Airborne transient electromagnetic detection device and method for complex mountainous area detection

Abstract

The present invention relates to the technical field of geophysical exploration equipment, and in particular to an airborne transient electromagnetic detection device and method for complex mountain area detection. The device comprises an isosceles right-angled triangular prism frame, wherein the rectangular surface of the isosceles right-angled triangular prism frame with the largest area is arranged downward, a rectangular transmitting coil I is arranged on the rectangular surface on one side of the isosceles right-angled triangular prism frame, and a rectangular transmitting coil II is arranged on the rectangular surface on the other side, a circular receiving coil I is arranged at the midpoint of the lower edge of the transmitting coil I and in a direction parallel to the transmitting coil I, a circular receiving coil II is arranged at the midpoint of the lower edge of the transmitting coil II and in a direction parallel to the transmitting coil II, and a circular receiving coil III is arranged at the exact center of the rectangular surface with the largest area and in a direction parallel to the rectangular surface with the largest area. The present invention adopts a plurality of detection modes, and achieves the purpose of detecting different terrains through different combinations of transmitting and receiving coils.

Description

Technical Field

[0001] The present invention relates to the technical field of geophysical exploration equipment, and in particular to an airborne transient electromagnetic detection device and method for detecting complex mountainous areas. Background Art

[0002] Airborne transient electromagnetic detection is a time-domain artificial source electromagnetic detection method and one of the metal mine detection methods commonly used internationally in recent years. This method has the advantages of fast speed, high efficiency, large exploration depth, and high resolution. It is particularly suitable for shallow coverage areas with high working difficulties. The airborne transient electromagnetic detection system sends pulse current to the ground through a multi-turn transmitting coil suspended under the aircraft to generate a primary field. The primary field acts on the underground anomaly to generate a secondary field. The secondary field is received by the receiving coil and the received data is inverted to obtain underground geological information.

[0003] CN202093187.U discloses a pod-type time-domain helicopter airborne electromagnetic detection system, including a pod and an electromagnetic survey device. The pod includes a regular dodecagonal tube structure outer ring, a central column, an internal support frame, a central offset coil tray, a pod fastening rope, and a tail. The pod part of the system adopts a glass fiber reinforced plastic round tube structure, which is not only simple in structure, light in weight, and strong in structural strength; and the various components widely adopt a nested structure, which is easy to disassemble and maintain; the transmitting part of the system adopts a large current fast shutdown technology and the receiving part adopts a segmented processing method of electromagnetic signals, which improves the depth, resolution and sensitivity of the survey.

[0004] CN108535667.A discloses an aviation magnetic field compensation multi-coil system based on a double compensation coil, including: a transmitting coil; a receiving coil; and a double compensation coil, including a positive compensation coil and a negative compensation coil, arranged between the transmitting coil and the receiving coil; wherein the transmitting coil, the double compensation coil, and the receiving coil are coplanar and co-centered, and the receiving coil is on the inner side; the parameters of the double compensation coil are set so that the primary field signal received by the receiving coil is zero. The radius and number of turns of the double compensation coil in the system can be flexibly adjusted and changed according to actual application requirements, and are no longer severely restricted by the parameters of the transmitting coil, effectively reducing the geometric size and weight of the compensation coil; it can not only effectively reduce the dynamic range of the receiver, but also greatly improve the shallow detection capability and detection accuracy of the aviation transient electromagnetic system, and is conducive to improving the quality and effect of aviation transient electromagnetic detection data, as well as the flexibility and practicality of system design.

[0005] CN112130214.A discloses an aviation transient electromagnetic eccentric double compensation coil system, including: a transmitting coil, a receiving coil and an eccentric double compensation coil group, the eccentric double compensation coil group includes an eccentric positive compensation coil and an eccentric reverse compensation coil; the eccentric positive compensation coil and the eccentric reverse compensation coil are arranged between the transmitting coil and the receiving coil, and deviate from the center of the transmitting coil; the eccentric double compensation coil group is coplanar and co-centered with the receiving coil, and is located inside the transmitting coil. The system can reduce the geometric size and weight of the compensation coil, improve the compensation effect of the compensation coil, make the compensation coil parameter design no longer overly dependent on the transmitting coil parameters, and be more flexible and practical, and improve the shallow detection capability and electromagnetic data quality of the aviation transient electromagnetic system.

