A method and system for measuring magnetic permeability of a flat plate

Abstract

The present invention discloses a method and system for measuring the magnetic permeability of a flat plate, comprising: placing a flat plate of soft magnetic material within a spatial range of a uniform magnetic field; measuring the magnetic field strength of the soft magnetic material flat plate before and after placement at a plurality of measurement points within the spatial range; establishing a magnetic field distribution model around the soft magnetic material flat plate to obtain the theoretical magnetic field strength of the plurality of measurement points; calculating the theoretical magnetic induction intensity and the actual magnetic induction intensity of the measurement points after the soft magnetic material flat plate is placed, and establishing a fitness function with the flat plate magnetic permeability as an unknown quantity; optimizing and solving the problem with the minimum fitness function as the goal to obtain the flat plate magnetic permeability. The present invention tests flat plate samples for actual installation of shielding bodies, and can directly obtain the magnetic permeability of the shielding layer structure, which can truly reflect the magnetic properties of the soft magnetic material flat plate; the process of measuring and obtaining the magnetic permeability is simple and fast, and the data can be read and detected after the plate to be tested is placed, resulting in high testing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic material testing, and in particular to a method and system for measuring the magnetic permeability of a plate. Background Art

[0002] Magnetic permeability is a physical quantity that describes the degree of magnetization of a material in a magnetic field. Understanding a material's magnetic permeability can be used to assess its magnetic properties in practical applications, which is crucial for confirming that the material meets requirements and application standards. Materials with high magnetic permeability conduct magnetic fields more efficiently, reducing magnetic field attenuation and loss, offering significant advantages in applications requiring efficient magnetic conduction. In magnetic shielding applications, high-permeability materials can more effectively shield external magnetic fields, protecting sensitive internal equipment from magnetic interference. Measuring the magnetic permeability of a flat plate of soft magnetic material can reveal the material's magnetic conductivity in a magnetic field, thereby understanding its behavior in actual working environments. Therefore, accurately and quickly measuring the magnetic permeability of a flat plate of soft magnetic material is crucial. Currently, the most commonly used method for testing the magnetic properties of soft magnetic materials is the test ring method, as specified in the national standard GB / T 13012-2008, "Measurement of DC Magnetic Properties of Soft Magnetic Materials." However, this method requires processing the soft magnetic material into a ring shape, which does not accurately reflect the magnetic properties of the flat plate. Furthermore, the testing process is complex and inefficient, and the accuracy of the test results can be easily affected by human error.

[0003] The Chinese patent document "A method for measuring the magnetic permeability of a cylindrical soft magnetic material" has a publication number of CN102565728B and a publication date of September 25, 2013. The specific magnetic permeability measurement method is as follows: 1. Measuring the aspect ratio of the cylindrical soft magnetic material; 2. Placing the cylindrical soft magnetic material with a secondary coil wound around its outer wall inside an excitation solenoid with an excitation coil wound around its outer wall, with the central axis of the cylindrical soft magnetic material, the central axis of the secondary coil, and the central axis of the excitation solenoid coinciding with each other, and the center of the cylindrical soft magnetic material, the secondary coil, and the excitation solenoid coinciding with each other. The central axis of the primary coil and the center of the excitation solenoid coincide with each other; 3. The excitation coil is connected in series with a precision resistor to form a loop, and an AC voltage is applied to the loop through a phase-locked amplifier, and the induced voltage of the secondary coil and the voltage across the precision resistor are received; 4. The external magnetic permeability of the cylindrical soft magnetic material is obtained; 5. The external magnetic susceptibility of the cylindrical soft magnetic material is obtained; 6. The magnetic permeability of the cylindrical soft magnetic material is obtained; The error range of the magnetic permeability obtained by this technology is 10%, which is much better than the error range of the magnetic permeability of the cylindrical soft magnetic material obtained by the existing measurement method. However, this technology measures the magnetic permeability of cylindrical soft magnetic materials and cannot accurately reflect the magnetic properties of soft magnetic material flat plates. It also requires winding a coil for testing. The test process is complicated and the test efficiency is low. It is easy for human errors to affect the accuracy of the test results. Summary of the Invention

[0004] The present invention aims to overcome the problems in the prior art of magnetic permeability detection of soft magnetic materials, such as complex operation, low test efficiency, easy loss of accuracy of test results due to human error, and inability to truly reflect the magnetic properties of soft magnetic material flat plates. A method and system for measuring the magnetic permeability of flat plates are provided.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for measuring the magnetic permeability of a plate, comprising:

[0007] Place a flat plate of soft magnetic material within the spatial range of a uniform magnetic field;

[0008] For a plurality of measurement points within the spatial range, the magnetic field strength is measured before and after the soft magnetic material plate is placed;

[0009] Establishing a magnetic field distribution model around the soft magnetic material plate and obtaining theoretical magnetic field strengths at several measuring points;

[0010] Calculate the theoretical and actual magnetic induction intensities at the measurement point after placing the soft magnetic material plate, and establish a fitness function with the plate magnetic permeability as the unknown quantity;

[0011] The magnetic permeability of the plate is obtained by optimizing the solution with the goal of minimizing the fitness function.

