Ground-space frequency domain electromagnetic detection background magnetic field real-time offset system and control method

Abstract

The invention relates to the technical field of ground-air electromagnetic detection, in particular to a ground-air frequency domain electromagnetic detection background magnetic field real-time counteracting system and a control method, and the system comprises a self-counteracting transmitting coil, a self-counteracting control system and a self-counteracting current source; the self-counteracting transmitting coil is composed of three groups of Helmholtz coils, and the groups of coils are perpendicular to one another; the three groups of Helmholtz coils are fixed on the solid wood frame, and a self-counteracting control system and a self-counteracting current source are also stored on the solid wood frame; the three-component magnetic field sensor and the attitude sensor are fixed in the solid wood frame through binding ropes, and the three-component geomagnetic field orientation measured by the three-component magnetic field sensor corresponds to the three groups of Helmholtz coils. The influence of low-frequency noise caused by a geomagnetic field is eliminated, and high-sensitivity and low-noise electromagnetic signal measurement is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of ground-air electromagnetic detection, and specifically to a real-time background magnetic field cancellation system and control method for ground-air frequency-domain electromagnetic detection. Background Art

[0002] As a non-invasive geophysical exploration method, ground-air frequency-domain electromagnetic detection technology is widely used in the fields of mineral resource exploration, geological disaster warning, underground water resource assessment, and environmental monitoring. When facing complex detection environments on the earth's surface that are difficult for humans to access, such as the land-sea interaction zone and rugged mountainous areas, ground-air electromagnetic detection has great advantages. By deploying emission sources on the ground and using airships or drones to carry receiving systems, magnetic field data can be collected in the measurement area. This method has the advantages of high detection efficiency, large detection depth, and low risk coefficient. However, this technology faces significant challenges in practical applications. The complex surface background magnetic field interference severely restricts the accuracy and reliability of detection data. Among them, the geomagnetic field, as the main component of the background magnetic field, superimposed with dynamic interference sources such as industrial electromagnetic noise and natural electromagnetic interference, will cause a significant decrease in the signal-to-noise ratio of the effective signal. Especially in the low-frequency band of 0.001 Hz to 1 kHz, the interference effect is particularly prominent. For background magnetic field suppression, existing technologies are mainly divided into two categories: passive shielding and active cancellation. Passive shielding relies on high-permeability materials to construct a shielding chamber. Although it can weaken high-frequency interference, its suppression effect on low-frequency geomagnetic fields is limited, and it is difficult to adapt to the dynamic detection environment in the wild. Active cancellation technology can theoretically achieve precise cancellation by generating a cancellation magnetic field with the same amplitude and opposite phase as the interference magnetic field. However, there is a bottleneck in the dynamic adaptability of the active cancellation method in existing ground-air electromagnetic detection systems. The geomagnetic field exhibits time-varying characteristics due to factors such as solar activity and geological structure, while human-made interferences such as power line fluctuations and traffic electromagnetic noise are random and sudden. Currently, most systems adopt fixed parameters or offline calibration modes, which cannot track the dynamic changes of the magnetic field in real time, resulting in cancellation lag or overcompensation, and even introducing additional noise. In recent years, some studies have tried to improve the cancellation effect through multi-sensor fusion and adaptive algorithms, such as a dynamic adjustment system based on PID control. However, such methods rely on the tuning of prior experience parameters and are difficult to cope with the complexity of non-stationary interference.

[0003] Therefore, in the face of the low-frequency noise problem caused by the geomagnetic field in ground-air electromagnetic detection, there is an urgent need to develop a real-time background magnetic field cancellation system and control method for ground-air frequency-domain electromagnetic detection to overcome the deficiencies in current practical applications. Summary of the Invention

[0004] The purpose of the present invention is to provide a real-time background magnetic field cancellation system and control method for ground-air frequency-domain electromagnetic detection to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solutions: A real-time cancellation system for the background magnetic field of ground-air frequency-domain electromagnetic detection, comprising a solid wood frame, a self-cancellation transmitting coil, a self-cancellation control system, and a self-cancellation current source; The self-cancellation transmitting coil is composed of three sets of Helmholtz coils, and each set of coils is perpendicular to each other, and is used to generate a reverse magnetic field opposite to the direction of the three-component geomagnetic field; The three sets of Helmholtz coils are fixed on the solid wood frame, and the self-cancellation control system and the self-cancellation current source are also stored on the solid wood frame; The three-component magnetic field sensor and the attitude sensor are fixed in the solid wood frame by tying ropes, and the azimuth of the three-component geomagnetic field measured by the three-component magnetic field sensor corresponds to the three sets of Helmholtz coils respectively.

