Method and device for designing a magnetic shielding device and magnetic shielding device

Abstract

The application provides a method and device for designing a magnetic shielding device and the magnetic shielding device, and the method comprises the following steps: determining a region of interest inside the magnetic shielding device, the region of interest being a region in which a magnetic field shielding effect is expected to be achieved, and the magnetic shielding device comprising N layers of housings arranged in a nested manner; determining a complete parameter set, the complete parameter set being used to describe the geometric structure of at least one of the N layers of housings and the relative position relationship between the region of interest and each of the at least one of the N layers of housings; and obtaining a set of result parameters describing the geometric structure based on the complete parameter set, wherein the result parameters can make the magnetic induction intensity in the region of interest meet a preset threshold. The method is more scientific and efficient, not only makes the optimized magnetic shielding performance greatly improved compared with an equidistant scheme, but also solves the problem that an analytical method cannot optimize a non-concentric structure magnetic shielding device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic shielding devices, and in particular to a method and device for designing a magnetic shielding device, a computer readable storage medium, an electronic device, software and a magnetic shielding device. BACKGROUND

[0002] In many cases, people need to measure weak magnetic field signals or carry out experiments in an environment with weak magnetic fields. In order to achieve the conditions for carrying out the above experiments, it is necessary to shield the interference of the geomagnetic field and other interference sources and create a weak magnetic field environment. At present, the recognized implementation method is to use high magnetic permeability magnetic materials to build a multi-layer shielding cavity to form a magnetic shielding device. The basic geometric structures that can be taken by the magnetic shielding device include: football shape (such as the Japanese COSMOS magnetic shielding device), cylindrical shape, cuboid shape (such as the German BMSR magnetic shielding room), etc. Generally speaking, the higher the symmetry, the better the magnetic shielding effect, but the more difficult the processing. The magnetic shielding cylinder has cylindrical symmetry and is easy to process, and can achieve good magnetic shielding effect at low cost, and can be processed into small to medium-sized magnetic shielding devices. For the magnetic shielding cylinder, the magnetic shielding performance is best when both ends of the bottom surface are closed, but in some cases, a single-end open magnetic shielding cylinder needs to be designed and manufactured. In the prior art, one end of the existing double-end closed magnetic shielding cylinder is opened to make it a single-end open magnetic shielding cylinder. Since the double-end closed magnetic shielding cylinder does not need to be specially optimized and designed, it also has good performance, such as an interlayer equidistant or approximately equidistant scheme, which is adopted by most manufacturers, so there is no optimization design for the parameters of the geometric structure of the magnetic shielding cylinder. However, if the single-end open magnetic shielding cylinder also adopts a similar geometric structure to the double-end closed magnetic shielding cylinder, the shielding performance will be poor. Similarly, for magnetic shielding devices with other basic geometric structures, only the opening structure is provided on the basis thereof, which will also significantly reduce the magnetic shielding performance of the magnetic shielding device.

[0003] In view of this, it is urgent to provide an optimization design method for a magnetic shielding device to improve the shielding performance of the magnetic shielding device. SUMMARY

[0004] In view of this, the embodiments of the present application provide a method for designing a magnetic shielding device, a computer readable storage medium, an electronic device, a software product and a magnetic shielding device, which realizes the optimization of the performance of the magnetic shielding device by constructing a complete parameter set and optimizing the parameters therein.

[0005] In a first aspect, the embodiments of the present application provide a method for designing a magnetic shielding device, comprising: determining a region of interest inside the magnetic shielding device, the region of interest being a region in which a magnetic field shielding effect is expected to be achieved, the magnetic shielding device comprising a plurality of nested magnetic shielding cylinders, each magnetic shielding cylinder having a cylindrical shape and being made of a magnetic material with high magnetic permeability, each magnetic shielding cylinder having a bottom surface and a top surface, the bottom surface of each magnetic shielding cylinder being connected to the top surface of the magnetic shielding cylinder nested therein, the region of interest being located in the nested magnetic shielding cylinders, and the region of interest being a region in which a magnetic field shielding effect is expected to be achieved. layered shell;

[0006] determining a complete parameter set for describing geometrical structure of at least one of the layered shell and relative position relationship between the region of interest and each of the at least one of the layered shell;

[0007] obtaining a set of result parameters describing the geometrical structure based on the complete parameter set, wherein the result parameters can make the magnetic induction intensity in the region of interest satisfy a preset threshold.

[0008] In some embodiments of the present application, obtaining a set of result parameters describing the geometrical structure based on the complete parameter set comprises:

[0009] inputting the complete parameter set as an independent variable and the magnetic induction intensity in the region of interest as a dependent variable into a derivative-free optimization model to obtain a set of optimal parameters, wherein the independent variable includes a non-monotonically increasing independent variable, the dependent variable is not monotonically increased when the non-monotonically increasing independent variable is increased, and a constant is set to define an upper limit of the non-monotonically increasing independent variable in the derivative-free optimization model;

[0010] verifying whether the non-monotonically increasing independent variable in the optimal parameters reaches the upper limit defined by the constant,

[0011] if yes, increasing the constant of the derivative-free optimization model and then re-performing the calculation of the derivative-free optimization model;

[0012] if no, verifying whether the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters satisfies the preset threshold; if yes, outputting the result, and the output result is the result parameters; if no, adjusting the input of the derivative-free optimization model and then re-performing the calculation of the derivative-free optimization model.

[0013] In some embodiments of the present application, inputting the complete parameter set as an independent variable and the magnetic induction intensity in the region of interest as a dependent variable into a derivative-free optimization model to obtain a set of optimal parameters comprises: obtaining the optimal parameters based on the complete parameter set through the derivative-free optimization model, and converting the optimal parameters into the magnetic induction intensity by a method of obtaining the magnetic field distribution of the magnetic shielding device from the geometrical structure, wherein the optimal parameters and the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters are obtained by using repeated calculation or iterative calculation in the process of the derivative-free optimization model operation.

[0014] In some embodiments of the present application, using repeated calculation in the process of the derivative-free optimization model operation comprises: calculating the target function values corresponding to all parameter combinations according to the rules of repeated calculation in the process of the derivative-free optimization model operation, selecting the optimal parameters corresponding to the minimum target function value and obtaining the values and the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters corresponding thereto.

[0015] In some embodiments of the present application, the iterative calculation in the process of the derivative-free optimization model operation comprises: obtaining new optimization parameters based on the values of the to-be-optimized parameters and the corresponding objective function values in the previous calculation in the process of the derivative-free optimization model operation, and continuously calculating according to the iteration termination condition until the optimal parameters and the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters are obtained.

[0016] In some embodiments of the present application, the method for obtaining the magnetic field distribution of the magnetic shielding device from the geometric structure comprises the finite element method.

[0017] In some embodiments of the present application, The basic geometric structures of the layer shells are the same and have symmetry, and the region of interest is a three-dimensional space.

[0018] In some embodiments of the present application, the center of the region of interest is On the symmetry plane of the layer shell.

[0019] In some embodiments of the present application, The layer shell has rotational symmetry, and the center of the region of interest is On the symmetry axis of the layer shell.

[0020] In some embodiments of the present application, the region of interest has axial symmetry, and the symmetry axis of the region of interest coincides with The symmetry axis of the layer shell.

[0021] In some embodiments of the present application, the complete parameter set is determined, comprising: determining the basic parameters of the magnetic shielding device according to a preset threshold of the magnetic induction intensity in the region of interest;

[0022] The complete parameter set is determined according to the basic parameters, wherein the basic parameters include parameters for characterizing the basic geometric structure of the magnetic shielding device, the number of layers of the shell included in the magnetic shielding device, The material of the layer shell, the thickness of each layer shell, and the size of the region of interest and the position of the region of interest relative to the magnetic shielding device.

[0023] In some embodiments of the present application, a set of result parameters describing the geometric structure is obtained based on the complete parameter set, comprising: determining a constraint condition; and obtaining a set of result parameters describing the geometric structure based on the constraint condition and the complete parameter set, wherein the constraint condition limits the parameter range in the complete parameter set.

[0024] In some embodiments of the present application, further comprising: selecting independent parameters with the same number of parameters as the complete parameter set based on the complete parameter set, wherein the independent parameters have the same completeness as the complete parameter set to completely describe the geometric structure; constructing a first generalized coordinate based on the independent parameters; and obtaining a difference characteristic parameter describing the geometric structure in the first generalized coordinate according to the complete parameter set.

[0025] In some embodiments of the present application, further comprising: constructing a second generalized coordinate based on the first generalized coordinate; and normalizing the first generalized coordinate using the second generalized coordinate.

[0026] In some embodiments of the present application, the basic geometric structure of the magnetic shielding device is a geometric structure with at least one opening structure, and the center of the basic geometric structure of the layer shell does not coincide with the center of the geometric structure, wherein the opening structure communicates the region of interest with the outer space of the layer shell.

[0027] In some embodiments of the present application, the basic geometric structure of the magnetic shielding device is a cylindrical structure with cylindrical symmetry and a single-end opening, the opening of at least one of the layer shells is provided with an annular structure extending along the outer edge of the shell towards the direction of the symmetry axis of the cylindrical structure, and the annular structure blocks the gap between the adjacent shells in the direction perpendicular to the symmetry axis;

[0028] The complete parameter set is used to represent the parameters of the symmetric cross section of the cylindrical structure, wherein the symmetric cross section refers to a half plane passing through the symmetry axis and bounded by the symmetry axis.

[0029] In some embodiments of the present application, the opening of each of the layer shells except the innermost layer shell is provided with an annular structure. 1layer shell is provided with an annular structure.

[0030] In some embodiments of the present application, the parameters of the complete parameter set include the radius of the bottom surface of the cylindrical structure the axial distance from the bottom surface to the center of the region of interest , the axial distance from each of the layer shells to the center of the region of interest and the width of the annular structure , wherein represents the first layer shell, wherein

[0031] When each of the layer shells is provided with an annular structure, is the axial distance from the geometric center of the annular structure, i.e. the center of mass, to the center of the region of interest;

[0032] When For the shell without the annular structure, is the axial distance from the outer edge of the corresponding shell without the annular structure to the center of the region of interest; and for the shell with the annular structure, For the shell with the annular structure, is the axial distance from the geometric center of the annular structure, i.e., the center of mass, to the center of the region of interest.

[0033] In some embodiments of the present application, the parameters in the complete parameter set are subjected to range limitations imposed by the constraints, wherein the constraints include:

[0034] An outer dimension constraint for defining the maximum outer boundary of the magnetic shielding device;

[0035] An inner dimension constraint for defining the minimum inner space of the magnetic shielding device;

[0036] A spacing constraint for defining the minimum spacing between adjacent shells;

[0037] A minimum width constraint for defining the minimum width of the annular structure;

[0038] A region of interest constraint for defining the minimum axial distance from the region of interest to the bottom surface of the innermost shell of the magnetic shielding device.

[0039] In some embodiments of the present application, the constraints further include an additional constraint for limiting the radius difference between the outer shell and the inner shell to be greater than the radius difference between the outer shell and the inner shell, i.e., .

[0040] In a second aspect, embodiments of the present application provide a computer-readable storage medium storing a computer program for executing the method for designing a magnetic shielding device according to any one of the above.

[0041] In a third aspect, embodiments of the present application provide an electronic device comprising a processor and a memory for storing processor-executable instructions, wherein the processor is configured to execute the method for designing a magnetic shielding device according to any one of the above.

[0042] In a fourth aspect, embodiments of the present application provide a software product for running the method for designing a magnetic shielding device according to any one of the above.

