it passes near the beacon. After being woken up, the beacon transmits positioning information to the source to be located, which then sends it to the PC.

[0064] A wake-up mechanism can be set up. When the source to be located is working, it transmits signals at fixed intervals. When it approaches a beacon, the RSSI value received by the beacon's low-frequency receiving antenna is greater than the set fixed threshold, such as the RSSI value corresponding to 2.2m. The beacon is awakened and then transmits a high-frequency signal. Since the beacon's power consumption mainly comes from the high-frequency transmission module, the wake-up mechanism can significantly reduce power consumption.

[0065] The beacon can be pasted and installed on important nodes in the inspection route, including walls and important instruments and equipment, at the same height of about 1-2 meters. After installation, the specific two-dimensional coordinates of the beacon need to be recorded.

[0066] In this embodiment, in order to briefly explain the system installation method and scenario, as shown in the following example: Figure 3 As shown in the figure, this is a top view, using four beacons for positioning. Beacons 1, 2, 3, and 4 are pasted and installed on the walls on both sides of the four corners of a 160cm×160cm square aisle area. The horizontal coordinates are (160,160), (0,160), (0,0), and (160,0), and the height is 160cm. The source to be located is installed on the helmet of the inspector, with the low-frequency transmitting antenna B31 vertically installed at the center point of the helmet. In actual positioning, the coordinates of the low-frequency transmitting antenna B31 are the coordinates of the inspector. In this embodiment, the person wearing the helmet is approximately 165cm tall.

[0067] A specific process of the positioning method based on the above positioning device is as follows: Figure 4 As shown, the following steps are included:

[0068] Step 1. Normalize the beacon's low-frequency receiving antenna. During normalization measurements, the antenna sensitivity of the low-frequency receiving antenna A31 is initially unknown. A Helmholtz coil configuration or any other device capable of generating a uniform magnetic field with a known magnetic flux density is required, with the uniform magnetic field perpendicular to the plane of the tag's antenna coil windings. Measure the RSSI sensitivity of the low-frequency receiving antennas of beacons 1, 2, 3, and 4 in the uniform magnetic field. Define one beacon, such as beacon 1, as the standard beacon S. Normalize the sensitivities of beacons 1, 2, 3, and 4 relative to beacon 1. This step is conventional technology in the field.

[0069] Step 2: Establish the RSSI-distance model of the standard beacon S and the source to be located.

[0070] To establish a 125 kHz low-frequency electromagnetic RSSI-distance model, the low-frequency transmitting antenna B31 was vertically fixed at the center of a 1-meter-high tripod, and the standard beacon S was fixed on a 1-meter-high wall. The driving voltage of the source to be located was 12 V, and the driving current of the low-frequency transmitting antenna B31 was set to 750 mA.

[0071] The low-frequency transmitting antenna B31 was moved gradually farther away, from 5 cm to 220 cm, in 5 cm increments. During each measurement, the PC, through MATLAB software, sent commands from the LoRa communication module C1 to the microcontroller unit of the source to be located to continuously transmit the low-frequency signal three times. The RSSI values ​​obtained from these three measurements were averaged as the RSSI value. The RSSI average was then fitted to the corresponding distance using a specified function. The specified function represents the electromagnetic wave propagation model, as follows:

[0072] p=p0+10n*log(r / r0)

[0073] Where p0 is the RSSI value sensed by the beacon when the distance between the source to be located and the standard beacon is r0, n is the path loss exponent, r is the distance between the standard beacon and the source to be located, and p is the RSSI value sensed by the standard beacon when the distance between the source to be located and the standard beacon is r.

[0074] After fitting, the fitting curve is as follows Figure 5 As shown, where the path loss index n = 11.756, p0 = 187.036, and r0 = 100 cm, the RSSI-distance model of beacon S at 125 kHz is:

[0075] p s =187.036+117.56*log(r s / 100)

[0076] where p s The distance between beacon S and the source to be located is r s The RSSI value sensed at the time,

[0077] Among them 220cm≥r s ≥5cm.