[0012] The present invention establishes a magnetic field distribution module around a soft magnetic material flat plate after it is placed in a uniform magnetic field in advance through theoretical calculation, thereby obtaining the theoretical magnetic field strength after the soft magnetic material flat plate is placed, obtaining the theoretical magnetic field strength at several measurement points, and then directly detecting the actual magnetic field strength at the same measurement point through a sensor. Based on the relationship between magnetic induction intensity and magnetic field intensity, the theoretical magnetic induction intensity and the actual magnetic induction intensity can be obtained. In an ideal situation, the two should be equal to obtain the flat plate magnetic permeability. In a practical situation, a fitness function is established based on the difference between the theoretical magnetic induction intensity and the actual magnetic induction intensity. When the fitness function is minimized, the flat plate magnetic permeability is obtained. The present invention is simple and fast in measuring and obtaining the flat plate magnetic permeability. After the flat plate to be tested is placed, data reading and detection can be completed, making the test process very fast and the test efficiency high.

[0013] Preferably, the fitness function is the norm of the difference vector obtained by subtracting the actual magnetic induction intensity vector from the theoretical magnetic induction intensity vector;

[0014] The actual magnetic induction intensity vector and the theoretical magnetic induction intensity vector are respectively vectors obtained by arranging the actual magnetic induction intensity and the theoretical magnetic induction intensity in the same measurement point order.

[0015] Preferably, establishing a magnetic field distribution model around the soft magnetic material plate includes:

[0016] The total magnetic field intensity at any point P in the space around the soft magnetic material plate is expressed as the superposition of the magnetic field intensity of the uniform magnetic field at point P and the magnetic field intensity at point P after the soft magnetic material plate is magnetized.

[0017] Preferably, the magnetic field intensity at point P after the soft magnetic material plate is magnetized comprises: dividing the soft magnetic material plate into micro-element areas;

[0018] According to the Poisson equation of static magnetic field, the surface integral of the soft magnetic material plate is performed by multiplying the magnetization intensity of the soft magnetic material plate corresponding to the area element by the normal vector of the plate and then dividing the result by the distance from the soft magnetic material plate corresponding to the area element to point P.

[0019] The magnetization intensity is equal to the product of the difference between the plate magnetic permeability and one and the magnetic field intensity.

[0020] Preferably, the spatial range of the uniform magnetic field is determined by a Helmholtz coil generating the magnetic field;

[0021] When current of the same direction and magnitude is passed through each coil ring in the Helmholtz coil pair, a uniform excitation magnetic field is generated in the Helmholtz coil pair.

[0022] Preferably, the obtaining of the plate magnetic permeability comprises:

[0023] Generate an initial particle swarm with one particle corresponding to one magnetic permeability value, and calculate the fitness function value of the particle;

[0024] For the fitness function value of each particle in the k-th generation particle swarm, if it does not meet the convergence requirements, the iterative calculation will continue until the fitness function value of any particle in the particle swarm meets the convergence requirements, and the global optimal position of the particle is used as the plate magnetic permeability.

[0025] A system for measuring the magnetic permeability of a flat plate, comprising: a Helmholtz coil pair, wherein two identical coil rings are arranged in parallel and coaxially;

[0026] A flat plate support frame is provided between the pair of Helmholtz coils, wherein the flat plate plane of the flat plate support frame is parallel to the axis of the pair of Helmholtz coils;

[0027] A measurement module is arranged above the flat panel support frame and between the Helmholtz coil pairs to measure the magnetic field strength at a number of measurement points;

[0028] The processing module obtains the plate magnetic permeability of the soft magnetic material plate to be measured according to the measurement results collected by the measurement module.

[0029] The present invention can test flat plate samples used for actual installation of the shielding body, and can directly obtain the magnetic permeability of the shielding layer structure without the need to separately make a standard test ring, and can truly reflect the magnetic properties of the soft magnetic material flat plate; the sensor is directly used to complete the test of the magnetic field strength, so the test sample itself does not need to be wrapped with wires, which reduces the influence of human factors during the test and improves the reliability of the test; when measuring multiple soft magnetic material flat plates, it is only necessary to move and replace the test flat plates on the flat plate support frame, without moving other devices and equipment, making the test process very convenient and easy to operate.

