Permanent magnet motor rotor strength evaluation method based on virtual interference boundary condition

Abstract

The invention discloses a permanent magnet motor rotor strength evaluation method based on virtual interference magnitude boundary conditions. The method comprises the steps that a general structure model of a permanent magnet motor rotor sleeved with a composite material sheath is established, and rotor initial boundary conditions and rotor iteration boundary conditions are established based on the general structure model and winding process parameters of the composite material sheath; obtaining the virtual interference magnitude of the first winding layer of the composite material sheath based on the initial boundary condition of the rotor, and inputting the virtual interference magnitude into the iterative boundary condition of the rotor to obtain the virtual interference magnitude of each layer; and based on the obtained virtual interference magnitude and different extreme working conditions of the rotor, establishing boundary conditions of the working conditions of the rotor, obtaining stress distribution of the rotor under different extreme working conditions, and further extracting the maximum stress to evaluate the strength of the rotor. Compared with a traditional analytical method, the method is higher in accuracy and faster in estimation compared with a finite element method, has the remarkable advantages of being high in universality, high in estimation speed and high in accuracy, and can rapidly evaluate the rotor strength.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the strength of a motor rotor, and particularly to a method for evaluating the strength of a permanent magnet motor rotor based on a boundary condition containing a virtual interference. Background Art

[0002] Surface-mounted permanent magnet motors (SMDs) are increasingly being used in energy storage flywheels, micro gas turbines, high-speed machine tools, and other applications due to their high power density and low losses. To prevent slippage and cracking caused by the immense centrifugal forces during high-speed rotation, the motor's permanent magnets require securement. Because rare earth permanent magnets inherently resist compression but not tension, this is typically achieved using an external sheath.

[0003] Composite sheaths protect permanent magnets through both structural interference fit and direct winding. Because composite materials have a low coefficient of thermal expansion, large interference fits are difficult to achieve through temperature differential assembly processes. Direct pressing can also damage composite wire. Therefore, high-tension composite winding is often used in high-speed motors.

[0004] Traditional analytical methods simplify the sheath as a whole for evaluation, ignoring the influence of actual winding process parameters such as winding tension. The resulting results are difficult to directly apply to actual processing. Finite element methods utilize an equivalent temperature field to evaluate composite materials layer by layer, offering high accuracy. However, the actual modeling is complex and computationally inefficient. Summary of the Invention

[0005] In response to the above-mentioned technical problems existing in the prior art, the present invention provides a permanent magnet motor rotor strength evaluation method based on a boundary condition containing a virtual interference. The present invention derives a new rotor strength analytical model and uses the model to complete the evaluation of the rotor strength under different working conditions. The composite sheath provides pre-tightening force for the permanent magnet by applying winding tension, while the alloy sheath achieves the same effect through interference assembly. Although the two have different ways of applying pre-tightening force, the final effect on the permanent magnet is similar. Therefore, it is assumed that there is a virtual interference between adjacent winding layers of the composite sheath to equivalent the effect of winding tension. It is worth noting that the effect of each layer of winding tension can be equivalent to an independent virtual interference, which is not affected by the winding layer that has not yet been wound and the operating conditions of the rotor. The method of the present invention is more accurate than the traditional analytical method and faster than the finite element method. It has the advantages of strong versatility, high speed and high accuracy.

[0006] The technical solution adopted in the present invention is:

[0007] The permanent magnet motor rotor strength evaluation method based on the virtual interference boundary condition of the present invention includes:

[0008] Step 1) establishing a general structural model of a permanent magnet motor rotor sheathed with a composite material sheath, inputting the structural parameters and material parameters of the rotor into the general structural model, and establishing the rotor initial boundary conditions and the rotor iterative boundary conditions based on the winding process parameters of the composite material sheath.

[0009] Step 2) Based on the initial boundary conditions of the rotor, the virtual interference of the first winding layer of the composite sheath is obtained, and then input into the rotor iterative boundary conditions. From the inner winding layer to the outer winding layer of the composite sheath, the virtual interference of each winding layer of the composite sheath is iterated in sequence to complete the rotor analytical modeling.

[0010] Step 3) Based on the obtained virtual interference and different extreme rotor operating conditions, the rotor operating boundary conditions are established to obtain the stress distribution of the rotor under different extreme operating conditions, and then the maximum stress is extracted to evaluate the rotor strength.