[0078] The RSSI-distance model of the transformed standard beacon S is obtained as follows:

[0079] r s =f(p s )=10e(p S / 117.56+0.4083), 220cm≥r s ≥5cm

[0080] In step 2, the beacon distance weighting coefficient can also be corrected.

[0081] In order to make the RSSI-distance model of each beacon as consistent as possible with the standard beacon model, it is necessary to calibrate the distance weighting coefficient of each beacon. When the actual distance between m beacons and the source to be located is r0, r0 is usually 80cm to 150cm, and the corresponding RSSI is p 0_m(m=1,2,3…); the distances obtained by RSSI-distance model are f(p 0_m ), the distance weighting coefficients are r0 / f(p 0_m ).

[0082] For m different beacons, when the RSSI value is p m When the distance between the beacon and the source to be located is r m , the corresponding final RSSI-distance model is

[0083] r m =r0 / f(p 0_m )*f(p m ).

[0084] In this embodiment, r0 is set to 113.14 cm, and the distance weighting coefficients of beacons 1, 2, 3, and 4 are 1.154, 1.227, 1.014, and 0.929, respectively. That is, their RSSI-distance models are:

[0085] r1=1.154f(p1), r2=1.227f(p2), r3=1.014f(p3), r4=0.929f(p4).

[0086] Step 3:

[0087] The source to be located continuously transmits a low-frequency signal for communicating with the beacon. When the beacon establishes a high-frequency signal connection with the source to be located, the source to be located is located.

[0088] The positioning method of the present invention uses a probability distribution function to locate a source to be positioned.

[0089] The measurement value of received signal strength RSSI is Signal measurement error It follows a normal distribution with mean 0 and variance σ.

[0090] The distance measurement between the beacon and the source to be located is

[0091] Right now

[0092] or

[0093] Taking the derivative of e, we get |dr i / de|=r i *ln10 / 10n, and since e obeys a normal distribution with mean 0 and variance σ, the probability density function of e is:

[0094]

[0095] From the above formula we can get r i The probability density function of :

[0096]

[0097] For the RSSI at a certain location, the beacon coordinates are (x i ,y i ), since the distance beacon is r i The probability on the circumference is W(r i ), corresponding to any point (x, y) on the circumference, its probability is W(r i ) / 2 π r i ,Will Substituting in:

[0098]

[0099] When there are m beacons with known locations, the final probability distribution model is:

[0100]

[0101] in It is a fixed constant in the same scenario.

[0102] That is, in a positioning scenario, it is only necessary to search for the coordinates (x, y) of the point with the largest probability W(x, y) within the beacon sensing range. max ,y max ), which is the location of the source to be located. For greater accuracy, e can be randomly selected multiple times, and the final average coordinate can be calculated and searched. The beacon sensing range is the area that can be sensed by the signal transmitting and receiving devices of all beacons in the positioning scene.

[0103] In this embodiment, there are 4 beacons, and the corresponding coordinates are (x1=160, y1=160), (x2=0, y2=160), (x3=0, y3=0) and (x4=160, y4=0). The signal measurement error is It follows a normal distribution with a mean of 0 and a variance of σ = 1.1.

[0104] That is, the probability distribution model in this scenario is:

[0105]

[0106] Where n = 11.756,

[0107] In order to make the positioning data of the source to be located more accurate at each position, 100 simulations are performed on e to calculate the search positioning coordinates and take the average value as the final coordinate (xe ,y e ), the final coordinates are obtained by multiple calculations (x max ,y max ) is the average value of .

[0108] Before locating the source to be located in step 3, the swing parameters of the low-frequency transmitting antenna of the source to be located may also be corrected.

[0109] The low-frequency transmitting antenna B31 is a flat magnetic rod antenna. Because it is worn on the head or other positions of the inspector and the antenna itself has a vertically flat structural characteristic, it will swing in position and angle to varying degrees as the inspector moves during the actual positioning process. Therefore, the swing parameter correction is required before actual positioning.

