Miniaturized Compensation Device and Design Method for Time-Domain Airborne Electromagnetic Soft Pod Rigid Structure

Abstract

This application belongs to the field of airborne electromagnetic exploration technology, specifically relating to a miniaturized compensation device and design method for a time-domain airborne electromagnetic soft pod with a rigid structure. The device includes a compensation-receiving coil and a transmitting coil, which are co-centered. The compensation-receiving coil comprises a compensation coil and a receiving coil wound on the same annular frame. One terminal of the compensation coil is connected to a first point on the transmitting coil via a series impedance device, and the other terminal of the compensation coil is directly connected to a second point on the transmitting coil via a lead wire. The area between the first and second points is a section of the transmitting coil. This application can reduce the weight of exploration equipment and decrease early noise generated during primary field movement.

Description

Technical Field

[0001] This application belongs to the field of airborne electromagnetic exploration technology, specifically relating to a miniaturized compensation device and design method for a time-domain airborne electromagnetic soft pod with a hard structure. Background Technology

[0002] An airborne electromagnetic survey system consists of a transmitting coil, a compensation coil, and a receiving coil. During operation, the transmitting coil generates an induced field, and the receiving coil receives the induced signal returned by the compensation coil. The compensation coil prevents saturation of the dB / dt field signal of the highly sensitive receiving coil under strong magnetic fields. The compensation coil requires a current of the same magnitude but opposite direction to that of the transmitting coil. Due to its application in the aerospace field, the first challenge is weight reduction; the second is that the traditional flexible connection between the compensation and receiving coils can lead to early noise from the primary field during movement under high sensitivity conditions.

[0003] The placement of compensation coils in typical domestic and international systems is described below. The SkyTEM system's compensation coil is typically located in the corner area of ​​the transmitting coil, making it sensitive to vibration and attitude changes, and easily introducing additional motion noise. The AeroTEM IV system uses eccentric compensation, resulting in significant dynamic noise. The VTEM system uses concentric compensation, and its flexible connections easily lead to high early-stage noise. The domestically developed CHTEM-III-32 system uses concentric compensation, which presents challenges in terms of size and weight. Summary of the Invention

[0004] This application provides a miniaturized compensation device and design method for a time-domain airborne electromagnetic soft pod hard structure, which solves the problems of large size and weight, as well as high early noise in existing compensation structures.

[0005] According to an embodiment of the first aspect of this application, a miniaturized compensation device for the rigid structure of a time-domain airborne electromagnetic soft pod is provided. The device includes a compensation-receiving coil and a transmitting coil, wherein the compensation-receiving coil and the transmitting coil are co-centered, and the compensation-receiving coil includes a compensation coil and a receiving coil wound on the same annular frame. One terminal of the compensation coil is connected to a first point on the transmitting coil through a series impedance device, and the other terminal of the compensation coil is directly connected to a second point on the transmitting coil through a lead wire. The area between the first point and the second point is a cut-off section of the transmitting coil.

[0006] Furthermore, the frame includes a coaxial compensation coil ring and a receiving coil ring, forming a compensation coil groove in the middle, and receiving coil grooves on both sides of the compensation coil groove, with two receiving coil grooves on each side. The diameter of the compensation coil groove is larger than the diameter of the receiving coil groove. The compensation coil is wound inside the compensation coil groove, and the receiving coil is wound inside the receiving coil groove.

[0007] Furthermore, the impedance device includes a magnetic ring with coils of different numbers of turns wound on it, and the number of turns of the coils is adjusted according to the required inductance.

[0008] Furthermore, the transmitting coil is a regular polygonal structure composed of multiple circular tubes, and the positions of the transmitting coil and the compensation-receiving coil are fixed, and they are connected to the helicopter by ropes.

[0009] Furthermore, the formula for calculating the number of turns of the coil on the magnetic ring is: , , , Represents the permeability of free space. Where is the relative permeability of the magnetic ring material, and N represents the number of turns of the coil wound on the magnetic ring. This represents the inductance of the inductor connected in series with the compensation coil. This is the effective cross-sectional area of ​​the magnetic ring. The height of the magnetic ring is indicated by OD, and the outer and inner diameters of the magnetic ring are indicated by ID, respectively. This indicates the effective magnetic path length of the magnetic ring.

