A bidirectional modulation double rotor permanent magnet Vernier motor

Abstract

The application discloses a bidirectional modulation double-rotor permanent magnet Vernier motor, belongs to the field of permanent magnet motors, and aims at solving the problems of low internal space utilization, limited torque density of single-rotor permanent magnet synchronous motor, and large amount of permanent magnets and limited magnetic field modulation effect of double-rotor permanent magnet motor. The bidirectional modulation double-rotor permanent magnet Vernier motor comprises an outer rotor, a stator and an inner rotor, the three are coaxially arranged, and the stator is located between the inner rotor and the outer rotor. The stator is provided with inner and outer stator teeth, an armature winding and permanent magnets, and the inner and outer rotors adopt an alternating pole structure. Through bidirectional magnetic field modulation, higher torque output is realized under the same volume by utilizing multi-harmonic interaction, and the amount of permanent magnets is significantly reduced. The bidirectional modulation double-rotor permanent magnet Vernier motor is suitable for high torque density and high efficiency permanent magnet motor application occasions.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motor technology, and in particular to a bidirectional modulated dual-rotor permanent magnet vernier motor. Background Technology

[0002] Traditional single-rotor permanent magnet synchronous motors (PMSMs) offer advantages such as simple structure, mature manufacturing processes, high efficiency, and high reliability. However, a significant portion of the internal space of a single-rotor PMSM remains unutilized, resulting in a large internal cavity proportion and low space utilization. With continuous technological advancements across various fields, the demands on motor torque density are increasing. Therefore, how to fully utilize the internal space of the motor and further improve the torque density of PMSMs has become a crucial issue.

[0003] The dual-rotor permanent magnet synchronous motor is a composite permanent magnet motor with two rotors, inner and outer. Compared with the traditional single-rotor permanent magnet motor, this dual-air gap motor has a compact structure, high space utilization, and can greatly improve torque density, operating efficiency, and various aspects of motor performance, making it highly practical and with broad application prospects.

[0004] Permanent magnet vernier motors have attracted widespread attention due to their ability to modulate specific harmonics to increase motor torque. Typically, permanent magnets are placed on the rotor, with stator teeth acting as magnetic conductors to achieve rotor permanent magnet field modulation, resulting in a unidirectional modulation structure. Building upon this unidirectional modulation structure, permanent magnets are placed at the stator slots, transforming the rotor into an alternating pole structure of "permanent magnet-iron pole," enabling simultaneous modulation of both the stator and rotor permanent magnet fields, resulting in a bidirectional modulation structure. By selecting a suitable pole-slot configuration, the specific harmonics generated by bidirectional modulation can interact with the armature magnetic field to produce higher torque and significantly reduce the amount of permanent magnets required.

[0005] In summary, traditional single-rotor permanent magnet synchronous motors suffer from low internal space utilization and limited torque density. While dual-rotor permanent magnet motors can improve both space utilization and torque density, they still face challenges such as large permanent magnet requirements and limited magnetic field modulation effects. Therefore, there is an urgent need for a motor structure that can output greater torque and require fewer permanent magnets within the same volume. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a bidirectional modulated dual-rotor permanent magnet vernier motor. By employing a structure combining dual rotors and bidirectional magnetic field modulation, it significantly reduces the amount of permanent magnets used while maintaining high space utilization and enhancing the magnetic field modulation effect, thereby achieving higher torque output within the same volume.

[0007] The present invention discloses a bidirectional modulated dual-rotor permanent magnet vernier motor, comprising an outer rotor, a stator, and an inner rotor; the stator is disposed between the inner rotor and the outer rotor and the three are coaxial, and the inner rotor and the outer rotor output torque coaxially;

[0008] The outer rotor includes an outer rotor yoke, multiple outer rotor teeth, and an outer rotor permanent magnet. An outer rotor slot is formed between two adjacent outer rotor teeth, and the outer rotor permanent magnet is disposed in the outer rotor slot.