[0006] Most of the existing research is designed for horizontal coils, which can achieve better results in areas with relatively flat terrain. However, when the detection target is a high mountain, the disadvantages of the flat coil are low energy efficiency and limited propagation distance when it is detected. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides an airborne transient electromagnetic detection device and method for complex mountain detection, and proposes a non-horizontal transmitting coil that is at a certain angle to the ground. In order to take into account both ground detection and mountain detection, a dual transmitting coil and three receiving coils are used for grouping.

[0008] The present invention is implemented as follows: first, an airborne transient electromagnetic detection device for detecting complex mountainous areas is provided, comprising an isosceles right-angled triangular prism frame, wherein the rectangular surface of the isosceles right-angled triangular prism frame with the largest area is arranged downward, a rectangular transmitting coil I is arranged on the rectangular surface on one side of the isosceles right-angled triangular prism frame, and a rectangular transmitting coil II is arranged on the rectangular surface on the other side, wherein the transmitting coil I and the transmitting coil II form a transmitting coil group, a circular receiving coil I is arranged at the midpoint of the lower edge of the transmitting coil I and in a direction parallel to the transmitting coil I, a circular receiving coil II is arranged at the midpoint of the lower edge of the transmitting coil II and in a direction parallel to the transmitting coil II, a circular receiving coil III is arranged at the exact center of the rectangular surface with the largest area and in a direction parallel to the rectangular surface with the largest area, wherein the receiving coils I, II and III form a receiving coil group.

[0009] Preferably, the rectangular transmitting coil I has the same side shape and size as the corresponding isosceles right triangular prism frame; the rectangular transmitting coil II has the same side shape and size as the corresponding isosceles right triangular prism frame.

[0010] More preferably, it further includes a transmitter and a receiver, the transmitter is connected to the transmitting coil I and the transmitting coil II respectively through a cable, and the receiver is connected to the receiving coil I, the receiving coil II and the receiving coil III respectively through a cable.

[0011] Further preferably, the side length and number of turns of the transmitting coil I and the transmitting coil II are variable; the radius and number of turns of the receiving coil I, the receiving coil II and the receiving coil III are variable.

[0012] The present invention also provides a method for detecting complex mountainous areas using the above-mentioned aviation transient electromagnetic detection device for detecting complex mountainous areas. When performing underground detection, the transmitting coil I and the transmitting coil II are used as transmitting coils, and the receiving coil III is used as a receiving coil.

[0013] The present invention also provides a method for detecting complex mountainous areas using the above-mentioned aviation transient electromagnetic detection device for detecting complex mountainous areas. When detecting the mountain, the transmitting coil I and the transmitting coil II are used as transmitting coils, and the receiving coil I and the receiving coil II are used as receiving coils.

[0014] The present invention verifies the method of performing complex mountain detection using the above-mentioned aviation transient electromagnetic detection device, which includes the following steps:

[0015] Assume that the transmitting coil TX is a rectangle and the receiving coil RX is a circle. The centers of the transmitting coil TX and the receiving coil RX are the origins of the spatial rectangular coordinate system. The side length of TX is 2a×2b, and the radius of RX is r2. After RX rotates α, β, and γ around the XYZ coordinate system, the X'Y'Z' coordinate system is obtained. The rotation angle ranges from 0 to 360°. According to the Neumann integral formula, the mutual inductance coefficient between the transmitting coil l1 and the receiving coil l2 can be written as:

[0016]

[0017] Where dl1 and dl2 are the integral line elements of the two closed coils l1 and l2, respectively, R is the distance between the two integral line elements, μ0 is the magnetic permeability of the vacuum medium, and the coordinates x2, y2, z2 of dl2 can be written as:

[0018]

[0019] Where L is the lateral offset, i.e. the Y-axis direction, H is the longitudinal offset, i.e. the Z-axis direction, φ2 is the angle between the integral line element dl2 and the Y-axis, and the integral elements dx2, dy2, and dz2 can be written as:

[0020]

[0021] Rotation matrix:

[0022]

[0023] Substituting formula (2)-(4) into formula (1), the mutual inductance coefficient M can be obtained;

[0024] Assume that the side length of the transmitting coil TX is 5m, the diameter of the receiving coil RX is 0.5m, the angle between the two transmitting coils is 90°, and the horizontal and vertical offsets are performed with the center of a certain transmitting coil as the origin. The offset range is 0-5m. Through calculation, when the mutual inductance coefficient is 0, it is the optimal position of the receiving coil.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] 1. The present invention adopts multiple modes of detection, and achieves the purpose of detecting different terrains through different combinations of transmitting and receiving coils;

[0027] 2. The present invention obtains the optimal position of the receiving coil by calculating the mutual inductance, thereby reducing the influence of the primary field on the secondary field;

[0028] 3. The radius and number of turns of the transmitting coil combination receiving coil group of the present invention can be adjusted according to actual requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0030] Figure 1 The figure is a schematic structural diagram of an airborne transient electromagnetic detection device for detecting complex mountainous areas according to an embodiment of the present invention.

