Rotor, magnetizing device, servo motor and structural parameter optimization method thereof

Abstract

The application belongs to the technical field of permanent magnet servo motors, and specifically discloses a rotor, a magnetizing equipment, a servo motor and a structural parameter optimization method. According to the application, the whole magnetizing technology of magnetizing after assembling the magnetic steel is adopted, the non-magnetized permanent magnet block is assembled to the rotor, and the whole rotor is magnetized through the pulse strong magnetic field equipment, so that the assembly difficulty is reduced, and the assembly precision is improved. In the case of the same permanent magnet consumption, better performance than the traditional servo motor adopting the Halbach array can be obtained, and the servo motor is easy to process and manufacture. Based on the optimization result of the theoretical model, the finite element method is used for more accurate optimization, and better design parameters than the Halbach array are obtained. Under the premise of the unchanged permanent magnet consumption, the torque of the discrete magnetizing permanent magnet motor is significantly improved, and the torque ripple is significantly reduced, so that the discrete magnetizing permanent magnet motor has greater competitiveness in the servo motor field or more occasions, and is expected to become a lower-cost alternative solution of the permanent magnet motor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of permanent magnet servo motors, and more particularly relates to a rotor, a magnetizing device, a servo motor and a structural parameter optimization method thereof. BACKGROUND

[0002] A servo motor is the most core functional unit in intelligent manufacturing equipment and plays a key role in the performance and reliability of advanced manufacturing equipment. The performance of a servo motor is mainly determined by torque density, torque quality and vibration noise.

[0003] In existing research, a servo motor mainly adopts a bread-type magnetic pole, a spoke-type magnetic pole or a Halbach array design. The bread-type magnetic pole is generally difficult to process and wastes permanent magnet material during processing. The spoke-type magnetic pole is difficult to control the torque quality of the motor. The Halbach array has advantages such as sinusoidal magnetic field distribution, self-shielding effect, high fundamental field and low harmonic content, and is widely used in the field of servo motors. However, the torque quality of the motor designed by using the Halbach array is high, but there is still room for improvement. SUMMARY

[0004] In view of the defects of the prior art, the purpose of the application is to provide a rotor, a magnetizing device, a servo motor and a structural parameter optimization method thereof, aiming to solve the problems of low torque density, high torque ripple of existing servo motors, and low assembly precision and high assembly difficulty of traditional pre-magnetizing technology.

[0005] To achieve the above-mentioned purpose, in a first aspect, the application provides a rotor, comprising: a rotor core and a magnetic steel, the rotor core is provided with a plurality of poles along its circumferential surface, each pole is composed of a plurality of magnetic steels, and the magnetic steels of different poles are combined in the same way; at least two magnetic steels under the same pole have different central angles; the magnetization directions of all magnetic steels under the same pole are different, and the magnetization direction of at least one magnetic steel is radial.

[0006] Preferably, when the plurality of magnetic steels under the same pole are of a symmetrical structure, the magnetization direction of the magnetic steel with a symmetrical structure is asymmetric.

[0007] Preferably, when the magnetization directions of the plurality of magnetic steels under the same pole are symmetrical, the central angles of the magnetic steels with symmetrical magnetization directions are different.

[0008] Preferably, the magnetization directions of the magnetic steels with radial magnetization directions in adjacent poles are opposite, and the magnetic steels at the same position of adjacent poles have equal angles between the magnetization directions and the radial direction.

[0009] Preferably, the magnetic steel has anisotropy and is oriented in an optimized design magnetization direction in the manufacturing stage.

[0010] To achieve the above object, in a second aspect, the application provides a magnetizing device for magnetizing the rotor as described in the first aspect, the magnetizing device comprising: a plurality of coils, the number of which is the same as the number of pole pairs of the rotor; the plurality of coils being uniformly distributed in a circumferential direction; each coil being a symmetrical structure; and an inner hole diameter of the magnetizing device being larger than an outer diameter of the rotor.

