Structure capable of comprehensively weakening cogging torque and electromagnetic vibration of permanent magnet synchronous motor

Abstract

The invention relates to the technical field of permanent magnet synchronous motors, and particularly discloses a structure capable of comprehensively weakening cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, which comprises a rotating shaft, a rotor and a stator which are coaxially sleeved from inside to outside, the rotor comprises a rotor iron core which coaxially sleeves the rotating shaft, and a rotor section I, a rotor section II, a rotor section III and a rotor section IV which are arranged on the rotor iron core at equal intervals along the axial direction, and the rotor section I and the rotor section IV comprise a plurality of permanent magnet magnetic steels I which are circumferentially arranged at equal intervals; the second rotor section and the third rotor section comprise second permanent magnet magnetic steel which is the same in number and arranged in the circumferential direction at equal intervals, magnetic poles on the two sides of the first permanent magnet magnetic steel and the two sides of the second permanent magnet magnetic steel offset in the circumferential direction at equal angles, and the third rotor section and the fourth rotor section have the same axial dislocation offset relative to the first rotor section and the second rotor section. The problem that synchronous suppression of cogging torque and radial electromagnetic force is difficult to realize by an optimized structure of a traditional permanent magnet synchronous motor is solved.

Description

Technical Field

[0001] This application relates to the field of permanent magnet synchronous motor technology, and specifically discloses a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have been widely used in transportation electrification and industrial automation due to their high efficiency, simple control, and excellent performance. As an electromagnetic device for converting electrical energy, the abundant harmonic components in the air gap magnetic field of a PMSM can cause torque pulsation and electromagnetic vibration, mainly in the following two aspects.

[0003] On the one hand, the interaction between the magnetic field of the permanent magnet inside the permanent magnet synchronous motor and the slotted structure of the stator generates cogging torque. Cogging torque pulsation is a tangential electromagnetic force independent of the armature current. In transportation electrification applications, this directly manifests as a jerking sensation and a decline in driving experience at low speeds. More seriously, when the pulsation frequency of the cogging torque coincides with the resonant frequency of the stator and rotor, it generates strong vibrations, deteriorating system performance.

[0004] On the other hand, the rich spatiotemporal harmonic components in the air gap magnetic field interact to generate complex radial electromagnetic force waves, which are the main excitation source of electromagnetic vibration and noise. When the frequency of a certain order of radial electromagnetic force wave is close to or coincides with the natural frequency of the stator core, it will excite the structural vibration of the corresponding spatial mode and radiate outward in the form of electromagnetic noise, producing a high-frequency howling that can be perceived by the human ear, which seriously affects the user experience.

[0005] Both cogging torque pulsation and electromagnetic vibration can be regarded as manifestations of electromagnetic force in permanent magnet synchronous motors. They originate from the interaction of various components of the air gap magnetic field harmonics. Existing technologies address these characteristics by reshaping the air gap magnetic field from the perspective of stator and rotor structure optimization. For example, stator skew slots or permanent magnet skew poles are used, or topological structures such as optimized pole arc coefficients, unequal width magnetic poles, or magnetic pole segments are adopted to weaken cogging torque and electromagnetic vibration.

[0006] However, the cogging torque and radial electromagnetic force are strongly coupled in terms of harmonic sources. The magnetic field harmonics of the permanent magnet are not only a key factor in generating the cogging torque, but also an important component in constituting the radial magnetic flux density and generating the radial electromagnetic force. This leads to the contradiction and limitations of existing suppression strategies.

[0007] The drawback of existing technologies is that optimization strategies for cogging torque can worsen radial electromagnetic force characteristics, and vice versa. For example, the slant angle used to suppress cogging torque of a certain order may increase the amplitude of radial electromagnetic force waves of the critical order. Similarly, rotor structure optimization implemented to suppress radial electromagnetic force waves of the critical order may lead to an increase in cogging torque pulsation.

