Unmanned aerial vehicle transient electromagnetic exploration device and control method for constant current emission silence reception

Abstract

The application discloses a kind of unmanned aerial vehicle transient electromagnetic detection devices and control methods of constant-current emission silence reception, it is related to geophysical electromagnetic detection field.The device includes the transient electromagnetic transceiver integrated machine fixed below unmanned aerial vehicle, its built-in constant-current emission circuit, receiving circuit and time sequence control circuit.Constant-current emission circuit includes constant-current Buck circuit, H bridge circuit, current sensor, hysteresis comparator and relay.The method is controlled by time-sharing through transceiving, makes the circuit enter electromagnetic silence state in acquisition stage, greatly improves the collection purity of weak secondary field signal;While hysteresis comparator and time sequence control circuit cooperate and regulate constant-current Buck circuit, in combination with current sensor real-time sampling, realize the high-precision closed-loop constant-current control of emission current, optimize flat section and off along waveform quality, reduce shallow layer detection blind area;While adapting unmanned aerial vehicle realizes long time efficient detection under limited power supply.

Description

Technical Field

[0001] This invention belongs to the field of geophysical electromagnetic detection technology, specifically, it relates to a transient electromagnetic detection device and control method for a UAV that transmits with constant current and receives with silent reception. Background Technology

[0002] The UAV-borne transient electromagnetic detection system, relying on the UAV's flexible take-off and landing, rapid mobility, and no need for ground laying, breaks through the bottleneck of traditional towed and vehicle-mounted detection equipment being limited in operation in complex terrain, densely populated urban areas, and dangerous areas. It has demonstrated irreplaceable application value in emergency exploration, shallow fine detection, and large-scale rapid surveys.

[0003] However, existing UAV-borne transient electromagnetic detection systems, in order to accommodate the limited payload space and size of UAVs, typically arrange the transmitter and receiver in a compact manner, resulting in an excessively small physical distance between them. When the system is conducting detection operations, the strong electromagnetic signals emitted by the transmitter directly affect the nearby receiver through spatial coupling, creating strong primary interference. This interference is superimposed on the effective detection signal acquired by the receiver, causing not only a significant decrease in the signal-to-noise ratio but also distortion of the target field data. This easily leads to distortion of detection results, reduced detection depth and resolution, making it difficult to meet the requirements of high-precision field detection operations. Furthermore, due to strict limitations in payload weight, power supply capacity, space size, and flight stability, there are significant technical bottlenecks in practical applications: First, limited by the power density of the airborne transmitting circuit and the lightweight design of the antenna, existing systems often experience interference from the secondary field caused by high-power switching devices in the transmitting circuit during the data acquisition phase; and it is difficult to generate a highly stable constant current transmission waveform, leading to interference from deep geological conditions. The system suffers from several drawbacks. First, the signal-to-noise ratio of the response signal is extremely low, the emission magnetic moment exhibits large dispersion, and the excitation energy exhibits poor consistency. Second, the slow rise time of the emission current and the distortion of the current waveform in the flat-top section directly lead to a large blind zone in shallow detection and distortion of time-frequency signals, failing to meet the high-precision detection requirements of shallow underground layers in urban areas. Third, the system lacks a constant current closed-loop control mechanism, making the emission current susceptible to fluctuations in antenna temperature, battery voltage, and load changes, resulting in insufficient parameter stability and difficulty in adapting to multi-depth and multi-scenario detection needs. Furthermore, the traditional emission circuit has low energy utilization and concentrated heat generation, which contradicts the characteristics of short flight time and limited heat dissipation space of UAVs, making it unable to support long-term continuous flight detection operations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a constant-current transmitting and silent receiving UAV transient electromagnetic detection device and a corresponding control method. This transient electromagnetic detection device and control method utilize time-division multiplexing control technology to completely shut down the constant-current Buck circuit and H-bridge circuit during the receiving phase, achieving electrical isolation between the constant-current transmitting and receiving circuits. This eliminates the impact of high-power switching devices on the purity of the secondary field signal acquisition, significantly improving the signal-to-noise ratio. Furthermore, this invention employs constant-current closed-loop control technology to improve circuit energy utilization and suppress the impact of battery voltage fluctuations and load changes on the secondary field, significantly enhancing detection efficiency and system stability.

[0005] The present invention specifically adopts the following technical solution: According to a first aspect of the present invention, a transient electromagnetic detection device for a UAV with constant current transmission and silent reception is provided, comprising a transient electromagnetic transceiver fixed below the UAV, and a transmitting antenna and a receiving antenna respectively suspended below and electrically connected to the transient electromagnetic transceiver; the transient electromagnetic transceiver integrates a constant current transmitting circuit, a receiving circuit, and a timing control circuit, and the constant current transmitting circuit and the receiving circuit are respectively signal-connected to the timing control circuit; the constant current transmitting circuit includes a constant current Buck circuit, an H-bridge circuit, a current sensor, a hysteresis comparator, and a relay; the input terminal of the constant current Buck circuit is connected to a DC voltage source, and the output terminal is connected to the input terminal of the H-bridge circuit; the output terminal of the H-bridge circuit is connected to the transmitting antenna; the current sensor is connected in series with the constant current Buck circuit. In the inductor branch of the k-circuit, the output voltage signal is fed into the non-inverting input of the hysteresis comparator; the inverting input of the hysteresis comparator is connected to a reference voltage, and its output is coupled to the control electrode of the power switch in the constant current Buck circuit via a relay. The pulse width modulation (PWM) signal output by the hysteresis comparator is transmitted to the control electrode via the relay. The timing control circuit is connected to the control electrode of the relay, the drive control electrode of the power switch in the constant current Buck circuit, and the drive control electrode of each power switch in the H-bridge circuit. During the signal acquisition and reception phase, the timing control circuit controls the relay to disconnect to cut off the PWM signal transmission path and simultaneously turns off all the power switches in the H-bridge circuit, so that both the constant current Buck circuit and the H-bridge circuit are in a power-off and silent state.

[0006] Furthermore, the UAV transient electromagnetic detection device also includes a first signal conditioning circuit; the voltage signal output by the current sensor is filtered and amplified by the first signal conditioning circuit before being input to the non-inverting input of the hysteresis comparator.

