Method and system for measuring magnetic conductivity of flat plate

Abstract

The invention discloses a method and a system for measuring the magnetic conductivity of a flat plate. The method comprises the following steps: placing a soft magnetic material flat plate in a spatial range of a uniform magnetic field; for a plurality of measurement points in the spatial range, respectively measuring magnetic field intensities of the soft magnetic material flat plate before and after the flat plate is placed; establishing a magnetic field distribution model around the soft magnetic material flat plate, and obtaining theoretical magnetic field intensities of the plurality of measurement points; calculating the theoretical magnetic induction intensity and the actual magnetic induction intensity of the measuring point after the soft magnetic material flat plate is placed, and establishing a fitness function taking the magnetic conductivity of the flat plate as an unknown quantity; and carrying out optimization solution by taking the minimum fitness function as a target to obtain the magnetic conductivity of the flat plate. According to the invention, a flat plate sample piece for actual installation of a shielding body is tested, the magnetic conductivity of a shielding layer structure can be directly obtained, and the magnetic characteristics of a soft magnetic material flat plate can be truly reflected; the process of measuring and obtaining the magnetic conductivity is simple and rapid, data reading and detection can be completed after a to-be-tested flat plate is placed, and the testing efficiency is high.

Description

Technical Field

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

[0002] Magnetic permeability is a physical quantity that describes the degree of magnetization of a material in a magnetic field. Understanding the magnetic permeability of a material can evaluate its magnetic properties in practical applications, which is very important for determining whether the material meets the requirements and application standards. Materials with high magnetic permeability can conduct magnetic fields more effectively, reducing magnetic field attenuation and loss, so they have significant advantages in applications that require efficient magnetic conduction. In magnetic shielding applications, materials with high magnetic permeability can more effectively shield external magnetic fields and protect internal sensitive devices from magnetic interference. By measuring the magnetic permeability of a flat plate of soft magnetic material, the magnetic conduction ability of the material in a magnetic field can be obtained, so as to understand its behavior in the actual working environment. Therefore, how to accurately and quickly measure the magnetic permeability of a flat plate of soft magnetic material is of great significance. Currently, the commonly used method for detecting the magnetic properties of soft magnetic materials is the test ring detection method specified in the national standard GB / T 13012-2008 "Measurement Method for DC Magnetic Properties of Soft Magnetic Materials". However, this method requires processing the soft magnetic material into a ring shape, which cannot truly reflect the magnetic properties of the flat plate of soft magnetic material. At the same time, the test process is complex, and the test efficiency is low, and it is easy to affect the accuracy of the test results due to human error.

[0003] In the "Method for Measuring the Magnetic Permeability of a Cylindrical Soft Magnetic Material" disclosed in the Chinese patent literature, with the publication number CN102565728B and the publication date of September 25, 2013, the specific method for measuring magnetic permeability is as follows: 1. Measure the aspect ratio of the cylindrical soft magnetic material; 2. Place the cylindrical soft magnetic material with a secondary coil wound around its outer wall inside an excitation solenoid with an excitation coil wound around it. The central axis of the cylindrical soft magnetic material, the central axis of the secondary coil, and the central axis of the excitation solenoid coincide with each other, and the center of the cylindrical soft magnetic material, the central axis of the secondary 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 circuit. An alternating voltage is applied to the circuit through a lock-in amplifier, and the induced voltage of the secondary coil and the voltage across the precision resistor are received; 4. Obtain the external magnetic permeability of the cylindrical soft magnetic material; 5. Obtain the external magnetic susceptibility of the cylindrical soft magnetic material; 6. Obtain the magnetic permeability of the cylindrical soft magnetic material; The error range of the magnetic permeability obtained by this technology is 10%, which is far better than the error range of the magnetic permeability of the cylindrical soft magnetic material obtained by the existing measurement methods. However, this technology measures the magnetic permeability of a cylindrical soft magnetic material and cannot accurately reflect the magnetic properties of a flat plate of soft magnetic material. Moreover, it also requires winding coils for testing, the test process is complex, and the test efficiency is low, and it is easy to affect the accuracy of the test results due to human error. Summary of the Invention