[0009] The stator includes a stator yoke, multiple outer stator teeth, an outer armature winding, an outer stator permanent magnet, multiple inner stator teeth, an inner armature winding, and an inner stator permanent magnet; an outer stator slot is formed between two adjacent outer stator teeth, the outer armature winding is disposed in the outer stator slot, and the outer stator permanent magnet is disposed at the slot opening of the outer stator slot; an inner stator slot is formed between two adjacent inner stator teeth, the inner armature winding is disposed in the inner stator slot, and the inner stator permanent magnet is disposed at the slot opening of the inner stator slot;

[0010] The inner rotor includes an inner rotor yoke, multiple inner rotor teeth, and an inner rotor permanent magnet. An inner rotor slot is formed between two adjacent inner rotor teeth, and the inner rotor permanent magnet is disposed in the inner rotor slot.

[0011] Preferably, the stator yoke provides a magnetic flux path for the outer magnetic field and serves as a structural component to make the stator an integral whole.

[0012] Preferably, the thickness of the stator yoke is configured such that the main magnetic flux generated by the permanent magnet under no-load conditions mainly forms a series magnetic circuit through the inner stator teeth and the outer stator teeth.

[0013] Preferably, the ratio of the radial thickness of the stator yoke to the radial height of the outer stator tooth is not greater than 1.

[0014] Preferably, the number of outer stator teeth and inner stator teeth are the same, and their radial positions correspond.

[0015] Preferably, the number of outer rotor teeth and inner rotor teeth are the same, and their radial positions correspond.

[0016] Preferably, the outer rotor permanent magnet has the same polarity as the inner rotor permanent magnet, the outer stator permanent magnet has the same polarity as the inner stator permanent magnet, and the polarity of the outer rotor permanent magnet is the same as or opposite to that of the outer stator permanent magnet.

[0017] Preferably, the magnetization methods of the outer rotor permanent magnet, the inner rotor permanent magnet, the outer stator permanent magnet, and the inner stator permanent magnet are parallel magnetization, radial magnetization, or Halbach magnetization.

[0018] Preferably, the outer armature winding and the inner armature winding have the same winding arrangement, and they are connected in series or energized independently.

[0019] Preferably, the number of stator slots Number of pole pairs of stator permanent magnets Number of pole pairs of the internal rotor permanent magnet and the number of armature winding pole pairs The following conditions must be met:

[0020]

[0021] and .

[0022] The beneficial effects of this invention are:

[0023] Compared with existing technologies, the bidirectional modulated dual-rotor permanent magnet vernier motor provided by this invention has the following significant advantages:

[0024] 1. High torque density and low permanent magnet usage: This invention creatively combines a dual-rotor structure with the principle of bidirectional magnetic field modulation between the stator and rotor. By selecting specific pole slot combinations, the permanent magnet magnetic field and the harmonic components of multiple pole pairs in the armature magnetic field can interact synchronously and effectively to jointly generate electromagnetic torque. This multi-harmonic synergistic mechanism enables the motor to output torque far exceeding that of traditional structures within the same volume, while significantly reducing the amount of permanent magnets used and lowering material costs.

[0025] 2. Optimized magnetic circuit structure and superior electromagnetic performance: By employing the same polarity of the inner and outer rotor permanent magnets, and their synergistic effect with the stator permanent magnets, a series magnetic circuit is constructed, forming a closed loop through which the main magnetic flux sequentially passes through the inner rotor permanent magnet, inner stator permanent magnet, stator teeth, outer stator permanent magnet, and outer rotor permanent magnet. This magnetic circuit allows for full utilization of most of the magnetic flux, effectively reducing the magnetic flux load on the stator yoke, thus allowing for a thinner stator yoke design. This not only reduces weight and increases the air gap diameter of the inner rotor, providing space for increased torque, but also optimizes the overall electromagnetic performance of the motor.

[0026] 3. Robust and reliable structure with low eddy current losses: Both the inner and outer rotors of this invention adopt an alternating pole structure of "permanent magnet-iron pole". Compared with the traditional surface-mounted permanent magnet rotor, this structure significantly reduces the harmonic magnetic field acting on the permanent magnet itself, thereby significantly reducing eddy current losses in the permanent magnet, alleviating the heat generation problem of the permanent magnet during motor operation, and improving the reliability and service life of the motor.