[0007] Furthermore, the constant current Buck circuit includes a fifth power switch, a first diode, an energy storage inductor, and a capacitor; the drain of the fifth power switch is connected to the positive terminal of the DC voltage source, and the source of the fifth power switch is simultaneously connected to the cathode of the first diode and one end of the energy storage inductor; the anode of the first diode is connected to the negative terminal of the DC voltage source; the other end of the energy storage inductor is connected to the input terminal of the current sensor; and the capacitor is connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit.

[0008] Furthermore, the H-bridge circuit includes a first power switch, a second power switch, a third power switch, and a fourth power switch; the first power switch and the third power switch are connected in series to form a first bridge arm, and the second power switch and the fourth power switch are connected in series to form a second bridge arm; the first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit; the transmitting antenna is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm, the midpoint of the first bridge arm being the series node of the first power switch and the third power switch, and the midpoint of the second bridge arm being the series node of the second power switch and the fourth power switch; the H-bridge circuit also includes a second diode and a transient voltage suppression diode, the second diode being connected in series between the current sensor and the positive terminal of the DC bus of the H-bridge circuit; the transient voltage suppression diode is connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit.

[0009] Furthermore, the turn-on and turn-off timings of the first power switch and the fourth power switch are completely consistent; the turn-on and turn-off timings of the second power switch and the third power switch are completely consistent, and differ from the timings of the first power switch and the fourth power switch by half a cycle.

[0010] According to a second aspect of the present invention, a constant-current transmit silent receive transient electromagnetic detection control method for unmanned aerial vehicles (UAVs) is provided, applied to the aforementioned constant-current transmit silent receive UAV transient electromagnetic detection device, the method comprising the following steps: Step 1: During the transmission phase, the timing control circuit controls the relay to close, so that the power switch in the constant current Buck circuit is turned on; and the timing control circuit controls a set of power switches arranged diagonally in the H-bridge circuit to turn on, so as to apply an excitation voltage to both ends of the transmitting antenna, thereby establishing a transmission current in the transmitting antenna; Step 2: The current in the inductor branch of the constant current Buck circuit is sampled in real time by a current sensor, the sampled current signal is converted into a voltage signal proportional to it, and the voltage signal is output to the non-inverting input of the hysteresis comparator. Step 3: The hysteresis comparator compares the voltage signal with the reference voltage and outputs a PWM signal; the PWM signal is transmitted to the control electrode of the power switch in the constant current Buck circuit via the relay to control the power switch to turn on and off, so that the amplitude of the flat-top segment of the emission current remains constant within the threshold range determined by the reference voltage; Step 4: After the flat-top segment of the transmitted current lasts for a preset time, the timing control circuit controls all power switches in the H-bridge circuit to turn off, so that the current in the transmitting antenna rapidly decays to zero. Step 5: When the current in the transmitting antenna decays to zero, the UAV transient electromagnetic detection device enters the signal acquisition and reception stage. The timing control circuit controls the relay to disconnect, thereby cutting off the transmission path of the PWM signal and keeping the power switching transistors in the constant current Buck circuit and all the power switching transistors in the H-bridge circuit in the off state, so that the constant current Buck circuit and the H-bridge circuit are both in a power-off and silent state. Step 6: In the signal acquisition and reception stage, the timing control circuit controls the receiving circuit to acquire the secondary field signal sensed by the receiving antenna in order to obtain underground geological information.

[0011] Furthermore, in step 4, the transient voltage suppression diode connected in parallel to the DC bus of the H-bridge circuit absorbs the reverse induced energy generated by the transmitting antenna when the current is turned off, causing the current in the transmitting antenna to rapidly decay to zero.

[0012] Furthermore, the method also includes: In step 1, the timing control circuit controls the first power switch and the fourth power switch in the H-bridge circuit to turn on, so that a positive transmission current is established in the transmitting antenna; After completing a full forward transmission and signal acquisition cycle, the method also includes a reverse transmission and signal acquisition cycle: Step 7: The timing control circuit controls the relay to close and controls the second and third power switches in the H-bridge circuit to turn on, so that a reverse transmission current is established in the transmitting antenna; Step 8: Repeat steps 2 to 5 to complete the constant current control and signal acquisition and reception process of the reverse transmission current.

[0013] Furthermore, the amplitude of the flat-top segment of the transmitting current is determined by the value of the reference voltage; the hysteresis comparator sets the upper and lower threshold voltages for the PWM signal toggling through its internal voltage divider resistor network, thereby locking the amplitude of the flat-top segment of the transmitting current within the hysteresis window range formed by the upper and lower threshold voltages.

[0014] Furthermore, after the voltage signal is filtered and amplified by the first signal conditioning circuit, it is input to the non-inverting input of the hysteresis comparator. During the signal acquisition and reception stage, the timing control circuit also controls the preamplifier, the second signal conditioning circuit and the A / D acquisition module in the receiving circuit to start working, so as to complete the amplification and analog-to-digital conversion acquisition of the secondary field signal.

[0015] Through the above design scheme, the beneficial effects of this invention compared with the prior art are as follows: First, in traditional transient electromagnetic (TEM) detection systems, the transmitter power supply unit generally adopts a mature power supply solution based on DC-DC converter topology. Throughout the complete detection time cycle, this power supply module remains electrically connected to the system's main circuit, providing stable power output during the transmission excitation phase and maintaining standby operation during the reception sampling phase, without performing shutdown or bypass switching operations. This invention employs a transmit-receive time-division power-off control strategy, completely shutting down the constant current transmitting circuit during the reception phase, isolating the electromagnetic coupling between the constant current transmitting circuit and the receiving circuit, and effectively avoiding the adverse effects of the transmission condition on the signal reception stage. This invention uses a constant current Buck circuit as the core of the transmitter and introduces time-division on / off control logic: when the system completes electromagnetic transmission and switches to the signal reception phase, the power supply and power devices on the transmitting side are completely disconnected, actively cutting off the power supply link of the constant current Buck circuit and completely stopping the operation of the constant current transmitting circuit. This design leverages the superior current output characteristics of the constant-current Buck circuit to ensure the stability of the transmission current. Furthermore, by employing a timing strategy that shuts off the constant-current transmission circuit during the receiving phase, it fundamentally avoids the electromagnetic crosstalk and noise interference problems inherent in traditional DC-DC circuits that operate with constant power throughout the process. This significantly improves the purity of the weak secondary field signal acquisition, forming a core technological advantage that distinguishes it from existing technologies. It also optimizes the overall electromagnetic compatibility performance of the equipment, significantly improving the detection signal-to-noise ratio and detection accuracy.