[0011] Preferably, the coil is saddle-shaped.

[0012] Preferably, the magnetizing device further comprises a magnetic yoke; each coil is embedded in a groove of the magnetic yoke, and a median plane of each coil coincides with a median plane of the magnetic yoke.

[0013] To achieve the above object, in a third aspect, the application provides a servo motor comprising the rotor as described in the first aspect.

[0014] Preferably, the servo motor is an internal rotor motor or an external rotor motor.

[0015] To achieve the above object, in a fourth aspect, the application provides a structure parameter optimization method of the servo motor as described in the third aspect, comprising: calculating a residual magnetization vector of the servo motor at each moment based on a theoretical model; solving an electromagnetic torque of the servo motor at each moment according to a stator slot opening width and the residual magnetization vector at each moment; calculating an average value of the electromagnetic torque and a torque ripple according to the electromagnetic torque of the servo motor at each moment; changing a central angle coefficient and a magnetization angle of the magnetic steel and the stator slot opening width, repeating the above steps until a Pareto optimal stop, and a corresponding structure parameter combination is the optimization result; and the theoretical model is specifically as follows:

[0016]

[0017] wherein, is a residual magnetization vector, n is a summation variable in a Fourier series expansion, taking values 1, 2, …, ∞, M rn is a radial component of the residual magnetization, M θn is a circumferential component of the residual magnetization, p is the number of pole pairs of the rotor, θ is an included angle between a circumferential position of an internal point of the magnetic steel and a center line of the magnetic steel with a magnetization direction being radially outward, is a radial unit vector, is a circumferential unit vector;

[0018]

[0019] wherein, B r is a residual magnetization of the magnetic steel, μ0 is a vacuum permeability, α i is a central angle of the i-th magnetic steel, γ i is an included angle between a center line of the i-th magnetic steel and a center line of the magnetic steel with a magnetization direction being radially outward, βi magnetization angle of the i-th block of magnetic steel, α i = a i α p , a i central angle coefficient of the i-th block of magnetic steel, α p polar distance angle, i = 1, 2, …, m, m is the number of blocks of each pole magnetic steel.

[0020] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0021] (1) The present application provides a rotor, comprising: a rotor core and a magnetic steel, the rotor core is provided with a plurality of poles along its circumferential surface, each pole is composed of a plurality of magnetic steels, and the magnetic steels of different poles are combined in the same way; at least two magnetic steels under the same pole have different central angles; the magnetization directions of all magnetic steels under the same pole are different, and the magnetization direction of at least one magnetic steel is radial. By using magnetic steels of different widths and discrete magnetization methods (the magnetization direction of each magnetic pole is discrete), the central angle and magnetization angle of each magnetic steel are variable. Compared with the existing rotor structure, the rotor proposed in the present application has more variable parameters, and can improve the torque performance as much as possible while keeping the amount of permanent magnet unchanged.

[0022] (2) The present application provides a magnetizing equipment for magnetizing the rotor, the magnetizing equipment comprises: a plurality of coils, the number of which is the same as the number of pole pairs of the rotor; the plurality of coils are uniformly distributed in the circumferential direction; each coil is a symmetrical structure; the inner diameter of the magnetizing equipment is larger than the outer diameter of the rotor. The present application adopts a whole magnetizing technology of assembling magnetic steels first and then magnetizing, assembles the non-magnetized permanent magnet blocks to the rotor, and magnetizes the whole rotor through a pulse strong magnetic field equipment, thereby reducing the assembly difficulty and improving the assembly precision.

[0023] (3) The present application provides a servo motor comprising the rotor. The present application can obtain better performance than the conventional servo motor using Halbach array under the same amount of permanent magnet, and is easy to process and manufacture.

