A direct current bias type double-side excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement

Abstract

This invention belongs to the field of magnetic field modulation permanent magnet motor technology, specifically disclosing a DC-biased, dual-excitation magnetic field modulation permanent magnet direct drive motor employing a composite tooth arrangement. Starting from the principle of magnetic field modulation, this invention constructs a novel stator structure on the stator side, combining a concentrated permanent magnet arrangement with a composite tooth structure, and uses a rotor with alternating pole permanent magnet arrangements to achieve bidirectional magnetic field modulation. This, in turn, excites abundant air gap magnetic field harmonic components, significantly improving the motor's torque density. Furthermore, this invention applies a DC-biased AC current to the stator armature winding; the DC component of this current enables dynamic adjustment of the air gap magnetic field, achieving effective magnetic field adjustment without adding a DC excitation winding, thus avoiding space competition issues.

Description

Technical Field

[0001] This invention belongs to the field of magnetic field modulation permanent magnet motor technology, and specifically relates to a DC biased double-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement, which is particularly suitable for application scenarios such as high-speed trains, electric vehicles, and drones. Background Technology

[0002] Permanent magnet direct drive motors have demonstrated significant technological value in various industrial applications due to their high efficiency, high reliability, and low noise and vibration. However, traditional permanent magnet direct drive motors are limited by the pole-slot configuration, resulting in large size and insufficient torque density in applications requiring high torque, making them difficult to apply in scenarios with limited installation space.

[0003] In addition, in special application scenarios such as high-speed trains and electric vehicles, the drive system not only requires a sufficiently large starting and load torque in the low-speed constant torque region, but also needs to achieve a wide speed regulation range in the constant power region. However, traditional permanent magnet motors have a single excitation source and the air gap flux cannot be dynamically adjusted. Field weakening control must rely on injecting a large amplitude direct-axis armature current to counteract the flux generated by the permanent magnet, which not only increases the burden on the controller, but also limits the high-speed operating range of the motor.

[0004] Although hybrid excitation motors can solve the problem of air gap magnetic field adjustment, their stator side usually requires the simultaneous arrangement of DC excitation windings and AC armature windings. The coexistence of the two in a limited space will cause space competition, which will not only increase the complexity of motor design and control, but also weaken the system's magnetic field adjustment flexibility and torque output capability to a certain extent, thus restricting the actual performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a DC-biased, dual-excitation, magnetic field-modulated permanent magnet direct-drive motor employing a composite tooth arrangement. The motor features a novel stator structure combining a concentrated permanent magnet arrangement with a composite tooth structure, coupled with a rotor using alternating pole permanent magnets. This achieves bidirectional magnetic field modulation, exciting abundant air gap magnetic field harmonic components and significantly increasing torque density. Furthermore, a DC-biased AC current is applied to the stator armature windings; the DC component of this current dynamically adjusts the air gap magnetic field, achieving effective magnetization without adding a DC excitation winding and avoiding space competition issues.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A DC biased bilateral excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement includes a stator and a rotor, wherein the stator is located outside the rotor and an air gap is left between the stator and the rotor.

[0008] The stator includes the stator yoke, stator split teeth, and stator straight teeth;

[0009] The stator yoke is circular; there are multiple stator split teeth and stator straight teeth, which are arranged alternately along the inner circumference of the stator yoke to form a composite tooth structure.

[0010] A stator permanent magnet is placed between each stator split tooth and two adjacent stator straight teeth. The magnetization directions of the two stator permanent magnets on different sides of the same stator split tooth are tangentially opposite and both face the stator split tooth, forming a magnet-concentrating permanent magnet arrangement.

[0011] The rotor includes rotor teeth and rotor permanent magnets; the magnetization direction of the rotor permanent magnets is radially outward.

[0012] The stator split teeth are equipped with stator armature windings. The stator armature windings adopt distributed windings. DC bias AC current is passed through the stator armature windings, and the DC component contained in the DC bias AC current is used to achieve magnetization.

[0013] Preferably, the stator split tooth has its inner end split into two sub-tooth structures.

[0014] Preferably, the outer ends of the stator split teeth and the stator straight teeth are connected to the inner circumference of the stator yoke; the inner ends of the stator split teeth and the stator straight teeth extend to the outer circumference of the rotor.