[0043] In a fifth aspect, embodiments of the present application provide a magnetic shielding device comprising: a plurality of shells nested together, wherein, > 1, and the magnetic shielding device is designed by the method for designing a magnetic shielding device according to any one of the above.

[0044] In some embodiments of this application, There is a length difference between at least one end of adjacent shells in the layered shell in the direction of use of the magnetic shielding device, and / or, An assembly gap exists between adjacent shells within the layered housing, perpendicular to the direction of use of the magnetic shielding device. The length difference and assembly gap are designed using the method employed to design the magnetic shielding device. The magnetic shielding device includes a channel for the sample to be tested to enter and exit, which can be closed by a cover. The direction of use of the magnetic shielding device is the straight line connecting the geometric center of the closed curve (edge ​​of the opening) formed by the sample's entry and exit channel in the outermost shell when not closed by the cover, and the center of the region of interest. The sample to be tested includes light, objects, and the human body, among other things. Of course, the length difference and assembly gap between the shells are not limited to the orientation relative to the direction of use as described in the above embodiment.

[0045] In some embodiments of this application, The shell in the layered shell has at least three layers, and the assembly gap between at least two adjacent shells is not equal and / or the length difference between at least two adjacent shells is not equal.

[0046] In some embodiments of this application, the magnetic shielding device The basic geometry of the shell layers is the same and they are all symmetrical; along Along the axial direction of the symmetry axis of the shell layer, One end of the shell layer has an opening, forming the open end of the magnetic shielding device; the other end, opposite the open end, is the closed end of the magnetic shielding device; near the open end of the magnetic shielding device... The shell layers form a length difference.

[0047] In some embodiments of this application, in At least one of the shells in the layered shell has an opening that extends towards the outer edge of the shell. A shielding structure extending along the axis of symmetry of a shell, with different layers of shielding structures perpendicular to each other. An assembly gap is formed in the direction of the axis of symmetry of the shell layer.

[0048] In some embodiments of this application, The outer edge of the innermost shell in the shell layer is stretched along the plane perpendicular to the opening to form a curved surface, and the shielding structure extends to the curved surface.

[0049] In some embodiments of this application, The shell layers excluding the innermost shell The opening of the shell layer is equipped with a shielding structure.

[0050] In some embodiments of this application, The basic geometry of the shell is a cylindrical structure with cylindrical symmetry, and the shielding structure is a ring structure.

[0051] Sixthly, embodiments of this application provide an apparatus for designing a magnetic shielding device, comprising:

[0052] The first determining module is used to determine the region of interest (ROI) inside the magnetic shielding device. The ROI is the region where the magnetic shielding effect is expected to be achieved. The magnetic shielding device includes nested components. Shell layer;

[0053] The second determining module is used to determine the complete parameter set, which is used to describe... The geometry of at least one shell in the layered shell and the relative positional relationship between the region of interest and each shell in the at least one shell;

[0054] The parameter optimization module is used to obtain a set of result parameters describing the geometric structure based on a complete parameter set. The result parameters enable the magnetic induction intensity in the region of interest to meet a preset threshold.

[0055] This application provides a method and apparatus for designing a magnetic shielding device, as well as the magnetic shielding device itself. In this method, a region of interest and a complete parameter set are set, and the performance of the magnetic shielding device is optimized by optimizing the parameters in the complete parameter set. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating a method for designing a magnetic shielding device provided in an exemplary embodiment of this application.

[0057] Figure 2 This is a flowchart illustrating a method for designing a magnetic shielding device provided in an exemplary embodiment of this application.

[0058] Figure 3 This is a three-dimensional schematic diagram of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application.

[0059] Figure 4 This is a two-dimensional cross-sectional schematic diagram of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application.

[0060] Figure 5 This is a schematic diagram of the structure of each layer of the housing of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application.

[0061] Figure 6 This is a schematic diagram of the symmetrical cross-section of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application in a three-dimensional illustration.

[0062] Figure 7 This is a schematic diagram of the structure of the symmetrical cross-section of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application in a two-dimensional cross-sectional view.

[0063] Figure 8 This is a schematic diagram of the structure of each layer of the magnetic shielding device to be optimized mentioned in an exemplary embodiment of this application in a symmetrical cross section.

[0064] Figure 9 This is a schematic diagram of the cylindrical region of interest in a symmetrical cross section in an exemplary embodiment of this application.

[0065] Figure 10 This is an exemplary embodiment of the present application describing a single-layer structure (the first layer). The complete set of parameters required for the layer and the region of interest.

[0066] Figure 11 This is a two-dimensional cross-sectional view of the equidistant magnetic shielding device scheme to be optimized mentioned in an exemplary embodiment of this application.

[0067] Figure 12 This is a three-dimensional schematic diagram of an optimized magnetic shielding device in an exemplary embodiment of this application.

[0068] Figure 13 This is a two-dimensional cross-sectional view of the optimized magnetic shielding device in an exemplary embodiment of this application. Attached image description:

[0070] 1-Shell; 2-Region of interest; 3-Open end; 4-Closed end; 5-Annular structure; 6-Symmetrical section; 7-Assembly gap; 8-Length difference. Detailed Implementation

[0071] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0072] Summary of the application

[0073] There are many factors affecting the performance of magnetic shielding devices, including the selection of materials, geometry, annealing and assembly process, demagnetization method, etc. The performance of closed magnetic shielding devices is the best, but in some cases, it is necessary to design and manufacture magnetic shielding devices with openings. For example, when measuring human magnetic signals (magnetocardiography, magnetoencephalography), the structure of the magnetic shielding device with openings ensures the comfort and safety of the subjects; for example, the experimental device served by the magnetic shielding device has a large cross-section through the cavity inside and outside; specific magnetic shielding devices can be used in condensed matter physics or material physics experiments, and the mechanical arm and vacuum flange used to transfer the sample from the outside into the cavity of the magnetic shielding device in vacuum; for example, the large cross-section light path in atomic physics experiments. In these cases, it may be necessary to design the magnetic shielding device with an opening structure. Among them, the opening is not a small hole drilled in the magnetic shielding device, but the minimum size of the opening is more than 15% of the maximum size of the whole device. For example, a cylindrical barrel with a length of 1 m and a radius of 0.4 m is provided with an elliptical hole at a certain position, and the major axis of the ellipse is 0.2 m and the minor axis is 0.1 m. Because , it is not considered as an opening. If the major axis of the ellipse is 0.2 m and the minor axis is 0.19 m, , it is considered as an opening.

[0074] For example, for a common cylindrical magnetic shielding cylinder, the magnetic shielding cylinder obtained based on the equal interval or approximately equal interval scheme between the shell layers of the double-end closed magnetic shielding cylinder can meet the use requirements without special optimization design. The design scheme currently adopted by most manufacturers is to open one end of the existing double-end closed magnetic shielding cylinder to make it a single-end open magnetic shielding device. However, compared with the magnetic shielding performance of the double-end closed magnetic shielding cylinder, the magnetic shielding performance of the magnetic shielding cylinder with an opening will be greatly attenuated due to the design of the opening. This problem also exists in the design of magnetic shielding devices with other basic geometric structures. Therefore, it is necessary to provide an optimized design scheme for a magnetic shielding device.

[0075] Exemplary method

[0076] Figure 1 A method for designing a magnetic shielding device is provided, which can be executed by a computer device. The method comprises:

[0077] 110, determining a region of interest 2 inside the magnetic shielding device, the region of interest 2 being a region in which a magnetic field shielding effect is expected to be achieved, and the magnetic shielding device comprising nested shell layers 1;

[0078] 120, determining a complete parameter set, the complete parameter set being used to describe geometrical structure of at least one shell 1 and the relative position relationship between the region of interest 2 and each shell 1 of the at least one shell 1;

[0079] 130, obtaining a set of result parameters describing the geometrical structure based on the complete parameter set, wherein the result parameters can make the magnetic induction intensity in the region of interest 2 satisfy a preset threshold value. The preset threshold value of the magnetic induction intensity has a corresponding external magnetic induction intensity. For example, assuming that the magnetic shielding device is exposed to a uniform axial magnetic induction intensity of 1000 nT, the maximum (or average) magnetic induction intensity in the region of interest 2 is not greater than 1 nT.

[0080] The method for designing a magnetic shielding device provided in the embodiment optimizes the design based on the region of interest 2 in the magnetic shielding device, which is different from optimizing the design based on a certain point. Meanwhile, the method combines the complete parameters to find a combination of a plurality of control variables that can make the magnetic induction intensity in the region of interest 2 minimum. This not only optimizes the design of the magnetic shielding device, but also can know which parameters in the complete parameter set can optimize the performance of the magnetic shielding device by comparing the complete parameter set.

[0081] Generally, an optimization problem can be converted into a problem of finding the minimum value of a multivariate function, which is called an objective function. The control variables of the objective function are called control variables, and there are multiple control variables. The combination of control variables that makes the objective function minimum is called the minimization of the function. The contribution of the objective function comes from two parts, one is the problem to be optimized itself, and the other is the penalty function.

[0082] For the minimum value problem of a multivariate function with constraints, the penalty function method is used to convert it into a minimum value problem of a multivariate function without constraints. The penalty function has the following properties: when the control variable is far away from the constraint boundary, the value of the penalty function is small; when the control variable is close to the constraint boundary, the value of the penalty function is large. Because the penalty function is part of the contribution of the objective function, the control variable can keep a distance from the constraint boundary during the process of finding the minimum value of the objective function. In some iterative optimization algorithms, it is judged whether the constraint condition is violated after each iteration. If it is, the step size is reduced and the calculation is re-computed until the constraint condition is not violated.

[0083] When the objective function is not derivable with respect to the arguments, the calculation can be performed with the aid of a derivative-free optimization algorithm, and therefore, in an embodiment, a set of result parameters describing the geometric structure is obtained based on the complete parameter set, including: inputting into the derivative-free optimization model with the complete parameter set as the arguments and the magnetic induction intensity in the region of interest 2 as the dependent variables, to obtain a set of optimal parameters, wherein the arguments include non-monotonically increasing arguments, the dependent variables do not monotonically increase as the non-monotonically increasing arguments increase, and a constant is set to define the upper bound of the non-monotonically increasing arguments in the derivative-free optimization model; specifically, the non-monotonically increasing arguments satisfy the following condition: as they grow, the magnetic shielding performance does not monotonically increase, but starts to decrease after a certain point. Therefore, a constant can be used to define the upper bound of these non-monotonically increasing arguments. At the same time, when the magnetic shielding performance is optimal, these non-monotonically increasing arguments do not reach the upper bound. The reason for adding a constant to define the upper bound of the non-monotonically increasing arguments is to clearly define the search range of the derivative-free optimization algorithm. The arguments in the present application also include monotonically increasing arguments, for which a constant cannot be arbitrarily specified as the upper bound, and the monotonically increasing arguments satisfy the following condition: as they grow, the magnetic shielding performance monotonically increases. Therefore, after optimization, one or more arguments will definitely reach the upper bound.

[0084] Verify whether the non-monotonically increasing arguments in the optimal parameters have reached the upper bound defined by the constant, if yes, increase the constant of the derivative-free optimization model and then re-perform the calculation of the derivative-free optimization model; if no, verify whether the magnetic induction intensity in the region of interest 2 of the magnetic shielding device with the optimal parameters satisfies the preset threshold; if yes, output the result, and the output result is the result parameters; if no, adjust the input of the derivative-free optimization model and then re-perform the calculation of the derivative-free optimization model.