[0031] Figure 2 It is a schematic diagram of the emission timing of the present invention.

[0032] Figure 3 It is a schematic diagram of the coil excitation current when the transmitting coil of the present invention is focused underground.

[0033] Figure 4 It is a schematic diagram of the coil excitation current when the transmitting coil of the present invention is focused toward the mountain.

[0034] Figure 5 This is the receiving coil placement method used by the present invention when detecting underground.

[0035] Figure 6 This is the receiving coil placement method used by the present invention when detecting a mountain. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] refer to Figure 1 The present invention provides an airborne transient electromagnetic detection device for detecting complex mountainous areas, comprising an isosceles right-angled triangular prism frame 6, wherein the rectangular surface of the isosceles right-angled triangular prism frame 6 with the largest area is arranged downward, a rectangular transmitting coil I1 is arranged on the rectangular surface on one side of the isosceles right-angled triangular prism frame 6, and a rectangular transmitting coil II2 is arranged on the rectangular surface on the other side, the transmitting coil I1 and the transmitting coil II2 form a transmitting coil group, a circular receiving coil I3 is arranged at the midpoint of the lower edge of the transmitting coil I1 and in a direction parallel to the transmitting coil I1, a circular receiving coil II4 is arranged at the midpoint of the lower edge of the transmitting coil II2 and in a direction parallel to the transmitting coil II2, a circular receiving coil III5 is arranged at the exact center of the rectangular surface with the largest area and in a direction parallel to the rectangular surface with the largest area, the receiving coils I3, II4 and III5 form a receiving coil group.

[0038] The rectangular transmitting coil I1 has the same side shape and size as the corresponding isosceles right-angled triangular prism frame 6; the rectangular transmitting coil II2 has the same side shape and size as the corresponding isosceles right-angled triangular prism frame 6.

[0039] The present invention also includes a transmitter and a receiver. The transmitter is connected to the transmitting coil I1 and the transmitting coil II2 respectively through cables, and the receiver is connected to the receiving coil I3, the receiving coil II4 and the receiving coil III5 respectively through cables.

[0040] In order to increase universality, the side length and the number of coil turns of the transmitting coil I1 and the transmitting coil II2 are variable; the radius and the number of turns of the receiving coil I3, the receiving coil II4, and the receiving coil III5 are variable.

[0041] The detection method of the present invention has the following characteristics:

[0042] 1) Excitation energy focusing method based on cross-combination transceiver coil device:

[0043] By properly designing the emission control timing (such as Figure 2 ) changes the direction of the excitation current of the two coils. When the current directions of the two coils are the same, the emission magnetic field after vector superposition focuses toward the mountain, such as Figure 3 As shown; when the current direction is opposite, the emitted magnetic field after vector superposition is focused toward the ground, as shown Figure 4 shown.

[0044] 2) Optimal design of coil position based on weak magnetic coupling structure:

[0045] The present invention realizes a weak magnetic coupling structure by adjusting the relative positions of the transmitting coil and the receiving coil based on the analysis of the magnetic field distribution of the orthogonal transmitting coil, thereby providing a guarantee for the precise detection of the mountain.

[0046] Taking the rectangular transmitting coil and circular receiving coil as examples, the mutual inductance calculation formula is derived:

[0047] Assume that the transmitting coil TX is a rectangle and the receiving coil RX is a circle. The centers of the transmitting coil TX and the receiving coil RX are the origins of the spatial rectangular coordinate system. The side length of TX is 2a×2b, and the radius of RX is r2. After RX rotates α, β, and γ around the XYZ coordinate system, the X'Y'Z' coordinate system is obtained. The rotation angle ranges from 0 to 360°. According to the Neumann integral formula, the mutual inductance coefficient between the transmitting coil l1 and the receiving coil l2 can be written as:

[0048]

[0049] Where dl1 and dl2 are the integral line elements of the two closed coils l1 and l2, respectively, R is the distance between the two integral line elements, μ0 is the magnetic permeability of the vacuum medium, and the coordinates x2, y2, z2 of dl2 can be written as:

[0050]

[0051] Where L is the lateral offset, i.e. the Y-axis direction, H is the longitudinal offset, i.e. the Z-axis direction, φ2 is the angle between the integral line element dl2 and the Y-axis, and the integral elements dx2, dy2, and dz2 can be written as:

[0052]

[0053] Rotation matrix:

[0054]

[0055] Substituting formula (2)-(4) into formula (1), the mutual inductance coefficient M can be obtained;

[0056] Assume that the side length of the transmitting coil TX is 5m, the diameter of the receiving coil RX is 0.5m, the angle between the two transmitting coils is 90°, and the horizontal and vertical offsets are performed with the center of a certain transmitting coil as the origin. The offset range is 0-5m. Through calculation, when the mutual inductance coefficient is 0, it is the optimal position of the receiving coil.

[0057] In order to achieve time-sharing measurement of mountain and underground anomalies, two sets of transmitting coils are set up. For underground detection, a single receiving coil is used to collect information, and it is parallel to the ground, such as Figure 5As shown by the dotted coil; for mountain detection, two receiving coils are used to collect information, and they are parallel to the transmitting coil, such as Figure 6 Shown by the dotted circle.

[0058] In summary, the present invention provides an airborne transient electromagnetic detection device and detection method for complex mountainous area detection, which can not only detect geological bodies under different terrain conditions in a time-sharing manner, but also adjust the radius and number of turns of the coil as needed to further improve the flexibility and practicality of the system design, which has important scientific significance and engineering value for improving the technical level and exploration capability of the airborne transient electromagnetic system.

[0059] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. The airborne transient electromagnetic detection device for complex mountainous areas is characterized by: The invention comprises an isosceles right-angled triangular prism frame (6), wherein the rectangular surface with the largest area of ​​the isosceles right-angled triangular prism frame (6) is arranged downward, a rectangular transmitting coil I (1) is arranged on the rectangular surface on one side of the isosceles right-angled triangular prism frame (6), and a rectangular transmitting coil II (2) is arranged on the rectangular surface on the other side, the transmitting coil I (1) and the transmitting coil II (2) form a transmitting coil group, a circular receiving coil I (3) is arranged at the midpoint of the lower edge of the transmitting coil I (1) and in a direction parallel to the transmitting coil I (1), a circular receiving coil II (4) is arranged at the midpoint of the lower edge of the transmitting coil II (2) and in a direction parallel to the transmitting coil II (2), a circular receiving coil III (5) is arranged at the exact center of the rectangular surface with the largest area and in a direction parallel to the rectangular surface with the largest area, and the receiving coil I (3), the receiving coil II (4) and the receiving coil III (5) form a receiving coil group.

2. The airborne transient electromagnetic detection device for complex mountainous area detection according to claim 1 is characterized in that: The rectangular transmitting coil I (1) has the same side shape and size as the corresponding isosceles right-angled triangular prism frame (6); the rectangular transmitting coil II (2) has the same side shape and size as the corresponding isosceles right-angled triangular prism frame (6).

3. The airborne transient electromagnetic detection device for complex mountainous area detection according to claim 1 is characterized in that: The invention also includes a transmitter and a receiver. The transmitter is connected to the transmitting coil I (1) and the transmitting coil II (2) respectively through cables. The receiver is connected to the receiving coil I (3), the receiving coil II (4) and the receiving coil III (5) respectively through cables.

4. The airborne transient electromagnetic detection device for complex mountainous area detection according to claim 1 is characterized in that: The side length and number of turns of the transmitting coil I (1) and the transmitting coil II (2) are variable; the radius and number of turns of the receiving coil I (3), the receiving coil II (4) and the receiving coil III (5) are variable.

5. A method for detecting complex mountainous areas using the airborne transient electromagnetic detection device for detecting complex mountainous areas according to claim 1, characterized in that: When performing underground detection, the transmitting coil I (1) and the transmitting coil II (2) are used as transmitting coils, and the receiving coil III (5) is used as a receiving coil.

6. A method for detecting complex mountainous areas using the airborne transient electromagnetic detection device for detecting complex mountainous areas according to claim 1, characterized in that: When performing mountain detection, the transmitting coil I (1) and the transmitting coil II (2) are used as transmitting coils, and the receiving coil I (3) and the receiving coil II (4) are used as receiving coils.

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