[0006] As a further solution of the present invention: The self-cancellation current source is used to differentially collect and linearly step down the voltage signals transmitted by the three-component magnetic field sensor and the attitude sensor. After processing and comparative analysis, it is regulated by the control method in the self-cancellation control system, and a PWM control signal with different duty cycles is output to the self-cancellation current source module to close-loop feedback control the magnitude of the cancellation current flowing to the self-cancellation transmitting coil.

[0007] As a further solution of the present invention: The self-cancellation control system takes the minimum single-chip microcomputer system as the core, collects the three-component magnetic field analog signals output by the three-component magnetic field sensor and the attitude sensor and linearly stepped down, as well as the current signals passing through the three sets of Helmholtz coils. After analysis and processing and comparison with the theoretical current magnitude, it controls the duty cycle of the three-way PWM control signal output to realize the current closed-loop feedback output to the three sets of Helmholtz coils.

[0008] As a further solution of the present invention: The three-component magnetic field sensor is composed of a housing, a connecting part, and an interface. The magnetic field range measured by each magnetic field component is ±1000 μT, and a voltage of ±10 V is output corresponding to the measured magnetic field magnitude.

[0009] As a further solution of the present invention: Among the three sets of Helmholtz coils, coil two and coil five correspond to a set of Helmholtz coils in the Z direction, coil one and coil six correspond to a set of Helmholtz coils in the X direction, and coil three and coil four correspond to a set of Helmholtz coils in the Y direction. Each set of Helmholtz coils is connected by wires.

[0010] As a further solution of the present invention: The self-cancellation current source includes: A linear step-down circuit module for stepping down the input analog signal to the range of 0 V to 3.3 V; A driving circuit, using an IR2104 MOSFET driving chip, for amplifying the PWM control signal; A MOSFET switch for controlling current output; An inductor and a filter capacitor for controlling current ripple and stabilizing the output voltage.

[0011] As a further solution of the present invention: the self-canceling current source further includes an overload protection module for turning off the PWM control signal when the current or voltage exceeds a predetermined value to protect the circuit.

[0012] As a further solution of the present invention: the ground-air frequency-domain electromagnetic detection background magnetic field real-time cancellation system further includes a carrying device, a towing rope, and a support platform; The carrying device is connected to the solid wood frame storing the self-canceling control system and the self-canceling current source through the towing rope, and is used for carrying and transporting the entire cancellation system to the detection area; The support platform is located inside the solid wood frame and is used for placing the ground-air electromagnetic detection sensor.

[0013] As a further solution of the present invention: the solid wood frame includes a solid wood support, solid wood support rods, and a solid wood flat panel. The solid wood support is used to support the entire cancellation system, the solid wood support rods are connected to each group of Helmholtz coils to assist in fixing, and the solid wood flat panel is used to place the self-canceling control system and the self-canceling current source.