[0085] In an embodiment, adjusting the input of the derivative-free optimization model in the input of the derivative-free optimization model includes: constraint conditions, the number of repeated calculations or the termination condition of iterative calculations, and the parameter categories and parameter optional ranges of the complete parameter set; wherein adjusting the parameter categories and parameter optional ranges of the complete parameter set can be achieved by adjusting any one or more of the thickness of the material of the magnetic shielding device, the number of layers of the shell 1, and the basic geometric structure of the magnetic shielding device, wherein the "basic geometric structure" refers to the structural category of the shell structure such as a cylinder, a cuboid, etc., and the "geometric structure" mentioned above refers to the specific structure of the shell, which is one of the basic geometric structures and is defined by specific parameters such as the height and radius of the cylinder, the length and width of the cuboid, etc.

[0086] In one embodiment, the input to the derivativeless optimization model yields a set of optimal parameters, including: calculating optimal parameters based on a complete parameter set using the derivativeless optimization model; converting the optimal parameters into magnetic induction intensity by obtaining the magnetic field distribution of the magnetic shielding device from its geometric structure; and employing repeated or iterative calculations during the derivativeless optimization model operation to obtain the optimal parameters and the magnetic induction intensity within the region of interest (ROI) of the magnetic shielding device with the optimal parameters. In one embodiment, repeated calculations during the derivativeless optimization model operation include: calculating the objective function values ​​corresponding to all parameter combinations according to the rules of repeated calculations, selecting the optimal parameter corresponding to the minimum objective function value, and obtaining its value and the corresponding magnetic induction intensity within the ROI of the magnetic shielding device with the optimal parameters. Iterative calculations during the derivativeless optimization model operation include: obtaining new optimal parameters based on the previously calculated values ​​of the parameters to be optimized and their corresponding objective function values; continuously calculating according to the iteration termination condition until the optimal parameters and the magnetic induction intensity within the ROI of the magnetic shielding device with the optimal parameters are obtained.

[0087] Specifically, the optimal parameters are the parameters obtained from the last iteration of the iterative calculation, or the parameters that minimize the objective function value that appear during repeated calculations. The derivativeless optimization model calls the method of obtaining the magnetic field distribution of the magnetic shielding device from the geometric structure. Using this method, the magnetic induction intensity in region of interest 2 of the magnetic shielding device with the optimal parameters is obtained based on the optimal parameters. Finally, the derivativeless optimization model outputs the optimal parameters and the magnetic induction intensity in region of interest 2 of the magnetic shielding device with the optimal parameters.

[0088] The specific calculations involved in repeated or iterative calculations include:

[0089] Iterative computation: Derivative-free optimization algorithms rely on the input objective function value to determine the value of the parameter to be optimized in the next calculation. Taking one implementation of the coordinate search algorithm as an example, this method will be explained in detail first: This algorithm sets... There are 1 control variable, and the optimization step size is 1. Among them, for the first Variables ,Pick and Given the coordinates of the test points, calculate the value of the objective function. Therefore, we have... The objective function value is calculated for each test point. Additionally, the objective function value is calculated at the initial value or obtained from the previous iteration. In this... If the initial value or the value at the last iteration is the minimum, the optimization step is reduced and the above steps are repeated. If the value at a certain test point is the minimum, the point is set as the new initial value and the above steps are repeated. The iteration is repeated until the minimum value is found.

[0090] The condition for the termination of iteration needs to be set in advance. In order to determine when the iteration stops, the optimization tolerance needs to be set The way of terminating the iteration with the optimization tolerance varies with the algorithm. For the above coordinate search method, after each iteration, the range of the above values is calculated. When the range is less than the optimization tolerance , the iteration is terminated.

[0091] Repetition calculation: It is applicable to the case where the selected derivative-free optimization algorithm in the derivative-free optimization model does not depend on the input target function value to determine the value of the selected parameter to be optimized in the next calculation, such as the exhaustive method. Specifically, the exhaustive method exhausts all parameter combinations with a preset precision and range, and needs to wait for all calculations to be completed before selecting the parameter value combination with the minimum target function as the output.

[0092] The above calculation methods can be realized by conventional software. For example, the fminsearch function of MATLAB can automatically perform derivative-free optimization, and the algorithm source code based on MATLAB, Python, C, etc. can also be easily realized.

[0093] In an embodiment, the method for obtaining the magnetic field distribution of the magnetic shielding device from the geometric structure includes the finite element method. Specifically, the finite element method is called by the derivative-free optimization model, the optimal parameters obtained by the derivative-free optimization model are input, the magnetic induction intensity in the region of interest 2 of the magnetic shielding device with the optimal parameters is obtained, and finally the derivative-free optimization model outputs the optimal parameters and the magnetic induction intensity in the region of interest 2 of the magnetic shielding device with the optimal parameters. The magnetic induction intensity is compared with the preset threshold, which can be performed manually or by using a software program.

[0094] In another embodiment, the method for obtaining the magnetic field distribution of the magnetic shielding device from the geometric structure is not limited to the finite element method, but can also use a combination of the boundary element method and the finite element method to solve the problem.

[0095] In an embodiment, The basic geometric structure of the layer shell 1 is the same and has symmetry, and the region of interest 2 is a three-dimensional space. Based on a large number of facts and experiences, it is known that the better the symmetry of the magnetic shielding device, the better the performance, and therefore the method in this embodiment is based on the symmetry of the geometric structure of the magnetic shielding device. Other parameters of the magnetic shielding device are optimized, and a three-dimensional space is selected as the region of interest 2 to make the method more scientific.

[0096] In an embodiment, the center of the region of interest 2 is on the symmetry axis of the layer shell 1, that is, the center of the region of interest 2 is on the symmetry axis of the magnetic shielding device. The center of the region of interest 2 is on the symmetry axis of the layer shell 1, that is, the center of the region of interest 2 is on the symmetry axis of the magnetic shielding device. As to how to determine the center of the region of interest 2, any one of the following two ways can be adopted. The first way: the geometric center of the magnetic shielding device, that is, the center of mass, is taken as the center of the region of interest 2; the other way: the midpoint of the line connecting the two points farthest apart in the axial direction of the magnetic shielding device can be selected as the center of the region of interest 2.

[0097] In order to further reduce the number of parameters in the complete parameter set and improve the calculation efficiency of the method, in an embodiment, the region of interest 2 has axial symmetry, and the symmetry axis of the region of interest 2 coincides with the symmetry axis of the magnetic shielding device. The symmetry axis of the region of interest 2 coincides with the symmetry axis of the magnetic shielding device. In another embodiment, the region of interest 2 is a cylindrical region. However, the shape of the region of interest 2 is not limited to a cylindrical shape, and any region with axial symmetry can be used, such as a spindle shape, a spherical shape, etc. If the original region of interest 2 does not satisfy the axial symmetry or the symmetry axis does not coincide with the symmetry axis of the magnetic shielding device, the original region of interest 2 should be expanded to obtain a new region of interest 2, which becomes the smallest axial symmetric structure that can wrap the original region of interest 2, and its symmetry axis coincides with the symmetry axis of the magnetic shielding device. Axial symmetry makes it possible to select only the geometric parameters on the symmetric section in the process of selecting the complete parameter set, which can completely describe the geometric structure. Therefore, the number of parameters in the complete parameter set is reduced, and the calculation efficiency of the method is improved.

[0098] The complete parameter set contains parameters that can control all possible changes in the geometry. For different geometries, the complete parameter set contains different parameters for describing the geometry thereof. For example, for a single spherical shell and a spherical region of interest within the spherical shell, the complete parameter set contains 4 parameters, i.e., the inner radius (or outer radius) of the spherical shell, and a three-direction displacement vector of the center of the region of interest relative to the center of the spherical shell. Here, the three-direction displacement vector cannot be replaced by the distance between the two centers, because when the two centers do not coincide, the shielding performance of the device is anisotropic, and the external magnetic field has directionality, so the relative position relationship of the two centers in three-dimensional space needs to be clearly defined. For example, for a single cuboid shell and a cuboid region of interest within the cuboid shell, the complete parameter set contains 6 parameters, i.e., the length, width, and height (inner or outer) of the cuboid shell, and a three-direction displacement vector of a vertex of the region of interest relative to a vertex of the cuboid shell. Therefore, in order to be able to describe all possible changes in the geometry of the shielding cylinder, the complete parameter set is determined based on the basic parameters of the magnetic shielding device in the embodiment. Specifically, in an embodiment, the complete parameter set is determined by: determining the basic parameters of the magnetic shielding device according to a preset threshold of the magnetic induction intensity of the region of interest 2; and determining the complete parameter set according to the basic parameters, wherein the basic parameters include parameters for representing the basic geometry of the magnetic shielding device, the number of layers of the shell 1 included in the magnetic shielding device, the material of the layer shell 1, the thickness of each layer shell 1, and the size of the region of interest 2 and the position of the region of interest 2 relative to the magnetic shielding device, wherein the "parameters for representing the basic geometry of the magnetic shielding device" mentioned above specifically refer to the types of parameters for representing the geometry of the magnetic shielding device. Specifically, the method for determining the basic parameters of the magnetic shielding device according to the preset threshold of the magnetic induction intensity of the region of interest 2 is as follows: the preset threshold is that in the case of a background magnetic field of 1000 nT, the average magnetic induction intensity in the region of interest is expected to be no more than 100 nT, and according to this threshold, it can be estimated that the number of layers does not need to be greater than 4.

[0099] In order to improve the calculation efficiency, in an embodiment, a set of result parameters for describing the geometry is obtained based on the complete parameter set, including: determining a constraint condition; and obtaining a set of result parameters for describing the geometry based on the constraint condition and the complete parameter set, wherein the constraint condition limits the parameter range in the complete parameter set. The constraint condition is an inequality, and when a monotonic independent variable is limited by the constraint condition, the corresponding constraint condition can be converted from an inequality to an equality, so as to reduce the number of parameters in the complete parameter set, and thus improve the calculation efficiency of the derivative-free optimization model.

[0100] To improve the computational efficiency of the derivative-free optimization model, in an embodiment, the method further comprises: selecting independent parameters with the same number of parameters as the complete parameter set based on the complete parameter set, wherein the independent parameters have the same completeness as the complete parameter set to completely describe the geometric structure; constructing a first-level generalized coordinate based on the independent parameters; and obtaining the difference characteristic parameters describing the geometric structure according to the complete parameter set in the first-level generalized coordinate. The first-level generalized coordinate selects the difference characteristics in the geometric structure of the magnetic shielding device based on the complete parameter set, because the optimization algorithm in the derivative-free optimization model will try to change the characteristics of the geometric structure of the magnetic shielding device, and the change is small relative to the reference amount, for example, the change in the radius of the bottom surface is much smaller than the radius itself, which is not conducive to the operation of most optimization algorithms. Selecting the difference characteristics in the geometric structure of the magnetic shielding device is conducive to improving the computational efficiency of the derivative-free optimization model, and further improving the computational efficiency of the entire method.

[0101] To further improve the computational efficiency of the derivative-free optimization model, in an embodiment, a second-level generalized coordinate is constructed based on the first-level generalized coordinate; and the first-level generalized coordinate is normalized using the second-level generalized coordinate. Normalization makes the to-be-optimized parameters in the complete parameter set near the high-dimensional unit sphere in the parameter space, which is conducive to improving the computational efficiency of the derivative-free optimization model.