[0015] Preferably, a slot is left between the stator split teeth and the adjacent stator straight teeth to place the stator permanent magnet.

[0016] Preferably, the two stator permanent magnets on different sides of the same stator split tooth are symmetrical about the center line of the stator split tooth.

[0017] Preferably, there are multiple rotor teeth and multiple rotor permanent magnets;

[0018] The rotor teeth and rotor permanent magnets are arranged alternately along the outer circumference of the rotor.

[0019] Preferably, the process of bidirectional magnetic field modulation of the motor of the present invention is as follows:

[0020] A simplified magnetomotive force-permeability model is used to analyze the harmonic characteristics of the air gap magnetic flux density of the motor. The magnetomotive force provides the original magnetic field with different pole pairs, and the permeability converts the pole pairs of the original magnetic field into usable working harmonics through spatial periodic changes. The magnetic field of the stator permanent magnet is modulated by the rotor teeth, and the magnetic field of the rotor permanent magnet is modulated by the composite teeth composed of stator split teeth and stator straight teeth.

[0021] The air gap permeability generated by the rotor side will produce The harmonics will generate a number of magnetomotive force pole pairs in the stator permanent magnet. The harmonics; the air gap harmonic components after the stator permanent magnet magnetomotive force is modulated by the rotor teeth are The air gap permeability generated on its stator side will produce The harmonics will cause the number of magnetomotive force pole pairs of the rotor permanent magnet to increase. The harmonics of the rotor permanent magnet magnetomotive force are modulated by a composite tooth structure consisting of stator split teeth and stator straight teeth, resulting in the air gap harmonic components being: ;

[0022] in Indicates the number of rotor teeth. The total number of stator teeth is the sum of the number of split-tooth structures and straight teeth in the stator. All are coefficients. , ;

[0023] The air gap contains some of the same harmonic components due to the bidirectional modulation effect. ;

[0024] By making full use of the same harmonics in this part to generate back electromotive force and torque, bidirectional magnetic field modulation can be achieved.

[0025] The present invention has the following advantages:

[0026] As described above, this invention relates to a DC-biased, dual-excitation, magnetic field-modulated permanent magnet direct drive motor employing a composite tooth arrangement. By analyzing the air gap magnetic field using a simplified magnetomotive force-permeability model, and based on the principle of magnetic field modulation, this invention proposes a novel stator structure on the stator side that combines a concentrated permanent magnet arrangement with composite teeth (i.e., alternating stator split teeth and stator straight teeth on the stator side). Combined with a rotor employing alternating pole permanent magnet arrangements, this achieves a bidirectional magnetic field modulation effect, thereby exciting abundant harmonic components in the air gap magnetic field. This increases the number and amplitude of effective working harmonics in the air gap magnetic field, significantly improving torque density. Furthermore, this invention introduces a DC-biased alternating current into the stator armature winding. The AC component of this DC-biased alternating current is used to achieve torque output, while the DC component enables dynamic adjustment of the air gap magnetic field. Effective magnetization (magnetization enhancement or weakening) can be achieved without adding a DC excitation winding, thus effectively avoiding space competition problems. The motor described in this invention can not only significantly improve the torque output capability under low-speed conditions, but also effectively expand the speed range of the motor, providing an innovative solution for wide-speed-range direct drive scenarios such as high-speed trains, electric vehicles, and drones. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of a DC-biased, dual-sided excitation magnetic field modulated permanent magnet direct drive motor with a composite tooth arrangement, as described in an embodiment of the present invention; wherein... Figure 1 The arrows in the diagram indicate the magnetization direction of the stator and rotor permanent magnets;

[0028] Figure 2 This is a schematic diagram showing the distribution of unloaded magnetic field lines of the motor in four typical positions according to an embodiment of the present invention; wherein... Figure 2 (a), (b), (c), and (d) in the diagram correspond to the unloaded magnetic field line distributions at 0°, 90°, 180°, and 270°, respectively.

[0029] Figure 3 This is a schematic diagram of the arrangement of the magnetizing permanent magnets used in the motor in this embodiment of the invention;

[0030] Figure 4 A schematic diagram of the magnetic flux linkage of stator A+, A- coils and A-term winding when different DC currents are applied under no-load conditions; Figure 4 (a), (b), and (c) in the figure show the cases of no DC current, negative DC current, and positive DC current, respectively.