[0030] Preferably, the flat plate of the flat plate support is located at the center between the Helmholtz coil pair, and the distance from the center of the flat plate to the two coil rings is the same;

[0031] A grid is drawn on the upper surface of the flat plate of the flat plate support frame to position the soft magnetic material flat plate.

[0032] Preferably, the measurement module includes a test fixture and a sensor array fixed on the test fixture;

[0033] The test fixture is located above the flat support frame and is connected to the Helmholtz coil pair;

[0034] The sensor array is located above the center of the flat panel of the flat panel support frame and detects the magnetic field strength at several measurement points.

[0035] Preferably, the soft magnetic material plate is placed on the upper surface of the plate of the plate support frame, and the center of the soft magnetic material plate is on the same vertical line as the center of the plate;

[0036] Several sensors in the sensor array are arranged at equal intervals, and all the sensors are on the same vertical line with the center of the plate.

[0037] The present invention has the following beneficial effects: by testing a flat plate sample for actual installation of a shielding body, the magnetic permeability of the shielding layer structure can be directly obtained without the need to separately produce a standard test ring, and the magnetic properties of the soft magnetic material flat plate can be truly reflected; a magnetic induction intensity sensor is used to complete the test, so the test sample itself does not need to be wound with wires, which reduces the influence of human factors during the test and improves the reliability of the test; when measuring multiple flat plates, it is only necessary to move and replace the test flat plate on the flat plate support frame without moving other devices, making the test process very convenient and easy to operate; the process of measuring and obtaining the magnetic permeability is simple and fast, and the data reading and detection can be completed after the flat plate to be tested is placed, making the test process very fast and the test efficiency high. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of the method for measuring the magnetic permeability of a flat plate in the present invention.

[0039] Figure 2 Schematic diagram of the system for measuring the magnetic permeability of a flat plate in the present invention.

[0040] Figure 3 Schematic diagram of the upper surface of the flat panel of the flat panel support frame in the present invention.

[0041] In the figure: 1. Helmholtz coil; 2. Flat plate support; 3. Measurement module; 31. Test fixture; 32. Sensor array. DETAILED DESCRIPTION

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] The commonly used method for testing the magnetic properties of soft magnetic materials is the test ring method, as specified in the national standard GB / T 13012-2008, "Measurement of DC magnetic properties of soft magnetic materials." This method uses a special standard test ring, around which a primary coil and a secondary coil are wound to apply a magnetic field and measure the magnetic induction intensity, respectively. Current flows through the primary coil to generate a magnetic field, while the secondary coil senses the magnetic induction intensity within the test ring. By measuring the primary coil current and the induced electromotive force, the magnetic field intensity H and the magnetic induction intensity B can be calculated, thereby obtaining a complete hysteresis loop for the material and, from this, calculating the material's magnetic permeability. This testing method has the following drawbacks: 1) Sample preparation is complex. The process of forming the material into a ring may introduce stress and defects, resulting in the test ring not being able to accurately reflect the magnetic properties of the flat plate used. 2) The test ring requires a coil to be wound for testing, resulting in low test efficiency. Furthermore, during the coil winding process, due to uneven winding or stress applied to the test ring, human errors can easily be introduced, affecting the test results.

[0044] In order to solve the above problems, the present invention provides Figure 1 A method for measuring the magnetic permeability of a flat plate is shown, comprising:

[0045] Place a flat plate of soft magnetic material within the spatial range of a uniform magnetic field;

[0046] For a plurality of measurement points within the spatial range, the magnetic field strength is measured before and after the soft magnetic material plate is placed;

[0047] Establish a magnetic field distribution model around a soft magnetic material plate and obtain the theoretical magnetic field strength at several measurement points;

[0048] Calculate the theoretical and actual magnetic induction intensities at the measurement point after placing the soft magnetic material plate, and establish a fitness function with the plate magnetic permeability as the unknown quantity;

[0049] The magnetic permeability of the plate is obtained by optimizing the solution with the goal of minimizing the fitness function.

