A Simulation and Strength Analysis Method and System for Carbon Fiber Winding of a Surface Mounted Permanent Magnet Rotor

Abstract

The present invention relates to a method and system for simulating and analyzing the strength of a surface-mounted permanent magnet rotor with carbon fiber winding. The carbon fiber winding structure is equivalent to a multi-layer ring with discrete characteristics, and a virtual interference amount is introduced as the winding tension control variable. The force equilibrium differential equation of the rotor at rest is established, and combined with the pressure boundary condition and displacement boundary condition of the rotor contact surface, the pressure and displacement constraint equations are obtained to realize the calculation of the stress during the winding process of the rotor. Based on the winding method of carbon fiber, iterative calculation of the interlayer interference amount is selected to obtain the virtual interlayer interference amount that satisfies the winding tension. On the basis of the analytical iterative calculation, the stress distribution of the rotor under different working conditions is calculated by combining the finite element time series analysis. The principle of this method is clear, which combines the advantages of analytical iteration and finite element analysis, and simulates the real winding process of carbon fiber. In addition, the influence of rotational speed and temperature on the rotor stress is considered, and the rapid and accurate calculation of the stress distribution is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and particularly relates to a method and system for simulating carbon fiber winding and strength analysis of a surface-mounted permanent magnet rotor. Background Art

[0002] High-speed rotation of the rotor is one of the effective measures to improve the power density of permanent magnet motors. However, the high-speed rotation of the rotor directly leads to an increase in the centrifugal force of the rotor, bringing about the problem of an increase in the stress level of the rotor. Rare earth permanent magnets have high compressive strength and low tensile strength. In order to protect the permanent magnet from being damaged under high-speed conditions, an additional rotor protective sleeve needs to be added. The carbon fiber protective sleeve has become the preferred solution for the high-speed permanent magnet rotor sheath due to its outstanding advantages such as light weight, high strength, and low conductivity.

[0003] To offset the centrifugal force borne by the permanent magnet under high-speed conditions, the reasonable design of the carbon fiber protective sleeve is particularly important. The large-tension winding type carbon fiber protective sleeve has significant advantages over the preformed carbon fiber protective sleeve in terms of mechanical properties, process flexibility, manufacturing quality, performance consistency, and durability, and is more widely used in the field of high-power high-speed permanent magnet motors. The carbon fiber wound rotor sheath offsets the centrifugal force in the high-speed rotation state through the prestress provided by the winding tension. To ensure that the stress distribution of the permanent magnet is lower than the allowable level, the accurate calculation of stress components is the key. At present, the stress calculation for carbon fiber wound permanent magnet rotors mainly falls into two categories: the analytical method and the finite element method. In the analytical method, the multi-layer wound carbon fiber protective sleeve is mostly equivalent to an integrated ring structure, resulting in the neglect of the actual winding process of the carbon fiber, with low accuracy and insufficient to provide data support for the accurate calculation of the rotor stress level. To improve the calculation accuracy of the rotor stress, the finite element method is widely used. In the traditional finite element method, the thermal strain of the carbon fiber is used to equivalent the winding tension. The equivalent interference amount is indirectly generated through the thermal strain generated by the carbon fiber winding layer under the influence of temperature to simulate the carbon fiber winding tension. However, the generation of thermal strain changes the material property parameters of the carbon fiber, does not conform to the real material physical properties, and cannot consider the thermal stress generated by the fiber layer under its own temperature, resulting in insufficient calculation accuracy of the rotor stress. In addition, to simulate the carbon fiber winding process, it is necessary to combine the finite element direct iteration and the "birth and death element strategy", which has the defects of large calculation amount and complex calculation process. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] Based on this, the present invention provides a method and system for simulating carbon fiber winding and strength analysis of a high-speed permanent magnet rotor to solve the problems of poor analysis accuracy, large calculation amount, and complex analysis process mentioned in the background art.

[0006] (2) Technical Solutions

[0007] To achieve the above object, the present invention provides a method for simulating and analyzing the strength of a surface-mounted permanent magnet rotor by carbon fiber winding, comprising the following steps:

[0008] S1: Establish an analytical model of the interference amount and stress of the carbon fiber layer; specifically including:

[0009] 1) Expand the permanent magnet rotor along the polar coordinates to form a planar analysis model;

[0010] 2) According to the physical properties, geometric properties and equilibrium differential equations of each component of the rotor, obtain the displacement, radial stress and circumferential stress expressions of each component of the rotor;

[0011] 3) Combine the contact surface pressure constraint and the interference amount-displacement constraint to solve the unknown coefficients in the displacement, radial stress and circumferential stress expressions, and then realize the calculation of the stress;

[0012] S2: Substitute the initial interference amount into the analytical model of the interference amount and stress of the carbon fiber layer to realize the analytical iteration of the equivalent simulation of the carbon fiber winding tension, and obtain the interference amount with iterative convergence; specifically including the following steps:

[0013] S201: Specify the structural parameters and material parameters of the rotor to be wound;

[0014] S202: Specify the initial interference amount of each layer of carbon fiber;

[0015] S203: Based on the given initial interference amount, combine the pressure boundary conditions and displacement constraint conditions of each component of the rotor, and calculate the stress of each part of the rotor according to the analytical model of the interference amount and stress of the carbon fiber layer; and extract the winding stress and residual stress of each layer of carbon fiber during the initial calculation;

[0016] S204: Determine the winding method of the carbon fiber, and the winding method includes equal winding tension and equal residual stress;

[0017] S205: Determine the iteration method, and the iteration method includes the layer-by-layer iteration method and the global iteration method; according to the iteration method, apply the initial interference amount to the analytical model of the interference amount and stress of the carbon fiber layer for iterative calculation to obtain the interference amount with iterative convergence;

[0018] S3: Take the interference amount with iterative convergence as the interference amount of each contact surface of the rotor in the finite element analysis, and perform stress time series analysis of the rotor under different working conditions.

