Area-compensated three-component electromagnetic coil coupling optimization method and device

Abstract

The present application relates to the field of aviation geophysical prospecting technology, and more particularly to an area compensation three-component electromagnetic coil coupling optimization method and device, the method comprising: constructing a multi-winding differential cross type area compensation structure according to the aviation detection environment, using the difference in the projected area of the sub-coil to offset the jitter-induced noise; constructing a multi-stage shock absorption structure and setting a spring compression constraint to establish a vibration grading suppression mechanism; integrating a built-in correction excitation coil to inject a sweep signal, calculating the complex transfer function and sensitivity drift coefficient to obtain the characteristic test results; constructing a coupling matrix to calculate the orthogonality error and generating adjustment parameters to be fed back to the hardware for correction. The present application combines hardware structure optimization and dynamic correction, effectively suppresses the vibration noise, solves the problems of sensitivity drift and coil non-orthogonal coupling, and realizes low-noise and high-precision measurement of aviation electromagnetic detection.

Description

Technical Field

[0001] This invention relates to the field of airborne geophysical exploration technology, and in particular to a method and apparatus for optimizing the coupling of three-component electromagnetic coils with area compensation. Background Technology

[0002] Helicopter time-domain airborne electromagnetic detection technology is an important geophysical exploration method. Its principle is to emit a pulse electromagnetic field downward to excite the underground medium to generate an induced electromagnetic field (i.e., a secondary field), and then use a high-sensitivity three-component electromagnetic coil sensor to sense the secondary field information, thereby inferring the conductivity distribution of the underground medium.

[0003] In practical applications, the coil of a high-sensitivity three-component electromagnetic sensor is highly susceptible to mechanical vibrations from the pod during flight. These vibrations cause attitude changes in the coil, specifically manifested as a superimposed combination of low-frequency, large-amplitude attitude changes (which occur as the pod oscillates) and high-frequency, small-amplitude attitude changes. When the coil undergoes attitude changes in the Earth's magnetic field, it cuts magnetic lines of force, generating an induced electromotive force that creates noise that is confused with the target signal, severely impacting measurement accuracy.

[0004] To address the aforementioned vibration and noise issues, existing noise reduction solutions typically employ attitude sensors to measure and compensate for attitude changes caused by the significant swaying of the pod system. However, for induced noise generated by the high-frequency, minute vibrations of the coils, installing attitude sensors within the limited coil space may interfere with the weak secondary field signal, making it impossible to accurately measure parameters such as vibration amplitude and frequency. Therefore, current technologies mainly rely on filtering or purely software compensation methods to eliminate this type of noise. These methods have significant limitations: firstly, they do not involve in-depth research and suppression of vibration at the system hardware design level; secondly, they are prone to loss of measurement information, making it extremely difficult to measure coil induced signals below 1 nT / s.

[0005] Furthermore, traditional three-component coil designs often do not consider the design scheme of built-in correction excitation coils, which makes it impossible to measure and correct parameters such as orthogonality and angle consistency of the wound coils online. At the same time, it is also impossible to measure key parameters such as the transfer function of the three-component coils in real time under dynamic flight conditions, thus limiting the further improvement of sensor accuracy. Summary of the Invention

[0006] Therefore, the present invention provides a three-component electromagnetic coil coupling optimization method and apparatus with area compensation to solve the aforementioned problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides an area-compensated three-component electromagnetic coil coupling optimization method, comprising:

[0008] Step S1: Obtain the jitter noise suppression requirements based on the flight environment parameters of the aerial reconnaissance. By constructing a multi-winding differential cross-type area compensation structure, the difference in the projected area of ​​the sub-induction coil pairs is used to cancel the induced noise in order to obtain the noise suppression result.

[0009] Step S2: Based on the noise suppression results, construct a multi-level vibration reduction structure and set the compression ratio constraint of the spring pair to establish a graded vibration suppression mechanism to obtain the vibration suppression results.

[0010] Step S3: Based on the vibration suppression results, the complex transfer function and sensitivity drift coefficient of the coil are calculated by integrating the built-in correction excitation coil and injecting a sweep frequency excitation signal to obtain the characteristic test results.

[0011] Step S4: Construct a coupling matrix based on the characteristic test results and calculate the orthogonality error, generate adjustment parameters and feed them back to the hardware structure to obtain the coupling correction results.

[0012] Furthermore, the process of step S1 includes:

[0013] A three-component electromagnetic coil assembly is constructed, wherein the induction coil of each component adopts a differential structure with symmetrical upper and lower parts. The differential structure consists of a positive induction coil and a negative induction coil, both of which contain an even number of sub-induction coil pairs.

[0014] The sub-induction coils are placed in a crosswise manner, and the inclination angle between the coil plane and the horizontal plane is set to θ. During the jittering process, when the horizontal projected area of ​​one sub-coil decreases, the horizontal projected area of ​​the other sub-coil paired with it increases. The difference in the change of the projected area between the two sub-coils is used to offset the change in magnetic flux.

[0015] Furthermore, the optimization process of setting the inclination angle θ between the coil plane and the horizontal plane includes:

[0016] Based on the vibration amplitude and frequency of the coil, select the optimal tilt angle that minimizes the difference in projected area; or, for dynamic environments where the vibration tilt angle is uncertain, configure two sets of cross-type sub-coil pairs that deflect by an angle θ with the orthogonal diameter of the coil as the axis.

[0017] Furthermore, the process of constructing a multi-level damping structure based on the noise suppression result and setting compression ratio constraints for the spring pairs includes:

[0018] A multi-stage damping structure comprising a pair of vertical non-magnetic springs is constructed, wherein the pair of vertical non-magnetic springs is composed of a bottom support spring, a coil horizontal bracket, and a top limiting spring connected in sequence;

[0019] The vertical non-magnetic spring pairs are evenly arranged along the circumference of the horizontal coil in the three-component electromagnetic induction coil;

[0020] Perform spring preload operation to control the compression amplitude of the bottom support spring to not exceed 1 / 3 of its maximum compression amplitude, and at the same time control the compression amplitude of the top limit spring to not exceed 1 / 4 of its maximum compression amplitude.

