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

Abstract

The invention provides a permanent magnet magnetizing control method based on magnetic domain dynamics and a magnetizer, and particularly relates to the technical field of permanent magnet magnetizing. Obtaining a three-dimensional model of the permanent magnet to be magnetized, and dividing the three-dimensional model into a plurality of magnetic domain units; obtaining a magnetic moment kinetic equation of each magnetic domain unit; magnetic moment directions of the magnetic domain units are randomly distributed when magnetizing is not carried out, the magnetic moments of the magnetic domains do spin precession under the action of an effective magnetic field, and the magnetic moment directions approach to the direction of the effective magnetic field; the magnetic moment direction of each magnetic domain unit at different moments is subjected to numerical solution, and the change track of the magnetic moment direction of the magnetic domain unit from the initial magnetic moment direction is determined according to the instantaneous magnetic moment direction of the magnetic domain unit at different moments; and determining the consistency degree of the magnetic moment direction of each magnetic domain unit according to the change track, and generating a relation graph of the magnetizing saturation, the pulse magnetic field intensity and the pulse duration. According to the method, the magnetizing precision and efficiency can be improved.

Description

Technical Field

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

[0002] Permanent magnet magnetization is an important process for magnetizing permanent magnetic materials. In related technologies, most start from macroscopic hysteresis models, such as the Jiles-Atherton model and the Preisach model. These models are difficult to incorporate the consideration of microscopic magnetic domain motion. They mainly calculate the hysteresis loop by given magnetic field intensity, lacking in-depth research on the magnetic domain motion and physical mechanism during the magnetization process. From the perspective of microscopic magnetic domains, although there are studies such as simplified magnetic domain models and six-magnetic-domain models, these models cannot accurately simulate the magnetic moment precession process of a single magnetic domain under the action of an external magnetic field, deviating from the actual physical process. Summary of the Invention

[0003] In order to solve the deficiencies of the prior art, the purpose of this 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, this application provides a permanent magnet magnetization control method based on magnetic domain dynamics, which includes: Obtain a three-dimensional model of the permanent magnet to be magnetized, divide the three-dimensional model into multiple cubic units, and each cubic unit serves as a magnetic domain unit; Obtain the dynamic equation of each magnetic domain unit; wherein, the dynamic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit; 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 the state with zero initial magnetization intensity. Under the action of the effective magnetic field, each magnetic domain unit undergoes spin precession, and the magnetic moment directions of each magnetic domain unit gradually approach the effective magnetic field direction; Based on the dynamic equation, solve the instantaneous magnetic moment direction of each magnetic domain unit at different times. For each magnetic domain unit, determine the 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; According to the change trajectories of the magnetic moment directions of each magnetic domain unit, determine the degree of consistency of the magnetic moment directions of the magnetic domain units, and generate a relationship map of the magnetization saturation degree, pulse magnetic field intensity, and pulse duration; 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.

[0005] In one embodiment, the kinetic equation is a spin precession equation that introduces 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.

[0006] In one embodiment, obtaining the kinetic equation of each magnetic domain unit includes: The dynamic behavior of each magnetic domain unit is described by the LLG equation; Setting the magnitude of the magnetization of each magnetic domain unit to be constant and the magnetic moment direction to be variable in the LLG equation to obtain the kinetic equation of each magnetic domain unit; Among them, the kinetic equation of the magnetic domain unit includes the gyromagnetic ratio, the damping coefficient α, and the effective magnetic field H eff 。

[0007] In one embodiment, the kinetic equation of the magnetic domain unit is: ; Among them, represents the instantaneous magnetic moment direction of the magnetic domain unit m i , represents the gyromagnetic ratio, α represents the damping coefficient, represents the effective magnetic field.

[0008] In one embodiment, the effective magnetic field is calculated by superimposing the following components: The external magnetizing magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized; The exchange interaction field component between adjacent magnetic domains, which is the interaction between adjacent magnetic domain units; The material anisotropy field component, which is determined by the structure of the permanent magnet to be magnetized; The demagnetizing field component, which is calculated by the product of the magnetization intensity and the demagnetization tensor.

[0009] In one embodiment, solving the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the kinetic equation includes: Setting the time step Δt and iteratively calculating the instantaneous magnetic moment direction according to the time step Δt; For each time step Δt, using the Runge-Kutta method to solve the kinetic equation and update the instantaneous magnetic moment direction; Until the three-dimensional model of the permanent magnet to be magnetized reaches the magnetization saturation, stop iteratively calculating the instantaneous magnetic moment direction.

[0010] In one embodiment, the unmagnetized state of the permanent magnet to be magnetized is simulated by the following method: Randomly assigning magnetic moment directions to each magnetic domain unit, and the magnetic moment directions of each magnetic domain unit are uniformly distributed in three-dimensional space; Among them, when not magnetized, the magnetic moment directions of each magnetic domain unit are different from each other and cancel each other out, presenting 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 from 85° to 95°.