[0016] Secondly, traditional transient electromagnetic transmission circuits rely on passive voltage regulation on the power supply side or only implement a feedforward semi-open-loop compensation approach. Moreover, the waveform of the transmission current cannot remain completely horizontal in the flat-top section, resulting in unstable primary field excitation. Compared with traditional transient electromagnetic transmission circuits, this invention optimizes the design of key waveforms in the flat-top section of the transmission current through closed-loop regulation and control technology of current feedback and hysteresis comparison. This ensures that the output characteristics of the primary field excitation signal remain highly consistent, effectively compressing the transient electromagnetic detection blind zone, improving detection performance, and significantly enhancing the overall efficiency of detection operations. It fundamentally eliminates the interference of battery voltage fluctuations and changes in transmitting antenna impedance on the transmission current, achieving high-precision constant current control and improving detection consistency.

[0017] Third, compared with the multi-power switching scheme, the present invention has higher energy conversion efficiency and lower heat generation, significantly reducing system power consumption and extending the flight time of the UAV; at the same time, it reduces circuit complexity and improves the stability and reliability of the system in complex flight environments.

[0018] Fourth, the present invention adopts a circuit-integrated design, which is highly adaptable to the environment, small in size and light in weight, and easy to carry on UAVs for operation; it is suitable for various scenarios such as emergency exploration, urban underground space exploration, and complex terrain survey. Attached Figure Description

[0019] 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 schematic diagram of the constant current transmitting circuit structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the first operating mode in an embodiment of the present invention; Figure 3 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the second operating mode in an embodiment of the present invention; Figure 4 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the third operating mode in an embodiment of the present invention; Figure 5 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the fourth operating mode in an embodiment of the present invention; Figure 6 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the fifth operating mode in an embodiment of the present invention; Figure 7 This is a schematic diagram of the equivalent circuit of the constant current transmitting circuit in the sixth operating mode in an embodiment of the present invention; Figure 8 This is a schematic block diagram of the circuit structure of the UAV transient electromagnetic detection device provided in an embodiment of the present invention; Figure 9 This is a waveform diagram of the conventional transient electromagnetic emission current in an embodiment of the present invention; Figure 10 This is a current waveform diagram of a key node in the transient electromagnetic constant current transmitting antenna in an embodiment of the present invention; Figure 11 The diagram shows the current waveforms of key nodes in the transient electromagnetic constant current transmitting antenna and the current waveforms in the energy storage inductor in this embodiment of the invention. Detailed Implementation

[0020] 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 of the invention and are not intended to limit the invention. It should be noted that the terms "first," "second," "third," "fourth," "fifth," and "sixth" in this invention are used to distinguish different objects, rather than to describe a specific order.

[0021] The constant-current transmit and silent receive UAV transient electromagnetic detection device provided in this embodiment includes a UAV, a transient electromagnetic transceiver, a transmitting antenna, and a receiving antenna. The transient electromagnetic transceiver is fixedly installed below the UAV and integrates a constant-current transmitting circuit, a receiving circuit, and a timing control circuit. The transmitting antenna is suspended below the transient electromagnetic transceiver and electrically connected to the constant-current transmitting circuit. The receiving antenna is suspended below the transient electromagnetic transceiver and electrically connected to the receiving circuit. Both the constant-current transmitting circuit and the receiving circuit are connected to the timing control circuit. U 5. Signal connection. Figure 1 to Figure 7 The specific topology of the constant current transmitting circuit in this embodiment is shown, while the overall circuit architecture of the UAV transient electromagnetic detection device provided in this embodiment is achieved through... Figure 8 The schematic diagram is presented here.

[0022] The constant current transmitting circuit provided by this invention integrates the following electrical components and functional modules in its circuit architecture: DC voltage source. V in Fifth power switching transistor S 5. First diode D 1. Second diode D 2. Transient voltage suppression diode D 3. Energy storage inductor L 2. Current sensor TA ,capacitance C First power switching transistor S 1. Second power switching transistor S 2. Third power switching transistor S 3. Fourth power switching transistor S 4. Resistance R Load inductance L 1. First gate driver U 1. Second gate driver U 2. Relay K Hysteresis comparator U 3 and the first signal conditioning circuit U 4. Wherein, the first power switch transistor S 1. Second power switching transistor S 2. Third power switching transistor S3. Fourth power switching transistor S 4 and the fifth power switch S 5. IGBTs (Insulated Gate Bipolar Transistors) are preferably used as the controllable semiconductor switching device. It should be noted that an IGBT is a composite power semiconductor device consisting of an IGBT chip and a freewheeling diode packaged together in a circuit; this is known technology and will not be elaborated upon here. Current Sensor TA A voltage-output Hall current sensor is used. First signal conditioning circuit. U 4 and timing control circuit U 5 is also a well-known and mature standard circuit structure in the field, and its specific implementation will not be elaborated in detail. This invention integrates the above-mentioned components and functional modules into a whole circuit system. It should be emphasized that, at the individual unit level, the physical structure for realizing each function is already known in the prior art, and the protocols, software, or programs involved in the operation of each module are also well known to those skilled in the art, and will not be described in detail here.

