CN115932979A - Buried unexploded bomb detection system and method under non-cooperative low-frequency magnetic excitation - Google Patents

Abstract

The invention discloses a detection system and a detection method under buried unexploded bomb non-cooperative low-frequency magnetic excitation, which utilize a low-frequency magnetic sensor array to collect spatial magnetic signals of an area where unexploded bombs possibly exist in the environment of wide-area distributed high-voltage power transmission network magnetic excitation; and carrying out Fourier transform and drying removal treatment on the spatial magnetic signal to obtain a distribution image of the low-frequency magnetic field intensity on a horizontal plane, judging the position of the magnetic anomaly through comparison and analysis of adjacent data of the image, and taking the position with the magnetic anomaly as the position of the buried unexploded bomb. According to the invention, an electromagnetic field is not required to be actively excited, and a 50Hz low-frequency alternating magnetic field generated by a high-voltage power transmission network is directly utilized to carry out remote unmanned autonomous safe and efficient detection on a secondary 50Hz low-frequency alternating magnetic field excited by an underground unexplosive bomb, so that accurate position information of the unexplosive bomb is obtained.

Description

System and method for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation

Technical Field

The present invention belongs to the technical field of underground unexploded bomb detection, and in particular relates to a buried unexploded bomb detection system and method based on wide-area distributed high-voltage transmission network magnetic excitation.

Background Art

Unexploded bombs buried underground include mortar shells, grenades, mines and aerial bombs. They are unexploded bombs left over from battlefields, military exercise ranges or past wars, with unknown exact locations and types. If they are not removed, they will pose a huge threat to people's lives and property. Detection and positioning of unexploded bombs buried underground is an important part of clearing hidden dangers left over from battlefields and ensuring the safety of ranges. There are currently two methods for detecting unexploded bombs buried underground: active and passive. The active detection method requires the detection system to actively emit an excitation signal and detect the secondary induction signal to achieve the purpose of detecting the target, such as transient electromagnetic method. However, the active detection method has a complex system construction, large size and weight, difficult electromagnetic compatibility design, high cost, and high power consumption. Whether it is based on manual detection methods or vehicle-mounted or drone detection methods, the continuous detection time and efficiency are very limited. Common passive detection methods include magnetic detection, etc. Although they are relatively economical and can partially overcome some of the problems brought by active detection methods, they can only detect unexploded bombs buried underground and with magnetism. In addition, their detection capabilities are poor, with high rates of missed alarms and false alarms, low accuracy, and even inability to detect non-magnetic targets. How to efficiently and accurately detect and locate underground unexploded bombs is a technical problem that needs to be solved urgently in the military field.

Summary of the invention

The present invention provides a system and method for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation. It does not require active excitation of the electromagnetic field, but directly utilizes the 50Hz low-frequency alternating magnetic field generated by the high-voltage transmission network to perform remote, unmanned, autonomous, safe and efficient detection of the secondary 50Hz low-frequency alternating magnetic field excited by the underground unexploded bombs, and obtains accurate location information of the unexploded bombs.

According to a first aspect of an embodiment of the present invention, a method for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation is provided, comprising: using a low-frequency magnetic sensor array to collect spatial magnetic signals of areas where unexploded bombs may exist under the magnetic excitation environment of a wide-area distributed high-voltage transmission network; analyzing the variation law of the spatial magnetic field according to the spatial magnetic signals, and taking the position where the magnetic anomaly occurs as the position of the buried unexploded bomb.

In some examples, the spatial magnetic signal is subjected to Fourier transformation and denoising to obtain a distribution image of the low-frequency magnetic field intensity on the horizontal plane, and then the location of the magnetic anomaly is determined by comparing and analyzing adjacent data of the image.

In some examples, the position information of the motion platform equipped with the low-frequency magnetic sensor array is recorded in real time by receiving positioning information from a satellite navigation system, and the position of the buried unexploded bomb is located in combination with the position where the magnetic anomaly appears.