[0010] Furthermore, the resistance of the compensation coil satisfies: ,in The current in the transmitting coil, To compensate for the current in the coil, To compensate for the coil resistance, The resistance of the segment cut off from the transmitting coil;

[0011] The inductance of the compensation coil satisfies: , To compensate for the time constant of the coil, To compensate for the inductance of the coil, The time constant of the transmitting coil, The inductance of the transmitting coil, The resistance of the transmitting coil;

[0012] The length of the wire wound on the compensating coil is: , To compensate for the radius of the coil, The radius of the transmitting coil;

[0013] The current in the compensation coil and the number of turns in the compensation coil satisfy the following: , This represents the current in the transmitting coil. This indicates the current in the compensation coil. Indicates the number of turns of the compensation coil. This represents the mutual inductance between the transmitting and receiving coils. This indicates the mutual inductance between the compensation coil and the receiving coil.

[0014] A design method for a miniaturized compensation device for a time-domain airborne electromagnetic soft pod hard structure according to a second aspect embodiment of this application, the design method comprising:

[0015] Determine the physical and electrical parameters of the transmitting coil, wherein the physical parameters include the radius of the transmitting coil, and the electrical parameters include the current, time constant, resistance, and inductance of the transmitting coil;

[0016] Calculate the voltage, resistance, and inductance of the cut-off segment of the transmitting coil based on its length.

[0017] Calculate the resistance of the compensation coil: ,in The current in the transmitting coil, To compensate for the current in the coil, To compensate for the coil resistance, The resistance of the segment cut off from the transmitting coil;

[0018] Calculate the inductance of the compensation coil: , To compensate for the time constant of the coil, To compensate for the inductance of the coil, The time constant of the transmitting coil, The inductance of the transmitting coil, The resistance of the transmitting coil;

[0019] The length of the wire wound around the compensating coil is calculated as follows: , To compensate for the radius of the coil, The radius of the transmitting coil;

[0020] Calculate the cross-sectional area of ​​the winding of the compensating coil based on the length of the winding: , It is the cross-sectional area of ​​the wire wound around the compensating coil. It is the resistivity of copper;

[0021] Based on the relationship between the number of turns of the compensation coil and the weight of the compensation coil:

[0022] Adjust the required number of turns, where, Indicates the weight of the copper wire. This indicates the weight per square millimeter of one meter of copper wire. This represents the current in the transmitting coil. This indicates the current in the compensation coil. Indicates the number of turns of the compensation coil. This represents the mutual inductance between the transmitting and receiving coils. This indicates the mutual inductance between the compensation coil and the receiving coil.

[0023] Compared with the prior art, the advantages of this application are: it can reduce the weight of exploration equipment and reduce the early noise caused by the movement of the primary field. Attached Figure Description

[0024] Figure 1 A schematic diagram of a miniaturized compensation device for a time-domain airborne electromagnetic soft pod with a rigid structure, provided in an embodiment of this application;

[0025] Figure 2 A diagram showing the positional relationship between the transmitting coil and the compensation-receiving coil provided in an embodiment of this application;

[0026] Figure 3 A schematic diagram of the skeleton provided in the embodiments of this application;

[0027] Figure 4 This is a schematic diagram of the impedance device provided in the embodiments of this application;

[0028] Figure 5 The transmitting current waveform and compensation current waveform diagram provided in the embodiments of this application;

[0029] Figure 6 This is a schematic diagram of the connection structure of the transmitting coil, the compensation coil, and the impedance device provided in the embodiments of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] This application is referred to Figure 1As shown, a miniaturized compensation device for the rigid structure of a time-domain airborne electromagnetic soft pod includes: a compensation-receiving coil 1, an impedance device 2, a transmitting coil section 3, a transmitting coil 4, a transmitting cable 5, a transmitter 6, and a receiver 7. The transmitter 6 is part of the transmitting system and is connected to the large transmitting coil 4 via the transmitting cable 5. The receiving system consists of the receiver 7 and the compensation-receiving coil 1 embedded in the center of the transmitting coil 4. The compensation-receiving coil 1 includes a compensation coil and a receiving coil wound on the same annular frame. One terminal of the compensation coil is connected to a first point on the transmitting coil 4 via the series impedance device 2, and the other terminal of the compensation coil is directly connected to a second point on the transmitting coil 4 via a lead. The transmitting coil section 3 is located between the first and second points. The impedance device 2 ensures a sufficiently large and adjustable inductance with very low resistance. During system operation, the transmitting coil 4 generates an excitation magnetic field, the compensation-receiving coil 1 senses the target signal, and transmits the signal through the lead of the impedance device 2. The impedance device 2 provides adjustable inductance and is adjacent to the transmitting coil section 3, forming an optimized electromagnetic coupling structure. The entire system achieves electromagnetic detection and signal analysis of underground targets through the coordinated operation of transmitting coil 4 and compensation-receiving coil 1.