[0019] Optionally, the layer-by-layer iteration method of the equal winding tension method in step S205 includes:

[0020] 1) Specify the material parameters and structural parameters of each component of the rotor;

[0021] 2) Specify the winding parameter N of the carbon fiber and set the initial number of winding layers to 0;

[0022] 3) Prepare to wind the first layer, i = 1, and at the same time set the iteration number k to 1;

[0023] 4) Specify the interference δ for the current winding layer (i) | k , and at the same time specify the winding stress σ of the current winding layer ωN(i) ;

[0024] 5) Combine all the contact pressure equations and displacement constraint equations including the current winding layer, and calculate the winding stress σ of each layer of carbon fiber at the current given interference according to the analytical model of the interference and stress of the carbon fiber layer ω(i) | k ;

[0025] 6) Compare the winding stress σ calculated for the current winding layer ω(i) | k with the specified winding stress σ of the current layer ωN(i) of the relative error Δσ ω(i) | k , where Δσ w(i) | k = abs(σ w(i) | k - σ wN(i) ), and judge whether the ratio of the relative error Δσ ω(i) | k to the specified winding stress σ of the current layer ωN(i) meets the convergence criterion. ξ is a user-defined convergence criterion, that is, Δσ w(i) | k / σ wN(i) ≤ ξ; if the convergence criterion is met, judge whether the current winding layer is the last layer. If it is the last layer, the winding is completed; otherwise, continue to wind the next layer; if the convergence criterion is not met, go to step 7);

[0026] 7) Increase the iteration number k, that is, let k = k + 1; according to the formula δ (i) | k = (Δσ w(i) | k-1 / K (i) ) + δ (i) | k-1 update the interference δ (i) | k , where Δσ ω(i) | k-1 is the difference between the winding stress σ ω(i) | k-1 calculated in the current winding layer and the specified winding stress σ ωN(i) , δ(i) | k-1 is the interference of the current winding layer in the previous iterative calculation, K (i) =(σ w(i) | k＝1 ) / (δ (i) | k＝1 ), and return to step 4).

[0027] Optionally, the global iteration method in step S205 includes:

[0028] 1) Specify the rotor parameters, including the material parameters of each component, the number of carbon fiber winding layers N, and the geometric structure parameters;

[0029] 2) Prepare for winding and set the number of iterations to k = 1;

[0030] 3) Given the virtual interference δ (i) ;

[0031] 4) According to the analytical model of the interference and stress of the carbon fiber layer, calculate the pressure constraint equation and displacement constraint equation corresponding to the current winding layer, and obtain the pressure distribution and stress distribution inside the current rotor;

[0032] 5) Extract the winding stress σ ω (k) of the carbon fiber after the current winding layer is calculated, and determine whether the current winding layer i is the last layer; if it is the last layer, go to step 6); if it is not the last layer, prepare for winding the next layer and return to step 3);

[0033] 6) Extract the residual stress σ re (k) of the carbon fiber layer after all carbon fiber layers are wound, and specify the carbon fiber winding form, which is divided into specifying the winding stress σ ωN and specifying the residual stress σ reN after winding; if it is the specified winding stress σ ωN , then go to step 7); if it is the specified residual stress distribution σ reN after winding, then go to step 8);

[0034] 7) Compare the difference Δσ ω (k) between the winding stress σ ωN obtained in step 5) and the specified winding stress σ ω (k), where Δσ ω (k) = max: abs[σ wN -σ w (k)] / σ wN , represents the maximum value of the relative stress error in all winding layers, and determine whether the difference Δσ ω (k) meets the convergence criterion ξ, ξ is a user-defined convergence criterion, that is, Δσw (k) ≤ ξ. If satisfied, it indicates that the winding simulation is completed, and the interference amount δ after the current winding is output (i) as the final output parameter; if not meeting the requirements, then based on the calculated difference Δσ ω (k), update the interference amount δ between carbon fiber layers (i) δ(i) = Δσ w (k) / K1 + δ(i), where K1 = [σ w (1)| k＝1 / (δ(1)| k＝1 ). Increase the iteration number k, let k = k + 1, and go back to step 3);

[0035] 8) Compare the residual stress σ re (k) obtained in step 6) with the specified residual stress σ reN to get the difference Δσ re (k), where Δσ re (k) = max:abs[σ reN - σ re (k)] / σ reN , representing the maximum value of the relative error of the residual stress in all winding layers, and determine whether the difference meets the convergence criterion ξ. ξ is a convergence criterion defined artificially, that is, Δσ re (k) ≤ ξ; if the convergence requirement is met, it indicates that the winding is completed, and the interference amount δ after the current winding is output (i) as the final output parameter; if the winding requirement is not met, then based on the residual stress σ re (k) after the winding is completed and the specified residual stress σ reN to update the interference amount between carbon fiber layers with the difference Δσ re (k) as the basis,, δ(i) = Δσ re (k) / K2 + δ(i), where K2 = [σ re (1)| k＝1 / (δ(1)| k＝1 ). Increase the iteration number k, let k = k + 1, and go back to step 3).

[0036] Optionally, S3 includes:

[0037] S301: Apply the interference amount of iterative convergence to the model of finite element analysis;

[0038] S302: Add a contact control condition to each layer of carbon fiber layers, numbered from 1 to N, where the number of the layer is the same as the layer number of the carbon fiber; at the initial moment, each layer of contact control is inhibited; when starting the winding, only activate the contact of the first layer; when starting to wind the second layer, maintain the contact of the first layer unchanged and activate the contact of the second layer; when starting to wind the third layer, maintain the contacts of the first and second layers unchanged and activate the third layer; and so on until the contact of the last layer is activated, indicating that the calculation of the carbon fiber winding process is completed.

[0039] S303: After the winding of the Nth layer of carbon fiber is completed, apply rotational speed and temperature to each component of the rotor, and calculate the stress distribution of the rotor considering the influence of rotational speed and temperature. The application of rotational speed and temperature conditions must be after the carbon fiber winding is completed, and there is no order for the application of rotational speed and temperature conditions. According to different combinations of rotational speed and temperature, it is divided into three different working conditions: normal temperature and overspeed, hot state and overspeed, and hot state and static.