[0004] The present invention aims to overcome the problems in the prior art that the operation of measuring the magnetic permeability of soft magnetic materials is complex, the test efficiency is low, the accuracy of the test results is easily affected by human errors, and the magnetic characteristics of the soft magnetic material plate cannot be truly reflected, and provides a method and system for measuring the magnetic permeability of a plate.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for measuring the magnetic permeability of a plate, comprising: Placing a soft magnetic material plate within the spatial range of a uniform magnetic field; For a plurality of measurement points within the said spatial range, measuring the magnetic field intensity before and after placing the soft magnetic material plate respectively; Establishing a magnetic field distribution model around the soft magnetic material plate to obtain the theoretical magnetic field intensity of a plurality of said measurement points; Calculating the theoretical magnetic induction intensity and the actual magnetic induction intensity of the measurement points after placing the soft magnetic material plate, and establishing a fitness function with the magnetic permeability of the plate as the unknown; Optimally solving with the goal of minimizing the fitness function to obtain the magnetic permeability of the plate.

[0006] In the present invention, a magnetic field distribution module around the soft magnetic material plate after it is placed in a uniform magnetic field is established through theoretical calculation in advance, so as to obtain the theoretical magnetic field intensity situation after placing the soft magnetic material plate, and obtain the theoretical magnetic field intensity of a plurality of measurement points. The theoretical magnetic field intensity is an expression related to the magnetic permeability of the plate. Then, the actual magnetic field intensity of the same measurement points is directly detected by a sensor, and based on the relationship between the magnetic induction intensity and the 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 magnetic permeability of the plate. In an actual situation, a fitness function regarding 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 plate is obtained when the fitness function is minimized. The process of measuring and obtaining the magnetic permeability of the plate in the present invention is simple and fast. After placing the plate to be measured, the data can be read and detected, making the test process very rapid and the test efficiency high.

[0007] Preferably, the fitness function is the norm of the difference vector obtained by subtracting the theoretical magnetic induction intensity vector from the actual magnetic induction intensity vector; The actual magnetic induction intensity vector and the theoretical magnetic induction intensity vector are vectors obtained by arranging the actual magnetic induction intensity and the theoretical magnetic induction intensity in the same order of measurement points.

[0008] Preferably, establishing the 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 flat soft magnetic material plate is expressed as the superposition of the magnetic field intensity at point P in the uniform magnetic field and the magnetic field intensity at point P after the flat soft magnetic material plate is magnetized.

[0009] Preferably, the magnetic field intensity at point P after the flat soft magnetic material plate is magnetized includes: dividing the flat soft magnetic material plate into area micro-elements; According to the Poisson equation of the static magnetic field, perform an area integral on the flat soft magnetic material plate by dividing the result of the dot product of the magnetization intensity of the flat soft magnetic material plate corresponding to the area micro-element and the normal vector of the plate by the distance from the flat soft magnetic material plate corresponding to the area micro-element to point P. The magnetization intensity is equal to the product of the difference between the plate permeability and one and the magnetic field intensity.

[0010] Preferably, the spatial range of the uniform magnetic field is determined by the Helmholtz coils that generate the magnetic field; After passing the same current in direction and magnitude through each coil loop in the pair of Helmholtz coils, a uniform excitation magnetic field is generated in the pair of Helmholtz coils.

[0011] Preferably, the obtained plate permeability includes: Generate an initial particle swarm with one particle corresponding to one permeability value, and calculate the fitness function value of the particles; For the fitness function value of each particle in the k-th generation particle swarm, if the convergence requirement is not met, continue the iterative calculation until the fitness function value of any one particle in the particle swarm meets the convergence requirement, and use the global best position of this particle as the plate permeability.

[0012] A system for measuring the plate permeability includes: a pair of Helmholtz coils, with two identical coil loops arranged in parallel and coaxial; A flat plate support frame, arranged between the pair of Helmholtz coils, and the flat plate plane of the flat plate support frame is parallel to the axis of the pair of Helmholtz coils; A measurement module, arranged above the flat plate support frame and between the pair of Helmholtz coils, to measure the magnetic field intensity at a number of measurement points; A processing module, to obtain the plate permeability of the soft magnetic material plate to be measured according to the measurement results collected by the measurement module.

