A multi-mode tow-pull type transient electromagnetic detection device and working method

Abstract

The application belongs to the field of geophysical geological exploration equipment, and relates to a multi-mode towed-pushed transient electromagnetic detection device and a working method thereof. The device comprises eight receiving coils and a transmitting coil. The transmitting coil is rectangular, and three receiving coils are arranged on one long side of the transmitting coil at equal intervals. Each long side is equally divided into four parts by the centers of the three receiving coils. One receiving coil is arranged at the midpoint of the short side of the transmitting coil. All the receiving coils are on the same plane and parallel to the plane where the transmitting coil is located. The distance between the receiving coils and the transmitting coil is h, and the offset distance between the center of each receiving coil and the side of the transmitting coil is s. The complementary synergistic effect is formed by the combination of the receiving coils, and the range limitation of single coil detection is completely solved.

Description

Technical Field

[0001] This application belongs to the field of geophysical and geological exploration equipment, and specifically relates to a multimodal towed-hand-push transient electromagnetic detection device and its working method. Background Technology

[0002] The towed transient electromagnetic detection device mainly consists of four parts: a transmitter, a receiver, a transmitting coil, and a receiving coil. The transmitter passes a rapidly changing current into the closed transmitting coil. According to Faraday's law of electromagnetic induction, the rapidly changing current in the transmitting coil generates a rapidly changing primary magnetic field. The magnetic field induces a current in the underground medium. The current gradually decays over time, and the rate of decay is affected by the resistivity of the geological body. During the decay of the current, a secondary magnetic field is generated. The receiving coil captures the changes in the secondary field and generates an induced voltage. The receiver collects the induced voltage and analyzes and inverts it to obtain the electrical structure of the underground medium.

[0003] Currently, the transceiver coils of towed transient electromagnetic detection devices are mainly made of metal wire. Due to the parasitic inductance and distributed capacitance between each turn of the coil, and the fact that most are single-transmit and single-receive coils, towed transient electromagnetic devices have the following problems in the process of geological exploration:

[0004] The current in the transmitting coil is delayed during the turn-off process. The early signal captured by the receiving coil is affected by the turn-off process of the transmitting current. The primary field signal and the secondary field signal are superimposed, making it impossible to perform inversion calculation of the resistivity of shallow geological bodies.

[0005] Because the primary magnetic field generated by the transmitting coil has a volume effect, the smaller the transmitting and receiving coils of the towed transient electromagnetic detection device, the higher the detection resolution. However, the transmitting magnetic moment will also be smaller, resulting in a low signal-to-noise ratio and insufficient detection depth. There is a contradiction between detection depth and high resolution.

[0006] Under the same size conditions, a detection device with a single receiving coil can only collect data from a single point during rapid towing, resulting in a limited amount of data. It can only assess the location and size of underground anomalies from a two-dimensional profile perspective, leading to low detection efficiency.

[0007] In the field of towed transient electromagnetic detection devices, the above-mentioned problems have only been addressed by reducing the coupling interference between the transmitting and receiving coils; the issues of high resolution and improved detection efficiency of towed transient electromagnetic detection devices have not yet been resolved. Therefore, under the same conditions, improving the signal-to-noise ratio of late-stage data, increasing the detection depth, and simultaneously enhancing the detection efficiency of the device have become a new direction for future research on towed transient electromagnetic detection devices. Summary of the Invention

[0008] The first aspect of this application provides a multimodal towed-hand-push transient electromagnetic detection device, which mainly solves the problems of low signal-to-noise ratio, low resolution, inaccurate positioning, low working efficiency, and shallow blind zone caused by the coupling of transceiver coils.

[0009] The second aspect of this application provides a method for operating a multimodal towed-hand-push transient electromagnetic detection device.

[0010] A multimodal towed-hand-push transient electromagnetic detection device according to a first aspect embodiment of this application includes: a first receiving coil, a second receiving coil, a third receiving coil, a fourth receiving coil, a fifth receiving coil, a sixth receiving coil, a seventh receiving coil, an eighth receiving coil, and a transmitting coil. The transmitting coil is rectangular, and the first receiving coil, the second receiving coil, and the third receiving coil are arranged at equal intervals on one long side of the transmitting coil.

[0011] The fifth, sixth, and seventh receiving coils are arranged at equal intervals above the other long side of the transmitting coil;

[0012] Each long side is divided into four equal parts by the center of the three receiving coils;

[0013] The fourth receiving coil is placed at the midpoint of one short side of the transmitting coil; the corresponding eighth receiving coil is placed at the midpoint of the other short side of the transmitting coil.

[0014] All receiving coils are on the same plane and parallel to the plane containing the transmitting coil, at a distance of h. The center of each receiving coil is offset from the edge of the transmitting coil by a distance of s.

[0015] Furthermore, the method for determining the position of the receiving coil includes:

[0016] Determine the distance between the plane containing the receiving coil and the plane containing the transmitting coil;

[0017] Calculate the mutual inductance coefficient between the transmitting coil and the receiving coil at the location to be determined;

[0018] By setting the mutual inductance coefficient to zero, we can obtain the eccentricity between the center of the receiving coil and the long and short sides of the transmitting coil.

[0019] Furthermore, the spacing between the receiving coils satisfies: ,in, The mutual inductance coefficient between the first receiving coil and the other seven receiving coils. The induced current on the first receiving coil, It is the number of turns of the first receiving coil. It is the secondary field signal induced by the first receiving coil.

[0020] Furthermore, the positive and negative terminals of the eight receiving coils are connected in series to form an eight-layer superimposed receiving coil.

[0021] Furthermore, the eight receiving coils are connected in a corresponding manner to form a four-differential receiving array and a four-superimposed receiving array. Specifically, this includes: connecting the negative terminal of the first receiving coil to the negative terminal of the third receiving coil, leading out the positive terminals of the first and third receiving coils; connecting the negative terminal of the fifth receiving coil to the negative terminal of the seventh receiving coil, leading out the positive terminals of the fifth and seventh receiving coils; connecting the positive terminal of the fifth receiving coil to the positive terminal of the third receiving coil as the negative terminal of the four-differential receiving coil; connecting the positive terminal of the seventh receiving coil to the positive terminal of the first receiving coil as the positive terminal of the four-differential receiving coil; leading out the negative terminal of the second receiving coil as the negative terminal of the four-superimposed receiving coil; connecting the positive terminal of the second receiving coil to the negative terminal of the fourth receiving coil; connecting the positive terminal of the fourth receiving coil to the negative terminal of the sixth receiving coil; connecting the positive terminal of the sixth receiving coil to the negative terminal of the eighth receiving coil; and using the positive terminal of the eighth receiving coil as the positive terminal of the four-superimposed receiving coil.

[0022] Furthermore, the eight receiving coils are not connected in any series or parallel configuration and each outputs independently.