[0031] Figure 5 This is a schematic diagram of the air gap magnetic field when different DC currents are applied under no-load conditions; where Figure 5 (a) in the figure shows a schematic diagram of the air gap magnetic field. Figure 5 (b) in the figure is a schematic diagram of the Fourier decomposition harmonics of the air gap magnetic field.

[0032] Figure 6 The graphs show the contrast waveforms and Fourier transforms of the back potential when different DC currents are applied under no-load conditions. Figure 6 In the diagram, (a) represents the waveform of the back electromotive force. Figure 6 (b) in the diagram is a schematic of the Fourier decomposition harmonics of the opposite electromotive force;

[0033] Figure 7 The figures show the torque waveforms of the outer stator armature winding when different DC currents are applied to it in the embodiments of the present invention.

[0034] Wherein: 1-stator, 2-stator yoke, 3-stator split tooth, 4-stator armature winding, 5-stator straight tooth, 6-stator permanent magnet, 7-rotor, 8-rotor permanent magnet, 9-rotor tooth. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] like Figure 1 As shown in the figure, this embodiment describes a DC biased double-sided excitation magnetic field modulation permanent magnet direct drive motor with a composite tooth arrangement, which includes a stator 1, a rotor 7 and a stator armature winding 4.

[0037] The stator 1 includes a stator yoke 2, a stator split tooth 3, and a stator straight tooth 5.

[0038] The stator yoke 2 is circular; there are multiple stator split teeth 3 and stator straight teeth 5, which are arranged alternately along the inner circumference of the stator yoke 2.

[0039] The alternating arrangement here refers to the arrangement of a stator split tooth 3, a stator straight tooth 5, and another stator split tooth 3 along the inner circumference (clockwise or counterclockwise) of the stator yoke 2.

[0040] The structure formed by the alternating arrangement of stator split teeth 3 and stator straight teeth 5 is a composite tooth structure. This composite tooth structure can not only act as a "magnetic field modulator" but also significantly reduce magnetic leakage.

[0041] In addition, the stator spur tooth 5 can also achieve phase isolation, which helps to improve fault tolerance and reliability.

[0042] Specifically, the outer ends of each stator split tooth 3 are connected to the corresponding positions on the inner circumference of the stator yoke 2; the inner ends of each stator split tooth 3 extend to the outer circumference of the rotor 1.

[0043] Similarly, the outer ends of each stator spur tooth 5 are connected to the corresponding positions on the inner circumference of the stator yoke 2; the inner ends of each stator spur tooth 5 extend to the outer circumference of the rotor 1.

[0044] In this embodiment, the inner end of the stator split tooth 3 is split into two sub-tooth structures.

[0045] A stator permanent magnet is placed between each of the stator split teeth 3 and the two adjacent stator straight teeth 5, such as Figure 1 As shown. Here, two adjacent stator spur teeth refer to, for example, those located at... Figure 1 The middle stator split tooth 3 and the stator straight tooth 5 on the left and right sides.

[0046] Taking one of the stator splitting teeth 3 as an example, the opposite side of the same stator splitting tooth 3 (e.g.) Figure 1 The magnetization directions of the two stator permanent magnets 6 (right and left sides of the middle stator split tooth 3) are both along the tangential direction and the magnetization directions of the two are opposite.

[0047] The magnetization direction of both stator permanent magnets 6 is towards the stator split tooth 3 located between them. Both stator permanent magnets 6 are spoke-shaped permanent magnets, and they form a magnetically focused arrangement, such as... Figure 3 As shown, leakage flux is significantly reduced.

[0048] A slot is provided between the stator split tooth 3 and the adjacent stator straight tooth 5 for placing the stator permanent magnet 6. The two stator permanent magnets 6 on different sides of the same stator split tooth 3 are symmetrical about the center line of the stator split tooth 3.

[0049] This method of placing the stator permanent magnets ensures that the structure of the stator permanent magnets is not affected by the stator split teeth 3 and stator straight teeth 5, which can more fully provide the energy source for the magnetic field in the motor air gap, improve the utilization rate of the stator permanent magnets, and at the same time enhance the amplitude of the working harmonic of the air gap magnetic flux density generated by the stator permanent magnets, thereby further improving the torque density.