[0011] In the step 1), the rotor of the permanent magnet motor also includes a permanent magnet and an alloy shaft wrapped around it, and the composite sheath is wrapped around the alloy shaft; the universal structural model includes a cylindrical universal structural model of the permanent magnet, a cylindrical universal structural model of the alloy shaft, and a cylindrical universal structural model of each winding layer in the composite sheath, wherein the innermost winding layer in the composite sheath is the first winding layer of the composite sheath.

[0012] In the step 1), the structural parameters of the rotor include the radii of the permanent magnet and the alloy shaft and the thickness of a single-layer winding layer of the composite sheath; the material parameters of the rotor include the Poisson's ratio, material density, material elastic modulus and material thermal expansion coefficient of the permanent magnet, the Poisson's ratio, material elastic modulus, material density and material thermal expansion coefficient of the alloy shaft, and the radial elastic modulus and circumferential elastic modulus, radial thermal expansion coefficient and circumferential thermal expansion coefficient, radial Poisson's ratio and circumferential Poisson's ratio and material density of the composite sheath; and the winding process parameters of the composite sheath include the number of winding layers and the winding tension of each layer.

[0013] In step 1), the initial boundary conditions of the rotor are as follows:

[0014]

[0015] Among them, u m (),u a () and u c_1 () are the radial displacements of the permanent magnet, alloy shaft and the first winding layer of the composite sheath respectively; R a and R c 1 is the inner radius of the alloy shaft and the first winding layer of the composite sheath; R m_out 、R a_outand R c_out_1 are the outer radius of the first winding layer of the permanent magnet, alloy shaft and composite sheath respectively; H fit is the interference fit between the permanent magnet and the alloy shaft; σ rm (),σ ra () and σ rc_1 () are the radial stresses of the permanent magnet, the alloy shaft and the first winding layer of the composite sheath respectively; δ1 is the virtual interference of the first winding layer of the composite sheath; σ θc_1 () is the circumferential stress of the first winding layer of the composite sheath; H c is the thickness of a single layer of the composite sheath; σ w_1 It is the winding tension of the first winding layer of the composite sheath.

[0016] In step 1), the rotor iteration boundary conditions are as follows:

[0017]

[0018] Among them, u c_k (),u c_k-1 (),u c_i () and u c_i-1 are the radial displacements of the kth, k-1th, ith and i-1th winding layers of the composite sheath respectively; R c_k and R c_i are the inner radius of the kth and ith winding layers of the composite sheath respectively; R c_out_k 、R c_out_k-1 and R c_out_i are the outer radii of the kth, k-1th and ith winding layers of the composite sheath; δ k and δ i are the virtual interferences of the kth and ith winding layers of the composite sheath respectively; σ rc_k (),σ rc_k-1 (),σ rc_i () and σ rc_i-1 () are the radial stresses of the kth, k-1th, ith and i-1th winding layers of the composite sheath respectively; σ θc_i () is the circumferential stress of the i-th winding layer of the composite sheath; σ w_i is the winding tension of the i-th winding layer of the composite sheath.

[0019] In the step 3), the different extreme working conditions of the rotor include static normal temperature, high speed normal temperature, static high temperature and high speed high temperature working conditions. Under static normal temperature working conditions: n = 0, ΔT = 0; under high speed normal temperature working conditions: n = n max , ΔT=0, under static high temperature conditions: n=0, ΔT=ΔTmax , under high speed and high temperature conditions: n=n max , ΔT=ΔT max , n and n max are the rotor speed and its maximum speed respectively; ΔT and ΔT max are the rotor temperature rise and its maximum temperature rise respectively.

[0020] In step 3), the rotor operating boundary conditions are as follows:

[0021]

[0022] Among them, u m () and u a () are the radial displacements of the permanent magnet and the alloy shaft respectively; R a is the inner radius of the alloy shaft, R m_out is the outer radius of the permanent magnet; H fit is the interference fit between the permanent magnet and the alloy shaft; σ rm () and σ ra () are the radial stresses of the permanent magnet and the alloy shaft respectively; u c_i () and u c_i-1 () are the radial displacements of the i-th and i-1-th winding layers of the composite sheath respectively; R c_i is the inner radius of the i-th winding layer of the composite sheath; R c_out_i and R c_out_i-1 are the outer radii of the i-th and i-1-th winding layers of the composite sheath respectively; δ i is the virtual interference of the i-th winding layer of the composite sheath; σ rc_i () and σ rc_i-1 () are the radial stresses of the i-th and i-1-th winding layers of the composite sheath respectively; N is the total number of winding layers of the composite sheath.