[0021] Furthermore, the process of establishing a graded vibration suppression mechanism to obtain vibration suppression results includes:

[0022] Based on the vibration frequency distribution experienced by the coil in the airborne detection flight environment, the vibration is divided into a low-frequency large-amplitude segment and a high-frequency small-amplitude segment.

[0023] By selecting the stiffness and pre-compression of the bottom support spring, its natural frequency is made lower than the center frequency of the low-frequency band, so as to perform first-level attenuation of low-frequency large-amplitude vibrations.

[0024] By selecting the stiffness and pre-compression of the top limiting spring, it forms a displacement constraint on the high-frequency micro-amplitude vibration of the coil, thus achieving secondary vibration reduction.

[0025] An elastic buffer layer is installed on the inner wall of the installation chamber to absorb residual high-frequency vibration energy using its damping characteristics.

[0026] The vibration suppression result is obtained by combining the first-level attenuation, the second-level vibration reduction, and the residual high-frequency vibration energy.

[0027] Furthermore, the process of step S3 includes:

[0028] An integrated correction excitation coil is incorporated inside the frame of the three-component electromagnetic induction coil.

[0029] Inject a sweep frequency excitation current signal into the correction excitation coil;

[0030] The output voltage signal of the induction coil is acquired, and the complex transfer function of the output voltage signal and the sweep frequency excitation current signal is calculated.

[0031] The sensitivity drift coefficient is calculated based on the amplitude-frequency characteristic change of the complex transfer function, and the characteristic test result is obtained by combining the complex transfer function and the sensitivity drift coefficient.

[0032] Furthermore, the process of calculating the sensitivity drift coefficient based on the amplitude-frequency characteristic change of the complex transfer function, and obtaining the characteristic test result by combining the complex transfer function and the sensitivity drift coefficient, includes:

[0033] The amplitude response value of the complex transfer function at the target frequency point is extracted as the measured sensitivity.

[0034] Obtain the pre-stored reference sensitivity, calculate the relative deviation of the measured sensitivity relative to the reference sensitivity, and obtain the sensitivity drift coefficient;

[0035] The sensitivity drift coefficient is compared with a preset drift threshold to obtain a comparison result;

[0036] The characteristic test results are generated by combining the amplitude-frequency curve data of the complex transfer function with the comparison results.

[0037] Furthermore, the process of step S4 includes:

[0038] Based on the complex transfer function data in the characteristic test results, calculate the mutual inductance coupling coefficient between any two axes of the three-component coil to construct a three-dimensional coupling matrix.

[0039] The orthogonality error is obtained by solving for the deviation of the off-diagonal elements of the three-dimensional coupling matrix relative to zero.

[0040] The required mechanical displacement compensation or electrical signal correction coefficient is calculated based on the orthogonality error and used as the adjustment parameter.

[0041] The adjustment parameters are fed back to the mechanical adjustment structure of the coil or the signal acquisition circuit to perform a correction operation and obtain the coupling correction result.

[0042] Furthermore, the process of calculating the required mechanical displacement compensation or electrical signal correction coefficient based on the orthogonality error as the adjustment parameter includes:

[0043] The orthogonality error is compared with a preset mechanical correction threshold;

[0044] When the orthogonality error exceeds the mechanical correction threshold, the required mechanical displacement compensation for the coil frame is calculated using the orthogonal projection algorithm as an adjustment parameter.

[0045] When the orthogonality error does not exceed the mechanical correction threshold, the gain correction coefficient and zero offset of the signal acquisition channel are calculated as adjustment parameters according to the error compensation formula.

[0046] On the other hand, the present invention also provides an area-compensated three-component electromagnetic coil coupling optimization device, comprising:

[0047] The three-component electromagnetic induction coil assembly is disposed inside the mounting chamber and includes a coil frame and an induction coil wound on the coil frame.

[0048] The vibration suppression mechanism includes a bottom support spring, a top limiting spring, an elastic buffer layer, and a coil horizontal bracket; the coil horizontal bracket is disposed between the bottom support spring and the top limiting spring; the coil frame is fixedly connected to the coil horizontal bracket; the bottom support spring is connected between the bottom surface of the mounting chamber and the coil horizontal bracket; the top limiting spring is connected between the top surface of the mounting chamber and the coil horizontal bracket; the elastic buffer layer is disposed in the gap between the coil horizontal bracket and the mounting chamber.

[0049] The characteristic testing mechanism includes a built-in correction excitation coil, which is coaxially wound on the inner side of the coil frame and used to inject a sweep frequency excitation current signal.

[0050] The coupling correction mechanism includes a control processing unit and a mechanical adjustment structure; the signal output terminal of the control processing unit is electrically connected to the correction excitation coil, and the signal input terminal of the control processing unit is electrically connected to the induction coil; the mechanical adjustment structure is disposed between the coil frame and the mounting chamber, and is connected to the control terminal of the control processing unit.

[0051] Compared with the prior art, the beneficial effects of this invention are as follows: By constructing a multi-winding differential cross-type area compensation structure, this invention utilizes the geometric characteristics of the opposite directions of the projected area change of the sub-induction coil pairs during vibration deflection, so that the induced noise cancels each other out during the differential process, cutting off the path from the physical source of vibration attitude change to magnetic flux change noise; combined with the specific compression ratio constraint of the spring in the multi-stage damping structure, it ensures that the elastic support always works in the linear stable range, effectively isolating and attenuating external mechanical vibration energy, and reducing the amplitude of coil attitude jitter; at the same time, by using the built-in excitation coil to inject a sweep frequency signal to determine the complex transfer function, a precise mapping relationship between the excitation magnetic field and the induced voltage response is established, and the orthogonality error feedback calculated based on the coupling matrix drives mechanical adjustment or electrical compensation, eliminating non-orthogonal crosstalk between the three component coils, thereby achieving sub-nT / s level low-noise and high-precision airborne electromagnetic detection. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating the area-compensated three-component electromagnetic coil coupling optimization method described in this invention.

