Permanent magnet magnetization control method and magnetizer based on magnetic domain dynamics

Abstract

The present invention provides a permanent magnet magnetization control method and magnetizer based on magnetic domain dynamics, specifically relating to the technical field of permanent magnet magnetization. A three-dimensional model of the permanent magnet to be magnetized is obtained, and the three-dimensional model is divided into multiple magnetic domain units; the magnetic moment dynamics equation of each magnetic domain unit is obtained; when not magnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed, and under the action of an effective magnetic field, the magnetic moments of each magnetic domain undergo spin precession, and the magnetic moment directions approach the effective magnetic field direction; the magnetic moment directions of each magnetic domain unit at different times are numerically solved, and based on the instantaneous magnetic moment directions of the magnetic domain units at different times, the change trajectory of the magnetic moment directions of the magnetic domain units starting from the initial magnetic moment direction is determined; based on the change trajectory, the degree of consistency of the magnetic moment directions of each magnetic domain unit is determined, and a relationship map of magnetization saturation, pulse magnetic field intensity, and pulse duration is generated. This method can improve the accuracy and efficiency of magnetization.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet magnetization, and in particular to a permanent magnet magnetization control method and a magnetizer based on magnetic domain dynamics. Background Art

[0002] Permanent magnetization is a crucial process for magnetizing permanent magnetic materials. Related technologies often rely on macroscopic hysteresis models, such as the Jiles-Atherton model and the Preisach model. These models struggle to account for microscopic magnetic domain motion. They primarily calculate hysteresis loops based on a given magnetic field strength and lack in-depth research into the motion and physical mechanisms of magnetic domains during magnetization. While some studies have explored the simplified domain model and the six-domain model from a microscopic perspective, these models cannot accurately simulate the magnetic moment precession of a single domain under an external magnetic field, deviating from the actual physical process. Summary of the Invention

[0003] In order to address the deficiencies of the prior art, the purpose of the present application is to provide a permanent magnet magnetization control method and a magnetizer based on magnetic domain dynamics, which can improve the accuracy and efficiency of magnetization.

[0004] In a first aspect, the present application provides a permanent magnet magnetization control method based on magnetic domain dynamics, the method comprising:

[0005] Obtaining a three-dimensional model of the permanent magnet to be magnetized, dividing the three-dimensional model into a plurality of cubic units, each cubic unit being a magnetic domain unit;

[0006] Obtaining a dynamic equation for each magnetic domain unit; wherein the dynamic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit;

[0007] Determine the initial magnetic moment direction of each magnetic domain unit; when not magnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed to simulate a state where the initial magnetization intensity is zero. Under the action of an effective magnetic field, each magnetic domain unit undergoes spin precession, and the magnetic moment direction of each magnetic domain unit gradually approaches the effective magnetic field direction;

[0008] Solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation, and determining the change trajectory of the magnetic moment direction of each magnetic domain unit starting from the initial magnetic moment direction according to the instantaneous magnetic moment direction of the magnetic domain unit at different times;

[0009] According to the magnetic moment direction change trajectory of each magnetic domain unit, the degree of consistency of the magnetic moment direction of the magnetic domain unit is determined, and a relationship map between the magnetization saturation and the pulse magnetic field intensity and the pulse duration is generated; wherein, the magnetizer can perform magnetization control on the permanent magnet to be magnetized according to the target magnetic field intensity and target magnetization time determined from the relationship map.

[0010] In one embodiment, the dynamic equation introduces a spin precession equation with a damping term based on the principle of magnetic moment dynamics, and the damping term controls the speed at which the instantaneous magnetic moment direction approaches the effective magnetic field direction through the damping coefficient α.

[0011] In one embodiment, obtaining the dynamic equation of each magnetic domain unit includes:

[0012] The dynamic behavior of each magnetic domain unit is described by the LLG equation;

[0013] The LLG equation sets the magnetization intensity of each magnetic domain unit to be constant and the magnetic moment direction to be variable, and the dynamic equation of each magnetic domain unit is obtained;

[0014] The dynamic equation of the magnetic domain unit includes the gyromagnetic ratio, the damping coefficient α and the effective magnetic field H eff .

[0015] In one embodiment, the dynamic equation of the magnetic domain unit is:

[0016] ;

[0017] in, Represents magnetic domain unit m i The instantaneous magnetic moment direction, represents the gyromagnetic ratio, α represents the damping coefficient, represents the effective magnetic field.

[0018] In one embodiment, the effective magnetic field is calculated by superposing the following components:

[0019] The external magnetizing magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized;

[0020] The exchange field component between adjacent magnetic domains is the interaction between adjacent magnetic domain units;

[0021] The material anisotropy field component is determined by the structure of the permanent magnet to be magnetized;

[0022] The demagnetization field component is calculated by multiplying the magnetization intensity by the demagnetization tensor.

[0023] In one embodiment, solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation includes:

[0024] Set the time step Δt and iteratively calculate the instantaneous magnetic moment direction according to the time step Δt;

[0025] For each time step Δt, the Runge-Kutta method is used to solve the dynamic equations and update the instantaneous magnetic moment direction;

[0026] The iterative calculation of the instantaneous magnetic moment direction is stopped until the three-dimensional model of the permanent magnet to be magnetized reaches magnetization saturation.

