Permanent magnet linear motor composite magnetic slot wedge topology and design method thereof

Abstract

This invention relates to a composite magnetic slot wedge topology structure and its design method for permanent magnet linear motors. Addressing the problem of large fluctuations in cogging force and thrust caused by slotting in the primary core of a permanent magnet linear motor, the invention proposes placing a magnetic slot wedge at the primary slot opening to adjust the relative air gap permeability. To overcome the limitations of regular shapes, an improved finite element modeling method is employed. The preprocessed region is meshed, and a topological matrix is ​​generated using binary numbers for topological encoding. This topological matrix is ​​then mapped to a high-dimensional space for finite element solution. An intelligent optimization algorithm is used to perform global iterative optimization of the slot wedge parameters in different slots, minimizing the overall cogging force after synthesis. The obtained optimal slot wedge structure is then smoothed. This invention overcomes the geometric optimization limitations of traditional regular slot wedges, effectively weakening the cogging force caused by core slotting and suppressing fluctuations in cogging force and thrust of the permanent magnet linear motor.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet linear motor technology, specifically relating to a composite magnetic slot wedge topology structure for permanent magnet linear motors and its design method; in particular, it relates to a composite magnetic slot wedge structure design method based on topology optimization, used to suppress cogging force and thrust fluctuations in permanent magnet linear motors. Background Technology

[0002] Linear motors do not require an intermediate transmission structure, and compared with traditional rotary motors, they have a simpler structure and higher efficiency. Due to their advantages such as high thrust density, high response speed, low loss, and high precision, permanent magnet linear motors have gradually gained favor in the industry market and have been widely used in high-thrust performance applications such as high-speed logistics, rail transportation, and electromagnetic catapults, as well as in high-precision CNC equipment such as semiconductor processing machine tools and computer numerical control machine tools.

[0003] However, permanent magnet linear motors inevitably suffer from cogging force and thrust fluctuations during operation, which severely affects the motor's positioning accuracy and motion control performance, becoming one of the key technical bottlenecks restricting its application in high-precision servo drive fields. The thrust fluctuation of permanent magnet motors mainly consists of cogging force generated by the cogging effect, end force generated by the end effect, and ripple thrust caused by winding parameter asymmetry. Among these, the presence of cogging force causes significant thrust fluctuations during motor operation, thus affecting positioning accuracy, causing motor vibration and noise problems, and consequently limiting its dynamic performance and its widespread application in high-precision fields.

[0004] To mitigate the cogging effect caused by slotting in the motor core, current methods for suppressing cogging force in permanent magnet motors mainly fall into three categories: changing the pole-slot configuration, altering permanent magnet pole parameters, and optimizing the motor's slot structure. Regarding changing the pole-slot configuration, fractional-slot winding structures are more effective at reducing cogging force compared to integer-slot winding motors. Among these, the fractional-slot concentrated winding structure is the most widely used; however, this structure is heavily constrained by the combination of pole-slot numbers.

[0005] For example, patent CN201020690018.6, while altering the permanent magnet pole parameters effectively suppresses cogging force, increases the complexity of the pole processing due to changes in the permanent magnet structure, and may also reduce the motor's output thrust. Patent CN202310911468.5 optimizes the motor's cogging structure; while this method also effectively suppresses cogging force, methods such as skewed slots, non-uniformly distributed teeth, and unequal stator slot widths can significantly impact the available slot area and winding windings.

[0006] Magnetic slot wedges are an effective means of adjusting the air gap magnetic permeability distribution and weakening cogging forces by filling the slot opening with magnetically conductive material. However, traditional magnetic slot wedge designs often employ regular geometric shapes (such as rectangles and trapezoids). These regular shapes are difficult to precisely match the actual distribution of the air gap magnetic field, limiting the optimization space and making it difficult to achieve optimal cogging force suppression. Furthermore, existing magnetic slot wedge design methods largely rely on empirical trial and error or simple parameter scanning, lacking systematic optimization design methods and failing to fully explore the potential of slot wedge structural parameters for cogging force suppression. Summary of the Invention

[0007] To address the above issues, this invention provides a composite magnetic slot wedge topology for a permanent magnet linear motor and its design method. By employing topology optimization technology to optimize the layout of magnetic and non-magnetic materials in the slot region, precise control of the air gap magnetic permeability distribution is achieved, thereby effectively suppressing the cogging force and thrust fluctuations of the permanent magnet linear motor.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: (1) By analyzing the analytical expression of the cogging force of the permanent magnet linear motor, the main methods to reduce the cogging force are derived, including adjusting the air gap magnetic flux density of the permanent magnet and adjusting the relative air gap magnetic permeability.