[0023] The stress distribution of the rotor is obtained according to the radial stress and circumferential stress of the permanent magnet and the alloy shaft, as well as the radial stress and circumferential stress of each winding layer of the composite sheath.

[0024] The radius of each winding layer of the permanent magnet, alloy shaft and composite material sheath in steps 1) to 3) is a virtual radius. Since the analytical model has a virtual interference δ i , so the virtual radius is not the actual radius. The actual radius is equal to the virtual radius plus the radial displacement, for example, R a ′=R a +u a (R a ), R′ a and R a are the actual and virtual inner radii of the alloy shaft respectively.

[0025] The electronic device of the present invention comprises: a memory and a processor coupled to each other, wherein the memory stores program data, and the processor calls the program data to execute the method described above.

[0026] The computer-readable storage medium of the present invention stores program data thereon, and is characterized in that the program data implements the method described above when executed by a processor.

[0027] This method utilizes theories related to material mechanics to innovatively propose the concept of "virtual interference," which is then used to analytically model the winding process of a rotor composite sheath. Through an iterative solution, the virtual interference is derived. The resulting analytical model is then used to assess rotor strength under extreme rotor operating conditions.

[0028] The beneficial effects of the present invention are:

[0029] 1) Efficient and Accurate Modeling and Strong Versatility: The method presented here enables rapid and precise rotor modeling. It not only enables detailed evaluation of the rotor sheath winding process but also comprehensively analyzes various complex rotor operating conditions, demonstrating strong versatility. Compared to existing evaluation methods, this method, based on numerical estimation, cleverly avoids the complexity and computational complexity of finite element simulation modeling, offering the advantages of fast computational speed, minimal computational effort, and high accuracy.

[0030] 2) Compatibility with engineering practice: The method of the present invention fully considers the winding process parameters of the composite sheath. On the one hand, it can accurately evaluate the stress distribution during the winding process; on the other hand, it can also provide a direct and effective reference basis for actual engineering manufacturing, and has strong guiding significance for engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the method of the present invention;

[0032] Figure 2 This is the structure diagram of the surface-mounted permanent magnet motor rotor;

[0033] Figure 3 The residual tension distribution diagram of different winding layers of the composite sheath under different winding tension conditions;

[0034] Figure 4 is the stress distribution diagram of the motor rotor under different extreme working conditions, where: Figure 4 (a) is the radial stress distribution diagram, Figure 4 (b) is the circumferential stress distribution diagram. Figure 4 (c) is the equivalent stress distribution diagram;

[0035] In the figure: 1. Permanent magnet, 2. Alloy shaft, 3. Composite material sheath. DETAILED DESCRIPTION

[0036] In order to describe the present invention in more detail, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 As shown, the permanent magnet motor rotor strength evaluation method based on the virtual interference boundary condition of the present invention is specifically as follows:

[0038] Step 1) First, use the relevant theories of material mechanics to establish a general structural model of the permanent magnet motor rotor with a composite material sheath 3, such as Figure 2 The figure shows the rotor structure model. The permanent magnet motor rotor also includes a permanent magnet 1 and an alloy shaft 2 encased therein, with a composite sheath 3 encased therein. The general structural model includes a cylindrical general structural model for the permanent magnet 1, a cylindrical general structural model for the alloy shaft 2, and a cylindrical general structural model for each winding layer in the composite sheath 3. The innermost winding layer in the composite sheath 3 is the first winding layer of the composite sheath 3. The alloy shaft 2 and the permanent magnet 1 have an interference fit, and the composite material is wound around the alloy shaft 2 to form the composite sheath 3. The general analytical model of each rotor component can be derived using the thick-walled cylinder theory of material mechanics.

[0039] The analytical model of permanent magnet 1 is as follows:

[0040] u m (r)=C 1m r

[0041]

[0042] The analytical model of alloy shaft 2 is as follows:

[0043] u a (r)=C 1a r+C 2a r -1

[0044]

[0045] The analytical model of the i-th winding layer of the composite sheath 3 is as follows:

[0046]

[0047] u c_i (r)=C 1c_i r k +C 2c_i r -k

[0048]

[0049] Wherein, subscript m represents the permanent magnet 1, subscript a represents the alloy shaft 2, and subscript c represents the composite sheath 3; u is the radial displacement; r is the radius of the infinitesimal element; C 1m 、C 1a 、C 2a 、C 1c_i and C 2c_i are the first, second, third, fourth and fifth unknown coefficients respectively; σ r and σ θ are radial and circumferential stresses respectively; E and μ are elastic modulus and Poisson's ratio respectively; k is the calculation coefficient that can be obtained from material parameters; E r and E θ are the radial and circumferential elastic moduli of the material respectively; μ θr and μ rθ are the radial and circumferential Poisson's ratios of the material respectively; the composite material can specifically be carbon fiber material.