[0023] Among them, the DC voltage source V in The positive terminal of the fifth power switch is connected to the fifth power switch. S 5. Drain connection; the fifth power switch transistor S The source of 5 is simultaneously with the first diode. D 1's cathode, the energy storage inductor L One end of 2 is connected; the first diode D The anode of 1 is connected to the DC voltage source. V in The negative terminal connection; the energy storage inductor L The other end of 2 is connected to the current sensor. TA The input terminal is connected; the second diode D 2 is connected in series with the current sensor TA On the current path between the H-bridge circuit and the second diode. D The function of 2 is to prevent the downstream current from flowing into the capacitor due to its unidirectional conduction characteristic. C Backflow; the capacitor C The transient voltage suppression diode is connected in parallel between the positive and negative terminals of the DC bus in the H-bridge circuit. D 3 are connected in parallel between the positive and negative terminals of the DC bus in the H-bridge circuit; the first power switch transistor S The source of 1 and the third power switch S 3. Drain connection; the second power switch transistor S The source of 2 and the fourth power switch S 4. Drain connection; the resistor R With the inductor LA series connection forms an equivalent inductive load branch for the transmitting antenna, one end of which is connected to the first power switch. S 1 and the third power switch S The common connection point of 3, the other end of the equivalent inductive load branch is connected to the second power switch. S 2 and the fourth power switch S 4. Common connection point; the current sensor TA The signal output terminal and the first signal conditioning circuit U 4 is connected to its input terminal; the first signal conditioning circuit U The output of 4 is connected to the hysteresis comparator. U The non-inverting input of 3 is connected; the hysteresis comparator U The inverting input terminal of 3 is connected to the reference voltage. V set The reference voltage V set The preset constant voltage value; the hysteresis comparator U The pulse width modulation (PWM) signal output terminal of 3 is connected to the first gate driver. U The input terminal of 1 is connected; the first gate driver U The output terminal of 1 is connected to the fifth power switch. S 5 gate connection, the first gate driver U The output terminal of 1 outputs the fifth gate-source voltage Vgs5 to the fifth power switch. S The gate of 5 is used to drive the fifth power switch. S 5. Close or open; the timing control circuit U The control signal output terminal of 5 is respectively connected to the first gate driver U 1 and second gate drivers U 2 connections; second gate driver U 2. Four independent gate drive signals are provided, namely the first gate-source voltage Vgs1, the second gate-source voltage Vgs2, the third gate-source voltage Vgs3, and the fourth gate-source voltage Vgs4, which are respectively applied to the first power switch. S 1. Second power switching transistor S 2. Third power switching transistor S 3 and the fourth power switch S The gate terminal of 4 is used to achieve independent driving and control of each switching transistor; the timing control circuit U 5's control signal output terminal and the relay K The control terminal is connected; the relay K One output contact of the hysteresis comparator UThe PWM signal path of 3 is connected, and the other output contact is connected to the fifth power switch. S The gate drive circuit input terminal of 5 is connected.

[0024] Furthermore, the first power switch transistor S 1 and the fourth power switch S 4. Simultaneous opening and closing, with completely consistent timing; the second power switch transistor S 2 and the third power switch S 3. Open and close simultaneously, with the first power switch transistor. S 1. Fourth power switching transistor S The timing of 4 is half a cycle apart; within one switching cycle, the constant current transmitting circuit relies on the fifth power switch. S 5, and the first power switch transistor S 1 and the fourth power switch S The first bridge arm, consisting of 4 components, is composed of the second power switch transistor. S 2 and the third power switch S The combination of on and off states of the second bridge arm consisting of 3 is divided into the first working mode, the second working mode, the third working mode, the fourth working mode, the fifth working mode and the sixth working mode in sequence.

[0025] First operating mode: When the fifth power switch transistor... S When the trigger pulse signal of 5 is at a high level, the constant current transmitting circuit enters the first operating mode; in the current mode, the timing control circuit... U 5. Output control signal to close the relay K The fifth power switch S 5 is turned on; the first power switch transistor is turned on. S 1 and the fourth power switch S 4. Conduction; the energy storage inductor L 2 and capacitor C Conduction; the second diode D 2 is turned on; the second power switch is turned on. S 2. Third power switching transistor S 3 and the first diode D 1. Turn off.

[0026] Second operating mode: when the energy storage inductor L The current 2 passes through the current sensor TA The converted voltage signal reaches the hysteresis comparator. U 3 Upper threshold voltage V H At a certain moment, the constant current transmitting circuit enters the second operating mode; in the current mode, the constant current transmitting circuit is in the forward transmitting phase; when the energy storage inductorL The current 2 passes through the current sensor TA The converted voltage signal reaches the hysteresis comparator. U 3 Upper threshold voltage V H Timing, Hysteresis Comparator U The low-level PWM signal output by 3 is transmitted through a relay. K Delivery to the first gate driver U 1. Control the fifth power switching transistor S 5. Perform the shutdown action; the first power switch transistor S 1 and the fourth power switch S 4. Conduction; the energy storage inductor L 2. First diode D 1 and capacitor C Conduction; the second diode D 2 is turned on; the second power switch is turned on. S 2 and the third power switch S 3. Turn off; at this time, the first and second operating modes are controlled by the fifth power switch. S The on and off states of 5 switch alternately to maintain the flat-top section of the emission current.

[0027] Third operating mode: After the forward transmission current in the transmitting antenna maintains the flat-top segment, it enters the turn-off moment; the constant current transmitting circuit enters the third operating mode; in the current mode, the timing control circuit... U 5. Output control signal disconnect relay K Contact, fifth power switch S 5. Turn off; the first power switch transistor S 1 and the fourth power switch S 4. Turn off; the energy storage inductor L 2. First diode D 1 and capacitor C Turn off; the second power switch S 2 and the third power switch S 3. Turn off.

[0028] Fourth operating mode: When the constant current transmitting circuit has been off for 1 / 4 of a cycle, the constant current transmitting circuit enters the fourth operating mode; in the current mode, the constant current transmitting circuit is in the reverse transmission phase; the timing control circuit U 5. Output control signal to close relay K Contacts, the hysteresis comparator U 3. Output a high-level PWM signal, which passes through the relay. K to the first gate driver U 1. The fifth power switch transistor S5 is turned on; the second power switch is turned on. S 2 and the third power switch S 3 is conducting; the second diode D 2. Conduction; the energy storage inductor L 2 and capacitor C Turn on; the first power switch transistor S 1. Fourth power switching transistor S 4 and the first diode D 1. Turn off.

[0029] Fifth operating mode: When the energy storage inductor L The current 2 passes through the current sensor TA The converted voltage signal reaches the hysteresis comparator. U 3 Upper threshold voltage V H At a certain moment, the constant current transmitting circuit enters the fifth operating mode; in the current mode, the hysteresis comparator... U The low-level PWM signal output by 3 is transmitted through a relay. K Delivery to the first gate driver U 1. Control the fifth power switching transistor S 5. Perform the shutdown action; the second power switch transistor S 2 and the third power switch S 3 is conducting; the second diode D 2. Conduction; the energy storage inductor L 2. First diode D 1 and capacitor C Turn on; the first power switch transistor S 1 and the fourth power switch S 4. Turn off; at this time, the fourth and fifth operating modes are controlled by the fifth power switch. S The 5-phase switch between on and off states maintains the flat-top section of the reverse emission current.

