Self-adaptive measurement and magnetic field visualization method for high-power semiconductor module space magnetic field radiation distribution

Abstract

The invention discloses a high-power semiconductor module space magnetic field radiation distribution-oriented adaptive measurement and magnetic field visualization method. Through combination of experimental measurement and a fitting technology, accurate measurement and visual display of space magnetic field radiation around the power module are realized. The method specifically comprises the following steps: by adopting a self-adaptive magnetic field intensity detection technology, analyzing a magnetic field intensity difference value at different measurement points, and dynamically comparing the magnetic field intensity difference value with a preset threshold value. When the difference value of the magnetic field intensity exceeds a threshold value, the number and density of measuring points are adaptively increased, comprehensive capture of change details of the magnetic field is ensured, and value selection of parameters such as a fitted curve and visual drawing processing are completed by further combining a Newton interpolation method or a Lagrange interpolation method. An efficient and accurate solution is provided for electromagnetic compatibility design and optimization of a high-power module, anti-magnetic interference design optimization is guided, and system stability and robustness are improved. The method has important significance in the fields of new energy automobiles, electromagnetic launching, ejection and the like.

Description

Technical Field

[0001] The present invention belongs to the field of electronic technology, and relates to an adaptive measurement and magnetic field visualization method for the spatial magnetic field radiation distribution of high-power semiconductor modules. Background Art

[0002] The application demand for power conversion devices has increased sharply in the fields of photovoltaic, wind energy, new energy vehicles, and industrial frequency conversion, etc., which are characterized by high component density and compact structure. In high-power converters, the large current and high-frequency switching of power devices cause stray magnetic field radiation, affecting circuit performance and the operation of adjacent circuits. The high rate of change of current and voltage and peak current of power devices constitute important EMI (Electromagnetic Interference) sources. Existing research focuses on the establishment of equivalent models, experimental verification, and circuit analysis methods for the magnetic field radiation of power devices, such as obtaining EMI spectra, common-mode current noise models, EMI estimation models, and reduced-order models through voltage and current changes. However, current research mainly focuses on the near-field single-point magnetic field radiation of high-power semiconductor devices, and there is limited attention to the global magnetic field radiation and rapid and accurate visualization mapping of power modules. This study aims to use integrated experimental measurement methods and mathematical fitting techniques to achieve accurate and convenient visualization characterization of the spatial magnetic field radiation of high-power semiconductor device modules.

[0003] Regarding the physical process of magnetic field radiation detection, based on the conducted EMI experimental platform of a buck circuit IGBT module (H. Huang, J. Wu, W. Xu, and T. Lu, The Influence of Driving Parameters on Conducted EMI for an IGBT Module, IEEE Transactions on Electromagnetic Compatibility, vol. 62, no. 5, pp. 2285-2293, Oct. 2020, doi: 10.1109 / TEMC.2020.2971720.), by setting different driving parameters in the external circuit, the switching voltage and current of the IGBT were obtained, and at the same time, the EMI noise under different driving parameters in the frequency band of 0.15 - 30 MHz was measured. However, the research on the magnetic field radiation in the IGBT mainly focuses on the near-field single-point magnetic field radiation of the IGBT, which is achieved by measuring the radiation noise using an electromagnetic signal receiving device placed close to the IGBT circuit. The disadvantage is that the measured magnetic field distribution is not comprehensive.

[0004] Regarding the research on the magnetic field radiation distribution of devices, based on the analysis of the influence of space magnetic field coupling on the transient process of power MOSFET (Y. Hao, M. Ma and D. Xu, Analysis of space magnetic field coupling effect on transient process of power MOSFET, in proc. 2023 26th International Conference on Electrical Machines and Systems (ICEMS), Zhuhai, China, 2023, pp. 4533-4536.), the time-domain electromagnetic field simulation was completed in combination with the double-pulse test results, and the magnetic field simulation results at specific moments were given. The disadvantage is that the simulation process is extremely time-consuming, and the simulation results only show part of the magnetic field distribution, without considering the magnetic field distribution in other parts around the device.