[0011] 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 direction of the effective magnetic field; 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 flipped relative to the initial magnetic moment direction.

[0012] In one embodiment, the relationship between the magnetization saturation and the pulsed magnetic field intensity and the pulse duration includes: When the pulsed magnetic field intensity does not reach the target pulsed magnetic field intensity, as the pulsed magnetic field intensity and the pulse duration increase, the magnetization saturation increases accordingly; At a constant pulsed magnetic field intensity, increasing the pulse duration can make the magnetization saturation stable at a certain value instead of increasing infinitely; At the target pulsed magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be saturatedly magnetized. If the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturated magnetization.

[0013] In a second aspect, the present application also provides a magnetizer, which includes: A magnetization circuit for magnetizing the permanent magnet to be magnetized; A controller, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the permanent magnet magnetization control method based on magnetic domain dynamics in the first aspect.

[0014] 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 equations of each magnetic domain unit, and determines its initial magnetic moment direction to simulate the scattered state when not magnetized; based on the dynamic equations, the instantaneous magnetic moment directions of each magnetic domain unit at different times are solved to determine the change trajectory of the magnetic moment direction; according to the change trajectory of the magnetic moment direction, the degree of consistency of the magnetic moment direction is determined, and a relationship map of the magnetization saturation degree with the pulse magnetic field intensity and duration is generated, thereby providing accurate control parameters for the magnetizer to ensure the best magnetization effect of the permanent magnet. In this method, the pulse magnetic field intensity and pulse duration are incorporated into the influencing factors of the magnetization saturation degree, and the spatial distribution of the permanent magnet is also incorporated into the influencing factors of the magnetization saturation degree by dividing the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, thereby improving the accuracy and efficiency of magnetization. Description of the Drawings

[0015] Figure 1 It is a flowchart of the permanent magnet magnetization control method based on magnetic domain dynamics in an embodiment; Figure 2 It is a flowchart of obtaining the dynamic equations of each magnetic domain unit in an embodiment; Figure 3(a) and Figure 3(b) are respectively the unsaturated magnetization magnetic domain model and saturated magnetization magnetic domain model diagrams of the unit magnetic domain in an embodiment; Figure 4 It is a flowchart of solving the instantaneous magnetic moment directions of each magnetic domain unit at different times based on the dynamic equations in an embodiment; Figure 5 It is a magnet model diagram in the unmagnetized state in an embodiment; Figure 6 It is a magnet model diagram in the unsaturated magnetization state in an embodiment; Figure 7 It is a magnet model diagram in the saturated magnetization state in an embodiment; Figure 8 It is a schematic diagram of the influence of the magnetic field intensity and duration on the magnetization saturation degree in an embodiment; Figure 9 It is a schematic diagram of the influence of the magnetic field intensity and duration on the remanence in an embodiment; Figure 10 It is a circuit diagram of the magnetization circuit in an embodiment. Detailed Embodiments

[0016] To make the objectives, technical solutions and advantages of this application more clear and understandable, the following further elaborates on this application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not used to limit this application. Unless otherwise defined, the technical terms or scientific terms involved in this application should have the general meaning understood by those with ordinary skills in the technical field to which this application belongs.

[0017] In one embodiment, as Figure 1 shown, a permanent magnet magnetization control method based on magnetic domain dynamics is provided. The method includes the following steps: Step 101: Obtain a three-dimensional model of the permanent magnet to be magnetized, divide the three-dimensional model into multiple cubic units, and each cubic unit serves as a magnetic domain unit; 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, and each cubic unit can serve as an independent magnetic domain unit, whose size is determined according to the calculation accuracy. Conventionally, the unit volume is approximately 1 mm 3 , so as to accurately simulate the magnetization behavior of the magnetic domains. Among them, each magnetic domain unit has an independent magnetic moment vector, and its initial direction is determined by the generated random number to reflect the scattered distribution of the magnetic domain magnetic moments in the unmagnetized state.

[0018] Step 102: Obtain the dynamic equation of each magnetic domain unit; among them, the dynamic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit; For each magnetic domain unit, obtain the dynamic equation of each magnetic domain unit. Among them, 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.

[0019] It should be noted that the dynamic equation of the magnetic domain unit can consider the spin precession of the magnetic moment, the damping effect, and the influence of the external magnetic field on the magnetic moment direction. By solving the dynamic equation of the magnetic domain unit, the change of the magnetic moment vector direction of each magnetic domain unit over time can be obtained, so as to accurately simulate the magnetization process of the permanent magnet. The method for solving the dynamic equation of the magnetic domain unit is the fourth-order Runge-Kutta method to ensure the accuracy and stability of the calculation.