[0030] Sixth operating mode: After the reverse transmission current in the transmitting antenna maintains the flat-top segment, the constant current transmitting circuit enters the turn-off moment; the constant current transmitting circuit enters the sixth operating mode; in the current mode, the timing control circuit... U 5. Output control signal disconnect relay K Contact, fifth power switch S 5. Turn off; the second power switch transistor S 2 and the third power switch S 3. Turn off; the energy storage inductor L 2. First diode D 1 and capacitor C Turn off; the first power switch transistor S1 and the fourth power switch S 4. Turn off.

[0031] Specifically, the first operating mode operates as follows: when the fifth power switch transistor... S When the trigger pulse signal of 5 is at a high level, the timing control circuit... U 5. Output control signal to close the relay K The hysteresis comparator U 3. Continuously output a high-level PWM signal to the first gate driver U 1. The first gate driver U 1. Output the fifth gate-source voltage Vgs5, the fifth power switch transistor S 5 is turned on; the timing control circuit is turned on. U 5. Output control signal to the second gate driver U 2, the second gate driver U 2. Output the first gate-source voltage Vgs1 and the fourth gate-source voltage Vgs4, the first power switch transistor S 1 and the fourth power switch S 4 is conducting; the second diode D 2. The circuit is on; the constant current transmitting circuit is in the forward transmitting phase; the energy storage inductor... L The current in 2 rises rapidly, simultaneously supplying the capacitor. C Charging; the current sensor TA Energy storage inductor L The current in 2 passes through the current sensor. TA The converted voltage signal is then processed by the first signal conditioning circuit. U 4. After filtering and amplification, the result is compared with the hysteresis comparator. U 3 reference voltage V set The comparison continues until the hysteresis comparator is reached. U 3 Upper threshold voltage V H .

[0032] Specifically, the second operating mode operates as follows: when the energy storage inductor L The current 2 passes through the current sensor TA The converted voltage signal reaches the hysteresis comparator. U 3 Upper threshold voltage V H At time, the hysteresis comparator U The low-level PWM signal output by 3 is transmitted through the first gate driver. U 1. Transmission, control of the fifth power switch transistor S5. Perform the shutdown action; the timing control circuit U 5. Output control signal to the second gate driver U 2, the first power switch S 1 and the fourth power switch S 4 is conducting; the second diode D 2 is turned on; at this time, the capacitor is turned on. C and the energy storage inductor L 2. Charge the transmitting antenna, the energy storage inductor L The current in step 2 will continue to decrease, passing through the current sensor. TA The converted voltage signal continues until it reaches the hysteresis comparator. U 3 Lower threshold voltage V L .

[0033] It is important to emphasize that the current sensor TA Continuously collect data from the energy storage inductor L The current in 2 passes through the current sensor. TA The converted voltage signal is then processed by the first signal conditioning circuit. U 4. After filtering and amplification, compared with a hysteresis comparator U 3 Lower threshold voltage V L Compare; if the energy storage inductor L The current in 2 passes through the current sensor. TA The converted voltage signal is less than that of the hysteresis comparator. U 3 Lower threshold voltage V L The hysteresis comparator U 3. Output a high-level PWM signal to the first gate driver. U 1. The first gate driver U 1. Output the fifth gate-source voltage Vgs5, the fifth power switch transistor S 5. Conductivity, Energy Storage Inductor L The current in 2 continues to increase; that is, the first and second operating modes are controlled by the fifth power switch. S The on and off states of 5 switch alternately to maintain the flat-top section of the positive emission current.

[0034] Specifically, the third operating mode operates as follows: after the forward transmission current in the transmitting antenna is maintained at the flat-top segment for a period of time, the timing control circuit... U 5. Output control signal to disconnect the relay K Contact, fifth power switch S 5. Shutdown; the timing control circuit U5. Output control signal to the second gate driver U 2, the second gate driver U 2. Output a low-level PWM signal to the first power switch. S 1 and the fourth power switch S 4; the first power switch transistor S 1 and the fourth power switch S 4. Turn off; the energy storage inductor L 2. First diode D 1 and capacitor C Turn off; the second power switch S 2 and the third power switch S 3. Turn off; Since the transmitting antenna is an inductive load, the current cannot change abruptly. At this time, the transient voltage suppression diode... D 3. When the transmitting antenna is turned on, the current in the transmitting antenna passes through the second power switch. S 2 and the third power switch S The freewheeling diode of 3 is subjected to the transient voltage suppression diode. D 3. Absorption: The forward transmission current in the transmitting antenna rapidly decreases to 0. At this time, the constant current transmitting circuit is in signal acquisition mode, and the timing control circuit... U 5. The receiving circuit, which is formed by controlling the preamplifier, the second signal conditioning circuit and the A / D acquisition module, amplifies and acquires the signal sensed by the receiving antenna; the receiving antenna receives the secondary field signal generated by the transmitting antenna through the underground medium, thereby obtaining underground geological information.

[0035] It is important to emphasize that after a forward transmitting current is passed through the transmitting antenna, an excitation signal is transmitted to the underground medium to establish a stable primary field. The receiving antenna receives the secondary field response signal generated by the electromagnetic induction of the underground medium. At this point, the UAV transient electromagnetic detection device enters the signal acquisition and reception phase; the timing control circuit... U 5. The corresponding control level signal has been output synchronously to drive the relay. K The contact is disconnected, thereby enabling the fifth power switch. S With reliable shutdown of step 5, the forward transmission current in the transmitting antenna rapidly decreases to 0. Under this condition, all high-power switching devices in the constant current Buck circuit have ceased their driving operation, completely cutting off the energy output path of the transmitting end at the hardware level. This significantly reduces electromagnetic crosstalk and interference coupling caused by the constant current transmitting circuit to the signal acquisition stage of the receiving circuit. It also greatly suppresses the distortion problem caused by high-power switching devices in the DC-DC circuit and the primary field signal to the effective secondary field signal during transient electromagnetic detection, and significantly improves the purity of the secondary field signal acquisition and the accuracy of the detection results.

[0036] It is important to emphasize that the current sensor TA Continuously collect data from the energy storage inductor L The current in 2 passes through the first signal conditioning circuit. U 4. After filtering and amplification, the current passes through the aforementioned current sensor. TA The converted voltage signal and the reference voltage V set The upper and lower thresholds are compared; if the energy storage inductor L The current in 2 passes through the current sensor. TA The converted voltage signal is less than the reference voltage. V set lower threshold V L The hysteresis comparator U 3. Output a high-level PWM signal to the first gate driver. U 1. The first gate driver U 1. Output the fifth gate-source voltage Vgs5, the fifth power switch transistor S 5. Conductivity, Energy Storage Inductor L The current in 2 continues to increase; that is, the first and second operating modes are controlled by the fifth power switch. S The on and off states of 5 switch alternately to maintain the flat-top section of the positive emission current.