[0050] This invention is applied in direct-drive scenarios, where extremely high torque density of the motor is required. However, existing dual-excitation field modulation motors often employ alternating pole permanent magnet arrangements on the stator side, resulting in inter-pole magnetic leakage and low permanent magnet utilization. To address this issue, this invention focuses on the stator permanent magnet arrangement, adopting a concentrated magnet arrangement structure, which significantly reduces magnetic leakage. However, because the operating harmonics generated by the concentrated magnet arrangement on the stator side, together with the rotor, do not match the operating harmonics generated by the rotor permanent magnets and the stator, a bidirectional magnetic field modulation effect cannot be achieved. Based on this, the present invention further analyzes the air gap magnetic field using a simplified magnetomotive force-permeability model. Starting from the principle of magnetic field modulation, a novel stator structure combining a magnetically concentrated permanent magnet arrangement with composite teeth (i.e., stator side simultaneously employs stator split teeth and stator straight teeth in alternating arrangement) is proposed. This achieves a bidirectional magnetic field modulation effect, thereby exciting rich harmonic components in the air gap magnetic field, increasing the number and amplitude of effective working harmonics in the air gap magnetic field, and significantly improving the torque density.

[0051] The stator 1 is located outside the rotor 7, and an air gap is left between the stator 1 and the rotor 7. The length of the air gap is related to the power rating of the motor, the permanent magnet material selected, and the processing and assembly technology of the stator 1 and the rotor 7.

[0052] The rotor 7 includes rotor teeth 9 and rotor permanent magnets 8. There are multiple rotor teeth 9 and rotor permanent magnets 8. The rotor permanent magnets 8 are arranged along the outer circumference of the rotor, and similarly, the rotor teeth 9 are also arranged along the outer circumference of the rotor.

[0053] The rotor teeth 9 and the rotor permanent magnets 8 are arranged alternately on the outer circumference of the rotor.

[0054] The alternating arrangement here refers to arranging a rotor tooth 9, a rotor permanent magnet 8, and another rotor tooth 9 along the outer circumference (clockwise or counterclockwise) of the rotor 7.

[0055] The magnetization direction of the rotor permanent magnet 8 is radially outward.

[0056] The stator split tooth 3 is provided with a stator armature winding 4. The stator armature winding 4 adopts a distributed winding. A DC bias AC current is passed through the stator armature winding, and the DC component contained in the DC bias AC current is used to achieve magnetic adjustment.

[0057] The bidirectional magnetic field modulation process of this invention, achieved by employing a concentrated permanent magnet arrangement and a composite tooth structure on the stator side, is as follows:

[0058] A simplified magnetomotive force-permeability model is used to analyze the harmonic characteristics of the air gap magnetic flux density of the motor. The magnetomotive force provides the original magnetic field with different pole pairs, and the permeability converts the pole pairs of the original magnetic field into usable working harmonics through spatial periodic changes. The magnetic field of the stator permanent magnet is modulated by the rotor teeth, and the magnetic field of the rotor permanent magnet is modulated by the composite teeth composed of stator split teeth and stator straight teeth.

[0059] The air gap permeability generated by the rotor side will produce The harmonics will generate a number of magnetomotive force pole pairs in the stator permanent magnet. The harmonics; the air gap harmonic components after the stator permanent magnet magnetomotive force is modulated by the rotor teeth are The air gap permeability generated on its stator side will produce The harmonics will cause the number of magnetomotive force pole pairs of the rotor permanent magnet to increase. The harmonics of the rotor permanent magnet magnetomotive force are modulated by a composite tooth structure consisting of stator split teeth and stator straight teeth, resulting in the air gap harmonic components being: .

[0060] in Indicates the number of rotor teeth. The total number of stator teeth is the sum of the number of split-tooth structures and straight teeth in the stator. All are coefficients. , .

[0061] The air gap contains some of the same harmonic components due to the bidirectional modulation effect. .

[0062] By making full use of the same harmonics in this part to generate back electromotive force and torque, bidirectional magnetic field modulation can be achieved.

