Pull-type transient electromagnetic detection device and detection method based on multi-magnetic moment emission

Abstract

The invention discloses a towed transient electromagnetic detection device and detection method based on multi-magnetic moment emission, and belongs to the technical field of geophysical electromagnetic detection.The transient electromagnetic detection device comprises a main control module, an upper computer, an emission system, a receiving system, a multi-path power supply module, a clamping module, a damping module, a PWM driving module and a current sensor; the multi-path power supply module is controlled to work in a time-sharing mode through time-sharing control over the state of a switch, multi-magnetic-moment pulse waves are emitted in a single period, a high-voltage active double-constant-voltage clamping circuit is adopted, the rising and falling time of emission current is optimized, the detection blind area of the transient electromagnetic detection device is reduced, and the detection efficiency is improved. Through a multi-path power supply module parallel control technology, the energy consumption and the heating value of the transient electromagnetic detection device are reduced, and the detection precision and the stability of the electromagnetic detection device are improved. According to the detection method, through the multi-magnetic-moment emission technology, the geological detection requirements of the deep layer and the shallow layer can be effectively considered, and the detection efficiency and the system stability are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of geophysical electromagnetic detection technology, specifically, it relates to a towed transient electromagnetic detection device and detection method based on multi-magnetic moment emission. Background Technology

[0002] With rapid economic development and accelerating urbanization, land resources are becoming increasingly scarce, making the development and utilization of urban underground space an inevitable trend. Against this backdrop, efficient and accurate underground space exploration technologies are particularly important. Electromagnetic methods, as one of the mainstream geophysical exploration technologies, especially the towed transient electromagnetic detection method, have demonstrated significant application value in urban underground space exploration due to their advantages such as large detection depth, wide coverage, and ease of operation.

[0003] However, traditional towed transient electromagnetic systems still face numerous technical bottlenecks in practical applications: First, limited by circuit structure design and the resistive-inductive characteristics of the transmitting coil, most existing systems exhibit single-magnetic-moment waveforms with relatively small peak currents, resulting in insufficient excitation energy for deep geological bodies and weak electromagnetic response signals; second, the poor quality of the rising and falling waveforms of the transmitting current not only affects the time-frequency characteristics of the signal but also leads to a significant shallow detection blind zone; third, existing equipment generally has limited functionality, often requiring frequent equipment replacements to achieve geological exploration at different depths, severely restricting detection efficiency; furthermore, the system generates significant heat during operation, affecting equipment stability and limiting the ability to operate continuously for extended periods.

[0004] These issues collectively make it difficult for existing towed transient electromagnetic systems to achieve comprehensive, multi-depth, and high-precision detection in complex urban environments, failing to meet the higher demands placed on detection technology by current urban underground space development and utilization. Therefore, it is urgent to overcome the limitations of existing technologies through innovative circuit structures and system designs, and to develop a towed transient electromagnetic system that can handle both deep and shallow layer detection, and possesses higher efficiency and better stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a towed transient electromagnetic detection device based on multi-magnetic moment emission, and a corresponding detection method. This transient electromagnetic detection device and method, through multi-magnetic moment emission technology, effectively addresses the geological exploration needs of both deep and shallow layers, significantly improving detection efficiency and system stability.

[0006] The objective of this invention is achieved through the following technical solution: According to a first aspect of the present invention, a towed transient electromagnetic detection device based on multi-magnetic-moment emission is proposed, comprising: a main control module, a host computer, a transmitting system, a receiving system, a multi-channel power supply module, a clamping module, a damping module, a PWM drive module, and a current sensor. The host computer is communicatively connected to the main control module and is used to send control parameters and receive acquired data. The transmitting system includes a transmitting coil and an H-bridge transmitting module, the H-bridge transmitting module being electrically connected to the transmitting coil and used to drive the transmitting coil to operate. The receiving system includes a receiving coil, a preamplifier, and an A / D acquisition module, wherein the receiving coil is sequentially... The power supply module is connected to the main control module via a preamplifier and an A / D acquisition module; the multi-channel power supply module includes a DC-DC boost module, a DC-DC buck-boost adjustment module, and a DC-DC buck module. The DC-DC boost module is connected in parallel with a capacitor and is connected to the H-bridge transmitter module in sequence via a first switch and a first protection diode; the DC-DC buck-boost adjustment module is connected to the H-bridge transmitter module in sequence via a second switch and a second protection diode; the DC-DC buck module is connected to the H-bridge transmitter module via a third protection diode; the clamping module includes a clamping capacitor bank and a DC-DC high-voltage clamping module. The DC-DC high-voltage clamping modules are connected in parallel, with their first connection point connected to the H-bridge transmitter module via a fourth switch, and their second connection point grounded. The fourth switch controls whether the clamping capacitor bank and the DC-DC high-voltage clamping module are connected to the H-bridge transmitter module. The damping module includes a damping resistor and a third switch. The damping resistor is connected in parallel across the transmitter coil via the third switch, thus controlling its connection to the transmitter coil. Normally, the transmitter coil is underdamped due to parasitic inductance and distributed capacitance when energized. Connecting the damping resistor in parallel across the transmitter coil can transform it into a critically damped state, thereby improving the transmitted waveform. The PWM drive module has an input terminal connected to the main control module and an output terminal connected to the H-bridge transmitter module, used to drive the H-bridge transmitter module according to the control signal of the main control module; the current sensor is connected to the main control module, used to monitor the current waveform of the transmitter coil in real time and feed the monitoring result back to the main control module; wherein the main control module is configured to switch the working state of the multi-channel power supply module and the clamping module in a time-division manner by controlling the closing or opening of the first switch, the second switch, the third switch and the fourth switch, so as to generate multiple magnetic moment pulse waveforms with different peak currents in a single transmission cycle.

