Vehicle-mounted transient electromagnetic underground space detection system and method based on primary field weak coupling

Abstract

Provided are a vehicle-mounted transient electromagnetic underground space detection system and method based on primary field weak coupling. The detection system comprises: a transmitting subsystem that sends out a set current pulse signal; a transceiver coil subsystem, comprising: a circular transmitting coil that generates a primary magnetic field signal after being loaded with a current pulse signal, and generates a secondary magnetic field signal after the primary magnetic field signal acts on the underground space; two circular receiving coils, respectively arranged on the upper and lower sides of the transmitting coil, for receiving the z-component induction signal of the secondary magnetic field signal and offsetting the interference of the primary magnetic field signal; an x-component rectangular receiving coil that is arranged perpendicular to the plane where the transmitting coil is located, for receiving the x-component induction signal of the secondary magnetic field signal; a y-component rectangular receiving coil that crosses perpendicularly with the x-component rectangular receiving coil and is arranged perpendicularly to the transmitting coil, for receiving the y-component induction signal of the secondary magnetic field signal; and a receiving subsystem, for synchronously collecting and processing the three-component induction signals to obtain underground target detection information.

Description

Technical Field

[0001] The present disclosure relates to the field of electromagnetic technology, and in particular to a vehicle-mounted transient electromagnetic underground space detection system and method based on primary field weak coupling. Background Art

[0002] With the continuous acceleration of urbanization, the safe use of urban underground space and the precise detection of urban underground space have become the focus of research. In the strong interference electromagnetic environment of the city, the precise detection and fine imaging of underground space and underground structures face great technical challenges, and gradually rise to the level of future urban development and urban security strategy, becoming a technical problem that urgently needs to be solved and must be solved. The transient electromagnetic method is a geophysical detection technology based on the principle of electromagnetic induction and is widely used in the field of underground space detection. Compared with the ground penetrating radar method, it has the advantages of high working efficiency, large penetration depth and low detection cost. However, most of the current transient electromagnetic devices have problems such as poor primary magnetic field compensation effect and long emission current shut-off time.

[0003] Therefore, how to effectively weaken the coupling between the transmitting coil and the receiving coil and reduce the impact of current shutdown is a technical issue that needs to be solved urgently for achieving three-dimensional high-precision detection of urban underground space. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] Based on the above problems, the present disclosure provides a vehicle-mounted transient electromagnetic underground space detection system and method based on weak coupling of primary field to alleviate technical problems in most transient electromagnetic devices in the prior art, such as poor primary magnetic field compensation effect and long emission current shutdown time.

[0006] (II) Technical solution

[0007] One aspect of the present disclosure provides a vehicle-mounted transient electromagnetic underground space detection system based on primary field weak coupling, including: a transmitting subsystem, a transceiver coil subsystem, and a receiving subsystem.

[0008] The transmitting subsystem is configured to emit a current pulse signal of set frequency and amplitude;

[0009] The transceiver coil subsystem includes: a circular transmitting coil, two circular receiving coils, an x-component rectangular receiving coil, and a y-component rectangular receiving coil.

[0010] The circular transmitting coil is used to load the current pulse signal and then excite and generate a primary magnetic field signal. The primary magnetic field signal acts on the underground space and then generates a secondary magnetic field signal including underground target information. Two circular receiving coils are respectively arranged on the upper and lower sides of the transmitting coil, and are used to receive the z-component induction signal of the secondary magnetic field signal and offset the interference of the z-component induction signal of the primary magnetic field signal. The x-component rectangular receiving coil is arranged perpendicular to the plane where the transmitting coil is located, and is used to receive the x-component induction signal of the secondary magnetic field signal and eliminate the interference of the primary magnetic field signal. The y-component rectangular receiving coil is perpendicularly crossed with the x-component rectangular receiving coil and is arranged perpendicular to the plane where the transmitting coil is located, and is used to receive the y-component induction signal of the secondary magnetic field signal and eliminate the interference of the primary magnetic field signal.

[0011] The receiving subsystem is used to synchronously collect and process the x-component induction signal, y-component induction signal and z-component induction signal of the current pulse signal and the secondary magnetic field signal to obtain underground target detection information.

[0012] According to an embodiment of the present disclosure, the current pulse signal is a dual-frequency pulse signal, and the emission waveform of each cycle includes a large current low-frequency rectangular pulse and a small current high-frequency rectangular pulse.

[0013] According to an embodiment of the present disclosure, the two circular receiving coils have the same radius as the transmitting coil, the plane where the two circular receiving coils are located is parallel to the plane where the circular transmitting coil is located, and they are symmetrically arranged on the upper and lower sides of the transmitting coil.