[0102] In an embodiment, the basic geometric structure of the magnetic shielding device is a geometric structure with at least one opening, and The centers of the basic geometric structures of the layer shells 1 do not coincide, wherein the openings communicate the region of interest 2 with the outer space of the layer shell 1. In another embodiment, the magnetic shielding device is a non-concentric geometric structure with one opening. The conventional analytical method cannot calculate the shielding coefficient of the magnetic shielding device with a non-concentric structure and an opening, while the method provided in the embodiment can accurately calculate the shielding coefficient of the magnetic shielding device with a non-concentric structure and an opening by using the finite element model for numerical calculation. On the other hand, the accuracy of the method in the embodiment can be adjusted. The numerical method is not absolutely accurate, and its accuracy is affected by the numerical precision of the computer, the density of the finite element mesh, and the tolerance of the iterative solution of the linear equation system. Therefore, the calculation accuracy of the numerical method can be adjusted by adjusting the above parameters. For example, the calculation accuracy of the numerical method can be improved by appropriately increasing the density of the finite element mesh and reducing the tolerance of the iterative solution of the linear equation system.

[0103] From the perspective of increasing the adaptability of the magnetic shielding device, improving its magnetic shielding performance, appropriately reducing the processing difficulty and cost, etc., in an embodiment, the basic geometric structure of the magnetic shielding device is a cylindrical structure with cylindrical symmetry and a single-end opening, The opening of at least one of the shell layers 1 is provided with an annular structure 5 extending along the outer edge of the shell 1 towards the direction of the symmetry axis of the cylindrical structure, the annular structure 5 occluding the gap between adjacent shells 1 in the direction perpendicular to the symmetry axis; a complete set of parameters is used to characterize the parameters of the symmetric cross section 6 of the cylindrical structure, where the symmetric cross section 6 refers to the half-plane passing through the symmetry axis and bounded by the symmetry axis.

[0104] In another embodiment, The openings of the shell layers 1, except for the innermost shell layer, are provided with an annular structure 5. The openings of the shell layers 1 are provided with an annular structure 5. The annular structure 5 can improve the shielding performance without changing the size of the internal space and the size of the external dimensions. The innermost shell layer is not provided with an annular structure 5 because this would reduce the size of the opening of the magnetic shielding device, thus reducing the maximum size of the object that can enter the internal space.

[0105] Based on the above structure, for example, the parameters of a complete set of parameters describing the geometry of the magnetic shielding device include the radius of the base of the cylinder , the axial distance of the base to the center of the region of interest , the axial distance of each of the shell layers to the center of the region of interest and the width of the annular structure , wherein represents the first shell layer, wherein,

[0106] When each of the shell layers is provided with an annular structure, is the axial distance of the geometric center, i.e. the centroid, of the annular structure to the center of the region of interest;

[0107] When at least one of the shell layers is not provided with an annular structure, for the shell layer not provided with an annular structure, is the axial distance of the outer edge of the corresponding shell layer not provided with an annular structure to the center of the region of interest; for the shell layers provided with an annular structure, is the axial distance of the geometric center, i.e. the centroid, of the annular structure to the center of the region of interest.

[0108] ​In an embodiment, the parameters in the complete parameter set are subjected to range restrictions by constraint conditions, wherein the constraint conditions include: an outer dimension constraint, an inner dimension constraint, a minimum width constraint, and a region of interest constraint, wherein the outer dimension constraint is used to define the maximum outer boundary of the magnetic shielding device; the inner dimension constraint is used to define the minimum inner space of the magnetic shielding device; the spacing constraint is used to define the minimum spacing between adjacent shells; the minimum width constraint is used to define the minimum width of the annular structure 5; and the region of interest constraint is used to define the minimum axial distance from the region of interest 2 to the bottom surface of the innermost shell of the magnetic shielding device.

[0109] In another embodiment, the constraint conditions further include an additional constraint, which is used to limit the radius difference of the outer layer between adjacent shells 1 to be greater than the radius difference of the inner layer, i.e. .

[0110] The method for designing a magnetic shielding device provided in this embodiment uses a combination of a derivative-free optimization model and finite element analysis. This not only greatly improves the magnetic shielding performance of the optimized magnetic shielding device compared with the magnetic shielding device with equal spacing between the shells, but also solves the problem that the analytical method cannot optimize the non-concentric structure magnetic shielding device. At the same time, the derivative-free optimization method is used in this method, which makes the calculation more efficient and allows a large number of parameters to be tried. The complete parameter set is used to control all possible changes based on the geometric structure, and the optimization design is performed with a fixed process to reduce the subjective influence of humans and obtain more scientific data results. It should be noted that this method is not limited to this way of using a derivative-free optimization model and finite element method, and can also use a derivative-free optimization model in combination with finite element method and boundary element method, or replace the derivative-free optimization model in this application with a trained model, machine learning, etc. to optimize the design of the magnetic shielding device based on the inventive concept of this application.

[0111] In order to better demonstrate the inventive concept of this application, another exemplary embodiment is provided to further illustrate the method for designing a magnetic shielding device in this application based on the above exemplary method. In this exemplary embodiment, the number of layers of the shells 1 of the magnetic shielding device is taken as an example of 6 layers, but the actual number of layers is not limited to 6 layers.

[0112] As shown in Figure 2 , this exemplary embodiment provides a method for designing a single-end open multi-layer nested cylindrical magnetic shielding device, the basic geometric structure of which is a single-end open multi-layer nested cylindrical magnetic shielding cylinder, the radial direction along the radius of the bottom surface of the cylinder is defined as the radial direction, and the axial direction along the height of the cylinder is defined as the axial direction. The open end is referred to as the open end 3, and the closed end opposite to the open end 3 is referred to as the closed end 4.

[0113] A three-dimensional diagram of the magnetic shielding cylinder to be optimized is shown in Figure 3As shown, the radial direction is not limited to the direction shown in the figure, and any direction parallel to the radius of the bottom surface of the cylinder can be regarded as the radial direction; a two-dimensional cross-sectional view of the magnetic shielding cylinder to be optimized is shown in Figure 4 As shown; the cross section can be selected as any plane that passes through the diameter of the cylinder symmetry axis and the bottom surface at the same time. The magnetic shielding cylinder is composed of multiple layers of nested shells 1, and the structure of each layer of shell 1 is shown in Figure 5 As shown, the structure of the multiple layers of nested shells 1 is shown in FIGS. 3 and Figure 5 As shown.

[0114] The opening of each layer of shell 1 is provided with a ring structure 5 extending along the outer edge of the shell 1 towards the direction close to the symmetry axis, and the opening of the innermost layer of shell is not provided with the ring structure 5. The ring structure 5 can improve the shielding performance of the magnetic shielding cylinder without changing the size of the internal space and the external size of the magnetic shielding cylinder. The opening of the innermost layer of shell is not provided with the ring structure 5 in order to avoid reducing the aperture size of the opening of the magnetic shielding cylinder, thereby not reducing the maximum size of the object that can enter the internal space of the magnetic shielding cylinder.

[0115] The structure of the magnetic shielding cylinder in this embodiment has rotational symmetry, so only a set of parameters are needed to describe the geometry on the symmetric cross section 6, and the geometry of the entire device can be completely described.

[0116] The symmetric cross section 6 can be selected as any half-plane with the cylinder symmetry axis as one side and extending infinitely in the other three directions. As shown in Figure 6 In the three-dimensional view, the dashed box ABCD represents the symmetric cross section 6, which is a half-plane. Among them, AD is the symmetry axis of the cylinder, which is a straight line extending infinitely at both ends; BC is a straight line extending infinitely parallel to AD; AB is a ray with A as the end point, which extends infinitely in the AB direction and is parallel to a certain radius of the cylinder; DC is a ray parallel to AB, D is the end point of the ray, and the ray extends infinitely in the DC direction. The above-mentioned certain radius can be any radius, so the position of the symmetric cross section 6 is not only the one shown in the figure, but also the position after rotating around the symmetry axis AD.

[0117] As shown in Figure 7 In the two-dimensional cross-sectional view, the dashed box ABCD represents the symmetric cross section 6, which is a half-plane. Among them, AD is the symmetry axis of the cylinder, which is a straight line extending infinitely at both ends; BC is a straight line extending infinitely parallel to AD; AB is a ray with A as the end point, which extends infinitely in the AB direction and is parallel to a certain radius of the cylinder; DC is a ray parallel to AB, D is the end point of the ray, and the ray extends infinitely in the DC direction. Because the cross section of the two-dimensional cross-sectional view can be selected as any plane that passes through the diameter of the cylinder symmetry axis and the bottom surface at the same time, the symmetric cross section 6 can be at a position after rotating around the symmetry axis AD.

[0118] As Figure 8 shown, for the structure of each layer of the shell 1, in the symmetry section 6, only the solid line structure in the figure is meaningful, and the dashed line part is outside the symmetry section 6 and is not considered.

[0119] The method for providing a single-end open multi-layer nested cylindrical magnetic shielding cylinder in an embodiment can use a calculation program or a software product to execute the method. The specific operation process of the method includes:

[0120] 201: Define a region of interest 2 (ROI, region of interest); the region of interest 2 is a region inside the magnetic shielding cylinder where the magnetic field shielding effect is expected to be achieved.

[0121] The region of interest 2 is a region in a three-dimensional space, which has axial symmetry and the symmetry axis coincides with the symmetry axis of the magnetic shielding cylinder. In an embodiment, the region of interest 2 is a cylindrical region, but it is not limited to a cylindrical shape, and any region with axial symmetry can be used, such as a spindle shape, a spherical shape, etc.

[0122] As an example, a cylindrical region of interest 2 is selected. The cylindrical region can be completely described by the bottom radius and the height . Thus, the volume of the region of interest 2 is . For other shapes of the region of interest 2, the corresponding parameters should be selected to completely describe them and calculate the volume. In the symmetry section 6, the cylindrical region of interest 2 becomes a rectangle. As shown in the attached Figure 9 , the rectangle drawn with the dashed line in the figure is the region of interest 2, the width of the rectangle corresponds to the bottom radius of the cylindrical region of interest 2, and the height of the rectangle corresponds to the height of the cylindrical region of interest 2. ROI is the abbreviation of region of interest, which represents the region of interest 2.

[0123] In this example, ;

[0124] .

[0125] 202: Select the material of the magnetic shielding cylinder

[0126] Magnetic materials come in many types: soft magnetic alloys, hard magnetic alloys, soft magnetic ferrites, amorphous magnetic materials, etc. Soft magnetic materials (including alloys and ferrites) are materials whose internal magnetic induction is large when in an external magnetic field, but whose internal magnetic induction is small when the external magnetic field is removed, and they almost return to their initial state, such as permalloy. Hard magnetic materials are materials whose internal magnetic induction is large when in an external magnetic field, but whose internal magnetic induction is still large when the external magnetic field is removed, and they cannot return to a state close to their initial state without external intervention, such as permanent magnets (magnets). Alloys generally have good processability and mechanical properties, and are easy to build into large magnetic shielding devices. In contrast, ferrites are sintered from ceramics and are not easy to process, have poor mechanical properties, and can only be built into small magnetic shielding devices. Amorphous magnetic materials can generally only be made into foils and cannot be used as the main structure of magnetic shielding devices, but can only be used as auxiliary structures.

[0127] In one embodiment, the material of the magnetic shielding cylinder can be high permeability permalloy. However, its selection is not limited to permalloy. Other materials such as iron, silicon steel, ferrite, other iron-nickel alloys, etc. can also be selected. In particular, a combination of multiple materials can be selected. For example, for the innermost layer of a multi-layer permalloy shielding cylinder, ferrite can be used instead of permalloy, which can greatly reduce thermal noise at the cost of a small amount of shielding performance, because the electrical conductivity of ferrite is lower than that of permalloy.