[0023] Furthermore, the eight receiving coils form four pairs of differential receiving coils, including: connecting the negative terminal of the first receiving coil to the negative terminal of the third receiving coil, and drawing out the positive terminals of the first and third receiving coils as the positive and negative terminals of the first differential receiving coil; connecting the negative terminal of the fifth receiving coil to the negative terminal of the seventh receiving coil, and drawing out the positive terminals of the fifth and seventh receiving coils as the positive and negative terminals of the second differential receiving coil; connecting the negative terminal of the second receiving coil to the negative terminal of the fourth receiving coil, and drawing out the positive terminals of the second and fourth receiving coils as the positive and negative terminals of the third differential receiving coil; connecting the negative terminal of the sixth receiving coil to the negative terminal of the eighth receiving coil, and drawing out the positive terminals of the sixth and eighth receiving coils as the positive and negative terminals of the fourth differential receiving coil; and outputting the positive and negative terminals of the four pairs of differential receiving coils respectively.

[0024] Furthermore, the eight receiving coils are arranged into four pairs of superimposed receiving coils, including: the positive terminal of the first receiving coil is connected to the negative terminal of the third receiving coil, and the negative terminal of the first receiving coil and the positive terminal of the third receiving coil are used as the positive and negative terminals of the first superimposed receiving coil; the positive terminal of the fifth receiving coil is connected to the negative terminal of the seventh receiving coil, and the negative terminal of the fifth receiving coil and the positive terminal of the seventh receiving coil are used as the positive and negative terminals of the second superimposed receiving coil; the positive terminal of the second receiving coil is connected to the negative terminal of the fourth receiving coil, and the negative terminal of the second receiving coil and the positive terminal of the fourth receiving coil are used as the positive and negative terminals of the third superimposed receiving coil; the positive terminal of the sixth receiving coil is connected to the negative terminal of the eighth receiving coil, and the negative terminal of the sixth receiving coil and the positive terminal of the eighth receiving coil are used as the positive and negative terminals of the fourth superimposed receiving coil; the positive and negative terminals of the four pairs of superimposed receiving coils are output respectively.

[0025] Furthermore, two receiving coils are combined to form a superimposed receiving coil, two receiving coils are combined to form two differential receiving coils, and four receiving coils are combined to form a four differential receiving coil. This includes: the positive terminal of the fourth receiving coil is connected to the negative terminal of the eighth receiving coil; the negative terminal of the fourth receiving coil and the positive terminal of the eighth receiving coil form the positive and negative terminals of the superimposed receiving coil; the negative terminal of the second receiving coil is connected to the negative terminal of the sixth receiving coil; the positive terminals of the second and sixth receiving coils are then used as the positive and negative terminals of the two differential receiving coils; the negative terminal of the first receiving coil is connected to the negative terminal of the third receiving coil; the negative terminal of the fifth receiving coil is connected to the negative terminal of the seventh receiving coil; the positive terminal of the first receiving coil is connected to the positive terminal of the third receiving coil to form the negative terminal of the fourth differential receiving coil; and the positive terminal of the fifth receiving coil is connected to the positive terminal of the seventh receiving coil to form the positive terminal of the four differential receiving coil. The positive and negative terminals of the superimposed receiving coil, the two differential receiving coils, and the four differential receiving coil are then output.

[0026] A method for operating a multimodal towed-hand-push transient electromagnetic detection device according to a second aspect embodiment of this application includes:

[0027] Adjust the relative positions between the eight receiving coils and the transmitting coil so that the eight receiving coils are in a zero-coupling position with the transmitting coils and the receiving coils are in a weak-coupling position with each other;

[0028] The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil, and the signal obtained after the superposition of the eight receiving coils is used as the first group of signals.

[0029] Eight receiving coils are combined into a four-differential receiving coil and a four-superimposed receiving coil. The pure secondary field signal received by the four-differential receiving coil is spliced ​​with the effective data length received by the four-superimposed receiving coil to form the second set of signals.

[0030] Without any series or parallel connection of the eight receiving coils, eight sets of individual data are acquired at each measurement point as the third set of signals;

[0031] Eight receiving coils are arranged into four pairs of differential receiving coils. The acquired differential signals are superimposed and then averaged to form the fourth group of signals.

[0032] Eight receiving coils are arranged into four pairs of superimposed receiving coils, and the average of the acquired superimposed signals is taken as the fifth group of signals.

[0033] Two of the eight receiving coils are combined into a superimposed receiving coil, two receiving coils are combined into two differential receiving coils, and four receiving coils are combined into four differential receiving coils to acquire signals at different depths as the sixth group of signals.

[0034] The first group of signals, the second group of signals, the third group of signals, the fourth group of signals, the fifth group of signals, and the sixth group of signals are inverted individually or in combination.

[0035] Compared with the prior art, the advantages of this application are as follows:

[0036] This application achieves a dual improvement in signal quality through signal superposition and differential techniques using multiple coil combinations. On one hand, the signal superposition of eight receiving coils, the averaging of signals from four superimposed receiving coils, and the averaging of differential signals significantly eliminate random noise interference. Simultaneously, the wideband characteristics of the eight receiving coils reduce early high-frequency signal distortion, ensuring the stability and accuracy of the effective signal. On the other hand, the design of four-differential and two-differential receiving coils directly eliminates primary field coupling, acquiring a pure secondary field signal and avoiding interference from the primary field on signal analysis, providing a high-quality foundation for subsequent data processing. The combination of receiving coils forms a complementary and synergistic effect, completely solving the limitation of single-coil detection range. Although the differential signals from the four-differential and two-differential receiving coils are weak, they can accurately capture shallow and near-surface anomaly signals. The four-differential receiving coil has extremely high resolution for near-surface signals, while the two-differential receiving coil has better resolution for shallower signals. The four-superimposed and dual-superimposed receiving coils, with their multiple turns, can effectively detect deep anomaly signals. The signal superposition of the eight receiving coils further enhances the ability to acquire weak deep signals. Through complementary combinations of different technologies, comprehensive coverage of geological bodies from near-surface, shallow to deep is achieved, completely eliminating blind spots in detection and ensuring that no information about underground anomalies is missed.

[0037] This application achieves a dual breakthrough in efficiency and resolution. On the one hand, it can simultaneously acquire 8 sets of signals to form a three-dimensional imaging result within a single transmission cycle, and the dual-receiver superimposed receiving coil can obtain 4 superimposed receiving coil signals within one transmission cycle, with working efficiency many times that of the conventional mode, significantly shortening the data acquisition time. On the other hand, a multi-gradient resolution system is constructed to address the characteristics of anomalies at different depths. Near-surface anomalies correspond to high resolution with four differential receiving coils, shallower anomalies correspond to better resolution with two differential receiving coils, and deep anomalies are secured by superimposed receiving coils while high-quality signal processing is combined to improve analytical accuracy. Each combination has a clear division of labor and strong targeting, which can not only quickly complete the detection task, but also meet the fine detection requirements of anomalies at different depths, making it particularly suitable for complex geological scenes with high resolution requirements. Attached Figure Description

[0038] Figure 1 A schematic diagram of the structure and coil laying method of a multimodal towed-hand-push transient electromagnetic detection device provided in an embodiment of this application;

[0039] Figure 2 A schematic diagram of a multimodal towed-hand-push transient electromagnetic detection device and coil laying method provided in another embodiment of this application;

[0040] Figure 3 A schematic diagram illustrating the relative positions of the transmitting coil and the receiving coil provided in this application;

[0041] Figure 4 This is a schematic diagram of the internal circuit structure of the transient electromagnetic transceiver provided in the embodiments of this application. Detailed Implementation

[0042] 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.