[0027] In one embodiment, the unmagnetized state of the permanent magnet to be magnetized is simulated by:

[0028] The magnetic moment direction is randomly assigned to each magnetic domain unit, and the magnetic moment direction of each magnetic domain unit is evenly distributed in three-dimensional space;

[0029] Among them, when not magnetized, the magnetic moment directions of each magnetic domain unit are different, cancel each other out and appear in a scattered state. The initial magnetization saturation when not magnetized is calculated by the average angle between the magnetic moment direction and the easy magnetization axis, and the angle range is 85° to 95°.

[0030] In one embodiment, for the permanent magnet to be magnetized, when the effective magnetic field action time is less than the target magnetization time and / or the intensity of the effective magnetic field is less than the target magnetic field intensity, the magnetic moment direction of the magnetic domain unit is not completely consistent with the effective magnetic field direction; and / or

[0031] For the permanent magnet to be magnetized, when the effective magnetic field action time is less than the target magnetization time and / or the effective magnetic field strength is less than the target magnetic field strength, the magnetic moment direction of the magnetic domain unit is not completely reversed relative to the initial magnetic moment direction.

[0032] In one embodiment, the relationship between magnetization saturation and pulse magnetic field strength and pulse duration includes:

[0033] When the pulse magnetic field intensity does not reach the target pulse magnetic field intensity, the magnetization saturation increases with the increase of the pulse magnetic field intensity and pulse duration;

[0034] Under a constant pulse magnetic field strength, increasing the pulse duration can stabilize the magnetization saturation at a certain value rather than increasing it indefinitely;

[0035] Under the target pulse magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be saturated magnetized. If the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturation magnetization.

[0036] In a second aspect, the present application further provides a magnetizer, comprising:

[0037] A magnetizing circuit, used for magnetizing the permanent magnet to be magnetized;

[0038] The controller includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the permanent magnet magnetization control method based on magnetic domain dynamics of the first aspect is implemented.

[0039] The above-mentioned permanent magnet magnetization control method based on magnetic domain dynamics divides the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, obtains the dynamic equation of each magnetic domain unit, and determines its initial magnetic moment direction to simulate the scattered state when not magnetized; solves the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation, and determines the change trajectory of the magnetic moment direction; determines the consistency of the magnetic moment direction based on the change trajectory of the magnetic moment direction, and generates a relationship map between the magnetization saturation and the pulse magnetic field intensity and duration, thereby providing accurate control parameters for the magnetizer to ensure that the permanent magnet achieves the best magnetization effect. In this method, the pulse magnetic field intensity and pulse duration are incorporated into the factors affecting the magnetization saturation. By dividing the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, the spatial distribution of the permanent magnet is also incorporated into the influence of the magnetization saturation, thereby improving the accuracy and efficiency of magnetization. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of a permanent magnet magnetization control method based on magnetic domain dynamics in one embodiment;

[0041] Figure 2 A flowchart of obtaining a dynamic equation for each magnetic domain unit in one embodiment;

[0042] FIG3 (a) and FIG3 (b) are diagrams of an unsaturated magnetized magnetic domain model and a saturated magnetized magnetic domain model of a unit magnetic domain in one embodiment, respectively;

[0043] Figure 4 A flowchart of solving the instantaneous magnetic moment direction of each magnetic domain unit at different moments based on the dynamic equation in one embodiment;

[0044] Figure 5 FIG. 1 is a diagram of a magnet model in an unmagnetized state according to an embodiment;

[0045] Figure 6 FIG. 1 is a diagram of a magnet model in an unsaturated magnetization state according to an embodiment;

[0046] Figure 7 FIG. 1 is a diagram of a magnet model in a saturated magnetization state according to an embodiment;

[0047] Figure 8 Schematic diagram of the effect of magnetic field intensity and duration on magnetization saturation in one embodiment;

[0048] Figure 9 Schematic diagram of the effect of magnetic field intensity and duration on residual magnetism in one embodiment;

[0049] Figure 10 FIG. 4 is a circuit diagram of a magnetizing circuit in one embodiment. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of this application more clear, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application. Unless otherwise defined, the technical terms or scientific terms involved in this application should have the general meaning understood by people with ordinary skills in the technical field to which this application belongs.

[0051] In one embodiment, Figure 1 As shown, a permanent magnet magnetization control method based on magnetic domain dynamics is provided, which includes the following steps:

[0052] Step 101: Obtain a three-dimensional model of a permanent magnet to be magnetized, and divide the three-dimensional model into a plurality of cubic units, each cubic unit being a magnetic domain unit;

[0053] Obtain a three-dimensional model of the permanent magnet to be magnetized. This three-dimensional model can describe the geometric shape and size of the permanent magnet to be magnetized. Further, the three-dimensional model can be divided into multiple cubic units. Each cubic unit can be used as an independent magnetic domain unit. Its size is determined according to the calculation accuracy. The unit volume is generally selected to be about 1mm. 3 , in order to accurately simulate the magnetization behavior of the magnetic domain. Each magnetic domain unit has an independent magnetic moment vector, whose initial direction is determined by a generated random number to reflect the scattered distribution of the magnetic moment of the magnetic domain in the unmagnetized state.

[0054] Step 102: Obtaining a dynamic equation for each magnetic domain unit; wherein the dynamic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit;

[0055] For each magnetic domain unit, a dynamic equation for each magnetic domain unit is obtained. The dynamic equation corresponding to each magnetic domain unit is the Landau-Lifshitz-Gilbert (LLG) equation, which is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit under the action of a pulsed magnetic field.

