A detection and positioning device and method based on motion magnetic induction

Abstract

A detection and positioning device based on motion magnetic induction includes a magnet, a receiving coil group and a signal processing device; the magnet and the receiving coil group are arranged on a motion platform, and the magnet and the receiving coil group are configured to be relatively static; the magnet is used as a constant magnetic field source, and induction excites the metal target to generate an echo magnetic field signal in the relative motion with the metal target, the receiving coil group receives the echo magnetic field signal, and the signal processing device detects the metal target according to the information obtained by the receiving coil group. The present invention also provides a corresponding detection and positioning method. The present invention uses a magnet to generate a constant magnetic field, and will not directly generate an induction signal on the vector magnetic sensor, and isolates the transmission and reception signals from a physical mechanism. In addition, the present invention uses a three-dimensional vector receiving coil group, which uses all the information of the three orthogonal vectors of the echo magnetic field, and has the functions of ranging and angle measurement and positioning. At the same time, the main hardware of the present invention is only a magnet and a receiving coil group, and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal detection and positioning, and in particular relates to a detection and positioning device and method based on motion magnetic induction. Background Art

[0002] By using the strong penetration of magnetic fields on non-metallic media, hidden metal targets can be detected. For example, using handheld magnetic induction metal detection devices at airports and station security checkpoints can detect hidden metal objects and detect metal objects buried underground.

[0003] However, currently common magnetic field detection equipment, such as the metal detection devices disclosed in patents with application numbers 201810096364.2 and 201520594606.2, all use AC energized coils as magnetic field sources. Since the magnetic field transmission and receiving signals are in the same frequency band, the strong transmission magnetic field will interfere with the extremely weak echo magnetic field signal, which is not conducive to long-distance detection and positioning. The present invention uses a permanent magnet as a magnetic field source, which will not generate an induced voltage in the receiving coil, and isolates the transmission signal and the receiving signal from a physical mechanism.

[0004] In addition, the patent with application number 202010251790.6 discloses an underwater metal detector based on CVD diamond quantum sensing and its preparation method, which also uses a permanent magnet as a source, but the method disclosed in the invention does not have the function of isolating the transceiver channels. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a detection and positioning device and method based on motion magnetic induction, in order to solve at least one of the following problems:

[0006] (1) The existing metal detection device has poor isolation between the transmitting and receiving channels, which leads to a short detection distance.

[0007] (2) Existing metal detection devices cannot fully utilize the three-dimensional holographic information of the magnetic field echo vector for positioning.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A detection and positioning device based on motion magnetic induction, comprising a magnet, a receiving coil group and a signal processing device; the magnet and the receiving coil group are arranged on a motion platform, and the magnet and the receiving coil group are configured to be relatively static; the magnet is used as a constant magnetic field source, and induction excites the metal target to generate an echo magnetic field signal during relative motion with the metal target, the receiving coil group receives the echo magnetic field signal, and the signal processing device realizes detection of the metal target according to the information obtained by the receiving coil group.

[0010] In one embodiment, the receiving coil group is a vector magnetic sensor group, and the magnet is a rare earth permanent magnet or an electromagnet.

[0011] In one embodiment, the vector magnetic sensor group is a three-dimensional vector coil group or a three-dimensional Hall effect magnetic sensor.

[0012] In one embodiment, the vector magnetic sensor group includes three orthogonal vector sensors: sensor x, sensor y and sensor z, which are respectively used to receive three orthogonal components B of the echo magnetic field signal. x , B y , B z , convert the echo magnetic field signal into three voltage signals V x 、V y and V z , the signal processing device according to V x 、V y and V z Realize the detection and positioning of metal targets.

[0013] In one embodiment, the sensor x is coil x, the sensor y is coil y, the sensor z is coil z, the number of turns of coil x, coil y and coil z are all N, the cross-sectional area is all S, and the normal of the plane is parallel to the x-axis, y-axis and z-axis of the spatial rectangular coordinate system respectively, and the three voltage signals V x 、V y and V z Satisfies the following relationship:

[0014] V x =-jωNSB x

[0015] V y =-jωNSB y

[0016] V z =-jωNSB z

[0017] Where ω is the angular frequency of the echo magnetic field signal, V x 、V y and V z They are transmitted to the signal processing device through differential line x, differential line y and differential line z respectively.