[0032] In one embodiment, see Figure 3 As shown, the frame includes coaxial compensating coil rings and receiving coil rings, forming a central compensating coil groove 10 and receiving coil grooves 9 on both sides of the compensating coil groove 10, with two receiving coil grooves 9 on each side. The diameter of the compensating coil groove 10 is larger than the diameter of the receiving coil groove 9. The compensating coil is wound inside the compensating coil groove 10, and the receiving coil is wound inside the receiving coil groove 9. The diameter of the compensating coil groove 10 is 1.026 times the diameter of the receiving coil groove 9. The compensating coil is wound inside the compensating coil groove 10 and reliably fixed through holes. The receiving coil is wound inside the receiving coil groove 9 and positioned and fixed using holes, allowing for smooth continuous winding of the receiving coil among the four receiving coil grooves 9.

[0033] In one embodiment, the impedance device 2 includes a magnetic ring on which coils of varying numbers of turns are wound to form an adjustable inductance. The formula for calculating the number of turns of the coils on the magnetic ring is: , , , Represents the permeability of free space. Where is the relative permeability of the magnetic ring material, and N represents the number of turns of the coil wound on the magnetic ring. This represents the inductance of the inductor connected in series with the compensation coil. This represents the effective cross-sectional area of ​​the magnetic ring, i.e., the equivalent cross-sectional area through which the magnetic field lines pass. The height of the magnetic ring is indicated by OD, and the outer and inner diameters of the magnetic ring are indicated by ID, respectively. This indicates the effective magnetic path length of the magnetic ring.

[0034] In one embodiment, see Figure 2 As shown, the transmitting coil 4 is a regular polygonal structure composed of multiple circular tubes, forming an approximately circular coil structure. The positions of the transmitting coil and the compensation-receiving coil 1 are fixed, and they are connected to the helicopter via rope 8. The positions of the transmitting coil 4 and the compensation-receiving coil 1 are fixed. Winding the compensation coil and the receiving coil onto the same frame reduces the weight of the exploration equipment and decreases early noise generated during primary field movement.

[0035] In one embodiment, see Figure 6 As shown, a combination structure of a double-bolt nut 11 with a washer and a semi-circular clamp 14 forms two symmetrical connection points on the sleeve 12 of the transmitting coil, namely the first point and the second point. The lead 13 of the compensation coil is first welded to the sleeve of the transmitting coil, and then mechanically and electrically fixed by the semi-circular clamp 13 and the double-bolt nut 11 with a washer. An impedance device 2 is connected in series on the lead of the compensation coil. The impedance device 2 uses a self-wound coil magnetic ring, which can adjust the inductance while ensuring a small resistance, so as to ensure that the ratio of the inductance to the resistance of the compensation coil meets the requirements.

[0036] See Figure 5 As shown, the current waveform of the transmitting coil and the current waveform that the compensation coil needs to generate are shown. If you want to compensate for the current of the transmitting coil, you must ensure that the rise, peak and fall times of the two current waveforms are consistent.

[0037] During the flat-top phase of the current waveform, the voltage is low. To ensure the synchronization of the current in the transmitting coil 4 and the compensation coil, a resistor shunt method can be used to ensure that the currents are in phase. The current in segment 3 of the transmitting coil is shunt to the compensation coil, so that the compensation coil generates a reverse magnetic field to cancel the magnetic field generated by the transmitting coil, making the primary field induced by the receiving coil as close to zero as possible.

[0038] The formula for the induced electromotive force in the circuit is shown in (1). The magnetic induction intensity B consists of two parts: one part is the magnetic induction intensity of the transmitting coil 4, and the other part is the magnetic induction intensity of the compensation coil. The formula for the magnitude of the induced electromotive force generated by the transmitting coil 4 in the receiving coil is shown in (2). The formula for the magnitude of the induced electromotive force generated by the compensation coil in the receiving coil is shown in (3). Combining formulas (1), (2), and (3), formula (4) can be derived. This represents the mutual inductance between the transmitting and receiving coils. This represents the mutual inductance between the compensation coil and the receiving coil. Given the current in the transmitting coil, the relationship between the current in the compensation coil and the number of turns in the compensation coil can be derived:

[0039] (1);

[0040] (2);

[0041] (3);

[0042] (4);

[0043] in, This represents the induced electromotive force, and S represents the area of ​​the compensation coil. This represents the current in the transmitting coil. This indicates the current in the compensation coil. Indicates the number of turns of the compensation coil. This represents the induced electromotive force generated by the transmitting coil in the receiving coil. This represents the induced electromotive force generated by the compensation coil in the receiving coil.