[0056] It should be noted that the dynamic equations for the magnetic domain unit take into account the spin precession of the magnetic moment, the damping effect, and the influence of the external magnetic field on the direction of the magnetic moment. By solving the dynamic equations for the magnetic domain unit, the temporal variation of the magnetic moment vector direction of each magnetic domain unit can be obtained, thereby accurately simulating the magnetization process of the permanent magnet. The method used to solve the dynamic equations for the magnetic domain unit is the fourth-order Runge-Kutta method to ensure the accuracy and stability of the calculation.

[0057] Step 103: determining the initial magnetic moment direction of each magnetic domain unit; when not magnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed to simulate a state where the initial magnetization intensity is zero. Under the action of the effective magnetic field, each magnetic domain unit undergoes spin precession, and the magnetic moment direction of each magnetic domain unit gradually approaches the effective magnetic field direction;

[0058] When unmagnetized, the magnetic moment directions of each domain unit are randomly distributed and mutually offset. This is used to simulate a state where the initial magnetization intensity is zero. Furthermore, under the action of an effective magnetic field, each domain unit begins to spin precess, and the direction of the magnetic moment of each domain unit can gradually approach the direction of the effective magnetic field.

[0059] Specifically, the direction of the magnetic moment vector of each magnetic domain unit is initially set using a random number generator to ensure that it has different orientations in three-dimensional space, thereby reflecting the scattered distribution of magnetic moments in the unmagnetized state. When an effective magnetic field is applied, the magnetic moment vector of each magnetic domain unit can spin precess according to its dynamic equation. During the spin precession process, the magnetic moment vector is gradually guided by the effective magnetic field, and its direction gradually converges to the direction of the effective magnetic field.

[0060] Step 104: solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation, and determining, for each magnetic domain unit, a change trajectory of the magnetic moment direction of the magnetic domain unit starting from the initial magnetic moment direction according to the instantaneous magnetic moment direction of the magnetic domain unit at different times;

[0061] Specifically, the magnetic moment of each domain is initially random, representing a scattered distribution of magnetic moments in the unmagnetized state. With the application of an external effective magnetic field, the magnetic moment begins to change according to the laws described by the dynamical equations, typically gradually moving from the initial random direction toward the direction of the effective magnetic field.

[0062] By recording the magnetic moment direction of each magnetic domain unit at each time step, we can plot the trajectory of the magnetic moment direction over time. The trajectory of the change in the magnetic moment direction of the magnetic domain unit from the initial magnetic moment direction can show the entire evolution process of the magnetic moment from the initial state to the stable state. It should be noted that for each magnetic domain unit, the dynamic equations can be solved using numerical methods, such as the Runge-Kutta method, to obtain the instantaneous direction of the magnetic moment at each time step.

[0063] Step 105: Determine the consistency of the magnetic moment directions of the magnetic domain units according to the magnetic moment direction change trajectory of each magnetic domain unit, and generate a relationship map of the magnetization saturation, the pulse magnetic field intensity, and the pulse duration; wherein the magnetizer can perform magnetization control on the permanent magnet to be magnetized according to the target magnetic field intensity and the target magnetization time determined from the relationship map.

[0064] By analyzing the trajectory of the magnetic moment direction changes of all magnetic domain units, the degree of consistency between the magnetic moment direction of each magnetic domain unit and the effective magnetic field direction is calculated under different pulse magnetic field intensities and durations, thereby obtaining the magnetization saturation. The magnetization saturation reflects the degree of magnetization of the permanent magnet under different magnetization conditions. The relationship diagram can intuitively display the relationship between the pulse magnetic field intensity and pulse duration as the horizontal and vertical axes, and the magnetization saturation as a visual element such as color or height.

[0065] Furthermore, the magnetizer can perform magnetization control on the permanent magnet to be magnetized according to the target magnetic field strength and target magnetization time determined from the relationship map. That is, according to the required magnetization saturation, the corresponding pulse magnetic field strength and duration are found in the relationship map, thereby accurately controlling the magnetization process and ensuring that the permanent magnet achieves the expected magnetization effect.

[0066] In this embodiment, the method divides the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, obtains the dynamic equation of each magnetic domain unit, and determines its initial magnetic moment direction to simulate the scattered state when not magnetized; based on the dynamic equation, the instantaneous magnetic moment direction of each magnetic domain unit at different times is solved to determine the change trajectory of the magnetic moment direction; according to the change trajectory of the magnetic moment direction, the consistency of the magnetic moment direction is determined, and a relationship map between the magnetization saturation and the pulse magnetic field intensity and duration is generated, thereby providing accurate control parameters for the magnetizer to ensure that the permanent magnet achieves the best magnetization effect. In this method, the pulse magnetic field intensity and pulse duration are incorporated into the factors affecting the magnetization saturation. By dividing the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, the spatial distribution of the permanent magnet is also incorporated into the influence of the magnetization saturation, thereby improving the accuracy and efficiency of magnetization.

[0067] In one embodiment, the dynamic equation introduces a spin precession equation with a damping term based on the principle of magnetic moment dynamics. The damping term controls the speed at which the instantaneous magnetic moment direction approaches the effective magnetic field direction through the damping coefficient α.

[0068] The dynamic equation can describe the dynamics of magnetic moment from a microscopic mechanism, and can reflect the influence of magnetizing magnetic field intensity, magnetic field duration, ferromagnetic material, etc. on the change of magnetic moment direction.

[0069] In micromagnetism, the relationship between magnetization intensity M and angular momentum L is:

[0070] ;

[0071] in, γ is the gyromagnetic ratio, which is , in the effective field H eff Under the action of T for:

[0072] .