[0014] A control method for a ground-air frequency-domain electromagnetic detection background magnetic field real-time cancellation system as described above, comprising the following steps: The attitude sensor stores and records the three-dimensional attitude information of the entire cancellation system during the ground-air electromagnetic detection process, and matches it with the geomagnetic field information measured by the three-component magnetic field sensor; The self-canceling control system processes and analyzes the two types of information to obtain the magnitude information of the three-component geomagnetic field in different attitudes, and outputs three-way PWM control signals corresponding to the cancellation of the three-component geomagnetic field; The self-canceling current source is regulated according to the PWM control signal, and a suitable DC cancellation current is passed through the three groups of Helmholtz coils to generate a reverse magnetic field opposite to the direction of the geomagnetic field, realizing the real-time cancellation of the three-component geomagnetic field in different attitudes.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The present invention designs the existing high-sensitivity three-component magnetic field sensors and attitude sensors, enabling a real-time geomagnetic field cancellation system. Using three sets of Helmholtz coils as three-component magnetic field generators, magnetic signals opposite to the three-component geomagnetic field signals are generated, thereby canceling the three-component geomagnetic field signals and creating a three-dimensional space without geomagnetic field within the system device. This allows the measurement sensors for ground-air electromagnetic detection to measure in a space with weak or even no geomagnetic field influence. The cancellation system uses a single-chip microcomputer as the control system, and a corresponding control method is designed for this control system to achieve the control of the entire cancellation system. At the same time, the real-time monitoring of the geomagnetic field in three components is realized, and a control power supply circuit that quickly outputs response signals is provided, achieving real-time cancellation of the geomagnetic field, eliminating the influence of low-frequency noise caused by the geomagnetic field, and realizing the measurement of high-sensitivity and low-noise electromagnetic signals, providing technical support for the reliable application of ground-air frequency domain detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the real-time cancellation system of the background magnetic field for ground-air frequency domain electromagnetic detection in an embodiment of the present invention.

[0017] Figure 2 It is a functional flowchart of the self-cancellation control system in an embodiment of the present invention.

[0018] Figure 3 It is a development flowchart of the self-cancellation current source in an embodiment of the present invention.

[0019] Figure 4 It is a schematic structural diagram of the three-component magnetic field sensor in an embodiment of the present invention.

[0020] In the figure: 1 - outer shell, 2 - connecting part, 3 - interface, 4 - carrying device, 5 - towing rope, 6 - support platform, 7 - coil one, 8 - solid wood support rod, 9 - coil two, 10 - coil three, 11 - coil four, 12 - coil five, 13 - three-component magnetic field sensor, 14 - self-cancellation control system, 15 - attitude sensor, 16 - coil six, 17 - solid wood bracket, 18 - solid wood flat panel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] The following describes the specific implementation of the present invention in detail in conjunction with specific embodiments.

[0023] Please refer to Figures 1 - 4, a real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection provided by an embodiment of the present invention includes a solid wood frame, a self-canceling transmitting coil, a self-canceling control system 14, and a self-canceling current source; The self-canceling transmitting coil is composed of three sets of Helmholtz coils. Each set of coils is perpendicular to each other, and the three sets of Helmholtz coils form an approximate spherical structure for generating a reverse magnetic field opposite to the direction of the three-component geomagnetic field; The three sets of Helmholtz coils are fixed on the solid wood frame, and the self-canceling control system 14 and the self-canceling current source are also stored on the solid wood frame; The three-component magnetic field sensor 13 and the attitude sensor 15 are fixed in the solid wood frame by tying ropes, and the azimuth of the three-component geomagnetic field measured by the three-component magnetic field sensor 13 corresponds to the three sets of Helmholtz coils respectively.

[0024] The self-canceling current source is used to differentially collect and linearly step down the voltage signals transmitted by the three-component magnetic field sensor 13 and the attitude sensor 15. After processing and comparative analysis, it is regulated by the control method in the self-canceling control system 14, and outputs PWM control signals with different duty cycles to the self-canceling current source module to closed-loop feedback control the magnitude of the canceling current flowing to the self-canceling transmitting coil.

[0025] The self-canceling control system 14 takes the minimum system of a single-chip microcomputer of the STM32 model as the core, collects the three-component magnetic field analog signals output by the three-component magnetic field sensor 13 and the attitude sensor 15 and linearly stepped down, as well as the current signals passed through the three sets of Helmholtz coils. After analysis and processing and comparison with the theoretical current magnitude, it controls the duty cycle of the three-way PWM control signals output to realize the current closed-loop feedback output to the three sets of Helmholtz coils.

[0026] The three-component magnetic field sensor 13 is composed of a housing 1, a connecting part 2, and an interface 3. The magnetic field range measured by each magnetic field component is ±1000 μT, and the voltage magnitude of ±10 V is output corresponding to the measured magnetic field magnitude.