[0027] 4. High structural integration, excellent manufacturability and mechanical performance: Compared to yokeless dual-rotor motors, this invention introduces a stator yoke design. This yoke not only provides the necessary magnetic flux path for the outer magnetic field and improves the magnetic field distribution, but more importantly, as a core structural component, it integrates the inner and outer stator teeth into a robust whole. This design greatly reduces the processing difficulty of the stator core and the winding winding difficulty, simplifies the assembly process, and significantly enhances the mechanical strength of the stator structure. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a bidirectional modulated dual-rotor permanent magnet vernier motor according to the present invention;

[0029] Figure 2 This is a schematic diagram of the connection of the armature winding of a bidirectional modulated dual-rotor permanent magnet vernier motor according to the present invention;

[0030] Figure 3 This is a diagram of the main flux path of a bidirectional modulated dual-rotor permanent magnet vernier motor under no-load conditions, as described in this invention.

[0031] Figure 4 This is a magnetic flux density diagram of the air gap of a bidirectional modulated dual-rotor permanent magnet vernier motor as described in this invention, wherein... Figure 4 (a) is a waveform diagram of the air gap outside the permanent magnet magnetic field; Figure 4 (b) is a waveform diagram of the air gap within the permanent magnet magnetic field; Figure 4 (c) is a diagram showing the amplitude of the main harmonics of the air gap magnetic flux density of the permanent magnet magnetic field;

[0032] Figure 5 This is an air gap magnetic flux density diagram of the armature magnetic field of a bidirectional modulated dual-rotor permanent magnet vernier motor as described in this invention, wherein... Figure 5 (a) is a waveform diagram of the air gap outside the armature magnetic field; Figure 5 (b) is a waveform diagram of the air gap within the armature magnetic field; Figure 5 (c) is a diagram showing the amplitude of the main harmonics of the air gap magnetic flux density of the armature magnetic field;

[0033] Figure 6 These are schematic diagrams of three types of dual-rotor permanent magnet motors, among which... Figure 6 (a) is a structural diagram of a traditional dual-rotor motor (Model 1); Figure 6 (b) is a structural diagram of a unidirectional modulated dual-rotor motor (Model 2); Figure 6 (c) is a structural diagram of a unidirectional modulated alternating pole dual rotor motor (Model 3);

[0034] Figure 7 This paper compares the no-load line back EMF waveform and harmonic amplitude of three types of dual-rotor permanent magnet motors (Models 1, 2, and 3) and the bidirectional modulated dual-rotor permanent magnet vernier motor described in this invention (Model 4). Figure 7(a) Comparison of the back EMF waveforms of the unloaded line for the four models; Figure 7 (b) Comparison of the back EMF harmonic amplitudes of the four models for the unloaded line;

[0035] Figure 8 This is a comparison diagram of the torque waveforms of three types of dual-rotor permanent magnet motors and the bidirectional modulation dual-rotor permanent magnet vernier motor (model 4) described in this invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] The specific embodiments of the bidirectional modulated dual-rotor permanent magnet vernier motor provided by the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] Specific Implementation Method 1: The following is combined with... Figures 1 to 8 This embodiment describes a bidirectional modulated dual-rotor permanent magnet vernier motor, which includes an outer rotor 1, a stator 2, and an inner rotor 3. The stator 2 is disposed between the inner rotor 3 and the outer rotor 1, and the three are coaxial. The inner rotor 3 and the outer rotor 1 output torque coaxially.

[0040] The outer rotor 1 includes an outer rotor yoke 11, a plurality of outer rotor teeth 12 and an outer rotor permanent magnet 13, an outer rotor slot is formed between two adjacent outer rotor teeth 12, and the outer rotor permanent magnet 13 is disposed in the outer rotor slot;

[0041] The stator 2 includes a stator yoke 201, multiple outer stator teeth 211, an outer armature winding 212, an outer stator permanent magnet 213, multiple inner stator teeth 221, an inner armature winding 222, and an inner stator permanent magnet 223. An outer stator slot is formed between two adjacent outer stator teeth 211, the outer armature winding 212 is disposed in the outer stator slot, and the outer stator permanent magnet 213 is disposed at the slot opening of the outer stator slot. An inner stator slot is formed between two adjacent inner stator teeth 221, the inner armature winding 222 is disposed in the inner stator slot, and the inner stator permanent magnet 223 is disposed at the slot opening of the inner stator slot.