[0110] In this embodiment, the low-frequency transmitting antenna B31 is fixed vertically on Figure 3 The center point of the inspection route aisle area (x0=80, y0=80) is equal to the height of the beacon. Figure 6 As shown, the Z axis is randomly swung at an angle α (range 0-60 degrees) 600 times, and the source to be positioned is positioned once for each swing using step 5.

[0111] The density distribution of all positioning points is calculated using the existing two-dimensional kernel density estimation technology. The coordinates of the point with the largest density (79.1789, 79.0837) are the points with the highest probability of antenna swing. Since the antenna setting coordinates are the center point (x0=80, y0=80), the swing correction parameter value x kde =80-79.1789=0.8211,y kde =80-79.0837y0=0.9163.

[0112] When performing actual positioning, the coordinates of the source to be positioned need to be subtracted from the swing correction parameter value, that is, (x max -x kde ,y max -y kde ), which is the maximum probability position point of the source to be located, and (x max ,y max ) Calculate the average multiple times and then perform swing correction parameters.

[0113] Figure 7 In an experiment for this embodiment, the real coordinates of the source to be located are (40, 60). When a single mobile interference source appears in the positioning area (the interference source is an iron metal box that can completely block the beacon signal), the positioning scene diagram of the system is shown. Figure 8 This is a partial distribution diagram of positioning points of a single interference source.

[0114] In this embodiment, 100 positioning operations were performed, and the average positioning error of the system was about 1.4 cm. The generally accepted indoor high-precision positioning error is within 10 cm. This embodiment meets the high-precision requirements.

[0115] Figure 9 In an experiment for this embodiment, the real coordinates of the source to be located are (40, 60). When a single fixed interference source and a single mobile interference source appear in the positioning area at the same time (the interference source is an iron metal box that can completely block the beacon signal), the positioning scene diagram of the system is shown. Figure 10 This is the distribution diagram of some positioning points of dual interference sources.

[0116] In this experiment, 100 positioning operations were performed, and the average positioning error of the system was about 2.4 cm. The generally accepted indoor high-precision positioning error is within 10 cm. This embodiment meets the high-precision requirements.

[0117] The foregoing are the preferred embodiments of the present invention. Unless the preferred implementation modes in each preferred embodiment are obviously self-contradictory or based on a certain preferred implementation mode, each preferred implementation mode can be arbitrarily superimposed and used in combination. The embodiments and the specific parameters in the embodiments are only for the purpose of clearly describing the inventor's invention verification process, and are not intended to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. Any equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A patrol positioning method based on low-frequency induction, which is used to locate the source to be located using beacons, characterized in that , including the following steps: Step 1. Set a standard beacon and normalize the sensitivity of other beacons based on the standard beacon; Step 2. Establish the RSSI-distance model f of the standard beacon and the source to be located; Specifically: Step 2-1. Fix the standard beacon, set the step size and movement range, and move the low-frequency transmitting antenna of the source to be located from the starting point, moving one step at a time until the entire movement range is covered; Step 2-2. Calculate the RSSI value each time you move using the following formula: p=p0+10n*log(r / r0); Where p0 is the RSSI value sensed by the beacon when the distance between the beacon and the source to be located and the standard beacon is r0, n is the path loss index, r is the distance between the standard beacon and the source to be located, and p is the RSSI value sensed when the distance between the standard beacon and the source to be located is r; Step 2-3. Fit the point set consisting of all points obtained in step 2-2 to obtain the RSSI-distance model f; Step 3. The source to be located continuously transmits a low-frequency signal for communicating with the beacon. When the beacon establishes a high-frequency signal connection with the source to be located, the source to be located is located. The positioning method is specifically as follows: The measurement value of the beacon received signal strength RSSI is According to the RSSI-distance model f obtained in step 2, the distance measurement between the corresponding beacon and the source to be located is Use the following formula: in Traverse all coordinates (x, y) within the beacon sensing range and search for the coordinates (x) corresponding to the point with the maximum probability W(x, y). max ,y max ), which is the location of the source to be located; The beacon coordinates are (x i ,y i ), subscript i represents different beacons; k is the probability distribution constant under the same scenario, log represents the logarithm sign, n is the path loss exponent; exp represents the exponential function with a natural constant as the base, ln represents the natural logarithm, and σ is the variance of the normal distribution of the signal measurement error; The step 3 also includes modifying the swing parameters of the low-frequency transmitting antenna of the source to be located; specifically, Multiple beacons are symmetrically arranged around a low-frequency transmitting antenna, with the beacons and antennas at the same height. The direction perpendicular to the plane where the beacons and antennas are located is defined as the Z axis. The low-frequency transmitting antenna is randomly swung multiple times around the Z axis at an angle α. The positioning method is used to locate the source to be positioned for each swing. The density distribution of all positioning points is calculated using two-dimensional kernel density estimation. The coordinates of the point with the largest density are the position point with the maximum probability of antenna swing. The swing parameter correction value (x kde ,y kde ); After considering the above swing parameter correction in step 3, the final position of the source to be located is (x max -x kde ,y max -y kde ).