[0008] In summary, in the existing technology, the optimization structure of permanent magnet synchronous motors only adopts the design idea of ​​weakening a single objective, which makes it difficult to achieve simultaneous suppression of cogging torque and radial electromagnetic force. Even if a multi-objective optimization method is adopted to achieve dual objectives, it is limited to changing the motor structural parameters, resulting in limited weakening effect and excessive time consumption.

[0009] This invention provides a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, in order to solve the above-mentioned problems. Summary of the Invention

[0010] The purpose of this invention is to solve the problem that the optimized structure of traditional permanent magnet synchronous motors is difficult to achieve synchronous suppression of cogging torque and radial electromagnetic force.

[0011] To achieve the above objectives, the basic solution of the present invention provides a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, including a rotating shaft, a rotor and a stator coaxially mounted from the inside to the outside. The rotor includes a rotor core coaxially mounted outside the rotating shaft, and rotor segments one, two, three and four equidistantly arranged on the rotor core along the axial direction with equal axial length. Both rotor section one and rotor section four include a number of equidistant circumferentially arranged permanent magnets one, and rotor section two and rotor section three include the same number of equidistant circumferentially arranged permanent magnets two. Both sides of the permanent magnet first and the permanent magnet second are offset at equal angles along the circumferential direction. The angle at which one side of the permanent magnet first is offset along the circumferential direction is the same as the angle at which the other side of the permanent magnet second is offset along the circumferential direction, and the number of slots corresponding to the magnetic poles is an integer. The rotor segment three and the rotor segment four are axially misaligned relative to the rotor segment one and the rotor segment two at the same angle, and the angle of the axial misalignment is greater than or equal to 0°.

[0012] Furthermore, the offset angle of the axial misalignment offset , This represents even-order radial electromagnetic harmonics.

[0013] Furthermore, the offset angle of the axial misalignment offset .

[0014] Furthermore, the geometric center line angle of one side pole of each permanent magnet is offset by a theoretical electrical angle of 180° relative to the geometric center line angle of its other side pole, and then uniformly offset by an angle along the circumference of the rotor segment. ; The geometric center angle of the other pole of each permanent magnet is determined by offsetting the geometric center angle of its other pole by 180° (theoretical electrical angle) along the circumference of rotor segment two. ; The offset angle of one side pole of a permanent magnet. The offset angle between the two magnetic poles on the other side of the permanent magnet. same.

[0015] Furthermore, the offset angle The calculation formula is as follows: ; In the formula, , Indicates the number of stator slots. This indicates the order of the harmonic component with the largest amplitude after Fourier decomposition of the cogging torque.

[0016] Furthermore, the magnetic pole shapes and installation methods of rotor segments one, two, three, and four are the same.

[0017] Furthermore, the rotor section one, rotor section two, rotor section three, and rotor section four are all installed using surface mounting.

[0018] Furthermore, the rotor segment one, rotor segment two, rotor segment three, and rotor segment four are all installed in a built-in manner.

[0019] The principle and effect of this solution are as follows: 1. Compared with existing technologies, this invention divides the rotor into at least two conjugate magnetic pole structures: rotor segment one, rotor segment two, rotor segment three, and rotor segment four. A specific circumferential offset structure is employed on rotor segment three and rotor segment four, and the offset patterns of the magnetic pole structures in rotor segment one, rotor segment two, rotor segment three, and rotor segment four are mirror-symmetrical. This circumferential offset structure can directionally suppress key cogging torque harmonics by changing the harmonic spectrum of the rotor magnetomotive force.

