Search

CN-121997649-A - Modeling method for permanent magnet motor rotor dynamics model

CN121997649ACN 121997649 ACN121997649 ACN 121997649ACN-121997649-A

Abstract

The invention discloses a modeling method of a permanent magnet motor rotor dynamics model, which provides a modeling method and a unified modeling flow for the integrity of a permanent magnet motor rotor system with a complex topological structure, and effectively solves the problem that the rigidity of a complex multi-component assembly is difficult to accurately represent by calibrating a rotating shaft parameter and acquiring an iron core equivalent parameter, thereby improving the prediction reliability of the model on the rotor modal characteristics. In addition, the method adopts a mode of combining finite elements and analysis, simultaneously considers bending deflection and shearing deflection under the four-point bending boundary condition, reconstructs bending stiffness parameters finally used for modeling through an equivalent mass diameter method, characterizes the reinforcing effect of the iron core lamination assembly on the rigidity of the rotating shaft, avoids the problem that the full-size entity is difficult to calculate in contact with the finite element model, and has the advantages of small calculation amount and high accuracy.

Inventors

  • Shi Cenmei
  • LV SHILONG
  • CAO YANFEI
  • SHI TINGNA

Assignees

  • 浙江大学
  • 浙江大学先进电气装备创新中心

Dates

Publication Date
20260508
Application Date
20260119

Claims (8)

  1. 1. The modeling method of the permanent magnet motor rotor dynamics model is characterized by comprising the following steps of: (1) The method comprises the steps of dispersing a permanent magnet motor rotor into a plurality of nodes and shaft sections positioned between adjacent nodes along the axial direction, and establishing a Riccati transmission matrix model; (2) Constructing a plurality of groups of discrete local finite element models with different lamination numbers aiming at a rotor core lamination assembly, applying four-point bending loading boundary conditions to each group of discrete local finite element models, extracting the mid-span total deflection of the models in a pure bending section, dividing the mid-span total deflection into a bending deformation component and a shearing deformation component by using a Timoshenko beam theory, establishing a deflection-stiffness inverse calculation relation, and calculating to obtain the equivalent bending stiffness under the corresponding lamination number; (3) The method comprises the steps of establishing a power function attenuation relation of equivalent bending stiffness along with the change of the number of laminations, determining the equivalent elastic modulus of a rotor core lamination assembly under the actual number of laminations through fitting extrapolation calculation, endowing the equivalent elastic modulus to a corresponding shaft section of a rotor core to characterize the stiffness reinforcing effect of the shaft section, constructing a complete rotor system Riccati transfer matrix model containing the lamination core stiffness characteristic by combining the optimal shear correction coefficient, and solving the modal characteristic of the rotor system.
  2. 2. The modeling method of the rotor dynamics model of the permanent magnet motor according to claim 1, wherein in the step (1), the shearing correction coefficient of each shaft section in the Riccati transfer matrix model is calibrated and optimized, and the method is specifically implemented by firstly establishing a solid finite element model of a rotating shaft, performing modal analysis under a free boundary condition, and extracting natural frequencies of free modes As a reference, defining the shear correction coefficient of each shaft section of the rotor as a design vector variable x to be optimized, and constructing an optimization objective function aiming at minimizing the relative error between the reference frequency and the theoretical calculation frequency: f i (x) is an optimization objective function, omega i (x) is the ith-order natural frequency of the rotating shaft calculated by the Riccati transmission matrix model under the current variable x; And solving the optimized objective function by utilizing a multi-objective genetic algorithm to select an optimal shear correction coefficient, and introducing the optimized shear correction coefficient into the Riccati transfer matrix model.
  3. 3. The modeling method of a permanent magnet motor rotor dynamics model according to claim 1, wherein the equivalent bending stiffness in the step (2) is calculated as follows: Firstly, setting simple branch constraints at two ends of a discrete local finite element model, respectively setting loading points at intervals of a supporting point a, applying a load with the size of P/2, and carrying out simulation analysis on the discrete local finite element models with different lamination numbers in each group to extract the total mid-span deflection w; based on the shear modulus and volume fraction of each material layer in the lamination assembly, calculating the equivalent shear stiffness By means of equivalent shear stiffness Calculating theoretical shearing deflection of each group of discrete local finite element models at mid-span positions under four-point bending loading, subtracting the theoretical shearing deflection from the mid-span total deflection w extracted by simulation, analyzing and separating out bending deformation components only contributed by bending effects, and obtaining equivalent bending stiffness (EI) eq according to the bending deformation components, wherein the calculation formula is as follows: wherein P is the total radial load applied on the discrete local finite element model, a is the distance from the loading point to the supporting point, and L is the span length of the supporting points at the two ends of the discrete local finite element model.
  4. 4. The modeling method of a permanent magnet motor rotor dynamics model according to claim 1, wherein the fitting formula of the power function attenuation relation in the step (3) is as follows: Wherein (EI) eq (n) is the equivalent bending stiffness at a lamination number n, lambda 1 and lambda 2 are fitting coefficients, lambda 1 ＞0,λ 2 <0.
  5. 5. The modeling method of the rotor dynamics model of the permanent magnet motor of claim 4, wherein in the step (3), a fitting formula of a power function attenuation relation is utilized, an actual lamination number is input to calculate to obtain an equivalent bending stiffness of an actual rotor core lamination assembly, and an actual geometrical section moment of inertia I real of a rotor core is combined, so that the attenuated stiffness characteristic of the lamination structure is characterized as an equivalent elastic modulus E eq of a material property layer, and the fitting extrapolation is used for obtaining an equivalent parameter under the actual lamination number on the basis of a limited sample, so that the lamination structure equivalent parameter can serve for full-size rotor dynamics modeling.
  6. 6. The method of modeling a rotor dynamics model of a permanent magnet motor according to claim 1, wherein in the step (3), in the process of constructing a complete rotor system Riccati transfer matrix model, an equivalent mass diameter method is adopted to calculate an equivalent section moment of inertia I eq of a rotor core node, and the specific formula is as follows: Wherein d eq is the equivalent outer diameter, d s is the outer diameter of the rotating shaft, m a is the mass of the accessory component, ρ is the density of the rotating shaft material, and l is the length of the shaft section; The product of the equivalent elastic modulus E eq and the equivalent section moment of inertia I eq is used as a bending stiffness parameter in a Riccati transfer matrix model of the complete rotor system to represent the reinforcing effect of the rotor core lamination assembly on the rigidity of the rotating shaft, and then the mass and the moment of inertia parameters of all parts except the rotating shaft are combined to establish a complete transfer matrix of all shaft sections and a transfer matrix of a node rigid disc, the state vector recurrence relation of the complete rotor system is deduced through Riccati transformation, a frequency characteristic equation of the rotor system is established, and the inherent frequency, the critical rotating speed and the vibration mode of the rotor system are solved.
  7. 7. A computer device comprising a memory and a processor, wherein the memory has a computer program stored therein, and the processor is configured to execute the computer program to implement the method for modeling a rotor dynamics model of a permanent magnet motor according to any one of claims 1 to 6.
  8. 8. A computer readable storage medium storing a computer program, wherein the computer program is executed by a processor to implement the method for modeling a rotor dynamics model of a permanent magnet motor according to any one of claims 1 to 6.