[0009] Furthermore, the analytical expression for the cogging force of a permanent magnet linear motor is as follows: (1) In equation (1): z is the number of motor slots, p is the number of motor pole pairs, n is the integer that makes nz / 2p an integer; x is the relative displacement between the primary and secondary sides of the motor; L is the axial length of the motor; C is the actual primary length corresponding to 2π; δ is the air gap length of the motor; B r(nz / 2p) Remanence B of permanent magnet r The coefficients of the expansion of the nz / 2pth term; and G n It can be represented as (2) In equation (2): hm is the magnetization height of the permanent magnet; b0 is the width of the motor slot; wend is the width of the end magnetic block of the slot wedge; τ is the motor pole pitch.

[0010] From equation (1), we can see that B r(nz / 2p) and G n It has a significant impact on the cogging force. Therefore, measures to reduce the cogging force can be mainly divided into two categories: one is to adjust the air gap magnetic density of the permanent magnet, and the other is to adjust the relative air gap magnetic permeability.

[0011] (2) A composite magnetic slot wedge topology for permanent magnet linear motor is proposed. The composite magnetic slot wedge is set in the area near the slot opening of the primary iron core of permanent magnet linear motor. The toothed slot wedge structure is used to change the distribution of relative air gap magnetic permeability, adjust the relative air gap magnetic permeability of the unit motor, suppress the magnitude of cogging force, and weaken the magnetic reluctance change caused by slotting by adjusting the air gap magnetic field, thereby suppressing the cogging force and thrust fluctuation of permanent magnet linear motor.

[0012] The composite magnetic slot wedge adopts a segmented magnetic slot wedge structure, which is composed of magnetically conductive blocks and non-magnetically conductive connecting materials arranged alternately along the slot opening direction. The magnetically conductive blocks are in the shape of a regular rectangle. The magnetically conductive blocks are composed of materials such as silicon steel sheets or magnetically conductive powder, and the non-magnetically conductive connecting materials are composed of epoxy resin mixed with glass fiber. The non-magnetically conductive connecting materials are filled in the air gaps between the magnetically conductive blocks. By adjusting the specific parameters and duty cycle of each segment of magnetically conductive blocks, the cogging force waveform and phase are modulated, thereby reducing the cogging force during the operation of the permanent magnet linear motor.

[0013] (3) To overcome the limitations of a regular rectangular shape making it difficult to accurately match the air gap magnetic field distribution and the constraints of the optimization space, an improved finite element modeling method was introduced when designing the composite magnetic slot wedge. This modeling method includes: (3-1) While keeping the permanent magnet structure, winding arrangement, air gap length, primary main iron core and secondary structure unchanged, the area near the slot of the primary iron core is set as the composite magnetic slot wedge design area; the pre-processing area is divided into several square grids of the same shape and size, and each square grid contains four triangles of the same shape. (3-2) The finite element calculation domain is divided into a fixed mesh consisting of a square mesh of equal size and four triangular finite element elements inside it, so that the node numbering and element connection relationship remain unchanged under different relative displacement positions and different slot wedge topologies; the material of the permanent magnet linear motor is topologically encoded using binary numerical values ​​to construct a topology matrix; (3-3) Based on the geometric position and relative displacement of the motor, fill each finite element unit with the material properties of air, iron core, permanent magnet, winding and composite magnetic slot wedge. The material properties of the composite magnetic slot wedge design area are determined by the topology matrix. Different values ​​in the topology matrix correspond to the magnetic slot wedge material and the non-magnetic slot wedge material, respectively. The elements in each row vector of the topology matrix are arranged into different binary sequences according to the column number from low to high, and converted into corresponding decimal position operators. These are then mapped to a high-dimensional space for finite element solution to break through the geometric limitations of regular shapes. (3-4) By combining the intelligent random optimization algorithm with the objective function, global optimization is performed in the high-dimensional space to find the magnetic slot wedge structure that minimizes the fluctuation of the tooth cogging force.