[0024] (4) The application provides a structure parameter optimization method of the servo motor, comprising the following steps: calculating the residual magnetization intensity vector of the servo motor at each moment based on a theoretical model; solving the electromagnetic torque of the servo motor at each moment according to the stator slot opening width and the residual magnetization intensity vector at each moment; calculating the average torque and torque ripple of the electromagnetic torque according to the electromagnetic torque of the servo motor at each moment; changing the central angle coefficient and magnetization angle of the magnetic steel and the stator slot opening width, and repeating the above steps until the Pareto optimal stop, and the corresponding structure parameter combination is the optimization result. Based on the optimization result of the theoretical model, the finite element method is used for more accurate optimization, and more optimal design parameters than the Halbach array are obtained. Under the premise of constant permanent magnet consumption, the torque of the discrete magnetized permanent magnet motor is significantly improved, and the torque ripple is significantly reduced, so that the discrete magnetized permanent magnet motor has greater competitiveness in the field of servo motors or more occasions and is expected to become a lower-cost alternative solution for permanent magnet motors. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A magnetizing equipment structure schematic diagram is provided for the application.

[0026] Figure 2 A whole magnetizing technical flowchart is provided for the application.

[0027] Figure 3 A rotor magnetic steel circumferential expansion schematic diagram is provided for the application.

[0028] Figure 4 An inner rotor structure schematic diagram with a block number of 2 is provided for the application.

[0029] Figure 5 An inner rotor structure schematic diagram with a block number of 3 is provided for the application.

[0030] Figure 6 An inner rotor structure schematic diagram with a block number of 4 is provided for the application.

[0031] Figure 7 An outer rotor structure schematic diagram with a block number of 2 is provided for the application.

[0032] Figure 8 An optimization result is provided for the application.

[0033] Figure 9 A Halbach scheme and an optimization scheme torque comparison diagram is provided for the application. DETAILED DESCRIPTION

[0034] In order to make the purposes, technical schemes and advantages of the present application clearer, the present application will be further described in details below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0035] The term "and / or" used herein is a description of an association relationship between associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The symbol " / " used herein means that the associated objects are or, for example, A / B means A or B.

[0036] The terms "first" and "second" and the like in the description and claims herein are used to distinguish different objects, and are not used to describe a specific order of the objects. For example, the first response message and the second response message are used to distinguish different response messages, and are not used to describe a specific order of the response messages.

[0037] In the embodiments of the present application, the words "exemplary" or "for example" are used to mean serving as an example, instance, or illustration, any implementation or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or advantageous than other implementation or design solutions. Rather, the use of "exemplary" or "for example" is intended to present concepts in a concrete manner.

[0038] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more, for example, a plurality of processing units means two or more processing units, and the like; a plurality of elements means two or more elements, and the like.

[0039] Next, the technical solutions provided in the embodiments of the present application will be introduced.

[0040] In a first aspect, the present application provides a rotor, comprising: a rotor core and magnetic steels, the rotor core is provided with a plurality of poles along the circumferential surface thereof, each pole is composed of a plurality of magnetic steels, and the magnetic steels of different poles are combined in the same way; at least two magnetic steels under the same pole have different central angles; the magnetization directions of all the magnetic steels under the same pole are different, and the magnetization direction of at least one magnetic steel is radial.

[0041] Preferably, the number of blocks of the magnetic steels under each pole can be 2, 3, 4 or more.

[0042] Preferably, when the plurality of magnetic steels under the same pole are in a symmetrical structure, the magnetization direction of the magnetic steels in the symmetrical structure is asymmetric.

[0043] Preferably, when the magnetization directions of the plurality of magnetic steels under the same pole are symmetrical, the central angle of the magnetic steels in the magnetization direction symmetry is different.

[0044] Preferably, the magnetization directions of adjacent poles that are magnetized radially are opposite, and the magnetization directions of adjacent poles that are located at the same position are at the same angle to the radial direction.

[0045] Preferably, the magnet is anisotropic and is oriented according to an optimized magnetization direction during the manufacturing stage.