[0027] Among the three sets of Helmholtz coils, coil two 9 and coil five 12 are a set of Helmholtz coils corresponding to the Z direction, coil one 7 and coil six 16 are a set of Helmholtz coils corresponding to the X direction, and coil three 10 and coil four 11 are a set of Helmholtz coils corresponding to the Y direction. Each set of Helmholtz coils is connected by wires.

[0028] The self-canceling current source includes: A linear step-down circuit module for stepping down the input analog signal to the range of 0 V to 3.3 V; A drive circuit using an IR2104 MOSFET drive chip for amplifying the PWM control signal; A MOSFET switch for controlling current output; An inductor and a filter capacitor for controlling current ripple and stabilizing the output voltage.

[0029] The self-canceling current source further includes an overload protection module for turning off the PWM control signal when the current or voltage exceeds a predetermined value to protect the circuit.

[0030] The self-canceling current source further includes a BUCK (step-down) power supply system with an input of 24V, an adjustable output current of 0A - 5A, and a switching frequency of 200kHz. The BUCK power supply system samples the output voltage through a 10kΩ / 1kΩ voltage division network and feeds it into the ADC sampling of the STM32F103C8T6 minimum system. The digital PID algorithm is used to calculate the correction amount in real time to achieve closed-loop feedback and PID regulation.

[0031] The ground-air frequency-domain electromagnetic detection background magnetic field real-time cancellation system further includes a carrying device 4, a towing rope 5, and a support platform 6; The carrying device 4 is connected to the solid wood frame storing the self-canceling control system 14 and the self-canceling current source through the towing rope 5 for carrying and transporting the entire cancellation system to the detection area; The support platform 6 is located inside the solid wood frame for placing the ground-air electromagnetic detection sensor.

[0032] The solid wood frame includes a solid wood support 17, solid wood support rods 8, and a solid wood flat panel 18. Among them, the solid wood support 17 and the solid wood support rods 8 are connected and fixed together by tying ropes (nylon cable ties). The solid wood flat panel 18 drills holes around the periphery close to the solid wood support 17, and the tying ropes pass through the holes and are fixed to the solid wood support 17. Each group of Helmholtz coils is fixedly connected to the solid wood support 17 through tying ropes to prevent electromagnetic interference caused by metals to the cancellation system. The solid wood support 17 is used to support the entire cancellation system, the solid wood support rods 8 connect each group of Helmholtz coils to assist in fixing, and the solid wood flat panel 18 is used to place the self-canceling control system 14 and the self-canceling current source.

[0033] A control method for the ground-air frequency-domain electromagnetic detection background magnetic field real-time cancellation system as described above includes the following steps: The attitude sensor 15 stores and records the three-dimensional attitude information of the entire cancellation system during the ground-air electromagnetic detection process and matches it with the geomagnetic field information measured by the three-component magnetic field sensor 13; The self-canceling control system 14 processes and analyzes the two kinds of information to obtain the magnitude information of the three-component geomagnetic field in different postures, and outputs three PWM (pulse width modulation) control signals corresponding to the cancellation of the three-component geomagnetic field; The self-canceling current source is regulated according to the PWM control signal, and appropriate DC canceling currents are applied to three sets of Helmholtz coils to generate a reverse magnetic field opposite to the direction of the geomagnetic field, realizing real-time cancellation of the three-component geomagnetic field in different postures.

[0034] The self-canceling control system 14 adopts a PID control algorithm to dynamically adjust the duty cycle of the PWM control signal, and ensures the stability of the current output through closed-loop feedback control.

[0035] The real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection of the present invention mainly includes a self-canceling transmitting coil, a self-canceling control system 14, and a self-canceling current source. The self-canceling transmitting coil uses three sets of Helmholtz coils, and each set of Helmholtz coils is perpendicular to each other. The three sets of Helmholtz coils are built into an approximate spherical shape. A solid wood frame made of solid wood is used to fix the three sets of Helmholtz coils, and at the same time store the self-canceling control system 14 and the self-canceling current source. The high-sensitivity three-component magnetic field sensor 13 and the attitude sensor 15 are fixed in the solid wood frame by tying ropes, and the azimuth of the three-component geomagnetic field measured by the three-component magnetic field sensor 13 corresponds to the three sets of Helmholtz coils respectively.