In some examples, an electronic map is used to track and display the motion trajectory of the motion platform in real time and to mark the location of buried unexploded bombs.

In some examples, based on the topography and the spatial distribution of the detected low-frequency magnetic field, areas where unexploded bombs may exist and obstacle avoidance schemes are traversed to plan the detection path in real time.

In some examples, the location of the buried unexploded bomb is transmitted to a remote data terminal, and a control signal for the motion platform is obtained from the remote data terminal.

According to a second aspect of an embodiment of the present invention, there is provided a system for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation, comprising: a low-frequency magnetic sensor array, which collects spatial magnetic signals of areas where unexploded bombs may exist under the magnetic excitation environment of a wide-area distributed high-voltage transmission network; and a suspected target judgment module, which analyzes the variation law of the spatial magnetic field according to the spatial magnetic signals, and takes the position where the magnetic anomaly occurs as the position of the buried unexploded bomb.

In some examples, the suspected target judgment module performs Fourier transform and denoising on the spatial magnetic signal to obtain a distribution image of the low-frequency magnetic field intensity on the horizontal plane, and then determines the location of the magnetic anomaly by comparing and analyzing adjacent data of the image.

In some examples, a suspected target positioning module is also included, which is configured to record the position information of the motion platform carrying the detection system in real time by receiving positioning information from a satellite navigation system, and to locate the position of the buried unexploded bomb in combination with the position where the magnetic anomaly appears.

In some examples, a geographic information module is also included, which is configured to provide an electronic map, track and display the movement trajectory of the motion platform in real time, and mark the location of buried unexploded bombs.

In some examples, a detection path planning module is also included, which is configured to traverse areas where unexploded bombs may exist and obstacle avoidance solutions based on the terrain and the spatial distribution of the detected low-frequency magnetic field, and plan the detection path in real time.

In some examples, a wireless communication module is further included, which is configured to transmit the location of the buried unexploded bomb to a remote data terminal and obtain a control signal for the motion platform from the remote data terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

FIG1 is a schematic diagram showing the principle of generating a detection magnetic field for a buried unexploded bomb under non-cooperative low-frequency magnetic excitation according to an embodiment of the present invention.

FIG2 is a block diagram of a system for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation according to an embodiment of the present invention.

FIG3 is a schematic diagram of the detection principle of buried unexploded bombs under non-cooperative low-frequency magnetic excitation according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a three-axis fluxgate sensor provided by an embodiment of the present invention.

FIG5 is a schematic diagram showing the arrangement of a buried unexploded bomb detection system on an unmanned vehicle according to an embodiment of the present invention.

FIG6 is a schematic diagram of the arrangement of a three-axis fluxgate sensor on an unmanned vehicle according to an embodiment of the present invention.

FIG. 7 is a flow chart of a method for detecting buried unexploded bombs under non-cooperative low-frequency magnetic excitation provided by an embodiment of the present invention.

FIG8 is a flowchart of the detection of buried unexploded bombs under non-cooperative low-frequency magnetic excitation according to an embodiment of the present invention.

9 is a schematic diagram of an autonomous detection path of an unmanned vehicle under non-cooperative low-frequency magnetic excitation of a buried unexploded bomb provided by an embodiment of the present invention.

DETAILED DESCRIPTION

China is a large country in electricity production and consumption. Currently, six regional power grids have been formed, namely the Central China Power Grid, the East China Power Grid, the North China Power Grid, the Southern Power Grid, the Northeast Power Grid and the Northwest Power Grid. In order to change the line voltage of the power generated by the power plant through the transmission lines extending in all directions through step-up/step-down transformers, and to transmit it step by step to the vast areas of power consumption, except for the Northwest Power Grid with 750/330kV as the main grid and 220kV as high-voltage transmission, the other five regional power grids have formed a grid structure with 500kV as the backbone, 220kV as the main trunk, and 110kV or 66kV as high-voltage 50Hz AC transmission. In addition, China has 8 1000kV ultra-high voltage 50Hz AC transmission lines in operation. The voltage level of the 50Hz AC high-voltage transmission network of the Xinjiang Power Grid and the Tibet Power Grid is 220kV, and they are connected to the Northwest Power Grid through DC transmission lines. In these power grids, the 50Hz alternating current of the transmission line generally reaches several thousand amperes.