[0050] It should be noted that in the present invention, a magnetic field distribution module around a soft magnetic material flat plate after being placed in a uniform magnetic field is established in advance through theoretical calculation, so that the theoretical magnetic field strength after the soft magnetic material flat plate is placed can be obtained, and the theoretical magnetic field strength of several measurement points can be obtained. The theoretical magnetic field strength is an expression of the magnetic permeability of the flat plate. Then, the actual magnetic field strength of the same measurement point is directly detected by a sensor. Based on the relationship between magnetic induction intensity and magnetic field intensity, the theoretical magnetic induction intensity and the actual magnetic induction intensity can be obtained. In an ideal case, the two should be equal to obtain the magnetic permeability of the flat plate. In a practical case, a fitness function about the difference between the theoretical magnetic induction intensity and the actual magnetic induction intensity is established with the two, and the magnetic permeability of the flat plate is obtained when the fitness function is minimized. The process of measuring and obtaining the magnetic permeability of the flat plate according to the present invention is simple and fast. After the flat plate to be tested is placed, the data reading and detection can be completed, making the test process very fast and the test efficiency high.

[0051] It's worth noting that existing methods exist for directly measuring the magnetic properties of flat panels. However, most of these methods require combining the panel to be tested with a magnetic yoke to form a closed circuit. The induction coil and probe are then used to measure the magnetic field intensity H and magnetic induction intensity B, directly obtaining the panel's hysteresis loop and, therefore, the panel's magnetic properties. While this method can directly measure the panel's magnetic properties, the setup is relatively complex, and testing efficiency still needs to be improved.

[0052] Furthermore, the present invention selects to measure the magnetic field intensity to obtain the magnetic field intensity before and after the soft magnetic material flat plate is placed, and after combining the theoretical magnetic field intensity of several measurement points obtained by the magnetic field distribution model around the soft magnetic material flat plate, the theoretical magnetic induction intensity and the actual magnetic induction intensity can be calculated through the conversion relationship between magnetic induction intensity and magnetic field intensity. Optionally, the magnetic induction intensity before and after the soft magnetic material flat plate can also be directly measured. The magnetic induction intensity before placement is combined with the theoretical magnetic field intensity of several measurement points obtained by the magnetic field distribution model around the soft magnetic material flat plate to obtain the theoretical magnetic induction intensity, and the magnetic induction intensity after placement is the actual magnetic induction intensity. The specific conversion relationship belongs to existing conventional knowledge and is therefore not described in detail.

[0053] As a specific embodiment, the fitness function is the norm of the difference vector obtained by subtracting the actual magnetic induction intensity vector from the theoretical magnetic induction intensity vector;

[0054] The actual magnetic induction intensity vector and the theoretical magnetic induction intensity vector are respectively vectors obtained by arranging the actual magnetic induction intensity and the theoretical magnetic induction intensity in the same measurement point order.

[0055] It should be noted that the actual magnetic induction intensity is the actual detected magnetic induction intensity, while the theoretical magnetic induction intensity is the theoretical magnetic induction intensity calculated using a model. This is an expression for the plate magnetic permeability. When there is only one measurement point, the plate magnetic permeability can be calculated by equating the actual magnetic induction intensity with the theoretical magnetic induction intensity. However, a single measurement point is prone to measurement errors and other issues, resulting in inaccurate results. Therefore, it is necessary to collect data from multiple measurement points to calculate the plate magnetic permeability. When there are multiple actual magnetic induction intensities and theoretical magnetic induction intensities, the optimal plate magnetic permeability result can be calculated by minimizing the total error between the actual and theoretical values.

[0056] Specifically, since the magnetic field distribution around a soft magnetic material plate in a static magnetic field is related to the magnetic permeability of the plate itself, according to the electromagnetic law, the calculation formula for the magnetic induction intensity is:

[0057]

[0058] Where B is the magnetic induction intensity at the test point, and H is the magnetic field intensity at the test point.

[0059] Establish a fitness function with the plate permeability as the unknown quantity:

[0060]

[0061] in is the actual magnetic induction intensity vector of the test point. Each actual magnetic induction intensity in the vector can be obtained by directly measuring the magnetic induction intensity of the measurement point, or by measuring the magnetic field intensity at the measurement point and then converting it into calculation. is the theoretical magnetic induction intensity vector of the test point. Each theoretical magnetic induction intensity in the vector is obtained by theoretical calculation of the magnetic field distribution around the soft magnetic material plate, which is an expression for the magnetic permeability of the plate.

[0062] The fitness function's criterion is to minimize its value, J. The fitness function's value is the norm of the difference vector obtained by subtracting the actual magnetic induction intensity vector from the theoretical magnetic induction intensity vector. A smaller norm indicates closer alignment between the two vectors. Subsequent optimization calculations aim to modify the permeability data in the theoretical model, aligning the theoretical calculation results with the actual measured results. Ultimately, the result with the smallest norm is obtained, thereby achieving the optimal plate permeability.