[0042] The inner rotor 3 includes an inner rotor yoke 31, a plurality of inner rotor teeth 32 and an inner rotor permanent magnet 33. An inner rotor slot is formed between two adjacent inner rotor teeth 32, and the inner rotor permanent magnet 33 is disposed in the inner rotor slot.

[0043] The stator yoke 201 provides a magnetic flux path for the outer magnetic field and serves as a structural component to make the stator 2 a whole.

[0044] The thickness of the stator yoke 201 is configured such that the main magnetic flux generated by the permanent magnet when unloaded mainly forms a series magnetic circuit through the inner stator tooth 221 and the outer stator tooth 211.

[0045] The ratio of the radial thickness of the stator yoke 201 to the radial height of the outer stator tooth 211 is not greater than 0.2.

[0046] The number of outer stator teeth 211 and inner stator teeth 221 are the same, and their radial positions correspond.

[0047] The number of outer rotor teeth 12 and inner rotor teeth 32 are the same, and their radial positions correspond.

[0048] The outer rotor permanent magnet 13 has the same polarity as the inner rotor permanent magnet 33, the outer stator permanent magnet 213 has the same polarity as the inner stator permanent magnet 223, and the polarity of the outer rotor permanent magnet 13 is the same as or opposite to that of the outer stator permanent magnet 213.

[0049] The magnetization methods for the outer rotor permanent magnet 13, the inner rotor permanent magnet 33, the outer stator permanent magnet 213, and the inner stator permanent magnet 223 are parallel magnetization, radial magnetization, or Halbach magnetization.

[0050] The outer armature winding 212 and the inner armature winding 222 have the same winding arrangement, and they are connected in series or energized independently.

[0051] Number of stator slots Number of pole pairs of stator permanent magnets Number of pole pairs of the internal rotor permanent magnet and the number of armature winding pole pairs The following conditions must be met:

[0052]

[0053] and .

[0054] Example: A 24-slot, 40-pole bidirectional modulated dual-rotor permanent magnet vernier motor.

[0055] Reference Figure 1This embodiment provides a bidirectional modulated dual-rotor permanent magnet vernier motor, which includes an outer rotor 1, a stator 2, and an inner rotor 3. The outer rotor 1, stator 2, and inner rotor 3 are coaxially arranged from the outside to the inside, that is, the stator 2 is located between the inner rotor 3 and the outer rotor 1. The inner rotor 3 and the outer rotor 1 output torque through a coaxial output structure, realizing the dual rotors rotating in the same direction.

[0056] 1. External rotor structure

[0057] The outer rotor 1 includes an outer rotor yoke 11, 20 outer rotor teeth 12, and 20 outer rotor permanent magnets 13. The 20 outer rotor teeth 12 are uniformly protruding circumferentially on the inner side of the outer rotor yoke 11. An outer rotor slot is formed between two adjacent outer rotor teeth 12, and the outer rotor permanent magnets 13 are embedded in the outer rotor slots. All the outer rotor permanent magnets 13 are magnetized in parallel directions and have the same polarity; for example, their surfaces near the air gap are all N poles.

[0058] 2. Stator Structure

[0059] The stator 2 is a bidirectional modulation core component, including a stator yoke 201, 24 outer stator teeth 211, 24 inner stator teeth 221, an outer armature winding 212, an inner armature winding 222, 24 outer stator permanent magnets 213, and 24 inner stator permanent magnets 223.

[0060] Teeth and slots: 24 outer stator teeth 211 and 24 inner stator teeth 221 are evenly protruding circumferentially on the outer and inner sides of the stator yoke 201, respectively, and their radial positions correspond one-to-one. An outer stator slot is formed between two adjacent outer stator teeth 211, and an inner stator slot is formed between two adjacent inner stator teeth 221. Therefore, the number of inner and outer stator slots... Both are 24.