[0043] like Figure 1 Combination Figure 2 As shown, a multimodal towed-hand-push transient electromagnetic detection device includes a first receiving coil 1, a second receiving coil 2, a third receiving coil 3, a fourth receiving coil 4, a fifth receiving coil 5, a sixth receiving coil 6, a seventh receiving coil 7, an eighth receiving coil 8, a transmitting coil 9, a transient electromagnetic transceiver 10, a transport platform 11, a towing rod 12, a towing vehicle 13, a multi-core shielded wire 14, a power cord 15, and a battery 16; wherein, the transport platform 11 can be... Figure 1 The dragging platform in the middle can also be Figure 2 The hand-pushed platform in the middle.

[0044] The receiving coils (including: first receiving coil 1, second receiving coil 2, third receiving coil 3, fourth receiving coil 4, fifth receiving coil 5, sixth receiving coil 6, seventh receiving coil 7, and eighth receiving coil 8) and the transmitting coil 9 are mounted on the carrier platform 11, see [reference]. Figure 3 As shown, in this embodiment, a towed platform is used, and the transmitting coil 9 is rectangular with a long side of 2a, a short side of 2b, and Nt number of turns;

[0045] The transport platform 11 is connected to the tractor 13 by the tow bar 12. The tractor 13 serves as the power unit to drive the transport platform 11 forward, thereby enabling the exploration of underground media.

[0046] The receiving coil consists of eight receiving coils, namely the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8.

[0047] The first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 are all circular structures with the same radius and number of turns. The radius of each coil is R and the number of turns is Nr. The winding method is the same.

[0048] The first receiving coil 1, the second receiving coil 2, and the third receiving coil 3 are arranged above one long side of the rectangular transmitting coil 9. The first receiving coil 1, the second receiving coil 2, and the third receiving coil 3 are placed at equal intervals, and the long side is divided into four equal parts by the center of the three receiving coils.

[0049] Similarly, the fifth receiving coil 5, the sixth receiving coil 6, and the seventh receiving coil 7 are arranged above the other long side of the rectangular transmitting coil 9. The fifth receiving coil 5, the sixth receiving coil 6, and the seventh receiving coil 7 are placed at equal intervals, and the long side is divided into four equal parts by the center of the three receiving coils.

[0050] The fourth receiving coil 4 is placed at the midpoint of one short side of the transmitting coil 9; the corresponding eighth receiving coil 8 is placed at the midpoint of the other short side of the transmitting coil 9.

[0051] See Figure 3 As shown, all receiving coils are on the same plane, which is parallel to the plane where transmitting coil 9 is located, at a distance of h. The center of each receiving coil is offset from the side of transmitting coil 9 by a distance of s. All receiving coils are made of enameled wire.

[0052] The position of each receiving coil is determined according to the following calculation formula:

[0053] Taking the first receiving coil 1 as an example,

[0054] The calculations are performed using the same method for other receiving coils.

[0055] The mutual inductance coefficient between transmitting coil 9 and first receiving coil 1 is calculated as follows:

[0056] ,in, and It is an integration path. Indicates the integration path of the transmitting coil. This indicates the integration path of the receiving coil.

[0057] It is the mutual inductance coefficient between the transmitting coil 9 and the first receiving coil 1. It is the vacuum permeability. , These are the number of turns of the transmitting coil 9 and the number of turns of the first receiving coil 1, respectively. It is the distance from the infinitesimal element on the first receiving coil 1 to the infinitesimal element on the transmitting coil 9; if we calculate separately for each of the four sides of the transmitting coil 9, then... , These are the mutual inductance coefficients between the four sides and the first receiving coil 1; where:

[0058] ;

[0059] ;

[0060] ;

[0061] ;

[0062] It is the radius of the first receiving coil 1. It is the angle between the infinitesimal element on the first receiving coil 1 and the coordinate axis; ;

[0063] ;

[0064] ;

[0065] ;

[0066] , , , This represents the straight-line distance between the infinitesimal element on the transmitting coil and the infinitesimal element on the receiving coil.

[0067] so yes and The function is expressed as: ,make , After confirming this, That can be confirmed. Generally, a length of 2cm to 20cm is appropriate.

[0068] Based on the above calculation formula, the center coordinates of the first receiving coil 1 can be determined.

[0069] Similarly, the positions of the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 can be determined.

[0070] However, when the receiving coils are too close together, the change in magnetic flux generated on the receiving coils will also affect the signal between adjacent receiving coils. In order to avoid mutual interference between the receiving coils and obtain a pure secondary field signal, it is also necessary to constrain the relative position between the receiving coils and determine the minimum distance between the receiving coils.

[0071] Taking the first receiving coil 1 as an example, the mutual inductance coefficient between the first receiving coil 1 and the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 can be expressed as: ;

[0072] ;

[0073] ;

[0074] ;

[0075] ;

[0076] ;

[0077] ;

[0078] ;

[0079] ;

[0080] It is the mutual inductance coefficient between the first receiving coil 1 and the other 7 receiving coils (i=2,3,4,5,6,7,8), and the formula is... It comes from transformation. It is the distance between the infinitesimal element on the first receiving coil 1 and the infinitesimal elements on each of the other receiving coils (i=2,3,4,5,6,7,8). , These are the integration variables.

[0081] so yes and The function, that is: The induced voltage on the first receiving coil 1 can be expressed as: , It is the current in transmitting coil 9. It is the induced current on the first receiving coil; It is the secondary field signal induced by the first receiving coil 1, when At this time, it can be assumed that there is no interference between the receiving coils; The distance constraints between the receiving coils are given. The receiving coils cannot be too close, otherwise they will interfere with each other and affect the secondary field data.

[0082] The transient electromagnetic transceiver unit 10 is mounted on the tractor; see also Figure 1 The transient electromagnetic transceiver 10 is connected to the transmitting coil 9, the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 via a multi-core shielded cable 14.

[0083] The transient electromagnetic transceiver 10 is connected to the battery 16 by a power cable 15, and the battery 15 supplies power to the transient electromagnetic transceiver 10.

[0084] The instantaneous current in the transmitting coil 9 is relatively large, reaching up to 1000A or more, therefore the transmitting coil 9 is made of high-power wire.

[0085] See Figure 4 As shown, the transient electromagnetic transceiver 10 consists of a filter circuit module 10-1, an operational amplifier circuit module 10-2, an ADC acquisition card 10-3, an FPGA control board 10-4, a 12V voltage converter 10-5, an SD card 10-6, a human-machine interface 10-7, an Ethernet interface 10-8, a host computer 10-9, an optocoupler isolation circuit 10-10, an H-bridge drive circuit 10-11, an H-bridge circuit 10-13, and a DC-DC converter 10-12.