[0040] Optionally, the permanent magnet rotor applicable to the winding simulation and strength analysis method includes: a rotor core, surface-mounted permanent magnets, and a multi-layer wound carbon fiber sleeve.

[0041] In addition, the present invention provides a carbon fiber winding simulation and strength analysis system for a surface-mounted permanent magnet rotor, including:

[0042] At least one processor; and

[0043] At least one memory communicatively connected to the processor, wherein:

[0044] The memory stores program instructions executable by the processor, and the processor can execute the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor described in any one of the above by invoking the program instructions.

[0045] In addition, the present invention provides a non-transitory computer-readable storage medium, and the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor described in any one of the above.

[0046] (III) Beneficial effects

[0047] As can be seen from the above technical solutions, the beneficial effects of a carbon fiber sleeve winding simulation and strength analysis method for a high-speed permanent magnet rotor proposed by the present invention are as follows:

[0048] 1. The wound carbon fiber sheath with continuous spiral features is discretized into a multi-layer circular ring structure with a hierarchical independent form, and the distribution of rotor stress during the carbon fiber winding process is accurately calculated through an analytical method. In addition, by establishing a winding analysis model of the permanent magnet rotor in a static state and using the virtual interference amount between carbon fiber layers as a control variable, the equivalent simulation of the winding tension during the carbon fiber winding process is realized, avoiding the defect that the thermal stress generated by the carbon fiber itself due to temperature influence cannot be considered when the existing finite element analysis equivalently applies the winding tension through the thermal strain of the carbon fiber. This method does not change the material properties of the carbon fiber sheath, uses the interference amount between carbon fiber layers corresponding to the winding tension as the tension control variable, and obtains the convergent interference amount parameters during the winding process through analytical iterative calculation. The distribution result of the thermal stress generated by the carbon fiber itself due to temperature influence is considered through finite element analysis, shortening the time required for rotor stress analysis and improving the stress calculation accuracy of the rotor assembly under thermal conditions.

[0049] 2. Through the established analytical iterative analysis process of interference amount and stress, according to different winding methods, the convergent calculation of the interference amount can be quickly realized, thus avoiding the direct iteration of the interference amount between carbon fiber layers in finite element analysis and improving the calculation speed on the premise of maintaining the rotor stress calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as any limitation to the present invention. In the drawings:

[0051] Figure 1 It is a schematic diagram of the two-dimensional structure of the surface-mounted high-speed permanent magnet rotor with carbon fiber winding of the present invention;

[0052] Figure 2 It is a schematic diagram of the structural parameters and physical boundary conditions of the high-speed permanent magnet rotor with carbon fiber winding of the present invention;

[0053] Figure 3 It is a schematic diagram of the simulation principle of the carbon fiber winding process of the surface-mounted high-speed permanent magnet rotor of the present invention;

[0054] Figure 4 It is a flow chart of the layer-by-layer iterative analysis of the interference amount parameters in the carbon fiber winding simulation of the present invention;

[0055] Figure 5 It is a global iterative flow chart of the interference amount between carbon fiber layers in the carbon fiber winding simulation of the present invention;

[0056] Figure 6 It is a model diagram of the mesh division of the permanent magnet rotor of the present invention;

[0057] Figure 7It is the finite element time sequence flow chart for the strength analysis of the carbon fiber wound high-speed permanent magnet rotor of the present invention;

[0058] Figure 8 It is the schematic diagram of the winding stress distribution of each layer of carbon fiber after winding under the given initial interference of the carbon fiber of the present invention;

[0059] Figure 9 It is the change of the winding stress of the fiber layer with the number of iterations after winding under equal winding tension of the present invention;

[0060] Figure 10 It is the schematic diagram of the change of the interference between carbon fiber layers with the number of iterations under equal winding tension of the present invention;

[0061] Figure 11 It is the diagram of the change relationship of the circumferential stress of carbon fiber with the number of winding layers under the given initial interference in the present invention; where (a) is the analytical iterative calculation result and (b) is the finite element direct calculation result;

[0062] Figure 12 It is the diagram of the change relationship of the circumferential stress of carbon fiber with the number of winding layers under equal winding tension in the present invention; where (a) is the analytical iterative calculation result and (b) is the finite element direct calculation result;

[0063] Figure 13 It is the diagram of the distribution of the residual stress of the fiber layer under the given initial interference under equal residual stress winding in the present invention;

[0064] Figure 14 It is the diagram of the change of the residual stress of the fiber layer during the iteration process under equal residual stress winding in the present invention;

[0065] Figure 15 It is the diagram of the change of the residual stress of the fiber layer with the number of winding layers under equal residual stress winding in the present invention, where (a) is the analytical iterative calculation result and (b) is the finite element direct calculation result;

[0066] Figure 16 It is the diagram of the change of the compressive stress of the permanent magnet with the number of winding layers under equal residual stress winding in the present invention. Specific embodiments

[0067] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0068] An embodiment of the present invention provides a method for simulating and analyzing the strength of a surface-mounted permanent magnet rotor with carbon fiber winding. The permanent magnet rotor applicable to this method includes: a rotor core, surface-mounted permanent magnets, and a multi-layer wound carbon fiber sheath, as Figure 1 shown. Among them, the rotor core is made of high-strength alloy steel material with good magnetic conductivity, and the surface-mounted permanent magnets are made of rare earth permanent magnet materials, and are in a circumferentially segmented structure in this embodiment.

[0069] The winding simulation and strength analysis method includes the following steps:

[0070] S1: Establish an analytical model of the interference amount and stress of the carbon fiber layer;

[0071] The specific implementation is as follows:

[0072] Unfold the permanent magnet rotor along the polar coordinates to form a plane analysis model, as Figure 2 shown. The unfolded rotor structure has a total of n + 2 layers. The innermost layer is the rotor core, the outside of the rotor core is the permanent magnet, the outside of the permanent magnet is the carbon fiber sheath, and there are n layers of carbon fiber sheaths. The carbon fiber layers are numbered from 1 to n from the inside to the outside.