[0014] According to an embodiment of the present disclosure, the transmitting subsystem includes: a DC-DC current conversion circuit, a transmitting system main control module, a main control drive module, a shutdown edge clamp circuit, a MOSFET inverter circuit, a damping circuit, and a current acquisition circuit; wherein:

[0015] The DC-DC current conversion circuit is connected to the DC power supply device to realize the DC power supply voltage conversion, and respectively power the main control module of the transmitting system, the main control drive module, and the MOSFET inverter circuit; the main control module of the transmitting system is the control center of the transmitting subsystem, which is used to receive the transmitting instruction and control the transmitting timing and the current pulse signal size, and realize the synchronization of the transmitting subsystem and the receiving subsystem in combination with the synchronization module; the main control drive module is controlled by the main control module of the transmitting system, and after the main control module provides the transmitting parameters, the MOSFET inverter circuit is controlled to generate a current pulse signal of a specific frequency and amplitude; the shutdown edge clamp circuit is controlled by the main control module of the transmitting system, and after the main control module provides the transmitting parameters , shaping the turn-off edge of the current pulse signal waveform generated by the MOSFET inverter circuit, improving the linearity of the turn-off edge and reducing the turn-off time; the MOSFET inverter circuit is used to generate a current pulse signal of set frequency and amplitude, and load it into the circular transmitting coil; the damping circuit is connected to the MOSFET inverter circuit, used to effectively absorb the high-order harmonics of the loop, prevent self-oscillation and protect the MOSFET inverter circuit; the current acquisition circuit includes a Hall device and a conditioning circuit, and the current acquisition circuit is used to realize signal conversion and conditioning of the current pulse signal; the synchronization module is connected to the transmitting subsystem and the receiving subsystem, and is used to realize synchronization between the transmitting subsystem and the receiving subsystem.

[0016] According to the embodiment of the present disclosure, the receiving subsystem includes: a DC-DC current conversion circuit, a receiving system main control module, an op amp, a preamplifier filter circuit module, and an ADC data acquisition circuit; wherein: the DC-DC current conversion circuit is connected to a DC power supply device to realize DC power supply voltage conversion, and supplies power to the receiving system main control module, the preamplifier filter circuit module, the ADC data acquisition circuit, and the data transmission module respectively; the receiving system main control module is the control center of the receiving subsystem, and is used to control the data acquisition, storage, and transmission operations of the receiving subsystem; the op amp is connected to two circular receiving coils to perform differential operations on the z-component sensing signals respectively input by the two circular receiving coils, so that the primary magnetic field interference in the sensing signals of the two receiving coils cancels each other, and obtains the z-component sensing signal of the secondary magnetic field signal. The ADC data acquisition circuit includes multiple channels, and after the receiving system main control module provides the acquisition parameters, the current pulse signal, and the amplified and filtered x-component sensing signal, y-component sensing signal, and z-component sensing signal are synchronously acquired.

[0017] The preamplifier filter circuit module includes: a first preamplifier filter circuit, a second preamplifier filter circuit, and a third preamplifier filter circuit.

[0018] The first preamplifier filter circuit is connected to the operational amplifier, and is used to amplify and filter the z-component induction signal of the secondary magnetic field signal; the second preamplifier filter circuit is connected to the x-component rectangular receiving coil, and is used to amplify and filter the x-component induction signal of the secondary magnetic field signal; the third preamplifier filter circuit is connected to the y-component rectangular receiving coil, and is used to amplify and filter the y-component induction signal of the secondary magnetic field signal.

[0019] According to an embodiment of the present disclosure, the detection system also includes: a data storage module and a data transmission module; wherein: the data storage module is used to store data; the data transmission module is used to transmit control instructions and data, and implement upload, download and deletion operations of control instructions and data.

[0020] According to the embodiment of the present disclosure, the detection system also includes: a non-metallic towing platform and a tractor.

[0021] The non-metal towed platform is used to carry the transceiver coil subsystem and the receiver subsystem;

[0022] The tractor is connected to the non-metallic towing platform through an articulated rod, and is used for carrying the launch subsystem and towing the non-metallic towing platform to travel on the detection line.

[0023] According to the embodiment of the present disclosure, the detection system also includes: a data monitoring center, which is arranged on the tractor and is configured to provide control instructions to the receiving subsystem and receive its feedback instructions. It can also realize real-time display, upload, and download operations of collected data of current pulse signals, x-component sensing signals, y-component sensing signals, and z-component sensing signals, thereby realizing remote human-computer interaction and remote monitoring of data.

[0024] Another aspect of the present disclosure provides a method for detecting underground space based on a primary magnetic field weak coupling vehicle-mounted transient electromagnetic method, which is detected by the above-mentioned detection system, and the detection method includes:

[0025] Operation S1: Sending a current pulse signal of set frequency and amplitude through the transmitting subsystem;

[0026] Operation S2: loading the current pulse signal into the circular transmitting coil to generate a primary magnetic field signal, and the primary magnetic field signal acts on the underground space to generate a secondary magnetic field signal including underground target information;

[0027] Operation S3: receiving the z-component induction signal of the secondary magnetic field signal through two circular receiving coils respectively and canceling the interference of the z-component induction signal of the primary magnetic field signal;

[0028] Operation S4: receiving the x-component induction signal of the secondary magnetic field signal through the x-component rectangular receiving coil and eliminating the interference of the primary magnetic field signal;

[0029] Operation S5: receiving the y-component induction signal of the secondary magnetic field signal through the y-component rectangular receiving coil and eliminating interference from the primary magnetic field signal; and

[0030] Operation S6: synchronously collecting and processing the current pulse signal, the x-component induction signal, the y-component induction signal, and the z-component induction signal of the secondary magnetic field signal through the receiving subsystem to obtain underground target detection information.