[0061] Permanent magnet arrangement: The outer stator permanent magnet 213 is embedded in the slot opening of the outer stator; the inner stator permanent magnet 223 is embedded in the slot opening of the inner stator. All outer stator permanent magnets 213 have the same polarity, and all inner stator permanent magnets 223 have the same polarity. In this embodiment, the polarities of the inner and outer stator permanent magnets are the same (for example, the outer stator permanent magnet 213 has an S pole near the air gap surface, and the inner stator permanent magnet 223 also has an S pole near the air gap surface).

[0062] Winding arrangement: The outer armature winding 212 is embedded in the outer stator slot, located below the outer stator permanent magnet 213; the inner armature winding 222 is embedded in the inner stator slot, located above the inner stator permanent magnet 223. Both the inner and outer armature windings are arranged in a distributed manner and have the same form, both being 24 slots and 8 poles (i.e., armature winding pole pairs). The two are arranged in an integer slot configuration of 4, and connected in series in the circuit.

[0063] Stator yoke: The stator yoke 201 connects the inner and outer stator teeth. Its radial thickness is relatively thin; through optimized design, the ratio of its radial thickness to the radial height of the outer stator tooth 211 is 0.1. This design ensures that, under no-load conditions, the main magnetic flux generated by the permanent magnet primarily forms a series magnetic circuit through the inner and outer stator teeth (e.g., ...). Figure 3 As shown in the figure, the yoke provides an additional magnetic flux path for the outer magnetic field and acts as a mechanical skeleton to make the stator 2 a robust whole, which is easy to process and assemble.

[0064] 3. Internal rotor structure

[0065] The inner rotor 3 includes an inner rotor yoke 31, 20 inner rotor teeth 32, and 20 inner rotor permanent magnets 33. The 20 inner rotor teeth 32 are evenly protruding circumferentially on the outer side of the inner rotor yoke 31. An inner rotor slot is formed between two adjacent inner rotor teeth 32, and the inner rotor permanent magnets 33 are embedded in the inner rotor slot. All the inner rotor permanent magnets 33 are magnetized in parallel directions, have the same polarity, and have the same polarity as the outer rotor permanent magnets 13 (i.e., all are N poles near the air gap surface).

[0066] 4. Pole-groove fit and working principle

[0067] The key to this embodiment lies in its pole-slot configuration satisfying the magnetic field modulation principle. Specific parameters include: number of stator slots. =24, Number of pole pairs of stator permanent magnets =24, Number of pole pairs of the internal rotor permanent magnet =20, number of armature winding pole pairs =4. These parameters satisfy the following relation: .

[0068] With this coordination, when a three-phase sinusoidal current is applied to the armature winding, the resulting four pairs of armature magnetic field harmonics ( =4) and the 20 pairs of pole magnetic field harmonics generated by the permanent magnet ( =20), through the modulation of the stator and rotor teeth, they can interact to generate stable electromagnetic torque. At the same time, the stator permanent magnet also participates in magnetic field modulation, realizing "bidirectional modulation", thus enabling the output of higher torque than traditional dual-rotor motors or unidirectional modulation motors under the same volume and current.

[0069] 5. Analysis of the Principle of Magnetic Field Modulation

[0070] The key to achieving high torque output in this embodiment lies in its successful bidirectional magnetic field modulation. The magnetic field modulation mechanism of this invention will be briefly analyzed below using an air gap magnetic permeability model.

[0071] Since the inner and outer layers of the motor have symmetrical pole slots, the following analysis will only take the inner layer as an example.

[0072] Under no-load conditions, the air gap magnetic field is contributed by both the rotor permanent magnet magnetic field and the stator permanent magnet magnetic field. The rotor permanent magnet magnetomotive force can be expressed as:

[0073] The rotor permanent magnet magnetomotive force can be expressed as:

[0074] (1)

[0075] In the formula, This represents the DC component of the rotor magnetomotive force. Rotor magnetomotive force Second harmonic amplitude; Spatial location; For time; This is the initial position of the rotor; This represents the angular velocity of the permanent magnet rotor, with counterclockwise as the positive direction.

[0076] The stator permanent magnet magnetomotive force can be expressed as:

[0077] (2)

[0078] In the formula, This is the DC component of the stator magnetomotive force; stator magnetomotive force Second harmonic amplitude.