[0063] As a specific embodiment, optimizing and solving the plate magnetic permeability with the goal of minimizing the fitness function includes:

[0064] Generate an initial particle swarm with one particle corresponding to one magnetic permeability value, and calculate the fitness function value of the particle;

[0065] For the fitness function value of each particle in the k-th generation particle swarm, if it does not meet the convergence requirements, the iterative calculation will continue until the fitness function value of any particle in the particle swarm meets the convergence requirements, and the global optimal position of the particle is used as the plate magnetic permeability.

[0066] It should be noted that the present invention's solution to the fitness function minimization objective can be obtained through a particle swarm optimization algorithm. A convergence requirement (i.e., a convergence threshold) is pre-set for the fitness function. When the fitness function value is less than the convergence threshold, it is considered to have reached its minimum, thereby obtaining the plate permeability corresponding to the fitness function value. Using the convergence requirement as a criterion not only yields a more accurate plate permeability calculation result, but also reduces the number of iterative calculations and improves computational efficiency.

[0067] Specifically, the first step is to generate the initial particle swarm , each particle represents a possible plate magnetic permeability value, substitute the plate magnetic permeability value into the fitness function to obtain the fitness function value of each particle .

[0068] Step 2: When the fitness function value of the particle does not meet the requirements, the value of each particle is updated according to:

[0069]

[0070]

[0071] in is the position of the i-th particle in the k-th iteration, and each particle represents a possible value of the plate magnetic permeability; is the update speed of the i-th particle in the k-th iteration; is the individual best position of the i-th particle in the k-th iteration; is the global optimal position of the i-th particle in the k-th iteration; w is the inertia weight coefficient; c1 and c2 are learning factors; r1 and r2 are random numbers between (0,1).

[0072] The inertia weight coefficient w controls the particle's inertia. A larger inertia allows particles to search widely in space, avoiding being trapped in local optima; a smaller inertia allows particles to conduct rapid local searches and converge to the optimal solution more quickly. The learning factor c1 adjusts the influence of the individual optimal position on the particle update rate, while the learning factor c2 adjusts the influence of the global optimal position on the particle update rate. Random numbers r1 and r2 are randomly generated in each iteration to enhance the algorithm's global search capability and introduce randomness and diversity into the algorithm.

[0073] Step 3: Calculate the k+1 generation particle swarm The fitness function value of each particle in If the fitness function value does not meet the convergence criteria, the process returns to step 2 and performs the next iterative calculation. If the fitness function value meets the convergence criteria, the current global optimal position gbest is taken as the plate permeability. To determine whether the fitness function value meets the convergence criteria, as long as the fitness function value of any particle in a certain generation of the particle swarm meets the convergence criteria, the next iterative calculation is not required, and the plate permeability is obtained using the global optimal position corresponding to the particle that meets the convergence criteria.

[0074] As a specific embodiment, establishing a magnetic field distribution model around a soft magnetic material plate includes:

[0075] The total magnetic field intensity at any point P in the space around the soft magnetic material plate is expressed as the superposition of the magnetic field intensity at point P of the uniform magnetic field and the magnetic field intensity at point P after the soft magnetic material plate is magnetized.

[0076] It should be noted that the magnetic field intensity at any point P in space can be considered to be caused by two field sources, the direct field source Hs and the indirect field source Hm. In the present invention, the direct field source is the uniform magnetic field generated by the Helmholtz coil, and the indirect field source is the magnetic field generated by the magnetization of the soft magnetic material plate in the uniform magnetic field. Therefore, the magnetic field intensity at P is:

[0077]

[0078] in is the total magnetic field intensity at point P; is the magnetic field intensity generated by the direct field source at point P, that is, the magnetic field intensity of the uniform magnetic field itself; It is the magnetic field intensity generated by the indirect field source at point P, that is, the magnetic field intensity generated at point P after the soft magnetic material plate is magnetized.

[0079] Furthermore, the magnetic field intensity at point P after the soft magnetic material plate is magnetized includes: dividing the soft magnetic material plate into minute elements of area;

[0080] According to the Poisson equation of static magnetic field, the surface integral of the soft magnetic material plate is performed by multiplying the magnetization intensity of the soft magnetic material plate corresponding to the area element by the normal vector of the plate and then dividing the result by the distance from the soft magnetic material plate corresponding to the area element to point P.

[0081] The magnetization intensity is equal to the product of the difference between the plate permeability and one and the magnetic field intensity.

