Magnetic field modulation type permanent magnet servo motor

Abstract

The invention discloses a magnetic field modulation type permanent magnet servo motor, belongs to the field of permanent magnet motors, and aims at solving the problem that an existing magnetic field modulation type permanent magnet servo motor is poor in demagnetization resistance under complex working conditions. The motor comprises a rotor and a stator, the rotor is arranged in the stator, a radial air gap is reserved between the rotor and the stator, and the air gap changes periodically; the rotor comprises a rotor iron core, a permanent magnet array surface-mounted on the outer surface of the rotor iron core, and a sheath sleeved outside the permanent magnet; according to the permanent magnet array, radial magnetizing permanent magnets and tangential magnetizing permanent magnets are alternately arranged according to a Halbach array to form a continuous arc magnetic pole. The tooth portion of the stator is provided with notch structures which are symmetrical about the tooth axis, the symmetrical notch structures of the tooth portion of the stator are combined with periodic changes of an air gap, an air gap magnetic field is directionally constructed into multi-harmonic air gap magnetic conductance, and through modulation of the air gap magnetic field, multiple harmonic components of a permanent magnetic field of the rotor and an armature magnetic field of the stator are circumferentially superposed to output torque.

Description

Technical Field

[0001] The invention relates to a magnetic field modulation type permanent magnet servo motor, belonging to the field of permanent magnet motors. Background Art

[0002] Servo motors are core drive components for high-end equipment such as CNC machine tools, industrial robots, and high-end semiconductor equipment. Their performance directly determines the equipment's processing accuracy, response speed, and energy efficiency. In servo motor applications, represented by the aerospace sector, aircraft engines place extremely stringent restrictions on the volume and weight of motor systems. Demand for indicators such as power density, torque pulsation, and torque density has surged, while also facing the challenge of cooling in harsh, high-temperature environments. Due to its unique operating principle and performance advantages, magnetic field modulated permanent magnet servo motors have become a key technology path to addressing the direct drive needs of low torque pulsation and high torque density. However, existing magnetic field modulated permanent magnet servo motors have weak anti-demagnetization capabilities under complex working conditions, and motor performance needs to be improved. Summary of the Invention

[0003] In order to solve the problem that the existing magnetic field modulation type permanent magnet servo motor has weak anti-demagnetization ability under complex working conditions, the present invention provides a magnetic field modulation type permanent magnet servo motor.

[0004] The present invention provides a magnetic field modulated permanent magnet servo motor, comprising a rotor 1 and a stator 3. The rotor 1 is disposed inside the stator 3, with a radial air gap 2 remaining between the rotor 1 and the stator 3. The air gap 2 varies periodically.

[0005] The rotor 1 includes a rotor core 1-2, a permanent magnet array attached to the outer surface of the rotor core, and a sheath 1-3 sleeved on the permanent magnets; the permanent magnet array is composed of radially magnetized permanent magnets 1-1-1 and tangentially magnetized permanent magnets 1-1-2 alternately arranged in a Halbach array to form continuous arc magnetic poles;

[0006] The teeth of the stator 3 are provided with a notch structure symmetrical about the tooth axis. The symmetrical notch structure of the stator teeth is combined with the periodic change of the air gap to directionally construct a multi-harmonic air gap magnetic permeance. Through the air gap magnetic permeance modulation, multiple harmonic components of the permanent magnetic field of the rotor 1 and the armature magnetic field of the stator 3 are circumferentially superimposed to output torque.

[0007] Preferably, a single rotor pole is composed of a radially magnetized permanent magnet 1-1-1 and a tangentially magnetized permanent magnet 1-1-2, and the mechanical angle θ of the rotor pole satisfies:

[0008]

[0009] Wherein, α is the mechanical angle occupied by an arc-shaped radially magnetized permanent magnet 1-1-1, β is the mechanical angle occupied by an arc-shaped tangentially magnetized permanent magnet 1-1-2, and p is the number of rotor pole pairs.

[0010] Preferably, the material, grade and geometric dimensions of the radially magnetized permanent magnet 1-1-1 and the tangentially magnetized permanent magnet 1-1-2 are independently adjustable, and their parameters meet the anti-demagnetization constraints:

[0011] Constraint 1: I = max(I1,I s )

[0012] Where, I is the amplitude of the motor demagnetization current, I1 is the maximum current amplitude when the motor is working normally, and I s It is the maximum current amplitude of the short-circuit current when the motor is short-circuited;

[0013] Constraint 2:

[0014]

[0015] Where μ r is the relative magnetic permeability of the permanent magnet, N is the number of turns of the stator armature winding, g is the air gap length, h is the b is the height difference between the boss and the groove on the rotor core surface;

[0016] The parameters of the permanent magnet include: H cr is the coercive force of radially magnetized permanent magnet 1-1-1 at 20°C, H crd (t) is the function of the coercive force of the radially magnetized permanent magnet 1-1-1 at the demagnetization point with respect to temperature; W r is the length of the center arc of the circular radial magnetized permanent magnet 1-1-1, T r H is the ring width of the arc-shaped radially magnetized permanent magnet 1-1-1, ct is the coercive force of the tangentially magnetized permanent magnet 1-1-2 at 20°C, H crt (t) is the function of the coercive force of the tangentially magnetized permanent magnet 1-1-2 at the demagnetization point with respect to temperature, W t is the length of the center arc of the circular tangential magnetized permanent magnet 1-1-2, T t It is the ring width of the arc-shaped tangentially magnetized permanent magnet 1-1-2.

[0017] Preferably, the stator 3 includes a stator core 3-1 and a stator winding 3-2; the stator winding 3-2 is arranged inside the stator slot of the stator core 3-1, and the slot opening of the stator slot is on the air gap side; the stator teeth of the stator core 3-1 have a notch at the tooth symmetry axis.