Figure 1 shows the principle of detecting magnetic field generation under non-cooperative low-frequency magnetic excitation of buried unexploded bombs. As shown in Figure 1, according to the Biot-Saffar and electromagnetic induction laws, the 50Hz alternating current of the wide-area distributed high-voltage transmission line will generate a 50Hz low-frequency alternating magnetic field in space. Because the electromagnetic field has a low frequency, long wavelength, long propagation distance, and strong penetration ability, it can even penetrate the soil and go deep underground. When there is a metal unexploded bomb target where the low-frequency alternating magnetic field reaches, it will produce an electromagnetic induction effect with the underground metal unexploded bomb and excite a secondary 50Hz low-frequency alternating magnetic field in the space near the metal unexploded bomb target. When the low-frequency magnetic induction detector finds the presence of low-frequency magnetic anomalies in the area, it can determine the suspected unexploded bomb target and locate it.

和

，50Hz低频电磁场在地下的趋肤深度或穿透深度为

，且Taking the 50Hz low-frequency alternating magnetic field in space as an example, the mathematical model is used to explain the source of the target magnetic excitation source for the detection of buried unexploded bombs under non-cooperative low-frequency magnetic excitation.

and

, the skin depth or penetration depth of 50Hz low-frequency electromagnetic field in the ground is

,and

It can be seen that the 50Hz high-voltage transmission low-frequency electromagnetic wave has a strong penetrating power to penetrate deep into the soil layer and reach the depth of the buried unexploded bomb, thereby stimulating a 50Hz secondary low-frequency magnetic field carrying the target information of the metal unexploded bomb. When the detector has sufficient sensitivity, it can sense the abnormal value of the 50Hz low-frequency magnetic field at the detection point and find and locate suspicious targets. When the sensitivity of the electromagnetic detector is constant, the greater the electromagnetic field strength of the original signal, the greater the propagation distance when the signal decays to the minimum value that the detector can detect; when the electromagnetic field strength of the original signal is constant, the higher the sensitivity, the larger the detectable range of the detector.

段组成，则在空间任一点

激励的总初级交变磁场为Assume that the distributed high voltage alternating current transmission network consists of

Segments, then at any point in space

The total primary alternating magnetic field excited is

Among them, x , y , z represent the coordinates of the spatial field point, t represents the current time, and

When there is a metal buried underground, according to the law of electromagnetic induction, under the action of a 50Hz alternating electromagnetic field, the changing magnetic field will generate an electric field, and the generated induced electromotive force

为导体表面，

为穿过导体的时变磁场。in,

is the conductor surface,

is the time-varying magnetic field passing through the conductor.

的作用下，导体内部将产生闭合回路涡流，由于导体目标的电阻率很小，涡流常常很强，进而在空间激发次级交变磁场

。当高压输电网有

段时，在空间任一点

激励的总次级交变级磁场为Induced electromotive force

Under the action of the conductor, a closed loop eddy current will be generated inside the conductor. Since the resistivity of the conductor target is very small, the eddy current is often very strong, which in turn excites a secondary alternating magnetic field in space.

When the high voltage transmission grid has

At any point in space

The total secondary alternating magnetic field of the excitation is

in,

总交变磁场可表示为Any point in space

The total alternating magnetic field can be expressed as

+

+

This field is a space-time four-dimensional function, which reflects that when there is a metal buried underground (such as an unexploded bomb) under the excitation of the magnetic field generated by the alternating current of the wide-area distributed transmission network, the spatial magnetic field in the target area will be abnormal at a frequency of 50Hz compared with the spatial background field. By detecting the changes of the magnetic field with space, the existence of the suspected target can be determined and positioned.