[0082] Specifically, according to the Poisson equation in the static magnetic field, it can be known that the influence of the indirect field source, that is, the soft magnetic material plate, on the magnetic field intensity at point P is determined by the magnetization intensity of the soft magnetic material plate itself, the area of ​​the soft magnetic material plate, and the distance between point P and the soft magnetic material plate. Assuming that the soft magnetic material plate is at position Q, the magnetic field intensity generated by the soft magnetic material plate at point P can be obtained as:

[0083]

[0084] in: is the magnetic field intensity generated by the soft magnetic material plate at point P, is the magnetization intensity inside the soft magnetic material plate, represents the distance between the soft magnetic material plate and point P, n represents the normal vector of the soft magnetic material plate, Represents the area of ​​the soft magnetic material plate, and performs surface integration on the soft magnetic material plate.

[0085] The soft magnetic material plate is discretely divided into several equivalent uniform magnetized bodies. In order to solve the magnetization intensity inside each unit after discretization, the field point P is usually placed at the center of each discrete unit. The equation group with the magnetic field intensity inside each discrete unit as the unknown quantity can be obtained, and according to the relationship between the magnetization intensity and the magnetic field intensity We can get:

[0086]

[0087] in represents the discrete number of soft magnetic material plate divisions, represents the center coordinate of the i-th unit after discretization, , Indicates the center coordinates of the jth unit after discretization. When i and j are the same, it corresponds to and is the same point in the soft magnetic material plate, so the magnetic field intensity and magnetization intensity in the soft magnetic material can be calculated according to the equation; is the flat permeability (the flat permeability in the present invention refers to the relative permeability), For soft magnetic material flat plate The magnetic field strength generated at the point, is the magnetic field intensity in the i-th discrete unit, is the normal vector of the ith discrete unit. From this, the magnetic field strength of each discrete unit inside the plate can be calculated, and the magnetic field distribution around the soft magnetic material plate can be further calculated.

[0088] In addition to a method for measuring the magnetic permeability of a plate, the present invention also provides Figure 2A system for measuring the magnetic permeability of a flat plate is shown, comprising: a pair of Helmholtz coils, wherein the two identical coil rings are arranged in parallel and coaxially;

[0089] A flat plate support frame 2 is provided between the pair of Helmholtz coils, and a flat plate plane of the flat plate support frame 2 is parallel to the axis of the pair of Helmholtz coils;

[0090] The measuring module 3 is arranged above the flat panel support frame 2 and between the pair of Helmholtz coils 1 to measure the magnetic field strength at a plurality of measuring points;

[0091] The processing module obtains the plate magnetic permeability of the soft magnetic material plate to be measured according to the measurement results collected by the measurement module 3.

[0092] It should be noted that the present invention can test the flat sample used for actual installation of the shielding body, and can directly obtain the magnetic permeability of the shielding layer structure without the need to make a separate standard test ring, which can truly reflect the magnetic properties of the soft magnetic material flat plate; the sensor is directly used to complete the test of the magnetic field strength, so the test sample itself does not need to be wrapped with wires, which reduces the influence of human factors during the test and improves the reliability of the test; when measuring multiple soft magnetic material flat plates, it is only necessary to move and replace the test flat plate on the flat plate support without moving other devices, making the test process very convenient and easy to operate. The measurement module in the present invention can measure the magnetic field strength, and can also choose to measure the magnetic induction strength. Based on the conversion relationship between the magnetic induction strength and the magnetic field strength at the same measuring point, the measurement results of the two can be converted to each other without affecting the final result.

[0093] It's worth noting that the spatial extent of the uniform magnetic field in the present invention can be determined by the Helmholtz coil pair that generates the magnetic field. When currents of the same direction and magnitude are passed through a pair of parallel, identical coil loops, a uniform magnetic field is generated between the Helmholtz coil pair. The technology for generating a uniform magnetic field using Helmholtz coil pairs is conventional and therefore not described in detail. The measurements in the present invention are all performed within the uniform magnetic field region.

[0094] like Figure 2 and Figure 3 As shown, the flat plate of the flat plate support frame 2 is located at the center between the pair of Helmholtz coils 1, and the distance from the center of the flat plate to the two coil rings is the same; a grid is drawn on the upper surface of the flat plate of the flat plate support frame 2 to position the soft magnetic material flat plate.

[0095] It should be noted that the uniform magnetic field is within the range of the coaxial central axis of the Helmholtz coil pair and a certain range extending around the central axis. Therefore, the flat plate of the flat plate support frame is set at the center position between the Helmholtz coil pair to ensure that the soft magnetic material flat plate placed on the flat plate can be within the uniform magnetic field range, and the sensor array above the square support frame can also be within the uniform magnetic field range, thereby ensuring the accuracy of the detection results.