[0014] Specifically, a two-dimensional vector magnetomotive force finite element equation is established based on node number, element connection relationship and material number. The nodal vector magnetomotive force is solved by the incomplete Cholesky decomposition conjugate gradient method and the Newton-Raphson nonlinear iterative method. Then the magnetic flux density distribution and the cogging force of the motor along the direction of motion are calculated. The cogging force waveform within one cogging force cycle is obtained by changing the relative displacement between the primary and secondary, and the peak value of the cogging force is extracted as an evaluation index.

[0015] The topology matrix of the composite magnetic slot wedge is updated using a discrete variable intelligent optimization algorithm, such as a genetic algorithm, simulated annealing algorithm, particle swarm optimization algorithm, or differential evolution algorithm, so that the distribution of local magnetic and non-magnetic materials at the slot opening gradually tends to the optimal level. Topologies that reduce cogging force fluctuations and meet manufacturability requirements are retained, while penalties are imposed on topologies that lead to increased cogging force or the appearance of isolated magnetic blocks, isolated holes, and abrupt boundary changes.

[0016] (4) The composite magnetic slot wedge is configured in an arbitrary shape, and magnetic slot wedges of the same shape are used at each slot opening; the structural parameters of the slot wedges of the same shape are used as optimization variables, and optimization is performed in combination with the objective function to obtain a unified slot wedge topology that can suppress the basic tooth cogging force.

[0017] (5) The composite magnetic slot wedge is configured in an arbitrary shape, and different shapes of magnetic slot wedges are used at each slot. The intelligent optimization algorithm is used to iteratively optimize the slot wedge parameters in different slots. Taking advantage of the different phases and amplitudes of the cogging force generated by each slot, the overall cogging force after synthesis is minimized.

[0018] (6) The optimized composite magnetic slot wedge topology is regularized and smoothed, and the finite element cogging force is rechecked. Thus, without changing the main structure of the motor, the cogging force amplitude of the permanent magnet linear motor is reduced by adjusting the local relative air gap magnetic permeability distribution of the slot. After obtaining the optimal magnetic slot wedge structure through topology optimization, the slot wedge structure is smoothed. The irregular stepped or sawtooth part of the magnetic slot wedge boundary is smoothed by using a circular arc curve to meet the actual industrial processing difficulty and installation space limitations.

[0019] The present invention also includes other components that enable its normal use, all of which are conventional means in the art. In addition, any devices or components not limited in the present invention adopt the prior art in the art.

[0020] The beneficial effects of this invention are as follows: To address the issue of large fluctuations in cogging force and thrust caused by slotting in the primary core of a permanent magnet linear motor, this invention proposes installing magnetic slot wedges at the primary slot openings to alter the relative air gap magnetic permeability distribution. Simultaneously, to overcome the limitations of regular shapes, an improved finite element modeling method is employed. The preprocessed region is meshed, and a topological matrix is ​​generated using binary digits for topological encoding. This topological matrix is ​​then mapped to a high-dimensional space for finite element solution. Based on this, an intelligent optimization algorithm is used to globally optimize the slot wedge parameters within different slot openings, minimizing the overall cogging force after synthesis. The obtained optimal slot wedge structure is then smoothed. This invention overcomes the geometric optimization limitations of traditional regular slot wedges, effectively reducing the cogging force caused by core slotting and suppressing fluctuations in cogging force and thrust of the permanent magnet linear motor.

[0021] This invention breaks the limitations of conventional segmented magnetic slot wedge geometry, granting composite magnetic slot wedges design freedom for arbitrary topological shapes while maintaining consistent slot wedge shapes across all slots in the motor. By using the structural parameters of the identical slot wedge shapes as optimization variables and combining them with an objective function for optimization, a unified slot wedge topology capable of suppressing basic cogging forces is obtained. This invention targets multi-slot structures in permanent magnet linear motors, where each primary slot is equipped with an arbitrary-shaped composite magnetic slot wedge with independent geometric parameters. By introducing an intelligent optimization algorithm to globally optimize the slot wedge structural parameters within each slot, and utilizing the unequal phase and amplitude of the cogging forces generated by each slot, the overall combined cogging force is minimized. Attached Figure Description