[0018] In one embodiment, the speed of the motion platform is greater than 10 m / s.

[0019] In one embodiment, the magnet is connected to the receiving coil assembly via a rigid device to ensure that the magnet and the receiving coil assembly do not move relative to each other; the signal processing device is connected to the receiving coil assembly via a signal bus to receive its signal.

[0020] The present invention also provides a detection and positioning method based on motion magnetic induction, comprising the following steps:

[0021] Step 1: The magnet and the receiving coil group follow the motion platform and move relative to the metal target. With the metal target as the reference system, the magnet generates a time-varying magnetic field, which induces and excites the surface of the metal target to generate an echo magnetic field signal.

[0022] Step 2, the receiving coil group receives the echo magnetic field signal, and the receiving coil group and the magnet always remain relatively still;

[0023] Step 3: The signal processing device detects and locates the metal target according to the information obtained by the receiving coil group.

[0024] In one embodiment, the receiving coil group is a three-dimensional vector coil group, comprising three orthogonal vector sensors: sensor x, sensor y and sensor z, which are respectively used to receive three orthogonal components B of the echo magnetic field signal. x , B y , B z , convert the echo magnetic field signal into three voltage signals V x 、V y and V z The signal processing device establishes (V x ,V y ,V z )and The corresponding relationship between them can realize the distance and angle measurement of the metal target, that is, detection and positioning; where r is the relative distance between the metal target and the motion platform, θ is the elevation angle of the metal target relative to the motion platform, is the azimuth angle of the metal target relative to the moving platform.

[0025] In one embodiment, the establishment (V x ,V y ,V z )and The corresponding relationship between them is as follows:

[0026]

[0027]

[0028]

[0029] f r It is a function of the magnetic field strength of the echo magnetic field signal.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] Compared with common metal detection devices, the present invention does not use an AC energized coil as a magnetic field source to generate an alternating magnetic field, but uses a magnet as a magnetic field source to generate a constant magnetic field. The constant magnetic field will not directly generate an induction signal on the vector magnetic sensor group, and the transmission signal and the reception signal are isolated from a physical mechanism. In addition, the present invention uses a three-dimensional vector receiving coil group to make full use of all the information of the three orthogonal vectors of the echo magnetic field, and has the positioning function of ranging and angle measurement. At the same time, the main hardware of the present invention is only a magnet and a vector magnetic sensor group, and its structure is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure and principle of the present invention.

[0033] Figure 2 It is a schematic diagram of the structure and connection method of the three-dimensional vector coil group of the present invention.

[0034] Figure 3 3 is a schematic diagram of a corresponding curve of the magnetic field intensity and the distance r of the echo magnetic field signal received by the vector magnetic sensor group of the present invention.

[0035] Figure 4 It is a schematic diagram of the distribution of the vector direction of the echo magnetic field signal in space of the present invention.

[0036] Figure 5 It is a flowchart of the detection method of the present invention. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0038] As mentioned above, conventional metal detection devices usually use AC energized coils as magnetic field sources, and the transmitted and received signals are in the same frequency band. The strong transmitted magnetic field will interfere with the extremely weak echo magnetic field signal, which is not conducive to long-distance detection and positioning. On the other hand, existing metal detection devices cannot fully utilize the three-dimensional holographic information of the magnetic field echo vector, resulting in the lack of positioning methods.

[0039] Based on this, the present invention uses a magnet as a constant magnetic field source, which will not generate an induced voltage in the receiving coil, and isolates the transmitting signal and the receiving signal from a physical mechanism, which can have better receiving sensitivity and a larger working distance. At the same time, the present invention uses a three-dimensional vector receiving coil, which can locate the metal target to be detected according to the direction of the magnetic field vector, and provides corresponding distance measurement and angle measurement methods.