[0128] Once the material to be used is determined, the magnetic properties of the material should be obtained. In one embodiment, the initial permeability or the initial relative permeability of the material can be obtained. Alternatively, the initial B-H curve or H-B curve (also known as the initial magnetization curve) of the material can also be obtained. These data cannot be accurately determined before the magnetic shielding cylinder is completely processed, because the final step of processing, bulk annealing, will change the magnetic properties of the material. However, the properties of the same model of material are relatively stable, and data from multiple batches of the material before processing should be obtained as the required data. In addition, the thickness of the material may also be determined. The thickness of the material in each layer can be different, and the thickness of the material depends on the specifications that the material supplier can provide, and the shielding performance and mechanical properties also need to be considered.

[0129] In this embodiment, 1J85 permalloy is selected as an example, and the initial relative permeability = 30000, .

[0130] 203: Select the number of layers of the magnetic shielding cylinder

[0131] The number of layers of the magnetic shielding cylinder should be estimated according to the size, location, desired shielding performance and material performance of the region of interest 2. The number of layers of the magnetic shielding cylinder is usually 2-8, but the present application is not limited to these numbers of layers. Only after the number of layers is selected, the following steps of the present method can be performed. In the subsequent steps, the shielding performance will be calculated, and if the performance of the optimized magnetic shielding device cannot meet the preset threshold, more layers should be selected again; if the performance of the optimized magnetic shielding device far exceeds the preset threshold, fewer layers can be selected again to reduce the cost. The innermost layer is defined as the first layer, and the layers are numbered outwardly in increasing order.

[0132] As an example, 6 layers are selected as the number of layers.

[0133] 204: Determine the complete parameter set of the magnetic shielding cylinder

[0134] Regarding how to determine the complete parameter set, in an embodiment, the determination of the parameter coordinates requires the establishment of a coordinate system. Specifically, a two-dimensional plane coordinate system is established in the symmetric cross section 6 of the magnetic shielding device. In an embodiment, a two-dimensional Cartesian coordinate system is used. The origin of the coordinate system is located at the midpoint of the structure where the symmetry axis of the region of interest 2 is located, the first coordinate axis (named axis) is along the radial direction, and the second coordinate axis (named axis) is along the axial direction. When the symmetric cross section 6 is placed in a three-dimensional graph, a third axis (named axis) can be added to form a cylindrical coordinate system in a three-dimensional space. In the two-dimensional cross-sectional view, the third axis is perpendicular to the paper and outward.

[0135] Figure 10 The complete parameter set required to describe a single layer structure (the first layer) and the region of interest 2 is shown, which has 4 parameters:

[0136] i. Bottom surface radius

[0137] ii. Axial distance between the bottom surface and the center of the region of interest 2

[0138] iii. Axial distance between the open end 3 annular structure 5 and the center of the region of interest 2

[0139] iv. Width of the open end 3 annular structure 5

[0140] Generally, for a single-end open shielding cylinder , 4 parameters are required to form a complete parameter set. When there is no annular structure 5 in the innermost layer, one is removed, and A complete parameter set consists of 23 parameters, which are and the innermost layer without the annular structure 5, a complete parameter set consists of 23 parameters, which are

[0141]

[0142] 205: Determine the constraints

[0143] The constraints include the following 6 categories:

[0144] i. Outer dimension constraints. Including the maximum length and the maximum width of the magnetic shielding cylinder, to define the maximum outer boundary of the shielding cylinder to ensure that the volume of the magnetic shielding cylinder is within a reasonable range. This needs to refer to the environment where the magnetic shielding cylinder is used, such as the passability of the corridors of a building, freight elevators, doors, etc., and the available space in the room, and is determined after excluding the external additional shell and parts. The method of the constraints acting on the parameters is:

[0145]

[0146]

[0147] In an embodiment, the first equation is taken as equal, i.e. ;

[0148] This is because generally, within the typical applicable range, the shielding performance of a single-end open magnetic shielding cylinder increases with length. Adding this equation constraint can reduce the number of parameters in the complete parameter set, thereby reducing the number of parameters to be optimized in the complete parameter set to improve overall calculation efficiency.

[0149] The typical applicable range refers to the ratio of the axial length of each layer to the radius of the base surface being between 0 and 2, which may be slightly changed with the addition of the annular structure 5. As an example, , .

[0150] ii. Inner dimension constraints. Including the minimum inner width of the magnetic shielding cylinder, to define the minimum internal space of the magnetic shielding cylinder to ensure that it has a large enough opening aperture to pass through and accommodate the shielded body. This needs to refer to the maximum size of the shielded body, and is determined after adding the internal additional shell and parts. Because the magnetic shielding cylinder is single-end open, there is no need to consider the minimum length constraint.

[0151] The method of the constraints acting on the parameters of the inner dimension constraints is:

[0152]

[0153]

[0154] In one embodiment, the first equation is set to be equal, i.e. fixed

[0155] This is because generally, in the typical applicable range, the shielding performance of a single-ended open magnetic shielding cylinder increases with the reduction of the radius. Adding this equation constraint can reduce the number of parameters in the complete parameter set, thereby reducing the number of parameters to be optimized in the complete parameter set in step 206, to improve the calculation efficiency of step 211. If the innermost layer adds the annular structure 5, the first equation cannot be set to be equal. As an example, the innermost layer does not add the annular structure 5, and the following is selected .

[0156] iii. Spacing constraint. Including minimum spacing to define the minimum spacing between adjacent shells 1 to ensure that there is enough space to arrange the interlayer degaussing cable and fill the damping support material during assembly. This needs to consider the diameter of the interlayer degaussing cable and the assembly process. The method of the constraint condition acting on the parameters is:

[0157]

[0158]

[0159]

[0160] As an example, the following is selected .

[0161] iv. Minimum width constraint. Including minimum width to define the minimum width of the annular structure 5, and the annular structure 5 smaller than this width cannot be processed. The method of the constraint condition acting on the parameters is:

[0162]

[0163] As an example, the following is selected .

[0164] v. Region of interest constraint. Including the minimum distance from the boundary of the region of interest 2 in the axial direction to the bottom surface of the innermost layer of the magnetic shielding cylinder to define the minimum axial distance of the region of interest 2 from the bottom surface of the innermost layer of the magnetic shielding cylinder. The determination of the minimum axial distance is related to degaussing. In the ideal degaussing case, because the innermost layer of the magnetic shielding cylinder has no residual magnetism and will not affect the region of interest 2; generally, in the case of better degaussing, the following is selected The influence of the remanence of the innermost layer of the magnetic shielding cylinder on the region of interest 2 can be reduced to a negligible level. In particular, if the shielded body itself generates a magnetic field, the radius difference of the outermost layer of the shell 1 needs to be increased appropriately to reduce the coupling effect with the innermost layer of the magnetic shielding cylinder and the magnetization of the innermost layer of the magnetic shielding cylinder. The method of applying constraints to the parameters is:

[0165]

[0166] where represents the maximum distance from the center of the region of interest 2 to the boundary of the bottom surface of the innermost layer of the shielding cylinder.

[0167] As an example, the following values are selected . Since the region of interest 2 is a cylinder, the following values are selected .

[0168] vi. Additional constraints (optional). The additional constraints are used to limit the radius difference of the outer shell 1 to be greater than the radius difference of the inner shell 1 to improve computational efficiency. This is because the outer shell 1 can improve the shielding performance using a larger radius difference. The method of applying constraints to the parameters is:

[0169] As an example, the following additional constraints are added.

[0170] 206: Construct the primary generalized coordinates to handle the parameters in the complete parameter set and the constraints

[0171] In the case where the innermost shell does not add the annular structure 5 and ; , there are independent parameters in the complete parameter set. Select another independent parameters with the same completeness as the original parameter set to completely describe the geometric structure, which independent parameters are called generalized coordinates. The generalized coordinates are selected to improve computational efficiency.

[0172] The primary generalized coordinates are selected based on the complete parameter set to select the difference features in the geometric structure. This is because the optimization algorithm of the derivative-free optimization model used in this method will try to change the features of the geometric structure, and the change is small relative to the reference quantity, for example, the change in the radius of the bottom surface is much smaller than the radius itself, which is not conducive to the operation of most optimization algorithms. Selecting the difference features in the geometric structure is beneficial to improving the computational efficiency of the derivative-free optimization model.

[0173] The radius difference

[0174]

[0175] is selected instead of the original .

[0176] Select the spacing between adjacent bottom surfaces

[0177]

[0178] To replace the original axial distance between the bottom surface and the center of region of interest 2 ,

[0179] The difference between the axial distance between the bottom surface of the innermost shell of the magnetic shielding cylinder and the center of region of interest 2 and the distance from the center of region of interest 2 to the edge of region of interest 2 closest to the bottom surface of the innermost shell of the magnetic shielding cylinder is selected as the minimum distance relative to the boundary of region of interest 2 to the bottom surface of the innermost shell of the magnetic shielding cylinder. The increase in value

[0180]

[0181] To replace the original .

[0182] Select the axial distance between the center of the annular structure 5 and the center of the region of interest 2. The axial distance between the outermost annular structure 5 and the center of the region of interest 2 reduction

[0183]

[0184] The axial distance between the original annular structure 5 and the center of the region of interest 2 is replaced. .(Notice ,and Already (Alternative.)

[0185] Based on the internal dimension constraints, the first The maximum allowable width of the ring structure 5 is The reduction in width of the ring structure 5 relative to its maximum width is selected.

[0186]

[0187] To replace the original ring structure with a width of 5 .

[0188] Accordingly, the constraints are transformed into a first-level generalized coordinate description:

[0189] remember

[0190]

[0191] It is used to represent the maximum value of the radius difference between the outermost and innermost layers.

[0192] Constraint i is transformed into

[0193]

[0194] Constraint ii is transformed into

[0195]

[0196] Constraint iii is transformed into

[0197]

[0198]

[0199]

[0200] Constraint iv is transformed into

[0201]

[0202] where If the innermost layer contains a cyclic structure 5, the value of .

[0203] Constraint v is transformed into

[0204]

[0205] Constraint vi is transformed into

[0206]

[0207] As an example, on the basis of the example of step 205, the following primary generalized coordinates are chosen:

[0208]

[0209]

[0210]

[0211]

[0212]

[0213]

[0214]

[0215]

[0216]

[0217]

[0218]

[0219]

[0220]

[0221]

[0222]

[0223]

[0224]

[0225]

[0226]

[0227]

[0228]

[0229] They satisfy the following constraints:

[0230]

[0231]

[0232]

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244]

[0245]

[0246]

[0247]

[0248]

[0249]

[0250]

[0251]

[0252]

[0253]

[0254]

[0255]

[0256]

[0257] 207: Determine the initial value of the parameters to be optimized, for the calculation of the subsequent model

[0258] There are two methods to determine the initial value of each parameter.

[0259] Method 1: Select the initial value so that each layer of the magnetic shielding cylinder forms an equidistant distribution. In the description of the first-order generalized coordinates, For each Take the same value, For each Take the same value, Take 0, The value of should satisfy For each The same, The value of for each The same. The above values also satisfy the constraint conditions of step 205, or the constraint conditions after step 206 transformation. If step 206 is skipped, the selection of the initial value still follows the above principles.

[0260] As an example, based on the example in step 206, the following initial values are selected: (the numbers in the superscript parentheses are used to indicate the number of iterations in step (211), and the number 0 indicates that no iteration has been performed, and the initial value. The same applies below.)

[0261]

[0262]

[0263]

[0264]

[0265]

[0266]

[0267]

[0268]

[0269]

[0270] The two-dimensional profile drawn in this equidistant scheme is shown in Figure 11.

[0271] Method two: select the initial value according to experience, and the initial value needs to be as close to the optimized design as possible, which can improve the calculation efficiency of step 211. The above values also need to meet the constraint conditions of step 205, or the constraint conditions after step 206 transformation.