[0050] Typical winding tension control mainly includes constant tension mode, taper tension model and constant torque mode, which satisfy the following relationship:

[0051]

[0052] Wherein, α is the taper coefficient, 0<α<1; R0 is the core mold radius, that is, the inner radius of the i-th winding layer of the composite sheath 3; σ w is the initial winding tension of the composite material.

[0053] Then, the structural parameters and material parameters of the rotor are input into the general structural model, and the initial boundary conditions and the iterative boundary conditions of the rotor are established based on the winding process parameters of the composite sheath. The structural parameters of the rotor include the radii of the permanent magnet 1 and the alloy shaft 2 and the thickness of the single-layer winding layer of the composite sheath 3. The radius of the permanent magnet 1 includes the outer radius and the inner radius of the permanent magnet 1. The material parameters of the rotor include the material Poisson's ratio, material density, material elastic modulus and material thermal expansion coefficient of the permanent magnet 1, the material Poisson's ratio, material elastic modulus, material density and material thermal expansion coefficient of the alloy shaft 2, and the material radial elastic modulus and circumferential elastic modulus, material radial thermal expansion coefficient and circumferential thermal expansion coefficient, material radial Poisson's ratio and circumferential Poisson's ratio and material density of the composite sheath 3. The winding process parameters of the composite sheath include the number of winding layers and the winding tension of each layer.

[0054] The initial boundary conditions of the rotor are as follows:

[0055]

[0056] Among them, u m (),u a () and u c_1 () are the radial displacements of the first winding layer of the permanent magnet 1, the alloy shaft 2 and the composite sheath 3 respectively; R a and R c_1 R are the inner radius of the first winding layer of the alloy shaft 2 and the composite sheath 3 respectively; m_out 、R a_out and R c_out_1 H are the outer radius of the first winding layer of the permanent magnet 1, the alloy shaft 2 and the composite sheath 3 respectively; fit is the interference fit between the permanent magnet 1 and the alloy shaft 2; σ rm (),σ ra () and σ rc_1 () are the radial stresses of the first winding layer of the permanent magnet 1, the alloy shaft 2 and the composite sheath 3 respectively; δ1 is the virtual interference of the first winding layer of the composite sheath 3; σ θc_1 () is the circumferential stress of the first winding layer of the composite sheath 3; H c is the thickness of a single wound layer of the composite sheath 3; σ w_1 is the winding tension of the first winding layer of the composite sheath 3.

[0057] There are 6 equations and 6 undetermined coefficients in the rotor initial boundary conditions: C 1m 、C 1a 、C 2a 、C 1c_1 、C 2c_1 and δ1, so the unique virtual interference δ1 can be solved.

[0058] Then, combined with the winding tension, the rotor iterative boundary conditions can be established and solved layer by layer from the inner layer to the outer layer of the composite sheath 3, as follows:

[0059]

[0060] Among them, u c_k (),u c_k-1 (),u c_i () and u c_i-1 are the radial displacements of the kth, k-1th, ith and i-1th winding layers of the composite sheath 3 respectively; R c_k and R c_i are the inner radius of the kth and ith winding layers of the composite sheath 3 respectively; R c_out_k 、R c_out_k-1 and R c_out_iare the outer radii of the kth, k-1th and ith winding layers of the composite sheath 3; δ k and δ i are the virtual interferences of the kth and ith winding layers of the composite sheath 3, respectively. In the current iteration process, δ k and δ i are the known quantity and the unknown quantity respectively; σ rc_k (),σ rc_k-1 (),σ rc_i () and σ rc_i-1 () are the radial stresses of the kth, k-1th, ith and i-1th winding layers of the composite sheath 3 respectively; σ θc_i () is the circumferential stress of the i-th winding layer of the composite sheath 3; σ w_i is the winding tension of the i-th winding layer of the composite sheath 3; u c_0 ()=u a (); σ rc_0 ()=σ ra ().