[0020] Step 103: Determine the initial magnetic moment direction of each magnetic domain unit; when unmagnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed to simulate the 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 directions of each magnetic domain unit gradually approach the direction of the effective magnetic field; When not magnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed and different from each other, canceling each other out. Its purpose is to simulate the state with an initial magnetization intensity of zero. Further, under the action of an effective magnetic field, each magnetic domain unit begins to perform spin precession, and the magnetic moment directions of each magnetic domain unit can gradually approach the direction of the effective magnetic field.

[0021] Specifically, initially, the magnetic moment vector direction of each magnetic domain unit is set by a random number generator to ensure that it has different orientations in three-dimensional space, thereby reflecting the scattered distribution of the magnetic moment in the non-magnetized state. When an effective magnetic field is applied, the magnetic moment vector of each magnetic domain unit can perform spin precession 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 approaches the direction of the effective magnetic field.

[0022] Step 104: Solve the instantaneous magnetic moment direction of each magnetic domain unit at different times based on the dynamic equation. For each magnetic domain unit, determine the 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; Specifically, initially, the magnetic moment direction of the magnetic domain unit is random, representing the scattered distribution of the magnetic moment in the non-magnetized state. With the application of an external effective magnetic field, the magnetic moment begins to change according to the law described by the dynamic equation, usually gradually tending from the initial random direction to the direction of the effective magnetic field.

[0023] Record the magnetic moment direction of each magnetic domain unit at each time step. The change trajectory of the magnetic moment direction of the magnetic domain unit over time can be plotted. The change trajectory of the magnetic moment direction of the magnetic domain unit starting 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 equation can be solved by numerical methods, such as the Runge-Kutta method, to obtain the instantaneous direction of the magnetic moment at each time step.

[0024] Step 105: Determine the degree of consistency of the magnetic moment directions of the magnetic domain units according to the change trajectories of the magnetic moment directions of the magnetic domain units, and generate a relationship map of the magnetization saturation degree, pulse magnetic field intensity, and pulse duration; among them, 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.

[0025] By analyzing the change trajectories of the magnetic moment directions of all magnetic domain units, calculate the degree of consistency between the magnetic moment directions of the magnetic domain units and the direction of the effective magnetic field under different pulse magnetic field intensities and durations, and then obtain the magnetization saturation degree. Among them, the magnetization saturation degree can reflect the magnetization degree of the permanent magnet under different magnetization conditions. The relationship map can use the pulse magnetic field intensity and pulse duration as the horizontal and vertical axes, and the magnetization saturation degree as a visual element such as color or height to intuitively display the relationship among the three.

[0026] Furthermore, 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, that is, according to the required magnetization saturation degree, find the corresponding pulsed magnetic field intensity and duration in the relationship map, so as to accurately control the magnetization process and ensure that the permanent magnet achieves the expected magnetization effect.

[0027] 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, solves the instantaneous magnetic moment direction of each magnetic domain unit at different times, and determines the change trajectory of the magnetic moment direction; determines the degree of consistency of the magnetic moment direction according to the change trajectory of the magnetic moment direction, generates a relationship map of magnetization saturation degree with pulsed magnetic field intensity and duration, and further provides accurate control parameters for the magnetizer to ensure that the permanent magnet achieves the best magnetization effect. In this method, the pulsed magnetic field intensity and pulse duration are incorporated into the influencing factors of magnetization saturation degree, and the spatial distribution of the permanent magnet is also incorporated into the influencing factors of magnetization saturation degree by dividing the three-dimensional model of the permanent magnet to be magnetized into multiple magnetic domain units, thereby improving the accuracy and efficiency of magnetization.

[0028] In one embodiment, the dynamic equation is a spin precession equation with a damping term introduced 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.

[0029] The dynamic equation can describe magnetic moment dynamics from a microscopic mechanism and can reflect the influence of magnetization magnetic field intensity, magnetic field duration, ferromagnetic materials, etc. on the change of magnetic moment direction.

[0030] In micromagnetics, the relationship between magnetization M and angular momentum L is: ; where γ is the gyromagnetic ratio, with a magnitude of , in the effective field H eff the torque T acting on the magnetization is: .

[0031] where μ 0 is the vacuum permeability, M is the magnetization, H eff is the effective field.

[0032] The effective field H eff is expressed as: .

[0033] Among them, μ s is the magnetic permeability, representing the response ability of the material to the magnetic field in a certain direction. is the Hamiltonian of the magnetic system, including the exchange energy, anisotropy energy, interaction energy, Zeeman energy, etc. of the magnetic system.

[0034] The expression of the Hamiltonian is: .

[0035] Among them, is the exchange energy of the magnetic system, is the anisotropy energy, is the interaction energy, is the external magnetic field energy.