[0037] Specifically, the fourth operating mode operates as follows: when the fifth power switch transistor... S When the trigger pulse signal of 5 is at a high level, the timing control circuit... U 5. Output control signal to close the relay K The hysteresis comparator U 3. Continuously output a high level to the first gate driver U 1. The first gate driver U 1. Output the fifth gate-source voltage Vgs5, the fifth power switch transistor S 5 is turned on; the timing control circuit is turned on. U 5. Output control signal to the second gate driver U 2, the second gate driver U 2. Outputs the second gate-source voltage Vgs2 and the third gate-source voltage Vgs3, the second power switch transistor S 2 and the third power switch S 3 is conducting; the second diode D 2. The circuit is on; the constant current transmitting circuit is in the reverse transmission phase; the energy storage inductor... L The current in 2 rises rapidly, simultaneously supplying the capacitor. C Charging; the current sensor TA Energy storage inductor L The current in step 2 passes through the first signal conditioning circuit. U 4. After filtering and amplification, the current passes through the aforementioned current sensor. TA The converted voltage signal is compared with the hysteresis comparator. U 3 reference voltage V set The comparison continues until the hysteresis comparator is reached. U 3 Upper threshold voltage V H .

[0038] Specifically, the fifth operating mode operates as follows: when the energy storage inductor L The current 2 passes through the current sensor TA The converted voltage signal reaches the hysteresis comparator. U Upper limit threshold of 3 V H At time, the hysteresis comparator U 3. Output a low-level PWM signal to the first gate driver. U 1. The fifth power switch transistor S 5. Shutdown; the timing control circuit U 5. Output control signal to the second gate driver U 2. The second power switch S 2 and the third power switch S 3 is conducting; the second diode D 2 is turned on; at this time, the capacitor is turned on. C and energy storage inductor L 2. Charge the transmitting antenna, the energy storage inductor L The current in step 2 will continue to decrease, passing through the current sensor. TA The converted voltage signal continues until it reaches the hysteresis comparator. U 3 Lower threshold voltage V L .

[0039] Specifically, the sixth operating mode operates as follows: after the reverse transmission current in the transmitting antenna maintains the flat-top segment for a period of time, the timing control circuit... U 5. Output control signal to disconnect the relay K Contact, fifth power switch S 5. Shutdown; the timing control circuit U 5. Output control signal to the second gate driver U 2, the second gate driver U 2. Output a low-level PWM signal to the second power switch. S2 and the third power switch S 3; the second power switch S 2 and the third power switch S 3. Turn off; the energy storage inductor L 2. The first diode D 1 and the capacitor C Turn off; the first power switch transistor S 1 and the fourth power switch S 4. Turn off; Since the transmitting antenna is an inductive load, the current cannot change abruptly. At this time, the transient voltage suppression diode... D 3. When the transmitting antenna is turned on, the current in the transmitting antenna passes through the first power switch. S 1 and the fourth power switch S The freewheeling diode of 4 is subjected to the transient voltage suppression diode. D 3. Absorption; the reverse transmission current in the transmitting antenna rapidly decreases to 0, at which point the constant current transmitting circuit re-enters the signal acquisition state, thus completing one transmission cycle; at this time, the timing control circuit... U 5. The receiving circuit, consisting of the preamplifier, the second signal conditioning circuit, and the A / D acquisition module, amplifies and acquires the signal sensed by the receiving antenna. The receiving antenna receives the secondary field signal generated by the transmitting antenna through the underground medium, thereby obtaining underground geological information.

[0040] It is important to emphasize that after a reverse transmission current is passed through the transmitting antenna, an excitation signal is transmitted to the underground medium to establish a stable primary field. The receiving antenna receives the secondary field response signal generated by the electromagnetic induction of the underground medium. At this point, the UAV transient electromagnetic detection device enters the signal acquisition and reception phase; the timing control circuit... U 5. The corresponding control level signal has been output synchronously to drive the relay. K The contact is disconnected, thereby enabling the fifth power switch. S With reliable shutdown of step 5, the reverse transmission current in the transmitting antenna rapidly decreases to 0. Under this condition, all high-power switching devices in the constant current Buck circuit and H-bridge circuit have terminated their driving operation, completely cutting off the energy output path of the transmitting end at the hardware level. This can significantly reduce electromagnetic crosstalk and interference coupling caused by the operation of the transmitting system to the signal acquisition stage of the receiving circuit, greatly suppress the distortion problem caused by high-power switching devices in the DC-DC circuit and the primary field signal to the effective secondary field signal during transient electromagnetic detection, and significantly improve the purity of the secondary field signal acquisition and the accuracy of the detection results.

[0041] It is important to emphasize that the current sensor TA Continuously collect data from the energy storage inductor LThe current in 2 passes through the current sensor. TA The converted voltage signal is then processed by a signal conditioning circuit. U 4. After filtering and amplification, it is compared with a hysteresis comparator. U The upper and lower threshold voltages of 3 are compared; if the energy storage inductor L The current in 2 passes through the current sensor. TA The converted voltage signal is less than that of the hysteresis comparator. U 3 Lower threshold voltage V L The hysteresis comparator U 3. Output a high-level PWM signal to the first gate driver. U 1. The first gate driver U 1. Output the fifth gate-source voltage Vgs5, the fifth power switch transistor S 5. Conductivity, Energy Storage Inductor L The current in 2 continues to increase; that is, the fourth and fifth operating modes are controlled by the fifth power switch. S The on and off states of 5 switch to maintain the flat-top section of the reverse emission current.

[0042] Furthermore, the hysteresis comparator U 3 has two different threshold voltages, namely the upper threshold voltage. V H and lower threshold voltage V L Its width is determined by the hysteresis comparator U The values ​​of the voltage divider resistors at the input and output terminals determine its hysteresis propagation characteristics. Upper threshold voltage. V H The input voltage value that causes the output voltage to jump when the input signal changes from low to high. Lower threshold voltage. V L The input voltage value that causes the output voltage to jump when the input signal changes from high to low.