[0013] In the present invention, it is possible to test the flat sample for actual installation of the shielding body, directly obtain the magnetic permeability of the shielding layer structure, without separately manufacturing a standard test ring, and can truly reflect the magnetic properties of the flat soft magnetic material; the magnetic field strength is directly measured by a sensor, so the test sample itself does not need to be wound with wires, reducing the influence of human factors during the test and improving the reliability of the test; when measuring multiple flat soft magnetic materials, only the test flat on the flat support frame needs to be moved and replaced, without moving other devices and equipment, making the test process very convenient and easy to operate.

[0014] Preferably, the flat on the flat support frame is located at the central position between the Helmholtz coil pairs, and the distance from the center of the flat to the two coil rings is the same; The upper surface of the flat on the flat support frame is drawn with a grid for positioning the flat soft magnetic material.

[0015] Preferably, 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 pairs; The sensor array is located above the center of the flat on the flat support frame to detect the magnetic field strength at several measurement points.

[0016] Preferably, the flat soft magnetic material is placed on the upper surface of the flat on the flat support frame, and the center of the flat soft magnetic material is on the same vertical line as the center of the flat; Several sensors in the sensor array are equally spaced, and all sensors are on the same vertical line as the center of the flat.

[0017] The present invention has the following beneficial effects: By testing the flat sample for actual installation of the shielding body, the magnetic permeability of the shielding layer structure can be directly obtained without separately manufacturing a standard test ring, and can truly reflect the magnetic properties of the flat soft magnetic material; the test is completed using a magnetic induction intensity sensor, so the test sample itself does not need to be wound with wires, reducing the influence of human factors during the test and improving the reliability of the test; when measuring multiple flats, only the test flat on the flat support frame needs to be moved and replaced, without moving other devices and equipment, 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 can be read and detected after placing the flat to be tested, making the test process very rapid and the test efficiency high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flowchart of the method for measuring the magnetic permeability of a flat in the present invention.

[0019] Figure 2 is a schematic diagram of the system for measuring the magnetic permeability of a flat in the present invention.

[0020] Figure 3 It is a schematic diagram of the upper surface of the flat plate of the flat plate support frame in the present invention.

[0021] In the figure: 1. Helmholtz coil; 2. Flat plate support frame; 3. Measuring module; 31. Test fixture; 32. Sensor array. Specific embodiments

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] Currently, the commonly used method for detecting the magnetic properties of soft magnetic materials is the test ring detection method specified in the national standard GB / T 13012-2008 "Measurement Method for DC Magnetic Properties of Soft Magnetic Materials". This method uses a special standard test ring, and by winding a primary coil and a secondary coil on the test ring, they are used to apply a magnetic field and measure the magnetic induction intensity respectively. The primary coil passes an electric current to generate a magnetic field, and the secondary coil then senses the magnetic induction intensity inside the test ring. By measuring the primary coil current and the induced electromotive force, the magnetic field strength H and the magnetic induction intensity B can be calculated, thereby obtaining the complete magnetic hysteresis loop of the material, and then calculating the magnetic permeability of the material. This test method has the following defects: 1) The sample production is complex, and stress and defects may be introduced during the process of processing the material into a ring shape, resulting in the test ring being unable to truly reflect the magnetic properties of the material flat plate used; 2) The test ring needs to be wound with coils for testing, resulting in low test efficiency, and during the process of winding the coils, due to uneven winding or applying stress to the test ring and other situations, it is easy to introduce human errors and affect the test results.