2. The inspection and positioning method based on low-frequency induction as claimed in claim 1, characterized in that: Said step 2 also includes beacon distance weighting coefficient correction; Specifically, the actual distances between all beacons and the source to be located are set to be the same, all r0, and the corresponding measured RSSIs are p 0_m (m=1,2,3…); the distances obtained by RSSI-distance model are f(p 0_m ), the distance weighting coefficients are r0 / f(p 0_m ); f represents the distance model obtained in step 2; For m different beacons, when the RSSI value is p m When the distance between the beacon and the source to be located is r m , the corresponding final RSSI-distance model is r m =r0 / f(p 0_m )*f(p m )。 3. The inspection and positioning method based on low-frequency induction as claimed in claim 1, characterized in that: In step 3, the process of establishing a high-frequency signal connection between the beacon and the source to be located is that the source to be located transmits signals at fixed intervals. When it approaches a beacon, the RSSI value received by the low-frequency receiving antenna of the beacon is greater than the set fixed threshold, then the beacon is awakened and transmits a high-frequency signal after awakening.

4. The inspection and positioning method based on low-frequency induction as claimed in claim 1, characterized in that: The RSSI value of the beacon received signal strength in step 3 is obtained as follows: the beacon converts the sensed magnetic field strength into a corresponding RSSI value, and then uses the beacon's own high-frequency transmitter to send the RSSI value and the beacon number to the source to be located through the high-frequency transmitting antenna.

5. A patrol and positioning device based on low-frequency induction, characterized in that , including multiple beacons, at least one source to be located and a PC end; the beacons and the source to be located, the source to be located and the PC end can communicate with each other; The inspection and positioning device is used to perform the inspection and positioning method according to claim 1; Each of the beacons comprises: a beacon microcontroller and a high-frequency transmitting module and a low-frequency receiving module connected thereto, wherein the high-frequency transmitting module and the low-frequency receiving module are respectively connected to a high-frequency transmitting antenna and a low-frequency receiving antenna; The source to be located includes a microcontroller of the source to be located and a high-frequency receiving module, a low-frequency transmitting module and a first communication module connected thereto; the high-frequency receiving module and the low-frequency transmitting module are respectively connected to a high-frequency receiving antenna and a low-frequency transmitting antenna, and the microcontroller of the source to be located can control the low-frequency transmitting module to generate a voltage square wave; The PC terminal includes a second communication module capable of communicating with the first communication module, and a computer for processing received data.

6. The inspection and positioning device based on low-frequency induction as claimed in claim 5, characterized in that The low-frequency receiving antenna is a 3D receiving antenna, which is composed of a capacitor and an inductor in parallel.

7. The inspection and positioning device based on low-frequency induction as claimed in claim 5, characterized in that ,The low-frequency transmitting antenna is a flat magnetic rod antenna consisting of a capacitor and an inductor connected in series.

8. The inspection and positioning device based on low-frequency induction as claimed in claim 5, characterized in that , the first communication module and the second communication module are LORA communication modules.

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