[0040] Specifically, refer to Figure 1The present invention is a detection and positioning device based on motion magnetic induction, which is arranged inside a high-speed motion platform 1. It mainly includes a magnet 2, a receiving coil group 3 and a signal processing device 4. The connection relationship between them is: the magnet 2 and the receiving coil group 3 are arranged on the same motion platform 1, move with the motion platform 1, and the magnet 2 and the receiving coil group 3 always remain relatively still.

[0041] A feasible specific connection structure, the magnet 2 and the receiving coil group 3 are connected by a rigid device 5 to ensure that the magnet 2 and the receiving coil group 3 do not move relative to each other; the rigid device 5 can be a non-magnetic material such as copper, aluminum, insulating rubber, etc., and its shape is arbitrary, depending on the shape of the magnet 2 and the receiving coil group 3. The magnet 2 and the receiving coil group 3 can also be directly connected by an adhesive. The signal processing device 4 is connected to the receiving coil group 3 through a signal bus 6 to receive its signal, and the signal processing device 4 and the signal bus 6 can also be mounted on the same motion platform 1. However, when wireless conditions are feasible, wireless connection can also be used.

[0042] Its main working principle is:

[0043] The magnet 2 acts as a constant magnetic field source. When the moving platform 1 passes near the metal target 8, the magnet 2 and the metal target 8 move relative to each other. With the metal target 8 as the reference system, the magnet 2 generates a time-varying magnetic field 7, which induces an eddy current 9 on the surface of the metal target 8. Further, the eddy current 9 excites an echo magnetic field signal 10. The echo magnetic field signal 10 is received by the receiving coil group 3, and the signal processing device 4 can complete the detection of the metal target 8 according to the signal characteristics.

[0044] During the detection process, the magnet 2 is used as a constant magnetic field source. Since there is no relative movement between the magnet 2 and the receiving coil group 3, the magnetic field 7 generated by the magnet 2 will not directly generate an induced signal on the receiving coil group 3. The transmitting signal and the receiving signal are isolated from a physical mechanism, the isolation of the transmitting and receiving channels is achieved, and distance detection is performed based on a quasi-static field.

[0045] In the embodiment of the present invention, in order to ensure that the time-varying characteristics of the magnetic field 7 are obvious, the speed of the motion platform 1 is generally preferably greater than 10 m / s. The motion platform 1 can be a high-speed train, a drone, or even a cannonball.

[0046] In the embodiment of the present invention, the magnet 2 can be a rare earth permanent magnet or an electromagnet. The advantage of the electromagnet is that the magnetic field can be adjusted as needed, but it consumes power, and the residual magnetism of the magnet 2 is generally not less than 1 Tesla.

[0047] In an embodiment of the present invention, the receiving coil group 3 is a vector magnetic sensor group to obtain vector information, and the signal processing device 4 can further realize detection and positioning based on the information. For example, the vector magnetic sensor group can select a three-dimensional vector coil group or a three-dimensional Hall effect magnetic sensor. The advantage of using a three-dimensional Hall effect magnetic sensor is that the device size can be reduced.

[0048] refer to Figure 2 The vector magnetic sensor group selected by the present invention includes three orthogonal vector sensors: sensor x3-1, sensor y3-2 and sensor z3-3. The magnetic field strength of the echo magnetic field signal 10 at the vector magnetic sensor group is Decompose it into three orthogonal components of the coordinate system, namely B x , B y , B z Sensor x3-1, sensor y3-2 and sensor z3-3 are used to receive B x , B y , B z , converting the echo magnetic field signal 10 into three voltage signals V x 、V y and V z The signal processing device 4 is based on V x 、V y and V z The metal target 8 can be detected and located.

[0049] When the vector magnetic sensor group selects a three-dimensional vector coil group, sensor x3-1 is coil x, sensor y3-2 is coil y, and sensor z3-3 is coil z. The number of turns of coil x, coil y, and coil z are all N, and the cross-sectional area is S. The normals of the planes of the three coils are parallel to the x-axis, y-axis, and z-axis of the spatial rectangular coordinate system, respectively.