Therefore, in order to improve the detection efficiency, probability, positioning accuracy and personnel safety of unexploded bombs buried underground in the target area, the present invention will indirectly utilize the 50Hz electromagnetic field excited in space by the high-voltage transmission network, and based on the low-frequency electromagnetic field generated by the 50Hz current of the non-cooperative high-voltage transmission network to excite the low-frequency induced magnetic field generated by the buried unexploded bomb, the low-frequency induced magnetic field excited by the target is sensed by a multi-component magnetic probe carried by the motion platform. In addition, the network is used to remotely control the platform detection system, so that the system can make autonomous decisions and implement detection. The motion platform in the present invention can be an unmanned vehicle.

FIG2 shows a block diagram of a detection system for buried unexploded bombs under non-cooperative low-frequency magnetic excitation. FIG3 shows a schematic diagram of a detection principle of buried unexploded bombs under non-cooperative low-frequency magnetic excitation. Taking an unmanned vehicle as an example, it includes a vehicle body, an asynchronous motor wheel driving a universal wheel, a drive module and a control module. The unmanned vehicle is equipped with the detection system, and the detection system dynamically senses the magnetic field at the location of the sensor as the unmanned vehicle platform moves. As shown in FIG2 and FIG3, the detection system includes a low-frequency magnetic induction detection module, which includes a low-frequency magnetic sensor array, a low-frequency magnetic induction signal analog-to-digital conversion module and a suspected target judgment module.

、

和

三个方向的磁场。The low-frequency magnetic sensor array includes multiple three-axis fluxgate probes evenly distributed in a straight line. The structure of the three-axis fluxgate probe is shown in Figure 4. Each three-axis fluxgate probe is installed on a non-magnetic material structure. The three measuring axes of the three-axis vector magnetic sensor are in the same direction and fixed on the platform. When the platform is an unmanned vehicle, it is fixed under the platform chassis and performs dynamic detection in motion as the platform moves. It is used to sense and low-noise amplify the vicinity of the probe.

,

and

Magnetic field in three directions.

The low-frequency magnetic induction signal analog-to-digital conversion module is used to collect the low-frequency magnetic signal sensed by each three-axis fluxgate probe to achieve analog-to-digital conversion.

The suspected target judgment module is used to analyze the law of spatial magnetic field changes and judge whether there are suspicious targets. The suspected target judgment module adopts FPGA and multi-core DSP architecture design, performs fast Fourier transform (FFT) and denoising on the spatial magnetic signals collected by multiple three-axis fluxgate probes, obtains the distribution image of low-frequency magnetic field intensity on the horizontal plane, and then judges whether there is magnetic anomaly through comparative analysis of adjacent data, thereby judging the presence and location of suspected targets.

The basic steps for determining and locating suspected targets are:

图像；First, the magnetic field in the detection area is obtained by a magnetic detector.

image;

图像，进行均值滤波，得到平滑后的图像Secondly, assuming that the probe car is at the same height,

Image, perform mean filtering to obtain a smoothed image

表示滤波前的磁场图像，h(m，n)表示滤波器，

表示滤波后的磁场分布图像。Where x and y represent the rows and columns of the magnetic field image, respectively, and m and n represent the rows and columns of the filter.

represents the magnetic field image before filtering, h ( m , n ) represents the filter,

Represents the magnetic field distribution image after filtering.

计算局部方差，以

尺度来遍历

，得到

范围内局部方差为

，由此得到地下埋入可疑目标的位置为

，且Finally, the 50Hz low-frequency magnetic field anomaly image obtained by the above processing

Calculate the local variance,

Scale to traverse

,get

The local variance in the range is

, thus the location of the suspicious target buried underground is

,and

表示目标空间位置的估计值。Where 1 and w represent the length and width of the spatial sampling, respectively.