[0036] According to the angular momentum theorem, .

[0037] Substitute the relationship between the magnetization intensity M and the angular momentum L and the expression of the magnetization intensity under torque into the angular momentum theorem, and we get: .

[0038] This equation can represent the precession form of the spin magnetization vector in the external magnetic field, but the damping dissipation is not considered. Starting from the Lagrangian equation, the damping term T D is: ; Among them, α is the damping constant, M S is the saturation magnetization intensity. Therefore, the magnetization dynamics equation considering damping dissipation is: .

[0039] Perform the M× operation on both sides, and we get:

[0040]

[0041] .

[0042] After arranging the formula, the magnetization dynamics equation is: .

[0043] Among them, unifying 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. In this embodiment, the damping term is introduced into the kinetic equation, and the damping coefficient α is used to control the speed at which the instantaneous magnetic moment direction approaches the effective magnetic field direction, enabling accurate simulation of the dynamic changes of the magnetic moment under the action of an external magnetic field and improving the accuracy and reliability of the magnetization simulation.

[0044] In one embodiment, as Figure 2 shown, obtaining the kinetic equation of each magnetic domain unit includes the following steps: Step 201: The dynamic behavior of each magnetic domain unit is described by the LLG equation; among them, the kinetic equation of the magnetic domain unit includes the gyromagnetic ratio, the damping coefficient α and the effective magnetic field H eff .

[0045] The dynamic behavior of each magnetic domain unit can be described by the LLG equation. The LLG equation combines 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 magnetic field.

[0046] Among them, the gyromagnetic ratio γ is a constant related to the material properties, which can reflect the precession speed of the magnetic moment under the action of a unit magnetic field, and its magnitude is 2.21×10 5 m / (As). The damping coefficient α can control the speed at which the magnetic moment direction approaches the effective magnetic field direction. A larger α value means that the magnetic moment direction changes faster and can align with the effective field direction more quickly, while a smaller α value indicates that the magnetic moment direction changes slower and the precession process lasts longer. The effective magnetic field H eff is the total magnetic field where the magnetic moment is located, which not only includes the externally applied magnetization magnetic field but may also include the anisotropy field, exchange field, etc. inside the material. H eff The direction and magnitude of

[0047] jointly determine the precession trajectory and the final stable direction of the magnetic moment.

[0048] Step 202: In the LLG equation, set the magnitude of the magnetization intensity of each magnetic domain unit to be constant and the magnetic moment direction to be variable to obtain the kinetic equation of each magnetic domain unit.

[0049] Exemplarily, assume that the magnitude of the magnetization of each magnetic domain unit remains unchanged, and the effective magnetic field only acts on its direction. Assume that the magnetization of each magnetic domain unit is 1, and the saturation magnetization is taken as the reference value, that is: .

[0050] where x, y, and z are the x-axis direction, y-axis direction, and z-axis direction in space, m i is the magnetization intensity vector of the i th magnetic domain unit after normalization.

[0051] In one embodiment, the dynamic equation of the magnetic domain unit is: ; where, represents the instantaneous magnetic moment direction of the magnetic domain unit m i ; represents the gyromagnetic ratio, and α represents the damping coefficient. H eff represents the effective magnetic field.

[0052] Specifically, m i is the normalized magnetization intensity vector of the i th magnetic domain unit, whose modulus length remains 1, and only the direction changes; γ is the gyromagnetic ratio, which is a constant related to the material properties and reflects the precession speed of the magnetic moment under the action of a unit magnetic field; H eff is the effective field, including the externally applied magnetic field and the anisotropy field, exchange field, etc. inside the material; α is the damping coefficient, which controls the rate of change of the magnetic moment direction.

[0053] 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 an external field without considering the change in the magnitude of the magnetization, so as to more efficiently analyze and predict the magnetization behavior of the permanent magnet.

[0054] In one embodiment, for the unit magnetic domain, m0 is the initial magnetic moment. Under the action of the effective field, the magnetic moment vector undergoes spin precession and gradually approaches the direction of the effective field. When the action time of the effective field is too short or the intensity is insufficient, according to the magnetic moment dynamics equation, the direction of the magnetic moment will not finally be completely consistent with the direction of the effective field, but will stop at a certain position in the precession motion, as shown in Fig. 3(a), which is the incomplete flipping of the magnetic domain and also the microscopic manifestation of incomplete magnetization. When the intensity and time of the effective field are sufficient, at the end of the action, the direction of the magnetic moment vector is basically consistent with the direction of the effective field, as shown in Fig. 3(b), the magnetic domain completes flipping, and the magnetic moment vector is consistent with the direction of the effective field.