[0007] Furthermore, the towed transient electromagnetic detection device based on multi-magnetic-moment emission also includes a power supply, a mobile platform, and a tow vehicle. The power supply is connected to the main control module and is used to power the entire transient electromagnetic detection device. The mobile platform is used to carry the transmitting coil and the receiving coil. The tow vehicle is used to tow the mobile platform.

[0008] Furthermore, the H-bridge transmitting module includes a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes a first transistor and a second transistor connected in series, and the second half-bridge branch includes a third transistor and a fourth transistor connected in series. The series connection node of the first transistor and the second transistor is connected to one end of the transmitting coil, and the series connection node of the third transistor and the fourth transistor is connected to the other end of the transmitting coil. The common terminal of the first transistor and the third transistor is connected to the first protection diode, the second protection diode, the third protection diode, and the fourth switch. The common terminal of the second transistor and the fourth transistor is grounded.

[0009] Furthermore, the DC-DC buck-boost adjustment module has two working modes: boost and buck, which are controlled by the main control module to switch between according to the launch stage.

[0010] According to a second aspect of the present invention, a towed transient electromagnetic detection method based on multi-magnetic moment emission is proposed. This method employs the aforementioned towed transient electromagnetic detection device based on multi-magnetic moment emission for detection. The method includes: Step S1: Input control parameters to the main control module via the host computer. The control parameters include the output voltage of the multi-power supply module, the transmission frequency, and the number of transmission cycles. Step S2: The main control module adjusts the output voltage and transmission waveform parameters of the DC-DC boost module, DC-DC buck-boost adjustment module, and DC-DC buck module according to the control parameters. Step S3: The main control module controls the closing or opening of the first switch, the second switch and the fourth switch in a time-sharing manner, so that the multi-channel power supply module and the clamping module work in a time-sharing manner, and sequentially generate multiple magnetic moment pulses with different peak currents within a single transmission cycle; Step S4: During the current rise and turn-off phases, the clamping module is connected to the circuit by closing the fourth switch to perform voltage clamping, thereby optimizing the current rise and turn-off speeds. Step S5: At the end of the emission current turn-off period, the damping resistor is connected to the circuit by closing the third switch to absorb residual energy and suppress current oscillation; Step S6: The secondary field signal is acquired by the receiving system and transmitted to the main control module for processing via the A / D acquisition module.

[0011] Furthermore, in step S3, the multiple magnetic moment pulses with different peak currents include a first magnetic moment pulse, a second magnetic moment pulse, a third magnetic moment pulse, and a fourth magnetic moment pulse, with their peak currents decreasing sequentially, corresponding to deep, medium-deep, medium-shallow, and shallow geological exploration, respectively.

[0012] Furthermore, in step S3, the time-sharing control includes: During the first magnetic moment pulse emission phase, the first and fourth switches are closed, and power is supplied by the DC-DC boost module and the capacitor. During the second magnetic moment pulse emission phase, the second and fourth switches are closed, and the DC-DC buck-boost regulator module operates in boost mode to supply power. During the third magnetic moment pulse emission phase, the second switch is closed, and the DC-DC buck-boost regulator module operates in buck mode to provide power. During the fourth magnetic moment pulse emission phase, the first, second, and fourth switches are disconnected, and power is supplied by the DC-DC step-down module.

[0013] Furthermore, in step S4, the voltage clamping includes active constant voltage clamping achieved through a DC-DC high voltage clamping module and a clamping capacitor bank during the current rise phase and the turn-off phase.