[0024] To solve the above problems, the present invention provides a method for measuring the magnetic permeability of a flat plate as shown in Figure 1 and includes: Placing a soft magnetic material flat plate within the spatial range of a uniform magnetic field; For a number of measurement points within the spatial range, measuring the magnetic field strength before and after placing the soft magnetic material flat plate respectively; Establishing a magnetic field distribution model around the soft magnetic material flat plate to obtain the theoretical magnetic field strength of a number of measurement points; Calculating the theoretical magnetic induction intensity and the actual magnetic induction intensity of the measurement points after placing the soft magnetic material flat plate, and establishing a fitness function with the magnetic permeability of the flat plate as the unknown quantity; Optimally solving with the goal of minimizing the fitness function to obtain the magnetic permeability of the flat plate.

[0025] It should be noted that in the present invention, a magnetic field distribution module around a flat soft magnetic material after being placed in a uniform magnetic field is established through theoretical calculations in advance, so that the theoretical magnetic field intensity situation after placing the flat soft magnetic material can be obtained, and the theoretical magnetic field intensities at several measurement points are obtained. The theoretical magnetic field intensity is an expression related to the magnetic permeability of the flat plate. Then, the actual magnetic field intensity at the same measurement points 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 situation, the two should be equal to obtain the magnetic permeability of the flat plate. In an actual situation, a fitness function regarding 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 in the present invention is simple and fast. After placing the flat plate to be measured, the data can be read and detected, making the test process very rapid and the test efficiency high.

[0026] It is worth noting that there are also methods for directly measuring the magnetic properties of a flat plate in the prior art. However, most of these methods need to combine the flat plate to be measured with a magnetic yoke to form a closed loop, and then use an induction coil and a probe to measure the magnetic field intensity H and the magnetic induction intensity B, directly obtain the hysteresis loop of the flat plate, and thus obtain the magnetic properties of the flat plate. Although this method can directly measure the magnetic properties of the flat plate, the device is relatively complex and the test efficiency still needs to be improved.

[0027] Furthermore, in the present invention, by measuring the magnetic field intensity before and after placing the flat soft magnetic material and combining the theoretical magnetic field intensities at several measurement points obtained from the magnetic field distribution model around the flat soft magnetic material, 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, based on directly measuring the magnetic induction intensity before and after placing the flat soft magnetic material, the theoretical magnetic induction intensity can be obtained by combining the magnetic induction intensity before placement with the theoretical magnetic field intensities at several measurement points obtained from the magnetic field distribution model around the flat soft magnetic material, and the magnetic induction intensity after placement is the actual magnetic induction intensity. The specific conversion relationship belongs to existing common knowledge, so no detailed description is given.

[0028] 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; The actual magnetic induction intensity vector and the theoretical magnetic induction intensity vector are vectors obtained by arranging the actual magnetic induction intensity and the theoretical magnetic induction intensity in the same order of measurement points.

[0029] It should be noted that the actual magnetic induction intensity is the actually detected magnetic induction intensity, and the theoretical magnetic induction intensity is the theoretically calculated magnetic induction intensity through the model, which is an expression about the magnetic permeability of the flat plate. When there is only one measurement point, the magnetic permeability of the flat plate can be calculated by making the actual magnetic induction intensity equal to the theoretical magnetic induction intensity. However, a single measurement point is prone to measurement errors and other problems, resulting in inaccurate results. Therefore, it is necessary to collect data at multiple measurement points for the calculation of the magnetic permeability of the flat plate. In the case of multiple actual magnetic induction intensities and theoretical magnetic induction intensities, the optimal magnetic permeability result of the flat plate can be calculated with the minimum total error between the actual and the theoretical values.

[0030] Specifically, since the magnetic field distribution around the soft magnetic material flat plate in a static magnetic field is related to the magnetic permeability of the flat plate itself, according to the electromagnetic law, the calculation formula for the magnetic induction intensity is:

[0031] where B is the magnetic induction intensity at the test point, and H is the magnetic field intensity at the test point.

[0032] Establish a fitness function with the magnetic permeability of the flat plate as the unknown:

[0033] where is the vector of the actual magnetic induction intensity at the test point. Each actual magnetic induction intensity in the vector can be obtained by directly measuring the magnetic induction intensity at the measurement point, or can be obtained through conversion calculation after measuring the magnetic field intensity at the measurement point; is the vector of the theoretical magnetic induction intensity at the test point. Each theoretical magnetic induction intensity in the vector is obtained through theoretical calculation based on the magnetic field distribution around the soft magnetic material flat plate, and it is an expression about the magnetic permeability of the flat plate.