[0079] The air gap ratio permeability can be expressed as

[0080] (3)

[0081] In the formula, This is the air gap length; The vacuum permeability; Spatial location; For time; This is the initial position of the rotor; ω represents the angular velocity of the permanent magnet rotor. For the air gap ratio permeability considering only the effect of stator tooth space variation, in the formula... and These are the constant value of the air gap ratio permeability and the amplitude of the nth harmonic, respectively, considering only the effect of stator tooth space variation; For the air gap ratio permeability considering only the effect of rotor tooth cogging variation, in the formula... and These are the constants of the air gap ratio permeability considering only the variation in rotor tooth cogging, and... The amplitude of the second harmonic; where the coefficient is... , , , satisfy:

[0082] (4)

[0083] When the motor is under no-load, the magnetic circuit is set to be in an unsaturated state. At this time, the air gap magnetic field is an algebraic superposition of the rotor permanent magnet magnetic field and the stator permanent magnet magnetic field. It can be represented as

[0084] (5)

[0085] when When all values ​​are 1, the amplitude of each harmonic of the permanent magnet magnetic field is the largest. The corresponding harmonic amplitude, phase, number of pole pairs and rotational speed are shown in Table 1 below.

[0086] Table 1 Harmonic Characteristics of Air Gap Magnetic Density in Permanent Magnet Magnetic Field ( Take 1 for all)

[0087]

[0088] Table 1 shows the harmonic characteristics of the air gap magnetic flux density of the permanent magnet field derived analytically. A finite element model is then established for simulation. Figure 4 (a) is the waveform of the air gap magnetic flux density outside the permanent magnet magnetic field. Figure 4 (b) is the waveform of the air gap magnetic flux density within the permanent magnet magnetic field. Figure 4 (c) represents the amplitudes of the main harmonics in the air gap magnetic flux density of the permanent magnet field. Simulation results show that the pole pairs with higher harmonic amplitudes mainly include... Figure 4 (c) shows the harmonic pole pairs, with the pole pairs having high harmonic content being 4, 20, 24, 40, 44, 60, and 72. The pole pairs of 4, 20, 24, 40, and 44 correspond to the analytical analysis above. The 60-pole-pole-pair harmonic is a high-order natural harmonic magnetic field (rotational speed ω). r The 72nd pole pair harmonic is a higher-order static magnetic field.

[0089] The air gap harmonic components of the armature magnetic field are analyzed below. The 24-slot, 8-pole armature winding is arranged with an integer number of slots. The three-phase windings are respectively supplied with the same amplitude but different phases. The sinusoidal current at electrical angle, and the three-phase combined armature magnetomotive force can be expressed as:

[0090] (6)

[0091] In the formula, armature magnetomotive force The amplitude of the second harmonic, among which As an intermediate parameter, its purpose is to enable... The values ​​of m are limited to 1, 7, and 13.

[0092] The armature magnetic field generated by the combined armature magnetomotive force under modulation can be expressed as:

[0093] (7)

[0094] when When all values ​​are 1, the amplitude of each harmonic of the armature magnetic field is the largest. The corresponding harmonic amplitude, phase, number of pole pairs and rotational speed are shown in Table 2 below.

[0095] Table 2 Harmonic Characteristics of Armature Magnetic Field Air Gap Magnetic Density ( Take 1 for all)

[0096]

[0097] Table 2 , These are the amplitudes of the first and fifth harmonics of the armature magnetomotive force, respectively.

[0098] Table 2 shows the harmonic characteristics of the armature magnetic field air gap magnetic flux density derived analytically. A finite element model is then established for simulation. Figure 5 (a) is the waveform of the air gap magnetic flux density outside the armature magnetic field. Figure 5 (b) is the waveform of the air gap magnetic flux density within the armature magnetic field. Figure 5 (c) represents the amplitude of the main harmonics of the armature magnetic field air gap flux density. The main harmonics of the armature magnetic field air gap flux density include... Figure 5 The harmonic pole pairs in (c) are 4, 16, 20, 24, 28, 40 and 48, which is consistent with the above magnetic flux density model analysis results.