[0050] Assume that the magnetic field component B x There is no effective magnetic flux on coil y and coil z, it will only be received by coil x, generating an induced voltage V x , satisfying the following relationship:

[0051] V x =-jωNSB x (1)

[0052] Similarly, the magnetic field component B y and magnetic field component B z The induced voltage V will be generated in coil y and coil z respectively. y and V z :

[0053] V y =-jωNSB y (2)

[0054] V z =-jωNSB z (3)

[0055] Where ω is the angular frequency of the echo magnetic field signal 10, V x 、V y and V z The signals are transmitted to the signal processing device 4 through the differential line x6-1, the differential line y6-2 and the differential line z6-3 respectively. Figure 2 shown.

[0056] According to the above structure and principle, the device of the present invention can detect and locate the metal target 8 by receiving the three-way voltage V x 、V y and V z By analyzing and processing, the relative position information of the motion platform 1 and the metal target 8 can be obtained. Specifically, according to the three-dimensional magnetic field vector B x , B y , B z The spatial distribution characteristics of the three-way voltage signal (V x ,V y ,V z )and The corresponding relationship between them can realize the distance and angle measurement of the metal target 8. That is, the relative distance r between the metal target 8 and the motion platform 1, the elevation angle θ of the metal target 8 relative to the motion platform 1 and the azimuth angle of the metal target 8 relative to the motion platform 1 can be expressed as three voltage signals V x 、V y and V z Function: r = f r (V x ,V y ,V z ),θ=f θ (V x ,V y ,V z ), where f r (·),f θ (·)and Each represents a function.

[0057] More specifically:

[0058] Distance measurement: The distance measurement function can be realized by the strength of the voltage signal. The closer the distance between the motion platform 1 and the metal target 8 is, the stronger the induced eddy current 9 is, and the greater the strength of the echo magnetic field signal 10 is, the stronger the induced voltage signal V generated on the receiving coil group 3 is. x 、Vy and V z Assuming that the distance between the moving platform 1 and the metal target 8 is r, it can be expressed as a function of the received magnetic field strength, and thus also as a function of the induced voltage amplitude:

[0059]

[0060] like Figure 3 As shown, the corresponding relationship between the distance r and the strength of the magnetic field signal received by the receiving coil group 3 is shown. The simulation conditions used in the figure are: the speed of the motion platform 1 is 100m / s, the magnet 2 is a cubic neodymium magnet with a side length of 3cm (remanent magnetism 1.4T), and the metal target 8 is set as a square steel plate with a side length of 1m and a thickness of 10cm. The receiving coil group 3 converts the received magnetic field signal into an electrical signal, and the signal processing device 4 makes a judgment to estimate the distance r.

[0061] Angle measurement: by processing the three voltage signals V received by the signal processing device 4 x 、V y and V z By analyzing the ratio between the two, we can get the elevation angle θ and azimuth angle of the moving platform 1 relative to the metal target 8. Make an estimate. Figure 4 As shown in the figure, not only the strength of the echo magnetic field signal 10 generated by the metal target 8 corresponds to the distance r, but also the vector direction of the echo magnetic field is related to the spatial orientation (elevation angle θ and azimuth angle θ) of the metal target 8. The induced eddy current 9 of the metal target 8 is approximately annularly distributed. Under this approximation, the elevation angle θ and azimuth angle of the metal target 8 relative to the moving platform 1 can be calculated. As shown below:

[0062]

[0063]

[0064] The theoretical approximate formula is given above. In the specific implementation, it can also be modified according to electromagnetic simulation software or experimental measurement to obtain a more accurate function correspondence for a specific model. In summary, the flow chart of the detection method in this embodiment is as follows: Figure 5 shown.