[0031] According to an embodiment of the present disclosure, in operation S3, after fixing two circular receiving coils on the upper and lower sides of the circular transmitting coil respectively, the position of the circular transmitting coil is adjusted up and down so that the amplitude of the z-component differential induction signal observed in real time is not greater than the amplitude of the system background noise, thereby determining the position of the transmitting coil; in operation S4, the x-component rectangular receiving coil is set perpendicular to the plane where the transmitting coil is located, and fine-tuning is performed so that the amplitude of the x-component differential induction signal observed in real time is not greater than the amplitude of the system background noise, thereby determining the position of the x-component rectangular receiving coil; in operation S5: the y-component rectangular receiving coil is perpendicularly crossed with the x-component rectangular receiving coil and is set perpendicular to the plane where the transmitting coil is located, and fine-tuning is performed so that the amplitude of the y-component differential induction signal observed in real time is not greater than the amplitude of the system background noise, thereby determining the position of the y-component rectangular receiving coil.

[0032] (III) Beneficial effects

[0033] It can be seen from the above technical solutions that the vehicle-mounted transient electromagnetic underground space detection system and method based on primary field weak coupling disclosed in the present invention has at least one or part of the following beneficial effects:

[0034] 1) The towed system structure is adopted. On the one hand, it isolates the electromagnetic interference caused by high-power current transmitting equipment to the coil system and improves the quality of the measurement signal; on the other hand, it is convenient to monitor the working status of the system during operation and improve the working efficiency of the system;

[0035] 2) The z-component differential measurement method is adopted to subtract the induction signals of the receiving coils symmetrically placed on the upper and lower sides to offset the primary magnetic field interference, and the pure secondary magnetic field can be obtained without any additional devices;

[0036] 3) The three-component (x component, y component, z component) receiving coil measurement method is adopted, which not only obtains the z component differential induction signal, but also can obtain the induction signals in the x and y directions at the same time, and the structure is simple; the measurement of multi-component induction signals provides technical support for realizing high-precision and high-resolution underground space detection;

[0037] 4) A dual-frequency transmission mode is adopted, in which the current amplitude of the large current low-frequency rectangular pulse is larger, which is suitable for depth measurement, but the shutdown time is longer and the shallow blind area is larger; the current amplitude of the small current high-frequency rectangular pulse is smaller, the shutdown time is shorter, and it has more shallow high-frequency information; combining the advantages of the two pulses can effectively reduce the impact of current shutdown and realize shallow-deep detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the overall structure of a vehicle-mounted transient electromagnetic underground space detection system based on primary field weak coupling according to an embodiment of the present disclosure;

[0039] Figure 2 is a schematic diagram of the composition architecture of a detection system according to an embodiment of the present disclosure;

[0040] Figure 3a It is a schematic diagram of the working process of a vehicle-mounted transient electromagnetic underground space detection method based on weak coupling of a primary magnetic field according to an embodiment of the present disclosure;

[0041] Figure 3b is a flow chart of a detection method according to an embodiment of the present disclosure;

[0042] Figure 4 A schematic diagram of a calibration process of a transceiver coil subsystem according to an embodiment of the present disclosure;

[0043] Figure 5a is a schematic diagram of a current pulse signal waveform according to an embodiment of the present disclosure;

[0044] Figure 5b for Figure 5a Schematic diagram of z-component differential induction signal waveform corresponding to the current pulse signal waveform shown;

[0045] Figure 6 It is a schematic diagram of the processing results of z-component data acquisition corresponding to a large current low-frequency rectangular pulse and a small current high-frequency rectangular pulse according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0046] The present disclosure provides a vehicle-mounted transient electromagnetic underground space detection system and method based on weak coupling of a primary field, which belongs to the field of time domain electromagnetic detection; most of the current transient electromagnetic devices have problems such as poor primary magnetic field compensation effect and long transmission current shut-off time. Due to the coupling between the transmitting coil and the receiving coil, the secondary magnetic field signal containing underground target information is often mixed with the primary magnetic field interference, and the primary magnetic field interference will undoubtedly cause the loss of shallow information, so that the detection result has a large shallow blind area; and the detection system provided by the present disclosure is mainly composed of a tractor and a non-metallic towing platform, the non-metallic towing platform is paved with a transmitting coil, and the three-component receiving coil includes a double z-component receiving coil, an x-component receiving coil and a y-component receiving coil arranged symmetrically up and down; the double z-component receiving coil is differentially operated by an op amp to eliminate the primary magnetic field coupling, and the x-component receiving coil and the y-component receiving coil are perpendicular to the transmitting coil to eliminate the primary magnetic field coupling, so as to realize the effective extraction of the three-component secondary magnetic field signal; the dual-frequency working mode can effectively combine the characteristics of deep detection depth of low-frequency large current and small shallow blind area of ​​high-frequency small current to realize three-dimensional high-precision detection of urban underground space.

[0047] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0048] In the embodiment of the present disclosure, Figure 1 and Figure 2 As shown, a vehicle-mounted transient electromagnetic underground space detection system based on a primary field weak coupling is provided, comprising:

[0049] A transmitting subsystem, configured to emit a current pulse signal of a set frequency and amplitude;

[0050] Transceiver coil subsystem, including:

[0051] A circular transmitting coil, used for loading the current pulse signal and then exciting and generating a primary magnetic field signal, wherein the primary magnetic field signal acts on the underground space and then generates a secondary magnetic field signal including underground target information;

[0052] Two circular receiving coils are respectively arranged at the upper and lower sides of the transmitting coil, and are used to receive the z-component induction signal of the secondary magnetic field signal and offset the interference of the z-component induction signal of the primary magnetic field signal;

[0053] an x-component rectangular receiving coil, arranged perpendicular to the plane where the transmitting coil is located, for receiving the x-component induction signal of the secondary magnetic field signal and eliminating interference from the primary magnetic field signal; and

[0054] a y-component rectangular receiving coil, perpendicularly intersecting the x-component rectangular receiving coil and arranged perpendicularly to the plane where the transmitting coil is located, for receiving the y-component induction signal of the secondary magnetic field signal and eliminating interference from the primary magnetic field signal; and

[0055] The receiving subsystem is used to synchronously collect and process the x-component induction signal, y-component induction signal and z-component induction signal of the current pulse signal and the secondary magnetic field signal to obtain underground target detection information.

