High-precision modal analysis method for motor assembly

Abstract

The invention discloses a high-precision modal analysis method for a motor assembly, and the method comprises the following steps: 1, building a finite element model of the motor assembly, and defining transverse isotropic material attributes for a silicon steel sheet laminated structure in the motor assembly; 2, based on the actual assembly relation of the motor assembly, a nonlinear connection relation is defined in the finite element model; 3, performing nonlinear static analysis on the finite element model to obtain global rigidity distribution of the motor assembly in a specific assembly state; through the implementation of the method, the problem of insufficient simulation precision caused by neglecting silicon steel sheet lamination anisotropy and assembly contact nonlinearity in a traditional method is systematically solved, so that the prediction accuracy of the inherent frequency and the modal shape of the motor assembly is remarkably improved, and a reliable basis is provided for structural resonance avoidance and optimization design; and meanwhile, the dependence on a physical test is reduced, and the research and development efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a high-precision modal analysis method for motor assemblies. Background Technology

[0002] Modal analysis is the foundation of structural dynamics analysis, providing the most basic inherent structural characteristics, namely natural frequencies and mode shapes, for many subsequent types of dynamic analysis. The essence of modal analysis is the process of solving a particular solution to the second-order differential equation of dynamics (the following equation), i.e. Essentially, it is a linear analysis. The internal connection type of the system is fixed or non-separated by default, and the stiffness is calculated by penalty function in the normal and tangential directions of the contact surface, respectively.

[0003]

[0004] Even if a nonlinear model is set in the materials module and a nonlinear contact is set in the contact module, the actual analysis will still be performed linearly, assuming the initial model state is equivalent to a linear state. The numerical simulation process ignores the objectively existing nonlinear effects. Frictional contact is a typical example of nonlinear contact. During the friction process, changes in frictional force directly affect the contact stiffness of the system, resulting in significant changes in the structure's natural frequency.

[0005] Furthermore, since both the stator and rotor cores of the motor are laminated silicon steel sheets, their axial and cross-sectional material properties (elastic modulus, Poisson's ratio, shear modulus) cannot be consistent and are difficult to obtain through simple material tests. Currently, the feasible approach is to conduct hammer impact tests on the core specimens, calibrate the material properties of the laminated silicon steel sheet structure based on the test results, determine the most suitable parameters, and then conduct subsequent simulation analysis. This method has a long iteration cycle and is costly. Therefore, a series of equivalent processing methods exist in the industry, such as: treating the laminated silicon steel sheet structure as an isotropic material for modeling and analysis; treating all contacts inside the motor system as linear fixed connections and setting global common nodes to share the topology; equivalencing the stator core, windings, rotor core, and permanent magnets to varying degrees, suppressing some entities from mesh modeling, and simulating by establishing coupling points with mass, center of gravity, and moment of inertia properties, etc. The above simplification methods are valuable for reference in terms of mode shapes and modal frequencies on the cross-section, but they ignore the large error in axial modal frequencies.

[0006] In summary, a high-precision modal analysis method for motor assemblies is needed to address the shortcomings of existing technologies. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a high-precision modal analysis method for motor assemblies, aiming to solve the aforementioned problems.

[0008] This application provides a high-precision modal analysis method for motor assemblies, including the following steps:

[0009] Step 1: Establish a finite element model of the motor assembly and define transversely isotropic material properties for the silicon steel sheet laminate structure in the motor assembly;

[0010] Step 2: Based on the actual assembly relationship of the motor assembly, define nonlinear connection relationships in the finite element model;

[0011] Step 3: Perform nonlinear static analysis on the finite element model to obtain the global stiffness distribution of the motor assembly under a specific assembly state;

[0012] Step 4: Using the global stiffness distribution as input, perform dynamic modal analysis of the motor assembly to obtain the natural frequencies and mode shapes under this stiffness distribution. By integrating the definition of transversely isotropic materials and nonlinear connection relationships, and innovatively transferring the global stiffness distribution from nonlinear static analysis to modal analysis, the system systematically solves the problem of insufficient simulation accuracy caused by neglecting the anisotropy of silicon steel sheet stacking and assembly contact nonlinearity in traditional methods. This significantly improves the prediction accuracy of the motor assembly's natural frequencies and mode shapes, providing a reliable basis for structural resonance avoidance and optimization design, while reducing reliance on physical experiments and improving R&D efficiency.