[0063] Furthermore, the stator side of this invention adopts a composite tooth structure design, which can fully combine the advantages of stator straight teeth 5 and stator split teeth 3, and can exhibit good performance under different operating conditions. Specifically, the alternating arrangement of stator straight teeth 5 and stator split teeth 3 on the stator side acts as a "magnetic field modulator," which can significantly reduce leakage flux compared to a pure "stator split tooth" structure. At the same time, compared to a pure stator straight tooth structure, the composite tooth structure can significantly reduce the number of modulation teeth, increase the placement space of the stator winding and increase the winding coefficient, thereby improving the overall electrical load capacity and thus increasing the output torque.

[0064] In this embodiment, the stator armature winding 4 adopts a distributed winding. This type of distributed winding has a magnetomotive force waveform that is closer to a sine wave, low harmonic losses, a more uniform interaction between the sinusoidal magnetomotive force and the rotor magnetic field, small torque pulsation, and smoother motor operation.

[0065] like Figure 1 As shown, the stator armature winding 4 includes the stator A-phase winding, the stator B-phase winding, and the stator C-phase winding.

[0066] The stator A-phase winding is composed of two coils, A+ and A-; the stator B-phase winding is composed of two coils, B+ and B-; and the stator C-phase winding is composed of two coils, C+ and C-.

[0067] To achieve magnetization adjustment without adding an extra excitation winding, a DC-biased alternating current (containing both DC and AC components) is passed through the stator armature winding 4. The DC component of the DC-biased alternating current is used to achieve magnetization adjustment. This DC component, combined with the rotor permanent magnet, the stator-side magnetizing permanent magnet arrangement, and the composite tooth structure proposed in this invention, can effectively achieve magnetization adjustment. The formula for the current flowing through the stator armature winding 4 is:

[0068] .

[0069] in , , , , , These represent the current flowing through coils A+, A-, B+, B-, C+, and C-, respectively. To allow alternating current to flow, Let α be the direct current flowing through the circuit, and α be the current angle. For frequency.

[0070] Combination Figure 2 The no-load magnetic flux adjustment process of the motor of the present invention is as follows, showing the four typical rotor positions:

[0071] When rotor 7 is in Figure 2 At the position shown in (a), the center line of rotor tooth 9 is aligned with the center line of stator split tooth 3 where phase A winding is located. At this time, the magnetic reluctance of the magnetic flux path of phase A winding is at its minimum, causing the linked magnetic flux of this phase winding to reach its maximum value (positive peak value). When the rotor... Figure 2 Rotate 90 electrical degrees counterclockwise from the position shown in (a) to Figure 2 At the position shown in (b), the magnetic field distribution of the two coil sides (A+ and A-) of phase A winding is symmetrical. Specifically, the magnetic flux linked by coil sides A+ and A- is equal in magnitude but opposite in direction. Therefore, the magnetic flux generated by the two in phase A winding cancels each other out, resulting in zero total magnetic flux of this phase winding. When rotor 7 continues to rotate counterclockwise by 90 electrical degrees to... Figure 2At the position shown in (c), the center line of rotor tooth 9 is aligned with the center line of stator split tooth 3 again, but at this time the magnetic field polarity is reversed, which makes the direction of magnetic flux through phase A winding opposite to that of the rotor tooth 9. Figure 2 The position shown in (a) is the opposite, thus reaching the minimum value (negative peak value, i.e., the maximum reverse value of the magnetic flux). When rotor 7 further rotates to Figure 2 When the position shown in (d) is rotated 270 electrical degrees from the initial position, the A-phase winding is again in a position similar to Figure 2 The magnetic flux at the position shown in (b) is symmetrically canceled, thus the total magnetic flux returns to zero. Specifically, due to the inherent magnetic flux asymmetry between the stator permanent magnet 6 and the rotor poles (i.e., rotor teeth 9), the flux linkage waveform of a single coil (such as A+) exhibits a sine wave superimposed with DC bias, i.e., it possesses "unipolar characteristics." To form a phase winding, this invention connects two in-phase unipolar coils (A+ and A-) spatially separated by 180 electrical degrees in series. This connection method causes the DC bias components of the two coils to cancel each other out, ultimately resulting in a standard sine wave flux linkage with a multiplied amplitude and alternating positive and negative values ​​at the phase winding end, thereby achieving efficient and smooth magnetic flux regulation.

