Computational method of spatial magnetic field of large-scale complex metal structures based on time-frequency domain conversion

Abstract

The present invention discloses a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion, which relates to the technical field of spatial magnetic field analysis, including: simplifying the CAD model of a ferromagnetic thin-walled cylindrical structure with a complex structure, ignoring the thickness of the component, and establishing an idealized model without thickness; establishing a thin-shell finite element frequency domain analysis model based on this model to characterize the influence of induced eddy currents of the thin-walled structure on the spatial magnetic field; introducing an excitation magnetic field signal, performing spectrum analysis, determining a typical excitation frequency band, sampling and analyzing the model, and obtaining the spatial and temporal distribution data of the magnetic field under discrete frequencies; performing Fourier decomposition on the excitation signal to obtain spectrum data; constructing a database, performing an inner product between the excitation spectrum and the frequency domain response to obtain frequency domain response data; performing inverse Fourier transform on the frequency domain response data to obtain time domain response data; analyzing the magnetic field according to the time domain response data at multiple locations, and obtaining the time domain response results of the magnetic field under different waveform excitations in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of spatial magnetic field analysis, and in particular to a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion. Background Art

[0002] The analysis and calculation of the spatial magnetic field of large-scale, complex metal structures is of great significance in numerous fields, including electromagnetic compatibility and electromagnetic protection, and forms the basis for the optimal design of complex electromagnetic systems. During this process, the electromagnetic physical parameters, geometric configuration, transverse and longitudinal structure, overall scale, and electromagnetic excitation source characteristics of the metal structure all significantly influence the system's spatial magnetic field, leading to complex spatiotemporal propagation characteristics of the magnetic field. Therefore, accurate analysis and calculation require the synergistic influence of high-dimensional system parameters, which requires high-throughput iterative calculations of numerical models, placing high demands on the efficiency of the solution.

[0003] Currently, the solution calculation of the spatial magnetic field of metal structures generally uses a time-domain calculation method based on the finite element model. In large-scale complex geometric configuration scenarios, it faces multi-dimensional challenges such as the difficulty of automatic mesh generation, poor mesh generation quality, and extremely high degrees of freedom in the solution, resulting in extremely high solution costs and extremely low solution efficiency. The popularity of supercomputers has alleviated this research challenge to a certain extent, but there is still a long way to go to meet the demand for high-throughput solutions in high-dimensional parameter spaces. In particular, for the solution of spatial magnetic fields under variable waveform excitation over extremely long periods of time, the solution cost of the time-domain method is directly proportional to the duration of the excitation waveform, resulting in an extremely high solution scale. In summary, for the analysis and calculation of the spatial magnetic field of large-scale complex metal structures, especially high-throughput iterative calculations, there is an urgent need to develop more efficient and low-cost numerical calculation methods. Summary of the Invention

[0004] The purpose of the present invention is to realize real-time calculation of time domain problems through time-frequency domain transformation method and provide a technical means for efficiently solving the magnetic field of complex metal structures.

[0005] The technical solution of the present invention is to provide a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion, the method comprising:

[0006] S1. Simplify the CAD model of a ferromagnetic thin-walled cylindrical structure with a complex crisscross structure, ignore the thickness of the ferromagnetic thin-walled component, and establish an idealized ferromagnetic thin-walled component model without thickness at the average midline position of the shell;

[0007] S2. Based on the idealized ferromagnetic thin-walled component model established in step S1, a thin-shell finite element frequency domain analysis model is established, and an equation is established to characterize the influence of the thin-walled structure induced eddy current of the thin-shell finite element on the spatial magnetic field;

[0008] S3. Introduce an excitation magnetic field signal and perform spectrum analysis on the excitation magnetic field waveform to determine a typical excitation frequency band. Perform sampling analysis on the thin shell finite element frequency domain analysis model of step S2 within the typical excitation frequency band. Take the same number of proportional sampling points within each order of magnitude. Calculate the time domain of the sampling point data and then convert it to the frequency domain to obtain the spatiotemporal distribution data of the magnetic field at several discrete frequencies, and record the magnetic field in key areas.

[0009] S4. applying an excitation signal to the ferromagnetic thin-walled cylindrical structure, performing Fourier decomposition on the waveform of the applied excitation signal, and obtaining spectrum data thereof;

[0010] S5. Sampling the vibration waveform of the shell unit within a typical excitation frequency band, constructing a database, performing an inner product between the spectrum of the excitation waveform and the frequency domain response in the magnetic field frequency domain response database, and obtaining frequency domain response data of the spatial magnetic field of the structure under the excitation signal;

[0011] S6. Analyze the spatial magnetic field of the metal structure based on the multiple time domain response data, and perform inverse Fourier transform on the frequency domain response data obtained in step S5 to obtain time domain response data;

[0012] S7. Analyze the spatial magnetic field of the metal structure based on the time domain response data at multiple locations, and repeat steps S4-S6 to obtain the time domain response results of the magnetic field under different waveform excitations in real time.