[0020] 2. Compared with existing technologies, the asymmetric offset magnetic poles used in this invention differ from conventional symmetric magnetic poles in that they increase the content of odd-order electromagnetic force harmonics. To weaken radial electromagnetic forces of arbitrary order, this invention employs an axial conjugate offset structure for rotor segments one and two, combined with an overall axial offset structure for rotor segments three and four. This allows for the directional selective suppression of even-order harmonic electromagnetic forces in any spatial space, while also weakening odd-order harmonic electromagnetic forces. The axial offset angles of rotor segments four and three, which have the same structure as rotor segments one and two, are related to the order of the key electromagnetic force to be suppressed. Simultaneously, this axial offset structure utilizes the circumferential symmetry of the physical structure after rotor segmentation, solving the problem of uneven and unbalanced mass distribution of magnetic poles in the circumferential direction in traditional asymmetric offset magnetic poles. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, according to an embodiment of this application, is shown. Figure 2 The diagram shows a comparison of the cogging torque of a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, as proposed in this application, with that of a conventional symmetrical structure. Figure 3 The figures show the ERP equivalent power radiation level waterfall diagrams of a structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor proposed in this application and existing structures. Figure (a) is the ERP waterfall diagram of a motor with a rotor structure that uses circumferentially offset magnetic poles and axially non-skewed poles, and Figure (b) is the ERP waterfall diagram of a motor with a rotor structure that uses circumferentially offset magnetic poles and axially skewed poles. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0024] The reference numerals in the accompanying drawings include: rotor section 1, rotor section 2, rotor section 3, rotor section 4, shaft 5, rotor core 6, stator teeth 7, stator core 8, armature winding 9.

[0025] A structure that can comprehensively reduce the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, for example... Figure 1 As shown: This includes a rotating shaft 5, a rotor, and a stator, all coaxially assembled from the inside out. The rotor is housed inside the stator and coaxial with the stator core 8. The armature winding 9 is wound around the armature of the stator core 8. When current is applied, the armature winding 9 generates a rotating armature magnetic field. The stator and rotor magnetic fluxes, through the stator teeth 7, the stator yoke, the air gap, and the rotor core 6, form the magnetic flux circuit of the permanent magnet synchronous motor, realizing the conversion of electromagnetic energy.

[0026] like Figure 1 As shown, the rotor includes a rotor core 6 coaxially mounted on a shaft 5, and rotor segments 1, 2, 3, and 4 equidistantly arranged along the axial direction on the rotor core 6. Rotor segment 4 has the same structure as rotor segment 1, and rotor segment 3 has the same structure as rotor segment 2. Rotor segments 1, 2, 3, and 4 are mechanically independent, but after assembly, they are coaxially fixed to the same rotor core 6, together forming a complete p-pole rotor magnetic circuit. Furthermore, the axial lengths of rotor segments 1, 2, 3, and 4 are equal.

[0027] In rotor section 1 and rotor section 4, p permanent magnets are arranged at equal intervals. The geometric center angle of the N pole of each permanent magnet is offset by a theoretical electrical angle of 180° relative to the geometric center angle of the S pole, and then uniformly offset along the circumference of rotor section 1. The expression is as follows: ; In the formula, This indicates the actual geometric centerline angular position of the N pole of a permanent magnet. This indicates the angular position of the geometric center line of the S pole of a permanent magnet. .

[0028] In rotor section 2 and rotor section 3, p permanent magnets are arranged at equal intervals. The actual geometric center line angle of the S pole of each permanent magnet is offset by a theoretical electrical angle of 180° relative to the geometric center line angle of the N pole, and then uniformly offset by an angle along the circumference of rotor section 2. The expression is as follows: ; In the formula, This indicates the angular position of the geometric center line of the S pole of the permanent magnet steel. This indicates the actual geometric centerline angular position of the N pole of the permanent magnet steel. .

[0029] In this embodiment, the magnetic pole offset angles of rotor segments 1, 2, 3, and 4 are consistent. In other embodiments, this can be extended to a configuration where the N pole of rotor segments 1 and 4 is fixed and the S pole is offset, and the S pole of rotor segments 2 and 3 is fixed and the N pole is offset, achieving the same effect.

[0030] like Figure 1 As shown, there is an axial misalignment between rotor segments 3 and 4 and rotor segments 1 and 2. Rotor segments 3 and 4 are coaxially mounted on the rotor core 6, and are axially misaligned relative to rotor segments 1 and 2. Angle. Furthermore, the overall offset angles of rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4 relative to the reference value rotor segment 1 are 0, 0, and 0, respectively. , Rotor segment 1 and rotor segment 2 are conjugately distributed in the axial direction to achieve a circumferentially uniform and balanced distribution of rotor magnetic pole mass.