[0073] According to the physical properties, the following constraint conditions exist for each component of the rotor:

[0074]

[0075] Among them, ε ρ is the radial strain; is the circumferential strain; σ ρ is the radial stress; is the circumferential stress; E ρ is the elastic modulus of the material along the radial direction, is the elastic modulus of the material along the circumferential direction; is the circumferential Poisson's ratio, indicating the influence of the circumferential strain of the material on the radial strain; is the radial Poisson's ratio, indicating the influence of the radial strain of the material on the circumferential strain.

[0076] In polar coordinates, each component of the rotor satisfies the equilibrium differential equation during the winding process:

[0077]

[0078] Among them, ρ represents the radius.

[0079] According to the small deformation theory, the geometric equation of each component of the rotor is obtained as:

[0080]

[0081] Among them, u represents the radial displacement of each component of the rotor at the radius ρ.

[0082] Combining equations (1)-(3) and considering the material properties of each component of the rotor, the expressions for the radial displacements of each component of the rotor are obtained as follows:

[0083] u = C1ρ η + C2ρ -η (4)

[0084] where C1 and C2 are both unknown coefficients.

[0085] The radial and circumferential stresses of each component of the rotor are:

[0086]

[0087] In the formula:

[0088] Let the contact pressures of each contact surface of the permanent magnet rotor be set as p1 to p n+1 from the inside to the outside, and the contact pressures between the inner surface of the rotor core, the outer surface of the outermost layer of carbon fiber and the air are regarded as 0.

[0089] From the standard form of the stress expression of each component of the rotor, that is, formula (5), the expression of the radial stress in the rotor core is written as:

[0090]

[0091] where the subscript core represents the rotor core; C 1(core) 、C 2(core) are the unknown coefficients to be solved in the stress equation of the rotor core; D 1(core) 、D 2(core) are the coefficients related to the material properties of the rotor core; R si is the inner radius of the rotor core, and R so is the outer radius of the rotor core. At this time, the unknown coefficients C 1(core) and C 2(core) can be expressed in terms of the contact pressure.

[0092] Similarly, for the permanent magnet, the radial stress at its contact surfaces with the rotor core and carbon fiber is expressed as:

[0093]

[0094] where the subscript pm represents the permanent magnet; C 1(pm) 、C 2(pm) are the unknown coefficients to be solved in the stress equation of the permanent magnet; D 1(pm) 、D 2(pm) are the coefficients related to the material properties of the permanent magnet; R mi is the inner radius of the permanent magnet, and Rmo is the outer radius of the permanent magnet.

[0095] The radial stress of the first layer of carbon fiber at the contact boundary is expressed as:

[0096]

[0097] where the subscript cf1 represents the first layer of carbon fiber; C 1(cf1) 、C 2(cf1) are the unknown coefficients to be solved in the stress equation of the first layer of carbon fiber; D 1(cf1) 、D 2(cf1) are the coefficients related to the properties of the carbon fiber material; R s(1) is the inner radius in polar coordinates of the first layer of carbon fiber; d is the thickness of the carbon fiber layer.

[0098] The radial stress of the i-th layer of carbon fiber at the contact boundary is expressed as:

[0099]

[0100] where the subscript cfi represents the i-th layer of carbon fiber; C 1(cfi) 、C 2(cfi) are the unknown coefficients to be solved in the stress equation of the i-th layer of carbon fiber; D 1(cfi) 、D 2(cfi) are the coefficients related to the properties of the carbon fiber material; R s(i) is the inner radius in polar coordinates of the i-th layer of carbon fiber.

[0101] The radial stress of the n-th layer of carbon fiber at the contact boundary is expressed as:

[0102]

[0103] where the subscript cfn represents the n-th layer of carbon fiber; C 1(cfn) 、C 2(cfn) are the unknown coefficients to be solved in the stress equation of the n-th layer of carbon fiber; D 1(cfn) 、D 2(cfn) are the coefficients related to the properties of the carbon fiber material; R s(n) is the inner radius in polar coordinates of the n-th layer of carbon fiber;

[0104] Formulas (6)-(15) constitute the pressure constraint equations between the contact surfaces of the various components of the rotor.

[0105] Since there is no interference between the rotor core and the permanent magnet, while there is interference between the permanent magnet and the carbon fiber and the carbon fiber layer, during the actual winding process of the rotor, the displacement constraint equations between the various components are as follows:

[0106]

[0107] Among them, the subscript i of R represents the inner radius, the subscript o of R represents the outer radius, the subscript s of R represents the rotor core, the subscript m of R represents the permanent magnet, and the subscript s (i) represents the i-th layer of carbon fiber layer; δ (i) represents the interference of the i-th layer of carbon fiber layer;

[0108] It can be known that is the radial displacement of the outer radius of the rotor core, is the radial displacement of the inner radius of the permanent magnet, is the radial displacement of the inner radius of the i-th layer of carbon fiber layer.

[0109] Combining the displacement constraint equation and the pressure constraint equation, the unknown coefficients in the stress expression can be solved, so as to realize the accurate calculation of the stress during the carbon fiber winding process.

[0110] S2: Substitute the initial interference into the analytical model of the interference and stress of the carbon fiber layer to realize the analytical iteration of the equivalent simulation of the carbon fiber winding tension, and obtain the converged interference;

[0111] The winding process of the carbon fiber is as Figure 3 shown. In the initial stage of rotor winding, there are only the rotor core and the rotor permanent magnet. When starting to wind, the interference of the contact surface between the first layer of carbon fiber and the rotor permanent magnet is applied. At this time, the number of contact pressures in the pressure constraint equation is 2, and the number of displacement constraint equations is equal to the number of contact pressures. By calculating the pressure constraint and displacement constraint of the above three-layer rotor structure, the equivalent simulation of the winding of the first layer of carbon fiber can be realized. By analogy, when winding the i-th layer of carbon fiber, there are i + 1 pressure constraint equations and i + 1 displacement constraint equations. By calculating the i + 1 pressure constraint equations and displacement digit equations, the winding simulation process of the i-th layer of carbon fiber can be realized. By analogy, until all the n-th layer of carbon fiber is wound.