[0013] Furthermore, in step 1, establishing the finite element model of the motor assembly includes:

[0014] The stator windings are geometrically simplified to remove small features;

[0015] An equivalent model is performed on the silicon steel sheet stacked structure of the stator core and rotor core.

[0016] Furthermore, in step 1, the definition of transversely isotropic material properties is based on a preset global coordinate system, which takes the rotation center of the motor rotating component as the origin, the rotation plane as the XY plane, and the motor axis as the Z axis.

[0017] Furthermore, the parameters required to define the transversely isotropic material properties include: silicon steel sheet density (ρ), elastic modulus in the X direction (E). X ), elastic modulus in the Y direction (E) Y ), Z-direction elastic modulus (E) Z Poisson's ratio in the XY plane (ν) X-Y Poisson's ratio in the XZ plane (ν) X-Z ), YZ plane Poisson ratio (ν) Y-Z ), XY plane shear modulus (G X-YXZ plane shear modulus (G) X-Z ), YZ plane shear modulus (G Y-Z ), where E X =E Y ,ν X-Z =ν Y-Z G X-Z = G Y-Z , .

[0018] Furthermore, in step 2, the nonlinear connection relationship includes the frictional contact between the motor housing and the stator core, and the frictional contact between the shaft and the rotor laminations, and the interference fit is set according to the actual assembly.

[0019] Furthermore, in step 2, the contact control of the nonlinear connection relationship adopts a multi-point constraint algorithm, and a spring unit is set at the motor bearing position to equivalently measure the bearing stiffness.

[0020] Furthermore, in step 3, nonlinear static analysis is used to calculate the contact stress and friction stress distribution of the motor assembly under assembly preload.

[0021] Furthermore, in step 3, the specific assembly state is the peak moment, trough moment, or final stabilization moment of the stress state during the nonlinear static analysis process.

[0022] Furthermore, in step 1, the grid division of the stator core, stator winding, rotor core, permanent magnet, balance plate, and rotor pressure ring adopts second-order hexahedral elements, and the grid division of the motor housing, end cover, and motor shaft adopts second-order tetrahedral elements.

[0023] Furthermore, in step 4, the dynamic modal analysis is a constrained modal analysis, used to obtain the resonant frequency and mode shape of the motor assembly.

[0024] The substantial effects of this invention:

[0025] 1. In this invention, by defining the transversely isotropic material properties of the silicon steel sheet laminate structure and defining nonlinear connections based on the actual assembly relationship, the errors caused by treating silicon steel sheets as isotropic materials or ignoring nonlinear contacts in traditional methods are effectively solved. The global stiffness distribution of the motor assembly under a specific assembly state is obtained through nonlinear static analysis and transferred to the dynamic modal analysis, so that the natural frequencies and mode shapes obtained by simulation are closer to the actual modal test results.

[0026] 2. In this invention, by considering the changes in the system stiffness distribution, the method can capture the stiffness characteristics under different assembly states, thereby providing a reliable basis for accurate frequency shifting of structural resonance and avoiding resonance risks in the later stage, which is beneficial to the lightweight, durability and NVH optimization design of the motor assembly.

[0027] 3. In this invention, by fully leveraging the technical advantages of simulation analysis, high-precision finite element modeling and nonlinear analysis are used to avoid physical experiments and iterative processes, greatly shortening the design and testing cycle, reducing R&D costs, and ensuring the reliability of the results. This invention is suitable for the rapid development and verification of drive motors for new energy vehicles.

[0028] 4. In this invention, the engineering analysis needs of complex motor assemblies are met by simplifying the geometric model, using mesh generation strategies, and defining nonlinear connections. This method can be applied to stiffness monitoring under different assembly states and operating conditions, providing a universal and efficient solution for evaluating the dynamic characteristics of motor assemblies. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the technical route of the present invention.