[0014] Through the above design scheme, the beneficial effects of this invention compared with the prior art are as follows: First, this invention controls the switching state in a time-sharing manner, thereby controlling the multi-power supply modules to work in a time-sharing manner, realizing the emission of multiple magnetic moment pulse waves in a single cycle, that is, the emission of emission currents of different magnitudes, achieving the effect of simultaneous detection of shallow, mid-shallow, mid-deep and deep layers, and achieving full coverage of the detection range, solving the problem that traditional towed transient electromagnetic systems cannot detect both shallow and deep layers. Second, the present invention uses a high-voltage active dual constant voltage clamping circuit to optimize the rise and fall time of the transmission current. The rapid rise and rapid turn-off of the transmission current is an important indicator for measuring the efficiency of an electromagnetic detection device. Optimizing the rise and fall time can reduce the detection blind zone of the transient electromagnetic detection device and improve the detection efficiency. Third, by using parallel control technology for multiple power supply modules, the energy consumption and heat generation of transient electromagnetic detection devices are reduced, solving the problems of high power consumption and heat generation in traditional towed transient electromagnetic systems, and improving the detection accuracy and stability of electromagnetic detection devices. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of this application. The illustrative embodiments and descriptions of the invention are used to understand the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a circuit diagram of a towed transient electromagnetic detection device based on multi-magnetic-moment emission in an embodiment of the present invention. Figure 2 This is an overall schematic block diagram of the towed transient electromagnetic detection device based on multi-magnetic-moment emission in an embodiment of the present invention; Figure 3 This is a schematic flowchart illustrating the system operation of the towed transient electromagnetic detection method based on multi-magnetic-moment emission in an embodiment of the present invention. Figure 4 This is a timing diagram of the towed transient electromagnetic detection method based on multi-magnetic-moment emission in an embodiment of the present invention. Figure 5 This is a simulated current output waveform diagram of the towed transient electromagnetic detection device based on multi-magnetic moment emission in an embodiment of the present invention; Figure 6 The simulated current output waveform of a traditional single magnetic moment emission detection device; Figure 7 The current rise waveform of the dragged transient electromagnetic detection device based on multi-magnetic moment emission of the present invention is shown in the figure. Figure 8 The waveform of current rise in a traditional single magnetic moment emission detection device; Figure 9 The waveform of the tail current when the current is turned off in a towed transient electromagnetic detection device based on multi-magnetic moment emission. Figure 10 The waveform of the tail current when a traditional single magnetic moment emission detection device is turned off; In the diagram: 1-Main control module; 2-Host computer; 3-Power supply; 4-DC-DC boost module; 5-DC-DC buck-boost adjustment module; 6-DC-DC buck module; 7-First switch; 8-Second switch; 9-First protection diode; 10-Second protection diode; 11-Third protection diode; 12-Capacitor; 13-Third switch; 14-Fourth switch; 15-Clamping capacitor bank; 16-PWM drive module; 17-H-bridge transmitter module; 18-Current sensor; 19-Transmitting coil; 20-DC-DC high-voltage clamping module; 21-Damping resistor; 22-A / D acquisition module; 23-Preamplifier; 24-Receiver coil; 25-Mobile platform; 26-Trailer; Q1-First transistor; Q2-Second transistor; Q3-Third transistor; Q4-Fourth transistor. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] See Figure 1 and Figure 2This invention provides a towed transient electromagnetic detection device based on multi-magnetic moment emission. The transient electromagnetic detection device includes a main control module 1, a host computer 2, a power supply 3, a DC-DC boost module 4, a DC-DC boost / buck adjustment module 5, a DC-DC buck module 6, a first switch 7, a second switch 8, a first protection diode 9, a second protection diode 10, a third protection diode 11, a capacitor 12, a third switch 13, a fourth switch 14, a clamping capacitor bank 15, a PWM drive module 16, an H-bridge transmitting module 17, a current sensor 18, a transmitting coil 19, a DC-DC high-voltage clamping module 20, a damping resistor 21, an A / D acquisition module 22, a preamplifier 23, a receiving coil 24, a moving platform 25, and a tow vehicle 26.

[0018] The main control module 1 is connected to the host computer 2, power supply 3, DC-DC boost module 4, DC-DC buck-boost adjustment module 5, DC-DC buck module 6, first switch 7, second switch 8, third switch 13, fourth switch 14, H-bridge transmitter module 17, current sensor 18, DC-DC high-voltage clamping module 20, and A / D acquisition module 22. The PWM drive module 16 is connected to the transmitting coil 19 via the H-bridge transmitter module 17. The first switch 7 is connected to the first protection diode 9, the second switch 8 is connected to the second protection diode 10, the DC-DC buck module 6 is connected to the third protection diode 11, the first protection diode 9 is connected to the clamping module via the H-bridge transmitter module 17 and the fourth switch 14, the second protection diode 10 is connected to the clamping module via the H-bridge transmitter module 17 and the fourth switch 14, the third protection diode 11 is connected to the clamping module via the H-bridge transmitter module 17 and the fourth switch 14, and the A / D acquisition module 22 is connected to the preamplifier 23, which is connected to the receiving coil 24. It should be noted that in this invention, the main control module 1, host computer 2, power supply 3, DC-DC boost module 4, DC-DC buck-boost adjustment module 5, DC-DC buck module 6, first switch 7, second switch 8, first protection diode 9, second protection diode 10, third protection diode 11, capacitor 12, third switch 13, fourth switch 14, clamping capacitor group 15, PWM drive module 16, current sensor 18, transmitting coil 19, DC-DC high voltage clamping module 20, damping resistor 21, A / D acquisition module 22, and preamplifier 23 are all common components. The transient electromagnetic detection device proposed in this invention organically integrates and consolidates the above-mentioned devices or modules into a whole. It should be emphasized that, as individual devices or modules, the specific structures for achieving their respective functions already exist in the prior art, and the protocols, software, or programs involved in the operation of each device and / or module also exist in the prior art, which are fully known to those skilled in the art.