[0086] Among them, the filter circuit module 10-1 is mainly used to filter out noise in the received signal, the operational amplifier circuit module 10-2 is used to amplify the weak received signal, the ADC acquisition card 10-3 converts the analog signal amplified by the operational amplifier circuit module 10-2 into a digital signal and transmits it to the FPGA control board 10-4. After processing the signal, the FPGA control board 10-4 transmits it to the host computer 10-9 for display through the Ethernet interface 10-8, and at the same time stores the data in the SD card 10-6. The human-machine interface 10-7 is mainly used to set the specific parameters of data acquisition, such as sampling frequency, sampling duration, etc.

[0087] DC-DC converter 10-12 converts the voltage of battery 16 for use in H-bridge circuit 10-13;

[0088] The 12V voltage converter 10-5 converts the voltage of the battery 16 and then supplies power to the filter circuit module 10-1, the operational amplifier circuit module 10-2, the ADC acquisition board 10-3, the FPGA control board 10-4, the SD card 10-6, the human-machine interface 10-7, and the Ethernet interface 10-8.

[0089] Furthermore, the filter circuit module 10-1 has 8 channels; the operational amplifier circuit module 10-2 has 8 channels, each corresponding to a filter circuit; the operational amplifier circuit module 10-2 is connected to the ADC acquisition card 10-3 to convert the 8 analog signals into digital signals; the ADC acquisition card 10-3 communicates with the FPGA control board 10-4, and the FPGA control board 10-4 controls the timing of the digital signals of the ADC acquisition card 10-3; the FPGA control board 10-4 stores the acquired digital signals in the SD card 10-6 for subsequent data processing, and also transmits the data to the host computer 10-9 for display and inversion calculation via the Ethernet 10-8 interface; the FPGA control board 10-4 is connected to the human-machine interface 10-7, and the operator controls the FPGA control board 10-4 to generate PWM waves of specific frequency and pulse width through the human-machine interface 10-7;

[0090] Furthermore, the FPGA control board 10-4 is connected to the H-bridge drive circuit 10-11 through the optocoupler isolation circuit 10-10. The PWM wave generated by the FPGA control board 10-4 controls the switching and closing of the bridge arm of the H-bridge circuit 10-13, generating a bipolar current trapezoidal wave in the transmitting coil 9.

[0091] The positive and negative terminals of each receiving coil are led out for different combinations of operating modes;

[0092] There are a total of 6 combination patterns;

[0093] In combination mode one, the positive and negative terminals of eight receiving coils are connected in series to form an eight-overlay receiving coil. Specifically, the negative terminal of the first receiving coil 1 is used as the negative terminal of the eight-overlay receiving coil. The positive terminal of the first receiving coil 1 is connected to the negative terminal of the second receiving coil 2. The positive terminal of the second receiving coil 2 is connected to the negative terminal of the third receiving coil 3. The positive terminal of the third receiving coil 3 is connected to the negative terminal of the fourth receiving coil 4. The positive terminal of the fourth receiving coil 4 is connected to the negative terminal of the fifth receiving coil 5. The positive terminal of the fifth receiving coil 5 is connected to the negative terminal of the sixth receiving coil 6. The positive terminal of the sixth receiving coil 6 is connected to the negative terminal of the seventh receiving coil 7. The positive terminal of the seventh receiving coil 7 is connected to the negative terminal of the eighth receiving coil 8. The positive terminal of the eighth receiving coil 8 is used as the positive terminal of the eight-overlay receiving coil. The positive and negative terminals of the eight-overlay receiving coil are connected to any one of the channels of the filter circuit module 10-1. The advantage of this combination method is that the received signals of the eight receiving coils can be superimposed, and the bandwidth of the eight receiving coils is relatively wide. This can reduce early high-frequency signal distortion and obtain deeper and weak underground anomaly signals.

[0094] In combination mode two, eight receiving coils are connected in corresponding ways to form a four-differential receiving array and a four-superimposed receiving array. The negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, leading out the positive terminals of the first receiving coil 1 and the third receiving coil 3. The negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, leading out the positive terminals of the fifth receiving coil 5 and the seventh receiving coil 7. The positive terminal of the fifth receiving coil 5 is connected to the positive terminal of the third receiving coil 3 as the negative terminal of the four-differential receiving coil. The positive terminal of the seventh receiving coil 7 is connected to the positive terminal of the first receiving coil 1 as the positive terminal of the four-differential receiving coil. The positive and negative terminals of the four-differential receiving coil are connected to any one of the paths of the filter circuit module 10-1. The negative terminal of the second receiving coil 2 is led out as the negative terminal of the four-superimposed receiving coil. The positive terminal of receiving coil 2 is connected to the negative terminal of the fourth receiving coil 4, the positive terminal of the fourth receiving coil 4 is connected to the negative terminal of the sixth receiving coil 6, the positive terminal of the sixth receiving coil 6 is connected to the negative terminal of the eighth receiving coil 8, and the positive terminal of the eighth receiving coil 8 serves as the positive terminal of the four-overlay receiving coil. The negative and positive terminals of the four-overlay receiving coil are connected to another path of the filter circuit. The advantage of this combination is that the four differential receiving coils can obtain a pure secondary field signal without interference from the primary field. However, due to the weakness of the differential signal and the short effective signal length, it can only detect shallow anomalies. The four-overlay receiving coil has more turns and can detect deep anomalies. However, the early secondary field signal is submerged in the primary field signal, resulting in the loss of shallow information. The four differential receiving coils and the four-overlay receiving coils can complement each other to obtain geological information without blind spots.

[0095] In combination mode three, the eight receiving coils are not connected in any series or parallel connection, but are respectively connected to the eight-channel filter circuit of filter circuit module 10-1. The signals of the eight receiving coils are collected separately, and then the algorithm is used to invert and calculate the eight signals to obtain eight sets of resistivity values. Based on the position of the receiving coils and the distribution of resistivity values, a set of three-dimensional cloud map results can be obtained. The X and Y coordinates represent the position of the receiving coils, Z represents the depth information, and the color of the cloud map represents the resistivity value. This combination method is equivalent to simultaneously collecting eight sets of signals to form a three-dimensional imaging result within one transmission cycle.

[0096] In combination mode four, eight receiving coils form four pairs of differential receiving coils. The negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, and the positive terminals of the first receiving coil 1 and the third receiving coil 3 are used as the positive and negative terminals of the first differential receiving coil. The negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, and the positive terminals of the fifth receiving coil 5 and the seventh receiving coil 7 are used as the positive and negative terminals of the second differential receiving coil. The negative terminal of the second receiving coil 2 is connected to the negative terminal of the fourth receiving coil 4, and the positive terminals of the second receiving coil 2 and the fourth receiving coil 4 are used as the positive and negative terminals of the third differential receiving coil. The negative terminal of the sixth receiving coil 6 is connected to the negative terminal of the eighth receiving coil. The negative terminal of coil 8 is connected to lead out the positive terminals of the sixth receiving coil 6 and the eighth receiving coil 8 as the positive and negative terminals of the fourth differential receiving coil. The positive and negative terminals of the four pairs of differential receiving coils are respectively connected to the four-channel filtering circuit of the filtering circuit module 10-1. The average signal of the four pairs of differential receiving coils is obtained by superimposing and averaging the acquired signals of the four pairs of differential receiving coils using an algorithm. The advantage of this combination method is that the differential signal between two receiving coils can eliminate the primary field coupling and obtain a pure secondary field signal, achieving the purpose of blind zone-free detection. At the same time, the differential signal is very weak. Superimposing and averaging the differential signals can partially eliminate random noise interference and obtain fine detection results of shallow ground.