[0005] Regarding the research on magnetic field visualization mapping, the method of predicting magnetic field radiation based on near-field scanning data (W. Abdelli, A. Frikha, X. Mininger, L. Pichon, and H. Trabelsi, Prediction of Radiation From Shielding Enclosures Using Equivalent 3-D High-Frequency Models, IEEE Transactions on Magnetics, vol. 51, no. 3, pp. 1-4, March 2015, Art no. 7001504, doi:10.1109 / TMAG.2014.2362575.) was used to make destructive openings in the magnetic field shielding cover, and single magnetic field radiation measurements were carried out at the fixed opening positions. Three opening positions were selected for magnetic field measurement in the experiment, and the magnetic field distribution map was drawn. The disadvantage is that the experimental object was locally damaged, and the measurement positions were fixed, ignoring the possible areas with dense magnetic field changes in the device to be measured, resulting in inaccurate final measurement results. Summary of the Invention

[0006] Aiming at the defects in the prior art, the purpose of the present invention is to provide an adaptive measurement and magnetic field visualization method for the space magnetic field radiation distribution of high-power semiconductor modules; this method can comprehensively capture the details of magnetic field changes and can achieve accurate and adaptive measurement of the space magnetic field radiation around complex multi-chip semiconductor high-power modules.

[0007] The technical solution adopted by the present invention is as follows:

[0008] An adaptive measurement and magnetic field visualization method for the spatial magnetic field radiation distribution of high-power semiconductor modules, characterized in that by combining experimental measurement methods and fitting techniques, the adaptive measurement and visualization graph display of the spatial magnetic field radiation around high-power semiconductor modules are realized, including: adopting an adaptive magnetic field intensity detection technique, by analyzing the magnetic field intensity differences at different measurement points, dynamically comparing them with a preset threshold, when the magnetic field intensity difference exceeds the threshold, automatically determining the complexity of the magnetic field distribution in this area, and then adaptively increasing the number and density of measurement points, and then combining Newton interpolation method and Lagrange interpolation method to complete the extraction of parameters such as fitting curves and visualization drawing processing.

[0009] In the above technical solution, further, it specifically includes the following steps:

[0010] The first step: Build a magnetic field measurement platform for the high-power semiconductor module to be measured;

[0011] The second step: Based on the platform in the first step, use a magnetic field test sensor to perform equidistant measurements along two perpendicular directions of the plane at different height planes from the high-power semiconductor module;

[0012] The third step: Change the measurement frequency band of the magnetic field, reposition the magnetic field test sensor to different positions and repeat the measurement according to the method in the second step; Record the magnetic field intensity value of each point in each measurement.

[0013] The fourth step: Adopt an adaptive magnetic field intensity detection method, according to the magnetic field intensity results of the equidistant measurement points in the second and third steps, combined with the set threshold, adaptively increase the magnetic field measurement points;

[0014] The fifth step: Adopt Newton interpolation fitting or Lagrange interpolation fitting method to obtain the magnetic field distribution fitting curve between the measurement points;

[0015] The sixth step: Extract the characteristic parameters of the fitting curve, and draw the obtained global magnetic field radiation value to obtain the visualization drawing result.

[0016] Further, through the second and third steps, the high-power semiconductor module is measured at different heights, different frequency bands, and different directions. Combined with the adaptive magnetic field intensity detection, and different fitting strategies are adopted for different magnetic field measurement points, so as to obtain the global magnetic field radiation of the high-power semiconductor module, where the different heights are any height between 1 cm and 10 cm from the high-power semiconductor module, the different measurement directions are two perpendicular directions in the same height plane, and the different frequency bands are from 1 KHz to 50 MHz.

[0017] Further, in the fourth step, according to the adaptive magnetic field strength detection method, the magnetic field measurement points are adaptively increased according to the determination conditions, specifically including:

[0018] For two adjacent measurement points x in the same plane and along the same direction n and x n+1 , let their corresponding magnetic field magnitude values be f(x n ), f(x n+1 ), compare the magnitudes of f(x n ) and f(x n+1 ). When recording the magnetic field distribution, if their magnitudes are both lower than -125 dBm, and , then no additional measurement points need to be added between the two, that is, the threshold condition is satisfied; otherwise, the threshold condition is not satisfied, and a supplementary measurement point x b1 needs to be added in the middle of the corresponding two measurement points, and then the magnetic field strength is measured to obtain the magnetic field strength f(x b1 ) of the supplementary measurement point. Judge the magnetic field strength of the supplementary measurement point. If it does not satisfy , and , then in the middle of x n and x b1 and in the middle of x n+1 and x b1 , add two more supplementary measurement points x b2 , x b3 , and so on until the condition is satisfied.