[0036] The self-canceling current source differentially collects and linearly steps down the voltage signals transmitted by the high-sensitivity three-component magnetic field sensor 13 and the attitude sensor 15. After processing and comparative analysis of these two analog signals, through the control method involved in the self-canceling control system 14, a PWM control signal with different duty cycles is pulse-modulated and output to the self-canceling current source module, thereby realizing closed-loop feedback control of the magnitude of the canceling current flowing into the self-canceling transmitting coil and realizing real-time cancellation of the magnetic field.

[0037] Embodiment 1: The overall architecture and working mechanism of the real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection; As Figure 1 shown, it is the basic architecture of the real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection of the present invention. Through this cancellation system, three-component geomagnetic field cancellation is realized during ground-air electromagnetic detection. This cancellation system is used in test processes such as time-domain airborne electromagnetic signal reception and magnetic field detection, cancels the three-component geomagnetic field in space, reduces low-frequency noise during ground-air electromagnetic exploration, thereby reducing the influence of low-frequency noise on the survey results, realizes geomagnetic exploration of low-frequency signals, and realizes high-sensitivity exploration effects.

[0038] Figure 1Among them, coil two 9 and coil five 12 are a set of Helmholtz coils corresponding to the Z direction, coil one 7 and coil six 16 are a set of Helmholtz coils corresponding to the X direction, and coil three 10 and coil four 11 are a set of Helmholtz coils corresponding to the Y direction. Each set of Helmholtz coils is connected by wires to form a three - set Helmholtz coil model. The high - sensitivity three - component magnetic field sensor 13 and the attitude sensor 15 are fixed on the solid wood frame, and the attitudes of the three components are synchronized with the attitudes of the three - set Helmholtz coils. There are four identical solid wood brackets 17 as the support of the whole system to keep it isolated from the ground. The solid wood support rod 8 is the support of the three - set Helmholtz coils to prevent the three - set Helmholtz coils from deforming during the force - induced swing. The solid wood flat plate 18 is the support of the self - canceling current source and the self - canceling control system 14. The support platform 6 is used for placing the detection sensor during the ground - air electromagnetic detection. The towing rope 5 can lift the whole cancellation system, and the cancellation system can be taken into the air through the carrying device 4 to receive low - frequency signals. Among them, the carrying device 4 can be in the form of a drone or a helicopter.

[0039] As Figure 1 shown, the attitude sensor 15 is used to store and record the three - dimensional attitude information of the whole cancellation system during the ground - air electromagnetic detection. The three - dimensional attitude information is matched with the geomagnetic field information measured by the high - sensitivity three - component magnetic field sensor 13. As Figure 2 shown, the two kinds of information are processed and analyzed by the self - canceling control system 14 to obtain the magnitude information of the three - component geomagnetic field in different attitudes, and three - way control signals corresponding to the cancellation of the three - component geomagnetic field are output.

[0040] Figure 1 As shown, the three - set Helmholtz coils are used as magnetic field generators. After passing current, a uniform magnetic field region can be formed between two Helmholtz coils. The magnitudes of the three - component geomagnetic field measured by the high - sensitivity three - component magnetic field sensor 13, combined with the attitude signals measured by the attitude sensor 15, and through the processing of the self - canceling control system 14, output corresponding control signals to the self - canceling current source module, and then apply appropriate DC cancellation currents to the three - set Helmholtz coils respectively to achieve the cancellation of the magnitudes of the three - component geomagnetic field and form a geomagnetic - field - free region in the three - dimensional region in the middle of the three - set Helmholtz coils.

[0041] During the ground - air detection process, Figure 1 the attitude of the detection instrument placed on the support platform 6 in may change in real time, and the magnitudes of the geomagnetic field with respect to the three components on the support platform 6 also change in real time in different attitudes. Therefore, it is necessary to adjust the current magnitudes applied to the three - set Helmholtz coils respectively according to different attitude situations to achieve the cancellation of the three - component geomagnetism in different attitudes.