[0031] In this embodiment, the magnetic pole shape and installation method are consistent across all rotor segments. Permanent magnet one and permanent magnet two in rotor segments 1, 2, 3, and 4 are all surface-mounted. Furthermore, in this embodiment, the number of slots corresponding to each magnetic pole in each rotor segment is an integer. In other embodiments, permanent magnet one and permanent magnet two in rotor segments 1, 2, 3, and 4 can be internally mounted.

[0032] Based on the structure described in this embodiment, when the number of slots corresponding to each magnetic pole is an integer, the cogging torque of the permanent magnet synchronous motor is the sum of the cogging torques generated by each of the magnetic poles. The following is an explanation of the principle and implementation steps for reducing cogging torque according to the structure described in this embodiment: In this embodiment, the geometric center line angle of the N pole of rotor segment 1 has a circumferential offset angle. The offset angle can be obtained. The subsequent motor cogging torque is expressed as: .

[0033] In the formula, Represents the magnetomotive force of a permanent magnet Second harmonic amplitude Indicating air gap permeability Second harmonic amplitude This indicates the initial position angle of the permanent magnet poles relative to the stator teeth. Indicates the number of stator slots. This indicates the effective length of the permanent magnet synchronous motor. Indicates the outer radius of the rotor. Indicates the inner radius of the stator. Represents the extreme logarithm. It represents the vacuum permeability.

[0034] In a permanent magnet synchronous motor with an integer number of slots, the number of slots is an integer multiple of the number of poles. Simultaneously, the fundamental frequency of the cogging torque is the same as the number of slots. After trigonometric identity transformations, the absolute value expression for the cogging torque is: ; In the formula, express Fourier coefficients of secondary cogging torque harmonics.

[0035] The cogging torque pulsation data acquired through finite element analysis or testing equipment is used to obtain the amplitudes of each order harmonic of the cogging torque through Fourier decomposition. The harmonic component with the largest amplitude is selected as the main target for attenuation, and the corresponding order is denoted as . The circumferential offset angle of the N pole in rotor section one. By this The subharmonic is determined by the following expression: ; In the formula, .

[0036] In this embodiment, the S pole magnetic poles in rotor segment 2 and rotor segment 3 are offset circumferentially by an angle. The circumferential offset angle of the N pole magnetic pole in rotor section 1 and rotor section 4 Therefore, the cogging torque obtained by each rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4 is consistent and can be reduced. Secondary major cogging torque harmonics.

[0037] In this embodiment, the total cogging torque generated by the permanent magnet synchronous motor is obtained by superimposing rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4. After rotor segment 3 and rotor segment 4 are axially offset by an arbitrary angle, the phase of the cogging torque harmonics generated by rotor segment 1, rotor segment 2 and rotor segment 3, and rotor segment 4 deviates from that of rotor segment 3 and rotor segment 4. The amplitude of each order harmonic after superposition is reduced compared with the original harmonic amplitude, ensuring that the total cogging torque after axial offset is further weakened compared with the case without axial offset.

[0038] The following is an explanation of the principle and implementation steps of suppressing radial electromagnetic force according to the structure described in this embodiment.

[0039] Radial electromagnetic force of permanent magnet synchronous motor Calculated using Maxwell's stress tensor method, after neglecting the small tangential magnetic flux density component, the expression is as follows: ; In the formula, Indicates the magnetic close component, , This represents the magnetomotive force of a permanent magnet. This represents the air gap permeability.

[0040] In this embodiment, the magnetomotive force and air gap permeability have the following characteristics: Magnetomotive force generated by rotor section 1 It can be decomposed into all odd harmonics. and even harmonics The sum, expressed as follows: .