[0055] In one embodiment, the effective magnetic field is calculated by superimposing the following components: The external magnetization magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized; The exchange interaction field component between adjacent magnetic domains, which is the interaction between adjacent magnetic domain units; The material anisotropy field component, which is determined by the structure of the permanent magnet to be magnetized; The demagnetizing field component, which is calculated by the product of the magnetization intensity and the demagnetization tensor.

[0056] In the modeling of the permanent magnet magnetization process, the effective magnetic field H eff is obtained by superimposing multiple components, and these components include: the external magnetization magnetic field component, the exchange interaction field component between adjacent magnetic domains, the material anisotropy field component, and the demagnetizing field component.

[0057] Among them, the external magnetization magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized, is the main driving force during the magnetization process and determines the basic orientation of the magnetic moment; the exchange interaction field component between adjacent magnetic domains results from the interaction between adjacent magnetic domain units, and 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, making the magnetic moment more stable in certain directions; the demagnetizing 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, and its magnitude and direction depend on the distribution of the magnetization intensity and the shape of the permanent magnet.

[0058] In this embodiment, through the combined action of these components, the dynamic behavior of the magnetic moment during the magnetization process and the final magnetization state are determined.

[0059] In one embodiment, as Figure 4 shown, based on the dynamics equation, solving the instantaneous magnetic moment direction of each magnetic domain unit at different times includes the following steps: Step 401: Set the time step Δt and iteratively calculate the instantaneous magnetic moment direction according to the time step Δt; Step 402: For each time step Δt, use the Runge-Kutta method to solve the dynamic equation and update the instantaneous magnetic moment direction. Set a time step Δt as the basic unit for time advancement in the calculation process. The magnitude of this time step Δt can be determined according to the required calculation accuracy and efficiency, usually in the order of nanoseconds to microseconds. If Δt is set, iterative calculations are performed according to this time step Δt to gradually obtain the instantaneous magnetic moment direction of each magnetic domain unit.

[0060] For each time step Δt, the Runge-Kutta method can be used to solve the dynamic equation and update the instantaneous magnetic moment direction. Among them, the Runge-Kutta method is a commonly used numerical method for solving ordinary differential equations. By calculating multiple intermediate slopes within each time step to estimate the value of the next time step, the accuracy of the solution is improved.

[0061] It should be noted that within each time step Δt, four stages of the Runge-Kutta method are used to calculate the change in the magnetic moment direction: calculate the slope k1 at the current time step, based on the current magnetic moment direction and the effective field; 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. Through the four calculated slopes, a more accurate magnetic moment direction update formula can be obtained, so as to accurately update the magnetic moment direction within each time step Δt.

[0062] Step 403: Stop the iterative calculation of the instantaneous magnetic moment direction until the three-dimensional model of the permanent magnet to be magnetized reaches the magnetization saturation.

[0063] Within each time step, the Runge-Kutta method is used to solve the dynamic equation and update the instantaneous magnetic moment direction. This process continues until the three-dimensional model of the permanent magnet to be magnetized reaches the magnetization saturation, that is, the magnetic moment directions of most magnetic domain units are 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. Exemplarily, the determination of magnetization saturation can be determined by calculating the deviation degree between the magnetic moment directions of all magnetic domain units and the effective field direction. When the deviation degree is less than a certain preset threshold, it is considered that the permanent magnet has reached the magnetization saturation state.

[0064] In this embodiment, by setting an appropriate time step Δt and using the Runge-Kutta method to solve the dynamic equation, the change of the magnetic moment direction with time can be accurately simulated, so as to accurately capture the dynamic behavior of the magnetic moment during the magnetization process; by judging the magnetization saturation to stop the iterative calculation, the computing resources can be effectively saved, unnecessary calculations can be avoided, and the simulation efficiency can be improved.

[0065] In one embodiment, the unmagnetized state of the permanent magnet to be magnetized is simulated by the following method: Randomly assign the magnetic moment directions to each magnetic domain unit, and the magnetic moment directions of each magnetic domain unit are uniformly distributed in three-dimensional space; Among them, when not magnetized, the magnetic moment directions of each magnetic domain unit are different from each other and cancel each other out, showing 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°.

[0066] In the initial stage of simulating the magnetization process of a permanent magnet, randomly assign the magnetic moment directions to each magnetic domain unit, and the magnetic moment directions of each magnetic domain unit are uniformly distributed in three-dimensional space. The purpose is that when not magnetized, the magnetic moment directions inside the permanent magnet are scattered, the magnetic moment directions of each magnetic domain unit are different from each other and cancel each other out, so that the permanent magnet as a whole does not show magnetism. The setting of this initial state conforms to the actual situation and can accurately reflect the physical properties of the non-magnetized permanent magnet.