[0034] The judgment criterion of the fitness function is that the value of the fitness function J is as small as possible. The value of the fitness function is the norm of the difference vector obtained by subtracting the vector of the actual magnetic induction intensity from the vector of the theoretical magnetic induction intensity. The smaller the norm, the closer the two vectors are. The subsequent optimization calculation is to modify the magnetic permeability data in the theoretical model to make the theoretical calculation result as close as possible to the actual measurement result, and finally obtain a result with the smallest norm, so as to obtain the optimal magnetic permeability of the flat plate.

[0035] As a specific embodiment, optimizing and solving to obtain the magnetic permeability of the flat plate with the minimum fitness function includes: Generating an initial particle swarm with one particle corresponding to one magnetic permeability value, and calculating the fitness function value of the particle; For the fitness function value of each particle in the k-th generation particle swarm, if the convergence requirement is not met, continue the iterative calculation until the fitness function value of any particle in the particle swarm meets the convergence requirement, and use the global best position of this particle as the slab permeability.

[0036] It should be noted that the solution of the minimization objective of the fitness function in the present invention can be obtained by optimizing through the particle swarm optimization algorithm. The convergence requirement (i.e., the convergence threshold) of the fitness function is preset, and it is considered that the minimum value has been reached when the fitness function value is less than the convergence threshold, so as to obtain the slab permeability corresponding to the fitness function value. Using the convergence requirement as the judgment criterion can not only obtain a more accurate calculation result of the slab permeability, but also reduce the amount of iterative calculation and improve the calculation efficiency.

[0037] Specifically, the first step is to generate an initial particle swarm , each particle represents a possible value of the slab permeability. Substitute the value of the slab permeability into the fitness function to obtain the fitness function value of each particle .

[0038] The second step is to update the value of each particle according to the following formula when the fitness function value of the particle does not meet the requirements:

[0039]

[0040] where is the position of the i-th particle in the k-th generation iteration, and each particle represents a possible value of the slab permeability; is the updated velocity of the i-th particle in the k-th generation iteration; is the individual best position of the i-th particle in the k-th generation iteration; is the global best position of the i-th particle in the k-th generation iteration; w is the inertia weight coefficient; c1 and c2 are learning factors; r1 and r2 are random numbers between (0, 1).

[0041] The inertia weight coefficient w controls the motion inertia of the particle. A larger motion inertia can enable the particle to search over a large span in space and avoid falling into a local optimal solution; a smaller motion inertia can enable the particle to perform a fast local search and converge to the optimal value more quickly. The learning factor c1 is used to adjust the influence degree of the individual best position on the update of the particle's update velocity, and the learning factor c2 is used to adjust the influence degree of the global best position on the update of the particle's update velocity. The random numbers r1 and r2 are randomly generated in each iteration to increase the global search ability of the algorithm and introduce randomness and diversity into the algorithm.

[0042] The third step is to calculate the (k + 1)-th generation particle swarm The fitness function value of each particle in , if the fitness function value does not meet the convergence condition, return to the second step for the next iterative calculation; if the fitness function value meets the convergence condition, take the current global best position gbest as the magnetic permeability of the flat plate. For the judgment of whether the fitness function value meets the convergence condition, as long as the fitness function value of any one particle in a certain generation of particle swarm meets the convergence condition, there is no need to perform the next iterative calculation, and the global best position corresponding to the particle that meets the convergence condition is used to obtain the magnetic permeability of the flat plate.

[0043] As a specific embodiment, establishing a magnetic field distribution model around a soft magnetic material flat plate includes: The total magnetic field intensity at any point P in the space around the soft magnetic material flat plate is expressed as the superposition of the magnetic field intensity at point P in the uniform magnetic field and the magnetic field intensity at point P after the soft magnetic material flat plate is magnetized.