[0053] Figure 2 This is a schematic diagram of the design of the cross-type sub-induction coil pair in the area-compensated three-component electromagnetic coil coupling optimization method described in this invention;

[0054] Figure 3 This is a schematic diagram of the area compensation for the jitter state of the cross-type induction coil in the three-component electromagnetic coil coupling optimization method with area compensation described in this invention.

[0055] Figure 4 This is a schematic diagram of the structure of the area-compensated three-component electromagnetic coil coupling optimization device described in this invention;

[0056] Figure 5 A schematic diagram of the vibration suppression mechanism provided in this embodiment of the invention;

[0057] Reference numerals in the attached diagram: 1. Coil frame; 2. Induction coil; 3. Bottom support spring; 4. Top limiting spring; 5. Elastic buffer layer; 6. Horizontal coil bracket; 7. Vertical non-magnetic spring pair; 8. Correction excitation coil. Detailed Implementation

[0058] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0059] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0060] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0061] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0062] Please see Figure 1 As shown, the present invention provides an area-compensated three-component electromagnetic coil coupling optimization method, comprising:

[0063] Step S1: Obtain the jitter noise suppression requirements based on the flight environment parameters of the aerial reconnaissance. By constructing a multi-winding differential cross-type area compensation structure, the difference in the projected area of ​​the sub-induction coil pairs is used to cancel the induced noise in order to obtain the noise suppression result.

[0064] Specifically, step S1 includes the following process:

[0065] A three-component electromagnetic coil assembly is constructed, wherein the induction coil of each component adopts a differential structure with symmetrical upper and lower parts. The differential structure consists of a positive induction coil and a negative induction coil, both of which contain an even number of sub-induction coil pairs.

[0066] Specifically, a three-component electromagnetic coil assembly is constructed. Each component's induction coil employs a symmetrical differential structure. The differential structure consists of a positive induction coil and a negative induction coil, electrically connected in series with opposite polarities. Each of the positive and negative induction coils contains an even number of sub-induction coil pairs to ensure structural symmetry.

[0067] The sub-induction coils are placed in a crosswise manner, and the inclination angle between the coil plane and the horizontal plane is set to θ. During the jittering process, when the horizontal projected area of ​​one sub-coil decreases, the horizontal projected area of ​​the other sub-coil paired with it increases. The difference in the change of the projected area between the two sub-coils is used to offset the change in magnetic flux.

[0068] Specifically, the spatial layout of the sub-induction coil pairs is configured. The sub-induction coil pairs are placed in a cross-position, and the tilt angle between the coil plane and the horizontal plane is set to θ. The tilt angle θ refers to the angle between the normal direction of the sub-coil plane and the vertical direction (the direction of gravity). With this layout, when the coil assembly is affected by external vibrations and its attitude deflects, the effective horizontal projected area of ​​one sub-coil in the sub-induction coil pair decreases, while the effective horizontal projected area of ​​its paired sub-coil increases accordingly. Since the positive and negative induction coils are connected in series with opposite polarities, the changes in induced electromotive force caused by the change in projected area cancel each other out. Therefore, the difference in projected area is used to offset the change in magnetic flux, achieving noise suppression.

[0069] Specifically, the optimization process of setting the inclination angle θ between the coil plane and the horizontal plane includes:

[0070] Based on the vibration amplitude and frequency of the coil, select the optimal tilt angle that minimizes the difference in projected area, or for dynamic environments where the vibration tilt angle is uncertain, configure two sets of cross-type sub-coil pairs that deflect by an angle θ with the orthogonal diameter of the coil as the axis.

[0071] Specifically, for steady-state flight environments where vibration parameters are predictable, a projected area change model is established based on the coil's vibration amplitude and frequency. By solving this model, the angle that minimizes the difference in projected area change is selected as the optimal tilt angle θ. The vibration amplitude refers to the maximum angular displacement of the coil from its equilibrium position, and the vibration frequency refers to the number of times the coil oscillates per unit time. The optimal tilt angle θ is typically set between 2° and 10°, with the specific value determined based on actual airborne reconnaissance flight environment parameters to obtain the best noise suppression ratio under specific conditions. In this embodiment, the optimal tilt angle is 4°. Alternatively, for dynamic environments where the vibration tilt angle change is uncertain, a bidirectional symmetrical deflection structure is used for compensation. Specifically, two sets of cross-type sub-coil pairs are configured, deflecting in opposite directions by an angle θ with the coil's orthogonal diameter as the axis. This structure achieves omnidirectional coverage compensation for attitude jitter in any direction through bidirectional symmetrical area change redundancy, ensuring stable noise suppression even in dynamic environments.

[0072] Specifically, assuming all sub-induction coils are arranged in parallel, and the Z-component plane of the differential coil is tilted at a fixed angle θ to the horizontal plane, the three-component coils will experience vibration and displacement due to wind resistance during flight. The coil displacement angle is φ. The induction coil sensor measures the derivative of the magnetic field with respect to time, and the voltage induced by the coil is:

[0073]

[0074] Where S is the projected area perpendicular to the direction of the magnetic field.

[0075] When the sub-coils are all placed in parallel, the difference in the equivalent effective area of ​​the coils during the jittering process is:

[0076]

[0077] When the sub-induction coil pairs contained in the positive and negative induction coils are placed in a crisscross pattern, each pair of sub-induction coils forms a crisscross sub-induction coil pair. If the coil jitters at an angle φ during flight, then the equivalent effective area difference during the jitter process is:

[0078]

[0079] Therefore, the ratio of the relative difference in the equivalent effective area of ​​the coils under parallel and intersecting placement conditions is obtained as follows:

[0080]

[0081] Specifically, Figure 2 This is a schematic diagram of the structure of a cross-type sub-induction coil pair. Figure 3 yes Figure 2When the cross-type sub-induction coil pair deflects at an angle along the X-axis, the projected area of ​​the two sub-coils on the horizontal plane changes. When the horizontal projected area of ​​one sub-coil decreases, the horizontal projected area of ​​the other sub-coil increases. The change in the horizontal projected area of ​​the overall coil is the difference between the changes in the projected areas of the two sub-coils. This is far superior to the design of the parallel sub-induction coil pair, where the change in projected area is the sum of the changes in the areas of the two sub-coils under the same vibration conditions. This results in a coil sensor design with anti-vibration offset characteristics.