[0046] Traditional pre-magnetization technology for producing permanent magnet motors involves first applying a strong pulsed magnetic field to small, non-magnetic permanent magnet blocks using a small solenoid magnetizing coil to saturate them, and then embedding or attaching the magnetic permanent magnet blocks to the rotor to form the motor's magnetic poles. The magnetic permanent magnet blocks exhibit significant attractive or repulsive forces against each other, making assembly difficult and resulting in low precision.

[0047] Regarding the above issues, the second aspect is as follows: Figure 1 As shown, this application provides a magnetizing device for magnetizing a rotor as described in the first aspect. The magnetizing device includes: a plurality of coils, the number of which is the same as the number of pole pairs of the rotor; the plurality of coils are evenly distributed circumferentially; each coil has a symmetrical structure; and the inner diameter of the magnetizing device is larger than the outer diameter of the rotor.

[0048] Preferably, the coil is saddle-shaped.

[0049] The magnetizing device can be a coil with a yoke or a coil without a yoke.

[0050] Preferably, the magnetization device further includes a magnetic yoke; each coil is embedded in a groove of the magnetic yoke, and the mid-plane of the coil coincides with the mid-plane of the magnetic yoke. The magnetic yoke is made of stacked silicon steel sheets.

[0051] The magnetizing device of this application is a set of coils, with or without a yoke. The magnetizing device is used to magnetize permanent magnets. The number of coils is the same as the number of rotor pole pairs. The overall magnetizing process is as follows: Figure 2 As shown: Unmagnetized magnets and rotor cores are assembled. Then, the magnetizing device is placed in an area outside the outer surface of the rotor (inner rotor) or in an area inside the inner surface (outer rotor), with the center of each coil aligned with the N or S pole. A current of a certain magnitude is passed through the coils to generate a magnetic field capable of saturating and magnetizing the permanent magnet.

[0052] Thirdly, this application provides a servo motor, including: a rotor as described in the first aspect.

[0053] Preferably, the servo motor is an internal rotor motor or an external rotor motor.

[0054] Fourthly, this application provides a method for optimizing the structural parameters of a servo motor as described in the third aspect, comprising:

[0055] Based on the theoretical model, the residual magnetization vector of the servo motor at each moment is calculated;

[0056] According to the stator slot opening width of the servo motor and the residual magnetization vector at each moment, the electromagnetic torque of the servo motor at each moment is solved;

[0057] According to the electromagnetic torque of the servo motor at each moment, the average value of the electromagnetic torque, i.e. the average torque and the torque ripple, is calculated;

[0058] Change the central angle coefficient (corresponding to the central angle of the magnetic steel) and the magnetization angle of the magnetic steel and the stator slot opening width, repeat the above steps until the Pareto optimal stop, and the corresponding structure parameter combination is the optimization result;

[0059] The theoretical model is as follows:

[0060]

[0061] Wherein, is the residual magnetization vector, n is the summation variable in the Fourier series expansion, taking values 1, 2, …, ∞, M rn is the radial component of the residual magnetization, M θn is the circumferential component of the residual magnetization, p is the number of rotor pole pairs, θ is the angle between the circumferential position of a point inside the magnetic steel and the center line of the magnetic steel with the magnetization direction being radially outward, is the radial unit vector, is the circumferential unit vector. The rotor magnetic steel is developed along the ring direction, as shown in Figure 3 .

[0062]

[0063] Wherein, B r is the residual magnetization of the magnetic steel, η0 is the vacuum permeability, α i is the central angle of the i-th magnetic steel, γ i is the angle between the center line of the i-th magnetic steel and the center line of the magnetic steel with the magnetization direction being radially outward, β i is the magnetization angle of the i-th magnetic steel, α i =a i α p , a i is the central angle coefficient of the i-th magnetic steel, α p is the pole pitch angle, i = 1, 2, …, m, and m is the number of blocks per pole of the magnetic steel.