[0019] The proposed towed transient electromagnetic detection device based on multi-magnetic moment emission has a main control module 1 as its core. The main control module 1 uses an STM32 series microcontroller and is responsible for the timing control, PWM signal generation, current waveform monitoring, and data acquisition of the entire transient electromagnetic detection device. The transient electromagnetic detection device is powered by a power supply 3, and the required voltage is provided in stages through a DC-DC boost module 4, a DC-DC step-up / step-down adjustment module 5, and a DC-DC step-down module 6. The protection circuit in this invention includes a first protection diode 9, a second protection diode 10, and a third protection diode 11 connected in series in the corresponding power supply branches. The first protection diode 9 is used to prevent damage from excessive voltage when the DC-DC boost module 4 is connected to the circuit. The second protection diode 10 is used to prevent damage from excessive voltage and reverse charging during the switching from the DC-DC boost module 4 to the DC-DC step-down adjustment module 5 when it is connected to the circuit. The third protection diode 11 is used to prevent damage from excessive voltage when the DC-DC step-down module 6 is connected to the circuit. The main control module 1 generates a PWM signal with adjustable frequency and duty cycle, which drives the H-bridge transmitting module 17 to operate through the PWM drive module 16, generating a corresponding bipolar transmitting current, which in turn generates an excitation magnetic field through the transmitting coil 19. The main control module 1 monitors the current waveform of the transmitting coil 19 through the current sensor 18. The main control module 1 controls the preamplifier 23 and the A / D acquisition module 22 to amplify and acquire the signal sensed by the receiving coil 24. The host computer 2 realizes human-machine interaction, transmitting the parameters required for the operation of the transient electromagnetic detection device to the main control module 1, and receiving and displaying the data returned from the main control module 1. The receiving coil 24 receives the secondary field signal generated by the transmitting coil 19 through the underground medium, thereby obtaining underground geological information. The mobile platform 25 is composed of a non-metallic frame and wheels, carrying the transmitting coil 19 and the receiving coil 24 for mobile measurement, avoiding manual coil laying and improving detection efficiency. The tow truck 26 has three driving modes: unmanned driving, manual driving, or manual towing. The tow truck 26 carries the electromagnetic transmitting and receiving systems and is used to tow the mobile platform 25. The first switch 7, the second switch 8, and the third switch 13 are ordinary switch triggers; the fourth switch 14 uses an IGBT switch with an anti-parallel diode (IGBT switch, full name insulated gate bipolar transistor); when the fourth switch 14 is open, current flows through the internal diode into the clamping capacitor group 15, such as... Figure 4 As shown in the diagram. The specific structures of the first switch 7, the second switch 8, the third switch 13, and the fourth switch 14 are all existing technologies and will not be described in detail here. Figure 4 In the diagram, A represents the first switch timing sequence; B represents the second switch timing sequence; C represents the third switch timing sequence; and D represents the fourth switch timing sequence.

[0020] The control process for multi-mode transmit current is as follows: First magnetic moment pulse transmission mode: Under the control of the main control module 1, the first switch 7 is closed, connecting the DC-DC boost module 4 and capacitor 12 into the circuit; simultaneously, the fourth switch 14 is closed, activating the high-voltage clamping module 20 and guiding the transmission current to rise rapidly. After entering the flat-top maintenance phase, the first switch 7 remains closed, and the DC-DC boost module 4 maintains a stable current.

[0021] Second magnetic moment pulse emission mode: Close the second switch 8 to enable the DC-DC buck-boost regulator module 5 to operate in boost mode; simultaneously close the fourth switch 14 to connect the high-voltage clamping module 20 to achieve a rapid current increase. During the flat-top phase, keep the second switch 8 closed, and maintain the current through the DC-DC buck-boost regulator module 5.

[0022] Third magnetic moment pulse emission mode: Close the second switch 8 to make the DC-DC buck-boost regulator module 5 work in buck mode; at the same time, close the fourth switch 14 to connect the high-voltage clamping module 20 to assist the current to rise rapidly. During the flat-top phase, the DC-DC buck-boost regulator module 5 continues to maintain the current.

[0023] Fourth magnetic moment pulse emission mode: Disconnect the first switch 7, the second switch 8 and the fourth switch 14. At this time, the DC-DC step-down module 6 supplies power and guides the current to rise. During the flat-top phase, keep the first switch 7, the second switch 8 and the fourth switch 14 disconnected, and maintain the current by the DC-DC step-down module 6.

[0024] Among them, the peak currents of the first magnetic moment pulse, the second magnetic moment pulse, the third magnetic moment pulse and the fourth magnetic moment pulse decrease sequentially.