[0042] Embodiment 2: The structure and measurement output characteristics of the high - sensitivity three - component magnetic field sensor 13; AsFigure 4 As shown, a high-sensitivity three-component magnetic field sensor 13 is used for the cancellation system. The three-component magnetic field sensor 13 consists of a housing 1, a connecting part 2, and an interface 3. The connecting part 2 is used to connect the internal three-component magnetic field sensor 13, and corresponding voltage signals are output through the interface 3. The three-component magnetic field sensor 13 is a prior art and will not be elaborated here. Figure 4 The three-component magnetic field sensor 13 shown in [the figure] is only used to measure the magnitude of the three-component geomagnetic field. The magnetic field range measured by each magnetic field component is ±1000 μT, and corresponding ±10 V voltage magnitudes are output according to the measured magnetic field magnitude.

[0043] Embodiment 3: The collaborative work and closed-loop control process of the self-cancellation control system 14 and the self-cancellation current source; As Figure 2 shown, taking the STM32 model single-chip microcomputer minimum system as the self-cancellation control system 14, the entire single-chip microcomputer system collects the three-component magnetic field analog signals output by the three-component magnetic field sensor 13 and the attitude sensor 15 and linearly stepped down, as well as the current signals passed through Figure 1 the three groups of Helmholtz coils in [the figure]. After the current signals are analyzed and processed by the single-chip microcomputer minimum system and compared with the theoretical current magnitudes deduced from the three-component geomagnetic signals and three-dimensional attitude signals, the duty ratios of the three PWM control signals are controlled to be output, realizing the current closed-loop feedback output to the three groups of Helmholtz coils. The execution process of the cancellation system is to pass the analog signals of the X, Y, and Z components output by the high-sensitivity three-component magnetic field sensor 13 and the analog signals output by the attitude sensor 15 through Figure 3 the linear buck circuit module in [the figure] to linearly step down the range of 0 V - 3.3 V and output a stable power supply. Through Figure 2 the ADC function of the single-chip microcomputer control system, the three-component geomagnetic analog signals after linear buck and the current magnitude analog signals of the self-cancellation current source are collected. Through the DMA function of the single-chip microcomputer, the collected geomagnetic field analog signals are quickly transported and processed. Through the control program and PID algorithm, the sampled current magnitude analog signals are compared with the theoretical values, and the duty ratios of the output PWM control signals are continuously feedback corrected. The PWM control signals are enhanced and amplified through Figure 3 the drive circuit (IR2104 MOSFET drive chip) in [the figure], and the current output is controlled according to Figure 4 the switching operation of the MOSFET in the flowchart. Among them, according to Figure 3Flowchart: The current passes through the inductor L to achieve current ripple control and output a filter capacitor. If the current value exceeds the predetermined maximum current value, the system will intervene to protect the circuit from overcurrent damage. The output voltage (Vout) is monitored in real time. When the output voltage is too low or too high, the system will automatically adjust the PWM control signal according to the feedback information to further adjust the output voltage and current to ensure a stable output of the power supply. There is a deviation between the output voltage and the reference voltage value (Vref). Figure 2 In the microcontroller minimum system, the PID control algorithm will be started. According to the voltage deviation, the duty cycle of the PWM control signal will be adjusted to gradually stabilize the voltage at the predetermined target value. After PID adjustment, the duty cycle of the PWM control signal is precisely adjusted, and finally a constant current output is achieved. After the current is stabilized, the system automatically enters the standby state to maintain a constant output of voltage and current, ensuring the efficient operation of the system.

[0044] The entire self-canceling current source module adds overload protection. After the current and voltage are stabilized, the relevant protection mechanism will continue to monitor the system status. When an abnormal situation occurs, the system will promptly turn off the PWM control signal to avoid damage to the device and ensure that the device operates within a safe range. Among them, at the moment when the current or voltage exceeds the predetermined value, the self-canceling current source module will protect by controlling the output of the PWM control signal, cut off the transmission of the PWM control signal, and immediately stop the current output to prevent more serious damage to the system caused by overload. When an overload occurs, the self-canceling current source module will also issue a warning through the built-in alarm system with LED flashing and sound alarm. Then the self-canceling current source module will automatically record the detailed data of the overload event, including the occurrence time, overload current, voltage value, and duration, etc., providing a reference for subsequent maintenance and optimization.