[0082] Step S2: Based on the noise suppression results, construct a multi-level vibration reduction structure and set the compression ratio constraint of the spring pair to establish a graded vibration suppression mechanism to obtain the vibration suppression results.

[0083] Specifically, the process of constructing a multi-level damping structure based on the noise suppression results and setting compression ratio constraints for the spring pairs includes:

[0084] A multi-stage damping structure comprising a pair of vertical non-magnetic springs is constructed, wherein the pair of vertical non-magnetic springs is composed of a bottom support spring, a coil horizontal bracket, and a top limiting spring connected in sequence;

[0085] Specifically, the coil horizontal bracket is used to fix and support the three-component electromagnetic induction coil, the bottom support spring is connected between the bottom of the bracket and the mounting base, and the top limiting spring is connected between the top of the bracket and the top cover of the mounting compartment, forming a bidirectional elastic constraint structure that is symmetrical from top to bottom.

[0086] The vertical non-magnetic spring pairs are evenly arranged along the circumference of the horizontal coil in the three-component electromagnetic induction coil;

[0087] Specifically, the number of vertical non-magnetic spring pairs is determined according to the total weight of the coil assembly. In this embodiment, it is preferably 8 pairs, which are evenly arranged along the circumferential direction of the horizontal coil in the three-component electromagnetic induction coil to ensure mechanical balance.

[0088] Perform spring preload operation to control the compression amplitude of the bottom support spring to not exceed 1 / 3 of its maximum compression amplitude, and at the same time control the compression amplitude of the top limit spring to not exceed 1 / 4 of its maximum compression amplitude.

[0089] Specifically, the preload compression amplitude ranges from 15% to 33% of the maximum compression amplitude. In this embodiment, the maximum compression amplitude of the bottom support spring is designed to be 30mm, and its actual preload compression is set to 10mm. This threshold ensures, on the one hand, that the bottom support spring has sufficient preload to bear the weight of the coil assembly, preventing the coil from detaching from the mounting base under static or low-frequency bumpy conditions; on the other hand, it reserves sufficient travel margin (20mm remaining travel in this embodiment) as a "dynamic buffer zone" to ensure that the spring is not compressed when encountering large low-frequency impacts, thereby maintaining the linearity of the stiffness characteristics. The preload compression amplitude of the top limit spring is set not to exceed 1 / 4 of its maximum compression amplitude. The preload compression amplitude ranges from 5% to 25% of the maximum compression amplitude. In this embodiment, the maximum compression amplitude of the top limit spring is designed to be 20mm, and its actual preload compression is set to 5mm. Under normal flight conditions with minor vibrations, the top limiting spring is in a low preload state and does not interfere with the main shock absorption function of the bottom support spring. When the coil is subjected to a severe impact and causes upward displacement, the top limiting spring intervenes to provide a reverse constraint force and play a flexible limiting protection role.

[0090] Specifically, the process of establishing a graded vibration suppression mechanism to obtain vibration suppression results includes:

[0091] Based on the vibration frequency distribution experienced by the coil in the airborne detection flight environment, the vibration is divided into a low-frequency large-amplitude segment and a high-frequency small-amplitude segment.

[0092] Specifically, based on the vibration frequency distribution characteristics experienced by the coil in an aerial reconnaissance flight environment, the vibration spectrum is divided into a low-frequency large-amplitude band and a high-frequency small-amplitude band. The frequency range of the low-frequency large-amplitude band is typically 0.5Hz to 10Hz, and the frequency range of the high-frequency small-amplitude band is typically 10Hz to 100Hz. In this embodiment, for an aerial reconnaissance environment of a certain type of helicopter, the measured center frequency of the low-frequency large-amplitude band is approximately 2Hz, and the center frequency of the high-frequency small-amplitude band is approximately 50Hz.

[0093] By selecting the stiffness and pre-compression of the bottom support spring, its natural frequency is made lower than the center frequency of the low-frequency band, so as to perform first-level attenuation of low-frequency large-amplitude vibrations.

[0094] Specifically, based on the single-degree-of-freedom vibration isolation theory, the stiffness coefficient of the bottom support spring is selected. The pre-compression amount causes the natural frequency of the vibration system consisting of the coil assembly mass m and the bottom support spring to be determined. Below the center frequency of the low-frequency large amplitude band The preferred design range for the natural frequency is 0.5 to 0.7 times the center frequency of the low-frequency large-amplitude band. In this embodiment, the natural frequency of the system is set to 1 Hz (satisfying ( Correspondingly, the stiffness coefficient of the bottom support spring is determined according to the formula. Calculations show that the value typically ranges from 200 N / m to 1000 N / m. In this embodiment, the coil assembly weighs 7 kg. The stiffness coefficient is calculated and selected accordingly. The value is 400 N / m. By setting this parameter, the energy storage characteristics of the spring's deformation are utilized to isolate the transmission of low-frequency, large-amplitude vibrations.

[0095] By selecting the stiffness and pre-compression of the top limiting spring, it forms a displacement constraint on the high-frequency micro-amplitude vibration of the coil, thus achieving secondary vibration reduction.

[0096] Specifically, the stiffness coefficient of the top limiting spring is selected. Construct a displacement constraint mechanism. The stiffness coefficient of the top limiting spring. The value range is usually the bottom support spring stiffness. This is 2 to 5 times that of [other components], i.e., 800 N / m to 2000 N / m. In this embodiment, [the following is selected]. The value is 1500 N / m. Due to its high stiffness and small preload, when high-frequency micro-vibration attempts to drive the coil to produce displacement, the top limiting spring quickly generates an elastic reaction force to suppress the displacement amplitude, preventing the micro-vibration from superimposed resonance and achieving secondary vibration reduction.

[0097] An elastic buffer layer is installed on the inner wall of the installation chamber to absorb residual high-frequency vibration energy using its damping characteristics.