[0022] Figure 1 This is a flowchart of the design method for the composite magnetic slot wedge topology of the permanent magnet linear motor in this invention; Figure 2 This is a schematic diagram of the magnetic slot wedge installation in the segmented magnetic slot wedge permanent magnet linear motor tooth cogging force suppression method of the present invention; Figure 3 This is a schematic diagram showing the effect of different magnetic block sizes on the cogging force of the permanent magnet linear motor using the segmented magnetic slot wedge method for suppressing cogging force in the present invention. Figure 4 A schematic diagram of a magnetic slot wedge structure for a method of suppressing cogging force in a permanent magnet linear motor using an arbitrary-shaped magnetic slot wedge topology, provided by the present invention; Figure 5 This is a schematic diagram of the geometric reconstruction mechanism of a method for suppressing cogging force in a permanent magnet linear motor using an arbitrary-shaped magnetic slot wedge topology, provided by the present invention. Figure 6 A schematic diagram of a material model modeled using an improved finite element method, provided by the present invention; Figure 7 This invention provides a schematic diagram of a motor drive simulation modeled using an improved finite element method. Figure 8 This invention provides a slot wedge topology structure that utilizes magnetic slot wedges of arbitrary shapes with identical topological structures in each slot. Figure 9 This invention provides a slot wedge topology structure that utilizes the different topologies of magnetic slot wedges with arbitrary shapes in each slot. Figure 10 This invention provides a comparison diagram of the cogging forces of a permanent magnet linear motor utilizing an arbitrary-shaped magnetic slot wedge topology and the original motor. Detailed Implementation

[0023] The present invention will now be clearly described in conjunction with the accompanying drawings and specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art based on the embodiments of the present invention without inventive effort to obtain all other embodiments should be included within the scope of protection of the present invention.

[0024] Example 1 A permanent magnet synchronous linear motor (PMLSM) is a type of linear motion motor. Unlike traditional rotary motors, it is mainly suitable for applications requiring linear motion. However, during operation, the permanent magnet linear motor is affected by cogging force, which leads to a decrease in its operational stability. Therefore, it is necessary to determine the appropriate shape of the magnetic slot wedge for treatment in order to better suppress the cogging force.

[0025] like Figure 1 As shown, this embodiment of the present invention provides a design method for a composite magnetic slot wedge topology structure of a permanent magnet linear motor, the method comprising the following steps: Step 1: Analyze the analytical expression for the cogging force of the permanent magnet linear motor to derive the main methods for reducing the cogging force, including adjusting the air gap magnetic flux density of the permanent magnet and adjusting the relative air gap permeability. The analytical expression for the cogging force of the permanent magnet linear motor is as follows: (1) In equation (1): z is the number of motor slots, p is the number of motor pole pairs, n is the integer that makes nz / 2p an integer; x is the relative displacement between the primary and secondary sides of the motor; L is the axial length of the motor; C is the actual primary length corresponding to 2π; δ is the air gap length of the motor; B r(nz / 2p) Remanence B of permanent magnet r The coefficients of the expansion of the nz / 2pth term; and G n It can be represented as (2) In equation (2): hm is the magnetization height of the permanent magnet; b0 is the width of the motor slot; wend is the width of the end magnetic block of the slot wedge; τ is the motor pole pitch.

[0026] From equation (1), we can see that Br(nz / 2p) and G n It has a significant impact on the cogging force. Therefore, measures to reduce the cogging force can be mainly divided into two categories: one is to adjust the air gap magnetic density of the permanent magnet, and the other is to adjust the relative air gap magnetic permeability.

[0027] While altering the permanent magnet pole parameters effectively suppresses cogging forces, changes to the permanent magnet structure increase the complexity of the pole manufacturing process and may reduce the motor's output thrust. Regarding optimizing the motor's cogging structure, while methods such as skewed slots, non-uniformly distributed teeth, and unequal stator slot widths significantly impact the available slot area and winding winding configuration.

[0028] This invention addresses the issue by altering the relative air gap magnetic permeability to weaken cogging force, proposing a segmented magnetic slot wedge structure to adjust the relative air gap magnetic permeability of the unit motor. For example... Figure 2 As shown, the segmented magnetic slot wedge structure is composed of alternating magnetic blocks and non-magnetic connecting materials. The magnetic blocks are regular rectangular in shape and can be made of materials such as silicon steel sheets or magnetic powder. The non-magnetic connecting materials are made of epoxy resin or glass fiber. By adjusting the specific parameters and duty cycle of each segmented rectangular magnetic block, the cogging force during motor operation can be reduced.