[0061] Starting from the inner layer, the new virtual interference is solved layer by layer. Specifically, based on the virtual interference of several winding layers, the winding tension of the outermost winding layer in the current iteration is used to establish an iterative boundary condition. The boundary condition is used to solve the virtual interference of the outermost layer in the current iteration. The iterative solution is continued until the required number of winding layers is reached, completing the entire winding process.

[0062] There are 2i+4 equations in the rotor iteration boundary conditions, and i-1 δ k It has been found in the iterative process, so there are only 2i+4 coefficients to be determined: C 1m 、C 1a 、C 2a 、C 1c_k 、C 2c_k 、C 1c_i 、C 2c_i and δ i , the outermost virtual interference δ can be obtained uniquely at each iteration i When the iterative solution is completed, the residual stress of the composite sheath 3 after winding can be evaluated, such as Figure 3 As shown in the figure, the residual tension changes of the sheath in the constant tension mode, the taper tension mode with a taper coefficient of 0.5 and the constant torque mode can be seen. Comparing the corresponding analytical method and the finite element method, it can be seen that the errors of the two are small, and the maximum error is only 0.0985%.

[0063] Based on the initial boundary conditions of the rotor, the virtual interference of the first winding layer of the composite sheath is obtained, and then input into the iterative boundary conditions of the rotor. From the inner winding layer to the outer winding layer of the composite sheath, the virtual interference of each winding layer of the composite sheath is iterated in sequence, and the analytical modeling of the rotor is completed.

[0064] After determining all virtual interferences, all rotor parameters are obtained and the rotor analytical modeling is determined. Because the rotor operating conditions mainly depend on the rotor speed and rotor temperature rise, a general analytical model of each rotor component considering rotation and temperature rise can be obtained through material mechanics theory.

[0065] The analytical model of permanent magnet 1 is as follows:

[0066]

[0067] The analytical model of alloy shaft 2 is as follows:

[0068]

[0069]

[0070] The analytical model of the i-th winding layer of the composite sheath 3 is as follows:

[0071] C T =k 2 (β θc +μ θrc β rc )-(β rc +μ rθc β θc )

[0072]

[0073] Where ρ is the material density; ω is the rotor angular velocity; C T is the calculation coefficient that can be obtained from the material parameters; β r and β θ are the radial and circumferential thermal expansion coefficients of the material, respectively.

[0074] Step 3) Based on the obtained virtual interference and different extreme rotor working conditions, establish the rotor working condition boundary conditions; the different extreme rotor working conditions include static normal temperature, high speed normal temperature, static high temperature and high speed high temperature working conditions, under static normal temperature condition: n = 0, ΔT = 0, under high speed normal temperature condition: n = n max , ΔT=0, under static high temperature conditions: n=0, ΔT=ΔT max , under high speed and high temperature conditions: n=n max , ΔT=ΔT max , n and n maxare the rotor speed and its maximum speed respectively; ΔT and ΔT max They are the rotor temperature rise and its maximum temperature rise respectively. The rotor operating boundary conditions under different extreme working conditions are as follows:

[0075]

[0076] Among them, u m () and u a () are the radial displacements of the permanent magnet 1 and the alloy shaft 2 respectively; R a is the inner radius of the alloy shaft 2, R m_out is the outer radius of the permanent magnet 1; H fit is the interference fit between the permanent magnet 1 and the alloy shaft 2; σ rm () and σ ra () are the radial stresses of permanent magnet 1 and alloy shaft 2 respectively; u c_i () and u c_i-1 () are the radial displacements of the i-th and i-1-th winding layers of the composite sheath 3; R c_i is the inner radius of the i-th winding layer of the composite sheath 3; R c_out_i and R c_out_i-1 are the outer radii of the i-th and i-1-th winding layers of the composite sheath 3 respectively; δ i is the virtual interference of the i-th winding layer of the composite sheath 3; σ rc_i () and σ rc_i-1 () are the radial stresses of the i-th and i-1-th winding layers of the composite sheath 3 respectively; N is the total number of winding layers of the composite sheath 3.

[0077] The stress distribution of the rotor is obtained based on the radial stress and circumferential stress of the permanent magnet 1 and the alloy shaft 2, as well as the radial stress and circumferential stress of each winding layer of the composite sheath 3, and the maximum stress is extracted to evaluate the rotor strength.