[0098] Specifically, an elastic buffer layer made of a high-damping viscoelastic material (such as butyl rubber or polyurethane foam) is attached to the inner wall of the installation chamber. The thickness of the elastic buffer layer ranges from 5 mm to 20 mm, and the damping loss factor ranges from 0.1 to 0.4. In this embodiment, a 10 mm thick butyl rubber layer is selected, with a damping loss factor of 0.25. When residual vibration waves are transmitted to the chamber wall, the internal friction characteristics of the elastic buffer layer are used to convert the mechanical energy of the residual high-frequency micro-amplitude vibration into heat energy for dissipation.

[0099] The vibration suppression result is obtained by combining the first-level attenuation, the second-level vibration reduction, and the residual high-frequency vibration energy.

[0100] Step S3: Based on the vibration suppression results, the complex transfer function and sensitivity drift coefficient of the coil are calculated by integrating the built-in correction excitation coil and injecting a sweep frequency excitation signal to obtain the characteristic test results.

[0101] Specifically, step S3 includes the following process:

[0102] An integrated correction excitation coil is incorporated inside the frame of the three-component electromagnetic induction coil.

[0103] Specifically, the correction excitation coil is made of non-magnetic high-resistance wire and is coaxially arranged with the induction coil to generate a standard excitation magnetic field.

[0104] Inject a sweep frequency excitation current signal into the correction excitation coil;

[0105] Specifically, the frequency range of the frequency sweep excitation current signal covers the target frequency band for airborne detection, typically ranging from 10Hz to 10kHz. In this embodiment, for low-frequency airborne detection requirements, the frequency sweep range is set to 10Hz to 5kHz. The amplitude of the excitation current must ensure that the generated magnetic field signal has a moderate signal-to-noise ratio and does not cause magnetic saturation. The current amplitude typically ranges from 1mA to 50mA. In this embodiment, the constant current source output amplitude is set to 10mA. This signal is frequency swept in steps with a preset time step or logarithmic interval.

[0106] The output voltage signal of the induction coil is acquired, and the complex transfer function of the output voltage signal and the sweep frequency excitation current signal is calculated.

[0107] Specifically, the complex transfer function Defined as the spectrum of the output voltage signal of the induction coil Spectrum of excitation current signal The ratio of amplitude and phase response is a function that contains information about both the amplitude and phase response, reflecting the dynamic characteristics of the coil system.

[0108] The sensitivity drift coefficient is calculated based on the amplitude-frequency characteristic change of the complex transfer function, and the characteristic test result is obtained by combining the complex transfer function and the sensitivity drift coefficient.

[0109] Specifically, the process of calculating the sensitivity drift coefficient based on the amplitude-frequency characteristic change of the complex transfer function, and obtaining the characteristic test result by combining the complex transfer function and the sensitivity drift coefficient includes:

[0110] The amplitude response value of the complex transfer function at the target frequency point is extracted as the measured sensitivity.

[0111] Specifically, the amplitude response value of the complex transfer function at the target frequency point is extracted as the measured sensitivity. The target frequency point is the main operating frequency or characteristic frequency of the airborne detection. The value range of the target frequency point is typically from 100Hz to 2kHz. In this embodiment, 500Hz is selected as the target frequency point. .

[0112] Obtain the pre-stored reference sensitivity, calculate the relative deviation of the measured sensitivity relative to the reference sensitivity, and obtain the sensitivity drift coefficient;

[0113] Specifically, the pre-stored reference sensitivity is obtained. The reference sensitivity refers to the transfer function amplitude value measured under standard static conditions or during factory calibration, and is stored in the non-volatile memory of the control processing unit. The measured sensitivity is then calculated. Relative to reference sensitivity The relative deviation is used to obtain the sensitivity drift coefficient η: .

[0114] The sensitivity drift coefficient is compared with a preset drift threshold to obtain a comparison result;

[0115] Specifically, the preset drift threshold is used to determine whether the coil system has failed due to vibration, shock, or temperature drift. The drift threshold ranges from 1% to 5%. If the drift coefficient exceeds this threshold, it indicates that the physical structure of the coil (such as turn spacing and frame position) has undergone irreversible deformation or relative displacement, resulting in a change in the magnetic flux integral area, and the sensor accuracy has exceeded the allowable error range. The drift threshold serves as the basis for triggering automatic correction or fault alarm. In this embodiment, considering the high-precision detection requirements, the drift threshold is set to 2%. When the calculated η > 2%, the test result is determined to be "abnormal," and subsequent correction steps need to be performed; when η ≤ 2%, the test result is determined to be "normal."

[0116] The characteristic test results are generated by combining the amplitude-frequency curve data of the complex transfer function with the comparison results.

[0117] Specifically, the characteristic test results are generated by combining the amplitude-frequency curve data of the complex transfer function with the comparison results. The amplitude-frequency curve data is used to analyze the resonant point and bandwidth of the coil in the high-frequency range, and the comparison results are used to characterize the current health status of the coil sensitivity. The two are combined to form a complete characteristic test report.

[0118] Step S4: Construct a coupling matrix based on the characteristic test results and calculate the orthogonality error, generate adjustment parameters and feed them back to the hardware structure to obtain the coupling correction results.

[0119] Specifically, step S4 includes the following process:

[0120] Based on the complex transfer function data in the characteristic test results, calculate the mutual inductance coupling coefficient between any two axes of the three-component coil to construct a three-dimensional coupling matrix.

[0121] The control processing unit controls the built-in correction excitation coils to sequentially apply standard excitation signals to the X, Y, and Z axes, and acquires the output voltage amplitude of the induction coils on each axis. (Definition) The transfer function amplitude of the i-axis induction coil is calculated when the excitation is applied in the j-axis direction. The normalized mutual inductance coupling coefficient is then calculated. (where i ≠ j), thus constructing the three-dimensional coupling matrix M:

[0122]

[0123] Among them, the diagonal elements represent the reference sensitivity of each axis, and the off-diagonal elements represent the inter-axis coupling strength, reflecting the degree of deviation of the coil orthogonality.

[0124] The orthogonality error is obtained by solving for the deviation of the off-diagonal elements of the three-dimensional coupling matrix relative to zero.

[0125] Specifically, since the off-diagonal elements of an ideal orthogonal system should be zero, the actual measured absolute values ​​of the off-diagonal elements... This is defined as orthogonality error.