[0029] Taking a two-section magnetic slot wedge structure as an example, the width w of the magnetic guide block at the motor end of the adjustment unit... end ,like Figure 3 Through analysis, within the range of 0~2 mm, as w end As the diameter increases, the cogging force of the unit motor gradually decreases, reaching a minimum value at around 1.5 mm; within the range of 6~8 mm, the cogging force of the unit motor also increases with w. end The force decreases with increasing velocity, and the cogging force also reaches a minimum value at around 7.5 mm, and w end The cogging force waveform in the range of 6~8 mm and w end The cogging force waveforms are out of phase in the range of 0 to 2 mm. Although adjusting the parameters of the magnetic block in the magnetic slot wedge can effectively suppress the cogging force of the unit motor, it cannot completely eliminate the cogging force.

[0030] While segmented magnetic slot wedges effectively reduce motor cogging forces, their design imposes constraints on their topology, limiting optimal topology design. Therefore, a composite magnetic slot wedge topology was constructed, such as... Figure 4 (a) is a composite magnetic slot wedge one. Figure 4 (b) is a composite magnetic slot wedge II, which broadens the optimization design of magnetic slot wedge topology.

[0031] Step 2, as follows Figure 5The geometric reconstruction mechanism of PMLSM magnetic slot wedges is elucidated. Breaking through the inherent boundaries of conventional topology design, this scheme allows for high freedom in the morphological distribution of magnetic slot wedges, enabling reconstruction into arbitrary shapes. To achieve this, the entire design region is divided into several square matrix grids, which serve as the minimum material filling carrier. In this system, the shaded state variable represents the magnetic material, while the blank state variable represents the epoxy resin material. Based on this discretization rule, the macroscopic physical structure can be accurately equivalent to a gridded topological matrix. Thus, the myriad variations in the shape of the magnetic slot wedge are essentially reduced to a process of free arrangement and combination of the shaded and blank states within a microscopic matrix.

[0032] This invention employs an improved finite element numerical modeling approach, which enhances the solution speed of the electromagnetic field by reducing the time spent on repeated mesh generation and equation reconstruction through regular mesh generation and improved moving body handling. Traditional finite element software uses an adaptive mesh generation method, determining the material first and then generating the mesh. This results in inconsistent mesh shapes and sizes, employing triangular meshes of different sizes and shapes depending on the solution region (mover, air gap, stator). Because traditional finite element software encapsulates its internal program, mesh size and shape cannot be manually controlled. Furthermore, each calculation requires re-meshing of the solution region when the model moves or deforms, and the results are always different.

[0033] In the process of improving the finite element model, it is necessary to set the material properties of the mesh to facilitate subsequent electromagnetic field calculations. A square mesh is used as the smallest unit for material filling, and each square mesh consists of four triangles of identical size and shape. To facilitate the subsequent electromagnetic field solution and topology optimization process, such as... Figure 6 As shown, after the grid is divided, each triangle and its three vertices are numbered. When setting the material properties of the square grid, different numbers such as "2", "3", "4", and "5" are used to distinguish the range of different materials. Among them, material number "3" represents ferromagnetic material, material number "4" represents permanent magnet material, "5" represents winding material, and "2" represents air.

[0034] The improved finite element model technique proposed in this invention simulates the motion trajectory of a linear motor's mover by varying the filling material of different mesh regions. While maintaining the unchanged mesh subdivision, it calculates the electromagnetic field after each displacement of the linear motor's mover by varying the material of different mesh regions. For example... Figure 7As shown in the schematic diagram of the motor drive simulation, by transforming the mesh material of the motor's moving part region to simulate the motor's trajectory at the corresponding time, there is no need to re-mesh the mesh during the motor's operation; only the mesh material at the same position coordinates needs to be changed. In summary, the improved finite element simulation model optimizes the solution process for the moving electromagnetic field because it does not require re-meshing of the solution region, significantly reducing the solution time compared to traditional finite element software.

[0035] Step 3, as follows Figure 8 As shown, in a permanent magnet linear motor, the composite magnetic slot wedge is configured in an arbitrary shape, and magnetic slot wedges of the same shape are used at each slot opening; the structural parameters of the slot wedges of the same shape are used as optimization variables, and optimization is performed in combination with the objective function to obtain a unified slot wedge topology that can suppress the basic cogging force.

[0036] Step 4, as follows Figure 9 As shown, in different slots of the permanent magnet linear motor, the composite magnetic slot wedge is configured in an arbitrary shape, and different shapes of magnetic slot wedges are used at each slot. The intelligent optimization algorithm is used to iteratively optimize the slot wedge parameters in different slots. Taking advantage of the different phases and amplitudes of the cogging forces generated by each slot, the overall cogging force after synthesis is minimized.