[0025] Turn-off Phase and Protection Mechanism: During the current turn-off phase, the main control module 1 controls the fourth switch 14 to open. When the fourth switch 14 is open, the current flows into the clamping capacitor group 15 through the internal diode, connecting the clamping capacitor group 15 to the circuit to achieve voltage clamping and force the current to drop rapidly. At the same time, the damping resistor 21 is connected by closing the third switch 13 to suppress current overshoot and tailing oscillation during the turn-off process.

[0026] Auxiliary function implementation: The main control module 1 generates a PWM signal with adjustable frequency and duty cycle to drive the H-bridge transmitting module 17 to generate a bipolar transmitting current. The current waveform of the transmitting coil 19 is monitored in real time by the current sensor 18 to ensure waveform quality. The received signal is conditioned and acquired by the preamplifier 23 and the A / D acquisition module 22. The mobile platform 25, in conjunction with the tow truck 26, enables the mobile deployment and measurement of the transmitting coil 19 and the receiving coil 24, effectively improving detection efficiency.

[0027] See Figure 3As shown, this embodiment provides a method for rapid and high-precision towed array electromagnetic detection in urban underground space using the aforementioned transient electromagnetic detection device. The method includes the following steps: Step 1: After connecting the transient electromagnetic detection device, input the voltage parameters Uin of the DC-DC boost module 4, the DC-DC buck-boost adjustment module 5, and the DC-DC buck module 6 through the host computer 2, as well as the number of transmission cycles Q and the transmission frequency f, and then transmit them to the main control module 1. Step 2: The main control module 1 adjusts the output voltage of the DC-DC boost module 4, DC-DC buck-boost adjustment module 5 and DC-DC buck module 6 according to the input voltage parameter Uin, and adjusts the frequency and duty cycle of the transient electromagnetic detection device's transmission waveform according to the input transmission frequency f. Step 3: The current magnitude of the transmitting coil 19 is continuously collected by the current sensor 18, and the main control module 1 starts the current detection process through the current sensor 18. Step 4: Begin transmitting multiple magnetic moment pulse waveforms with different peak currents; Step 5: Has the transmission of multiple magnetic moment pulse waveforms with different peak currents been completed? If yes, the operation ends; otherwise, proceed to step 3.