[0112] The specific process is as follows:

[0113] S201: Specify the rotor structure parameters and material parameters to be wound;

[0114] S202: Specify the initial interference of each layer of carbon fiber;

[0115] S203: Based on the given initial interference, combined with the pressure boundary conditions and displacement constraint conditions of each component of the rotor, according to the analytical model of the interference and stress of the carbon fiber layer, calculate the stress of each part of the rotor; and extract the winding stress and residual stress of each layer of carbon fiber during the initial calculation;

[0116] S204: Determine the winding method of the carbon fiber, and the winding method includes equal winding tension and equal residual stress;

[0117] S205: Determine the iteration method, which includes the layer-by-layer iteration method and the global iteration method; according to the iteration method, apply the initial interference amount to the analytical model of the interference amount and stress of the carbon fiber layer for iterative calculation to obtain the interference amount with iterative convergence.

[0118] Optionally, in the equal winding tension mode, the flow chart of the layer-by-layer iterative calculation of the interference amount is as Figure 4 shown. It includes the following steps:

[0119] 1) Specify the material parameters and structural parameters of each component of the rotor;

[0120] 2) Specify the winding parameter N of the carbon fiber and set the initial winding layer number to 0;

[0121] 3) Prepare to wind the first layer, i = 1, and at the same time set the iteration number k to 1;

[0122] 4) Specify the interference amount δ (i) | k for the current winding layer, and at the same time specify the winding stress σ ωN(i) of the current winding layer;

[0123] 5) Combine all the contact pressure equations and displacement constraint equations including the current winding layer, and according to the analytical model of the interference amount and stress of the carbon fiber layer, calculate the winding stress σ ω(i) | k of each layer of carbon fiber under the current given interference amount;

[0124] The pressure constraint is:

[0125] P (2i+4)×1 = G (2i+4)×(2i+4) C (2i+4)×1 (17)

[0126] where the matrix P represents the contact pressure matrix related to the contact surface pressure of each component in the rotor, the matrix G represents the coefficient matrix related to the geometric parameters and material parameters of the rotor, and the matrix C is the coefficient matrix to be solved;

[0127] The displacement constraint is:

[0128] u| Rso = u| Rmo , u| Rhi(1) - u| Rmo = δ (1) | k ...u| Rhi(i) - u| Rhi(i-1) = δ (i) | k (18)

[0129] 6) Compare the winding stress σ calculated for the current winding layer ω(i) | k with the specified winding stress σ ωN(i) of the current layer for the relative error Δσ ω(i) | k , where Δσ w(i) | k = abs(σ w(i) | k -σ wN(i) ), and determine whether the ratio of the relative error Δσ ω(i) | k to the specified winding stress σ ωN(i) of the current layer meets the convergence criterion. ξ is a user-defined convergence criterion, i.e., Δσ w(i) | k / σ wN(i) ≤ ξ; if the convergence criterion is met, determine whether the current winding layer is the last layer. If it is the last layer, the winding is completed; otherwise, continue winding the next layer; if the convergence criterion is not met, proceed to step 7);

[0130] 7) Increase the iteration count k, i.e., set k = k + 1; update the interference δ (i) | k = (Δσ w(i) | k-1 / K (i) ) + δ (i) | k-1 calculated in the previous iteration, where Δσ (i) | k is the difference between the winding stress σ ω(i) | k-1 calculated for the current winding layer and the specified winding stress σ ω(i) | k-1 , δ ωN(i) | (i) | k-1 is the interference of the current winding layer in the previous iteration calculation, and K (i) = (σ w(i) | k＝1 ) / (δ (i) | k＝1 ), and return to step 4);

[0131] The above layer-by-layer iteration method can implement the winding simulation process of carbon fiber under equal winding tension. When winding under equal winding tension, the winding tension is converted into winding stress.

[0132] At the initial winding, for simplicity of calculation, the same interlayer interference δ (i) | k＝1。The initial winding simulates the carbon fiber winding process under the given initial interference condition, aiming to calculate the carbon fiber winding stress corresponding to the initial interference, similar to initializing the rotor stress field. After the initial winding is completed, the winding stress distribution σ of the carbon fiber ω(i) | k＝1 is shown schematically as Figure 8 shown. During the carbon fiber winding process, the inner layer component is extruded by the carbon fiber winding stress and generates a contraction effect inward along the radial direction, resulting in the interlayer interference of each layer of carbon fiber being lower than the specified initial interference, and further leading to the winding stress σ ω(i) | k＝1 being lower than the specified winding stress σ ωN(i) , and the winding stress of the carbon fiber will gradually decrease as the number of winding layers increases.

[0133] During the iterative process, the variation process of the winding stress σ ω(i) | k of the carbon fiber layer with the number of iterations k is shown schematically as Figure 9 shown. When k = 1, the interlayer interference of the carbon fiber is the initially given value δ (i) | k＝1 ; as k continuously increases, the winding stress σ ω(i) | k＝i of the carbon fiber gradually approaches the specified winding stress σ ωN(i) . When k = s, s represents the number of times when the final iteration is completed, indicating that the specified tension winding simulation has been completed. At this time, as the iterative process progresses step by step, the variation process of the interlayer interference of the carbon fiber layer inside the rotor under different numbers of iterations is as Figure 10 shown. To compensate for the compression effect caused by the current winding layer on the inner rotor component of this layer during the carbon fiber layer winding process, when the winding iterative process converges, the interference of the carbon fiber layer gradually increases from the inside to the outside, so as to ensure that the outer layer carbon fiber has the same winding tension as the inner layer carbon fiber. Iterative winding needs to carry out the iteration of the interference on the basis of the initial winding, which belongs to the accurate calculation of the rotor winding stress.