[0064] Example 1

[0065] As Figure 4As shown, the inner rotor is divided into two sections. The rotor core has four poles arranged along its circumferential surface, each pole consisting of two magnets, and the magnet combinations are the same for different poles. Figure 4 The central part of the circle represents one pole. The two magnets under the same pole have different central angles, 54° and 36° respectively. All magnets under the same pole have different magnetization angles; one magnetization angle is 0°, and the other magnetization angle is 110°.

[0066] Example 2

[0067] like Figure 5 As shown, the inner rotor is divided into 3 sections. The rotor core has 4 poles arranged along its circumferential surface, and each pole consists of 3 magnets. The magnets of different poles have the same combination. Figure 5 The central part of the circle represents one pole. Under the same pole, the three magnets have different central angles: 47.7°, 24.3°, and 18°. All magnetization angles under the same pole are different: the first magnet has a magnetization angle of 0°, the second magnet has a magnetization angle of 42°, and the third magnet has a magnetization angle of 147°.

[0068] Example 3

[0069] like Figure 6 As shown, the inner rotor is divided into 4 sections. The rotor core has 4 poles arranged along its circumferential surface, and each pole consists of 4 magnets. The magnet combinations are the same for different poles. Figure 6 The central section of the circle represents one pole. Under the same pole, the four magnets have different central angles: 52.2°, 11.7°, 15.75°, and 10.35°. All magnetization angles under the same pole are different: the first magnet has a magnetization angle of 0°, the second 42°, the third 106°, and the fourth 147°.

[0070] Example 4

[0071] like Figure 7 As shown, the outer rotor is divided into 2 sections. The rotor core has 42 poles arranged along its circumferential surface, and each pole consists of 2 magnets. The magnets of different poles have the same combination. Figure 7 The central part of the circle represents one pole. The two magnets under the same pole have different central angles: 6.51° and 2.06°. All magnets under the same pole have different magnetization angles: one magnetization angle is 0°, and the other magnetization angle is 130°.

[0072] Example 5

[0073] The main parameters of the motor involved in this embodiment are shown in Table 1.

[0074] Table 1 Main parameters of the motor

[0075] Parameter Value Stator outer diameter / mm 122.5 Stator inner diameter / mm 83 Stack length / mm 34 Stator slot number 12 Pole pair number 5 Air gap length / mm 0.7 Magnetic steel thickness / mm 3

[0076] For example, the optimization result of the analytical method for a discrete magnetization permanent magnet motor with an inner rotor and 4 magnet pieces per pole (m = 4) is shown in Table 1. Figure 8 It can be seen that the torque ripple of the optimization scheme is reduced compared with the Halbach scheme.

[0077] The parameters and performance of the analytical method optimization scheme and the Halbach scheme are compared, and the results are shown in Tables 2 and 3.

[0078] Table 2 Comparison of parameters of the analytical method optimization scheme and the Halbach scheme

[0079] Halbach approach Optimized approach β2 / ° -45 -21.117 β3 / ° -90 -53.661 β4 / ° -135 -167.07 [a2] 0.25 0.1888 [a3] 0.25 0.1498 [a4] 0.25 0.3237 w so / mm]] 2.5 2.1066

[0080] Table 3 Comparison of analytical solutions of performance of the optimization scheme and the Halbach scheme

[0081] Halbach approach Optimized approach Average torque / Nm 6.23 7.01 Torque ripple / % 0.625 0.144

[0082] The analytical method ignores the effects of inter-pole leakage, pole edge effect and saturation effect, and cannot accurately predict the torque, but can predict the change rule of the torque. Therefore, the analytical method can be used for preliminary optimization, and based on the optimization result of the analytical method, the finite element method is used for more accurate optimization. The optimization result of the finite element method is shown in Table 4.