[0045] When the overload state is lifted, the self-canceling current source module will gradually recover: The system sets a reasonable delay recovery mechanism, and will delay 1 to 5 seconds after the current and voltage are stabilized before restarting the PWM control signal to ensure that the system can resume normal operation in a safe state.

[0046] Influence of temperature change and countermeasures: The self-canceling current source module is equipped with a temperature sensor inside to monitor the temperature of the self-canceling current source module in real time. When the temperature exceeds the set safety threshold (85°C), the system will start over-temperature protection and cut off the PWM control signal to prevent the system from being damaged by overheating.

[0047] Influence of humidity change and countermeasures: The self-canceling current source module also has a humidity alarm function. When the humidity exceeds the set safety threshold, the system will automatically cut off the power output to avoid the possible influence of humidity change on the electronic components and circuit boards of the self-canceling current source module.

[0048] Example 4: Design Scheme and Protection Mechanism of BUCK Power Supply System; As Figure 3 shown, with the core objectives of an input of 24V, an adjustable output current of 0A - 5A, and a switching frequency of 200kHz, a set of efficient and reliable BUCK power supply systems was constructed. This power supply system adopts a hierarchical design concept, integrating hardware protection, digital control, and analog feedback. The specific implementation is as follows: At the power supply inlet, an N-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) reverse connection prevention circuit (D2810) is deployed. A 10kΩ voltage-dividing resistor is used to ensure stable gate voltage, and a π-type filter network composed of a 10μF electrolytic capacitor and a 0.1μF capacitor is used to effectively suppress input surges and high-frequency noise. When connected in reverse, the MOSFET automatically turns off, and the leakage current is less than 1μA, forming a double protection in cooperation with a 12V TVS tube. Based on Figure 2 the timer of the STM32F103C8T6 minimum system in Figure 2 generates a 200kHz basic PWM control signal, which is amplified by an IR2104 driver and then drives the high-side MOSFET (IRF540N). The power stage uses a 33uH shielded inductor and a 22uF low-ESR ceramic capacitor to achieve dynamic voltage regulation. The inductor ripple current is controlled within 0.8A to ensure efficient energy transfer in the CCM mode and realize control and power conversion. The output voltage is sampled by a 10kΩ / 1kΩ voltage-dividing network, and the output voltage signal is sent to

[0049] the ADC of the STM32F103C8T6 minimum system in

[0050] For the above reasons, the present invention has dynamic environmental adaptability, can track the transient changes of the three-component geomagnetic field in real time, create a three-dimensional space area without geomagnetic field, and can monitor and quickly respond to the three-component geomagnetic field in real time. Through precise reverse magnetic field generation, it can cancel the geomagnetic field in real time, eliminate the influence of low-frequency noise caused by the geomagnetic field in ground-air electromagnetic detection, and realize the measurement of high-sensitivity and low-noise electromagnetic signals, providing technical support for the reliable application of ground-air frequency domain detection technology.It should be noted that in the present invention, it should be understood that although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A real-time cancellation system for the background magnetic field of a ground-air frequency-domain electromagnetic detection, characterized in that, It includes a solid wood frame, a self-canceling transmitting coil, a self-canceling control system (14), and a self-canceling current source; The self-canceling transmitting coil is composed of three sets of Helmholtz coils. Each set of coils is perpendicular to each other and is used to generate a reverse magnetic field opposite to the direction of the three-component geomagnetic field; The three sets of Helmholtz coils are fixed on the solid wood frame, and the self-canceling control system (14) and the self-canceling current source are also stored on the solid wood frame; The three-component magnetic field sensor (13) and the attitude sensor (15) are fixed in the solid wood frame by tying ropes, and the azimuth of the three-component geomagnetic field measured by the three-component magnetic field sensor (13) corresponds to the three sets of Helmholtz coils respectively.

2. The real-time cancellation system for background magnetic field of the ground-air frequency-domain electromagnetic detection according to claim 1, wherein The self-canceling current source is used to differentially collect and linearly step down the voltage signals transmitted by the three-component magnetic field sensor (13) and the attitude sensor (15). After processing and comparative analysis, it is regulated by the control method in the self-canceling control system (14), and a PWM control signal with different duty cycles is output to the self-canceling current source module to closed-loop feedback control the magnitude of the canceling current flowing to the self-canceling transmitting coil.