[0056] The x component, y component, and z component mentioned above represent the magnetic field components in three directions of the electromagnetic field, or simply referred to as the three-component magnetic field. A coordinate system is established based on the direction of the three-component magnetic field, where the three-component magnetic field refers to two magnetic field components in the horizontal direction, such as the x component in the x-axis direction and the y component in the y-axis direction, and the z component in the z-axis direction perpendicular to the xy plane. The x component in the horizontal direction usually takes the direction of the measurement route of the system, while the y component takes the direction perpendicular to the x and z components.

[0057] According to an embodiment of the present disclosure, the transmitting coil is formed by overlapping copper wires into multiple turns of a circle, the radius of which is generally between 1 and 1.5 m. It is installed on a towing platform to load the current pulse signal generated by the transmitting subsystem and excite a magnetic field into the surrounding space.

[0058] According to the embodiments of the present disclosure, two circular receiving coils are wound by multiple turns of thin copper wires, and the radius is generally between 1 and 1.5 m. The performance parameters of the two circular receiving coils are exactly the same, and they are symmetrically placed on the upper and lower sides of the transmitting coil to measure the z-component induced signal, wherein the z-component receiving coil (upper) is located above the transmitting coil, and the z-component receiving coil (lower) is located below the transmitting coil. Since the primary magnetic field coupling generated by the transmitting coil inside the two receiving coils is exactly the same, the differential operation of the measurement signals of the two receiving coils is completed by the operational amplifier to offset the primary magnetic field, thereby realizing the measurement of the pure secondary magnetic field of the z-component. Among them, the vertical receiving distance between the transmitting coil and the two z-component circular receiving coils is 0.3 to 0.5 m, and the distance adjustment and correction work is realized by connecting the transmitting coil and the shaft rod of the two z-component circular receiving coils.

[0059] According to the embodiment of the present disclosure, the square receiving coil is also wound by multiple turns of thin copper wire, and the performance parameters of the two square receiving coils are exactly the same, and they are placed vertically and crosswise on the towing platform to measure the x and y component induced signals. Among them, the x and y component square receiving coils and the transmitting coils are perpendicular to each other to achieve the removal of the primary magnetic field coupling between the receiving coil and the transmitting coil.

[0060] Transmitting subsystem. This subsystem includes DC-DC current conversion circuit, transmitting system main control module, main control drive module, turn-off edge clamp circuit, MOSFET inverter circuit, damping circuit, current acquisition circuit and synchronization module.

[0061] According to an embodiment of the present disclosure, the DC-DC current conversion circuit is used to realize DC power supply voltage conversion, and to supply power to the main control module, the main control drive module and the MOSFET inverter circuit of the transmitting subsystem separately;

[0062] According to the embodiment of the present disclosure, the transmitting system main control module is the control center of the transmitting subsystem, which is used to receive the transmitting instruction and control the transmitting timing and the transmitting current, and realize the synchronization of the transmitting subsystem and the receiving subsystem in combination with the synchronization module;

[0063] According to an embodiment of the present disclosure, the main control driving module is controlled by the main control module of the transmitting system, and after the main control module provides the transmitting parameters, the main control driving module controls the MOSFET inverter circuit to generate a current pulse signal of a specific frequency and amplitude;

[0064] According to the embodiment of the present disclosure, the turn-off edge clamp circuit is controlled by the main control module of the transmitting system, and after the main control module provides the transmitting parameters, the turn-off edge of the current waveform generated by the MOSFET inverter circuit is shaped to improve the linearity of the turn-off edge and reduce the turn-off time;

[0065] According to an embodiment of the present disclosure, the MOSFET inverter circuit is used to generate a current pulse signal of a specific frequency and amplitude, and load it into the transmitting coil;

[0066] According to the embodiment of the present disclosure, the damping circuit is connected to the MOSFET inverter circuit, which can effectively absorb the high-order harmonics of the circuit, prevent the output circuit from generating self-oscillation, and protect the MOSFET inverter circuit;

[0067] According to an embodiment of the present disclosure, the current acquisition circuit is used to acquire a current pulse signal loaded into the transmitting coil;

[0068] According to an embodiment of the present disclosure, the synchronization module is connected to the transmitting system main control module and the receiving system main control module, and the transmitting system main control module synchronously controls the receiving system main control module to synchronously collect received data through the synchronization module when the transmitting subsystem starts working;

[0069] Receiving subsystem: This subsystem includes DC-DC current conversion circuit, receiving system main control module, operational amplifier, preamplifier filter circuit, ADC data acquisition circuit, data storage module, and data transmission module.