[0037] Example 2 Based on Example 1, the cogging force calculation method based on the finite element method includes the following sub-steps: An equivalent two-dimensional finite element model is established based on the actual dimensions of the motor to be optimized. The finite element calculation region and the composite magnetic slot wedge preprocessing region are determined according to the actual dimensions and structure of the motor. The preprocessing region is located near the primary core slot opening and is used to install or fill the composite magnetic slot wedge material. When determining the preprocessing region, the permanent magnet structure, winding arrangement, air gap length, primary core, and secondary structure of the motor remain unchanged; only the material distribution in the local area of ​​the slot opening is optimized. The finite element calculation region is divided into square meshes of consistent shape and size. Each square mesh consists of four identical triangular finite element elements, with the center point of the square mesh serving as the common node of the four triangular elements. This fixed meshing method maintains the mesh node and element connection relationships unchanged under different displacement positions and different slot wedge topologies of the motor, thus avoiding the repeated re-meshing of the mesh in traditional finite element software during motion and structural change calculations.

[0038] Material properties are filled into the square mesh. Based on the motor geometry and current displacement position, each mesh cell is assigned material properties such as air, iron core, permanent magnet, winding, or composite magnetic slot wedge. The material properties within the composite magnetic slot wedge design region are determined by the topology matrix; when the corresponding design cell in the topology matrix is ​​in a magnetically permeable state, the region is filled with magnetically permeable slot wedge material; when the corresponding design cell is in a non-magnetically permeable state, the region is filled with non-magnetically permeable connecting material or low-permeability materials such as air.

[0039] The four corner points and the center point of the square mesh are globally numbered, and the four triangular finite element elements within each square mesh are also numbered. Each triangular element consists of three nodes, and the node numbers are arranged counterclockwise. By establishing the correspondence between node numbers, element numbers, and material numbers, a mesh topology data structure for finite element calculations is formed.

[0040] Based on the established node numbers and element connection relationships, interpolation functions are established for each triangular element, and a finite element matrix equation is formed based on the magnetic field vector magnetomotive force equation. For the magnetic field calculation of a two-dimensional permanent magnet linear motor, the vector magnetomotive force is used as the variable to be solved. Combined with the permeability of different material regions, the equivalent magnetization of the permanent magnet, and the winding current source term, a global stiffness matrix and right-hand side terms are assembled. The incomplete Cholesky decomposition conjugate gradient method is used to solve the finite element matrix equation to obtain the vector magnetomotive force at all nodes. Due to the magnetic saturation characteristics of the motor core, the equivalent permeability of the core region is updated in real time according to the material magnetization curve during the finite element solution process. The Newton-Raphson method is used to iteratively solve the nonlinear magnetic field problem. In each nonlinear iteration, the permeability of the ferromagnetic material is updated according to the current magnetic field calculation result, the finite element matrix is ​​reassembled, and the nodal vector magnetomotive force is solved until the results of two adjacent iterations meet the convergence accuracy requirements.

[0041] The magnetic flux density distribution in each finite element element is calculated based on the obtained nodal vector magnetomotive force, and the electromagnetic force on the primary magnetic body of the motor is calculated using the nodal force method. By accumulating the electromagnetic forces on the primary core, the composite magnetic slot wedge, and the boundary nodes of their adjacent magnetic regions, the cogging force of the motor along the direction of motion at the current displacement position is obtained. By changing the relative displacement between the primary and secondary elements and repeating the magnetic field solution and nodal force calculation, the cogging force waveform within one cogging force cycle can be obtained.

[0042] Example 3 Based on Example 2, the composite magnetic slot wedge topology optimization method includes the following sub-steps: A topology optimization strategy suitable for discrete variables is selected and combined with the aforementioned fixed-mesh finite element positioning force calculation model. The topology optimization strategy can employ genetic algorithms, simulated annealing algorithms, particle swarm optimization algorithms, differential evolution algorithms, or other intelligent stochastic optimization algorithms. Each candidate solution corresponds to a set of composite magnetic slot wedge topology matrices. The finite element program automatically generates the slot wedge material distribution and calculates the positioning force evaluation index based on this topology matrix. A topology matrix composed of "0"s and "1"s is used to characterize the material distribution structure of the composite magnetic slot wedge. Each element in the matrix corresponds to a square design unit within the slot design area. When the matrix element is "1", the design unit is filled with magnetically conductive slot wedge material; when the matrix element is "0", the design unit is filled with non-magnetically conductive material. Through this topology matrix, the complex slot wedge structure can be transformed into a material distribution model that the finite element program can automatically recognize.