[0013] In any of the above technical solutions, further, the typical excitation frequency band determined in step S3 is in the range of 10^-4 Hz to 10^2 Hz.

[0014] In any of the above technical solutions, further, in step S2, the equation group for characterizing the influence of the thin-walled structure-induced eddy current of the thin-shell finite element on the spatial magnetic field includes:

[0015]

[0016] In the above equations, subscript 1 represents the outer surface, subscript 2 represents the inner surface, and J s1 With J s2 represents the surface current density, E t1 and E t2 represents the surface tangential electric field intensity, ω, μ, and σ are frequency, conductivity, and magnetic permeability, respectively. d is the wall thickness of the structure, j is the imaginary unit, Z is the defined impedance, and Z S represents the surface impedance, Z T represents the transmission impedance.

[0017] In any of the above technical solutions, further, the calculation formula for Fourier decomposition in step S4 is as follows:

[0018]

[0019] Among them, x(n) is the discrete excitation signal obtained by sampling at equal time intervals, N is the number of points of the time domain discrete signal, n is the number of the time domain discrete signal (the value range is 0N-1), X(m) is the corresponding discretized spectrum data, m is the number of the frequency domain signal (the value range is 0N-1), and the number of points of the frequency domain signal is also N.

[0020] In any of the above technical solutions, further, the calculation formula for the inverse Fourier transform in step S6 is as follows:

[0021]

[0022] Where b(n) is the obtained time-domain discrete magnetic field response result, B(m)* is the conjugate complex number of B(m), and B(m) is the frequency-domain response result of the magnetic field in a typical region.

[0023] The beneficial effects of the present invention are:

[0024] The present invention provides an efficient and low-cost calculation method that can accurately analyze the spatial magnetic field distribution of large-scale complex metal structures under different excitation conditions; through time-frequency domain conversion and frequency domain analysis, it significantly reduces the computational complexity and improves the computational efficiency, and is particularly suitable for high-throughput iterative calculation requirements; in addition, this method overcomes the grid division difficulties and high-degree-of-freedom solution challenges of traditional time-domain calculations in large-scale complex geometric configuration scenarios, and has broad application prospects and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The advantages of the above and additional aspects of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0026] Figure 1 1 is a schematic diagram of the frequency domain response results of the magnetic field in three typical areas near a typical ferromagnetic shell model according to a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to an embodiment of the present invention;

[0027] Figure 2 Spectra corresponding to three typical excitation waveforms according to a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to an embodiment of the present invention;

[0028] Figure 3 2. This is a schematic diagram of the time-domain magnetic field frequency-domain response results under rectangular pulse excitation according to a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to an embodiment of the present invention;

[0029] Figure 42. This is a schematic diagram of the time-domain magnetic field frequency-domain response results under triangular pulse excitation according to a method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the time domain magnetic field frequency domain response results under single pulse excitation of a large-scale complex metal structure spatial magnetic field calculation method based on time-frequency domain conversion according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0033] This embodiment provides a method for calculating the spatial magnetic field of large-scale complex metal structures based on time-frequency domain conversion. This method performs computational analysis on a CAD model of a ferromagnetic thin-walled cylindrical structure with a complex, crisscrossing structure. The structure is excited by a magnetic field using a Helmholtz coil structure, and the cylinder is placed at the center of the Helmholtz coil to approximately simulate a uniform spatial magnetic field. The method includes:

[0034] S1. Simplify the CAD model of a ferromagnetic thin-walled cylindrical structure with a complex crisscross structure, ignore the thickness of the ferromagnetic thin-walled component, and establish an idealized ferromagnetic thin-walled component model without thickness at the location of the thickness midline of the magnetic thin-walled component.

[0035] like Figure 1 As shown in Figure (a), this embodiment uses a symmetrical cylindrical ferromagnetic thin-walled component as an example. Considering the symmetry of this component, only a quarter of the cross section is shown in the figure. Simplifying the solid model into a shell model significantly reduces the difficulty and workload of meshing and reduces the scale of equation solving.