Represents an estimate of the target's spatial position.

图像上灰度值的异常，判断可疑目标的存在和位置。By detecting and identifying

The abnormal gray value on the image can be used to determine the existence and location of suspicious targets.

The above-mentioned detection system having the low-frequency magnetic sensor array, the low-frequency magnetic signal analog-to-digital conversion module and the suspected target judgment module can be produced and sold separately, that is, the detection system can be deployed as an independent system on existing equipment such as minesweepers.

The detection system may also include a suspected target positioning module. The suspected target positioning module records the position information of the platform in real time by receiving positioning information from the Beidou satellite navigation system, the GPS global positioning system, the Galileo satellite navigation system or the GLONASS satellite navigation system, and locates the suspected buried unexploded bomb target in combination with the position where the 50Hz magnetic anomaly appears.

The detection system may also include a geographic information module, which provides a high-resolution electronic map for real-time tracking and display of the platform's motion trajectory and timely marking of suspicious targets.

The detection system may also include a detection path planning module. The detection path planning module traverses the rough measurement, fine measurement, suspicious target area range and obstacle avoidance scheme according to the topography and the spatial distribution of the detected 50Hz low-frequency magnetic field, and plans the detection path in real time.

The detection system also includes a wireless communication module for realizing remote wireless communication and data information interaction between the platform and the remote data terminal. The present application does not limit the specific technology used for wireless communication. The remote data terminal adopts a mobile phone, a tablet computer, a personal computer, etc. The remote data terminal is loaded with software specially developed for the detection system to realize the control of the entire detection system, and to display and grasp the working status and detection status of each module of the remote platform in real time.

The detection system may also include a detection system integrated control and management module. The detection system integrated control and management module is designed based on FPGA and PLC and is used to coordinate the work of various subsystems such as the coordination platform, low-frequency magnetic induction detection module, information comprehensive processing module, suspected target positioning module, geographic information module, detection path planning module and wireless communication module.

The detection system may also include a power management module. The power management module uses a rechargeable high-energy lithium battery pack. In order to save energy and increase battery life, the battery energy is adjusted and optimally allocated in real time according to the detection and system module task working conditions.

As shown in Figures 5 and 6, the low-frequency magnetic sensor array is fixed on the moving platform and faces the ground. The low-frequency magnetic signal analog-to-digital conversion module, the suspected target judgment module, the suspected target positioning module, the geographic information module, the detection path autonomous planning module and the detection system comprehensive control and management module are installed in a box on the platform. The box is designed with non-magnetic material structural parts such as carbon fiber or plastic, and has a radio frequency magnetic interference shielding effect.

Figure 7 shows a flow chart of a detection method for buried unexploded bombs under non-cooperative low-frequency magnetic excitation. As shown in Figure 7, the detection method includes: step 10, fast Fourier transform the sampled data to obtain the magnetic field value of 50Hz frequency; step 11, based on the magnetic detection data of the entire area, obtain the magnetic field distribution image of the detection area; step 12, mean filter the magnetic field image to obtain a smooth image; step 13, calculate the local variance of the processed 50Hz magnetic field anomaly image; step 14, detect and judge the presence of suspicious targets based on the local variance of the magnetic field image; locate and mark the target in combination with satellite positioning and electronic maps. For more detailed implementation methods of each step, refer to the above-mentioned detection system part.

Figure 8 shows a flow chart of the detection of buried unexploded bombs under non-cooperative low-frequency magnetic excitation. The following describes the detection process of buried unexploded bombs using the detection system and method of the present invention in conjunction with Figure 8.

Step 20, input the area where the unexploded bombs may exist into the high-resolution electronic map, and set the detection parameters.

Step 21, placing the unmanned automatic vehicle detection system at a safe distance outside the set suspected unexploded bomb area.

Step 21, the remote data terminal moves away from the suspected unexploded bomb area.