[0072] The following section explains the working principle of the motor of this invention from the perspective of magnetic field modulation:

[0073] The motor can operate using a "bidirectional magnetic field modulation" effect without a DC bias component. Since both the stator 1 and rotor 7 of the motor adopt a salient pole structure and are respectively embedded with permanent magnets (i.e., stator permanent magnet 6 and rotor permanent magnet 8), both the stator and rotor can simultaneously provide excitation magnetic fields and magnetic field modulation functions. Specifically, when the motor is operating, the stator split teeth 3 and stator straight teeth 5 generate a magnetic field modulation effect on the rotor permanent magnet 8; simultaneously, the rotor teeth 9 also generate a magnetic field modulation effect on the stator permanent magnet 6. The composite tooth structure used on the stator side of this invention achieves bidirectional magnetic field modulation through the modulation of the rotor permanent magnet 8, and the modulation of the stator permanent magnet 6 by the rotor permanent magnet 8, thereby meeting the operating conditions of the motor.

[0074] The following analysis of the air gap magnetic field is performed by establishing a simplified magnetomotive force-permeability model. This explains the process of bidirectional magnetic field modulation achieved by designing the stator teeth as a composite tooth structure after arranging concentrated permanent magnets on the stator side in this invention.

[0075] The stator permanent magnets are arranged in a magnetically focused pattern, and the number of permanent magnet pole pairs is [number missing]. The equivalent magnetomotive force of the generated stator permanent magnet is expressed as:

[0076] .

[0077] in The equivalent magnetomotive force of the stator permanent magnet 6. For the stator permanent magnet Second harmonic amplitude This refers to the total number of stator teeth, which is the sum of the stator split tooth 3 structure and the stator straight teeth 5. The spatial mechanical angle (rad) is referenced to the stator.

[0078] Rotor permeability function Represented as:

[0079] .

[0080] in and The first and second parts represent the rotor magnetic permeability respectively. The amplitude and average value of the second harmonics Represents mechanical angular velocity. This is the initial rotor position. This indicates the number of rotor teeth.

[0081] Therefore, the no-load air gap magnetic flux density generated by the stator permanent magnet 6 modulated by the rotor teeth 9 Represented as:

[0082] .

[0083] As can be seen from the above formula, the air gap magnetic field generated by the stator permanent magnet 6 includes both static and static magnetic fields. Second harmonics, which also include rotation. Second harmonic. Similarly, the magnetomotive force of the rotor permanent magnet. Represented as:

[0084] .

[0085] in For the rotor permanent magnet Second harmonic amplitude.

[0086] Because the stator teeth proposed in this invention adopt a composite tooth structure, the total number of stator teeth participating in modulation, i.e., the total number of sub-teeth in the stator straight tooth 5 and stator split tooth 3 structure, is: Then the stator magnetic permeability function The expression is as follows:

[0087] .

[0088] in and The first and second parts represent the stator magnetic permeability respectively. The amplitude and average value of the second harmonic.

[0089] The air gap magnetic flux density excited by the rotor permanent magnet Represented as:

[0090] .

[0091] As can be seen from the above formula, the air gap magnetic field generated by the rotor permanent magnet includes rotational... Subharmonics and Secondary harmonics.

[0092] In summary, the air gap magnetic flux density excited by stator permanent magnet 6 and the air gap magnetic flux density excited by rotor permanent magnet 8 contain some of the same harmonic components. This portion of harmonics can be fully utilized by setting an appropriate number of winding pole pairs. Under these conditions, the "bidirectional magnetic field modulation effect" is introduced to generate the maximum torque.

[0093] The number of armature winding pole pairs should satisfy the following expression: .

[0094] Conversely, if the stator teeth of the motor of the present invention are all stator straight teeth 5 or all stator split teeth 3, then the common working harmonics cannot be generated, and thus the bidirectional magnetic field modulation effect cannot be achieved.

[0095] Specifically, the rotor magnetic permeability will generate The harmonics will cause the number of pole pairs of the stator permanent magnet to increase. The harmonics, after being modulated by the rotor teeth, are the air gap harmonic components of the stator permanent magnet. When all stator teeth adopt a spur tooth structure, the stator magnetic permeability will generate... The harmonics will cause the number of pole pairs of the rotor permanent magnet to increase. The harmonics of the rotor permanent magnet, after being modulated by the stator, are: It lacks the ability to generate bidirectional magnetic field modulation using common harmonics. Furthermore, when all stator teeth employ a split-tooth structure, its stator magnetic permeability will generate... The harmonics will cause the number of pole pairs of the rotor permanent magnet to increase. The harmonics of the rotor permanent magnet are modulated by the stator, and the air gap harmonic components are... It is also impossible to achieve bidirectional modulation effect to generate working harmonics.