[0134] The finite element analysis model of the rotor strength is as Figure 6 shown. The magnetization method of the 4-pole permanent magnet rotor is Halbach. The 1 / 4 analysis model is established as the minimum analysis unit. Considering that the permanent magnet has different linear expansion coefficients in the magnetization parallel and magnetization perpendicular directions, it is necessary to establish a local coordinate system of the permanent magnet for analysis. All structural finite element analyses adopt quadrilateral meshes and co-node divisions, and the mesh independence is verified.

[0135] During the initial winding, the circumferential stress change of the carbon fiber is obtained through the above analytical iterative method and the finite element direct analysis method as Figure 11As shown. The direct finite element analysis method is a method that directly performs finite element simulation without the above-mentioned analytical iteration. It can be seen that the analytical iteration method and the direct finite element analysis method have almost the same calculation results, which demonstrates the accuracy of the analytical iteration method. At the same time, the inner components of the rotor will shrink inward under the influence of the stress of the outer carbon fiber winding, and the winding stress gradually decreases as the number of winding layers gradually increases.

[0136] When the winding tension is constant, the circumferential stress distribution results of carbon fiber obtained by the analytical iteration method and the direct finite element analysis method are as Figure 12 shown. The results can also illustrate the accuracy and effectiveness of the simulation process of carbon fiber winding in the present invention.

[0137] Optionally, the global iterative calculation process of the interference amount is as Figure 5 shown. It includes the following steps:

[0138] 1) Specify the rotor parameters, including the material parameters of each component, the number of carbon fiber winding layers N, and the geometric structure parameters;

[0139] 2) Prepare for winding and set the iteration number k = 1;

[0140] 3) Given the virtual interference amount δ (i) of the current winding layer;

[0141] 4) According to the analytical model of the interference amount and stress of the carbon fiber layer, calculate the pressure constraint equation and displacement constraint equation corresponding to the current winding layer, and obtain the pressure distribution and stress distribution inside the current rotor;

[0142] 5) Extract the winding stress σ ω (k) of the carbon fiber after the calculation of the current winding layer, and determine whether the current winding layer i is the last layer; if it is the last layer, go to step 6); if it is not the last layer, prepare for winding the next layer and return to step 3)

[0143] 6) Extract the residual stress σ re (k) of the carbon fiber layer after all carbon fiber layers are wound, and specify the carbon fiber winding form, which is divided into specifying the winding stress σ ωN and specifying the residual stress σ reN after winding; if it is to specify the winding stress σ ωN , then go to step 7); if it is to specify the residual stress distribution σ reN after winding, then go to step 8);

[0144] 7) Compare the difference Δσ ω (k) between the winding stress σ ωN obtained in step 5) and the specified winding stress σ ω (k), where Δσω (k) = max: abs[σ wN - σ w (k)] / σ wN , representing the maximum relative error of stress in all winding layers, and judging whether the difference Δσ ω (k) meets the convergence criterion. ξ is a user-defined convergence criterion, that is, Δσ w (k) ≤ ξ. If it is satisfied, it means that the winding simulation is completed, and the interference amount δ after the current winding is output (i) as the final output parameter; if it does not meet the requirements, then according to the calculated difference Δσ ω (k), the interference amount δ between carbon fiber layers (i) is updated, δ(i) = Δσ w (k) / K1 + δ(i), where K1 = [σ w (1)| k＝1 / (δ(1)| k＝1 ). Increase the iteration number k, let k = k + 1, and return to step 3);

[0145] 8) Compare the difference Δσ re (k) between the residual stress σ reN obtained in step 6) and the specified residual stress σ re (k), where Δσ re (k) = max: abs[σ reN - σ re (k)] / σ reN , representing the maximum relative error of residual stress in all winding layers, and judging whether the difference meets the convergence criterion ξ. ξ is a user-defined convergence criterion, that is, Δσ re (k) ≤ ξ; if the convergence requirement is met, it means that the winding is completed, and the interference amount δ after the current winding is output (i) as the final output parameter; if the winding requirement is not met, then based on the difference Δσ re (k) between the residual stress σ reN after the winding is completed and the specified residual stress σ re (k), the interference amount between carbon fiber layers is updated, δ(i) = Δσ re (k) / K2 + δ(i), where K2 = [σ re (1)| k＝1 / (δ(1)| k＝1 ). Increase the iteration number k, let k = k + 1, and return to step 3).

[0146] The global iterative calculation process takes the interference amount δ after the current winding is completed (i)As the final output parameter, since the interference amount corresponds to the winding stress, the winding tension of carbon fiber can be obtained based on the analytical model of the interference amount and stress.

[0147] When the winding method is equal residual stress, a given equal initial interference amount δ (i) | k＝1 , the residual stress distribution σ of each layer of carbon fiber re(i) | k＝1 such as Figure 13 shown. Affected by the winding stress of the outer layer of carbon fiber, the residual stress of the inner layer of carbon fiber will gradually decrease as the number of winding layers increases, that is, the distribution of the residual stress of the carbon fiber layer shows the characteristic of the smallest in the inner layer and the largest in the outer layer. As the iterative calculation progresses, the residual stress of the carbon fiber layer will gradually approach the specified residual stress distribution until the difference Δσ re(i) | k meets the convergence criterion. During the equal residual stress winding process, the residual stress σ of the carbon fiber layer re(i) | k changes with the number of iterations k as shown in Figure 14 shown. As the number of iterations k increases, the residual stress σ of the carbon fiber layer re(i) | k will gradually approach the specified residual stress σ reN . When the number of iterations is s, s represents the number of iterations required for final convergence, and the residual stress σ of the carbon fiber layer re(i) | k＝s is almost equal to the specified residual stress σ reN , thus realizing the simulation of the equal residual stress winding process of carbon fiber.