[0028] Step 4 is as follows: Within one cycle T, multiple magnetic moment pulse waveforms with different peak currents are emitted once, where T is the excitation pulse period. The control signal for the H-bridge transmitting module 17 is u (PWM-A, PWM-B). The pulse emission steps for a single cycle are as follows: Step 401: The main control module 1 closes the first switch 7 and the fourth switch 14 by control, and connects the DC-DC boost module 4, capacitor 12 and DC-DC high voltage clamping module 20 into the circuit to prepare for the first magnetic moment positive polarity pulse emission. Step 402: Start transmitting the first magnetic moment positive polarity pulse. The PWM drive module 16 transmits the PWM-A to drive the H-bridge transmitter module 17, causing the first transistor Q1 and the fourth transistor Q4 to close. At this time, t=t1, and prepare to enter the rapid current rise stage. Step 403: Determine if the transmitting current has risen to its maximum value I. max If yes, proceed to step 404; otherwise, repeat this step. The judgment is based on whether the real-time current parameters collected by the current sensor 18 have reached their peak value. Step 404: The main control module 1 controls the fourth switch 14 to open, and the DC-DC boost module 4 and capacitor 12 maintain the transmission current; Step 405: Determine whether PWM-A has ended. If yes, proceed to step 406; otherwise, repeat this step. The determination is based on whether the real-time current parameters collected by the current sensor 18 have started to decrease. Step 406: The main control module 1 continues to control the first switch 7 to close. When PWM-A ends, the circuit current flows into the clamping capacitor group 15 through the diode of the fourth switch 14. At this time, the clamping capacitor group 15 applies a reverse clamping voltage across the transmitting coil 19, causing the transmitting coil current to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. Step 407: The main control module 1 controls the third switch 13 to close, so that the damping resistor 21 is connected to the transmitting coil 19, which solves the problem of overshoot of the transmitting current and prevents the transmitting waveform from trailing and oscillating. Step 408: The main control module 1 controls the first switch 7 and the third switch 13 to open, disconnecting the damping resistor 21 from the transmitting coil 19; Step 409: Determine whether the signal acquisition is complete. If yes, proceed to step 410; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to T / 8. Step 410: Main control module 1 maintains the switch drive state unchanged and begins the second magnetic moment positive polarity pulse emission; Step 411: The main control module 1 closes the second switch 8 and the fourth switch 14 by controlling the DC-DC step-up / step-down adjustment module 5 and the DC-DC high-voltage clamping module 20 into the circuit. At this time, the DC-DC step-up / step-down adjustment module 5 is working in the voltage rise mode, preparing for the rapid rise of the transmission current. Step 412: Start the transmission of the second magnetic moment positive polarity pulse. The PWM drive module 16 drives the transmitting PWM-A drive H-bridge transmitting module 17 to close the first transistor Q1 and the fourth transistor Q4. At this time, t=t5, and the current rapidly rises. Step 413: Determine if the transmitting current has risen to its maximum value I. max If yes, proceed to step 414; otherwise, repeat this step. The judgment is based on whether the real-time current parameters collected by the current sensor 18 have reached their peak value. Step 414: The main control module 1 controls the fourth switch 14 to open, and the DC-DC buck-boost adjustment module 5 maintains the transmission current; Step 415: Determine whether PWM-A has ended. If yes, proceed to step 416; otherwise, repeat this step. The determination is based on whether the real-time current parameters collected by the current sensor 18 have started to decrease. Step 416: The main control module 1 still controls the second switch 8 to close. When PWM-A ends, the circuit current flows into the clamping capacitor group 15 through the fourth switch 14. At this time, the clamping capacitor group 15 applies a reverse clamping voltage across the transmitting coil 19, causing the current of the transmitting coil 19 to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. Step 417: The main control module 1 controls the third switch 13 to close, so that the damping resistor 21 is connected to the transmitting coil 19, which solves the problem of overshoot of the transmitting current and prevents the transmitting waveform from trailing and oscillating. Step 418: The main control module 1 controls the second switch 8 and the third switch 13 to open, disconnecting the damping resistor 21 from the transmitting coil 19; Step 419: Determine whether the signal acquisition is complete. If yes, proceed to step 420; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to T / 4. Step 420: Main control module 1 maintains the switch drive state unchanged and begins to emit the third magnetic moment positive polarity pulse current; Step 421: The main control module 1 closes the second switch 8 by controlling the DC-DC buck-boost adjustment module 5 to connect to the circuit, preparing for the third magnetic moment positive polarity pulse to be emitted. At this time, the DC-DC buck-boost adjustment module 5 is working in buck mode. Step 422: Start transmitting the third magnetic moment positive polarity pulse. The PWM drive module 16 drives the transmitting PWM-A drive H-bridge transmitting module 17 to close the first transistor Q1 and the fourth transistor Q4. At this time, t=t9, and prepare to enter the rapid current rise stage. Step 423: Determine if the transmitting current has risen to its maximum value I. max If yes, proceed to step 424; otherwise, repeat this step. The judgment is based on whether the real-time current parameters collected by the current sensor 18 have reached their peak value. Step 424: The main control module 1 continues to control the second switch 8 to close, and the DC-DC step-up / step-down adjustment module 5 maintains the transmission current; Step 425: Determine whether PWM-A has ended. If yes, proceed to step 426; otherwise, repeat this step. The determination is based on whether the real-time current parameters collected by the current sensor 18 have started to decrease. Step 426: When PWM-A ends, the circuit current flows into the clamping capacitor group 15 through the diode of the fourth switch 14. At this time, the clamping capacitor group 15 applies a reverse clamping voltage across the transmitting coil 19, causing the current of the transmitting coil 19 to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. Step 427: The main control module 1 controls the third switch 13 to close, so that the damping resistor 21 is connected to the transmitting coil 19, which solves the problem of overshoot of the transmitting current and prevents the transmitting waveform from trailing and oscillating. Step 428: The main control module 1 controls the second switch 8 and the third switch 13 to open, disconnecting the damping resistor 21 from the transmitting coil 19; Step 429: Determine whether the signal acquisition is complete. If yes, proceed to step 430; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to 3T / 8. Step 430: Main control module 1 maintains the switch drive state unchanged and begins to emit the fourth magnetic moment positive polarity pulse current; Step 431: The main control module 1 keeps the first switch 7 and the second switch 8 open by controlling the DC-DC step-up / step-down adjustment module 5 into the circuit to prepare for the fourth magnetic moment positive polarity pulse emission; Step 432: Start transmitting the fourth magnetic moment positive polarity pulse. The PWM drive module 16 drives the transmitting PWM-A drive H-bridge transmitting module 17 to close the first transistor Q1 and the fourth transistor Q4. At this time, t=t13, and prepare to enter the rapid current rise stage. Step 433: Determine if the transmitting current has risen to its maximum value I. max If yes, proceed to step 434; otherwise, repeat this step. The judgment is based on whether the real-time current parameters collected by the current sensor 18 have reached their peak value. Step 434: The main control module 1 controls the first switch 7 and the second switch 8 to open, and the DC-DC step-down module 6 maintains the transmission current; Step 435: Determine whether PWM-A has ended. If yes, proceed to step 436; otherwise, repeat this step. The determination is based on whether the real-time current parameters collected by the current sensor 18 have started to decrease. Step 436: When PWM-A ends, the circuit current flows into the clamping capacitor group 15 through the diode of the fourth switch 14. At this time, the clamping capacitor group 15 applies a reverse clamping voltage across the transmitting coil 19, causing the current of the transmitting coil 19 to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. Step 437: The main control module 1 controls the third switch 13 to close, so that the damping resistor 21 is connected to the transmitting coil 19, which solves the problem of overshoot of the transmitting current and prevents the transmitting waveform from trailing and oscillating. Step 438: The main control module 1 controls the third switch 13 to open, disconnecting the damping resistor 21 from the transmitting coil 19; Step 439: Determine whether the signal acquisition is complete. If yes, proceed to step 440; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to T / 2. Furthermore, power supply 3 charges capacitor 12, and the voltage change of capacitor 12 during charging satisfies the formula: ; in This is the capacitor voltage. This is the power supply output voltage. The charging time for the capacitor. The internal resistance of the power supply This refers to the capacitance value. Step 440: End signal acquisition from the receiving coil and end current transmission in cycle T / 2.