[0070] According to the embodiment of the present disclosure, the DC-DC current conversion circuit is used to realize DC power supply voltage conversion, and separately supplies power to the main control module, preamplifier filter circuit, ADC data acquisition circuit and data transmission module of the receiving subsystem;

[0071] According to the embodiment of the present disclosure, the receiving system main control module is the control center of the receiving subsystem, which is used to receive the synchronization instructions of the transmitting subsystem, and receive the receiving instructions of the data monitoring center through the data transmission unit, and control the collection, storage and transmission operations of the receiving subsystem;

[0072] According to an embodiment of the present disclosure, the operational amplifier is used to perform differential operation on the input upper and lower z-component receiving coil induction signals, so that the primary magnetic field interferences in the two receiving coil induction signals cancel each other out;

[0073] According to an embodiment of the present disclosure, the preamplifier filter circuit has three channels, namely, a first preamplifier filter circuit, a second preamplifier filter circuit and a third preamplifier filter circuit, which respectively amplify and filter the received z-component differential sensing signal, x-component sensing signal and y-component sensing signal;

[0074] According to the embodiment of the present disclosure, the ADC data acquisition circuit has multiple channels, and after the main control module provides acquisition parameters, the emission current signal and the amplified and filtered three-component sensing signal are synchronously and accurately acquired;

[0075] According to an embodiment of the present disclosure, the data storage module is used to store the collected data to prevent data loss;

[0076] According to an embodiment of the present disclosure, the data transmission module is used to transmit control instructions and data, and implement operations such as uploading, downloading and deleting control instructions and data;

[0077] According to an embodiment of the present disclosure, the system further comprises: a GPS positioning system, a DC power supply device, a data monitoring center, a tractor, a non-metallic towing platform, an articulated rod, and a wiring harness tube;

[0078] The GPS positioning system is installed on the non-metallic towing platform to record the geographical location information of the detection system;

[0079] The DC power supply device is placed on the tractor to provide external DC power for the transmitting and receiving subsystems;

[0080] The data monitoring center is located on the tractor. The driver can provide control instructions to the receiving subsystem through the data monitoring center and receive its feedback instructions, thus realizing remote human-computer interaction of the detection system. In addition, the data monitoring center can also realize real-time display and upload and download of the emission current and three-component sensing signal acquisition data, thereby realizing remote monitoring of the data;

[0081] The tractor is manually driven, carries electromagnetic instruments such as a transmitting subsystem, a DC power supply device and a data monitoring center, and is connected to a non-metallic towing platform via an articulated rod to travel on a pre-planned measurement route;

[0082] The non-metal towing platform has no power device, carries the transceiver coil subsystem and the receiving subsystem, is connected to the tractor through an articulated rod, and is provided with forward power by the tractor;

[0083] The articulated rod is used to connect the tractor and the non-metal towing platform to control the forward direction of the latter;

[0084] The wire harness tube is fixed between the tractor and the non-metal towing platform and is used for bundling the connecting wires of the electromagnetic devices between the two platforms.

[0085] The present disclosure also provides a method for detecting underground space based on a weak coupling vehicle-mounted transient electromagnetic field, which detects underground space and detection targets through the above-mentioned detection system. Figure 3a , Figure 3b , Figure 4 As shown, the detection method includes:

[0086] Operation S1: Sending a current pulse signal of set frequency and amplitude through the transmitting subsystem;

[0087] Operation S2: loading the current pulse signal into the circular transmitting coil to generate a primary magnetic field signal, and the primary magnetic field signal acts on the underground space to generate a secondary magnetic field signal including underground target information;

[0088] Operation S3: receiving the z-component induction signal of the secondary magnetic field signal through two circular receiving coils respectively and canceling the interference of the z-component induction signal of the primary magnetic field signal;

[0089] Operation S4: receiving the x-component induction signal of the secondary magnetic field signal through the x-component rectangular receiving coil and eliminating the interference of the primary magnetic field signal;

[0090] Operation S5: receiving the y-component induction signal of the secondary magnetic field signal through the y-component rectangular receiving coil and eliminating interference from the primary magnetic field signal; and

[0091] Operation S6: synchronously collecting and processing the current pulse signal, the x-component induction signal, the y-component induction signal, and the z-component induction signal of the secondary magnetic field signal through the receiving subsystem to obtain underground target detection information.

[0092] In the embodiments of the present disclosure, Figure 3a As shown, when conducting detection work, the system layout and self-check should be carried out first. The transmitting coil and the three-component receiving coil are laid on the non-metallic towing platform. The transmitting coil is horizontally installed on a horizontal plane with a vertical height of 0.3 to 0.5m from the plane of the towing platform. The two circular z-component receiving coils are horizontally and symmetrically installed on the upper and lower sides of the transmitting coil respectively. The lower z-component receiving coil is directly laid on the surface of the towing platform. The two square x- and y-component receiving coils are vertically crossed inside the cylindrical space formed by the two z-component receiving coils, and the x- and y-component square receiving coils are perpendicular to each other with the transmitting coil. In addition, the receiving subsystem is also fixed on the towing platform, and other electromagnetic instruments such as the transmitting subsystem and DC power supply equipment are placed on the tractor; finally, complete the self-check of each subsystem, eliminate possible faults, and ensure the smooth progress of the detection operation;

[0093] Furthermore, if combined Figure 3a and Figure 4 As shown, the relative position correction of the transceiver coil subsystem is performed. The relative position of the transmitting coil and the three-component receiving coil is adjusted to improve the primary magnetic field compensation effect of the three-component receiving coil and determine the optimal position of the transceiver coil; the details are as follows:

[0094] A 1kHz, 1A sinusoidal current pulse is loaded, and the data received by the data monitoring center is observed in real time to determine the primary magnetic field compensation effect of the three-component receiving coil, and adjust the relative positions of the transmitting and receiving coils.