[0073] in, μ 0 is the vacuum magnetic permeability, M is the magnetization intensity, H eff is the effective field.

[0074] Effective field H eff Expressed as:

[0075] .

[0076] in, μ s is the magnetic permeability, which indicates the material’s ability to respond to a magnetic field in a certain direction. is the Hamiltonian of the magnetic system, including the exchange energy, anisotropy energy, interaction energy and Zeeman energy of the magnetic system.

[0077] The expression of Hamiltonian is:

[0078] .

[0079] in, is the exchange energy of the magnetic system, is the anisotropic energy, For the interaction energy, is the external magnetic field energy.

[0080] According to the angular momentum theorem, .

[0081] The magnetization M and angular momentum L Substituting the relationship between and the expression of magnetization torque into the angular momentum theorem, we get:

[0082] .

[0083] This equation can express the precession form of the spin magnetization vector in the external magnetic field, but does not take into account the damping dissipation. Starting from the Lagrange equation, the damping term is derived: T D for:

[0084] ;

[0085] in, α is the damping constant, M S is the saturation magnetization intensity, so the magnetization dynamics equation considering damping dissipation is:

[0086] .

[0087] Performing M× operations on both sides simultaneously yields:

[0088]

[0089]

[0090] .

[0091] Arrange the formula, the magnetization dynamics equation is:

[0092] .

[0093] Among them, placing the differential terms on the left side of the equation is more conducive to numerical simulation. Macroscopically, the magnetization intensity is a function of time and position, and its value is the vector sum of all magnetic moments.

[0094] In this embodiment, the dynamic equation introduces a damping term and uses the damping coefficient α Controlling the speed at which the direction of the instantaneous magnetic moment approaches the direction of the effective magnetic field can accurately simulate the dynamic changes of the magnetic moment under the action of the external field and improve the accuracy and reliability of the magnetization simulation.

[0095] In one embodiment, Figure 2 As shown, obtaining the dynamic equation of each magnetic domain unit includes the following steps:

[0096] Step 201: The dynamic behavior of each magnetic domain unit is described by the LLG equation; wherein the dynamic equation of the magnetic domain unit includes the gyromagnetic ratio, the damping coefficient α and effective magnetic field H eff .

[0097] The dynamic behavior of each magnetic domain unit can be described by the LLG equation. The LLG equation integrates the precession and damping effects of the magnetic moment and can accurately simulate the dynamic changes of the magnetic moment under the action of an external field.

[0098] Among them, the gyromagnetic ratio γ is a constant related to material properties, which can reflect the precession speed of the magnetic moment under the action of unit magnetic field. Its value is 2.21×10 5 m / (As). The damping coefficient α can control the speed at which the direction of the magnetic moment approaches the direction of the effective magnetic field. A larger α value means that the direction of the magnetic moment changes faster and can align with the effective field direction more quickly. A smaller α value means that the direction of the magnetic moment changes slower and the precession process lasts longer. Effective magnetic field H eff It is the total magnetic field where the magnetic moment is located, which includes not only the externally applied magnetizing magnetic field, but also the anisotropic field and exchange field inside the material. Heff The direction and magnitude of the magnetic moment jointly determine the precession trajectory and the final stable direction.

[0099] Step 202: The magnetization intensity of each magnetic domain unit in the LLG equation is set to be constant and the magnetic moment direction is set to be variable, thereby obtaining a dynamic equation for each magnetic domain unit.

[0100] In order to simplify the calculation and focus on the change in the direction of the magnetic moment, the magnetization intensity of each magnetic domain unit is set to constant in the LLG equation, and only the direction of the magnetic moment is allowed to change, thereby obtaining the dynamic equation of each magnetic domain unit suitable for magnetization analysis.

[0101] For example, assuming that the magnetization intensity of each magnetic domain unit is constant, the effective magnetic field only affects its direction. Assuming that the magnetization intensity of each magnetic domain unit is 1, the saturation magnetization intensity is used as the reference value, that is:

[0102] .

[0103] Among them, x, y, z are the x-axis direction, y-axis direction and z-axis direction in space. m i For the i The magnetization intensity vector of each magnetic domain unit after normalization.

[0104] In one embodiment, the dynamic equation of the magnetic domain unit is:

[0105] ;

[0106] in, Represents magnetic domain unit m i The instantaneous magnetic moment direction, represents the gyromagnetic ratio, α represents the damping coefficient, H eff Represents the effective magnetic field.

[0107] Specifically, m i It is i The normalized magnetization intensity vector of each magnetic domain unit has a modulus that remains 1, and only the direction changes; γ is the gyromagnetic ratio, which is a constant related to material properties and reflects the precession speed of the magnetic moment under the action of unit magnetic field; H eff It is the effective field, including the externally applied magnetic field and the anisotropic field and exchange field inside the material; α is the damping coefficient, which controls the rate at which the direction of the magnetic moment changes.

[0108] In this embodiment, through the dynamic equation of the magnetic domain unit, it is possible to focus on simulating the dynamic evolution process of the magnetic moment direction under the action of the external field without considering the change in the magnetization intensity, thereby more efficiently analyzing and predicting the magnetization behavior of the permanent magnet.