[0067] 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 meaning of setting the angle range is that the easy magnetization axis is the direction in which the permanent magnet is most easily magnetized. In the non-magnetized state, the magnetic moment direction should be almost perpendicular to the easy magnetization axis to ensure a low initial magnetization saturation. Selecting the angle range of 85° to 95° can ensure that the magnetic moment direction is almost perpendicular to the easy magnetization axis initially, so that the initial magnetization saturation is close to zero, which conforms to the physical properties of the non-magnetized state.

[0068] 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 direction of the effective magnetic field; 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 does not completely flip relative to the initial magnetic moment direction.

[0069] The target magnetization time can refer to the shortest time set to achieve full magnetization of the permanent magnet, and the target magnetic field intensity refers to the minimum magnetic field intensity required to make the permanent magnet reach the saturation magnetization state.

[0070] 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 will not be completely consistent with the direction of the effective magnetic field, nor will it completely flip relative to the initial magnetic moment direction.

[0071] Specifically, if the action time of the effective magnetic field is insufficient, the magnetic moment does not have enough time to fully align with the direction of the effective field; and if the intensity of the effective magnetic field is insufficient, the magnetic moment cannot obtain enough energy to overcome obstacles such as anisotropy and demagnetizing field, and thus cannot complete a complete flipping process.

[0072] In this embodiment, both of these situations may cause the direction of the magnetic moment to stay in an intermediate state, neither fully aligning with the direction of the effective field nor fully returning to the initial direction, thus affecting the magnetization effect.

[0073] In one embodiment, the magnet model in the unmagnetized state is as Figure 5 shown. When unmagnetized, the magnetic moment vectors within each magnetic domain of the permanent magnet are different from each other and cancel each other out, presenting a scattered state. The magnet model in the unsaturated magnetization state is as Figure 6 shown. When the magnetic field intensity or the duration is insufficient, although precession flipping has occurred in each magnetic domain, it has not fully tended to the direction of the external magnetic field, that is, it is not saturated magnetized. The magnet model in the saturated magnetization state is as Figure 7 shown. When sufficient magnetic field intensity and sufficient duration are given, the permanent magnet is saturated magnetized, and most of the magnetic domains complete flipping and fully tend to the direction of the effective field.

[0074] In one embodiment, the relationship between the magnetization saturation and the pulsed magnetic field intensity and the pulse duration includes: When the pulsed magnetic field intensity does not reach the target pulsed magnetic field intensity, as the pulsed magnetic field intensity and the pulse duration increase, the magnetization saturation increases accordingly; Specifically, when the pulsed magnetic field intensity does not reach the target pulsed magnetic field intensity, as the pulsed magnetic field intensity and the pulse duration increase, the magnetization saturation increases accordingly. When the pulsed magnetic field intensity is low, the magnetic moment requires more pulse duration to overcome the internal resistance and gradually aligns with the magnetic field direction. As the pulsed magnetic field intensity increases, the magnetic moment is easier to align, and the increase in pulse duration provides more time for the magnetic moment 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 together promote the increase in magnetization saturation.

[0075] At a constant pulsed magnetic field intensity, increasing the pulse duration can make the magnetization saturation stabilize at a certain value instead of increasing infinitely; Specifically, at a constant pulsed magnetic field intensity, as the pulse duration increases, the direction of the magnetic moment gradually aligns with the magnetic field direction, and the magnetization saturation will gradually increase. 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 enhancing 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 prolongs, and finally reach a dynamic equilibrium, making the magnetization saturation tend to a stable value. Therefore, at a constant pulsed magnetic field intensity, increasing the pulse duration will make the magnetization saturation gradually tend to a stable value instead of increasing infinitely.

[0076] At the target pulsed magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be magnetized to saturation. If the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturation magnetization.

[0077] Specifically, when the magnetic field intensity is sufficient, the magnetic moment needs a certain amount of time to overcome the 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 unable to reach saturation magnetization. Therefore, only when the pulse duration reaches the target magnetization time can it ensure that the magnetic moment is fully aligned and saturation magnetization is achieved.

[0078] In one embodiment, as Figure 8 shown, this figure shows the relationship between the magnetization saturation and the magnetic field intensity at different pulse durations. Among them, the horizontal axis represents the magnetic field intensity (unit: A / m), the vertical axis represents the magnetization saturation, and the curves of different colors and symbols correspond to different pulse durations (from 1.ms to 6ms). When the applied magnetic field intensity is 600 kA / m, the maximum magnetic field intensity does not reach the saturation magnetization magnetic field intensity of the permanent magnet model. Even if the duration is long enough, the final magnetization saturation still remains at about 50%. When the applied magnetic field intensity increases to 800 kA / m, within the time range of 0 - 1.5 ms, the magnetization speed significantly accelerates. However, the magnetic field intensity still does not reach saturation magnetization. Although most of the magnetic domains have completed flipping, about 40% of the magnetic domains are still misaligned with the easy magnetization axis, resulting in a final saturation level of about 80%.