[0095] Furthermore, the relative positions of the z-component receiving coil and the transmitting coil are adjusted. The z-component receiving coils on the upper and lower sides are fixed, and the transmitting coil is slowly moved up and down. The amplitude of the z-component differential induction signal received is observed in real time by the data monitoring center to see whether it is greater than the system background noise amplitude. If it is not greater than the system background noise, it means that the primary magnetic field compensation effect is good enough, and the position of the transmitting coil is directly fixed; if the amplitude of the received signal is greater than the system background noise amplitude, it means that there is a large residual magnetic field interference, and the transmitting coil is slowly moved upward from the initial position. If the amplitude of the received signal continues to decrease, it continues to move upward until the amplitude of the received signal reaches the minimum, and the position of the transmitting coil is fixed; on the contrary, if the amplitude of the received signal continues to increase, the transmitting coil is changed to move downward until the amplitude of the received signal reaches the minimum, and the position of the transmitting coil is fixed.

[0096] Furthermore, the relative positions of the x-component receiving coil and the transmitting coil are adjusted. After the transmitting coil position is corrected and kept stationary, the x-component receiving coil is slightly flipped left and right, and the received x-component induction signal amplitude is observed in real time by the data monitoring center to see whether it is greater than the system background noise amplitude. If it is not greater than the system background noise, it means that the primary magnetic field compensation effect is good enough, and the position of the x-component receiving coil is directly fixed; if the received signal amplitude is greater than the system background noise amplitude, it means that there is a large residual magnetic field interference, and the x-component receiving coil is slightly flipped to the left from the initial position. If the received signal amplitude continues to decrease, it continues to be slightly flipped to the left until the received signal amplitude reaches the minimum, and the position of the x-component receiving coil is fixed; on the contrary, if the received signal amplitude continues to increase, the x-component receiving coil is changed to be slightly flipped to the right until the received signal amplitude reaches the minimum, and the position of the x-component receiving coil is fixed.

[0097] Furthermore, similarly, the position of the y-component receiving coil is corrected according to the x-component receiving coil position adjustment method. After the transmitting coil position is corrected and kept unchanged, the y-component receiving coil is slightly flipped left and right. The data monitoring center is used to observe in real time whether the amplitude of the received y-component induction signal is greater than the system background noise amplitude. If it is not greater than the system background noise, it means that the primary magnetic field compensation effect is good enough, and the position of the y-component receiving coil is directly fixed; if the received signal amplitude is greater than the system background noise amplitude, it means that there is a large residual primary magnetic field interference, and the y-component receiving coil is slightly flipped to the left from the initial position. If the received signal amplitude continues to decrease, it continues to be slightly flipped to the left until the received signal amplitude reaches the minimum, and the position of the y-component receiving coil is fixed; on the contrary, if the received signal amplitude continues to increase, the y-component receiving coil is changed to be slightly flipped to the right until the received signal amplitude reaches the minimum, and the position of the y-component receiving coil is fixed.

[0098] Furthermore, the emission and sampling parameters of the detection system are set. The emission subsystem is in dual-frequency emission mode, that is, the waveform of each emission cycle consists of a series of high-current low-frequency rectangular pulses and a series of low-current high-frequency rectangular pulses, see Figure 5a and Figure 5b The current amplitude of the large current low-frequency rectangular pulse is larger, which is suitable for depth measurement, but the shutdown time is longer and the shallow blind area is larger; the current amplitude of the small current high-frequency rectangular pulse is smaller, the shutdown time is shorter, and it has more shallow high-frequency information. Combining the advantages of the two pulses can effectively reduce the impact of current shutdown and achieve shallow-deep detection. The sampling rate of the receiving subsystem is set at about 1MHz, which can achieve high-precision synchronous acquisition of the transmitting current and the three-component sensing signal;

[0099] Furthermore, system operation and data collection: the driver issues instructions through the data monitoring center, the transmitting and receiving systems work synchronously, and are connected to the GPS positioning system. Under the guidance of the tractor, the towing platform operates on the pre-planned measurement route. At the same time, the transmitting current and three-component sensing signals are collected, and displayed and stored in real time.

[0100] Further, comprehensive data processing and analysis: After the detection is completed, the collected data is imported into the MATLAB data processing platform for data processing and analysis. Taking the z component sensing signal as an example, Figure 6 As shown in the figure, the solid line and the dotted line correspond to the high-frequency and low-frequency modes respectively. The current amplitude of the large current low-frequency rectangular pulse is larger, and later response data can be measured, but the shutdown time is longer, which will lose some early data and cause shallow blind areas; the small current high-frequency rectangular pulse has a shorter shutdown time and can measure earlier response data, but the signal-to-noise ratio is poor and deep formation information cannot be obtained. Combining the advantages of the two current pulses can effectively reduce the impact of current shutdown. Subsequently, resistivity inversion imaging is used to realize the joint data interpretation of the dual-frequency transmission mode to obtain high-precision shallow-deep geophysical data.

[0101] So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0102] Based on the above description, those skilled in the art should have a clear understanding of the vehicle-mounted transient electromagnetic underground space detection system and method based on weak coupling of primary magnetic field disclosed in the present invention.