[0272] As an example, based on the example in step 206, the following initial values are selected:

[0273]

[0274]

[0275]

[0276]

[0277]

[0278]

[0279]

[0280]

[0281]

[0282]

[0283]

[0284]

[0285]

[0286] 208: Constructing secondary generalized coordinates, normalizing the parameters and constraints obtained from the primary generalized coordinates

[0287] Normalization makes the parameters to be optimized in the parameter space near the high-dimensional unit sphere, which is beneficial to improve the computational efficiency of the subsequent step 211. The specific method is that for the primary generalized coordinates with initial value not equal to 0, the initial value is normalized:

[0288]

[0289]

[0290]

[0291] For the primary generalized coordinates with initial value equal to 0, a constant value is used for normalization, and the constant value is generally taken as The value is related to the assembly process and reflects the smallest detail that can be assembled.

[0292]

[0293]

[0294] The value used for normalization is not limited to the above selection. If there is design experience, the constant used for normalization can be adjusted.

[0295] Correspondingly, the constraints of step 205 or step 206 need to be converted into secondary generalized coordinate description:

[0296] Constraint i is converted into

[0297]

[0298] Constraint ii is converted into

[0299]

[0300] Constraint iii is converted into

[0301]

[0302]

[0303]

[0304] Constraint iv translates into

[0305]

[0306] where If the innermost layer contains a cyclic structure 5, the value of .

[0307] Constraint v translates into

[0308]

[0309] Constraint vi translates into

[0310]

[0311] If the constants used for normalization are adjusted empirically, the above constraints translation needs to be adjusted accordingly.

[0312] As an example, on the basis of method two at step 207, the second order generalized coordinates are:

[0313]

[0314]

[0315]

[0316]

[0317]

[0318]

[0319]

[0320]

[0321]

[0322]

[0323]

[0324]

[0325]

[0326]

[0327]

[0328]

[0329] The constants used for normalization are adjusted empirically, and the normalization constants are not used instead. This is because it is expected that slightly increase during optimization (this expectation is not borne out in the results of the example).

[0330]

[0331]

[0332]

[0333]

[0334]

[0335] They satisfy the following constraints:

[0336]

[0337]

[0338]

[0339]

[0340]

[0341]

[0342]

[0343]

[0344]

[0345]

[0346]

[0347]

[0348]

[0349]

[0350] ​

[0351]

[0352]

[0353]

[0354]

[0355]

[0356]

[0357]

[0358]

[0359]

[0360]

[0361]

[0362]

[0363] Initial value is

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370]

[0371]

[0372]

[0373]

[0374]

[0375]

[0376]

[0377]

[0378]

[0379]

[0380]

[0381]

[0382]

[0383]

[0384]

[0385] 209: Constructing a derivative-free optimization model

[0386] i. Constructing the objective function: Determining a function As the optimization objective, the optimization algorithm will find the combination of independent variables that minimizes the value of the variable.

[0387] In one embodiment, there are two methods to construct the objective function:

[0388] Method 1: Defined as the integral of the magnetic flux density modulus with respect to volume within region 2 of interest, using typical values ​​of magnetic flux density. and total volume Normalize:

[0389]

[0390] in The value of the remanent magnetic flux density modulus in region 2 of interest is taken as close to the desired shielding performance.

[0391] Method 2: Select the face closest to the beginning 3 in region of interest 2, and apply the objective function... Defined as the integral of the magnetic flux density modulus over the area on this surface, using typical values ​​of magnetic flux density. and total area Normalize:

[0392]

[0393] The value of the objective function will be calculated in step 210.

[0394] As an example, using the second method, the region of interest 2 (ROI) is the area of the face of the cylinder in step 201 close to the open end 3 , typical values .

[0395] ii. Constructing the set of parameters to be optimized: determining the arguments of the objective function, the optimization algorithm will find the minimum of the objective function in the space spanned by the set of parameters to be optimized.

[0396] In an embodiment, the set of parameters to be optimized is the set of secondary generalized coordinates constructed in step 208.

[0397] Alternatively, the set of primary generalized coordinates constructed in step 206, or the set of complete parameters determined in step 204 can be chosen.

[0398] As an example, the set of parameters to be optimized is the set of secondary generalized coordinates constructed in step 208, which contains the following parameters

[0399] .

[0400] iii. Determining the bounds of the parameters to be optimized: determining the upper and lower bounds of the parameters to be optimized, so as to determine the range of parameter search. The determined range needs to be a subset of the parameter range delineated by the constraints in step 205. Among them, the bounds in this application are divided into two categories, the first category is the bounds determined by the constraints, which includes the upper and lower bounds; the second category is the bounds determined by the constants in the derivative-free optimization model, which are all upper bounds, if the bounds of the second category are touched in the calculation process, it means that the constants in the derivative-free optimization model are too small; if the bounds of the first category are touched, it is a normal phenomenon. The second category of bounds is used to bound the non-monotonically increasing arguments.

[0401] Let

[0402]

[0403] is used to represent the maximum value of the radius difference between two adjacent layers. Then

[0404]

[0405] or

[0406]

[0407] is a non-monotonically increasing argument, whose lower bound is bounded by , and the upper bound is selected as a constant according to the actual geometric shape As long as the constant is large enough, the value of the constant will not affect the final result, only the search efficiency. The definition of large enough is that in the final optimization result, no parameter reaches the upper bound defined by the constant. If there is, it means that the constant is not large enough and needs to be increased and then the method of the present application is executed from this step again. The upper bound of the second type of boundary is

[0408] The upper and lower bounds of are

[0409]

[0410] or

[0411]

[0412] The non-monotonically increasing independent variable belongs to the second type of boundary, the lower bound of which is defined by , and the upper bound is a constant selected according to the actual geometric shape. As long as the constant is large enough, the value of the constant will not affect the final result, only the search efficiency. The definition of large enough is that in the final optimization result, no parameter reaches the upper bound defined by the constant. If there is, it means that the constant is not large enough and needs to be increased and then the method of the present application is executed from this step again. The upper and lower bounds of are

[0413]

[0414] or

[0415]

[0416] The non-monotonically increasing independent variable belongs to the second type of boundary, the lower bound of which is defined by , and the upper bound is a constant selected according to the actual geometric shape. As long as the constant is large enough, the value of the constant will not affect the final result, only the search efficiency. The definition of large enough is that in the final optimization result, no parameter reaches the upper bound defined by the constant. If there is, it means that the constant is not large enough and needs to be increased and then the method of the present application is executed from this step again. The upper and lower bounds of are

[0417]

[0418] or

[0419]

[0420] The upper and lower bounds of are

[0421]

[0422] or

[0423]

[0424] If the constants used for normalization are adjusted empirically in step 208, the above constraint transformation needs to be adjusted accordingly.

[0425] As an example, the bounds of the parameters to be optimized are:

[0426]

[0427]

[0428]

[0429]

[0430]

[0431]

[0432]

[0433]

[0434]

[0435]

[0436]

[0437]

[0438]

[0439]

[0440]

[0441]

[0442]

[0443]

[0444]

[0445]

[0446]

[0447] Here we choose

[0448]

[0449]

[0450]

[0451] iv. Select search method. Various derivative-free optimization algorithms can be chosen.

[0452] In one embodiment, when , the exhaustive method is chosen; when , the Nelder-Mead method is chosen; when , the coordinate search method is chosen.

[0453] Construct penalty function of constraint condition in step 205 or 206 or 208 and add to objective function.

[0454] Various methods can be implemented by commercial software such as: Ansys Maxwell, COMSOL Multiphysics, MATLAB-based software package, etc., open source or semi-open source software such as deal. II, Elmer.

[0455] As an example, the coordinate search method is chosen.

[0456] Step 209 obtains a model, the output of which is the value of the parameter to be optimized, and the input is the value of the objective function.

[0457] 210: Construct finite element model

[0458] i. Use the parameters in step 204 to construct the geometric structure. After the generalized coordinates defined in step 206 or 208 are restored to the parameters in the complete parameter set according to the corresponding definition method, they are used to construct the geometric structure.

[0459] As an example, after the generalized coordinates defined in step 208 are restored to the parameters in the complete parameter set, they are used to construct the geometric structure.

[0460] ii. The equation to be solved is:

[0461] In one embodiment, the wave equation of the magnetic vector potential is solved on the symmetric section 6:

[0462]

[0463] Simplify to

[0464]

[0465] where is the component of the magnetic vector potential normal to the symmetry plane 6, and Figure 10 is the component of the magnetic vector potential along the axis of the cylindrical coordinate system in three-dimensional space.

[0466] The boundary conditions are:

[0467]

[0468] where is the normal unit vector to the boundary of the solution domain.

[0469] The final magnetic induction is given by:

[0470]

[0471] In another embodiment, the wave equation for the magnetic scalar potential

[0472]

[0473] The boundary conditions are:

[0474]

[0475] where is the normal unit vector to the boundary of the solution domain.

[0476] The final magnetic induction is given by:

[0477]

[0478] where is the magnetic permeability.

[0479] As an example, the wave equation for the magnetic vector potential is solved.

[0480] iii. Treatment of the thin layers of the shield cylinder:

[0481] In one embodiment, each layer of the shield cylinder is treated as a boundary condition with no geometric thickness, the material thickness and the magnetic properties contribute to the boundary condition in step 202.

[0482] The contribution of the magnetic properties to the boundary condition is given by a constitutive relation:

[0483]

[0484] or

[0485]

[0486] When the magnetic vector potential equation is solved, the boundary conditions are:

[0487]

[0488]

[0489]

[0490] where is the magnetic induction on both sides of the boundary, denotes the leakage of the shell to the tangential magnetic field, denotes the leakage of the shell to the tangential magnetic induction, denotes the material thickness, given by step 202.

[0491] When solving the magnetic scalar potential equation, the boundary conditions are:

[0492]

[0493]

[0494]

[0495] where is the magnetic induction on both sides of the boundary, denotes the tangential calculation gradient along the boundary.

[0496] In another embodiment, each layer of the magnetic shielding cylinder can also be treated as a geometric entity with thickness. When the layer thickness is much smaller than the overall size of the shielding cylinder, only the first method can be used, otherwise the second method can be used.

[0497] As an example, each layer of the magnetic shielding cylinder is treated as a boundary condition without geometric thickness.

[0498] iv. Background magnetic induction

[0499] A uniform background magnetic induction is applied along the axial direction At this time, the magnetic induction modulus in the region of interest 2 can be calculated, which can reflect the axial shielding performance of the system. Studies have shown that the axial shielding performance of the single-end open magnetic shielding cylinder is the weakest, so it is most reasonable to take the axial shielding performance as the optimization goal.

[0500] When solving the magnetic vector potential equation, the background magnetic induction is converted into the magnetic vector potential and added to the equation and boundary conditions for solving; when solving the magnetic scalar potential equation, the background magnetic induction is converted into the background magnetic field strength and added to the equation and boundary conditions for solving.

[0501] When the magnetic properties of the material obtained in step 202 are characterized by magnetic permeability, the background magnetic induction can take any value; when the magnetic properties are characterized by the initial B-H curve or H-B curve, the background magnetic induction should be less than the maximum magnetic field strength of the initial magnetization region after being converted into magnetic field strength.

[0502] As an example, the selection .

[0503] v. Discretization and solution

[0504] In another embodiment, Lagrange quadratic elements are used for discretization. Linear elements or higher order elements can also be used. The meshing method and solver are implemented using methods provided in commercial software such as Ansys Maxwell, COMSOL Multiphysics, MATLAB-based software packages, open source or semi-open source software such as deal.II, Elmer, etc.