[0031] Figure 2 This is a finite element model diagram of the motor assembly of the present invention.

[0032] Figure 3 This is a finite element model diagram of the motor stator assembly of the present invention.

[0033] Figure 4 This is a finite element model diagram of the motor rotor assembly of the present invention.

[0034] Figure 5 This is a schematic diagram of the global coordinates of the present invention. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected to" another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this specification are for illustrative purposes only.

[0036] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0037] Example 1:

[0038] Reference Figure 1 As shown, a high-precision modal analysis method for an electric motor assembly includes the following steps:

[0039] Step 1: Establish the finite element model of the motor assembly and define the transversely isotropic material properties of the silicon steel sheet laminate structure in the motor assembly;

[0040] Step 2: Based on the actual assembly relationship of the motor assembly, define nonlinear connection relationships in the finite element model;

[0041] Step 3: Perform nonlinear static analysis on the finite element model to obtain the global stiffness distribution of the motor assembly under a specific assembly state;

[0042] Step 4: Using the global stiffness distribution as input, perform dynamic modal analysis of the motor assembly to obtain the natural frequencies and mode shapes under this stiffness distribution. This embodiment integrates the definition of transversely isotropic materials and nonlinear connection relationships, and innovatively transfers the global stiffness distribution from nonlinear static analysis to modal analysis. It systematically solves the problem of insufficient simulation accuracy caused by neglecting the anisotropy of silicon steel sheet stacking and assembly contact nonlinearity in traditional methods. This significantly improves the prediction accuracy of the motor assembly's natural frequencies and mode shapes, providing a reliable basis for structural resonance avoidance and optimization design, while reducing reliance on physical experiments and improving R&D efficiency.

[0043] Example 2:

[0044] Reference Figures 1-5 As shown, this embodiment is basically the same as embodiment 1, except that it provides a high-precision modal analysis method for a motor assembly, including the following steps:

[0045] Step 1: Establish the finite element model of the motor assembly and define transversely isotropic material properties for the silicon steel sheet laminate structure in the motor assembly; establishing the finite element model of the motor assembly includes:

[0046] The stator windings are geometrically simplified to remove small features;

[0047] The silicon steel sheet laminate structure of the stator core and rotor core is modeled equivalently, rather than modeled according to the actual laminate morphology.

[0048] The definition of transversely isotropic material properties is based on a preset global coordinate system, with the rotation center of the rotating motor component as the origin, the rotation plane as the XY plane, and the motor axis as the Z-axis.

[0049] The parameters required to define the transversely isotropic material properties include: silicon steel sheet density (ρ), elastic modulus in the X direction (E). X ), elastic modulus in the Y direction (E) Y ), Z-direction elastic modulus (E) Z Poisson's ratio in the XY plane (ν) X-Y Poisson's ratio in the XZ plane (ν) X-Z ), YZ plane Poisson ratio (ν) Y-Z ), XY plane shear modulus (G X-Y XZ plane shear modulus (G) X-Z ), YZ plane shear modulus (G Y-Z ), where E X =E Y ,ν X-Z =ν Y-Z G X-Z = G Y-Z , ;

[0050] Step 2: Based on the actual assembly relationship of the motor assembly, define nonlinear connection relationships in the finite element model;

[0051] Nonlinear connection relationships include frictional contact between the motor housing and the stator core, and frictional contact between the shaft and the rotor laminations, with interference fits set according to actual assembly.

[0052] The contact control of nonlinear connection relationship adopts a multi-point constraint algorithm, and spring units are set at the motor bearing position to equivalently measure the bearing stiffness;

[0053] Step 3: Perform nonlinear static analysis on the finite element model to obtain the global stiffness distribution of the motor assembly under a specific assembly state;

[0054] Nonlinear static analysis is used to calculate the contact stress and frictional stress distribution of the motor assembly under assembly preload;

[0055] A specific assembly state is usually the peak moment, trough moment or final stabilization moment of the stress state during nonlinear static analysis.