[0065] The present invention can be carried on a moving platform to detect and locate metal targets. For example, it can be carried on a high-speed railway to detect rail anomalies, or carried on a drone to detect and locate underground mineral deposits.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A detection and positioning device based on motion magnetic induction, characterized in that: The invention comprises a magnet (2), a receiving coil group (3) and a signal processing device (4), wherein the receiving coil group (3) is a vector magnetic sensor group, and the magnet (2) is a rare earth permanent magnet or an electromagnet; the magnet (2) and the receiving coil group (3) are arranged on a moving platform (1), and the magnet (2) and the receiving coil group (3) are configured to be relatively stationary; the magnet (2) is used as a constant magnetic field source, and in the relative motion with the metal target (8), the magnet (2) induces and excites the metal target (8) to generate an echo magnetic field signal (10), the receiving coil group (3) receives the echo magnetic field signal (10), and the signal processing device (4) detects the metal target (8) according to the information obtained by the receiving coil group (3); The vector magnetic sensor group comprises three orthogonal vector sensors: sensor x (3-1), sensor y (3-2) and sensor z (3-3), which are respectively used to receive three orthogonal components B of the echo magnetic field signal (10) x , B y , B z , convert the echo magnetic field signal (10) into three voltage signals V x 、V y and V z The signal processing device (4) is based on V x 、V y and V z Realize the detection and positioning of metal targets (8); The sensor x (3-1) is coil x, the sensor y (3-2) is coil y, and the sensor z (3-3) is coil z. The number of turns of coil x, coil y, and coil z are all N, and the cross-sectional area is all S. The normal of the plane is parallel to the x-axis, y-axis, and z-axis of the spatial rectangular coordinate system, respectively. The three voltage signals V x 、V y and V z Satisfies the following relationship: In x =-jωNSB x In y =-jωNSB y In z =-jωNSB z Where ω is the angular frequency of the echo magnetic field signal (10), V x 、V y and V z The signals are transmitted to the signal processing device (4) through the differential line x (6-1), the differential line y (6-2) and the differential line z (6-3) respectively.

2. The detection and positioning device based on motion magnetic induction according to claim 1, characterized in that: The vector magnetic sensor group is a three-dimensional vector coil group or a three-dimensional Hall effect magnetic sensor.

3. The detection and positioning device based on motion magnetic induction according to claim 1, characterized in that: The speed of the motion platform (1) is greater than 10 m / s.

4. The detection and positioning device based on motion magnetic induction according to claim 1, characterized in that: The magnet (2) and the receiving coil group (3) are connected via a rigid device (5) to ensure that the magnet (2) and the receiving coil group (3) do not move relative to each other; the signal processing device (4) is connected to the receiving coil group (3) via a signal bus (6) to receive its signal.

5. A detection and positioning method based on motion magnetic induction, implemented by using the detection and positioning device based on motion magnetic induction according to claim 1, comprising the following steps: Step 1, the magnet (2) and the receiving coil group (3) follow the moving platform (1) and the metal target (8) to move relative to each other, with the metal target (8) as the reference system, the magnet (2) generates a time-varying magnetic field (7), and the magnetic field (7) induces and excites the surface of the metal target (8) to generate an echo magnetic field signal (10); Step 2, the receiving coil group (3) receives the echo magnetic field signal (10), and the receiving coil group (3) and the magnet (2) always remain relatively still; Step 3: The signal processing device (4) detects the metal target (8) based on the information obtained by the receiving coil group (3).

6. The detection and positioning method based on motion magnetic induction according to claim 5 is characterized in that: The receiving coil group (3) is a three-dimensional vector coil group, comprising three orthogonal vector sensors: sensor x, sensor y and sensor z, which are respectively used to receive three orthogonal components B of the echo magnetic field signal (10). x , B y , B z , convert the echo magnetic field signal (10) into three voltage signals V x 、V y and V z The signal processing device (4) establishes (V x ,V y ,V z )and The corresponding relationship between them is used to achieve distance measurement and angle measurement of the metal target (8), that is, detection and positioning; wherein r is the relative distance between the metal target (8) and the motion platform (1), θ is the elevation angle of the metal target (8) relative to the motion platform (1), is the azimuth angle of the metal target (8) relative to the moving platform (1).

7. The detection and positioning method based on motion magnetic induction according to claim 6 is characterized in that: The establishment of x ,V y ,V z )and The corresponding relationship between them is as follows: f r is a function of the magnetic field strength of the echo magnetic field signal (10).

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