[0096] It is worth noting that a grid is drawn on the upper surface of the plate of the plate support frame, and the specific size of the grid can be set according to actual conditions. Therefore, after the soft magnetic material plate is placed on the plate support frame, the soft magnetic material plate can be positioned according to the grid; after completing the measurement of one soft magnetic material plate, the replaced soft magnetic material plate can be placed in the same position for measurement, ensuring the stability of the measurement process and the consistency of variables, and improving the accuracy of the magnetic permeability of the plate.

[0097] Specifically, the measurement module 3 includes a test fixture 31 and a sensor array 32 fixed on the test fixture 31;

[0098] The test fixture 31 is located above the flat support frame 2 and is connected to the pair of Helmholtz coils 1;

[0099] The sensor array 32 is located above the center of the flat panel of the flat panel support frame 2 and detects the magnetic field strength at several measurement points.

[0100] It should be noted that the test fixture and the Helmholtz coil pair are only simply connected and fixed, which does not affect the generation of a uniform magnetic field after the current passes through the coil. At the same time, the test fixture can fix the sensor array, and fix the sensor array directly above the center of the flat plate of the flat plate support frame, which is conducive to determining the relative position relationship between the actual measurement point and the soft magnetic material flat plate, and is convenient for calculating the theoretical magnetic field intensity and theoretical magnetic induction intensity of the measurement point through the magnetic field distribution model around the soft magnetic material flat plate.

[0101] Furthermore, the soft magnetic material plate is placed on the upper surface of the plate of the plate support frame 2, and the center of the soft magnetic material plate is on the same vertical line as the center of the plate;

[0102] The sensors in the sensor array 32 are arranged at equal intervals, and all the sensors are on the same vertical line with the center of the plate.

[0103] Specifically, the center of the soft magnetic material plate and the center of the plate are on the same vertical line, which can ensure that the position of the soft magnetic material plate is at the center position between the Helmholtz coil pair, that is, within the uniform magnetic field range; all sensors are on the same vertical line with the center of the plate, which also means that all sensors are perpendicular to the center of the soft magnetic material plate. At this time, due to the symmetry of the sensor position with respect to the soft magnetic material plate, it is conducive to simplifying the calculation of the magnetic field strength generated by the soft magnetic material plate on the measurement point, thereby improving calculation efficiency.

[0104] In an embodiment of the present invention, a system for measuring the magnetic permeability of a flat plate is first constructed. Specifically, the system is assembled from a pair of Helmholtz coils, a flat plate support, and a measurement module. The measurement module is then connected to a processing module, which stores a model for calculating the magnetic permeability of the flat plate based on the measured data. A grid is drawn on the upper surface of the flat plate of the flat plate support for positioning the flat plate to be measured. The flat plate of the flat plate support can be 500 mm by 500 mm in size, and each grid on the flat plate can be 50 mm by 50 mm in size. Each grid is marked with a 10 mm interval on the edge, thereby ensuring accurate positioning of the soft magnetic material flat plate.

[0105] The test fixture, connected to the Helmholtz coil pair, is located above the midpoint of the flat surface of the flat plate support. The lowest point of the test fixture is 20 mm from the flat surface. The sensor array, consisting of three sensors, is fixed to the test fixture, spaced 30 mm apart perpendicular to the flat surface, with the lowest sensor 20 mm from the lowest point of the test fixture. The magnetic field strength is measured at 50 mm, 80 mm, and 110 mm above the flat plate midpoint. When the Helmholtz coil operates, the magnetic field within the coil changes, allowing the sensors to directly measure the magnetic field within the coil.

[0106] The specific test steps include: Step 1, input current into the Helmholtz coil pair to generate a uniform magnetic field within a certain spatial range. Step 2, perform data acquisition, obtain data from three test points in the uniform magnetic field through the sensor, and transmit the acquired data to the processing module to obtain the magnetic field strength under the uniform magnetic field. Step 3, place the soft magnetic material flat plate to be tested on the support plane so that the soft magnetic material flat plate is located at the center position of the Helmholtz coil pair. Step 4, perform data acquisition again, obtain data of the actual magnetic field strength through the three test points at the same position of the sensor, and transmit the acquired data to the processing module to obtain the actual magnetic field strength. Step 5, complete the test, and use the measured data to calculate the flat plate magnetic permeability through the data processing method saved by the processing module to obtain the flat plate magnetic permeability of the soft magnetic material flat plate to be tested. After taking out the soft magnetic material flat plate after the test, replace it with a new soft magnetic material flat plate to continue testing.