[0044] Given the inductance of the inductor required to be connected in series with the compensation coil, the number of coil turns required for the magnetic ring to be wound is calculated according to formula (5), where This represents the free permeability, with a value of 4. *10 -7 H / m, ρ represents the relative permeability of the magnetic ring material, a dimensionless value. N represents the number of turns of the coil wound on the magnetic ring. This indicates the inductance of the inductor connected in series with the compensation coil. The effective cross-sectional area of ​​the magnetic ring is the equivalent cross-sectional area through which the magnetic lines of force pass, calculated by formula (6). The height of the magnetic ring is indicated by OD, and the outer and inner diameters of the magnetic ring are indicated by ID, respectively. The effective magnetic circuit length of the magnetic ring is the average length of the closed path of the magnetic field lines inside the magnetic ring, which is calculated by formula (7):

[0045] (5);

[0046] (6);

[0047] (7);

[0048] The relationship between the number of turns of the compensation coil and the current of the compensation coil can be determined by formula (4). Determining the lengths of the two connection points determines the voltage, resistance, and inductance of the transmitting coil section 3. The resistance shunt formula is shown in formula (8). Given the current of the transmitting coil, the current of the compensation coil, and the resistance of the transmitting coil section 3, the resistance of the compensation coil can be calculated:

[0049] (8).

[0050] To ensure that the current in the compensation coil can compensate for the current in the transmitting coil, the time constants of the compensation coil and the transmitting coil must be consistent, as shown in formula (9). Given the resistance and inductance of the transmitting coil and the resistance of the compensation coil, the inductance of the compensation coil can be calculated:

[0051] (9);

[0052] The voltage value generated by the inductance of the compensation coil can be calculated using formula (10). The length D of the wire wound around the compensation coil can be obtained using formula (11) given the radius of the compensation coil and the radius of the receiving coil.

[0053] (10)

[0054] (11);

[0055] According to formula (12), the cross-sectional area of ​​the wire wound on the compensating coil can be calculated, and then the wire diameter and total weight of the winding can be calculated:

[0056] (12) It is the cross-sectional area of ​​the wire wound around the compensating coil. It is the resistivity of copper. It is the resistance of the compensation coil.

[0057] According to formula (13), the relationship between the number of turns of the compensating coil and the weight of the copper wire can be calculated, and it is non-linear. Indicates the weight of the copper wire. This indicates the weight per square millimeter of a one-meter-long copper wire.

[0058] (13)

[0059] In other words, the weight reduction of the compensation coil can be achieved by adjusting the number of turns of the compensation coil.

[0060] On the other hand, embodiments of this application provide a design method for a miniaturized compensation device for a time-domain airborne electromagnetic soft pod hard structure, the method comprising:

[0061] The physical and electrical parameters of the transmitting coil 4 are determined. The physical parameters include the radius of the transmitting coil 4, and the electrical parameters include the current, time constant, resistance, and inductance of the transmitting coil 4.

[0062] Calculate the voltage, resistance, and inductance of the cut-off segment 3 of the transmitting coil based on the length of the cut-off segment 3.

[0063] Calculate the resistance of the compensation coil:

[0064] ,in The current in the transmitting coil, To compensate for the current in the coil, To compensate for the coil resistance, The resistance of the segment cut off from the transmitting coil;

[0065] Calculate the inductance of the compensation coil:

[0066] , To compensate for the time constant of the coil, To compensate for the inductance of the coil, The time constant of the transmitting coil, The inductance of the transmitting coil, The resistance of the transmitting coil;

[0067] The length of the wire wound around the compensating coil is calculated as follows:

[0068] , To compensate for the radius of the coil, The radius of the transmitting coil;

[0069] Calculate the cross-sectional area of ​​the winding of the compensating coil based on the length of the winding:

[0070] , It is the cross-sectional area of ​​the wire wound around the compensating coil. It is the resistivity of copper;

[0071] Based on the relationship between the number of turns of the compensation coil and the weight of the compensation coil:

[0072] Adjust the required number of turns, where, Indicates the weight of the copper wire. This indicates the weight per square millimeter of one meter of copper wire. This represents the current in the transmitting coil. This indicates the current in the compensation coil. Indicates the number of turns of the compensation coil. This represents the mutual inductance between the transmitting and receiving coils. This indicates the mutual inductance between the compensation coil and the receiving coil.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A time domain airborne electromagnetic soft pod hard structure miniaturization compensation device, characterized in that, The device comprises a compensation-receiving coil (1) and a transmitting coil (4), the compensation-receiving coil (1) is concentric with the transmitting coil (4), the compensation-receiving coil (1) comprises a compensation coil and a receiving coil wound on the same annular framework, one terminal of the compensation coil is connected with a first point on the transmitting coil (4) through a series impedance device (2), the other terminal of the compensation coil is directly connected with a second point on the transmitting coil (4) through a lead, and the transmitting coil segment (3) is between the first point and the second point.