[0056] Step 4: Using the global stiffness distribution as input, perform dynamic modal analysis of the motor assembly to obtain the natural frequencies and mode shapes under this stiffness distribution.

[0057] In one implementation, in step 1, the grid division of the stator core, stator winding, rotor core, permanent magnet, balance plate, and rotor pressure ring adopts second-order hexahedral elements, and the grid division of the motor housing, end cover, and motor shaft adopts second-order tetrahedral elements.

[0058] In one implementation, step 4 involves constrained modal analysis of the dynamics, used to obtain the resonant frequency and mode shape of the motor assembly.

[0059] Example 3:

[0060] This embodiment is basically the same as Embodiment 1, except that it provides a modal analysis method for a new energy vehicle drive motor assembly. The specific steps are as follows:

[0061] Geometric model processing: The stator winding is appropriately simplified and some small features are removed; the stator core and rotor core structures are treated as equivalent and are not modeled according to the actual silicon steel sheet shape.

[0062] Establish a finite element mesh model: The stator core, stator winding, rotor core, permanent magnet, balance plate, and rotor pressure ring mesh models are divided according to second-order hexahedral meshes, while the remaining components are divided according to second-order tetrahedral meshes.

[0063] Define the coordinate system: with the center of rotation of the motor's rotating parts as the origin, the direction of rotation as the XY plane, and the motor's axial direction as the Z-axis.

[0064] Define the material properties involved in the motor assembly. The components include: motor housing, front and rear end covers, stator windings, permanent magnets, balance plates, rotor pressure rings, and motor shaft. The material parameters include: density, elastic modulus, and Poisson's ratio.

[0065] Define a transversely isotropic material model for silicon steel sheets: Based on the S3 coordinate system, the following need to be defined: density (ρ) and elastic modulus (E in the X direction) of the silicon steel sheet. X , Y direction E Y Z direction E Z Poisson's ratio (in the XY plane) X-Y XZ plane ν X-Z YZ plane ν Y-Z ), shear modulus (G in the XY plane) X-Y XZ plane G X-Z YZ plane G Y-Z ), where E X =E Y ,ν X-Z =ν Y-Z G X-Z = G Y-Z , .

[0066] Finite element model connection method definition: The nonlinear connection relationship of the motor assembly is defined according to the actual assembly of the motor, and the contact control adopts a multi-point constraint algorithm; the motor housing and stator core, and the shaft and rotor lamination are all in frictional contact and the interference is set according to the actual situation; the equivalent spring stiffness is set at the bearing position.

[0067] The nonlinear assembly state of the motor assembly is calculated using a nonlinear statics analysis module.

[0068] The contact stress and friction stress curves of the motor assembly under nonlinear assembly conditions are obtained. In this embodiment, the stiffness distribution state of the motor assembly at the last moment is selected, and the critical stiffness state is transferred to the modal analysis module.

[0069] The constrained modes of the motor assembly are calculated to obtain the resonant frequency results of the motor assembly. In this embodiment, the first-order bending resonant frequency, the second-order bending resonant frequency, and the torsional resonant frequency of the rotor are taken as examples:

[0070] The first-order bending resonance frequency of the rotor is 4331.7 Hz.

[0071] The rotor's second-order bending resonance frequency is 5991.6 Hz.

[0072] Rotor torsional resonance frequency: 7450.9Hz;

[0073] Based on traditional simulation methods: the silicon steel sheet stacking effect is ignored, and isotropic materials are used to construct the material model; the influence of nonlinear contact is ignored, and the internal structure of the motor assembly is linearly fixed, neglecting the effect of stiffness variations. Modal analysis is performed on the drive motor assembly, with all other settings unchanged. Taking the rotor's first-order bending resonance frequency, second-order bending resonance frequency, and torsional resonance frequency as examples, the results are as follows:

[0074] The first-order bending resonance frequency of the rotor is 4477.5 Hz.