[0043] For permanent magnet linear motors with multiple slots, two optimization methods can be adopted: a unified slot wedge topology or a segmented independent slot wedge topology. A unified slot wedge topology means that all slots use the same composite magnetic slot wedge structure to facilitate processing and batch installation. A segmented independent slot wedge topology means that different slots use different composite magnetic slot wedge structures based on their spatial positions, utilizing the amplitude and phase differences of the local cogging force components in each slot to further reduce the overall cogging force of the motor.

[0044] The composite magnetic slot wedge topology matrix is ​​continuously updated using an intelligent optimization algorithm, gradually optimizing the distribution of magnetic and non-magnetic materials at different slot openings. During the optimization process, if a certain topology can reduce the peak-to-peak value of cogging force, weaken the main harmonic components, and meet the manufacturability requirements, the topology is retained and the search continues; if the topology leads to increased cogging force or the appearance of unmanufacturable isolated magnetic blocks, its fitness is reduced or a penalty term is added. After multiple iterations, a composite magnetic slot wedge topology that can effectively reduce the amplitude of cogging force in permanent magnet linear motors is obtained.

[0045] The optimized composite magnetic slot wedge topology is regularized and smoothed. This process includes removing isolated magnetically conductive units, filling isolated non-magnetically conductive holes, limiting abrupt changes in adjacent boundaries, ensuring the minimum connection width of the magnetically conductive material, and smoothing stepped boundaries with arcs or polygonal lines. The regularized slot wedge structure is then re-imported into a finite element program for cogging force verification to ensure it maintains good cogging force suppression even after meeting machining and installation requirements.

[0046] Through the above steps, this invention transforms the structural design problem of the composite magnetic slot wedge in a permanent magnet linear motor into a topology optimization problem of the local material distribution at the slot opening, and uses a fixed-mesh finite element cogging force calculation program to quickly evaluate each slot wedge topology. This method can reduce the overall cogging force fluctuation by adjusting the relative air gap magnetic permeability distribution at the slot opening without changing the main motor structure, winding arrangement, or permanent magnet structure, thereby improving the operational stability of the permanent magnet linear motor.

[0047] To visualize the effect of the proposed invention in suppressing alveolar force, such as Figure 10 A comparison of the cogging force of a permanent magnet linear motor based on a topology-optimized composite magnetic slot wedge structure design method with that of the original motor was conducted. The results showed that after adopting the composite magnetic slot wedge structure, the peak-to-peak value of the cogging force further decreased to 3.86 N, a reduction of 96.88% compared to the original motor. The harmonic spectrum of the cogging force indicates that the composite magnetic slot wedge structure can essentially reduce the amplitude of each harmonic of the motor cogging force to zero, demonstrating that the composite magnetic slot wedge structure can achieve a better suppression effect on the motor cogging force.

[0048] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite magnetic slot wedge topology structure for a permanent magnet linear motor, characterized in that: The composite magnetic slot wedge is set in the area near the slot opening of the primary iron core of the permanent magnet linear motor. The toothed slot wedge structure changes the distribution of relative air gap magnetic permeability, suppresses the magnitude of cogging force, and weakens the magnetic reluctance change caused by slotting by adjusting the air gap magnetic field, thereby suppressing the cogging force and thrust fluctuation of the permanent magnet linear motor.

2. The composite magnetic slot wedge topology of the permanent magnet linear motor according to claim 1, characterized in that: The composite magnetic slot wedge adopts a segmented magnetic slot wedge structure, which is composed of magnetically conductive blocks and non-magnetically conductive connecting materials arranged alternately along the slot opening direction. By adjusting the specific parameters and duty cycle of each segment of magnetically conductive blocks, the cogging force during the operation of the permanent magnet linear motor and the relative air gap magnetic permeability of the motor can be reduced.

3. The composite magnetic slot wedge topology of the permanent magnet linear motor according to claim 2, characterized in that: The magnetically conductive blocks are made of silicon steel sheets or magnetically conductive powder materials; the non-magnetically conductive connecting material is made of epoxy resin mixed with glass fiber, and is filled in the air gaps between the magnetically conductive blocks.

4. The composite magnetic slot wedge topology of the permanent magnet linear motor according to claim 3, characterized in that: The magnetic conductive block is a block structure of arbitrary shape, and each slot uses a magnetic wedge of the same or different shape.