[0097] In combination mode five, eight receiving coils form four pairs of superimposed receiving coils: the positive terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, and the negative terminal of the first receiving coil 1 and the positive terminal of the third receiving coil 3 are used as the positive and negative terminals of the first superimposed receiving coil; the positive terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, and the negative terminal of the fifth receiving coil 5 and the positive terminal of the seventh receiving coil 7 are used as the positive and negative terminals of the second superimposed receiving coil; the positive terminal of the second receiving coil 2 is connected to the negative terminal of the fourth receiving coil 4, and the negative terminal of the second receiving coil 2 and the positive terminal of the fourth receiving coil 4 are used as the positive and negative terminals of the third superimposed receiving coil; the positive terminal of the sixth receiving coil 6 is connected to the negative terminal of the eighth receiving coil 8... The negative terminal of the sixth receiving coil 6 and the positive terminal of the eighth receiving coil 8 are connected to the fourth superimposed receiving coil as the positive and negative terminals. The positive and negative terminals of the four pairs of superimposed receiving coils are connected to the four-way filtering circuit of the filtering circuit module 10-1 respectively. The average signal of the four pairs of superimposed receiving coils is obtained by superimposing and averaging the acquired signals of the four pairs of superimposed receiving coils using an algorithm. The advantage of this combination method is that two receiving coils form a superimposed receiving coil, which can obtain signals of deeper anomalous objects. At the same time, the signals of the superimposed receiving coils can be obtained 4 times in one transmission cycle, which is 4 times more efficient than that of a single receiving coil. Averaging the 4 signals can eliminate some random noise and improve the resolution of deep anomalous objects.

[0098] Combination mode six involves two receiving coils forming a superimposed receiving coil, two receiving coils forming two differential receiving coils, and four receiving coils forming four differential receiving coils. Specifically: the positive terminal of the fourth receiving coil 4 is connected to the negative terminal of the eighth receiving coil 8; the negative terminal of the fourth receiving coil 4 and the positive terminal of the eighth receiving coil 8 form the positive and negative terminals of the superimposed receiving coil; the negative terminal of the second receiving coil 2 is connected to the negative terminal of the sixth receiving coil 6; the positive terminals of the second receiving coil 2 and the sixth receiving coil 6 are then used as the positive and negative terminals of the two differential receiving coils; the negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3; the negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7; and the positive terminal of the first receiving coil 1 is connected to the positive terminal of the third receiving coil 3. The negative terminal of the fourth differential receiving coil, the positive terminals of the fifth and seventh receiving coils (5 and 7) are connected to form the positive terminal of the four differential receiving coils. The positive and negative terminals of the superimposed receiving coil, the two differential receiving coils, and the four differential receiving coil are connected to the three-channel filtering circuit of the filtering circuit module 10-1. The three signals are normalized and then spliced. The advantage of this combination is that the signal from the superimposed receiving coil can obtain signals from deep anomalies, but with low resolution; the two differential receiving coils and the four differential receiving coils can both obtain pure secondary field signals; the signals from the two differential receiving coils can obtain signals from shallower anomalies, with higher resolution; and the four differential receiving coils can obtain signals from near-surface anomalies, with very high resolution. The shallower the anomaly, the smaller its volume, and the higher the resolution requirement. The three combined coils have multi-gradient resolution for anomalies at different depths, each with its own function, resulting in high efficiency and achieving the goal of fine detection.

[0099] The transient electromagnetic transceiver unit 10 is mounted on the tractor; see also Figure 1 The transient electromagnetic transceiver 10 is connected to the transmitting coil 9, the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 via a multi-core shielded cable 14.

[0100] The transient electromagnetic transceiver 10 is connected to the battery 16 by a power cable 15, and the battery 15 supplies power to the transient electromagnetic transceiver 10.

[0101] The instantaneous current in the transmitting coil 9 is relatively large, reaching up to 1000A or more, therefore the transmitting coil 9 is made of high-power wire.

[0102] On the other hand, the working method of the multimodal towed-hand-push transient electromagnetic detection device provided in this application includes: adjusting the relative positions between eight receiving coils and transmitting coil 9 so that the eight receiving coils and transmitting coil 9 are in a zero-coupling position and the receiving coils are in a weak-coupling position with each other.

[0103] The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil, and the signal obtained after the superposition of the eight receiving coils is used as the first group of signals.

[0104] Eight receiving coils are combined into a four-differential receiving coil and a four-superimposed receiving coil. The pure secondary field signal received by the four-differential receiving coil is spliced ​​with the effective data length received by the four-superimposed receiving coil to form the second set of signals.

[0105] Without any series or parallel connection of the eight receiving coils, eight sets of individual data are acquired at each measurement point as the third set of signals;

[0106] Eight receiving coils are arranged into four pairs of differential receiving coils. The acquired differential signals are superimposed and then averaged to form the fourth group of signals.

[0107] Eight receiving coils are arranged into four pairs of superimposed receiving coils, and the average of the acquired superimposed signals is taken as the fifth group of signals.

[0108] Two of the eight receiving coils are combined into a superimposed receiving coil, two receiving coils are combined into two differential receiving coils, and four receiving coils are combined into four differential receiving coils to acquire signals at different depths as the sixth group of signals.

[0109] The first group of signals, the second group of signals, the third group of signals, the fourth group of signals, the fifth group of signals, and the sixth group of signals are inverted individually or in combination.

[0110] Specifically, it includes:

[0111] The first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, the eighth receiving coil 8, and the transmitting coil 9 are fixed on the transport platform 11. The transient electromagnetic transceiver host 10 is installed on the tractor 13. The first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, the eighth receiving coil 8, the transmitting coil 9 and the transient electromagnetic transceiver host 10 are connected by a multi-core shielded wire 14.

[0112] Adjust the relative positions of the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, the eighth receiving coil 8 and the transmitting coil 9 so that the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, the eighth receiving coil 8 and the transmitting coil 9 are in a zero-coupling position, and the receiving coils are in a weak-coupling position with each other;

[0113] A rectangular transmitting coil 9 with Nt turns is fixed on the carrier platform 11, with the long side being 2a and the short side being 2b;

[0114] The transport platform 11 was towed to an open area with uniform underground geological formations, the resistivity of which was [missing information]. The device is then adjusted and calibrated. This calibration is performed only once after the device is manufactured. If the relative positions of the receiving coil and the transmitting coil 9 remain unchanged, further calibration is unnecessary. The calibration method is as follows:

[0115] The transient electromagnetic transceiver 10 controls the transmission of a bipolar current trapezoidal wave through the transmitting coil 9;

[0116] Calculate the horizontal relative position of the receiving coil and the transmitting coil 9. Observe the voltage waveforms on the first receiving coil 1, the second receiving coil 2, the third receiving coil 3, the fourth receiving coil 4, the fifth receiving coil 5, the sixth receiving coil 6, the seventh receiving coil 7, and the eighth receiving coil 8 individually using an oscilloscope. Fine-tune the relative position between the receiving coil and the transmitting coil 9 until the starting point of the secondary field of the eight voltage waveforms coincides with the ending point of the transmission current turn-off process. Adjust the eight voltage waveforms to be consistent or nearly consistent. This is because the primary field coupling signal can be considered zero.