[0103] In summary, the present disclosure provides a vehicle-mounted transient electromagnetic underground space detection system and method based on weak coupling of a primary field, which adopts a towed system structure. On the one hand, the electromagnetic interference caused by high-power current transmitting equipment to the coil system is isolated, and the quality of the measurement signal is improved; on the other hand, it is convenient to monitor the working state of the system when the system is operating, and improve the working efficiency of the system. A unique method of ground z-component differential measurement is adopted, so that the induction signals of the receiving coils symmetrically placed on the upper and lower sides are subtracted to offset the primary magnetic field interference, and a pure secondary magnetic field can be obtained without other additional devices; a three-component receiving coil measurement method is adopted, which not only obtains the z-component differential induction signal, but also can obtain the induction signals in the x and y directions at the same time, and the structure is simple. The measurement of multi-component induction signals provides technical support for realizing high-precision and high-resolution underground space detection; a dual-frequency transmission mode is adopted. The current amplitude of a large current low-frequency rectangular pulse is larger, which is suitable for depth measurement, but the off time is longer and the shallow blind area is larger; the current amplitude of a small current high-frequency rectangular pulse is smaller, the off time is shorter, and it has more shallow high-frequency information. Combining the advantages of the two pulses can effectively reduce the impact of current shutdown and achieve both shallow and deep detection.

[0104] It should also be noted that the above are different embodiments provided by the present disclosure. These embodiments are used to illustrate the technical content of the present disclosure, rather than to limit the scope of protection of the present disclosure. A feature of an embodiment can be applied to other embodiments through appropriate modification, replacement, combination, and separation.

[0105] It should be noted that, in this document, unless otherwise specified, “a” element is not limited to a single element, but may include one or more elements.

[0106] In addition, in this document, unless otherwise specified, ordinal numbers such as "first" and "second" are only used to distinguish multiple components with the same name, and do not indicate that there is a hierarchy, level, execution order, or process order between them. A "first" component and a "second" component may appear together in the same component, or appear in different components. The presence of a component with a larger ordinal number does not necessarily indicate the presence of another component with a smaller ordinal number.

[0107] In this document, unless otherwise specified, the so-called feature A "or" or "and / or" (and / or) feature B means that A exists alone, B exists alone, or A and B exist at the same time; the so-called feature A "and" (and) or "and" (and) or "and" (and) feature B means that A and B exist at the same time; the so-called "includes", "comprising", "has" and "containing" mean including but not limited to these.

[0108] In addition, in this document, the terms "upper", "lower", "left", "right", "front", "back", or "between" are only used to describe the relative positions between multiple elements, and can be extended to include translation, rotation, or mirroring. In addition, in this document, unless otherwise specified, "an element is on another element" or similar descriptions do not necessarily mean that the element contacts the other element.

[0109] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0110] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A primary magnetic field weak coupling vehicle-mounted transient electromagnetic underground space detection system, comprising: The transmitting subsystem is configured to emit a current pulse signal of a set frequency and amplitude, wherein the current pulse signal is a dual-frequency pulse signal, and the transmitting waveform of each cycle includes a large current low-frequency rectangular pulse and a small current high-frequency rectangular pulse; Transceiver coil subsystem, including: A circular transmitting coil, used for loading the current pulse signal and then exciting to generate a primary magnetic field signal, wherein the primary magnetic field signal acts on the underground space and then generates a secondary magnetic field signal including underground target information; Two circular receiving coils are respectively arranged at the upper and lower sides of the transmitting coil, and are used to receive the z-component induction signal of the secondary magnetic field signal and offset the interference of the z-component induction signal of the primary magnetic field signal; an x-component rectangular receiving coil, arranged perpendicular to the plane where the transmitting coil is located, for receiving the x-component induction signal of the secondary magnetic field signal and eliminating interference from the primary magnetic field signal; and a y-component rectangular receiving coil, perpendicularly intersecting the x-component rectangular receiving coil and arranged perpendicularly to the plane where the transmitting coil is located, for receiving the y-component induction signal of the secondary magnetic field signal and eliminating interference from the primary magnetic field signal; and A receiving subsystem, used for synchronously collecting and processing the x-component induction signal, y-component induction signal, and z-component induction signal of the current pulse signal and the secondary magnetic field signal to obtain underground target detection information; The transmitting subsystem includes: a DC-DC current conversion circuit, a transmitting system main control module, a main control drive module, a turn-off edge clamp circuit, a MOSFET inverter circuit, a damping circuit, and a current acquisition circuit; wherein: the DC-DC current conversion circuit is connected to a DC power supply device to realize DC power supply voltage conversion, and respectively power the transmitting system main control module, the main control drive module, and the MOSFET inverter circuit; the transmitting system main control module is the control center of the transmitting subsystem, and is used to receive transmitting instructions and control the transmitting timing and the size of the current pulse signal, and realize the synchronization of the transmitting subsystem and the receiving subsystem in combination with the synchronization module; the main control drive module is controlled by the transmitting system main control module, and after the main control module provides the transmitting parameters, it controls the MOSFET inverter circuit to generate current pulses of specific frequency and amplitude signal; the turn-off edge clamp circuit is controlled by the main control module of the transmitting system. After the main control module provides the transmitting parameters, the turn-off edge of the current pulse signal waveform generated by the MOSFET inverter circuit is shaped to improve the linearity of the turn-off edge and reduce the turn-off time; the MOSFET inverter circuit is used to generate a current pulse signal of set frequency and amplitude, and load it into the circular transmitting coil; the damping circuit is connected to the MOSFET inverter circuit to effectively absorb the high-order harmonics of the loop, prevent self-oscillation and protect the MOSFET inverter circuit; the current acquisition circuit includes a Hall device and a conditioning circuit, and the current acquisition circuit is used to realize signal conversion and conditioning of the current pulse signal; the synchronization module is connected to the transmitting subsystem and the receiving subsystem to realize synchronization of the transmitting subsystem and the receiving subsystem; The receiving subsystem includes: a DC-DC current conversion circuit, a receiving system main control module, an operational amplifier, a preamplifier filter circuit module, and an ADC data acquisition circuit; wherein: the DC-DC current conversion circuit is connected to a DC power supply device to realize DC power supply voltage conversion, and supplies power to the receiving system main control module, the preamplifier filter circuit module, the ADC data acquisition circuit, and the data transmission module respectively; the receiving system main control module is the control center of the receiving subsystem, and is used to control the data acquisition, storage, and transmission operations of the receiving subsystem; the operational amplifier is connected to two circular receiving coils, and is used to perform differential operations on the z-component induction signals respectively input by the two circular receiving coils, so that the primary magnetic field interference in the induction signals of the two receiving coils cancels each other, and a secondary magnetic field is obtained The preamplifier filter circuit module comprises: a first preamplifier filter circuit connected to the operational amplifier for amplifying and filtering the z-component induction signal of the secondary magnetic field signal; a second preamplifier filter circuit connected to the x-component rectangular receiving coil for amplifying and filtering the x-component induction signal of the secondary magnetic field signal; and a third preamplifier filter circuit connected to the y-component rectangular receiving coil for amplifying and filtering the y-component induction signal of the secondary magnetic field signal; the ADC data acquisition circuit comprises a plurality of channels, and after the receiving system main control module provides the acquisition parameters, the current pulse signal, and the amplified and filtered x-component induction signal, y-component induction signal, and z-component induction signal are synchronously acquired.