[0505] As an example, using Lagrange quadratic element discretization, the grid is meshed using COMSOL Multiphysics and solved.

[0506] vi. Calculate the objective function

[0507] If method one is used in step 209, assume that the region of interest 2 contains units, assume that the average value of the magnetic induction modulus of each node calculated on the th unit in the region of interest 2 is , and the area of the node is , then the objective function is given by

[0508]

[0509] , where is the distance of the unit to the axis of symmetry.

[0510] If method two is used in step 209, assume that the face of the region of interest 2 closest to the opening 3 contains units, assume that the average value of the magnetic induction modulus of each node calculated on the th unit in the region of interest 2 is , and the length of the node is , then the objective function is given by

[0511]

[0512] , where is the distance of the unit to the axis of symmetry.

[0513] If the software used provides other calculation methods, they can also be used.

[0514] As an example, the calculation method provided by COMSOL Multiphysics is used.

[0515] The model obtained in step 210, with the input of the values of the parameters to be optimized, outputs the value of the objective function.

[0516] 211: repeated calculation or iterative calculation

[0517] The initial value of step 207 or the initial value processed by step 208 is input into the model of step 210, and the value of the objective function is calculated. The result is input into the model of step 209, and the new parameters to be optimized are calculated. The new parameters to be optimized are input into the model of step 210. When the derivative-free optimization algorithm selected in step 209 does not depend on the input value of the objective function to determine the value of the selected parameter to be optimized in the next calculation (such as the exhaustive method), this process is a repeated calculation; when the derivative-free optimization algorithm selected in step 209 depends on the input value of the objective function to determine the value of the selected parameter to be optimized in the next calculation (such as the Nelder-Mead method), this process is an iteration. In the case of repeated calculation, the parameter value combination with the smallest objective function needs to be selected as the output after all calculations are completed. In the case of iterative calculation, the termination condition of iteration needs to be set in advance. After times of iteration, the output of the parameters to be optimized is

[0518]

[0519] As an example, the iteration termination condition is the optimization tolerance , and the actual number of iterations is 572. The optimization parameter value of the output parameter to be optimized is:

[0520]

[0521]

[0522]

[0523]

[0524]

[0525]

[0526]

[0527]

[0528]

[0529]

[0530]

[0531]

[0532]

[0533]

[0534]

[0535]

[0536]

[0537]

[0538]

[0539]

[0540]

[0541] 212: Evaluate and output results

[0542] i. Determine whether the output parameter reaches the upper bound of the second type specified in step 209.iii. If it reaches the upper bound, it means that the constant is too small and a larger constant should be selected to start from step 209 again. If it does not reach, the setting of the constant is reasonable.

[0543] ii. Determine whether the objective function value output by the finite element model in step 210 to the derivative-free optimization model in the last step of iteration or the minimum objective function value of the corresponding repeated calculation meets the preset threshold. If it does not meet, analyze the reason and modify the input of the derivative-free optimization model according to the analysis result. Specifically, it can be considered to replace the material, modify the number of layers, relax the constraint condition, adopt more stringent iteration termination criterion or more repeated calculation times, and execute the method again in the corresponding step. If it meets the preset threshold, the derivative-free optimization model outputs the result. If generalized coordinates are used, the parameters in the complete parameter set are restored from the generalized coordinates before output.

[0544] As an example, none of the output parameters reaches the upper bound of the non-monotonically increasing independent variable defined by the constant in step 209.iii. After the last step of iteration, the objective function value meets the expectation. The parameters to be optimized are restored from the two-level generalized coordinates to the parameters in the complete parameter set, and the result parameters are obtained:

[0545]

[0546]

[0547]

[0548]

[0549]

[0550]

[0551]

[0552]

[0553]

[0554]

[0555]

[0556]

[0557]

[0558]

[0559]

[0560]

[0561]

[0562]

[0563]

[0564]

[0565]

[0566]

[0567]

[0568] The optimized magnetic shielding cylinder obtained according to this example has a three-dimensional view as shown in Figure 12 , and a two-dimensional sectional view as shown in Figure 13 .

[0569] In an example embodiment of the present application, a complete set of optimization design methods for magnetic shielding devices with openings is provided. The optimization methods are more scientific and efficient, and the optimized magnetic shielding cylinder has a significantly improved magnetic shielding performance compared to the magnetic shielding cylinder designed using an equal interval design scheme. Specifically, the typical shielding factor is improved by more than 5 times. For example, in a 6-layer magnetic shielding cylinder in some examples, the shielding factor of the magnetic shielding cylinder designed using the equal interval scheme is 1722, while the shielding factor of the optimized magnetic shielding cylinder is 12720, and less raw materials are used. At the same time, the optimization target is the axial shielding factor in the quasi-static magnetic field, and the weakest direction of the shielding performance of the sighting system is optimized, and the optimization effect is significant. The shielding factor in the above is calculated based on the ratio of the background magnetic induction intensity module to the magnetic induction intensity module in the region of interest. The comparison results in the above are obtained based on the following method: before the optimization of the magnetic shielding device, after selecting the region of interest in the interior of the magnetic shielding device, the magnetic shielding factor in the region of interest is calculated; after the optimization of the magnetic shielding device is completed, the magnetic shielding factor in the region of interest is calculated again based on the same background magnetic induction intensity module.

[0570] Exemplary computer-readable storage medium

[0571] In an example embodiment of the present application, a computer readable storage medium is provided, and the storage medium stores a computer program for executing the method for designing a magnetic shielding device in the above example method.

[0572] Exemplary electronic device

[0573] In an example embodiment of the present application, an electronic device is provided, which includes a processor and a memory for storing processor-executable instructions, wherein the processor is configured to execute the method for designing a magnetic shielding device in the above example method.

[0574] Exemplary software product

[0575] In an example embodiment of the present application, a software product is provided, and the software runs the method for designing a magnetic shielding device in the example method.

[0576] Exemplary magnetic shielding arrangement

[0577] The present embodiment provides a magnetic shielding device, which includes nested layered shell 1, wherein, > 1, and the magnetic shielding device is designed by the method for designing a magnetic shielding device in the example method.

[0578] In an example embodiment, there is a length difference 8 between the adjacent shells 1 in the layer shell 1 at either end of the use direction of the magnetic shielding device, and / or there is an assembly gap 7 between the adjacent shells 1 in the layer shell 1 in the direction perpendicular to the use direction of the magnetic shielding device, and the parameters optimized in the complete parameter set of the magnetic shielding device include the assembly gap 7 and / or the length difference 8. In particular, the various schemes included in this embodiment, the first scheme: there is a length difference 8 between the adjacent shells 1 in the layer shell 1 at either end of the use direction of the magnetic shielding device, which is more suitable for a single-end open magnetic shielding device, and the length difference 8 is located in the opening direction; the second scheme: there is a length difference 8 between the adjacent shells 1 in the layer shell 1 at either end of the use direction of the magnetic shielding device, which is more suitable for a double-end open scheme or a double-end non-open scheme. The third scheme: there is a length difference 8 between the adjacent shells 1 in the layer shell 1 at either end of the use direction of the magnetic shielding device, and there is an assembly gap 7 between the adjacent shells 1 in the layer shell 1 in the direction perpendicular to the use direction of the magnetic shielding device; the fourth scheme: there is a length difference 8 between the adjacent shells 1 in the layer shell 1 at either end of the use direction of the magnetic shielding device, and there is an assembly gap 7 between the adjacent shells 1 in the layer shell 1 in the direction perpendicular to the use direction of the magnetic shielding device, wherein the length difference 8 and the assembly gap 7 in each scheme are different from those determined only by experience in the prior art, and the length difference 8 and the assembly gap 7 in this application are ultimately optimized by the method for designing the magnetic shielding device. At the same time, for the assembly gap 7, in the direction perpendicular to the use direction of the magnetic shielding device, at least one is greater than 5% of the size of the inner layer of the two adjacent shells in the perpendicular direction; for the length difference 8, in the use direction of the magnetic shielding device, at least one is greater than 10% of the total length of the shorter shell in the use direction. In the above exemplary method, the single-end open magnetic shielding cylinder with a 6-layer shell structure has a length difference 8 of 24.9% of the total length of the innermost layer relative to the second innermost layer in the use direction; in the direction perpendicular to the use direction, the assembly gap 7 (for this device, the radius difference) of the second outer layer relative to the outermost layer reaches 10.5% of the diameter of the second outer layer.

[0579] Regarding the specific characteristics of the optimized length difference 8 and assembly gap 7, in one embodiment, The shells 1 in the layer shell are at least three layers, and the assembly gap 7 between at least two adjacent shells 1 is not equal and / or the length difference 8 between at least two adjacent shells 1 is not equal.

[0580] In one embodiment, the magnetic shielding device The basic geometric structures of the shell layers 1 are the same and all have symmetry; along Along the axial direction of the axis of symmetry of shell 1, in One end of the shell 1 has an opening, forming the open end 3 of the magnetic shielding device; the other end, opposite to the open end 3, is the closed end 4 of the magnetic shielding device; near the open end 3 of the magnetic shielding device... The shell layer 1 forms a length difference of 8.

[0581] To improve the magnetic shielding effect of the magnetic shielding device, in one embodiment, in At least one of the shells 1 in the shell 1 has an opening 3 that extends towards the outer edge of the shell 1. The shielding structure extends along the axis of symmetry of the shell 1, and the shielding structures of different layers are perpendicular to each other. An assembly gap 7 is formed in the direction of the axis of symmetry of the shell 1. In one embodiment, The outer edge of the innermost shell in the layered shell is stretched along a direction perpendicular to the plane containing the opening to form a curved surface, and the shielding structure extends to the curved surface. In one embodiment, In shell 1, excluding the innermost shell A shielding structure is provided at the opening of the housing 1. This improves the magnetic shielding effect of the magnetic shielding device without affecting its internal usable space. In one embodiment, The basic geometric structure of the shell 1 is a cylindrical structure with cylindrical symmetry, and the shielding structure is a ring structure 5. That is, the basic geometric structure of the magnetic shielding device is a single-end open, multi-layered nested cylinder.

[0582] Generally, the higher the symmetry of the basic geometric structure of a magnetic shielding device, the better the magnetic shielding effect, but the greater the manufacturing difficulty. Cylindrical magnetic shielding devices possess cylindrical symmetry and are easy to manufacture, achieving good magnetic shielding effects at a relatively low cost. They can be manufactured into small to medium-to-large-sized magnetic shielding devices. Numerous studies have shown that increasing the thickness of a single-layer shielding shell 1 provides only a limited increase in shielding performance, while using thin shells to fabricate multi-layer shielding devices results in a significant increase in shielding performance with the increase in the number of layers. Therefore, the magnetic shielding device used in this embodiment is a single-end open, multi-layer nested cylindrical magnetic shielding cylinder. Meanwhile, as... Figure 13 The optimized magnetic shielding device shown has the same magnetic shielding performance as... Figure 11 As shown, the magnetic shielding device offers a significant improvement over the scheme of using equal spacing between the housings, with a typical shielding coefficient increase of more than 5 times.

[0583] Exemplary apparatus

[0584] The embodiment provides a device for designing a magnetic shielding device, which comprises a first determining module, a second determining module and a parameter optimization module, wherein the first determining module is used for determining a region of interest in the magnetic shielding device, the region of interest is a region in which a magnetic field shielding effect is expected to be achieved, and the magnetic shielding device comprises nested layered shells; the second determining module is used for determining a complete parameter set, the complete parameter set is used for describing geometric structures of at least one of the layered shells and relative position relationships between the region of interest and each of the at least one of the layered shells; and the parameter optimization module is used for obtaining a set of result parameters for describing the geometric structures based on the complete parameter set, wherein the result parameters can make the magnetic induction intensity in the region of interest satisfy a preset threshold.