[0117] Furthermore, a towed-hand-push transient electromagnetic fine detection device based on a multi-gradient receiving coil has a total of six operating modes.

[0118] Work Mode 1:

[0119] The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil. Specifically, the negative terminal of the first receiving coil 1 is used as the negative terminal of the eight-layer superimposed receiving coil. The positive terminal of the first receiving coil 1 is connected to the negative terminal of the second receiving coil 2. The positive terminal of the second receiving coil 2 is connected to the negative terminal of the third receiving coil 3. The positive terminal of the third receiving coil 3 is connected to the negative terminal of the fourth receiving coil 4. The positive terminal of the fourth receiving coil 4 is connected to the negative terminal of the fifth receiving coil 5. The positive terminal of the fifth receiving coil 5 is connected to the negative terminal of the sixth receiving coil 6. The positive terminal of the sixth receiving coil 6 is connected to the negative terminal of the seventh receiving coil 7. The positive terminal of the seventh receiving coil 7 is connected to the negative terminal of the eighth receiving coil 8. The positive terminal of the eighth receiving coil 8 is used as the positive terminal of the eight-layer superimposed receiving coil. The positive and negative terminals of the eight receiving coils are connected to any one of the paths in the filter circuit module 10-1. Assume the voltage waveforms of the eight receiving coils are as follows: , , , , , , , The voltage waveform of each receiving coil is generated by a primary field-coupled signal. Secondary field signal The sum of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composition, therefore: ;

[0120] The signal after the eight receiving coils are superimposed ;in This is random noise, which can be partially attenuated during the superposition process. The positions between the receiving coils are determined to be weakly coupled during the design process, and the coupling signal between the receiving coils... It can be ignored that, after calibrating the relative positions of the receiving coil and the transmitting coil 9, the primary field coupling signal can be considered to be zero, i.e. Therefore, within the effective data length, , for signal Inversion is performed. In this operating mode, it consists of eight receiving coils. The receiving coil composed of stacked receiving coils and a single receiving coil The receiving coils of the turns receive the same signal strength, but with a wider bandwidth. The wider bandwidth of the eight receiving coils can reduce early high-frequency signal distortion and obtain signals from deeper, weaker underground anomalies.

[0121] Working Mode Two:

[0122] Eight receiving coils form a four-differential receiving coil and a four-overlapping receiving coil. The negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, thus bringing out the positive terminals of the first receiving coil 1 and the third receiving coil 3. The negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, thus bringing out the positive terminals of the fifth receiving coil 5 and the seventh receiving coil 7. The positive terminal of the fifth receiving coil 5 is connected to the positive terminal of the third receiving coil 3 as the negative terminal of the four-differential receiving coil. The positive terminal of the seventh receiving coil 7 is connected to the positive terminal of the first receiving coil 1 as the positive terminal of the four-differential receiving coil. Connect the positive and negative terminals of the four differential receiving coils to any one of the paths in the filter circuit module 10-1; lead out the negative terminal of the second receiving coil 2 as the negative terminal of the four superimposed receiving coils; connect the positive terminal of the second receiving coil 2 to the negative terminal of the fourth receiving coil 4; connect the positive terminal of the fourth receiving coil 4 to the negative terminal of the sixth receiving coil 6; connect the positive terminal of the sixth receiving coil 6 to the negative terminal of the eighth receiving coil 8; and use the positive terminal of the eighth receiving coil 8 as the positive terminal of the four superimposed receiving coils. Connect the negative and positive terminals of the four superimposed receiving coils to another path in the filter circuit; after ADC conversion, two signals can be acquired, namely... and The four differential receiving coils receive a pure secondary field signal, but due to the weak signal and the significant noise affecting the later stages, inversion calculations are not possible. Therefore, the effective length of the data is taken as... The early signal from the four superimposed receiving coils was affected by the primary field superposition, making it impossible to extract the secondary field signal. Therefore, the effective length of the data was taken as... , , , Both represent points in time, where 0 After normalizing the two signals, they can be spliced ​​together to obtain the final signal. The four differential receiving coils and the four superimposed receiving coils can complement each other to obtain geological body information without blind spots.

[0123] Working Mode 3:

[0124] The eight receiving coils are not connected in any series or parallel configuration, but are respectively connected to the eight-channel filter circuit of the filter circuit module. The signals from the eight receiving coils are collected separately, resulting in eight signals, which are respectively... , , , , , , , By performing individual inversion calculations on the eight signals, eight sets of data for a single measurement point can be obtained. , , , , , , , , This represents the resistivity inversion result of a single receiving coil. It is a depth value, based on the positions of the eight receiving coils. , , , , , , , This can create a 3D cloud map result, where the X and Y coordinates represent the positions of the eight receiving coils. Indicates the depth value. = The color depth of the cloud map is determined by resistivity. express.

[0125] Working Mode Four:

[0126] Eight receiving coils form four pairs of differential receiving coils. The negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, and the positive terminals of the first and third receiving coils 1 and 3 are used as the positive and negative terminals of the first differential receiving coil. The negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, and the positive terminals of the fifth and seventh receiving coils 5 and 7 are used as the positive and negative terminals of the second differential receiving coil. The negative terminal of the second receiving coil 2 is connected to the negative terminal of the fourth receiving coil 4, and the positive terminals of the second and fourth receiving coils 2 and 4 are used as the positive and negative terminals of the third differential receiving coil. The negative terminal of the sixth receiving coil 6 is connected to the negative terminal of the eighth receiving coil 8, and the positive terminals of the sixth and eighth receiving coils 6 and 8 are used as the positive and negative terminals of the fourth differential receiving coil. The positive and negative terminals of the four pairs of differential receiving coils are connected to the four filtering circuits of the filtering circuit module to collect the four received signals respectively. , , , After differential processing, none of the four received signals contain the primary field coupling signal. Therefore, the voltage waveform of each differential receiving coil is composed of the secondary field signal. Total of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composition, therefore:

[0127] ;

[0128] ;

[0129] express , , , The positions between the receiving coils were determined to be weakly coupled during the design process, and the coupling signals between the receiving coils... It can be ignored; It is the average value after superposition, which can eliminate some of the differences. Extend the effective length of the signal, that is The effective length is ,but The effective length is ;0< < . and All are time points.

[0130] The advantage of this working mode is that the differential signal between the two receiving coils can eliminate primary field coupling and obtain a pure secondary field signal, achieving the purpose of blind zone-free detection; at the same time, the differential signal is very weak, and by superimposing the differential signals and averaging them, random noise interference can be partially eliminated, and fine detection results of shallow ground surface can be obtained.