[0041] The rotor segment 2 of this invention is not subject to axial offset and can be considered as a conjugate segment. Its magnetomotive force adopts a conjugate design, and the expression is as follows: .

[0042] The expression for the air gap permeability function is: ; Among them, due to integer slots Since the value is even, the air gap permeability function is an even function that contains only even-order space harmonics.

[0043] In this embodiment, the radial electromagnetic force characteristics of rotor segment 2 and rotor segment 3 are as follows: According to the magnetomotive force-permeability method and Maxwell's stress tensor method, the radial electromagnetic force is proportional to the square of the radial magnetic flux density, and we can obtain: odd-order magnetomotive force harmonics Even-order magnetic permeability generates odd-order magnetic flux density harmonics. ; Even-order magnetomotive force harmonics Even-order magnetic flux density harmonics are generated by interaction with even-order magnetic permeability. ; The radial electromagnetic force of rotor segment 1 is expressed as: ; The radial electromagnetic force of rotor segment 2 without axial offset is expressed as: ; Based on the above expression for radial electromagnetic force, it can be seen that the harmonic order of the radial electromagnetic force is determined by the interaction of the magnetic flux density harmonic orders. Therefore, the following superposition law of electromagnetic force harmonics can be obtained:

[0044] The even-order electromagnetic force harmonics generated by rotor section 1 and rotor section 2 are in phase and originate from the same source, namely, odd-order magnetic flux density harmonics. Interaction and even-order magnetic flux density harmonics Interaction, i.e. .

[0045] The odd-order electromagnetic force harmonics generated by rotor section 1 and rotor section 2 are in opposite directions and originate from odd-order magnetic flux density harmonics. Even-order magnetic flux density harmonics The interaction, that is .

[0046] In this embodiment, when rotor segment 1 and rotor segment 2 are obtained by segmenting the rotor into equal-length segments, the total radial electromagnetic force of the permanent magnet synchronous motor is... Considering the radial electromagnetic forces generated by rotor segment 1 and rotor segment 2 as the axial average, the expression is as follows: .

[0047] The following is a description of the directional harmonic attenuation under the condition that the axial offset angles of rotor segment 3 and rotor segment 4 are not zero, based on the structure described in this embodiment:

[0048] The radial electromagnetic force generated by rotor section 1 consists of odd harmonics and even harmonics. The odd harmonics are represented as: .

[0049] Even harmonics are represented as: ;

[0050] In the formula, express The amplitude of the odd harmonic electromagnetic force express The amplitude of the second even harmonic electromagnetic force express Phase of the odd harmonic electromagnetic force express Phase of even-order harmonic electromagnetic forces.

[0051] When rotor segment 2 adopts the conjugate offset method, that is, when it is not offset axially relative to rotor segment 1, it is based on radial electromagnetic force waves. Assuming rigidity with rotor rotation, the radial electromagnetic force generated by rotor segment 2 is also expressed as a combination of odd and even harmonics. The odd harmonic form is as follows: The even harmonic form is Therefore, according to the principle of force wave superposition in rotor segments with equal shaft lengths, for odd-numbered segments... When electromagnetic force waves of different orders are superimposed in opposite directions, the amplitudes of odd-order electromagnetic force waves are opposite, while those of even-order waves are opposite. When electromagnetic force waves of different orders are superimposed in the same direction, the amplitudes of even-order electromagnetic force waves are the same. Therefore, the amplitudes of even-order electromagnetic force waves generated by rotor segment 1 and rotor segment 2 are... .

[0052] Since rotor segment 3 has the same structure as rotor segment 2, and rotor segment 4 has the same structure as rotor segment 1, in a special case, when rotor segment 3 and rotor segment 4 have no axial offset, for even-numbered... The superposition of electromagnetic force waves of different orders in the same direction yields the amplitude of electromagnetic force waves of even orders. Compared with the original electromagnetic force wave amplitude The relationship is as follows: .