Step 22, the remote data terminal uploads the preliminary planned unmanned automatic vehicle detection path to the detection system integrated control management module.

Step 23, under the control of the remote data terminal, the unmanned automatic vehicle detection system can perform a "bow"-shaped reciprocating autonomous detection of the detection area as shown in FIG9, and transmit the detection process back to the remote data terminal in real time; the ground data processing terminal receives and stores the data in real time; once a suspicious target is found, the unmanned automatic vehicle detection system will mark the geographical location information of the suspected suspicious target on a high-resolution electronic map through rough measurement, fine measurement and other processes, and quickly transmit the detection results back to the remote data terminal in the form of danger warning;

Step 24, after the detection is completed, the detection system is recovered.

Claims (10)

1. A detection method under buried unexploded bomb non-cooperative low-frequency magnetic excitation is characterized by comprising the following steps:

collecting a spatial low-frequency magnetic signal of a region where unexploded bombs possibly exist in the environment of wide-area distributed high-voltage transmission network magnetic excitation by using a low-frequency magnetic sensor array;

and according to the space low-frequency magnetic signal, analyzing the change rule of the space magnetic field, and taking the position with magnetic anomaly as the position of the buried unexploded bomb.

2. The detection method according to claim 1, wherein the spatial low-frequency magnetic signal is subjected to fourier transform and drying processing to obtain a distribution image of the low-frequency magnetic field intensity on a horizontal plane, and the position of the magnetic anomaly is determined by comparing and analyzing adjacent data of the image.

3. The detection method according to claim 2, wherein the position information of the motion platform carrying the low-frequency magnetic sensor array is recorded in real time by receiving satellite navigation system positioning information, and the position of the buried unexploded bomb is positioned by combining the position of the occurrence of the magnetic anomaly.

4. The detection method according to claim 3, characterized in that an electronic map is used for carrying out real-time tracking display on the motion track of the motion platform and marking the position of the buried unexploded bomb; traversing the possible existing area of the unexploded bomb and the obstacle avoidance scheme according to the landform and the detected space distribution condition of the low-frequency magnetic field, and planning the detection path in real time.

5. A detection method according to any one of claims 1 to 4, characterised in that the location where a buried unexploded bomb will be located is transmitted to a remote data terminal and control signals for the motion platform are obtained from the remote data terminal.

6. A buried unexploded bomb non-cooperative low frequency magnetic excitation lower detection system, comprising:

the low-frequency magnetic sensor array is used for collecting a spatial low-frequency magnetic signal of a region where unexploded bombs possibly exist in the environment of wide-area distributed high-voltage power transmission network magnetic excitation; and

and the suspected target judgment module analyzes the change rule of the space magnetic field according to the space low-frequency magnetic signal and takes the position with magnetic anomaly as the position of the buried unexploded bomb.

7. The detection system according to claim 6, wherein the suspected target determination module performs Fourier transform and drying processing on the spatial low-frequency magnetic signal to obtain a distribution image of the low-frequency magnetic field intensity on a horizontal plane, and determines the position of the magnetic anomaly by comparing and analyzing adjacent data of the image.

8. The detection system of claim 7, further comprising a suspected target positioning module configured to record position information of a moving platform carrying the detection system in real time by receiving satellite navigation system positioning information, and to position the position of a buried unexploded bomb in combination with the position of the occurrence of the magnetic anomaly.

9. The detection system of claim 8, further comprising: the geographic information module is configured to provide an electronic map, track and display the motion track of the motion platform in real time and mark the position of the buried unexploded bomb; and the detection path planning module is configured to traverse the possible existing area of the unexplosive bomb and the obstacle avoidance scheme according to the landform and the spatial distribution condition of the detected low-frequency magnetic field, and plan the detection path in real time.

10. The detection system of any one of claims 6 to 9, further comprising a wireless communication module configured to transmit the location of a buried unexploded bomb to a remote data terminal and to obtain a control signal for the motion platform from the remote data terminal.

Images