[0126] The required mechanical displacement compensation or electrical signal correction coefficient is calculated based on the orthogonality error and used as the adjustment parameter.

[0127] Specifically, the process of calculating the required mechanical displacement compensation or electrical signal correction coefficient based on the orthogonality error as the adjustment parameter includes:

[0128] The orthogonality error is compared with a preset mechanical correction threshold;

[0129] Specifically, the preset mechanical correction threshold is used to determine whether the deformation of the coil's physical structure exceeds the effective range of electrical compensation. The mechanical correction threshold ranges from 0.01 to 0.05 (i.e., 1% to 5%). This indicates that when the coupling coefficient exceeds this value, it means that the coil frame has undergone significant physical displacement or tilting due to vibration and impact, resulting in a change in the magnetic flux integral area. In this case, electrical correction alone will cause a severe loss of signal dynamic range. In this embodiment, the mechanical correction threshold is set to 0.02 (2%).

[0130] When the orthogonality error exceeds the mechanical correction threshold, the required mechanical displacement compensation for the coil frame is calculated using the orthogonal projection algorithm as an adjustment parameter.

[0131] Specifically, based on geometric projection relationships, the orthogonality error is... Mapped to the tilt angle deviation of the coil frame By combining the transmission ratio of the mechanical adjustment structure (such as the stepper motor pitch or piezoelectric ceramic stroke ratio), the required linear displacement ΔL of the mechanical adjustment structure is calculated. The accuracy control range of the mechanical displacement compensation amount needs to be better than 0.1mm. In this embodiment, the control processing unit generates a control command containing the displacement ΔL and sends it to the mechanical adjustment structure to drive the coil frame to fine-tune its attitude until the orthogonality error drops below the threshold.

[0132] When the orthogonality error does not exceed the mechanical correction threshold, the gain correction coefficient and zero offset of the signal acquisition channel are calculated according to the error compensation formula as adjustment parameters.

[0133] Specifically, the gain correction coefficient The formula used to compensate for sensitivity attenuation caused by inter-axis coupling is as follows: ,in, This represents the sum of squares of the coupling coefficients of all other axes to the i-axis, reflecting the proportion of coupling energy loss. The zero-point offset... The formula for calculating the voltage used to cancel non-quadrature crosstalk is: ,in, The real-time output voltage is the reference axis. The adjustment range of the gain correction coefficient is typically between 0.95 and 1.05, and the adjustment range of the zero-point offset is between ±10mV. In this embodiment, the control processing unit writes the above parameters into the register of the signal acquisition circuit to correct the output signal in real time.

[0134] The adjustment parameters are fed back to the mechanical adjustment structure of the coil or the signal acquisition circuit to perform a correction operation and obtain the coupling correction result.

[0135] Specifically, when the orthogonality error exceeds a preset mechanical correction threshold, a hardware mechanical correction operation is performed: First, the control processing unit generates a mechanical drive command. This mechanical drive command includes a mechanical displacement compensation amount ΔL calculated according to the aforementioned steps. Specifically, the command is a pulse width modulation (PWM) signal or a step pulse sequence, the number of pulses or duty cycle of which is linearly mapped to the mechanical displacement compensation amount ΔL. Second, the mechanical drive command is transmitted to the driver of the mechanical adjustment structure. The mechanical adjustment structure is located between the coil frame and the mounting chamber, specifically including a micro stepper motor or piezoelectric ceramic actuator, and a precision transmission mechanism (such as a fine-tuning screw or lever assembly) connected to it. After receiving the command, the driver drives the actuator to output a corresponding linear displacement or rotation angle. Finally, physical pose adjustment is performed. The actuator pushes or pulls the coil frame, causing it to undergo a small spatial displacement or rotation relative to the mounting base. The process monitors the feedback signal of the displacement sensor (if equipped) in real time until the actual position change of the coil frame reaches the mechanical displacement compensation amount ΔL, thereby restoring the orthogonality of each axis of the coil at the physical level, completing the mechanical correction, and obtaining the coupling correction result at the mechanical level.

[0136] Specifically, when the orthogonality error does not exceed a preset mechanical correction threshold, a software electrical correction operation is performed: First, the control processing unit generates an electrical parameter configuration instruction. This configuration instruction includes the gain correction coefficient and zero-point offset calculated in the preceding steps. The configuration instruction is then transmitted to the signal acquisition circuit via a data bus (such as SPI or I2C). The signal acquisition circuit includes a programmable gain amplifier (PGA) and an analog-to-digital converter (ADC). For gain correction, the control processing unit writes the gain correction coefficient into the gain register of the PGA, adjusting the amplifier's amplification factor to compensate for sensitivity attenuation caused by coupling. For zero-point correction, the control processing unit writes the zero-point offset into the calibration register of the ADC or the output control register of the digital-to-analog converter (DAC), superimposing a reverse bias voltage in the signal acquisition link to counteract the zero-point offset voltage caused by inter-axis crosstalk. Through these parameter updates, the signal acquisition circuit corrects the output signal of the three-component coil in real time, eliminating the influence of non-orthogonality errors at the electrical level and obtaining the coupling correction result at the electrical level.

[0137] Specifically, such as Figure 4 and Figure 5 As shown, the present invention also provides an area-compensated three-component electromagnetic coil coupling optimization device, comprising:

[0138] The three-component electromagnetic induction coil assembly is disposed inside the mounting chamber and includes a coil frame 1 and an induction coil 2 wound on the coil frame 1.

[0139] Specifically, the coil frame is made of non-metallic, non-magnetic material and has an overall structure of three mutually orthogonal circular frames. The induction coil is wound with multi-core copper wire on the coil frame and is divided into three components: X, Y, and Z, with the Z component being a horizontally placed coil. Each component's induction coil adopts a symmetrical differential structure, including a positive induction coil and a negative induction coil. Both the positive and negative induction coils consist of two or an even number of sub-induction coil pairs. When the sub-induction coil pairs contained in the positive and negative induction coils are placed in a crisscross pattern, every two sub-coils form a crisscross sub-induction coil pair.