[0096] Compared to structures that use only stator straight teeth 5 or stator split teeth 3, this invention employs a composite tooth structure with stator split teeth 3 and stator straight teeth 5 arranged alternately, and the air gap contains some of the same harmonic components. Therefore, this invention can fully utilize this common harmonic to generate back electromotive force and torque. It is evident that the structure combining a concentrated permanent magnet arrangement with composite teeth on the stator side of this invention is derived from the principle of magnetic field modulation. By utilizing bidirectional magnetic field modulation, richer and higher-amplitude air gap magnetic field working harmonics can be excited, including the first ( ), 17 times ( ), 35 times ( Key operating harmonics, including those mentioned above, synergistically contribute to a significant increase in motor torque density. Figure 5 (b) Figure 5 (a) in the figure represents the air gap magnetic field waveform, which is obtained by Fourier decomposition as the air gap magnetic field harmonics. In addition, when DC current in different directions is applied to the motor, the motor can enter the magnetization or magnetization weakening state.

[0097] The dual-excitation structure proposed in this invention can actively and precisely adjust the distribution and intensity of the magnetic field inside the motor by applying DC currents of different polarities to the excitation coil, thereby achieving flexible flux control. Specifically, taking the stator A-phase winding as an example, Figure 4 (a) in the diagram represents the state of the phase winding when no DC current is applied. Figure 4 (b) in the figure represents the state when a negative DC current is applied. The magnetomotive force generated by this current has a demagnetizing effect on the main magnetic field, which causes the amplitude of the combined magnetic flux to be significantly reduced after the A+ and A- coils are superimposed when the rotor rotates. This reduces the back electromotive force and torque output generated by the stator A-phase winding, and the motor enters the field weakening operation state. Figure 4 (c) represents the state when a positive DC current is applied. Its magnetomotive force enhances the main magnetic field, increasing the amplitude of the combined flux linkage after the A+ and A- coils are superimposed. This strengthens the back electromotive force and torque output of the stator A-phase winding, causing the motor to enter a magnetized operating state. This mechanism enables continuous, online control of the motor's air gap magnetic field.

[0098] Specifically, the stator side employs a composite tooth structure with alternating stator split teeth 3 and stator straight teeth 5, forming a multi-path magnetic conduction, which effectively reduces leakage flux and contributes to improving the power factor. Furthermore, when a reverse DC bias current is applied, the magnetic reluctance in the stator straight tooth 5 region is significantly reduced, making it easier for the demagnetizing flux to close through the stator straight tooth path, thereby effectively weakening the magnetic fields of the stator permanent magnet 6 and the rotor permanent magnet 8, thus achieving magnetization weakening. Similarly, when a forward DC bias current is applied, the magnetic reluctance of the stator straight teeth 5 is appropriately increased by superimposing the magnetic fields of the stator permanent magnet 6 and the rotor permanent magnet 8, and the motor enters a magnetization-enhanced operating state. Therefore, the motor involved in this invention has practical value in applications requiring wide speed range adjustment.

[0099] Figure 6 This diagram shows the opposite electromotive force waveforms and harmonic comparisons of the motor under three conditions: no DC current applied, positive DC current applied, and negative DC current applied. Figure 6 (a) The opposite potential waveform and the harmonics after Fourier decomposition ( Figure 6As shown in (b) of the figure, when a positive DC current is applied to the motor and the air gap magnetic flux is superimposed, the amplitude of the opposite electromotive force increases. When a negative DC current is applied, the air gap magnetic flux is canceled out and the amplitude of the opposite electromotive force decreases. This shows that the magnetic flux can be flexibly adjusted.

[0100] Furthermore, to fully utilize the bidirectional magnetic field modulation effect, the number of pole pairs in the stator armature winding can be set according to the low-order pole pair number, thereby obtaining a higher pole ratio and generating a larger back electromotive force and torque. Because the stator armature winding has a low number of pole pairs, the overall size of the motor is significantly reduced, increasing the motor's torque density. Moreover, when a DC bias current is applied to the stator armature winding, flexible torque adjustment can be achieved, such as... Figure 7 As shown, it can increase torque at low speeds and decrease torque at high speeds, thus expanding the speed range.