[0109] In one embodiment, for a unit magnetic domain, m 0 is the initial magnetic moment. Under the action of the effective field, the magnetic moment vector undergoes spin precession, gradually approaching the direction of the effective field. When the effective field is applied for too short a time or is insufficiently strong, according to the magnetic moment dynamics equation, the magnetic moment direction will not ultimately completely align with the effective field direction, but will instead remain at a certain position during the precession motion, as shown in Figure 3(a). This is an incomplete reversal of the magnetic domains and a microscopic manifestation of incomplete magnetization. When the effective field strength and duration are sufficient, the direction of the magnetic moment vector is essentially consistent with the effective field direction at the end of the action, as shown in Figure 3(b). The magnetic domains have completely flipped, and the magnetic moment vector is aligned with the effective field direction.

[0110] In one embodiment, the effective magnetic field is calculated by superposing the following components:

[0111] The external magnetizing magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized;

[0112] The exchange field component between adjacent magnetic domains is the interaction between adjacent magnetic domain units;

[0113] The material anisotropy field component is determined by the structure of the permanent magnet to be magnetized;

[0114] The demagnetization field component is calculated by multiplying the magnetization intensity by the demagnetization tensor.

[0115] In the modeling of the permanent magnet magnetization process, the effective magnetic field H eff It is obtained by superposition calculation of multiple components, including: external magnetizing magnetic field component, exchange field component between adjacent magnetic domains, material anisotropy field component and demagnetization field component.

[0116] Among them, the external magnetizing magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized, is the main driving force in the magnetization process and determines the basic orientation of the magnetic moment; the exchange interaction field component between adjacent magnetic domains originates from the interaction between adjacent magnetic domain units. This exchange interaction tends to make the directions of adjacent magnetic moments consistent; the material anisotropy field component is determined by the structure of the permanent magnet to be magnetized, such as crystal anisotropy or shape anisotropy, which makes the magnetic moment more stable in certain directions; the demagnetization field component is calculated by the product of the magnetization intensity and the demagnetization tensor, reflecting the reverse magnetic field generated by the magnetic moment itself. Its magnitude and direction depend on the distribution of the magnetization intensity and the shape of the permanent magnet.

[0117] In this embodiment, the dynamic behavior of the magnetic moment during the magnetization process and the final magnetization state are determined by the combined action of these components.

[0118] In one embodiment, Figure 4 As shown, solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation includes the following steps:

[0119] Step 401: setting a time step Δt, and iteratively calculating the instantaneous magnetic moment direction according to the time step Δt;

[0120] Step 402: For each time step Δt, the Runge-Kutta method is used to solve the dynamic equations and update the instantaneous magnetic moment direction;

[0121] A time step, Δt, is set as the basic unit of time advancement during the calculation process. This time step, Δt, can be determined based on the required computational accuracy and efficiency, typically ranging from nanoseconds to microseconds. If Δt is set, the calculation is iterated at this time step to gradually determine the instantaneous magnetic moment direction of each magnetic domain unit.

[0122] For each time step Δt, the Runge-Kutta method can be used to solve the dynamical equations and update the instantaneous magnetic moment direction. The Runge-Kutta method is a commonly used numerical method for solving ordinary differential equations. It improves the accuracy of the solution by calculating multiple intermediate slopes within each time step to estimate the value of the next time step.

[0123] It should be noted that within each time step Δt, the four stages of the Runge-Kutta method are used to calculate the change in the direction of the magnetic moment: the slope k1 of the current time step is calculated, based on the current magnetic moment direction and the effective field;

[0124] Use k1 to estimate the intermediate state and calculate the slope k2; use k2 again to estimate another intermediate state and calculate the slope k3; finally, use k3 to calculate the final slope k4. By calculating the four slopes, a more accurate formula for updating the magnetic moment direction can be obtained, thereby accurately updating the magnetic moment direction within each time step Δt.

[0125] Step 403: until the three-dimensional model of the permanent magnet to be magnetized reaches magnetization saturation, the iterative calculation of the instantaneous magnetic moment direction is stopped.

[0126] At each time step, the Runge-Kutta method is used to solve the dynamic equations and update the instantaneous magnetic moment direction. This process continues until the three-dimensional model of the permanent magnet to be magnetized reaches magnetization saturation, that is, the magnetic moment direction of most magnetic domain units is basically consistent with the effective field direction, and the magnetization saturation reaches the expected value. At this time, the iterative calculation of the instantaneous magnetic moment direction is stopped. For example, the magnetization saturation can be determined by calculating the degree of deviation between the magnetic moment direction of all magnetic domain units and the effective field direction. When the deviation is less than a preset threshold, the permanent magnet is considered to have reached magnetization saturation.

[0127] In this embodiment, by setting an appropriate time step Δt and using the Runge-Kutta method to solve the dynamic equations, the change of the magnetic moment direction over time can be accurately simulated, thereby accurately capturing the dynamic behavior of the magnetic moment during the magnetization process; by judging the magnetization saturation to stop the iterative calculation, computing resources can be effectively saved, unnecessary calculations can be avoided, and simulation efficiency can be improved.

[0128] In one embodiment, the unmagnetized state of the permanent magnet to be magnetized is simulated by:

[0129] The magnetic moment direction is randomly assigned to each magnetic domain unit, and the magnetic moment direction of each magnetic domain unit is evenly distributed in three-dimensional space;

[0130] Among them, when not magnetized, the magnetic moment directions of each magnetic domain unit are different, cancel each other out and appear in a scattered state. The initial magnetization saturation when not magnetized is calculated by the average angle between the magnetic moment direction and the easy magnetization axis, and the angle range is 85° to 95°.