[0078] The radius of each winding layer of the permanent magnet 1, the alloy shaft 2 and the composite sheath 3 is a virtual radius. Due to the existence of a virtual interference δ in the analytical model, i , so the virtual radius is not the actual radius. The actual radius is equal to the virtual radius plus the radial displacement, for example, R a ′=R a +u a (R a ), R′ a and R a are the actual and virtual inner radius of the alloy shaft 2 respectively.

[0079] Because the alloy material is a plastic material, the fourth strength theory is used for evaluation. It is necessary to calculate the equivalent stress of the rotor, specifically:

[0080]

[0081] Among them, σ r , σ θ and σ z are radial stress, circumferential stress and axial stress respectively. Since the present invention only considers the two-dimensional structure of the rotor, σ z =0.

[0082] Taking the taper tension mode (taper coefficient is 0.5) as an example, the stress distribution of the rotor under different extreme stress conditions can be calculated, such as Figure 4 (a) Figure 4 (b) and Figure 4 As shown in (c), this embodiment is calculated using MATLAB under the configuration of Intel(R) Core(TM) i7-10700 CPU@2.90GHz (16CPUs), and the calculation time is only 30s, which can illustrate the speed and effectiveness of the method of the present invention.

[0083] In order to better illustrate the correctness of the method of the present invention, a finite element model with the same parameters as in this embodiment was established and compared with the analytical method. The specific comparison is shown in Table 1.

[0084] Table 1 Comparison of analytical and finite element method results

[0085]

[0086] As can be seen from Table 1, the results of the analytical method in the present invention are basically consistent with those of the finite element method, with the maximum error being only 1.3% and the remaining errors being less than 0.2%, which illustrates the accuracy of the method of the present invention.

[0087] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A permanent magnet motor rotor strength evaluation method based on a virtual interference boundary condition, characterized in that: include: Step 1) establishing a general structural model of a permanent magnet motor rotor covered with a composite material sheath (3), inputting the structural parameters and material parameters of the rotor into the general structural model, and establishing the rotor initial boundary conditions and the rotor iterative boundary conditions based on the winding process parameters of the composite material sheath; Step 2) obtaining a virtual interference of the first winding layer of the composite sheath based on the initial boundary conditions of the rotor, and then inputting the virtual interference of the first winding layer of the composite sheath into the iterative boundary conditions of the rotor, and iteratively obtaining the virtual interference of each winding layer of the composite sheath from the inner winding layer to the outer winding layer; Step 3) Based on the obtained virtual interference and different extreme rotor operating conditions, the rotor operating boundary conditions are established to obtain the stress distribution of the rotor under different extreme operating conditions, and then the maximum stress is extracted to evaluate the rotor strength.

2. The permanent magnet motor rotor strength assessment method based on the virtual interference boundary condition according to claim 1 is characterized in that: In the step 1), the rotor of the permanent magnet motor further comprises a permanent magnet (1) and an alloy shaft (2) sleeved thereon, and the composite material sheath (3) is sleeved outside the alloy shaft (2); the universal structural model comprises a cylindrical universal structural model of the permanent magnet (1), a cylindrical universal structural model of the alloy shaft (2), and a cylindrical universal structural model of each winding layer in the composite material sheath (3), wherein the innermost winding layer in the composite material sheath (3) is the first winding layer of the composite material sheath (3).

3. The permanent magnet motor rotor strength assessment method based on the virtual interference boundary condition according to claim 2 is characterized in that: In the step 1), the structural parameters of the rotor include the radii of the permanent magnet (1) and the alloy shaft (2) and the thickness of a single-layer winding layer of the composite material sheath (3); the material parameters of the rotor include the material Poisson's ratio, material density, material elastic modulus and material thermal expansion coefficient of the permanent magnet (1), the material Poisson's ratio, material elastic modulus, material density and material thermal expansion coefficient of the alloy shaft (2), and the material radial elastic modulus and circumferential elastic modulus, material radial thermal expansion coefficient and circumferential thermal expansion coefficient, material radial Poisson's ratio and circumferential Poisson's ratio and material density of the composite material sheath (3); and the winding process parameters of the composite material sheath include the number of winding layers and the winding tension of each layer.