[0099] Electromagnetic torque can only be generated through the interaction of permanent magnet air gap harmonics and armature magnetic field air gap harmonics with the same harmonic pole pair number and rotational speed. According to... Figure 4 (c) and Figure 5 The analysis in section (c) shows that the pole pairs with higher harmonic content in the permanent magnet magnetic field air gap are 4, 20, 24, 40, 44, 60, and 72. Meanwhile, the pole pairs with higher harmonic content in the armature magnetic field air gap are 4, 16, 20, 24, 28, 40, and 48. Among these, the pole pairs with the same harmonic content mainly include 4, 20, 24, and 40. The following analysis examines the rotational speed, amplitude, and phase of the magnetic fields with these four harmonic pole pairs, and calculates the initial rotor position. The specific parameters are shown in Table 3 below.

[0100] Table 3. Harmonic Characteristics of Air Gap Magnetic Denseness Based on Common Harmonic Pole Pair Count

[0101]

[0102] As shown in Table 3, the permanent magnet air gap harmonics and armature magnetic field air gap harmonics with the same number of harmonic pole pairs (4, 20, 24, 40) have the same rotational speed and can generate electromagnetic torque. In summary, harmonics with 4, 20, 24, and 40 pole pairs coexist in both the permanent magnet and armature magnetic fields and rotate synchronously, thus jointly generating a stable average torque. This torque generation mechanism through the combined action of multiple harmonics is the fundamental reason for the high torque density achieved in this invention. Compared to traditional motors or unidirectional modulation motors that primarily rely on a single pair of magnetic field harmonics, this invention fully utilizes multiple effective harmonics generated by bidirectional modulation, thereby outputting greater torque with the same volume and material usage.

[0103] 6. Performance Verification

[0104] To verify the high torque output capability of the bidirectional modulated dual-rotor vernier motor, it is compared with... Figure 6 A performance comparison analysis of three dual-rotor permanent magnet motor structures was conducted, among which... Figure 6 (a) is a structural diagram of a traditional dual-rotor motor (Model 1); Figure 6 (b) is a structural diagram of a unidirectional modulated dual-rotor motor (Model 2); Figure 6 (c) is a structural diagram of a unidirectional modulated alternating pole dual-rotor motor (Model 3); the motor structure of this invention (Model 4) establishes finite element models of four dual-rotor motor structures, including a traditional unmodulated 24-slot 8-pole motor (Model 1), a 24-slot 40-pole unidirectional modulated motor (Model 2), a 24-slot 40-pole unidirectional modulated alternating pole motor (Model 3), and a 24-slot 40-pole bidirectional modulated motor (Model 4). Model 1, with the smallest number of rotor pole pairs, is used as the benchmark to ensure that the stator and rotor cores are unsaturated. All four structures have the same external dimensions, air gap radius, and air gap length. The motor structural parameters are shown in Table 4 below.

[0105] Table 4 Main parameters of dual rotor motor

[0106]

[0107] At the same rotation speed Under these conditions, finite element comparative analysis was performed on four structures under no-load and loaded conditions. The simulation waveforms of the no-load line back EMF and the harmonic amplitudes of the line back EMF for the four models are as follows: Figure 7 (a) and Figure 7 As shown in (b).

[0108] Simulation results show that the no-load back EMF amplitude of the magnetic field modulation motor is greater than that of the conventional motor (Model 1). The back EMF amplitude of the alternating pole magnetic field modulation motor (Models 3 and 4) is greater than that of the non-alternating pole magnetic field modulation motor (Model 2). Model 4 has the largest no-load back EMF amplitude, low higher harmonic content, and high sinusoidal back EMF. Model 4 exhibits the best no-load performance. Figure 8 The figures show the torque waveforms of the four models at the same speed and current. As can be seen from the figures, the torque of model 4 is significantly higher than that of the other three models, followed by model 3, while the traditional model 1 has the lowest torque.