[0079] When the peak value of the magnetization magnetic field reaches 1000 kA / m, the permanent magnet reaches the saturation state, the magnetic domain units are basically completed flipping, and the magnetization speed significantly increases. After reaching saturation magnetization, with the further increase of the external magnetic field intensity, within the same duration, the magnetization saturation will increase to a certain extent.

[0080] In summary, the dynamic equation of the magnetic domain unit constructed based on the LLG equation can effectively reflect the influence of the magnetization magnetic field strength and duration on the magnetization effect. The relationship between the magnetic field strength and duration can be summarized as follows: when the saturation magnetization magnetic field strength is not reached, as the magnetic field strength and duration increase, the magnetization saturation increases accordingly. At a certain magnetic field strength, further increasing the duration will stabilize the magnetization saturation at a certain value rather than increasing indefinitely. Once the saturation magnetization intensity is reached, if the duration is sufficient, the sample can be saturated magnetized. However, if the duration is insufficient, saturation magnetization cannot be achieved.

[0081] In one embodiment, as Figure 9 shown, the figure shows the relationship between the remanence and the magnetic field strength at different pulse durations. Among them, the horizontal axis represents the magnetic field strength (unit: A / m), and the vertical axis represents the remanence (unit: mT). The curves of different colors and symbols correspond to different pulse durations (from 1.05 ms to 6.20 ms). It should be noted that the remanence refers to the magnetization intensity retained by the magnetic material after the external pulsed magnetic field is removed, and it is an important index to measure the magnetization ability of the magnetic material.

[0082] At low magnetic field strengths, the remanence increases rapidly with the increase of the magnetic field strength, and the curves of different durations vary greatly, indicating that the pulse duration has a significant influence on the remanence. At high magnetic field strengths, the remanence tends to saturate, the curves tend to flatten, and the curves of different durations tend to be consistent, indicating that when the magnetic field strength is high enough, the influence of the pulse duration on the remanence decreases. Therefore, the remanence is not only related to the magnetic field strength but also closely related to the pulse duration, especially in the low magnetic field strength region. When the magnetic field strength reaches the saturation value, further increasing the magnetic field strength or duration has little effect on the improvement of the remanence.

[0083] In one embodiment, during the magnetization process, the effective magnetic field strength is usually not constant but changes dynamically with time. This change may be due to the characteristics of the magnetization device, power supply fluctuations, or is deliberately designed to achieve a specific magnetization strategy. The influence 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 dynamic equation. For example, in the (LLG) equation, the effective magnetic field strength is set as a function of time, so as to more accurately describe the dynamic behavior of the magnetic moment under the action of the external magnetic field. In this way, the magnetization process can be optimized and the magnetization effect can be improved.

[0084] Based on the same concept, the present application also provides a magnetizer, which includes: A magnetization circuit, as Figure 10 shown, for magnetizing the permanent magnet to be magnetized; The 0 - 1000V DC power supply on the left side of the magnetization circuit is used to provide energy for the entire circuit. Through the switchK 1 and the current-limiting resistor R 1 (1 kΩ) can control the charging process of the circuit. Multiple capacitors ( C = 400 μF, U = 1800 V) are connected in parallel to form an energy storage capacitor for storing electrical energy. These capacitors accumulate energy during the charging process and then quickly release it during the discharging process, generating a pulsed current. The switch K 2 is used to control the start of the magnetization process. When the switch K 2 is closed, the capacitor bank discharges through the magnetization coil, generating a pulsed magnetic field. The diode DL plays a protective role to prevent the reverse flow of current during the discharging process, which may damage other components in the circuit. The magnetization coil is the core part of the circuit. Through experimental measurement, its inductance L = 106.65 mH, and the resistance R L = 0.63 Ω. 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 for grounding the circuit to ensure the safe and stable operation of the circuit.

[0085] The working principle of the magnetization circuit is that by closing the switch K 1, the power supply charges the capacitor bank, and the capacitor bank stores electrical energy. When the capacitor bank is charged to the required voltage, the switch K 1 is disconnected and the switch K 2 is closed. The capacitor bank quickly discharges through the magnetization coil, generating a pulsed magnetic field. This magnetic field acts on the permanent magnet to be magnetized, causing the direction of its magnetic moment to change, thus achieving the magnetization process. The various parameters in the circuit (such as the capacitance of the capacitor, the magnitude of the inductance, etc.) can be adjusted according to the required pulsed magnetic field strength and duration to meet different magnetization requirements.

[0086] A controller, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements a method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics.

[0087] The processor can dynamically adjust the magnetization parameters, such as the magnetic field strength and duration, according to the real-time data during the magnetization process and the preset control strategy to ensure that the permanent magnet can achieve the best magnetization effect.

[0088] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope recorded in this specification.