[0131] During the initial stage of simulating the magnetization process of a permanent magnet, the magnetic moment directions of each domain unit are randomly assigned, and these directions are evenly distributed in three-dimensional space. This is intended to ensure that, when unmagnetized, the magnetic moment directions within the permanent magnet are scattered, with the directions of each domain unit differing and canceling each other out, resulting in a non-magnetic permanent magnet overall. This initial state setting is consistent with actual conditions and accurately reflects the physical properties of an unmagnetized permanent magnet.

[0132] Specifically, the initial magnetization saturation when not magnetized can be calculated by the average angle between the magnetic moment direction and the easy magnetization axis, and the angle range is set to 85° to 95°. The physical significance of setting the angle range is that the easy magnetization axis is the direction that is most easily magnetized in a permanent magnet. In the unmagnetized state, the magnetic moment direction should be almost perpendicular to the easy magnetization axis to ensure that the initial magnetization saturation is low. Selecting an angle range of 85° to 95° can ensure that the magnetic moment direction is almost perpendicular to the easy magnetization axis at the initial stage, so that the initial magnetization saturation is close to zero, which is consistent with the physical characteristics of the unmagnetized state.

[0133] In one embodiment, for the permanent magnet to be magnetized, when the action time of the effective magnetic field is less than the target magnetization time and / or the intensity of the effective magnetic field is less than the target magnetic field intensity, the magnetic moment direction of the magnetic domain unit is not completely consistent with the effective magnetic field direction; and / or

[0134] For the permanent magnet to be magnetized, when the effective magnetic field action time is less than the target magnetization time and / or the effective magnetic field strength is less than the target magnetic field strength, the magnetic moment direction of the magnetic domain unit is not completely reversed relative to the initial magnetic moment direction.

[0135] The target magnetization time may refer to the shortest time set to achieve full magnetization of the permanent magnet, and the target magnetic field strength may refer to the minimum magnetic field strength required to enable the permanent magnet to reach a saturated magnetization state.

[0136] When the effective magnetic field duration is shorter than the target magnetization time, and / or the effective magnetic field strength is less than the target magnetic field strength, the magnetic moment direction of the magnetic domain unit will not be completely consistent with the effective magnetic field direction, nor will it be completely reversed relative to the initial magnetic moment direction.

[0137] Specifically, if the effective magnetic field does not act for a long enough time, the magnetic moment will not have enough time to fully align with the effective field direction; and if the strength of the effective magnetic field is not strong enough, the magnetic moment will not be able to obtain enough energy to overcome obstacles such as anisotropy and demagnetization field, and thus will not be able to complete the complete flipping process.

[0138] In this embodiment, both situations may cause the direction of the magnetic moment to remain in an intermediate state, neither completely aligned with the effective field direction nor completely returning to the initial direction, thereby affecting the magnetization effect.

[0139] In one embodiment, the magnet model in the unmagnetized state is as follows: Figure 5 As shown in the figure, when not magnetized, the magnetic moment vectors in each magnetic domain of the permanent magnet are different from each other, cancel each other out, and appear scattered. The magnet model of the unsaturated magnetization state is as follows: Figure 6 As shown in the figure, when the magnetic field strength or duration is insufficient, each magnetic domain has undergone precession flipping, but has not completely tended to the direction of the external magnetic field, that is, there is no saturation magnetization. The magnet model of the saturation magnetization state is as follows: Figure 7 As shown in FIG, when given a sufficient magnetic field strength and a sufficient duration, the permanent magnet is saturated and magnetized, and most of the magnetic domains are flipped and completely tend to the effective field direction.

[0140] In one embodiment, the relationship between magnetization saturation, pulse magnetic field strength, and pulse duration includes:

[0141] When the pulse magnetic field intensity does not reach the target pulse magnetic field intensity, the magnetization saturation increases with the increase of the pulse magnetic field intensity and pulse duration;

[0142] Specifically, when the pulsed magnetic field intensity does not reach the target pulsed magnetic field intensity, the magnetization saturation increases with increasing pulsed magnetic field intensity and pulse duration. When the pulsed magnetic field intensity is low, the magnetic moments require more pulse duration to overcome internal resistance and gradually align in the direction of the magnetic field. As the pulsed magnetic field intensity increases, the magnetic moments align more easily, and the increase in pulse duration provides the magnetic moments with more time to respond to the magnetic field. Therefore, when the target magnetic field intensity is not reached, the increase in pulsed magnetic field intensity and pulse duration jointly promotes the improvement of magnetization saturation.

[0143] Under a constant pulse magnetic field strength, increasing the pulse duration can stabilize the magnetization saturation at a certain value rather than increasing it indefinitely;

[0144] Specifically, under a constant pulse magnetic field strength, as the pulse duration increases, the direction of the magnetic moment gradually aligns with the direction of the magnetic field, and the magnetization saturation gradually increases. When most of the magnetic moments have been aligned, even if the pulse duration continues to increase, the number of remaining unaligned magnetic moments is already very small, and the effect on improving the magnetization saturation is limited. Due to the damping effect and energy dissipation inside the material, the alignment speed of the magnetic moment will gradually slow down as the action time increases, and eventually reach a dynamic equilibrium, causing the magnetization saturation to tend to a stable value. Therefore, under a constant pulse magnetic field strength, increasing the pulse duration will cause the magnetization saturation to gradually tend to a stable value, rather than increasing indefinitely.

[0145] Under the target pulse magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be saturated magnetized. If the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturation magnetization.