[0043] Furthermore, current sensor TA Read the current value and convert it into an output voltage value. The high level of the output voltage value is... V OH The output low level is V OL ; Forming hysteresis characteristics: when the hysteresis comparator U 3. The upper threshold voltage at which the output toggles to a high level when the output is low. V H for: ; When the hysteresis comparatorU 3. The lower threshold voltage at which the output toggles to a low level when the output is high. V L for: ; in R m and R n For the hysteresis comparator U A 3-pin voltage divider resistor, R m It is the series resistor between the input terminal and the non-inverting terminal. R n It is the feedback series resistor from the comparator output to the non-inverting input.

[0044] Furthermore, the current sensor TA Continuously collect data from the energy storage inductor L The current in step 2 passes through the signal conditioning circuit. U 4. Filtering, amplification, and passing through the current sensor. TA The converted voltage signal and the reference voltage V set The upper and lower limits are compared by a hysteresis comparator. U 3. The fifth power switch is controlled by a PWM signal with an adjustable duty cycle. S 5. Turn on or off.

[0045] It is important to emphasize that by changing the values ​​of the voltage divider resistors at the input and output terminals, the upper and lower thresholds of the hysteresis window can be altered, thus achieving an adjustable emitter current. It is also crucial to highlight the hysteresis comparator configured in the constant current emitter circuit of this invention. U 3. The upper threshold voltage of its hysteresis window. V H Lower threshold voltage V L The values ​​are not fixed and unadjustable; the core adjustment method for the circuit threshold is to match and adjust the resistance values ​​of the input and output voltage divider resistors. By selectively replacing and fine-tuning the resistance values ​​of the two voltage divider branches, the overall amplitude of the hysteresis loop window and the difference between the upper and lower thresholds can be changed simultaneously, flexibly widening or narrowing the hysteresis comparison range; ultimately achieving the core function of wide-range, fine-grained, and continuously adjustable transmission current, adapting to the differentiated usage requirements of transmission current intensity under different formation detection depths and exploration conditions.

[0046] The UAV transient electromagnetic detection device of this invention adopts a structure consisting of a UAV-mounted transient electromagnetic transceiver, a ring transmitting antenna, and a ring receiving antenna. It is not limited by terrain and can easily traverse areas difficult to access using traditional methods, such as mountains, ravines, and waterways, achieving full-terrain coverage detection. It eliminates the need for manual entry into dangerous areas to deploy antennas, significantly expanding the applicable scenarios of transient electromagnetic methods, especially suitable for geological exploration in mountainous areas, mine disaster detection, and concealed engineering investigation. The UAV enables rapid deployment and movement of the transmission system, eliminating the need for manual handling and deployment of large antennas, reducing survey line setup time to minutes, and increasing detection efficiency by several to tens of times compared to traditional ground methods. Simultaneously, it significantly reduces labor and equipment transportation costs, greatly lowering the implementation cost of exploration projects. The constant current transmitting circuit of this invention effectively isolates the influence of UAV power supply voltage fluctuations and battery degradation in the field on the transmitting current, ensuring a constant current amplitude of the transmitting antenna. Furthermore, the hoisting structure physically separates the transient electromagnetic transceiver from the UAV, reducing the impact of UAV electromagnetic interference on the transmitted signal, improving the consistency and stability of the transmitted waveform, and providing a reliable signal foundation for subsequent data processing. Figure 9 This is a waveform diagram of the conventional transient electromagnetic emission current in an embodiment of the present invention; Figure 10 This is a current waveform diagram of a key node in the transient electromagnetic constant current transmitting antenna in an embodiment of the present invention; such as... Figure 10 As shown, this embodiment uses MATLAB simulation software for simulation, and the parameter settings for each component are as follows: DC voltage source V in The voltage is 20V, and the load is... R The resistance is 0.25Ω, capacitor C The capacitance is 5000μF, and the energy storage inductor L The inductance of 2 is 47μH, and the load inductance is... L The inductance of 1 is 130μH, a transient voltage suppressor diode. D 3. With the parameter set to 500V, the simulation waveform is as follows: Figure 10 As shown, Figure 10 The horizontal axis represents time. It is important to emphasize that when the DC voltage source... V in When the voltage changes, the magnitude of the transmitting current in the transmitting antenna does not change with the DC voltage source. V in The system adapts to changes and effectively solves the interference and impact of battery voltage decay on the transmission current in the field; that is, the system can adapt to changes in DC voltage sources. V in When fluctuations occur, the output current of the transmitting circuit of the transmitting antenna remains constant, effectively avoiding the problem of transmitting current deviation caused by the gradual decay of battery voltage in field operation scenarios, and completely eliminating the adverse interference caused by power supply voltage changes on the stability of the transmitting signal. Figure 11 The current waveform and energy storage inductor of a key node in the transient electromagnetic constant current transmitting antenna in this embodiment of the invention are shown. L Two current waveform diagrams; including the energy storage inductor. L The current (green) in 2 is in the hysteresis comparator U The upper and lower threshold currents of the 3-threshold current vary. Here, the upper and lower threshold currents are obtained by dividing the upper and lower threshold voltages by the corresponding voltage divider resistors; the average output current is 40A.

Claims

1. A transient electromagnetic detection device for unmanned aerial vehicles (UAVs) with constant current transmission and silent reception, comprising a transient electromagnetic transceiver fixed below the UAV, and a transmitting antenna and a receiving antenna respectively suspended below and electrically connected to the transient electromagnetic transceiver; the transient electromagnetic transceiver integrates a constant current transmitting circuit, a receiving circuit, and a timing control circuit, and the constant current transmitting circuit and the receiving circuit are respectively connected to the timing control circuit; characterized in that: The constant current transmitting circuit includes a constant current Buck circuit, an H-bridge circuit, a current sensor, a hysteresis comparator, and a relay. The input of the constant current Buck circuit is connected to a DC voltage source, and the output is connected to the input of the H-bridge circuit. The output of the H-bridge circuit is connected to the transmitting antenna. The current sensor is connected in series in the inductor branch of the constant current Buck circuit, and its output voltage signal is sent to the non-inverting input of the hysteresis comparator. The inverting input of the hysteresis comparator is connected to a reference voltage, and its output is coupled to the control electrode of the power switch in the constant current Buck circuit via a relay. The PWM signal output by the hysteresis comparator is transmitted to the control electrode via the relay. The timing control circuit is connected to the control electrode of the relay, the drive control electrode of the power switch in the constant current Buck circuit, and the drive control electrode of each power switch in the H-bridge circuit. During the signal acquisition and reception stage, the timing control circuit controls the relay to disconnect to cut off the PWM signal transmission path and simultaneously turns off all the power switches in the H-bridge circuit, so that both the constant current Buck circuit and the H-bridge circuit are in a power-off and silent state.