2. According to the detection system of claim 1, the two circular receiving coils have the same radius as the transmitting coil, the plane where the two circular receiving coils are located is parallel to the plane where the circular transmitting coil is located, and they are symmetrically arranged on the upper and lower sides of the transmitting coil.

3. The detection system according to claim 1, further comprising: Data storage module, data transmission module; wherein: The data storage module is used to store data; The data transmission module is used to transmit control instructions and data, and implement upload, download and delete operations of control instructions and data.

4. The detection system according to claim 1, further comprising: A non-metal towed platform used to carry the transceiver coil subsystem and the receiver subsystem; The tractor is connected to the non-metallic towing platform via an articulated rod, and is used for carrying the launch subsystem and towing the non-metallic towing platform to move along the detection route.

5. The detection system according to claim 4, further comprising: The data monitoring center is installed on the tractor and is configured to provide control instructions to the receiving subsystem and receive its feedback instructions, so as to realize the real-time display, upload and download operations of the collected data of the current pulse signal, the x-component sensing signal, the y-component sensing signal and the z-component sensing signal, thereby realizing remote human-computer interaction and remote monitoring of data.

6. A method for detecting underground space based on a primary magnetic field weak coupling vehicle-mounted transient electromagnetic, which is detected by the detection system according to any one of claims 1 to 5, and the detection method comprises: Operation S1: Sending a current pulse signal of set frequency and amplitude through the transmitting subsystem; Operation S2: loading the current pulse signal into the circular transmitting coil to generate a primary magnetic field signal, and the primary magnetic field signal acts on the underground space to generate a secondary magnetic field signal including underground target information; Operation S3: receiving the z-component induction signal of the secondary magnetic field signal through two circular receiving coils respectively and canceling the interference of the z-component induction signal of the primary magnetic field signal; Operation S4: receiving the x-component induction signal of the secondary magnetic field signal through the x-component rectangular receiving coil and eliminating the interference of the primary magnetic field signal; Operation S5: receiving the y-component induction signal of the secondary magnetic field signal through the y-component rectangular receiving coil and eliminating interference from the primary magnetic field signal; and Operation S6: synchronously collecting and processing the current pulse signal, the x-component induction signal, the y-component induction signal, and the z-component induction signal of the secondary magnetic field signal through the receiving subsystem to obtain underground target detection information.

7. The detection method according to claim 6, wherein: In operation S3, after fixing the two circular receiving coils at the upper and lower sides of the circular transmitting coil respectively, the position of the circular transmitting coil is adjusted up and down so that the amplitude of the z-component differential induction signal observed in real time is not greater than the amplitude of the system background noise, thereby determining the position of the transmitting coil; In operation S4, the x-component rectangular receiving coil is arranged perpendicular to the plane where the transmitting coil is located, and fine-tuned so that the amplitude of the x-component differential induction signal observed in real time is not greater than the amplitude of the system background noise, thereby determining the position of the x-component rectangular receiving coil; In operation S5: the y-component rectangular receiving coil is perpendicularly crossed with the x-component rectangular receiving coil and is arranged perpendicular to the plane where the transmitting coil is located, and fine-tuned so that the amplitude of the y-component differential induction signal observed in real time is not greater than the system background noise amplitude, thereby determining the position of the y-component rectangular receiving coil.

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