[0146] Specifically, when the magnetic field strength is sufficient, it takes a certain amount of time for the magnetic moment to overcome internal resistance and gradually align with the magnetic field direction. If the pulse duration is long enough, the magnetic moment has enough time to complete the alignment, thus achieving saturation magnetization. However, if the pulse duration is less than the target magnetization time, the magnetic moment does not have enough time to fully align, resulting in insufficient magnetization saturation and failure to achieve saturation magnetization. Therefore, only when the pulse duration reaches the target magnetization time can the magnetic moment be fully aligned and saturation magnetization be achieved.

[0147] In one embodiment, Figure 8The figure shows how magnetization saturation varies with magnetic field strength at different pulse durations. The horizontal axis represents magnetic field strength (A / m), and the vertical axis represents magnetization saturation. Curves of different colors and symbols correspond to different pulse durations (ranging from 1.ms to 6ms). When the applied magnetic field strength is 600kA / m, the maximum magnetic field strength does not reach the saturation magnetization field strength of the permanent magnet model. Even with sufficiently long durations, the final magnetization saturation remains around 50%. When the applied magnetic field strength is increased to 800kA / m, the magnetization speed significantly accelerates between 0 and 1.5ms. However, the magnetic field strength still does not reach saturation magnetization. Although most magnetic domains have completed reversal, approximately 40% of the domains remain misaligned with the easy axis, resulting in a final saturation level of approximately 80%.

[0148] When the peak value of the magnetizing magnetic field reaches 1000kA / m, the permanent magnet reaches saturation, the magnetic domain unit basically completes the flip, and the magnetization speed is significantly improved. After reaching saturation magnetization, the further increase of the external magnetic field intensity will increase the magnetization saturation to a certain extent within the same duration.

[0149] In summary, the dynamic equations for magnetic domain units constructed based on the LLG equations effectively reflect the influence of magnetizing field strength and duration on the magnetization effect. The relationship between magnetic field strength and duration can be summarized as follows: before the saturation magnetization field strength is reached, the magnetization saturation increases with increasing field strength and duration. At a certain field strength, further increasing duration stabilizes the magnetization saturation at a certain value, rather than increasing indefinitely. Once the saturation magnetization strength is reached, the sample can be saturated if the duration is sufficient. However, if the duration is insufficient, saturation magnetization cannot be achieved.

[0150] In one embodiment, Figure 9 The figure shows how remanence changes with magnetic field strength at different pulse durations. The horizontal axis represents magnetic field strength (in A / m), and the vertical axis represents remanence (in mT). Curves of different colors and symbols correspond to different pulse durations (ranging from 1.05ms to 6.20ms). It should be noted that remanence refers to the magnetization retained in a magnetic material after the applied pulse magnetic field is removed and is an important indicator of the material's magnetization capacity.

[0151] At low magnetic field intensities, remanence increases rapidly with increasing magnetic field strength, and the curves for different durations vary significantly, indicating that pulse duration has a significant impact on remanence. At high magnetic field intensities, remanence approaches saturation, and the curves become flat. The curves for different durations converge, indicating that when the magnetic field strength is high enough, the effect of pulse duration on remanence decreases. Therefore, remanence is closely related not only to magnetic field strength but also to pulse duration, especially in the low magnetic field strength region. Once the magnetic field strength reaches saturation, further increases in magnetic field strength or duration have little effect on the remanence.

[0152] In one embodiment, during the magnetization process, the effective magnetic field strength is typically not constant but varies dynamically over time. This variation may be due to the characteristics of the magnetizing equipment, power supply fluctuations, or intentional design to implement a specific magnetization strategy. The effect of this dynamically changing effective magnetic field strength on the direction of the magnetic moment can be simulated by introducing a time-varying term into the kinetic equations. For example, in the (LLG) equation, the effective magnetic field strength is set as a function of time, thereby more accurately describing the dynamic behavior of the magnetic moment under the influence of an external field. In this way, the magnetization process can be optimized and the magnetization effect can be improved.

[0153] Based on the same concept, the present application also provides a magnetizer, which includes:

[0154] Magnetizing circuit, such as Figure 10 As shown, it is used to magnetize the permanent magnet to be magnetized;

[0155] The 0~1000V DC power supply on the left side of the magnetizing circuit is used to provide energy for the entire circuit. K 1 and current limiting resistor R 1 (1kΩ), can control the charging process of the circuit. Multiple capacitors ( C =400μF, U =1800V) are connected in parallel to form energy storage capacitors to store electrical energy. These capacitors accumulate energy during the charging process and then release it quickly during the discharge process, generating a pulse current. K 2 is used to control the start of the magnetization process. K 2 When closed, the capacitor bank discharges through the magnetizing coil, generating a pulse magnetic field. DL It plays a protective role, preventing the reverse flow of current during the discharge process and causing damage to other components in the circuit. The magnetizing coil is the core part of the circuit. After experimental measurement, its inductance L =106.65mH, resistance R L= 0.63Ω. When the capacitor bank discharges through the coil, a pulsed magnetic field is generated in the coil, which is used to magnetize the permanent magnet. The ground wire (GND) is used to ground the circuit, ensuring safe and stable operation.

[0156] The working principle of the magnetizing circuit is to close the switch K 1. The power supply charges the capacitor bank, which stores electrical energy. When the capacitor bank is charged to the required voltage, disconnect the switch. K 1 Close the switch K 2. The capacitor bank is rapidly discharged through the magnetizing coil, generating a pulsed magnetic field. This field acts on the permanent magnet to be magnetized, changing the direction of its magnetic moment, thereby achieving magnetization. Circuit parameters (such as capacitor capacity and inductance) can be adjusted to meet the desired pulsed magnetic field intensity and duration to meet different magnetization requirements.