2. The time domain airborne electromagnetic soft-buoy hard-structure miniaturization compensation device according to claim 1, characterized in that, The framework comprises coaxial compensation coil rings and receiving coil rings, a compensation coil groove (10) is formed in the middle, and receiving coil grooves (9) are arranged on both sides of the compensation coil groove (10), two receiving coil grooves (9) are arranged on each side, the diameter of the compensation coil groove (10) is larger than that of the receiving coil groove (9), the compensation coil is wound in the compensation coil groove (10), and the receiving coil is wound in the receiving coil groove (9).

3. The hard structure miniaturization compensation device for time domain airborne electromagnetic soft pod according to claim 1, characterized in that, The impedance device (2) comprises a magnetic ring, and coils with different numbers of turns are wound on the magnetic ring, and the number of turns of the coil is adjusted according to the required inductance.

4. The hard structure miniaturization compensation device for time domain airborne electromagnetic soft pod according to claim 1, characterized in that, The transmitting coil (4) is a regular polygon structure composed of multiple circular tubes, the transmitting coil (4) and the compensation-receiving coil (1) are fixed in position and connected with the helicopter through a rope (8).

5. The hard structure miniaturization compensation device for time domain airborne electromagnetic soft pod according to claim 2, characterized in that, The formula for calculating the number of turns of the coil on the magnetic ring is: , , , represents the vacuum permeability, is the relative permeability of the magnetic ring material, N represents the number of turns of the coil wound on the magnetic ring, represents the inductance of the inductance in series with the compensation coil, is the effective cross-sectional area of the magnetic ring, represents the height of the magnetic ring, OD and ID represent the outer diameter and inner diameter of the magnetic ring respectively, represents the effective magnetic path length of the magnetic ring.

6. The hard structure miniaturization compensation device for a soft bird of time domain airborne electromagnetic system according to claim 1, characterized in that, The resistance of the compensation coil satisfies: wherein is the current of the transmitting coil, is the current of the compensation coil, is the resistance of the compensation coil, is the resistance of the intercepting section of the transmitting coil; The inductance of the compensation coil satisfies: , is the time constant of the compensation coil, is the inductance of the compensation coil, is the time constant of the transmitting coil, is the inductance of the transmitting coil, is the resistance of the transmitting coil; The length of the wire wound by the compensation coil is: , is the radius of the compensation coil, is the radius of the transmitting coil; The current of the compensation coil and the number of turns of the compensation coil satisfy: , denotes the current of the transmitting coil, denotes the current of the compensation coil, denotes the number of turns of the compensation coil, denotes the mutual inductance value between the transmitting coil and the receiving coil, denotes the mutual inductance value between the compensation coil and the receiving coil.

7. A design method of the time domain airborne electromagnetic soft pod hard structure miniaturization compensation device according to any one of claims 1-6, characterized in that, The design method comprises: determining the physical parameters and electrical parameters of the transmitting coil (4), the physical parameters comprising the radius of the transmitting coil (4), and the electrical parameters comprising the current, time constant, resistance and inductance of the transmitting coil (4); the voltage, resistance and inductance of the transmitting coil segment (3) are calculated through the length of the transmitting coil segment (3); The resistance of the compensation coil is calculated as: wherein is the current of the transmitting coil, is the current of the compensation coil, is the resistance of the compensation coil, is the resistance of the intercepting section of the transmitting coil; calculating the inductance of the compensation coil: , the time constant of the compensation coil, the inductance of the compensation coil, the time constant of the transmitting coil, the inductance of the transmitting coil, the resistance of the transmitting coil; The length of the wire wound by the compensation coil is calculated as: , is the radius of the compensation coil, is the radius of the transmitting coil; The cross-sectional area of the wire wound by the compensation coil is calculated according to the length of the wire wound by the compensation coil: , is the cross-sectional area of the wire wound by the compensation coil, is the resistivity of copper; According to the relationship between the number of turns of the compensation coil and the weight of the compensation coil: Adjust the number of turns required, wherein, represents the weight of copper wire, represents the weight of one meter long copper wire per square millimeter, represents the current of the transmitting coil, represents the current of the compensation coil, represents the number of turns of the compensation coil, represents the mutual inductance value between the transmitting coil and the receiving coil, represents the mutual inductance value between the compensation coil and the receiving coil.

Images