[0036] S2. Based on the idealized ferromagnetic thin-walled component model established in step S1, a thin-shell finite element frequency domain analysis model is established, and the following equation is established to characterize the influence of the thin-walled structure induced eddy current of the thin-shell finite element on the spatial magnetic field:

[0037]

[0038]

[0039] In the above equations, subscript 1 represents the outer surface, subscript 2 represents the inner surface, and J s1 With J s2 represents the surface current density, E t1 and E t2 represents the surface tangential electric field intensity, ω, μ, and σ are frequency, conductivity, and magnetic permeability, respectively. d is the wall thickness of the structure, j is the imaginary unit, Z is the defined impedance, and Z S represents the surface impedance, Z T represents the transmission impedance.

[0040] S3. Introduce the excitation magnetic field signal and perform spectrum analysis on the excitation magnetic field waveform to obtain a typical excitation frequency band. Perform sampling analysis on the thin shell finite element frequency domain analysis model of step S2 within the typical excitation frequency band (e.g., take 3 proportional sampling points in each order of magnitude, the spectrum spans 6 orders of magnitude, and a total of 18 sampling points). Calculate the time domain of the sampling point data and then convert it to the frequency domain to obtain the spatiotemporal distribution data of the magnetic field at several discrete frequencies, and record the magnetic field in key areas.

[0041] The typical excitation frequency range defined in this embodiment is from 10^-4Hz to 10^2Hz. Figure 1 (b)(c)(d) give the frequency domain response results of the magnetic field in three typical areas near a typical ferromagnetic shell model, denoted as B(m).

[0042] S4. Apply an excitation signal to the ferromagnetic thin-walled cylindrical structure, perform Fourier decomposition on the waveform of the applied excitation signal, and obtain its spectrum data. The calculation formula is as follows:

[0043]

[0044] Among them, x(n) is the discrete excitation signal obtained by sampling at equal time intervals, N is the number of points of the time domain discrete signal, n is the number of the time domain discrete signal (the value range is 0N-1), X(m) is the corresponding discretized spectrum data, m is the number of the frequency domain signal (the value range is 0N-1), and the number of points of the frequency domain signal is also N.

[0045] like Figure 2 As shown in FIG, the spectra corresponding to three typical excitation waveforms (ie, rectangular pulse, triangular pulse, and quasi-static pulse) are given.

[0046] S5. Sample the vibration waveform of the shell unit within the typical excitation frequency band and build a database; perform an inner product between the spectrum of the excitation waveform and the frequency domain response in the magnetic field frequency domain response database to obtain the frequency domain response data of the spatial magnetic field of the structure under the excitation signal.

[0047] S6. Analyze the spatial magnetic field of the metal structure based on the multiple time domain response data, perform inverse Fourier transform on the frequency domain response data obtained in step S5, and obtain time domain response data. The calculation formula is as follows:

[0048]

[0049] Wherein, b(n) is the obtained time-domain discrete magnetic field response result, and B(m)* is the conjugate complex number of B(m).

[0050] S7. Analyze the spatial magnetic field of the metal structure based on the time domain response data at multiple locations, and repeat steps S4-S6 to obtain the time domain response results of the magnetic field under different waveform excitations in real time.

[0051] like Figure 3-5 The time domain and frequency domain response results of the magnetic field provided by the present invention under three typical excitations, namely rectangular pulse, triangular pulse and single pulse, are given in turn. The calculation results of the direct solution algorithm based on the time domain commonly used in the prior art are also given. It can be clearly seen that both show good consistency in all calculation examples, which reflects the effectiveness of the algorithm proposed in the present invention.

[0052] In summary, the present invention provides a method for calculating the spatial magnetic field of large-scale complex metal structures based on time-frequency domain conversion, which includes:

[0053] S1. Simplify the CAD model of the ferromagnetic thin-walled cylindrical structure with a complex crisscross structure, ignore the thickness of the ferromagnetic thin-walled component, and establish an idealized ferromagnetic thin-walled component model without thickness.

[0054] S2. Based on the idealized ferromagnetic thin-walled component model established in step S1, a thin-shell finite element frequency domain analysis model is established, and an equation is established to characterize the influence of the thin-walled structure induced eddy current of the thin-shell finite element on the spatial magnetic field.

[0055] S3. Introduce the excitation magnetic field signal and perform spectrum analysis on the excitation magnetic field waveform to determine the typical excitation frequency band. Sampling analysis is performed on the thin shell finite element frequency domain analysis model of step S2 within the typical excitation frequency band. The same number of proportional sampling points are taken within each order of magnitude. The time domain is calculated and then converted to the frequency domain to obtain the spatiotemporal distribution data of the magnetic field at several discrete frequencies, and the magnetic field in key areas is recorded.

[0056] S4. Apply an excitation signal to the ferromagnetic thin-walled cylindrical structure, perform Fourier decomposition on the waveform of the applied excitation signal, and obtain its spectrum data.