2. The UAV transient electromagnetic detection device with constant current transmission and silent reception according to claim 1, characterized in that, The UAV transient electromagnetic detection device also includes a first signal conditioning circuit; the voltage signal output by the current sensor is filtered and amplified by the first signal conditioning circuit before being input to the non-inverting input of the hysteresis comparator.

3. The UAV transient electromagnetic detection device with constant current transmission and silent reception according to claim 1, characterized in that, The constant current Buck circuit includes a fifth power switch, a first diode, an energy storage inductor, and a capacitor. The drain of the fifth power switch is connected to the positive terminal of the DC voltage source, and the source of the fifth power switch is connected to both the cathode of the first diode and one end of the energy storage inductor. The anode of the first diode is connected to the negative terminal of the DC voltage source. The other end of the energy storage inductor is connected to the input terminal of the current sensor. The capacitor is connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit.

4. The UAV transient electromagnetic detection device with constant current transmission and silent reception according to claim 1, characterized in that, The H-bridge circuit includes a first power switch, a second power switch, a third power switch, and a fourth power switch. The first power switch and the third power switch are connected in series to form a first bridge arm, and the second power switch and the fourth power switch are connected in series to form a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit. The transmitting antenna is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm. The midpoint of the first bridge arm is the series node of the first power switch and the third power switch, and the midpoint of the second bridge arm is the series node of the second power switch and the fourth power switch. The H-bridge circuit also includes a second diode and a transient voltage suppression diode. The second diode is connected in series between the current sensor and the positive terminal of the DC bus of the H-bridge circuit. The transient voltage suppression diode is connected in parallel between the positive and negative terminals of the DC bus of the H-bridge circuit.

5. The UAV transient electromagnetic detection device with constant current transmission and silent reception according to claim 4, characterized in that, The turn-on and turn-off timings of the first power switch and the fourth power switch are completely consistent; the turn-on and turn-off timings of the second power switch and the third power switch are completely consistent, and differ from the timings of the first power switch and the fourth power switch by half a cycle.

6. A constant-current transmit, silent receive transient electromagnetic detection and control method for unmanned aerial vehicles (UAVs), characterized in that, The method for a UAV transient electromagnetic detection device with constant current transmission and silent reception as described in any one of claims 1 to 5 includes the following steps: Step 1: During the transmission phase, the timing control circuit controls the relay to close, so that the power switch in the constant current Buck circuit is turned on; and the timing control circuit controls a set of power switches arranged diagonally in the H-bridge circuit to turn on, so as to apply an excitation voltage to both ends of the transmitting antenna, thereby establishing a transmission current in the transmitting antenna; Step 2: The current in the inductor branch of the constant current Buck circuit is sampled in real time by a current sensor, the sampled current signal is converted into a voltage signal proportional to it, and the voltage signal is output to the non-inverting input of the hysteresis comparator. Step 3: The hysteresis comparator compares the voltage signal with the reference voltage and outputs a PWM signal; the PWM signal is transmitted to the control electrode of the power switch in the constant current Buck circuit via the relay to control the power switch to turn on and off, so that the amplitude of the flat-top segment of the emission current remains constant within the threshold range determined by the reference voltage; Step 4: After the flat-top segment of the transmitted current lasts for a preset time, the timing control circuit controls all power switches in the H-bridge circuit to turn off, so that the current in the transmitting antenna rapidly decays to zero. Step 5: When the current in the transmitting antenna decays to zero, the UAV transient electromagnetic detection device enters the signal acquisition and reception stage. The timing control circuit controls the relay to disconnect, thereby cutting off the transmission path of the PWM signal and keeping the power switching transistors in the constant current Buck circuit and all the power switching transistors in the H-bridge circuit in the off state, so that the constant current Buck circuit and the H-bridge circuit are both in a power-off and silent state. Step 6: In the signal acquisition and reception stage, the timing control circuit controls the receiving circuit to acquire the secondary field signal sensed by the receiving antenna in order to obtain underground geological information.

7. The UAV transient electromagnetic detection and control method for constant current transmission and silent reception according to claim 6, characterized in that, In step 4, the transient voltage suppression diode connected in parallel to the DC bus of the H-bridge circuit absorbs the reverse induced energy generated by the transmitting antenna when the current is turned off, causing the current in the transmitting antenna to decay rapidly to zero.

8. The UAV transient electromagnetic detection and control method for constant current transmission and silent reception according to claim 6, characterized in that, The method further includes: In step 1, the timing control circuit controls the first power switch and the fourth power switch in the H-bridge circuit to turn on, so that a positive transmission current is established in the transmitting antenna; After completing a full forward transmission and signal acquisition cycle, the method also includes a reverse transmission and signal acquisition cycle: Step 7: The timing control circuit controls the relay to close and controls the second and third power switches in the H-bridge circuit to turn on, so that a reverse transmission current is established in the transmitting antenna; Step 8: Repeat steps 2 to 5 to complete the constant current control and signal acquisition and reception process of the reverse transmission current.

9. The UAV transient electromagnetic detection and control method for constant current transmission and silent reception according to claim 6, characterized in that, The amplitude of the flat-top segment of the transmitting current is determined by the value of the reference voltage; the hysteresis comparator sets the upper and lower threshold voltages for the PWM signal toggling through its internal voltage divider resistor network, thereby locking the amplitude of the flat-top segment of the transmitting current within the hysteresis window range formed by the upper and lower threshold voltages.

10. The UAV transient electromagnetic detection and control method for constant current transmission and silent reception according to claim 6, characterized in that, The voltage signal is filtered and amplified by the first signal conditioning circuit before being input to the non-inverting input of the hysteresis comparator. During the signal acquisition and reception stage, the timing control circuit also controls the preamplifier, the second signal conditioning circuit and the A / D acquisition module in the receiving circuit to start working, so as to complete the amplification and analog-to-digital conversion acquisition of the secondary field signal.

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