[0044] 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 after the soft magnetic material flat plate in the uniform magnetic field is magnetized. Therefore, the magnetic field intensity at P is:

[0045] Among them 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; is the magnetic field intensity generated by the indirect field source at point P, that is, the magnetic field intensity generated by the soft magnetic material flat plate after magnetization at point P.

[0046] Furthermore, the magnetic field intensity at point P after the soft magnetic material flat plate is magnetized includes: dividing the soft magnetic material flat plate into area micro-elements; According to the Poisson equation of the static magnetic field, perform an area integral on the soft magnetic material flat plate by dividing the result of the dot product of the magnetization intensity of the soft magnetic material flat plate corresponding to the area micro-element and the normal vector of the flat plate by the distance from the soft magnetic material flat plate corresponding to the area micro-element to point P; The magnetization intensity is equal to the product of the difference between the magnetic permeability of the flat plate and one and the magnetic field intensity.

[0047] 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 flat plate, on the magnetic field intensity at point P is determined by the magnetization intensity of the soft magnetic material flat plate itself, the area size of the soft magnetic material flat plate, and the distance between point P and the soft magnetic material flat plate. Assuming that the soft magnetic material flat plate is at position Q, the magnetic field intensity generated by the soft magnetic material flat plate at point P can be obtained as:

[0048] Wherein: is the magnetic field strength generated by the soft magnetic material flat plate at point P, is the magnetization intensity inside the soft magnetic material flat plate, represents the distance between the soft magnetic material flat plate and point P, n represents the normal vector of the soft magnetic material flat plate, represents the area of the soft magnetic material flat plate, and performs a surface integral on the soft magnetic material flat plate.

[0049] The soft magnetic material flat plate is discretely divided into several equivalent uniformly magnetized bodies. To solve the magnetization intensity inside each discrete unit after discretization, usually the field point P is placed at the center of each discrete unit, and a system of equations with the magnetic field intensity inside each discrete unit as the unknown can be obtained. And according to the relationship between the magnetization intensity and the magnetic field intensity It can be obtained that:

[0050] Wherein represents the number of discrete divisions of the soft magnetic material flat plate, represents the central coordinates of the i-th unit after discretization, , represents the central coordinates corresponding to the j-th unit after discretization. When i and j are the same, it corresponds to and being the same point inside the soft magnetic material flat plate, so as to calculate the magnetic field intensity and magnetization intensity inside the soft magnetic material according to the equation; is the flat plate permeability (the flat plate permeability in the present invention refers to the relative permeability), is the magnetic field strength generated by the soft magnetic material flat plate at point, is the magnetic field strength inside the i-th discrete unit, is the normal vector of the i-th discrete unit. Thus, the magnetic field strength of each discrete unit inside the flat plate can be calculated, and further the magnetic field distribution around the soft magnetic material flat plate can be calculated.

[0051] In addition to a method for measuring the flat plate permeability, the present invention also provides a system for measuring the flat plate permeability as shown in Figure 2 which includes: a pair of Helmholtz coils 1, and two completely identical coil rings are arranged in parallel and coaxial; a flat plate support frame 2, which is arranged between the pair of Helmholtz coils 1, and the flat plate plane of the flat plate support frame 2 is parallel to the axis of the pair of Helmholtz coils 1; a measurement module 3, which is arranged above the flat plate support frame 2 and between the pair of Helmholtz coils 1, and measures the magnetic field strength at a plurality of measurement points; The processing module obtains the magnetic permeability of the flat soft magnetic material to be measured according to the measurement results collected by the measurement module 3.

[0052] It should be noted that in the present invention, the flat sample for actual installation of the shielding body can be tested, and the magnetic permeability of the shielding layer structure can be directly obtained without separately manufacturing a standard test ring, which can truly reflect the magnetic characteristics of the flat soft magnetic material. The magnetic field strength test is directly completed by using the sensor, so there is no need to wind wires on the test sample itself, reducing the influence of human factors in the test process and improving the reliability of the test. When measuring multiple flat soft magnetic materials, only the test flat on the flat support frame needs to be moved and replaced, without moving other devices and equipment, making the test process very convenient and easy to operate. The measurement module in the present invention can measure the magnetic field strength or can also choose to measure the magnetic induction intensity. Based on the conversion relationship between the magnetic induction intensity and the magnetic field strength at the same measurement point, the two measurement results can be converted into each other without affecting the final result.