[0109] In summary, the no-load and load characteristics of the four models were analyzed, and the electromagnetic performance of the four motor structures is shown in Table 5 below. Model 4, a bidirectional modulated dual-rotor permanent magnet vernier motor, exhibits the largest effective value of no-load back EMF and the smallest harmonic THD, along with high waveform sinusoidality. It also boasts the largest output torque and the smallest torque fluctuation. Furthermore, compared to Models 1 and 2, Model 4 uses less permanent magnet. This demonstrates that the electromagnetic performance of the bidirectional modulated dual-rotor permanent magnet vernier motor is the best among the four models, achieving the highest output torque while significantly reducing the amount of permanent magnets required.

[0110] Table 5 Summary of Electromagnetic Performance of Motors

[0111]

[0112] The results are as follows Figure 6 As shown in Table 5, the total output torque of this embodiment (Model 4) reaches It is significantly higher than other models, while having the lowest torque ripple. ), and the amount of permanent magnets used is only Compared to traditional models, it reduces The no-load back EMF waveform also has the highest sinusoidal strength (THD= ),like Figure 8 As shown, this fully demonstrates the comprehensive advantages of the present invention in increasing torque density, reducing torque ripple, and saving permanent magnet materials.

[0113] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A bidirectional modulated double rotor permanent magnet Vernier motor, characterized in that, The motor comprises an outer rotor (1), a stator (2) and an inner rotor (3); the stator (2) is arranged between the inner rotor (3) and the outer rotor (1) and coaxial with the inner rotor (3) and the outer rotor (1), and the inner rotor (3) and the outer rotor (1) are coaxial to output torque; The outer rotor (1) comprises an outer rotor yoke (11), a plurality of outer rotor teeth (12) and outer rotor permanent magnets (13), two adjacent outer rotor teeth (12) form an outer rotor slot, and the outer rotor permanent magnets (13) are arranged in the outer rotor slot; The stator (2) comprises a stator yoke (201), a plurality of outer stator teeth (211), outer armature windings (212), outer stator permanent magnets (213), a plurality of inner stator teeth (221), inner armature windings (222) and inner stator permanent magnets (223); two adjacent outer stator teeth (211) form an outer stator slot, the outer armature windings (212) are arranged in the outer stator slot, and the outer stator permanent magnets (213) are arranged at the slot opening of the outer stator slot; two adjacent inner stator teeth (221) form an inner stator slot, the inner armature windings (222) are arranged in the inner stator slot, and the inner stator permanent magnets (223) are arranged at the slot opening of the inner stator slot; The inner rotor (3) comprises an inner rotor yoke (31), a plurality of inner rotor teeth (32) and inner rotor permanent magnets (33), two adjacent inner rotor teeth (32) form an inner rotor slot, and the inner rotor permanent magnets (33) are arranged in the inner rotor slot; The outer rotor permanent magnets (13) have the same polarity as the inner rotor permanent magnets (33), the outer stator permanent magnets (213) have the same polarity as the inner stator permanent magnets (223), and the outer rotor permanent magnets (13) have the same or opposite polarity as the outer stator permanent magnets (213).

2. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The stator yoke (201) provides a magnetic flux path for an outer magnetic field and serves as a structural component to integrate the stator (2).

3. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 2, wherein, The ratio of the radial thickness of the stator yoke (201) to the radial height of the outer stator teeth (211) is not greater than 0.

2.

4. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The number of outer stator teeth (211) and inner stator teeth (221) is the same, and the positions correspond in the radial direction.

5. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The number of outer rotor teeth (12) and inner rotor teeth (32) is the same, and the positions correspond in the radial direction.

6. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The outer rotor permanent magnets (13), the inner rotor permanent magnets (33), the outer stator permanent magnets (213) and the inner stator permanent magnets (223) are magnetized in parallel, radially or in a Halbach manner.

7. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The outer armature windings (212) and the inner armature windings (222) have the same winding arrangement, and are connected in series or independently powered.

8. The bidirectional modulated double rotor permanent magnet Vernier motor of claim 1, wherein, The number of slots of the inner and outer stators is both Q The number of pole pairs of the inner and outer stator permanent magnets is both P S The number of pole pairs of the inner and outer rotor permanent magnets is both P r , Q , P S , P r and the number of pole pairs of the armature winding P w satisfies: Q = P S =P r +P w and P S ≠ P r ≠ P w .

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