[0148] The circumferential stress distribution results of carbon fiber under equal residual stress winding obtained by analytical iteration and finite element direct analysis are shown in Figure 15 shown. After the equal residual stress winding is completed, it is an equal residual stress distribution, and it is 1000 Mpa. It can be seen from the results that when the carbon fiber winding is completed, the residual stress of all layers is 1000 Mpa, meeting the winding requirements. In addition, during the equal residual stress winding process, the change of the internal compressive stress in the permanent magnet with the number of carbon fiber winding layers is shown in Figure 16 shown. As the number of winding layers gradually increases, the compressive stress borne by the permanent magnet gradually increases, and the increasing slope gradually decreases as the number of winding layers increases. The carbon fiber winding simulation analysis method proposed by the present invention reflects the phenomenon of stress saturation of the permanent magnet compressive stress as the number of winding layers gradually increases, and further reveals the change law of the permanent magnet stress during the carbon fiber winding process.

[0149] S3: Use the interference amount with iterative convergence as the interference amount of each contact surface of the rotor in finite element analysis, and perform stress time series analysis under different working conditions of the rotor, such asFigure 7 as shown

[0150] The specific process is as follows:

[0151] S301: Apply the interference amount that converges in iteration to the model for finite element analysis;

[0152] S302: Add a contact control condition to each layer of carbon fiber layer, corresponding numbers are from 1 to N, and the number of numbers is the same as the layer number of carbon fiber; at the initial moment, each layer of contact control is suppressed; when starting winding, only activate the contact of the first layer; when starting to wind the second layer, keep the contact of the first layer unchanged and activate the contact of the second layer; when starting to wind the third layer, keep the contacts of the first and second layers unchanged and activate the third layer; and so on, until the contact of the last layer is activated, indicating that the calculation of the carbon fiber winding process is completed;

[0153] S303: After the winding of the Nth layer of carbon fiber is completed, apply rotational speed and temperature to each component of the rotor, and calculate the stress distribution of the rotor considering the influence of rotational speed and temperature. The application of rotational speed and temperature conditions must be after the carbon fiber winding is completed, and the application of rotational speed and temperature conditions has no order, and can be applied separately or simultaneously, representing three different working conditions of normal temperature overspeed, hot state overspeed, and hot state static according to different combination forms.

[0154] The present invention will analyze and iteratively calculate to obtain the interference amount parameter that converges during the winding process, and consider the thermal stress distribution result generated by the carbon fiber itself affected by temperature through finite element analysis, shortening the time required for rotor stress analysis and improving the stress calculation accuracy of the rotor assembly under hot state working conditions.

[0155] In the embodiments provided by the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor of the present invention, the functional units in each step can be integrated in a controller processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware, or in the form of hardware plus software functional units. The above-mentioned integrated units implemented in the form of software functional units can be stored in a computer-readable storage medium. The above-mentioned software functional units are stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute part of the steps of the method described in each embodiment of the present invention. And the foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0156] The present invention also discloses a carbon fiber winding simulation and strength analysis system for a surface-mounted permanent magnet rotor, comprising: at least one processor; and at least one memory communicatively connected to the processor, wherein: the memory stores program instructions executable by the processor, and the processor can execute the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor of the present invention as described above by invoking the program instructions.

[0157] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A method for simulating and analyzing the strength of a surface-mounted permanent magnet rotor by carbon fiber winding, characterized in that The winding simulation and strength analysis method includes the following steps: S1: Establish an analytical model of the interference amount and stress of the carbon fiber layer; specifically including: 1) Expand the permanent magnet rotor along the polar coordinates to form a plane analysis model; 2) Obtain the displacement, radial stress, and circumferential stress expressions of each component of the rotor according to the physical properties, geometric properties, and equilibrium differential equations of each component of the rotor; 3) Combine the contact surface pressure constraint and the interference amount-displacement constraint to solve the unknown coefficients in the displacement, radial stress, and circumferential stress expressions, and then realize the calculation of stress; S2: Substitute the initial interference amount into the analytical model of the interference amount and stress of the carbon fiber layer to realize the analytical iteration of the equivalent simulation of the carbon fiber winding tension, and obtain the interference amount with iterative convergence; specifically including the following steps: S201: Specify the rotor structure parameters and material parameters to be wound; S202: Specify the initial interference amount of each layer of carbon fiber; S203: Based on the given initial interference amount, combine the pressure boundary conditions and displacement constraint conditions of each component of the rotor, and calculate the stress of each part of the rotor according to the analytical model of the interference amount and stress of the carbon fiber layer; and extract the winding stress and residual stress of each layer of carbon fiber during the initial calculation; S204: Determine the winding method of the carbon fiber, and the winding method includes equal winding tension and equal residual stress; S205: Determine the iteration method, and the iteration method includes the layer-by-layer iteration method and the global iteration method; according to the iteration method, apply the initial interference amount to the analytical model of the interference amount and stress of the carbon fiber layer for iterative calculation to obtain the interference amount with iterative convergence; S3: Use the interference amount with iterative convergence as the interference amount of each contact surface of the rotor in the finite element analysis to perform stress time series analysis under different working conditions of the rotor.