[0053] It is worth noting that the spatial range of the uniform magnetic field in the present invention can be determined by the pair of Helmholtz coils generating the magnetic field. After passing the same-direction and same-magnitude currents through a pair of parallel and identical coil rings, a uniform magnetic field can be generated between the pair of Helmholtz coils. The technology of generating a uniform magnetic field based on the pair of Helmholtz coils belongs to the existing conventional technical means, so no detailed description will be given, and the measurement process in the present invention is carried out within the uniform magnetic field region.

[0054] As Figure 2 and Figure 3 shown, the flat of the flat support frame 2 is located at the central position between the pair of Helmholtz coils 1, and the distance from the center of the flat to the two coil rings is the same. A grid is drawn on the upper surface of the flat of the flat support frame 2 to position the flat soft magnetic material.

[0055] It should be noted that within the coaxial central axis position of the pair of Helmholtz coils and within a certain range extending around the central axis is the range of the uniform magnetic field. Therefore, the flat of the flat support frame is set at the central position between the pair of Helmholtz coils to ensure that the flat soft magnetic material placed on the flat can be within the uniform magnetic field range, and it can also make the sensor array above the flat support frame be within the uniform magnetic field range, ensuring the accuracy of the detection result.

[0056] It is worth noting that a grid is drawn on the upper surface of the flat of the flat support frame, and the specific size of the grid can be set according to the actual situation. Therefore, after placing the flat soft magnetic material on the flat support frame, the flat soft magnetic material can be positioned according to the grid. After completing the measurement of one flat soft magnetic material, another flat soft magnetic material to be replaced can be placed at 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 flat.

[0057] Specifically, the measurement module 3 includes a test fixture 31 and a sensor array 32 fixed on the test fixture 31; The test fixture 31 is located above the flat support frame 2 and is connected to the Helmholtz coil pair 1; The sensor array 32 is located above the center of the flat plate of the flat support frame 2 and detects the magnetic field strength at several measurement points.

[0058] It should be noted that the relationship between the test fixture and the Helmholtz coil pair is only a simple connection and fixation relationship, which does not affect the generation of a uniform magnetic field after the coil passes through an electric current. At the same time, the test fixture can fix the sensor array, and fixing the sensor array directly above the center of the flat plate of the flat support frame is beneficial to determining the relative position relationship between the actual measurement points and the soft magnetic material flat plate, facilitating the calculation of the theoretical magnetic field strength and theoretical magnetic induction intensity of the measurement points through the magnetic field distribution model around the soft magnetic material flat plate.

[0059] Furthermore, the soft magnetic material flat plate is placed on the upper surface of the flat plate of the flat support frame 2, and the center of the soft magnetic material flat plate and the center of the flat plate are on the same vertical line; Several sensors in the sensor array 32 are arranged at equal intervals, and all sensors are on the same vertical line as the center of the flat plate.

[0060] Specifically, the fact that the center of the soft magnetic material flat plate and the center of the flat plate are on the same vertical line can ensure that the position of the soft magnetic material flat plate is at the center position between the Helmholtz coil pair, that is, within the range of the uniform magnetic field; all sensors being on the same vertical line as the center of the flat plate also means that all sensors and the center of the soft magnetic material flat plate are collinear. At this time, due to the symmetry relationship of the sensor positions with respect to the soft magnetic material flat plate, it is beneficial to simplify the calculation of the magnetic field strength generated by the soft magnetic material flat plate at the measurement points and improve the calculation efficiency.