Description

Modeling method for permanent magnet motor rotor dynamics model Technical Field The invention belongs to the technical field of motor rotor dynamics analysis, and particularly relates to a permanent magnet motor rotor dynamics model modeling method. Background The high-speed permanent magnet motor occupies an important position in the field of high-end equipment by virtue of the high power density, high efficiency and compact structural characteristics. In order to ensure safe and stable operation under high-speed working conditions, it is particularly necessary to establish an accurate dynamic model to accurately predict the critical rotation speed and modal characteristics of the rotor However, the lamination of the silicon steel sheets, which is characteristic of the rotor core, brings about significant difficulty in accurate modeling. Due to the nonlinear microscopic contact and friction effects between the laminations, the rotor exhibits complex mechanical characteristics, its actual bending stiffness is significantly lower than theoretical values calculated based on solid materials, and exhibits nonlinear attenuation characteristics as a function of the number of layers. In the prior art, when a rotor dynamics model is established, the true deformation mechanism of the laminated structure when loaded is often difficult to accurately represent. The document [ Wang Dongxiong, cao Kanglei, yu Zewen ] modal characteristics of a rotor system of a high-speed built-in permanent magnet motor bearing, 2024 (7): 62-71] proposes a rotor equivalent elastic modulus algorithm based on a cantilever beam model which considers the characteristics of different materials of multiple components, but the method is mainly based on an idealized analytical assumption and does not consider the influence of lamination and interference fit of silicon steel sheets. The literature [ golden plane, zhang Zhengyue, huang Daoqiong. Research on the rotor dynamics of a high-speed permanent magnet motor. Rocket propulsion, 2019,45 (3): 20-25] proposes a method for calculating the actual rigidity by calculating the rigidity of models with different lamination numbers and fitting the curve, however, the method is to apply forced displacement at the axial center position to obtain counter force so as to perform counter calculation, the shearing deformation is kneaded, and shearing force is mixed in the counter force, so that the equivalent elastic modulus which can be directly used for calculation cannot be obtained. If the parameters are directly applied to a rotor dynamics equation, the mechanical behavior of the rotor under full-size and high-speed working conditions is difficult to truly reflect, so that the prediction results of key indexes such as critical rotation speed and the like have deviation. Disclosure of Invention In view of the above, the invention provides a modeling method for a rotor dynamics model of a permanent magnet motor, which aims to construct a set of integral modeling flow from component equivalence to system integration, definite physical meaning and high precision, so as to solve the problem of prediction deviation of the rotor dynamics model caused by inaccurate equivalent of complex components such as a laminated structure, and the like, and has the advantages of higher calculation speed and high accuracy compared with a finite element method. A modeling method of a permanent magnet motor rotor dynamics model comprises the following steps: (1) The method comprises the steps of dispersing a permanent magnet motor rotor into a plurality of nodes and shaft sections positioned between adjacent nodes along the axial direction, and establishing a Riccati (Riccati) transmission matrix model; (2) Constructing a plurality of groups of discrete local finite element models with different lamination numbers for the rotor core lamination assembly, applying four-point bending loading boundary conditions to each group of discrete local finite element models, extracting the mid-span total deflection of the models in a pure bending section, dividing the mid-span total deflection into a bending deformation component and a shearing deformation component by using a Timoshenko (ironwood Xin Ke) beam theory, establishing a deflection-stiffness back calculation relation, and calculating to obtain the equivalent bending stiffness under the corresponding lamination number; (3) The method comprises the steps of establishing a power function attenuation relation of equivalent bending stiffness along with the change of the number of laminations, determining the equivalent elastic modulus of a rotor core lamination assembly under the actual number of laminations through fitting extrapolation calculation, endowing the equivalent elastic modulus to a corresponding shaft section of a rotor core to characterize the stiffness reinforcing effect of the shaft section, constructing a complete rotor system Riccati transfer matrix model containin