[0019] Further, based on the magnetic field strength values of the measurement points in the fourth step, for two adjacent measurement points that satisfy the threshold condition, Newton interpolation is performed and fitted into the magnetic field strength distribution function B 1 (x):

[0020]

[0021] Further, for two adjacent measurement points that do not satisfy the threshold condition, Lagrange interpolation is used to fit into the magnetic field strength distribution function B 2 (x). First, construct the Lagrange basis function l i (x):

[0022]

[0023] Obtain the Lagrange fitting function B 2 (x):

[0024]

[0025] Furthermore, after the fifth-step fitting process for all measurement points in the same direction, the fitting curve of this measurement direction can be obtained. By performing the above fitting process for the measurement points at different heights, different frequency bands, and different directions, the global magnetic field distribution characteristics in the studied frequency band can be obtained.

[0026] Furthermore, equal-parameter values are taken for the fitting curve, and finally, the obtained global magnetic field radiation values are subjected to two-dimensional visualization plotting. Specifically, if the maximum number of supplementary measurement points added due to not meeting the threshold condition in all Lagrangian interpolations is P, then P points are taken at equal distances on each fitted curve to obtain their corresponding magnetic field radiation values. Finally, two-dimensional visualization plotting is performed through the interpolation fitting method to obtain the global magnetic field distribution map.

[0027] The beneficial effects of the present invention are as follows:

[0028] The present invention proposes an adaptive measurement and magnetic field visualization method for the spatial magnetic field radiation distribution of high-power semiconductor modules. By building a magnetic field radiation detection experimental platform and adopting an adaptive magnetic field intensity detection method, combined with selective Newton interpolation fitting and Lagrangian interpolation fitting methods, the global magnetic field radiation value distribution is obtained, and visualization plotting is completed. The present invention provides an efficient and accurate solution for the electromagnetic compatibility design and optimization of high-power semiconductor modules, which can improve the scientificity and pertinence of the anti-magnetic interference design of sensitive power modules, as well as the stability and robustness of the operation of the entire system. This is of great significance for promoting the application expansion of power electronics technology in new energy vehicles and electromagnetic emission, ejection and other fields. Description of the Drawings

[0029] Figure 1 is a flowchart of an adaptive measurement and magnetic field visualization method for the spatial magnetic field radiation distribution of high-power semiconductor modules according to the present invention.

[0030] Figure 2 is a magnetic field distribution map drawn by different methods in the 15 MHz frequency band according to the present invention: (a) The figure is the distribution map measured in direction 1 at a distance of 5 cm from the DUT and drawn by interpolating and fitting the original data, and (b) The figure is the distribution map measured in direction 1 at a distance of 5 cm from the DUT and drawn by the method proposed in the present invention.

[0031] Figure 3 is a magnetic field distribution map drawn by different methods in the 15 MHz frequency band according to the present invention: (a) The figure is the distribution map measured in direction 2 at a distance of 10 cm from the DUT and drawn by interpolating and fitting the original data, and (b) The figure is the distribution map measured in direction 2 at a distance of 10 cm from the DUT and drawn by the method proposed in the present invention.

[0032] Figure 4These are the magnetic field distribution maps drawn by different methods within the 32 MHz frequency band in the present invention: (a) The map is measured in direction 1 at a distance of 5 cm from the DUT and drawn by interpolating and fitting the original data. (b) The map is measured in direction 1 at a distance of 5 cm from the DUT and drawn by the method proposed in the present invention.