[0057] S5. Sample the shell unit within the typical excitation frequency band, build a database, perform an inner product between the spectrum of the excitation waveform and the frequency domain response in the magnetic field frequency domain response database, and obtain the frequency domain response data of the spatial magnetic field of the structure under the excitation signal.

[0058] S6. Analyze the spatial magnetic field of the metal structure according to the multiple time domain response data, and perform inverse Fourier transform on the frequency domain response data obtained in step S5 to obtain time domain response data.

[0059] S7. Analyze the spatial magnetic field of the metal structure based on the time domain response data at multiple locations, and repeat steps S4-S6 to obtain the time domain response results of the magnetic field under different waveform excitations in real time.

[0060] The steps in the present invention can be adjusted in sequence, combined, or deleted according to actual needs.

[0061] The units in the device of the present invention can be combined, divided and deleted according to actual needs.

[0062] Although the present invention has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely illustrative and are not intended to limit the application of the present invention. The scope of the present invention is defined by the appended claims and includes various modifications, variations, and equivalents made to the invention without departing from the scope and spirit of the present invention.

Claims

1. A method for calculating the spatial magnetic field of large-scale complex metal structures based on time-frequency domain conversion, characterized by: The method comprises: S1. Simplify the CAD model of a ferromagnetic thin-walled cylindrical structure with a complex crisscross structure, ignore the thickness of the ferromagnetic thin-walled component, and establish an idealized ferromagnetic thin-walled component model without thickness at the average midline position of the shell; S2. Based on the idealized ferromagnetic thin-walled component model established in step S1, a thin-shell finite element frequency domain analysis model is established, and an equation is established to characterize the influence of the thin-walled structure induced eddy current of the thin-shell finite element on the spatial magnetic field; S3. Introduce an excitation magnetic field signal and perform spectrum analysis on the excitation magnetic field waveform to determine a typical excitation frequency band. Perform sampling analysis on the thin shell finite element frequency domain analysis model of step S2 within the typical excitation frequency band. Take the same number of proportional sampling points within each order of magnitude. Calculate the time domain of the sampling point data and then convert it to the frequency domain to obtain the spatiotemporal distribution data of the magnetic field at several discrete frequencies, and record the magnetic field in key areas. S4. applying an excitation signal to the ferromagnetic thin-walled cylindrical structure, performing Fourier decomposition on the waveform of the applied excitation signal, and obtaining spectrum data thereof; S5. Sampling the vibration waveform of the shell unit within a typical excitation frequency band, building a database, performing an inner product between the spectrum of the excitation waveform and the frequency domain response in the magnetic field frequency domain response database, and obtaining frequency domain response data of the spatial magnetic field of the structure under the excitation signal; S6. Analyze the spatial magnetic field of the metal structure based on the multiple time domain response data, and perform inverse Fourier transform on the frequency domain response data obtained in step S5 to obtain time domain response data; S7. Analyze the spatial magnetic field of the metal structure based on the time domain response data at multiple locations, and repeat steps S4-S6 to obtain the time domain response results of the magnetic field under different waveform excitations in real time.

2. The method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to claim 1 is characterized in that: The typical excitation frequency band determined in step S3 is in the range of 10^-4 Hz to 10^2 Hz.

3. The method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to claim 1 is characterized in that: The equation group for characterizing the influence of the thin-walled structure induced eddy current of the thin-shell finite element on the spatial magnetic field in step S2 includes: In the above equations, subscript 1 represents the outer surface, subscript 2 represents the inner surface, and J s1 With J s2 represents the surface current density, E t1 and E t2 represents the surface tangential electric field intensity, ω, μ, and σ are frequency, conductivity, and magnetic permeability, respectively. d is the wall thickness of the structure, j is the imaginary unit, Z is the defined impedance, and Z S represents the surface impedance, Z T represents the transmission impedance.

4. The method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to claim 1 is characterized in that: The calculation formula for Fourier decomposition in step S4 is as follows: Among them, x(n) is the discrete excitation signal obtained by sampling at equal time intervals, N is the number of points of the time domain discrete signal, n is the number of the time domain discrete signal, and the value range of n is 0-N-1. X(m) is the corresponding discretized spectrum data, m is the number of the frequency domain signal, and the value range of m is 0-N-1. The number of points of the frequency domain signal is also N.

5. The method for calculating the spatial magnetic field of a large-scale complex metal structure based on time-frequency domain conversion according to claim 4 is characterized in that: The calculation formula for the inverse Fourier transform in step S6 is as follows: Among them, b(n) is the obtained time-domain discrete magnetic field response result, and B(m) is the frequency-domain response result of the magnetic field in the typical area.

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