[0029] Furthermore, the negative pulse emission in the latter T / 2 cycles is similar to the positive pulse emission, except that the second transistor Q2 and the third transistor Q3 of the H-bridge transmitter module 17 are closed during the negative pulse current emission phase, and the control signal is a negative PWM signal to emit the negative pulse.

[0030] like Figure 4 As shown, PWM-A represents a positive PWM signal and PWM-B represents a negative PWM signal. It should be noted that the "positive" and "negative" of the PWM signal (pulse width modulation) describe the direction of its duty cycle deviation relative to the reference level, that is, whether the effective level is high or low. A positive PWM signal (effective level high) and a negative PWM signal (effective level low) belong to the prior art.

[0031] The traditional emission waveform and the multi-magnetic-moment emission waveform were compared and verified using Matlab software under the same conditions and simulation environment. The simulated current output waveform of the multi-magnetic-moment emission transient electromagnetic detection device of this invention is shown in Figure 5, and the simulated current output waveform of the traditional single-magnetic-moment emission detection device is shown in Figure 5. Figure 6 As shown, by Figure 5 and Figure 6 It can be seen that, firstly, in terms of the number of magnetic moment emissions, the multi-magnetic moment emission transient electromagnetic detection device proposed in this invention can emit four different peak current emission waves, achieving multi-magnetic moment pulse emission and thus enabling detection at both shallow and deep depths compared to traditional single-magnetic moment emission transient electromagnetic detection devices; secondly, in terms of peak emission current, the multi-magnetic moment emission transient electromagnetic detection device proposed in this invention has a maximum peak emission current of 90A, which is more than twice that of the traditional emission current under the same simulation conditions, resulting in deeper detection depths; thirdly, at the shallow detection level, the minimum emission current of the multi-magnetic moment emission transient electromagnetic detection device proposed in this invention is less than 20A, which is less than half that of the traditional emission current under the same simulation conditions, enabling better detection of shallow geological information. To conduct a simulation comparison and verification of the rise time of traditional and multi-magnetic moment emission under the same conditions and simulation environment, the current rise waveform of the multi-magnetic moment emission detection device is shown below. Figure 7 As shown: The following is the current rise waveform of a conventional single magnetic moment emission detection device, as follows: Figure 8 As shown, by Figure 7 and Figure 8As can be seen, under the same simulation conditions, the rise time of the multi-magnetic-moment emission transient electromagnetic detection device proposed in this invention, after the action of the clamping module, is approximately 0.003s, while the rise time of the traditional transient electromagnetic detection device is approximately 0.008s. The data shows a significant optimization and improved linearity. To verify the optimization of the tail current during traditional emission turn-off and the tail current during multi-magnetic-moment emission turn-off under the same conditions and simulation environment, the tail current waveform of the multi-magnetic-moment emission detection device during current turn-off is shown below. Figure 9 As shown; the tail current waveform of a conventional single magnetic moment emission and detection device when turned off is as follows. Figure 10 As shown; by Figure 9 and Figure 10 It can be seen that, under the same simulation conditions, the multi-magnetic-moment transient electromagnetic detection device proposed in this invention has a good effect on absorbing the tail oscillation of the emission current by precisely controlling the connection of the damping resistor 21. Compared with the traditional transient electromagnetic emission device, the tail current has a very good optimization effect.

Claims

1. A towed transient electromagnetic detection device based on multi-magnetic-moment emission, characterized in that, include: The system comprises a main control module, a host computer, a transmitting system, a receiving system, a multi-channel power supply module, a clamping module, a damping module, a PWM drive module, and a current sensor. The host computer is communicatively connected to the main control module and is used to send control parameters and receive acquired data. The transmitting system includes a transmitting coil and an H-bridge transmitting module, which is electrically connected to the transmitting coil to drive it. The receiving system includes a receiving coil, a preamplifier, and an A / D acquisition module. The receiving coil is connected to the main control module sequentially through the preamplifier and the A / D acquisition module. The multi-channel power supply module includes a DC-DC boost module, a DC-DC buck-boost adjustment module, and a DC-DC buck module. The DC-DC boost module is connected in parallel with a capacitor and sequentially connected to the H-bridge transmitting module through a first switch and a first protection diode. The DC-DC buck-boost adjustment module is sequentially connected to the H-bridge transmitting module through a second switch and a second protection diode. The DC-DC buck module is connected to the H-bridge transmitting module through a third protection diode. The system is connected to the H-bridge transmitting module; the clamping module includes a clamping capacitor bank and a DC-DC high-voltage clamping module, the clamping capacitor bank and the DC-DC high-voltage clamping module are connected in parallel, and their first connection point is connected to the H-bridge transmitting module through a fourth switch, and the second connection point is grounded; the damping module includes a damping resistor and a third switch, the damping resistor is connected in parallel across the transmitting coil through the third switch; the input terminal of the PWM drive module is connected to the main control module, and the output terminal is connected to the H-bridge transmitting module, used to drive the H-bridge transmitting module according to the control signal of the main control module; the current sensor is connected to the main control module, used to monitor the current waveform of the transmitting coil in real time and feed the monitoring result back to the main control module; wherein the main control module is configured to switch the working state of the multi-channel power supply module and the clamping module in a time-division manner by controlling the closing or opening of the first switch, the second switch, the third switch and the fourth switch, so as to generate multiple magnetic moment pulse waveforms with different peak currents in a single transmitting cycle.