[0061] In the embodiment of the present invention, first, a system for measuring the magnetic permeability of a flat plate is built, that is, it is built and combined by a Helmholtz coil pair, a flat support frame, and a measurement module, and the measurement module is connected to the processing module. In the processing module, there is a specific method model for calculating the magnetic permeability of the flat plate based on the measurement data. A grid is drawn on the upper surface of the flat plate of the flat support frame for positioning the flat plate to be measured. The size of the flat plate of the flat support frame can be 500mm * 500mm, the size of each grid on the flat plate can be 50mm * 50mm, and markings at intervals of 10mm are marked on the edges of each grid, thereby ensuring the determination of the position of the soft magnetic material flat plate.

[0062] The test fixture is connected to the Helmholtz coil pair and is located above the midpoint of the flat plate plane of the flat plate support frame. The lowest point of the test fixture is 20 mm away from the flat plate plane. The sensor array consists of three sensors and is fixedly connected to the test fixture. The three sensors are each spaced 30 mm apart in the direction perpendicular to the flat plate plane, and the lowest sensor is 20 mm away from the lowest point of the test fixture. That is, the magnetic field intensities at 50 mm, 80 mm, and 110 mm above the midpoint of the flat plate are measured. When the Helmholtz coil is operating, the magnetic field inside the coil changes, and thus the sensor is directly used to measure the magnetic field inside the coil.

[0063] 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 within the uniform magnetic field through the sensor, and transmit the acquired data to the processing module to obtain the magnetic field intensity under the uniform magnetic field. Step 3, place the flat plate of the soft magnetic material to be tested on the support plane so that the flat plate of the soft magnetic material is located at the center position of the Helmholtz coil pair. Step 4, perform data acquisition again, obtain the data of the actual magnetic field intensity from the three test points at the same position through the sensor, and transmit the acquired data to the processing module to obtain the actual magnetic field intensity. Step 5, complete the test, and calculate the magnetic permeability of the flat plate using the data processing method saved by the processing module with the measured data to obtain the magnetic permeability of the flat plate of the soft magnetic material to be tested. After taking out the tested flat plate of the soft magnetic material, replace it with a new flat plate of the soft magnetic material and continue the test.

[0064] The above embodiments are further elaborations and explanations of the present invention for easy understanding, and are not any limitations to the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope 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 measuring 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 magnetic induction intensity and actual magnetic induction intensity of the measuring point after placing the soft magnetic material plate, and establish a fitness function with the plate magnetic permeability as the unknown quantity; The magnetic permeability of the plate is obtained by optimizing the solution with the goal of minimizing the fitness function.

2. A method for measuring the magnetic permeability of a plate according to claim 1, characterized in that: 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 measurement point order.

3. A method for measuring the magnetic permeability of a plate according to claim 1 or 2, characterized in that: The establishment of a magnetic field distribution model around the soft magnetic material plate comprises: 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.

4. A method for measuring the magnetic permeability of a plate according to claim 3, characterized in that: 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 area integral of the soft magnetic material plate is performed by dividing the result of dot multiplication of the magnetization intensity of the soft magnetic material plate corresponding to the area element and the normal vector of the plate 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 magnetic permeability of the plate and one and the magnetic field intensity.

5. A method for measuring the magnetic permeability of a plate according to claim 1, 2 or 4, 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.

6. A method for measuring the magnetic permeability of a plate according to claim 1, 2 or 4, characterized in that: The solution to obtain the plate magnetic permeability includes: Generate an initial particle group 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 kth 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.

7. A system for measuring the magnetic permeability of a plate, suitable for the method according to any one of claims 1 to 6, characterized in that: include: Helmholtz coil pair, two identical coil rings arranged in parallel and coaxially; A flat plate support frame is arranged between the Helmholtz coil pair, and a flat plate plane of the flat plate support frame is parallel to the axis of the Helmholtz coil pair; A measuring module is arranged above the plate support frame and between the Helmholtz coil pairs to measure the magnetic field strength at a number of measuring 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.

8. A system for measuring the magnetic permeability of a flat plate according to claim 7, characterized in that: The flat plate of the flat plate support frame 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.

9. A system for measuring the magnetic permeability of a flat plate according to claim 7 or 8, 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 plate of the flat plate support frame and detects the magnetic field strength at a number of measurement points.

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

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