4. The permanent magnet motor rotor strength assessment method based on the virtual interference boundary condition according to claim 1 is characterized in that: In step 1), the initial boundary conditions of the rotor are as follows: Among them, u m (),u a () and u c_1 () are the radial displacements of the first winding layer of the permanent magnet (1), the alloy shaft (2) and the composite sheath (3); R a and R c_1 are the inner radius of the first winding layer of the alloy shaft (2) and the composite sheath (3); R m_out 、R a_out and R c_out_1 are the outer radius of the first winding layer of the permanent magnet (1), the alloy shaft (2) and the composite material sheath (3); H fit is the interference fit between the permanent magnet (1) and the alloy shaft (2); σ rm (),σ ra () and σ rc_1 () are the radial stresses of the first winding layer of the permanent magnet (1), the alloy shaft (2) and the composite material sheath (3); δ1 is the virtual interference of the first winding layer of the composite material sheath (3); σ θc_1 () is the circumferential stress of the first winding layer of the composite sheath (3); H c is the thickness of a single wound layer of the composite sheath (3); σ w_1 It is the winding tension of the first winding layer of the composite material sheath (3).

5. The method for evaluating the rotor strength of a permanent magnet motor based on a boundary condition containing a virtual interference according to claim 4, characterized in that: In step 1), the rotor iteration boundary conditions are as follows: Among them, u c_k (),u c_k-1 (),u c_i () and u c_i-1 are the radial displacements of the kth, k-1th, ith and i-1th winding layers of the composite sheath (3); R c_k and R c_i are the inner radii of the kth and ith winding layers of the composite sheath (3); R coutk 、R coutk-1 and R couti are the outer radii of the kth, k-1th and ith winding layers of the composite sheath (3); δ k and δ i are the virtual interferences of the kth and ith winding layers of the composite sheath (3); σ rc_k (),σ rc_k-1 (),σ rc_i () and σ rc_i-1 () are the radial stresses of the kth, k-1th, ith and i-1th winding layers of the composite sheath (3); σ θc_i () is the circumferential stress of the i-th winding layer of the composite sheath (3); σ w_i is the winding tension of the i-th winding layer of the composite material sheath (3).

6. The method for evaluating the rotor strength of a permanent magnet motor based on a boundary condition containing a virtual interference according to claim 1, characterized in that: In the step 3), the different extreme working conditions of the rotor include static normal temperature, high speed normal temperature, static high temperature and high speed high temperature working conditions. Under static normal temperature working conditions: n = 0, ΔT = 0; under high speed normal temperature working conditions: n = n max , ΔT=0, under static high temperature conditions: n=0, ΔT=ΔT max , under high speed and high temperature conditions: n=n max , ΔT=ΔT max , n and n max are the rotor speed and its maximum speed respectively; ΔT and ΔT max are the rotor temperature rise and its maximum temperature rise respectively.

7. The method for evaluating the rotor strength of a permanent magnet motor based on a boundary condition containing a virtual interference according to claim 1, characterized in that: In step 3), the rotor operating boundary conditions are as follows: Among them, u m () and u a () are the radial displacements of the permanent magnet (1) and the alloy shaft (2); R a is the inner radius of the alloy shaft (2), R m_out is the outer radius of the permanent magnet (1); H fit is the interference fit between the permanent magnet (1) and the alloy shaft (2); σ rm () and σ ra () are the radial stresses of the permanent magnet (1) and the alloy shaft (2); u c_i () and u c_i-1 () are the radial displacements of the i-th and i-1-th winding layers of the composite sheath (3); R c_i is the inner radius of the i-th winding layer of the composite sheath (3); R c_out_i and R c_out_i-1 are the outer radii of the i-th and i-1-th winding layers of the composite sheath (3); δ i is the virtual interference of the i-th winding layer of the composite sheath (3); σ rc_i () and σ rc_i-1 () are radial stresses of the i-th and i-1-th winding layers of the composite sheath (3); N is the total number of winding layers of the composite sheath (3); The stress distribution of the rotor is obtained based on the radial stress and circumferential stress of the permanent magnet (1) and the alloy shaft (2) and the radial stress and circumferential stress of each winding layer of the composite material sheath (3).

8. The method for evaluating the rotor strength of a permanent magnet motor based on a boundary condition containing a virtual interference according to claim 2, characterized in that: The radius of each winding layer of the permanent magnet (1), the alloy shaft (2) and the composite material sheath (3) in steps 1) to 3) is a virtual radius, and the actual radius is equal to the virtual radius plus the radial displacement.

9. An electronic device, characterized in that: include: A memory and a processor coupled to each other, wherein the memory stores program data, and the processor calls the program data to execute the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having program data stored thereon, characterized in that: When the program data is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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