[0053] When rotor segment 3 and rotor segment 4 are axially offset Similarly, rotor segments 3 and 4 do not generate electromagnetic force waves of odd order, but only generate electromagnetic force waves of even order with varying amplitudes. For even numbers The superposition of electromagnetic force waves of different orders in the same direction yields the amplitude of electromagnetic force waves of even orders. Compared with the original electromagnetic force wave amplitude The relationship is as follows: .

[0054] In summary, in this embodiment, the overall offset angle of rotor segment 3 and rotor segment 4 is... Based on this, it can be determined that: When even order: When the secondary radial electromagnetic harmonic content is high, the offset angle In particular, when The method used is conjugate axial offset, which, due to the symmetrical axial magnetic poles, can weaken all unbalanced magnetic pull.

[0055] In this embodiment, a conventional permanent magnet synchronous motor employing a magnetic pole offset cogging torque suppression structure is used as a control group. In the control group, the conventional permanent magnet synchronous motor does not use axial segmentation and only uses circumferential offset. The rotor structure has an angle. In the control group, it can also suppress cogging torque pulsation. Its total radial electromagnetic force composition is the same as the electromagnetic force harmonic order contained in the action of rotor segment one or rotor segment two alone. Compared with conventional symmetrical magnetic pole motors, its total radial electromagnetic force contains odd-order magnetic flux density. Even magnetic flux density Interaction-generated cross terms However, this cross term will generate odd-order radial electromagnetic forces that are not present in conventional symmetrical pole motors, such as when the number of pole pairs is 3. The non-zero amplitude of the aforementioned electromagnetic force waves is a key excitation source causing motor vibration. Furthermore, since motor vibration is also related to motor modal parameters, some even-order electromagnetic force waves can also generate severe electromagnetic vibrations. Traditional permanent magnet synchronous motors employing pole offset cogging torque suppression structures do not contain any suppression methods.

[0056] The structure described in this embodiment, which combines circumferential and axial offset, fundamentally solves the aforementioned defects. Specifically, in the permanent magnet synchronous motor provided in this embodiment, the even-order forces of rotor segment 1 and rotor segment 2 are in-phase, while the odd-order forces are out-of-phase. Axial offset enables the overall radial force amplitude to individually target specific even-order harmonics and attenuate all odd-order harmonics. The beneficial effects of the structure described in this embodiment can be achieved by selecting the circumferential offset angle. , and axial offset angle Based on the above analysis, the structure described in this embodiment has the following two significant advantages:

[0057] First, when the axial offset angle At this time, theoretically, the amplitude of all odd-order forces is zero, which is an implementation method that weakens odd-order electromagnetic vibration forces without sacrificing the average torque. Specifically, the average torque is... First-order electromagnetic force, which is mainly composed of spatial order of The rotor magnetomotive force and spatial order are The axial offset is generated by the interaction of the stator magnetomotive force. The effect of angle on average torque can be determined by analyzing its influence on the magnetomotive force (MMF) of the permanent magnet. The fundamental MMF of the stator and rotor belongs to odd harmonic MMF. According to the conjugate offset principle, the odd harmonic MMF is in phase before and after offset. Therefore, applying the principle of in-phase superposition, the amplitude of the fundamental MMF after axial offset is... Compared to the original magnetomotive force Weakened to Due to average torque Therefore, the average torque follows the same decay law, that is... .

[0058] Therefore, after conjugate offset, the average torque is the same as that of the control group. That is, without losing the average torque, the antiphase characteristic of conjugate offset weakens all odd-order radial forces introduced by circumferential offset, fundamentally compensating for the electromagnetic vibration suppression defects of the control group.

[0059] Furthermore, implementation methods are provided for the targeted attenuation of critical even-order radial electromagnetic force waves with extremely low average torque loss. This is applicable when it is necessary to suppress a high-order even-order force, such as... At this time, the axial offset angle can be set. This weakens the electromagnetic force of that order. At this point, the expression for the average torque is as follows: .

[0060] Based on the above formula, the torque loss is only 0.9%.