[0107] The above embodiments are further elaborations and illustrations of the present invention for ease of understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the magnetic permeability of a flat plate, characterized in that: include: Place a flat plate of soft magnetic material within the spatial range of a uniform magnetic field; For a plurality of measurement points within the spatial range, the magnetic field strength is measured before and after the soft magnetic material plate is placed; Establishing a magnetic field distribution model around the soft magnetic material plate and obtaining theoretical magnetic field strengths at several measuring points; Calculate the theoretical and actual magnetic induction intensities at the measurement point after placing the soft magnetic material plate, and establish a fitness function with the plate magnetic permeability as the unknown quantity; The fitness function is the norm of the difference vector obtained by subtracting the actual magnetic induction intensity vector from the theoretical magnetic induction intensity vector; The actual magnetic induction intensity vector and the theoretical magnetic induction intensity vector are respectively vectors obtained by arranging the actual magnetic induction intensity and the theoretical magnetic induction intensity in the same order of measurement points; The magnetic permeability of the plate is obtained by optimizing the solution with the goal of minimizing the fitness function.

2. The method for measuring the magnetic permeability of a plate according to claim 1, wherein: The establishment of a magnetic field distribution model around the soft magnetic material plate includes: The total magnetic field intensity at any point P in the space around the soft magnetic material plate is expressed as the superposition of the magnetic field intensity at point P of the uniform magnetic field and the magnetic field intensity at point P after the soft magnetic material plate is magnetized.

3. The method for measuring the magnetic permeability of a plate according to claim 2, wherein: The magnetic field intensity at point P after the soft magnetic material plate is magnetized includes: dividing the soft magnetic material plate into micro-element areas; According to the Poisson equation of static magnetic field, the surface integral of the soft magnetic material plate is performed by multiplying the magnetization intensity of the soft magnetic material plate corresponding to the area element by the normal vector of the plate and then dividing the result by the distance from the soft magnetic material plate corresponding to the area element to point P. The magnetization intensity is equal to the product of the difference between the plate magnetic permeability and one and the magnetic field intensity.

4. A method for measuring the magnetic permeability of a plate according to claim 1 or 3, characterized in that: The spatial range of the uniform magnetic field is determined by the Helmholtz coil pair that generates the magnetic field; When current of the same direction and magnitude is passed through each coil ring in the Helmholtz coil pair, a uniform excitation magnetic field is generated in the Helmholtz coil pair.

5. A method for measuring the magnetic permeability of a flat plate according to claim 1 or 3, characterized in that: The solution to obtain the plate magnetic permeability includes: Generate an initial particle swarm with one particle corresponding to one magnetic permeability value, and calculate the fitness function value of the particle; For the fitness function value of each particle in the k-th generation particle swarm, if it does not meet the convergence requirements, the iterative calculation will continue until the fitness function value of any particle in the particle swarm meets the convergence requirements, and the global optimal position of the particle is used as the plate magnetic permeability.

6. A system for measuring the magnetic permeability of a plate, suitable for the method according to any one of claims 1 to 5, characterized in that: include: Helmholtz coil pair, two identical coil rings arranged parallel and coaxially; A flat plate support frame is provided between the pair of Helmholtz coils, wherein the flat plate plane of the flat plate support frame is parallel to the axis of the pair of Helmholtz coils; A measurement module is arranged above the flat panel support frame and between the Helmholtz coil pairs to measure the magnetic field strength at a number of measurement points; The processing module obtains the plate magnetic permeability of the soft magnetic material plate to be measured according to the measurement results collected by the measurement module.

7. A system for measuring the magnetic permeability of a flat plate according to claim 6, characterized in that: The flat plate of the flat plate support is located at the center between the Helmholtz coil pair, and the distance from the center of the flat plate to the two coil rings is the same; A grid is drawn on the upper surface of the flat plate of the flat plate support frame to position the soft magnetic material flat plate.

8. A system for measuring the magnetic permeability of a flat plate according to claim 6 or 7, characterized in that: The measurement module includes a test fixture and a sensor array fixed on the test fixture; The test fixture is located above the flat support frame and is connected to the Helmholtz coil pair; The sensor array is located above the center of the flat panel of the flat panel support frame and detects the magnetic field strength at several measurement points.

9. The system for measuring the magnetic permeability of a flat plate according to claim 8, characterized in that: The soft magnetic material plate is placed on the upper surface of the plate of the plate support frame, and the center of the soft magnetic material plate is on the same vertical line as the center of the plate.

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