[0089] The above embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics, characterized in that, The method includes: Obtain a three-dimensional model of the permanent magnet to be magnetized, divide the three-dimensional model into a plurality of cubic units, and each cubic unit serves as a magnetic domain unit; Obtain the dynamic equation of each magnetic domain unit; wherein, the dynamic equation is used to calculate the instantaneous magnetic moment direction of the magnetic domain unit; Determine the initial magnetic moment direction of each magnetic domain unit; when unmagnetized, the magnetic moment directions of each magnetic domain unit are randomly distributed to simulate the state of zero initial magnetization intensity. Under the action of the effective magnetic field, each magnetic domain unit performs spin precession, and the magnetic moment directions of each magnetic domain unit gradually approach the direction of the effective magnetic field; Based on the dynamic equation, solve the instantaneous magnetic moment direction of each magnetic domain unit at different times. For each magnetic domain unit, determine the 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; According to the change trajectories of the magnetic moment directions of each magnetic domain unit, determine the degree of consistency of the magnetic moment directions of the magnetic domain units, and generate a relationship map of the magnetization saturation degree, pulse magnetic field intensity, and pulse duration; 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 method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 1, characterized in that, The dynamic equation is a spin precession equation based on the magnetic moment dynamics principle and introducing a damping term, 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.

3. The method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 2, characterized in that, Obtain the dynamic equation of each magnetic domain unit, including: The dynamic behavior of each magnetic domain unit is described by the LLG equation; In the LLG equation, set the magnetization intensity magnitude of each magnetic domain unit to be constant and the magnetic moment direction to be variable to obtain the dynamic equation of each magnetic domain unit; Among them, 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 method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 3, characterized in that, The dynamic equation of the magnetic domain unit is: ； Among them, represents the magnetic domain unit m i is the instantaneous magnetic moment direction of represents the gyromagnetic ratio, and α represents the damping coefficient. H eff represents the effective magnetic field.

5. The method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 3, characterized in that, The effective magnetic field is calculated by superimposing the following components: An external magnetization magnetic field component, whose direction is aligned with the easy magnetization axis of the permanent magnet to be magnetized; An exchange interaction field component between adjacent magnetic domains, which is the interaction between adjacent magnetic domain units; A material anisotropy field component, which is determined by the structure of the permanent magnet to be magnetized; A demagnetizing field component, which is calculated by the product of the magnetization intensity and the demagnetization tensor.

6. The method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 1, characterized in that, Based on the dynamic equation, solve the instantaneous magnetic moment direction of each magnetic domain unit at different times, including: Set a time step Δt, and iteratively calculate the instantaneous magnetic moment direction according to the time step Δt; For each time step Δt, use the Runge-Kutta method to solve the dynamic equation and update the instantaneous magnetic moment direction; Stop iteratively calculating the instantaneous magnetic moment direction until the three-dimensional model of the permanent magnet to be magnetized reaches the magnetization saturation degree.

7. The method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to claim 1, characterized in that, The unmagnetized state of the permanent magnet to be magnetized is simulated by the following method: Randomly assign magnetic moment directions to each magnetic domain unit, and the magnetic moment directions of each magnetic domain unit are uniformly distributed in three-dimensional space; Among them, when unmagnetized, the magnetic moment directions of each magnetic domain unit are different from each other and cancel each other out, showing a scattered state. The initial magnetization saturation degree when unmagnetized is calculated by the average angle between the magnetic moment direction and the easy magnetization axis, and the angle range is 85° to 95°.

8. The method for controlling the magnetization of a permanent magnet 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 directions of the magnetic domain units are not completely consistent with the direction of the effective magnetic field; 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 directions of the magnetic domain units are not completely flipped relative to the initial magnetic moment directions.

9. The permanent magnet magnetization control method based on magnetic domain dynamics according to claim 1, characterized in that, The relationship between the magnetization saturation degree and the pulse magnetic field intensity and the pulse duration includes: When the pulse magnetic field intensity does not reach the target pulse magnetic field intensity, as the pulse magnetic field intensity and the pulse duration increase, the magnetization saturation degree increases accordingly; At a constant pulse magnetic field intensity, increasing the pulse duration can make the magnetization saturation degree stable at a certain value instead of increasing infinitely; At the target pulse magnetic field intensity, if the pulse duration reaches the target magnetization time, the permanent magnet to be magnetized can be magnetized to saturation. If the pulse duration is less than the target magnetization time, the permanent magnet to be magnetized cannot reach saturation magnetization.

10. A magnetizer, characterized in that, including: A magnetization circuit for magnetizing the permanent magnet to be magnetized; A controller, the controller includes a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, it implements the method for controlling the magnetization of a permanent magnet based on magnetic domain dynamics according to any one of claims 1 to 9.

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