[0033] Figure 5 These are the magnetic field distribution maps drawn by different methods within the 32 MHz frequency band in the present invention: (a) The map is measured in direction 2 at a distance of 10 cm from the DUT and drawn by interpolating and fitting the original data. (b) The map is measured in direction 2 at a distance of 10 cm from the DUT and drawn by the method proposed in the present invention. Detailed implementation manners

[0034] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0035] An adaptive measurement and magnetic field visualization method for the spatial magnetic field radiation distribution of high-power semiconductor modules in the present invention combines experimental measurement and fitting techniques to achieve accurate and adaptive measurement of the spatial magnetic field radiation around complex power modules, and further converts the measurement results into intuitive visual graphs for display. In the specific implementation process, first, data of some specific measurement points are obtained through experimental means. The adaptive magnetic field intensity detection technology is adopted. By analyzing the magnetic field intensity differences at different measurement points and dynamically comparing them with a preset threshold, when the magnetic field intensity difference exceeds the threshold, the system automatically determines that the magnetic field distribution in this area is relatively complex, and then adaptively increases the number and density of measurement points to ensure comprehensive capture of the details of magnetic field changes. After obtaining rich magnetic field intensity data, the present invention further selectively combines the Newton interpolation method or the Lagrange interpolation method to complete the determination of the fitting curve parameter values and perform visual drawing processing. As Figure 1 shown, it specifically includes the following steps:

[0036] The first step: Build an experimental platform composed of a three-phase inverter circuit, a high-power module drive and protection circuit, a system parameter acquisition circuit, and an EMI probe.

[0037] The second step: According to the experimental platform built in the first step, fix the direction of the EMI probe and perform equidistant measurements in the horizontal and vertical directions on planes at different heights using an EMI test receiver.

[0038] The third step: Change the measurement frequency band of the magnetic field, then reposition the EMI probe to different positions and repeat the measurement, and record the magnetic field intensity value at each point.

[0039] Step 4: Use the adaptive magnetic field intensity detection method. According to the magnetic field intensity results of the equally spaced measurement points in Step 2 and Step 3, and in combination with the set threshold, adaptively increase the magnetic field measurement points.

[0040] Step 5: Optionally use Newton interpolation fitting or Lagrange interpolation fitting method to obtain the fitting curve of the magnetic field distribution between the measurement points.

[0041] Step 6: Perform equal-parameter value taking on the fitting curve, and perform two-dimensional plotting on the obtained global magnetic field radiation values to obtain the visualization plotting result.

[0042] According to a specific embodiment of the present invention, in this method:

[0043] The magnetic field radiation evaluation of the power module involves the amplitudes at different frequency bands, different heights, and different directions. The measurements are carried out at 5 and 10 cm away from the module respectively. The EMI probe is first used to scan the measurement area above the module at equal distances, and then the adaptive magnetic field intensity measurement method is used to appropriately increase the magnetic field detection points. Here, two different measurement directions are adopted: In Direction 1, the probe is positioned parallel to the measurement plane, while in Direction 2, the probe is positioned perpendicular to the measurement plane.

[0044] When performing EMI spatial measurement, initially, the EMI probe with fixed Direction 1 is used for measurement. Equal-distance measurements are carried out in the transverse and longitudinal directions within each measurement plane. The magnetic field measurement frequency band range is from 1 KHz to 50 MHz or even higher, and the resolution bandwidth is set to 1 KHz. The measurement is repeated by repositioning the EMI probe to different positions, and the magnetic field intensity value of each point is recorded. The adaptive magnetic field intensity detection method is used, in combination with Newton interpolation fitting and Lagrange interpolation fitting methods, to obtain the global magnetic field distribution and perform visualization plotting.

[0045] Specifically, first complete the measurement of 13 points in the horizontal direction and 9 points in the vertical direction. Take the first measurement at the bottom left as the coordinate origin (0, 0), and its magnetic field magnitude is f(x 1 ), with the unit of dBm. Take the vertical upward direction as the positive direction of the Y-axis and the horizontal rightward direction as the positive direction of the X-axis. The magnetic field magnitude value of the next measurement point along the positive direction of the X-axis is f(x 2 ), with the unit of dBm. Finally, fill the obtained magnetic field intensity values of the measurement points into the initial magnetic field radiation measurement matrix R 13x9 :

[0046]

[0047] First, for f(x 1 ) and f(x 2) Determine the size. When recording the maximum (minimum) magnetic field distribution, if the size is lower than -125 dBm, and , then directly perform Newton interpolation according to the following method and fit it into the magnetic field strength distribution function B(x) between the measurement points:

[0048]

[0049] If we let:

[0050]

[0051] Then we have:

[0052]

[0053] Among them, l 1 (x) and l 2 (x) are respectively linear polynomials about x, which are called interpolation basis functions. They satisfy at the nodes x 1 and x 2 :

[0054]

[0055] Therefore, a key conclusion can be drawn: The first-order interpolation polynomial B(x) that satisfies the interpolation conditions can be constructed through the linear combination of the two interpolation basis functions l 1 (x) and l 2 (x), that is, the magnetic field strength value between two points can be fitted by giving the positions of two different magnetic field measurement points and their magnetic field strength values.

[0056] During the specific test process, it is measured that f(x 1 ) = -121 dBm, f(x 2 ) = -124 dBm, x 1 = 0 (m), x 2 = 0.03 (m), which satisfies the above threshold conditions. Then perform Newton fitting on it. Referring to formula 2, the Newton interpolation fitting function B 1 (x) between the two points is obtained:

[0057]

[0058] If the judgment condition is not satisfied, then perform EMI measurement again in the middle of the two measurement points to obtain the magnetic field strength f(x 3 ). If it does not satisfy and , additional measurement points are added again between the corresponding two points until the conditions are met.

[0059] Specifically, the measurement results f(x 5 ) = -106 dBm, f(x 6 ) = -100 dBm do not meet the threshold conditions. An additional magnetic field strength measurement point f(x b1 ) = -103 dBm is added. At this time, x 5 = 0.12 m, x 6 = 0.15 m; at x b1 = 0.135 m, the three points at this time meet the above conditions.

[0060] Next, Lagrange interpolation fitting is used. First, the Lagrange basis function l i (x) is constructed:

[0061]

[0062] l i (x) satisfies:

[0063]

[0064] The basis functions can be obtained as follows:

[0065]

[0066]

[0067]

[0068] The Lagrange fitting function B 2 (x) is obtained:

[0069]

[0070] Substituting the parameter values, the Lagrange fitting function B 2 (x) is obtained:

[0071]

[0072] Since the fitting function satisfies that the value of B(x i ) at each point is the same as the measured value of the magnetic field magnitude f(x i ), that is:

[0073]

[0074] Satisfy:

[0075]

[0076] The nth-degree polynomial satisfies:

[0077]

[0078] The coefficient matrix of the fitting polynomial is:

[0079]

[0080] This coefficient matrix belongs to the Vandermonde determinant. Since the original measurement points and the supplementary measurement points are different points, the corresponding fitting polynomial of the above coefficient matrix exists and is unique. Thus, the multi-point measurement results can be represented by a unique magnetic field distribution fitting function. Then, P points are equally spaced on the curve fitted by Newton interpolation and the curve fitted by Lagrange interpolation, and the corresponding magnetic field intensity values are added to the magnetic field radiation value matrix to obtain the final magnetic field intensity radiation value matrix for plotting.

[0081] Specifically, in all fitting processes, at most 3 additional measurement points are inserted between two points to meet the threshold condition, so the parameter P = 3; therefore, 3 points need to be equally spaced on each fitting curve, and the obtained magnetic field intensity values are added to the magnetic field radiation intensity matrix. Through the two-dimensional interpolation plotting method, a visual map of the magnetic field distribution is obtained; for different frequencies, different heights, and different test directions, the magnetic field distribution maps obtained by using the method of the present invention and directly by interpolating and fitting the original data are as Figure 2 , 3 , 4 and Figure 5 shown; the distribution area of the EMI intensity of the power module can be visually observed. And it can be seen that the magnetic field distribution map obtained by the ordinary interpolation method is not as accurate as the distribution map obtained by the method proposed in the present invention. The former omits some regions with higher magnetic field intensity because the magnetic field distribution between the measurement points is not considered. The method of the present invention obtains a smoother and more accurate magnetic field distribution map by adaptively adding magnetic field measurement points in a timely manner.