[0157] The controller includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, a permanent magnet magnetization control method based on magnetic domain dynamics is implemented.

[0158] The processor can dynamically adjust magnetization parameters, such as magnetic field strength and duration, based on real-time data during the magnetization process and preset control strategies to ensure that the permanent magnet can achieve the best magnetization effect.

[0159] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The above embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A permanent magnet magnetization control method based on magnetic domain dynamics, characterized in that: The method comprises: Obtaining a three-dimensional model of a permanent magnet to be magnetized, and dividing the three-dimensional model into a plurality of cubic units, each cubic unit serving as a magnetic domain unit; Obtain a kinetic equation for each magnetic domain unit; the kinetic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit, and the kinetic equation is: , Represents magnetic domain unit m i The instantaneous magnetic moment direction, represents the gyromagnetic ratio, α represents the damping coefficient, H eff represents the effective magnetic field; Determining the initial magnetic moment direction of each magnetic domain unit; when not magnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed to simulate a state where the initial magnetization intensity is zero. Under the action of the applied effective magnetic field, each magnetic domain unit undergoes spin precession, and the magnetic moment direction of each magnetic domain unit gradually approaches the effective magnetic field direction; Solving the instantaneous magnetic moment direction of each magnetic domain unit at different moments based on the dynamic equation, and determining, for each magnetic domain unit, a change trajectory of the magnetic moment direction of the magnetic domain unit starting from the initial magnetic moment direction according to the instantaneous magnetic moment direction of the magnetic domain unit at different moments; According to the magnetic moment direction change trajectory of each magnetic domain unit, the degree of consistency of the magnetic moment direction of the magnetic domain unit is determined, and a relationship map between the magnetization saturation and the pulse magnetic field intensity and the pulse duration is generated; wherein the magnetizer can perform magnetization control on the permanent magnet to be magnetized according to the target magnetic field intensity and target magnetization time determined from the relationship map.

2. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that: The dynamic equation introduces a spin precession equation with a damping term based on the principle of magnetic moment dynamics. The damping term controls the speed at which the instantaneous magnetic moment direction approaches the effective magnetic field direction through a damping coefficient α.

3. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 2, characterized in that: Obtain the dynamic equations for each magnetic domain unit, including: The dynamic behavior of each magnetic domain unit is described by the LLG equation; The magnetization intensity of each magnetic domain unit in the LLG equation is set to be constant and the magnetic moment direction is variable, thereby obtaining a dynamic equation for each magnetic domain unit; The dynamic equation of the magnetic domain unit includes the gyromagnetic ratio, the damping coefficient α and the effective magnetic field. H eff .

4. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 3, characterized in that: The effective magnetic field is calculated by superposing the following components: an external magnetizing magnetic field component, the direction of which is aligned with the easy magnetization axis of the permanent magnet to be magnetized; The exchange field component between adjacent magnetic domains is the interaction between adjacent magnetic domain units; The material anisotropy field component is determined by the structure of the permanent magnet to be magnetized; The demagnetization field component is calculated by multiplying the magnetization intensity by the demagnetization tensor.

5. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that: Solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation includes: Setting a time step Δt, and iteratively calculating the instantaneous magnetic moment direction according to the time step Δt; For each time step Δt, the Runge-Kutta method is used to solve the dynamic equations and update the instantaneous magnetic moment direction; The iterative calculation of the instantaneous magnetic moment direction is stopped until the three-dimensional model of the permanent magnet to be magnetized reaches magnetization saturation.

6. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that: The unmagnetized state of the permanent magnet to be magnetized is simulated in the following manner: Randomly assigning a magnetic moment direction to each magnetic domain unit, so that the magnetic moment directions of each magnetic domain unit are evenly distributed in a three-dimensional space; Among them, when not magnetized, the magnetic moment directions of each magnetic domain unit are different, cancel each other out and appear in a scattered state. The initial magnetization saturation when not magnetized is calculated by the average angle between the magnetic moment direction and the easy magnetization axis, and the angle range is 85° to 95°.

7. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that: For the permanent magnet to be magnetized, when the action time of the effective magnetic field is less than the target magnetization time and / or the intensity of the effective magnetic field is less than the target magnetic field intensity, the magnetic moment direction of the magnetic domain unit is not completely consistent with the effective magnetic field direction; and / or For the permanent magnet to be magnetized, when the action time of the effective magnetic field is less than the target magnetization time and / or the intensity of the effective magnetic field is less than the target magnetic field intensity, the magnetic moment direction of the magnetic domain unit is not completely reversed relative to the initial magnetic moment direction.

8. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that: The relationship between magnetization saturation and pulse magnetic field strength and pulse duration includes: When the pulse magnetic field intensity does not reach the target pulse magnetic field intensity, the magnetization saturation increases with the increase of the pulse magnetic field intensity and the pulse duration; Under the constant pulse magnetic field intensity, increasing the pulse duration can stabilize the magnetization saturation at a certain value rather than increasing it indefinitely; Under the target pulse magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be saturated magnetized; if the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturation magnetization.

9. A magnetizer, characterized in that: include: A magnetizing circuit, used for magnetizing the permanent magnet to be magnetized; A controller comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the permanent magnet magnetization control method based on magnetic domain dynamics according to any one of claims 1 to 8 is implemented.

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