[0101] In summary, the motor of the present invention, by constructing a novel stator structure combining a magnetizing permanent magnet and a composite tooth, and in conjunction with a rotor using an alternating pole permanent magnet arrangement, effectively introduces a "bidirectional magnetic field modulation effect," thereby exciting abundant air gap magnetic field harmonic components and significantly improving torque density. At the same time, by using a DC bias current to replace hybrid excitation, it achieves flexible magnetic flux adjustment while solving the winding space competition problem.

[0102] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A DC-biased, dual-sided excitation magnetic field modulation permanent magnet direct drive motor employing a composite tooth arrangement, characterized in that, It includes a stator and a rotor, with the stator located outside the rotor and an air gap between the stator and the rotor; The stator includes the stator yoke, stator split teeth, and stator straight teeth; The stator yoke is circular; there are multiple stator split teeth and stator straight teeth, which are arranged alternately along the inner circumference of the stator yoke to form a composite tooth structure. A stator permanent magnet is placed between each stator split tooth and two adjacent stator straight teeth. The magnetization directions of the two stator permanent magnets on different sides of the same stator split tooth are tangentially opposite and both face the stator split tooth, forming a magnet-concentrating permanent magnet arrangement. The rotor includes rotor teeth and rotor permanent magnets; the magnetization direction of the rotor permanent magnets is radially outward. The stator split teeth are equipped with stator armature windings. The stator armature windings adopt distributed windings. DC bias AC current is passed through the stator armature windings, and the DC component contained in the DC bias AC current is used to achieve magnetization. The process of bidirectional magnetic field modulation of the motor is as follows: A simplified magnetomotive force-permeability model is used to analyze the harmonic characteristics of the air gap magnetic flux density of the motor. The magnetomotive force provides the original magnetic field with different pole pairs, and the permeability converts the pole pairs of the original magnetic field into usable working harmonics through spatial periodic changes. The magnetic field of the stator permanent magnet is modulated by the rotor teeth, and the magnetic field of the rotor permanent magnet is modulated by the composite teeth composed of stator split teeth and stator straight teeth. The air gap magnetic permeability generated by the rotor side will produce The harmonics will generate a number of magnetomotive force pole pairs in the stator permanent magnet. Harmonics; The air gap harmonic components of the stator permanent magnet magnetomotive force modulated by the rotor teeth are: The air gap permeability generated on its stator side will produce The harmonics will cause the number of magnetomotive force pole pairs of the rotor permanent magnet to increase. The harmonics of the rotor permanent magnet magnetomotive force are modulated by a composite tooth structure consisting of stator split teeth and stator straight teeth, resulting in the air gap harmonic components being: ; in Indicates the number of rotor teeth. The total number of stator teeth is the sum of the number of split-tooth structures and straight teeth in the stator. All are coefficients. , ; The air gap contains some of the same harmonic components due to the bidirectional modulation effect. ; By making full use of the same harmonics in this part to generate back electromotive force and torque, bidirectional magnetic field modulation can be achieved.

2. The DC-biased dual-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement according to claim 1, characterized in that, The stator split tooth has its inner end split into two sub-tooth structures.

3. The DC-biased dual-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement according to claim 1, characterized in that, The outer ends of the stator split teeth and stator straight teeth are connected to the inner circumference of the stator yoke; the inner ends of the stator split teeth and stator straight teeth extend to the outer circumference of the rotor.

4. The DC-biased dual-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement according to claim 1, characterized in that, A slot is left between the stator split tooth and the adjacent stator straight tooth to place the stator permanent magnet.

5. The DC-biased dual-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement according to claim 1, characterized in that, Two stator permanent magnets on different sides of the same stator split tooth are symmetrical about the center line of the stator split tooth.

6. The DC-biased dual-sided excitation magnetic field modulation permanent magnet direct drive motor with composite tooth arrangement according to claim 1, characterized in that, There are multiple rotor teeth and rotor permanent magnets; The rotor teeth and rotor permanent magnets are arranged alternately along the outer circumferential direction of the rotor.

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