3. The real-time cancellation system for background magnetic field of the ground-air frequency-domain electromagnetic detection according to claim 1, wherein The self-canceling control system (14) takes the single-chip microcomputer minimum system as the core, collects the three-component magnetic field analog signals output by the three-component magnetic field sensor (13) and the attitude sensor (15) and linearly stepped down, as well as the current signals passed through the three sets of Helmholtz coils. After analysis and processing and comparison with the theoretical current magnitude, it controls the duty cycle of the output of the three-way PWM control signal to achieve closed-loop feedback of the current output to the three sets of Helmholtz coils.

4. The real-time background magnetic field cancellation system for ground-air frequency domain electromagnetic detection according to claim 1, characterized in that The three-component magnetic field sensor (13) is composed of a housing (1), a connecting part (2), and an interface (3). The magnetic field range measured by each magnetic field component is ±1000 μT, and a voltage of ±10 V is output corresponding to the measured magnetic field magnitude.

5. The real-time cancellation system for background magnetic field of ground-air frequency-domain electromagnetic detection according to claim 1, characterized in that, Among the three sets of Helmholtz coils, coil two (9) and coil five (12) are a set of Helmholtz coils corresponding to the Z direction, coil one (7) and coil six (16) are a set of Helmholtz coils corresponding to the X direction, and coil three (10) and coil four (11) are a set of Helmholtz coils corresponding to the Y direction. Each set of Helmholtz coils is connected by wires.

6. The real-time cancellation system for background magnetic field of ground-air frequency-domain electromagnetic detection according to claim 2, wherein The self-canceling current source includes: A linear step-down circuit module for stepping down the input analog signal to the range of 0 V to 3.3 V; A drive circuit that uses an IR2104 MOSFET drive chip to amplify the PWM control signal; A MOSFET switch for controlling current output; An inductor and a filter capacitor for controlling current ripple and stabilizing the output voltage.

7. The real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection according to claim 6, characterized in that, The self-canceling current source also includes an overload protection module for turning off the PWM control signal when the current or voltage exceeds a predetermined value to protect the circuit.

8. The real-time cancellation system for background magnetic field of ground-air frequency-domain electromagnetic detection according to claim 1, characterized in that, The real-time cancellation system for the background magnetic field of the ground-air frequency-domain electromagnetic detection also includes a carrying device (4), a towing rope (5), and a support platform (6); The carrying device (4) is connected to the solid wood frame storing the self-canceling control system (14) and the self-canceling current source through the towing rope (5) and is used to carry and transport the entire cancellation system to the detection area; The support platform (6) is located inside the solid wood frame and is used to place the ground-air electromagnetic detection sensor.

9. The real-time background magnetic field cancellation system for ground-air frequency-domain electromagnetic detection according to claim 1, wherein The solid wood frame includes a solid wood support (17), solid wood support rods (8) and a solid wood flat panel (18). The solid wood support (17) is used to support the entire cancellation system. The solid wood support rods (8) are connected to each group of Helmholtz coils to assist in fixing. The solid wood flat panel (18) is used to place the self-cancellation control system (14) and the self-cancellation current source.

10. A control method for a real-time cancellation system of the background magnetic field of a ground-air frequency-domain electromagnetic detection, as described in any one of claims 1-9, characterized in that, It includes the following steps: The attitude sensor (15) stores and records the three-dimensional attitude information of the entire cancellation system during the ground-air electromagnetic detection process, and matches it with the geomagnetic field information measured by the three-component magnetic field sensor (13); The self-cancellation control system (14) processes and analyzes the two kinds of information to obtain the three-component geomagnetic field magnitude information in different attitudes, and outputs three-way PWM control signals corresponding to the cancellation of the three-component geomagnetic field; The self-cancellation current source is regulated according to the PWM control signal, and a suitable DC cancellation current is passed through the three groups of Helmholtz coils to generate a reverse magnetic field opposite to the direction of the geomagnetic field, realizing the real-time cancellation of the three-component geomagnetic field in different attitudes.

Images