5. A design method for a composite magnetic slot wedge topology structure for a permanent magnet linear motor based on any one of claims 1-4, characterized in that, Includes the following steps: S1. Based on the permanent magnet linear motor to be optimized, an improved finite element model is constructed to determine the design region of the composite magnetic slot wedge; and the region is divided into several identical square grids, with each square grid containing four congruent triangles; S2. Use binary values ​​to perform topological coding on the distribution of magnetic slot wedge material and non-magnetic slot wedge material in the permanent magnet linear motor, and construct a topological matrix. S3. Extract the row vectors of the topological matrix and combine them into different binary sequences according to the column order. Then, convert them into corresponding decimal values ​​and map them to a high-dimensional space. Use an intelligent stochastic optimization algorithm combined with the objective function to solve the problem in the high-dimensional space and obtain the optimization result. S4. After obtaining the optimal magnetic slot wedge structure through topology optimization, the boundary of the slot wedge structure is regularized and smoothed. The processed slot wedge structure is then re-imported into the finite element program for tooth cogging force verification to ensure that it still has a good tooth cogging force suppression effect while meeting the limitations of actual industrial processing difficulty and installation space.

6. The design method of the composite magnetic slot wedge topology structure of the permanent magnet linear motor according to claim 5, characterized in that: Step S1 is as follows: Based on the actual dimensions of the permanent magnet linear motor to be optimized, an equivalent two-dimensional finite element calculation model is established. Under the condition that the permanent magnet structure, winding arrangement, air gap length, primary main iron core and secondary structure remain unchanged, the area near the slot of the primary iron core is set as the composite magnetic slot wedge design area. The finite element calculation area is divided into a fixed mesh consisting of a square mesh of equal size and four triangular finite element elements inside it, so that the node number and element connection relationship remain unchanged under different relative displacement positions and different slot wedge topologies.

7. The design method of the composite magnetic slot wedge topology structure of the permanent magnet linear motor according to claim 5, characterized in that: Step S2 specifically involves filling each finite element unit with air, iron core, permanent magnet, winding, and composite magnetic slot wedge material properties based on the geometric position and relative displacement of the permanent magnet linear motor. The material properties within the composite magnetic slot wedge design area are determined by a topology matrix, and different values ​​in the topology matrix correspond to magnetically conductive slot wedge materials, non-magnetically conductive slot wedge materials, or low-permeability materials, respectively.

8. The design method of the composite magnetic slot wedge topology structure of the permanent magnet linear motor according to claim 5, characterized in that: Step S3 specifically includes: S31. A two-dimensional vector magnetomotive force finite element equation is established based on node number, element connection relationship and material number. The nodal vector magnetomotive force is solved by the incomplete Cholesky decomposition conjugate gradient method and the Newton-Raphson nonlinear iterative method. Then the magnetic flux density distribution and the cogging force of the permanent magnet linear motor along the motion direction are calculated. The cogging force waveform within one cogging force cycle is obtained by changing the relative displacement between the primary and secondary, and the peak value of the cogging force is extracted as the evaluation index. S32. The composite magnetic slot wedge topology matrix is ​​updated using genetic algorithm, simulated annealing algorithm, particle swarm algorithm, differential evolution algorithm or other discrete variable intelligent optimization algorithm to make the distribution of local magnetic and non-magnetic materials at the slot gradually approach the optimal. Topologies that reduce cogging force fluctuations and meet manufacturability requirements are retained, while topologies that cause increased cogging force or the appearance of isolated magnetic blocks, isolated holes and abrupt boundary changes are penalized.

9. The design method of the composite magnetic slot wedge topology structure of the permanent magnet linear motor according to any one of claims 5-8, characterized in that: When magnetic slot wedges of the same shape are used at each slot of the permanent magnet linear motor, the structural parameters of the slot wedges of the same shape are used as optimization variables and combined with the objective function to obtain a unified slot wedge topology that can suppress the basic cogging force.

10. The design method of the composite magnetic slot wedge topology structure of the permanent magnet linear motor according to any one of claims 5-8, characterized in that: When different shapes of magnetic slot wedges are used at each slot of the permanent magnet linear motor, an intelligent optimization algorithm is used to iteratively optimize the slot wedge parameters in different slots. By taking advantage of the different phases and amplitudes of the cogging forces generated by each slot, the overall cogging force after synthesis is minimized.

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