[0131] Work Mode 5:

[0132] Eight receiving coils form four pairs of superimposed receiving coils. The positive terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, and the negative terminals of the first receiving coil 1 and the positive terminals of the third receiving coil 3 are used as the positive and negative terminals of the first superimposed receiving coil. The positive terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7, and the negative terminals of the fifth receiving coil 5 and the positive terminals of the seventh receiving coil 7 are used as the positive and negative terminals of the second superimposed receiving coil. The positive terminal of the second receiving coil 2 is connected to the negative terminal of the fourth receiving coil 4, and the negative terminals of the second receiving coil 2 and the positive terminals of the fourth receiving coil 4 are used as the positive and negative terminals of the third superimposed receiving coil. The positive terminal of the sixth receiving coil 6 is connected to the negative terminal of the eighth receiving coil 8, and the negative terminals of the sixth receiving coil 6 and the positive terminals of the eighth receiving coil 8 are used as the positive and negative terminals of the fourth superimposed receiving coil. The positive and negative terminals of the four pairs of superimposed receiving coils are respectively connected to the four filtering circuits of the filtering circuit module to collect four received signals. , , , The voltage waveform of each superimposed receiving coil is composed of a primary field signal. Secondary field signal Total of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composition, therefore:

[0133] ;

[0134] = ( + + + );

[0135] express , , , The positions between the receiving coils were determined to be weakly coupled during the design process, and the coupling signals between the receiving coils... It can be ignored; It is the average value after superposition, which can eliminate some of the differences. Extend the effective length of the signal, that is The effective length is ,but The effective length is ; , and Indicating the time point, the advantage of this working mode is that the two receiving coils form a superimposed receiving coil, which can obtain signals of deeper anomalous objects; at the same time, the signals of the superimposed receiving coil can be obtained 4 times in one transmission cycle, which is 4 times more efficient than the single receiving coil. Averaging the 4 signals can eliminate some random noise and improve the resolution of deep anomalous objects.

[0136] Work Mode Six:

[0137] Two of the eight receiving coils form a superimposed receiving coil, two receiving coils form two differential receiving coils, and four receiving coils form a four differential receiving coil. The positive terminal of the fourth receiving coil 4 is connected to the negative terminal of the eighth receiving coil 8. The negative terminal of the fourth receiving coil 4 and the positive terminal of the eighth receiving coil 8 form the positive and negative terminals of the superimposed receiving coil. The negative terminal of the second receiving coil 2 is connected to the negative terminal of the sixth receiving coil 6. The positive terminals of the second receiving coil 2 and the sixth receiving coil 6 are used as the positive and negative terminals of the two differential receiving coils. The first receiving coil 1... The negative terminal of the first receiving coil 1 is connected to the negative terminal of the third receiving coil 3, and the negative terminal of the fifth receiving coil 5 is connected to the negative terminal of the seventh receiving coil 7. The positive terminal of the first receiving coil 1 is connected to the positive terminal of the third receiving coil 3 to form the negative terminal of the fourth differential receiving coil. The positive terminals of the fifth receiving coil 5 and the seventh receiving coil 7 are connected to form the positive terminal of the four differential receiving coils. The positive and negative terminals of the superimposed receiving coil, the two differential receiving coils, and the four differential receiving coils are respectively connected to the three-channel filtering circuit of the filtering circuit module 10-1. One received signal is collected. From a single field signal Secondary field signal Total of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composed of one channel for receiving signals From secondary field signal Total of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composed of one channel for receiving signals From secondary field signal Total of all types of electromagnetic noise Coupled signal between the receiving coil and the receiving coil Composition, namely:

[0138] = + + + ;

[0139] = + + ;

[0140] = + + ;

[0141] After normalization of the three signals, they are respectively , , Superimposed signals from the receiving coil can obtain signals from deep anomalies, but the resolution is low and the early signals contain primary field signals, so the effective signal is... Both two-differential and four-differential receiving coils can obtain pure secondary field signals. The signals from the two differential coils can obtain signals of shallower anomalous bodies, with high resolution and an effective signal of [missing information]. Four differential receiving coils can acquire near-surface anomalous body signals with higher resolution and an effective signal of [missing information]. ( ),in < < < Both represent time. The three signals are then spliced ​​together. + ( The shallower the depth of the anomalous object, the smaller its volume is generally, and the higher the resolution requirement. The three combined receiving coils have multi-gradient resolution for anomalous objects at different depths, each with its own function, resulting in high working efficiency and achieving the purpose of fine detection.

[0142] 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 multimodal towed-hand-push transient electromagnetic detection device, characterized in that, include: The first receiving coil (1), the second receiving coil (2), the third receiving coil (3), the fourth receiving coil (4), the fifth receiving coil (5), the sixth receiving coil (6), the seventh receiving coil (7), the eighth receiving coil (8), and the transmitting coil (9) are rectangular. The first receiving coil (1), the second receiving coil (2), and the third receiving coil (3) are arranged at equal intervals on one long side of the transmitting coil (9). The fifth receiving coil (5), the sixth receiving coil (6), and the seventh receiving coil (7) are arranged at equal intervals above the other long side of the transmitting coil (9); Each long side is divided into four equal parts by the center of the three receiving coils; The fourth receiving coil (4) is placed at the midpoint of one short side of the transmitting coil (9); the corresponding eighth receiving coil (8) is placed at the midpoint of the other short side of the transmitting coil (9); All receiving coils are on the same plane and parallel to the plane where the transmitting coil (9) is located, at a distance of h. The center of each receiving coil is offset from the edge of the transmitting coil (9) by a distance of s. Methods for determining the position of the receiving coil include: Determine the distance between the plane containing the receiving coil and the plane containing the transmitting coil (9); Calculate the mutual inductance coefficient between the transmitting coil (9) and the receiving coil at the location to be determined; By setting the mutual inductance coefficient to zero, the eccentricity between the center of the receiving coil and the long and short sides of the transmitting coil (9) is obtained. The spacing between the receiving coils satisfies: ,in, The mutual inductance coefficient between the first receiving coil (1) and the other seven receiving coils is... The induced current on the first receiving coil (1), It is the number of turns of the first receiving coil (1). It is the secondary field signal sensed by the first receiving coil (1); Adjust the relative positions between the eight receiving coils and the transmitting coil (9) so that the eight receiving coils and the transmitting coil (9) are in a zero-coupling position and the receiving coils are in a weak-coupling position; The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil, and the signal obtained after the superposition of the eight receiving coils is used as the first group of signals. Eight receiving coils are combined into a four-differential receiving coil and a four-superimposed receiving coil. The pure secondary field signal received by the four-differential receiving coil is spliced ​​with the effective data length received by the four-superimposed receiving coil to form the second set of signals. Without any series or parallel connection of the eight receiving coils, eight sets of individual data are acquired at each measurement point as the third set of signals; Eight receiving coils are arranged into four pairs of differential receiving coils. The acquired differential signals are superimposed and then averaged to form the fourth group of signals. Eight receiving coils are arranged into four pairs of superimposed receiving coils, and the average of the acquired superimposed signals is taken as the fifth group of signals. Two of the eight receiving coils are combined into a superimposed receiving coil, two receiving coils are combined into two differential receiving coils, and four receiving coils are combined into four differential receiving coils to acquire signals at different depths as the sixth group of signals. The first group of signals, the second group of signals, the third group of signals, the fourth group of signals, the fifth group of signals, and the sixth group of signals are inverted individually or in combination.

2. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil.

3. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, Eight receiving coils are connected in a corresponding manner to form a four-differential receiving array and a four-superimposed receiving array; specifically, the negative terminal of the first receiving coil (1) is connected to the negative terminal of the third receiving coil (3) to bring out the positive terminals of the first receiving coil (1) and the third receiving coil (3); the negative terminal of the fifth receiving coil (5) is connected to the negative terminal of the seventh receiving coil (7) to bring out the positive terminals of the fifth receiving coil (5) and the seventh receiving coil (7); and the positive terminal of the fifth receiving coil (5) is connected to the positive terminal of the third receiving coil (3) to form a four-differential receiving array. The negative terminal of the differential receiving coil, the positive terminal of the seventh receiving coil (7) is connected to the positive terminal of the first receiving coil (1) as the positive terminal of the four differential receiving coils; the negative terminal of the second receiving coil (2) is led out as the negative terminal of the four superimposed receiving coils, the positive terminal of the second receiving coil (2) is connected to the negative terminal of the fourth receiving coil (4), the positive terminal of the fourth receiving coil (4) is connected to the negative terminal of the sixth receiving coil (6), the positive terminal of the sixth receiving coil (6) is connected to the negative terminal of the eighth receiving coil (8), and the positive terminal of the eighth receiving coil (8) is the positive terminal of the four superimposed receiving coils.

4. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, The eight receiving coils are not connected in any series or parallel, and each outputs independently.

5. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, Eight receiving coils form four pairs of differential receiving coils, including: connecting the negative terminal of the first receiving coil (1) to the negative terminal of the third receiving coil (3), and leading out the positive terminals of the first receiving coil (1) and the third receiving coil (3) as the positive and negative terminals of the first differential receiving coil; connecting the negative terminal of the fifth receiving coil (5) to the negative terminal of the seventh receiving coil (7), and leading out the positive terminals of the fifth receiving coil (5) and the seventh receiving coil (7) as the positive and negative terminals of the second differential receiving coil; connecting the negative terminal of the second receiving coil (2) to the negative terminal of the fourth receiving coil (4), and leading out the positive terminals of the second receiving coil (2) and the fourth receiving coil (4) as the positive and negative terminals of the third differential receiving coil; connecting the negative terminal of the sixth receiving coil (6) to the negative terminal of the eighth receiving coil (8), and leading out the positive terminals of the sixth receiving coil (6) and the eighth receiving coil (8) as the positive and negative terminals of the fourth differential receiving coil; and outputting the positive and negative terminals of the four pairs of differential receiving coils respectively.

6. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, Eight receiving coils are arranged into four pairs of superimposed receiving coils, including: the positive terminal of the first receiving coil (1) is connected to the negative terminal of the third receiving coil (3), and the negative terminal of the first receiving coil (1) and the positive terminal of the third receiving coil (3) are taken out as the positive and negative terminals of the first superimposed receiving coil; the positive terminal of the fifth receiving coil (5) is connected to the negative terminal of the seventh receiving coil (7), and the negative terminal of the fifth receiving coil (5) and the positive terminal of the seventh receiving coil (7) are taken out as the positive and negative terminals of the second superimposed receiving coil; the positive terminal of the second receiving coil (2) is connected to the negative terminal of the fourth receiving coil (4), and the negative terminal of the second receiving coil (2) and the positive terminal of the fourth receiving coil (4) are taken out as the positive and negative terminals of the third superimposed receiving coil; the positive terminal of the sixth receiving coil (6) is connected to the negative terminal of the eighth receiving coil (8), and the negative terminal of the sixth receiving coil (6) and the positive terminal of the eighth receiving coil (8) are taken out as the positive and negative terminals of the fourth superimposed receiving coil; the positive and negative terminals of the four pairs of superimposed receiving coils are output respectively.

7. The multimodal towed-hand-push transient electromagnetic detection device according to claim 1, characterized in that, Two receiving coils are combined to form a superimposed receiving coil, two receiving coils are combined to form two differential receiving coils, and four receiving coils are combined to form a four differential receiving coil. This includes: the positive terminal of the fourth receiving coil (4) is connected to the negative terminal of the eighth receiving coil (8); the negative terminal of the fourth receiving coil (4) and the positive terminal of the eighth receiving coil (8) form the positive and negative terminals of the superimposed receiving coil; the negative terminal of the second receiving coil (2) is connected to the negative terminal of the sixth receiving coil (6); and the positive terminals of the second receiving coil (2) and the sixth receiving coil (6) are led out as two differential receiving coils. The negative terminals of the first receiving coil (1) are connected to the negative terminal of the third receiving coil (3), and the negative terminal of the fifth receiving coil (5) is connected to the negative terminal of the seventh receiving coil (7). The positive terminal of the first receiving coil (1) is connected to the positive terminal of the third receiving coil (3) to form the negative terminal of the fourth differential receiving coil. The positive terminal of the fifth receiving coil (5) and the positive terminal of the seventh receiving coil (7) are connected to form the positive terminal of the four differential receiving coils. The positive and negative terminals of the superimposed receiving coil, the positive and negative terminals of the two differential receiving coils, and the positive and negative terminals of the four differential receiving coils are output respectively.

8. A method of operating the multimodal towed-hand-push transient electromagnetic detection device according to any one of claims 1-7, characterized in that, include: Adjust the relative positions between the eight receiving coils and the transmitting coil (9) so that the eight receiving coils and the transmitting coil (9) are in a zero-coupling position and the receiving coils are in a weak-coupling position; The positive and negative terminals of eight receiving coils are connected in series to form an eight-layer superimposed receiving coil, and the signal obtained after the superposition of the eight receiving coils is used as the first group of signals. Eight receiving coils are combined into a four-differential receiving coil and a four-superimposed receiving coil. The pure secondary field signal received by the four-differential receiving coil is spliced ​​with the effective data length received by the four-superimposed receiving coil to form the second set of signals. Without any series or parallel connection of the eight receiving coils, eight sets of individual data are acquired at each measurement point as the third set of signals; Eight receiving coils are arranged into four pairs of differential receiving coils. The acquired differential signals are superimposed and then averaged to form the fourth group of signals. Eight receiving coils are arranged into four pairs of superimposed receiving coils, and the average of the acquired superimposed signals is taken as the fifth group of signals. Two of the eight receiving coils are combined into a superimposed receiving coil, two receiving coils are combined into two differential receiving coils, and four receiving coils are combined into four differential receiving coils to acquire signals at different depths as the sixth group of signals. The first group of signals, the second group of signals, the third group of signals, the fourth group of signals, the fifth group of signals, and the sixth group of signals are inverted individually or in combination.

Images