[0061] Most importantly, the control group could not suppress it. The odd-order harmonic electromagnetic force can be significantly weakened in this invention.

[0062] In this embodiment, the preferred embodiment adopts a four-segment axially symmetrical rotor structure, which is arranged axially as rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4. The first two segments of the four rotor structure are axially conjugately distributed, and the last two segments are conjugately distributed and the overall axial offset is the same angle.

[0063] Furthermore, the construction of a structure to weaken the cogging torque and electromagnetic vibration of a permanent magnet synchronous motor can be carried out through the following steps: First, a two-dimensional finite element model of a 6-pole, 36-slot permanent magnet synchronous motor is established. This model adopts a magnetically symmetrical and axially unsegmented structure. The performance of this model is analyzed through finite element transient electromagnetic simulation. Fast Fourier analysis is performed on the obtained cogging torque pulsation data to determine that the fundamental frequency of the cogging torque is LCM(6,36) = 36th harmonic, and the fundamental frequency amplitude accounts for a large proportion.

[0064] Keep the S poles of rotor segment 1 and rotor segment 4 in their current positions, and offset the N pole relative to its initial position by an angle. The mechanical angle of the circumferential offset of the N magnetic pole is determined to be 5°. The N poles of rotor segment 2 and rotor segment 3 are kept unchanged, and the S magnetic pole is offset by a mechanical angle of 5° relative to the initial position to suppress the fundamental component of the cogging torque.

[0065] A finite element simulation model of a permanent magnet synchronous motor with a rotor divided into two segments, using only rotor segment one and rotor segment two, was established. Spatiotemporal two-dimensional data of radial electromagnetic force waves were acquired. Based on two-dimensional Fourier transform and multiphysics simulation (electromagnetic-structural-acoustic simulation model), the key electromagnetic force wave time frequencies of the motor were determined to be the 11th, 13th, and 20th harmonics. Two-dimensional Fourier force wave decomposition determined the spatial order of the main suppression to be 36th order. Rotor segment models of rotor segment one (1), rotor segment two (2), rotor segment three (3), and rotor segment four (4) were constructed. It was determined that rotor segment four (4) and rotor segment three (3) have the same structure as rotor segment one (1) and rotor segment two (2), and their overall axial offset angles relative to rotor segment one (1) and rotor segment two (2) are... That is, the axial offset angle of the first and second segments of the rotor is set to -2.5°, and the axial offset angle of the third and fourth segments of the rotor relative to the first and second segments is set to 2.5°.

[0066] The conventional symmetrical structure uses only one magnetic pole offset, which is consistent with the structure of rotor section one. Figure 2 This is a comparison diagram of the cogging torque between the structure proposed in this invention and the conventional symmetrical structure, as shown in the figure. Figure 2 As shown, the cogging torque of the structure of the present invention can be reduced by 75% compared to conventional methods.

[0067] Figure 3 The ERP equivalent power radiation level waterfall diagram of the structure proposed in this invention and the conventional symmetrical structure is shown below. Figure 3 As shown, Figure (a) is the ERP waterfall diagram of a motor with a rotor structure featuring circumferentially offset magnetic poles and axially non-skewed poles, and Figure (b) is the ERP waterfall diagram of a motor with a rotor structure featuring circumferentially offset magnetic poles and axially skewed poles. Figure (b) corresponds to the structure proposed in this invention. In Figures (a) and (b), the marked 11th, 18th, 13th, and 20th represent the 11th, 18th, 13th, and 20th orders, respectively, corresponding to frequencies of 11 times, 18 times, 13 times, and 20 times. The comparison results show that the vibration at the 20th harmonic frequency of the motor of this invention is greatly reduced compared to the control scheme. At the same time, some odd harmonics: the 5th, 7th, and 9th harmonics, as well as the 11th and 13th harmonics which have a greater impact on vibration, are weakened, resulting in a reduction in the overall vibration amplitude and an effective improvement in the NVH performance of the motor.