[0083] Table 4 Comparison of parameters of the finite element method optimization scheme and the Halbach scheme

[0084] Halbach approach Optimized approach β2 / ° -45 -41.7 β3 / ° -90 -106.35 β4 / ° -135 -146.5 [a2] 0.25 0.13 [a3] 0.25 0.175 [a4] 0.25 0.115 w so / mm]] 2.5 2.89

[0085] Table 5 Comparison of finite element results of performance of the optimization scheme and the Halbach scheme

[0086] Halbach approach Optimized approach Average torque / Nm 5.98 6.66 Torque ripple / % 2.28 1.20

[0087] The comparison of the torques of the optimization scheme and the Halbach scheme is shown in Table 5. Figure 9 It can be seen that the average torque of the optimization scheme is obviously improved compared with the Halbach scheme.

[0088] The comparison of the finite element results of the two schemes shows that the torque of the discrete magnetization permanent magnet motor obtained by optimization is higher than that of the Halbach scheme, and the torque ripple is lower, that is, the performance of the discrete magnetization permanent magnet motor is better than that of the Halbach scheme.

[0089] It can be understood that the detailed function implementation of each unit / module can be referred to the description in the foregoing method embodiments, which will not be repeated here.

[0090] It should be understood that the above device is used to execute the method in the above embodiment, the corresponding program module in the device, the implementation principle and technical effect are similar to the description in the above method, the working process of the device can refer to the corresponding process in the above method, and details are not described here.

[0091] It can be understood that various digital numbers involved in the embodiments of the present application are only for convenient differentiation, and are not used to limit the scope of the embodiments of the present application.

[0092] Those skilled in the art easily understand that the above only describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A servo motor characterized by comprising: The rotor comprises a rotor core and magnetic steels, the rotor core is provided with a plurality of poles on its circumferential surface, each pole is composed of a plurality of magnetic steels, the magnetic steels of different poles are combined in the same way, at least two magnetic steels under the same pole have different central angles, the magnetization directions of all the magnetic steels under the same pole are different, and the magnetization direction of at least one magnetic steel is radial; The structural parameters of the servo motor are optimized in the following way: Based on a theoretical model, the residual magnetization vector of the servo motor at each moment is calculated; According to the stator slot opening width of the servo motor and the residual magnetization vector at each moment, the electromagnetic torque of the servo motor at each moment is solved; According to the electromagnetic torque of the servo motor at each moment, the average torque and torque ripple are calculated; The central angle coefficient and magnetization angle of the magnetic steel and the stator slot opening width are changed, and the above steps are repeated until the Pareto optimal stop, and the corresponding structural parameter combination is the optimization result; The theoretical model is as follows: wherein, is the residual magnetization vector, is the summation variable in the Fourier series expansion, taking values , is the radial component of the residual magnetization, is the circumferential component of the residual magnetization, is the number of rotor pole pairs, is the angle between the circumferential position of an internal point of the magnetic steel and the center line of the magnetic steel, whose magnetization direction is radially outward, is the radial unit vector, is the circumferential unit vector; wherein, is the residual magnetism of the magnetic steel, is the vacuum permeability, is the first is the central angle of the block magnetic steel, is the first is the angle between the center line of the block magnetic steel and the center line of the magnetic steel whose magnetization direction is radially outward, is the first is the magnetization angle of the block magnetic steel, , , is the central angle coefficient of the first is the pole pitch angle, , , is the number of blocks of each pole magnetic steel.

2. The servomotor of claim 1, wherein The servo motor is an inner rotor motor or an outer rotor motor.

3. The servomotor of claim 1, wherein When the plurality of magnetic steels under the same pole are of a symmetrical structure, the magnetization direction of the magnetic steel with a symmetrical structure is asymmetric.

4. The servomotor of claim 1, wherein When the magnetization directions of the plurality of magnetic steels under the same pole are symmetrical, the central angles of the magnetic steels with a symmetrical magnetization direction are different.

5. The servomotor of claim 1, wherein The magnetization directions of the magnetic steels with a radial magnetization direction in adjacent poles are opposite, and the magnetic steels at the same position have the same angle between the magnetization direction and the radial direction.

6. The rotor of claim 1, wherein The magnetic steel has anisotropy, and is oriented in the optimized magnetization direction in the manufacturing stage.

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