[0075] Rotor second-order bending resonance frequency: 6287.5Hz;

[0076] Rotor torsional resonance frequency: 7832.5Hz;

[0077] This comparison demonstrates that the modal results of the drive motor assembly can be significantly corrected using the technical method of this invention, resulting in higher accuracy in simulation analysis and making it more conducive to accurately predicting the resonant frequency of the motor assembly. Taking the above data as an example, the simulation error can be corrected by up to 4.87%, which is more beneficial for accurate frequency shifting of structural resonance and optimization of structural design in the later stages, greatly shortening the design and testing cycle and reducing R&D costs.

[0078] It should be noted that while the preferred embodiments of the present invention are provided in the specification and accompanying drawings, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A high-precision modal analysis method for an electric motor assembly, characterized in that, Includes the following steps: Step 1: Establish a finite element model of the motor assembly and define transversely isotropic material properties for the silicon steel sheet laminate structure in the motor assembly; Step 2: Based on the actual assembly relationship of the motor assembly, define nonlinear connection relationships in the finite element model; Step 3: Perform nonlinear static analysis on the finite element model to obtain the global stiffness distribution of the motor assembly under a specific assembly state; Step 4: Using the global stiffness distribution as input, perform dynamic modal analysis of the motor assembly to obtain the natural frequencies and mode shapes under the stiffness distribution.

2. The high-precision modal analysis method for a motor assembly according to claim 1, characterized in that, In step 1, establishing the finite element model of the motor assembly includes: The stator windings are geometrically simplified to remove small features; An equivalent model is performed on the silicon steel sheet stacked structure of the stator core and rotor core.

3. The high-precision modal analysis method for a motor assembly according to claim 2, characterized in that, In step 1, the definition of transversely isotropic material properties is based on a preset global coordinate system, which takes the rotation center of the motor rotating component as the origin, the rotation plane as the XY plane, and the motor axis as the Z axis.

4. The high-precision modal analysis method for a motor assembly according to claim 3, characterized in that, The parameters required to define transversely isotropic material properties include: silicon steel sheet density (ρ), and elastic modulus in the X direction (E). X ), elastic modulus in the Y direction (E) Y ), Z-direction elastic modulus (E) Z Poisson's ratio in the XY plane (ν) X-Y Poisson's ratio in the XZ plane (ν) X-Z ), YZ plane Poisson ratio (ν) Y-Z ), XY plane shear modulus (G X-Y XZ plane shear modulus (G) X-Z ), YZ plane shear modulus (G Y-Z ), where E X =E Y ,ν X-Z =ν Y-Z G X-Z = G Y-Z , .

5. The high-precision modal analysis method for a motor assembly according to claim 1, characterized in that, In step 2, the nonlinear connection relationship includes the frictional contact between the motor housing and the stator core, and the frictional contact between the shaft and the rotor laminations, and the interference fit is set according to the actual assembly.

6. The high-precision modal analysis method for a motor assembly according to claim 5, characterized in that, In step 2, the contact control of the nonlinear connection relationship adopts a multi-point constraint algorithm, and a spring unit is set at the motor bearing position to equivalently measure the bearing stiffness.

7. The high-precision modal analysis method for a motor assembly according to claim 1, characterized in that, In step 3, nonlinear static analysis is used to calculate the contact stress and friction stress distribution of the motor assembly under assembly preload.

8. The high-precision modal analysis method for a motor assembly according to claim 7, characterized in that, In step 3, the specific assembly state is the peak moment, trough moment, or final stabilization moment of the stress state during the nonlinear static analysis process.

9. The high-precision modal analysis method for a motor assembly according to claim 8, characterized in that, In step 1, the grid division of the stator core, stator winding, rotor core, permanent magnet, balance plate, and rotor pressure ring adopts second-order hexahedral elements, and the grid division of the motor housing, end cover, and motor shaft adopts second-order tetrahedral elements.

10. The high-precision modal analysis method for a motor assembly according to claim 1, characterized in that, In step 4, the dynamic modal analysis is a constrained modal analysis, used to obtain the resonant frequency and mode shape of the motor assembly.

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