2. The towed transient electromagnetic detection device based on multi-magnetic-moment emission according to claim 1, characterized in that, It also includes a power supply, a mobile platform, and a trailer. The power supply is connected to the main control module and is used to power the entire transient electromagnetic detection device. The mobile platform is used to carry the transmitting coil and the receiving coil. The trailer is used to tow the mobile platform.

3. The towed transient electromagnetic detection device based on multi-magnetic-moment emission according to claim 1, characterized in that, The H-bridge transmitting module includes a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes a first transistor and a second transistor connected in series, and the second half-bridge branch includes a third transistor and a fourth transistor connected in series. The series connection node of the first transistor and the second transistor is connected to one end of the transmitting coil, and the series connection node of the third transistor and the fourth transistor is connected to the other end of the transmitting coil. The common terminal of the first transistor and the third transistor is connected to the first protection diode, the second protection diode, the third protection diode, and the fourth switch. The common terminal of the second transistor and the fourth transistor is grounded.

4. The towed transient electromagnetic detection device based on multi-magnetic-moment emission according to claim 1, characterized in that, The DC-DC buck-boost adjustment module has two working modes: boost and buck. The main control module controls the switching of its working mode according to the launch stage.

5. A towed transient electromagnetic detection method based on multi-magnetic moment emission, wherein the method employs the towed transient electromagnetic detection device based on multi-magnetic moment emission as described in any one of claims 1-4 for detection, characterized in that, The method includes: Step S1: Input control parameters to the main control module via the host computer. The control parameters include the output voltage of the multi-power supply module, the transmission frequency, and the number of transmission cycles. Step S2: The main control module adjusts the output voltage and transmission waveform parameters of the DC-DC boost module, DC-DC buck-boost adjustment module, and DC-DC buck module according to the control parameters. Step S3: The main control module controls the closing or opening of the first switch, the second switch and the fourth switch in a time-sharing manner, so that the multi-channel power supply module and the clamping module work in a time-sharing manner, and sequentially generate multiple magnetic moment pulses with different peak currents within a single transmission cycle; Step S4: During the current rise and turn-off phases, the clamping module is connected to the circuit by closing the fourth switch to perform voltage clamping, thereby optimizing the current rise and turn-off speeds. Step S5: At the end of the emission current turn-off period, the damping resistor is connected to the circuit by closing the third switch to absorb residual energy and suppress current oscillation; Step S6: The secondary field signal is acquired by the receiving system and transmitted to the main control module for processing via the A / D acquisition module.

6. The towed transient electromagnetic detection method based on multi-magnetic-moment emission according to claim 5, characterized in that, In step S3, the multiple magnetic moment pulses with different peak currents include a first magnetic moment pulse, a second magnetic moment pulse, a third magnetic moment pulse, and a fourth magnetic moment pulse. The peak currents of the first magnetic moment pulse, the second magnetic moment pulse, the third magnetic moment pulse, and the fourth magnetic moment pulse decrease sequentially, corresponding to deep, medium-deep, medium-shallow, and shallow geological exploration, respectively.

7. The towed transient electromagnetic detection method based on multi-magnetic-moment emission according to claim 6, characterized in that, In step S3, the time-sharing control includes: During the first magnetic moment pulse emission phase, the first and fourth switches are closed, and power is supplied by the DC-DC boost module and the capacitor. During the second magnetic moment pulse emission phase, the second and fourth switches are closed, and the DC-DC buck-boost regulator module operates in boost mode to supply power. During the third magnetic moment pulse emission phase, the second switch is closed, and the DC-DC buck-boost regulator module operates in buck mode to provide power. During the fourth magnetic moment pulse emission phase, the first, second, and fourth switches are disconnected, and power is supplied by the DC-DC step-down module.

8. The towed transient electromagnetic detection method based on multi-magnetic-moment emission according to claim 5, characterized in that, In step S4, the voltage clamping includes active constant voltage clamping through a DC-DC high voltage clamping module and a clamping capacitor bank during the current rise phase and the turn-off phase.

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