[0585] In conclusion, the application provides a method for designing a magnetic shielding device and the magnetic shielding device, the method comprises the following steps: determining a region of interest in the magnetic shielding device, the region of interest is a region in which a magnetic field shielding effect is expected to be achieved, and the magnetic shielding device comprises nested layered shells; determining a complete parameter set, the complete parameter set is used for describing geometric structures of at least one of the layered shells and relative position relationships between the region of interest and each of the at least one of the layered shells; and obtaining a set of result parameters for describing the geometric structures based on the complete parameter set, wherein the result parameters can make the magnetic induction intensity in the region of interest satisfy a preset threshold. The method is more scientific and efficient, not only makes the optimized magnetic shielding performance greatly improve compared with an equal-interval scheme, but also solves the problem that an analytical method cannot optimize and design a single-end open magnetic shielding device with a non-concentric structure.

[0586] All the optional technical solutions described above can be combined to form optional embodiments of the application, and thus will not be described here again.

[0587] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the description of the present application, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0588] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used in the description herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0589] Those skilled in the art can clearly understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0590] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0591] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0592] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0593] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically, or two or more units can be integrated into one unit.

[0594] If the functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random-Access Memory), a magnetic disk or an optical disk, and various storage program code storage media.

[0595] It should be noted that in the description of the present application, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0596] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for designing a magnetic shielding device, characterized in that, include: The region of interest within the magnetic shielding device is defined as the area where the magnetic field shielding effect is expected to be achieved. The magnetic shielding device includes nested components. The shell layer, the basic geometric structure of the magnetic shielding device is a cylindrical structure with cylindrical symmetry and a single-end opening, the... The centers of the basic geometry of the shell layers do not coincide, wherein the opening connects the region of interest with the... The external space of the shell layer, the The opening of at least one of the shells is provided with an annular structure extending along the outer edge of the shell towards the axis of symmetry of the cylindrical structure, the annular structure blocking the gap between adjacent shells perpendicular to the axis of symmetry. Determine a complete parameter set, which is used to describe the... The geometry of at least one shell in the layered shell and the relative positional relationship between the region of interest and each of the at least one shell, wherein the parameters of the complete parameter set include the base radius of the cylinder. The axial distance from the bottom surface to the center of the region of interest The The axial distance from each layer of the shell to the center of the region of interest and the width of the ring structure ,in Representing the Shell layer; Based on the complete parameter set, a set of result parameters describing the geometric structure are obtained, wherein the result parameters enable the magnetic induction intensity in the region of interest to meet a preset threshold. The step of obtaining a set of result parameters describing the geometric structure based on the complete parameter set includes: Using the complete parameter set as the independent variable and the magnetic induction intensity in the region of interest as the dependent variable, the parameters are input into the derivative-free optimization model to obtain a set of optimal parameters. The independent variable includes a non-monotonic increasing independent variable. When the non-monotonic increasing independent variable increases, the dependent variable does not increase monotonically. A constant is set to define the upper bound of the non-monotonic increasing independent variable in the derivative-free optimization model. Verify whether the non-monotonic increasing independent variable in the optimal parameters has reached the upper bound defined by the constant; If so, increase the constant of the derivativeless optimization model and then recalculate the derivativeless optimization model; If not, verify whether the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters meets the preset threshold; if yes, output the result, and the output result is the result parameter; if no, adjust the input of the derivativeless optimization model and recalculate the derivativeless optimization model.

2. The method as described in claim 1, characterized in that, The input to the derivativeless optimization model yields a set of optimal parameters, including: calculating the optimized parameters based on the complete parameter set through the derivativeless optimization model, and converting the optimized parameters into the magnetic induction intensity by obtaining the magnetic field distribution of the magnetic shielding device from the geometric structure. During the calculation of the derivativeless optimization model, repeated calculations or iterative calculations are used to obtain the optimal parameters and the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameters.

3. The method as described in claim 2, characterized in that, The method for obtaining the magnetic field distribution of the magnetic shielding device from the geometry includes the finite element method.

4. The method as described in claim 1, characterized in that, The The basic geometric structures of the shell layers are the same and all have symmetry, and the region of interest is in three-dimensional space.

5. The method as described in claim 4, characterized in that, The center of the region of interest is in On the symmetry plane of the shell layer.

6. The method as described in claim 4, characterized in that, The region of interest has axial symmetry, and the axis of symmetry of the region of interest is perpendicular to the axis of symmetry of the region of interest. The symmetry axes of the shell layers coincide.

7. The method as described in claim 1, characterized in that, Determining the complete parameter set includes: The basic parameters of the magnetic shielding device are determined based on a preset threshold for the magnetic flux density of the region of interest. The complete parameter set is determined based on the basic parameters, wherein the basic parameters include parameters characterizing the basic geometric structure of the magnetic shielding device, the number of shell layers included in the magnetic shielding device, and so on. The material of the shell layers, the thickness of each shell layer, the size of the region of interest, and the position of the region of interest relative to the magnetic shielding device.

8. The method as described in claim 1, characterized in that, The step of obtaining a set of result parameters describing the geometric structure based on the complete parameter set includes: Define the constraints; Based on the constraints and the complete parameter set, a set of result parameters describing the geometry is obtained, wherein the constraints limit the range of parameters in the complete parameter set.

9. The method as described in claim 1, characterized in that, Also includes: Based on the complete parameter set, the difference features in the geometric structure are selected as the first-level generalized coordinates.

10. The method as described in claim 9, characterized in that, Also includes: The first-level generalized coordinates are normalized to construct the second-level generalized coordinates.

11. The method as described in claim 1, characterized in that, The The shell layers excluding the innermost shell The opening of the shell layer is provided with the aforementioned annular structure.

12. The method as described in claim 1, characterized in that, When the When each layer of the shell is provided with the aforementioned annular structure. The axial distance from the geometric center of the annular structure to the center of the region of interest; When the When at least one layer of the shell does not have the aforementioned annular structure, for the shell that does not have the annular structure, The distance is the axial distance from the outer edge of the shell without an annular structure to the center of the region of interest; for the The shell with the aforementioned annular structure is located within the shell layer. The distance is the axial distance from the geometric center of the annular structure to the center of the region of interest.

13. The method as described in claim 12, characterized in that, The parameters in the complete parameter set are subject to range restrictions imposed by constraints, wherein the constraints include: External dimension constraints are used to define the maximum external boundary of the magnetic shielding device; Internal dimension constraints are used to define the minimum internal space of the magnetic shielding device; Spacing constraints are used to define the minimum spacing between adjacent shells; A minimum width constraint is used to define the minimum width of the ring structure; Region of interest constraint is used to define the minimum axial distance between the region of interest and the bottom surface of the innermost housing of the magnetic shielding device.

14. The method as described in claim 13, characterized in that, The constraints also include an additional constraint that limits the radius difference between the outermost layers of adjacent shells to be greater than the radius difference between the innermost layers. .

15. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for executing the method for designing a magnetic shielding device as described in any one of claims 1-14.

16. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is used to execute the method for designing a magnetic shielding device as described in any one of claims 1-14.

17. A software product, characterized in that, The software product operates the method for designing a magnetic shielding device as described in any one of claims 1-14.

18. A magnetic shielding device, characterized in that, include: Nested together Layered shell, wherein, >1, and the magnetic shielding device is designed by the method for designing a magnetic shielding device as described in any one of claims 1-14.

19. The magnetic shielding device as described in claim 18, characterized in that, The There is a length difference between adjacent shells in the layered housing at at least one end at both ends of the magnetic shielding device in the direction of use, and / or, the There is an assembly gap between adjacent shells in the layered shell in a direction perpendicular to the use direction of the magnetic shielding device, and the length difference and the assembly gap are designed by the method for designing the magnetic shielding device.

20. The magnetic shielding device as described in claim 19, characterized in that, The The shell in the layered shell has at least three layers, and the assembly gap between at least two adjacent shells is not equal and / or the length difference between at least two adjacent shells is not equal.

21. The magnetic shielding device as described in claim 20, characterized in that, The magnetic shielding device The basic geometry of the shell layers is the same and they are all symmetrical; along the... Along the axial direction of the symmetry axis of the shell layer, in the One end of the shell layer has an opening, forming the open end of the magnetic shielding device, and the other end, opposite to the open end, is the closed end of the magnetic shielding device; near the open end of the magnetic shielding device, the... The layered shell forms the length difference.

22. The magnetic shielding device as described in claim 21, characterized in that, In the At least one of the shells in the layered shell has an opening that extends along the outer edge of the shell towards the outer edge of the shell. A shielding structure extending along the axis of symmetry of the shell, and the shielding structures of different layers are separated by the [missing information]. The assembly gap is formed in the axial direction of the axis of symmetry of the shell.

23. The magnetic shielding device as described in claim 22, characterized in that, The The outer edge of the innermost shell in the shell is stretched along a direction perpendicular to the plane where the opening is located to form a curved surface, and the shielding structure extends to the curved surface.

24. The magnetic shielding device as described in claim 23, characterized in that, The The shell layers excluding the innermost shell The shielding structure is provided at the opening of the shell layer.

25. The magnetic shielding device as described in claim 24, characterized in that, The The basic geometric structure of the shell is a cylindrical structure with cylindrical symmetry, and the shielding structure is a ring structure.

26. An apparatus for designing magnetic shielding devices, characterized in that, include: The first determining module is used to determine the region of interest inside the magnetic shielding device, the region of interest being the area where the magnetic field shielding effect is expected to be achieved, and the magnetic shielding device includes nested components. The shell layer, the basic geometric structure of the magnetic shielding device is a cylindrical structure with cylindrical symmetry and a single-end opening, the... The centers of the basic geometry of the shell layers do not coincide, wherein the opening connects the region of interest with the... The external space of the shell layer, the The opening of at least one of the shells is provided with an annular structure extending along the outer edge of the shell towards the axis of symmetry of the cylindrical structure, the annular structure blocking the gap between adjacent shells perpendicular to the axis of symmetry. The second determining module is used to determine a complete parameter set, the complete parameter set being used to describe the... The geometry of at least one shell in the layered shell and the relative positional relationship between the region of interest and each of the at least one shell, wherein the parameters of the complete parameter set include the base radius of the cylinder. The axial distance from the bottom surface to the center of the region of interest The The axial distance from each layer of the shell to the center of the region of interest and the width of the ring structure ,in Representing the Shell layer; The parameter optimization module is used to obtain a set of result parameters describing the geometric structure based on the complete parameter set. These result parameters enable the magnetic flux density within the region of interest to meet a preset threshold. Obtaining the set of result parameters describing the geometric structure based on the complete parameter set includes: inputting the complete parameter set as the independent variable and the magnetic flux density within the region of interest as the dependent variable into a derivative-free optimization model to obtain a set of optimal parameters. The independent variables include non-monotonic increasing independent variables. When the non-monotonic increasing independent variables increase, the dependent variable does not increase monotonically, and a constant is set. The constant is used to define the upper bound of the non-monotonic increasing independent variable in the derivative-free optimization model; to verify whether the non-monotonic increasing independent variable in the optimal parameter has reached the upper bound defined by the constant; if so, the constant of the derivative-free optimization model is increased and the derivative-free optimization model is recalculated; if not, the magnetic induction intensity in the region of interest of the magnetic shielding device with the optimal parameter is verified to meet the preset threshold; if so, the result is output, and the output result is the result parameter; if not, the input of the derivative-free optimization model is adjusted and the derivative-free optimization model is recalculated.

Images