2. The winding simulation and strength analysis method according to claim 1, characterized in that The layer-by-layer iteration method of the equal winding tension method in step S205 includes: 1) Specify the material parameters and structure parameters of each component of the rotor; 2) Specify the winding parameter N of the carbon fiber and set the initial winding layer number to 0; 3) Prepare to wind the first layer, i = 1, and at the same time set the iteration number k to 1; 4) Specify the interference amount δ for the current winding layer (i) | k , and at the same time specify the winding stress σ of the current winding layer ωN(i) ; 5) Combine all the contact pressure equations and displacement constraint equations including the current winding layer, and calculate the winding stress σ of each carbon fiber layer at the current given interference amount according to the analytical model of the interference amount and stress of the carbon fiber layer ω(i) | k ; 6) Compare the winding stress σ calculated for the current winding layer ω(i) | k with the specified winding stress σ ωN(i) of the current layer to obtain the relative error Δσ ω(i) | k , where Δσ w(i) | k = abs(σ w(i) | k - σ wN(i) ). Then, judge whether the ratio of the relative error Δσ ω(i) | k to the specified winding stress σ ωN(i) of the current layer meets the convergence criterion. ξ is a user-defined convergence criterion, that is, Δσ w(i) | k / σ wN(i) ≤ ξ. If the convergence criterion is met, judge whether the current winding layer is the last layer. If it is the last layer, the winding is completed; otherwise, continue to wind the next layer. If the convergence criterion is not met, go to step 7); 7) Increase the number of iterations k, i.e., let k = k + 1; according to the formula δ (i) | k =(Δσ w(i) | k-1 / K (i) )+δ (i) | k-1 Update the interference δ (i) | k , where Δσ ω(i) | k-1 is the difference between the winding stress σ ω(i) | k-1 calculated in the current winding layer and the specified winding stress σ ωN(i) , δ (i) | k-1 is the interference of the current winding layer in the previous iteration calculation, K (i) =(σ w(i) | k＝1 ) / (δ (i) | k＝1 ), and return to step 4).

3. The winding simulation and strength analysis method according to claim 1, characterized in that The global iteration method in step S205 includes: 1) Specify the rotor parameters, including the material parameters of each component, the carbon fiber winding layer number N, and the geometric structure parameters; 2) Prepare to wind and set the iteration number to k = 1; 3) Given the virtual interference δ of the current winding layer (i) ; 4) According to the analytical model of the interference amount and stress of the carbon fiber layer, calculate the pressure constraint equation and displacement constraint equation corresponding to the current winding layer, and obtain the pressure distribution and stress distribution inside the current rotor; 5) Extract the winding stress σ ω (k) of the carbon fiber after the current winding layer is calculated, and determine whether the current winding layer i is the last layer; if it is the last layer, go to step 6); if it is not the last layer, prepare to wind the next layer and return to step 3); 6) Extract the residual stress σ re (k) of the carbon fiber layers after all carbon fiber layers are wound, and specify the carbon fiber winding form, which is divided into specifying the winding stress σ ωN and the residual stress σ reN after winding is completed; if it is the specified winding stress σ ωN , then go to step 7); if it is the specified residual stress distribution σ reN after winding is completed, then go to step 8); 7) Compare the winding stress σ ω (k) obtained in step 5) with the specified winding stress σ ωN to get the difference Δσ ω (k), where Δσ ω (k) = max:abs[σ wN - σ w (k)] / σ wN , representing the maximum relative stress error among all winding layers, and determine whether the difference Δσ ω (k) meets the convergence criterion ξ, where ξ is a user-defined convergence criterion, i.e., Δσ w (k) ≤ ξ. If it is satisfied, it means the winding simulation is completed, and the interference δ (i) after the current winding is output as the final output parameter; if not, update the interference δ ω between carbon fiber layers according to the calculated difference Δσ (i) , δ(i) = Δσ w (k) / K1 + δ(i), where K1 = [σ w (1)| k＝1 / (δ(1)| k＝1 ). Increase the iteration number k by setting k = k + 1, and go back to step 3); 8) Compare the residual stress σ re (k) obtained in step 6) with the specified residual stress σ reN to obtain the difference Δσ re (k), where Δσ re (k) = max: abs[σ reN - σ re (k)] / σ reN , which represents the maximum relative error of the residual stress in all winding layers, and determine whether the difference meets the convergence criterion ξ. ξ is a user-defined convergence criterion, that is, Δσ re (k) ≤ ξ; if the convergence requirement is met, it means that the winding is completed, and the current interference δ (i) is output as the final output parameter; if the winding requirement is not met, the interference between layers of carbon fiber is updated based on the difference Δσ re (k) between the residual stress σ reN after winding and the specified residual stress σ re , δ(i) = Δσ re (k) / K2 + δ(i), where K2 = [σ re (1)| k＝1 / (δ(1)| k＝1 ), increase the iteration number k, let k = k + 1, and return to step 3).

4. The winding simulation and strength analysis method according to claim 1, wherein S3 including: S301: Apply the interference amount with iterative convergence to the model of the finite element analysis; S302: Add a contact control condition to each layer of carbon fiber layer, corresponding numbers are from 1 to N, and the number is the same as the layer number of the carbon fiber; at the initial moment, each layer of contact control is suppressed; when starting to wind, only activate the contact of the first layer; when starting to wind the second layer, keep the contact of the first layer unchanged and activate the contact of the second layer; when starting to wind the third layer, keep the contacts of the first and second layers unchanged and activate the third layer; and so on until the contact of the last layer is activated, indicating that the calculation of the carbon fiber winding process is completed; S303: After the carbon fiber winding of the Nth layer is completed, rotational speed and temperature are applied to each component of the rotor, and the stress distribution of the rotor considering the influence of rotational speed and temperature is calculated. The application of rotational speed and temperature conditions must be carried out after the carbon fiber winding is completed, and there is no order for the application of rotational speed and temperature conditions. According to different combinations of rotational speed and temperature, it is divided into three different working conditions: normal temperature overspeed, hot state overspeed, and hot state static.

5. The winding simulation and strength analysis method according to claim 1, characterized in that The permanent magnet rotor to which the winding simulation and strength analysis method is applicable includes: a rotor core, a surface-mounted permanent magnet, and a multi-layer wound carbon fiber sheath.

6. A carbon fiber winding simulation and strength analysis system for a surface-mounted permanent magnet rotor, characterized in that, including: at least one processor; and at least one memory communicatively connected to the processor, wherein: the memory stores program instructions executable by the processor, and the processor can execute the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor according to any one of claims 1 to 5 by invoking the program instructions.

7. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the carbon fiber winding simulation and strength analysis method for the surface-mounted permanent magnet rotor according to any one of claims 1 to 5.

Images