[0068] In summary, this invention does not employ traditional symmetrical magnetic poles or identical asymmetrical magnetic poles. Instead, it divides the rotor into at least two conjugate magnetic pole structures: rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4. Both rotor segment 3 and rotor segment 4 utilize a circumferential offset structure at a specific angle, and the offset patterns of the magnetic pole structures in rotor segment 1, rotor segment 2, rotor segment 3, and rotor segment 4 exhibit a mirror-symmetric relationship. This circumferential offset structure, by altering the harmonic spectrum of the rotor magnetomotive force, can directionally suppress critical cogging torque harmonics. The offset angle of the magnetic poles is related to the amplitude components of the main harmonics of the cogging torque.

[0069] The asymmetric offset magnetic poles used in this invention differ from conventional symmetric magnetic poles in that they incorporate an increased content of odd-order electromagnetic harmonics. To weaken radial electromagnetic forces of arbitrary order, this invention employs an axial conjugate offset structure for rotor segments 1 and 2, combined with an overall axial offset structure for rotor segments 3 and 4. This allows for the directional selective suppression of even-order harmonic electromagnetic forces in any spatial space, while also weakening odd-order harmonic electromagnetic forces. The axial offset angles of rotor segments 4 and 3, which share the same structure as rotor segments 1 and 2, are related to the order of the critical electromagnetic forces to be suppressed. Furthermore, this axial offset structure utilizes the circumferential symmetry of the physical structure after rotor segmentation, resolving the problem of uneven and unbalanced mass distribution of magnetic poles in the circumferential direction in traditional asymmetric offset magnetic poles.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A structure capable of comprehensively reducing cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, comprising a rotating shaft, a rotor, and a stator coaxially mounted from the inside out, characterized in that, The rotor includes a rotor core coaxially mounted outside the shaft, and rotor segments one, two, three, and four equidistantly arranged on the rotor core along the axial direction with equal axial length. Both rotor section one and rotor section four include a number of equidistant circumferentially arranged permanent magnets one, and rotor section two and rotor section three include the same number of equidistant circumferentially arranged permanent magnets two. Both sides of the permanent magnet first and the permanent magnet second are offset at equal angles along the circumferential direction. The angle at which one side of the permanent magnet first is offset along the circumferential direction is the same as the angle at which the other side of the permanent magnet second is offset along the circumferential direction, and the number of slots corresponding to the magnetic poles is an integer. The rotor segment three and the rotor segment four are axially misaligned relative to the rotor segment one and the rotor segment two at the same angle, and the angle of the axial misalignment is greater than or equal to 0°.

2. The structure according to claim 1 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The offset angle of the axial misalignment , This represents even-order radial electromagnetic harmonics.

3. A structure according to claim 1 or 2 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The offset angle of the axial misalignment .

4. The structure according to claim 1 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The geometric center angle of one side pole of each permanent magnet is determined by offsetting the geometric center angle of the other side pole by a theoretical electrical angle of 180°, and then uniformly offset along the circumference of the rotor segment. ; The geometric center angle of the other pole of each permanent magnet is determined by offsetting the geometric center angle of its other pole by 180° (theoretical electrical angle) along the circumference of rotor segment two. ; The offset angle of one side pole of a permanent magnet. The offset angle between the two magnetic poles on the other side of the permanent magnet. same.

5. A structure according to claim 4 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, Offset Angle The calculation formula is as follows: ； In the formula, , Indicates the number of stator slots. This indicates the order of the harmonic component with the largest amplitude after Fourier decomposition of the cogging torque.

6. A structure according to claim 1 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The magnetic pole shapes and installation methods of rotor segments one, two, three, and four are the same.

7. A structure according to claim 6 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The rotor sections 1, 2, 3, and 4 are all installed using surface mounting.

8. A structure according to claim 6 that can comprehensively reduce cogging torque and electromagnetic vibration of a permanent magnet synchronous motor, characterized in that, The rotor segments 1, 2, 3, and 4 are all installed in a built-in manner.

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