Claims

1. An adaptive measurement and magnetic field visualization method for spatial magnetic field radiation distribution of high-power semiconductor modules, characterized in that: By combining experimental measurement methods with fitting technology, adaptive measurement and visual graphic display of magnetic field radiation in the space around high-power semiconductor modules are achieved, including: using adaptive magnetic field strength detection technology, analyzing the magnetic field strength difference at different measurement points, and dynamically comparing it with the preset threshold. When the magnetic field strength difference exceeds the threshold, the complexity of the magnetic field distribution in the area will be automatically determined, and the number and density of measurement points will be adaptively increased. Combined with Newton interpolation and Lagrange interpolation, parameter extraction such as fitting curves and visual drawing processing are completed.

2. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 1 is characterized in that: The specific steps include: Step 1: Build a magnetic field measurement platform for the high-power semiconductor module to be tested; Step 2: Based on the platform of step 1, a magnetic field test sensor is used to perform equidistant measurements along two perpendicular directions of a plane at different heights from the high-power semiconductor module; Step 3: Change the measurement frequency band of the magnetic field, reposition the magnetic field test sensor to a different position and repeat the measurement according to the method in step 2; record the magnetic field intensity value at each point in each measurement; Step 4: Adopting the adaptive magnetic field strength detection method, according to the magnetic field strength results of the equally spaced measurement points in the second and third steps, combined with the set threshold, the magnetic field measurement points are adaptively added; Step 5: Use Newton interpolation fitting or Lagrange interpolation fitting method to obtain the magnetic field distribution fitting curve between the measurement points; Step 6: Extract characteristic parameters of the fitting curve, and plot the global magnetic field radiation values ​​to obtain a visual plot result.

3. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 2, characterized in that: The second and third steps are used to measure the high-power semiconductor module at different heights, different frequency bands, and different directions. The adaptive magnetic field strength detection is combined with different fitting strategies for different magnetic field measurement points to obtain the global magnetic field radiation of the high-power semiconductor module. The different heights are any heights between 1 cm and 10 cm from the high-power semiconductor module, the different measurement directions are two directions perpendicular to each other in the same height plane, and the different frequency bands are from 1 KHz to 50 MHz.

4. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 2, characterized in that: In the fourth step, according to the adaptive magnetic field strength detection method, the magnetic field measurement points are adaptively added according to the judgment conditions, specifically including: For two adjacent measurement points x in the same plane and along the same direction n and x n+1 , assuming that the corresponding magnetic field magnitudes are f(x n )、f(x n+1 ), for f(x n ) and f(x n+1 ) size is compared and judged. When recording the magnetic field distribution, if its size is lower than -125dBm and , then no additional measurement point is needed between the two, that is, the threshold condition is met; otherwise, the threshold condition is not met, and a supplementary measurement point x needs to be added between the two corresponding measurement points b1 , and then measure the magnetic field strength to obtain the magnetic field strength f(x b1 ), judge the magnetic field strength of the supplementary measurement point, if it does not meet ,and , then at x n and x b1 The middle and x n+1 and x b1 In the middle, add two more additional measurement points x b2 、x b3 , and so on, until the conditions are met.

5. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 4, characterized in that: According to the magnetic field intensity value of the measuring point in the fourth step, Newton interpolation is performed for two adjacent measuring points that meet the threshold condition, and the magnetic field intensity distribution function B1(x) between the measuring points is fitted.

6. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 4, characterized in that: For two adjacent measurement points that do not meet the threshold condition, Lagrange interpolation is used to fit the magnetic field intensity distribution function B2(x) between the measurement points.

7. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 2, characterized in that: After the fifth step of fitting processing for all measurement points in the same direction, the fitting curve of the measurement direction is obtained. The above fitting processing is performed on measurement points at different heights, different frequency bands, and different directions to obtain the global magnetic field distribution characteristics under the studied frequency band.

8. The method for adaptive measurement and magnetic field visualization of spatial magnetic field radiation distribution of high-power semiconductor modules according to claim 2, characterized in that: The fitting curve is subjected to equal parameter selection, and finally the global magnetic field radiation value is visualized in two dimensions. Specifically, the number of additional measurement points added because the threshold condition is not met in all Lagrangian interpolations is at most P. Then P points are taken at equal distances on each fitted curve to obtain their corresponding magnetic field radiation values. Finally, a two-dimensional visualization is performed through the interpolation fitting method to obtain the global magnetic field distribution map.

Images