[0140] The vibration suppression mechanism includes a bottom support spring 3, a top limiting spring 4, an elastic buffer layer 5, and a coil horizontal bracket 6; the coil horizontal bracket 6 is disposed between the bottom support spring 3 and the top limiting spring 4; the coil frame 1 is fixedly connected to the coil horizontal bracket 6; the bottom support spring 3 is connected between the bottom surface of the mounting chamber and the coil horizontal bracket 6; the top limiting spring 4 is connected between the top surface of the mounting chamber and the coil horizontal bracket 6; the elastic buffer layer 5 is disposed in the gap between the coil horizontal bracket 6 and the mounting chamber;

[0141] Specifically, the bottom support spring and the top limiting spring form 7 vertical non-magnetic spring pairs, totaling 8 sets, evenly distributed along the circumference of the horizontal coil (Z component) in the three-component electromagnetic induction coil. A horizontal coil bracket is provided between each set of vertical non-magnetic spring pairs. One side of the horizontal coil bracket is fixedly connected to the horizontal coil in the three-component electromagnetic induction coil via a non-magnetic screw, while the other side is placed between the vertical non-magnetic spring pairs and contacts the bottom support spring and the top limiting spring via its own limiting slot. The bottom support spring is a high-elasticity spring, with its compression amplitude set not exceeding 1 / 3 of its maximum compression amplitude, used to support the three-component electromagnetic induction coil; the top limiting spring is a lower-elasticity spring, with its compression amplitude set not exceeding 1 / 4 of its maximum compression amplitude, used to limit the upward displacement of the coil under dynamic conditions. The elastic buffer layer specifically includes a high-elasticity sponge material and an elastic silicone pad. The highly elastic sponge material is filled between the coil horizontal bracket and the spring limiting mounting chamber to limit isolation and prevent impact noise; the elastic silicone pad is attached to the inner wall groove of the mounting chamber to achieve stable limiting of the shock-absorbing support and provide primary shock absorption, absorbing minor flutter.

[0142] The characteristic testing mechanism has a built-in correction excitation coil 8, which is coaxially wound on the inner side of the coil frame 1 and is used to inject a sweep frequency excitation current signal.

[0143] Specifically, the corrective excitation coil employs a triaxial orthogonal corrective excitation coil group, coaxially wound or fixed to the inner center of the coil frame, and is electrically completely independent of the induction coil. The corrective excitation coil is configured to generate a swept-frequency excitation signal with a known frequency and current amplitude when energized, used to measure the complex transfer function and sensitivity of the three-component electromagnetic coil.

[0144] The coupling correction mechanism includes a control processing unit and a mechanical adjustment structure; the signal output terminal of the control processing unit is electrically connected to the correction excitation coil 8, and the signal input terminal of the control processing unit is electrically connected to the induction coil 2; the mechanical adjustment structure is disposed between the coil frame 1 and the mounting chamber, and is connected to the control terminal of the control processing unit.

[0145] Specifically, the signal output terminal of the control processing unit is electrically connected to the correction excitation coil for outputting an excitation signal; the signal input terminal of the control processing unit is electrically connected to the induction coil for acquiring response signals and calculating the coupling matrix. The mechanical adjustment structure is located between the coil frame and the mounting chamber. Specifically, it includes a precision adjustment mechanism and a threaded fine-tuning mechanism mounted on the coil support. The three-component electromagnetic coil support has a precision adjustment mechanism. The required mechanical adjustment angle is calculated based on the measured coupling matrix M. The precision adjustment mechanism is used to fine-tune the driver of the coil mounting platform, physically adjusting the spatial orientation of each component coil; the threaded fine-tuning mechanism is used to connect the independent frames constituting the cross-type sub-induction coils, adjusting the relative angle of the sub-coils according to the test results. The mechanical adjustment structure is connected to the control terminal of the control processing unit, performing physical adjustments based on the calculated orthogonality error or angle consistency deviation. The precision adjustment mechanism and the threaded fine-tuning mechanism are not located on the coil frame. Figure 4 Annotation.

[0146] Specifically, this invention constructs a multi-winding differential cross-type area compensation structure. Utilizing the geometric characteristic that the projected area of ​​the sub-induction coils changes in opposite directions during vibration deflection, the induced noise cancels out during the differential process, cutting off the path from the physical source where vibration attitude change is converted into magnetic flux change noise. Combined with the specific compression ratio constraint of the springs in the multi-stage damping structure, it ensures that the elastic support always operates within the linear stability range, effectively isolating and attenuating external mechanical vibration energy and reducing coil attitude jitter amplitude. Simultaneously, by injecting a sweep frequency signal into the built-in excitation coil to determine the complex transfer function, a precise mapping relationship between the excitation magnetic field and the induced voltage response is established. Based on the orthogonality error feedback calculated using the coupling matrix, mechanical adjustment or electrical compensation is driven, eliminating non-orthogonal crosstalk between the three component coils. This achieves sub-nT / s level low-noise, high-precision airborne electromagnetic detection.

[0147] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-component electromagnetic coil coupling optimization method with area compensation, characterized in that, include: Step S1: Obtain the jitter noise suppression requirements based on the flight environment parameters of the aerial reconnaissance. By constructing a multi-winding differential cross-type area compensation structure, the difference in the projected area of ​​the sub-induction coil pairs is used to cancel the induced noise in order to obtain the noise suppression result. Step S2: Based on the noise suppression results, construct a multi-level vibration reduction structure and set the compression ratio constraint of the spring pair to establish a graded vibration suppression mechanism to obtain the vibration suppression results. Step S3: Based on the vibration suppression results, the complex transfer function and sensitivity drift coefficient of the coil are calculated by integrating the built-in correction excitation coil and injecting a sweep frequency excitation signal to obtain the characteristic test results. Step S4: Construct a coupling matrix based on the characteristic test results and calculate the orthogonality error, generate adjustment parameters and feed them back to the hardware structure to obtain the coupling correction results.

2. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 1, characterized in that, The process of step S1 includes: A three-component electromagnetic coil assembly is constructed, wherein the induction coil of each component adopts a differential structure with symmetrical upper and lower parts. The differential structure consists of a positive induction coil and a negative induction coil, both of which contain an even number of sub-induction coil pairs. The sub-induction coils are placed in a crosswise manner, and the tilt angle between the coil plane and the horizontal plane is set to θ. During the jittering process, when the horizontal projected area of ​​one sub-coil decreases, the horizontal projected area of ​​the other sub-coil paired with it increases. The difference in the change of the projected area between the two sub-coils is used to offset the change in magnetic flux.

3. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 2, characterized in that, The optimization process, which sets the inclination angle θ between the coil plane and the horizontal plane, includes: Based on the vibration amplitude and frequency of the coil, select the optimal tilt angle that minimizes the difference in projected area; or, for dynamic environments where the vibration tilt angle is uncertain, configure two sets of cross-type sub-coil pairs that deflect by an angle θ with the orthogonal diameter of the coil as the axis.

4. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 3, characterized in that, The process of constructing a multi-level vibration reduction structure based on the noise suppression results and setting compression ratio constraints for spring pairs includes: A multi-stage damping structure comprising a pair of vertical non-magnetic springs is constructed, wherein the pair of vertical non-magnetic springs is composed of a bottom support spring, a coil horizontal bracket, and a top limiting spring connected in sequence; The vertical non-magnetic spring pairs are evenly arranged along the circumference of the horizontal coil in the three-component electromagnetic induction coil; Perform spring preload operation to control the compression amplitude of the bottom support spring to not exceed 1 / 3 of its maximum compression amplitude, and at the same time control the compression amplitude of the top limit spring to not exceed 1 / 4 of its maximum compression amplitude.

5. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 4, characterized in that, The process of establishing a graded vibration suppression mechanism to obtain vibration suppression results includes: Based on the vibration frequency distribution experienced by the coil in the airborne detection flight environment, the vibration is divided into a low-frequency large-amplitude segment and a high-frequency small-amplitude segment. By selecting the stiffness and pre-compression of the bottom support spring, its natural frequency is made lower than the center frequency of the low-frequency band, so as to attenuate the large-amplitude low-frequency vibrations in the first stage. By selecting the stiffness and pre-compression of the top limiting spring, it forms a displacement constraint on the high-frequency micro-amplitude vibration of the coil, thus achieving secondary vibration reduction. An elastic buffer layer is installed on the inner wall of the installation chamber to absorb residual high-frequency vibration energy using its damping characteristics. The vibration suppression result is obtained by combining the first-level attenuation, the second-level vibration reduction, and the residual high-frequency vibration energy.

6. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 5, characterized in that, The process of step S3 includes: An integrated correction excitation coil is incorporated inside the frame of the three-component electromagnetic induction coil. Inject a sweep frequency excitation current signal into the correction excitation coil; The output voltage signal of the induction coil is acquired, and the complex transfer function of the output voltage signal and the sweep frequency excitation current signal is calculated. The sensitivity drift coefficient is calculated based on the amplitude-frequency characteristic change of the complex transfer function, and the characteristic test result is obtained by combining the complex transfer function and the sensitivity drift coefficient.

7. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 6, characterized in that, The process of calculating the sensitivity drift coefficient based on the amplitude-frequency characteristic change of the complex transfer function, and combining the complex transfer function and the sensitivity drift coefficient to obtain the characteristic test result includes: The amplitude response value of the complex transfer function at the target frequency point is extracted as the measured sensitivity. Obtain the pre-stored reference sensitivity, calculate the relative deviation of the measured sensitivity relative to the reference sensitivity, and obtain the sensitivity drift coefficient; The sensitivity drift coefficient is compared with a preset drift threshold to obtain a comparison result; The characteristic test results are generated by combining the amplitude-frequency curve data of the complex transfer function with the comparison results.

8. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 7, characterized in that, The process of step S4 includes: Based on the complex transfer function data in the characteristic test results, calculate the mutual inductance coupling coefficient between any two axes of the three-component coil to construct a three-dimensional coupling matrix. The orthogonality error is obtained by solving for the deviation of the off-diagonal elements of the three-dimensional coupling matrix relative to zero. The required mechanical displacement compensation or electrical signal correction coefficient is calculated based on the orthogonality error and used as the adjustment parameter. The adjustment parameters are fed back to the mechanical adjustment structure of the coil or the signal acquisition circuit to perform a correction operation and obtain the coupling correction result.

9. The area-compensated three-component electromagnetic coil coupling optimization method according to claim 8, characterized in that, The process of calculating the required mechanical displacement compensation or electrical signal correction coefficient based on the orthogonality error as the adjustment parameter includes: The orthogonality error is compared with a preset mechanical correction threshold; When the orthogonality error exceeds the mechanical correction threshold, the required mechanical displacement compensation for the coil frame is calculated using the orthogonal projection algorithm as an adjustment parameter. When the orthogonality error does not exceed the mechanical correction threshold, the gain correction coefficient and zero offset of the signal acquisition channel are calculated as adjustment parameters according to the error compensation formula.

10. An area-compensated three-component electromagnetic coil coupling optimization device based on the area-compensated three-component electromagnetic coil coupling optimization method according to any one of claims 1-9, characterized in that, include: The three-component electromagnetic induction coil assembly is disposed inside the mounting chamber and includes a coil frame and an induction coil wound on the coil frame. The vibration suppression mechanism includes a bottom support spring, a top limiting spring, an elastic buffer layer, and a coil horizontal bracket; the coil horizontal bracket is disposed between the bottom support spring and the top limiting spring; the coil frame is fixedly connected to the coil horizontal bracket; the bottom support spring is connected between the bottom surface of the mounting chamber and the coil horizontal bracket; the top limiting spring is connected between the top surface of the mounting chamber and the coil horizontal bracket; the elastic buffer layer is disposed in the gap between the coil horizontal bracket and the mounting chamber. The characteristic testing mechanism includes a built-in correction excitation coil, which is coaxially wound on the inner side of the coil frame and used to inject a sweep frequency excitation current signal. The coupling correction mechanism includes a control processing unit and a mechanical adjustment structure; the signal output terminal of the control processing unit is electrically connected to the correction excitation coil, and the signal input terminal of the control processing unit is electrically connected to the induction coil; the mechanical adjustment structure is disposed between the coil frame and the mounting chamber, and is connected to the control terminal of the control processing unit.

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