[0018] Preferably, the air gap 2 includes three parts: a uniform annular physical air gap between the stator core 3-1 and the sheath 1-3, an air gap section at the slot of the stator slot, and an air gap section at the stator tooth notch, and the air gap varies periodically.

[0019] Preferably, the air gap permeability Λ of the motor satisfies the following formula:

[0020]

[0021] Where N s is the number of motor slots, i is the permeability order, i=1,2,...,n, n￡3, θ m is the motor position angle, Λ i and θ i are the amplitude and phase of the i-th order permeability component respectively;

[0022] Λ0 is the average magnetic permeability, is the harmonic permeance;

[0023] The annular physical air gap segment between the stator and rotor is used to generate average magnetic permeability;

[0024] The air gap section at the slot of the stator slot and the air gap section at the stator tooth gap are used to edit the harmonic magnetic permeance of multiples of the number of motor slots.

[0025] Beneficial effects of the present invention:

[0026] 1. High anti-demagnetization capability: The permanent magnets are arranged in a Halbach array, and the materials, grades and geometric dimensions of the radially and tangentially magnetized permanent magnets can be independently selected and optimized to meet specific anti-demagnetization constraints, significantly enhancing the motor's anti-demagnetization capability under complex operating conditions (such as high current, short circuit, and high temperature).

[0027] 2. High Magnetic Concentration and Efficiency: The Halbach array concentrates magnetic lines of force on the airgap side and weakens them on the non-airgap side, significantly increasing the airgap flux, reducing the magnetic flux and thickness of the rotor yoke, lowering rotor weight and inertia, and improving system response speed. Simultaneously, the array generates a unilateral, highly sinusoidal permanent magnet magnetic field, effectively reducing unwanted harmonics, lowering motor iron loss, improving efficiency, and helping to reduce cogging torque and torque ripple.

[0028] 3. High torque density and stability: The symmetrical notch structure of the stator teeth, combined with the periodic variation of the air gap, creates specific air gap permeability harmonics (especially harmonics that are multiples of the slot number). Through magnetic field modulation, multiple harmonic components of the permanent magnet field and the armature field can be superimposed in the same direction to output torque, significantly improving the motor's torque output capacity and output stability.

[0029] 4. Comprehensive performance improvement: While improving the anti-demagnetization ability, the present invention comprehensively improves the torque density, efficiency, response speed and running stability of the motor by optimizing the magnetic field and magnetic permeability design. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural schematic diagram of a magnetic field modulation type permanent magnet servo motor according to the present invention;

[0031] Figure 2 Schematic diagram of the structure of the magnetic field modulation permanent magnet servo rotor of the present invention;

[0032] Figure 3 Schematic diagram of the permanent magnet magnetization method of the permanent magnet rotor assembly of the present invention;

[0033] Figure 4 It is a structural schematic diagram of the stator of the present invention;

[0034] Figure 5 Schematic diagram of geometrical dimension parameters of the permanent magnet rotor assembly of the present invention;

[0035] In the figure, 1, rotor, 2, air gap, 3, stator;

[0036] 1-1, rotor permanent magnet, 1-2, rotor core, 1-3, sheath;

[0037] 1-1-1, radially magnetized permanent magnet, 1-1-2, tangentially magnetized permanent magnet;

[0038] 3-1. Stator core, 3-2. Stator winding. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0042] Specific implementation method 1: Figures 1 to 5 This embodiment describes a magnetic field modulated permanent magnet servo motor, comprising a rotor 1 and a stator 3. The rotor 1 is disposed inside the stator 3, with a radial air gap 2 remaining between the rotor 1 and the stator 3. The air gap 2 varies periodically.

[0043] The rotor 1 includes a rotor core 1-2, a permanent magnet array attached to the outer surface of the rotor core, and a sheath 1-3 sleeved over the permanent magnets. The permanent magnet array is composed of radially magnetized permanent magnets 1-1-1 and tangentially magnetized permanent magnets 1-1-2 alternately arranged in a Halbach array to form continuous arc magnetic poles, forming a permanent magnet rotor with a special structure.

[0044] The teeth of the stator 3 are provided with a notch structure that is symmetrical about the tooth axis. The symmetrical notch structure of the stator teeth is combined with the periodic change of the air gap to directionally construct a multi-harmonic air gap permeability. Through the modulation of the air gap permeability, multiple harmonic components of the permanent magnetic field of the rotor 1 and the armature magnetic field of the stator 3 are circumferentially superimposed to output torque. One of the key features of the present invention is that each stator tooth of the stator core 3-1 is designed with a specific notch structure at the position of its symmetry axis. This notch is used to directionally construct the required air gap permeability harmonics. The specific notch structure must be strictly symmetrical about the tooth axis to ensure the phase consistency of the permeability harmonics and avoid the increase of torque pulsation; the notch shape is V-shaped, U-shaped, rectangular or trapezoidal, etc., and the boundary line along the stator core in this shape can be composed of multiple straight lines; this shape is achieved by optimizing the harmonic components of the air gap permeability (mainly N s Multiple harmonics) make the multiple modulated harmonics of the armature magnetic field and the permanent magnet magnetic field work together and superimpose in phase, thereby improving the torque output capacity.

[0045] A single rotor pole consists of a radially magnetized permanent magnet 1-1-1 and a tangentially magnetized permanent magnet 1-1-2. The mechanical angle θ of the rotor pole satisfies:

[0046]

[0047] Wherein, α is the mechanical angle occupied by an arc-shaped radially magnetized permanent magnet 1-1-1, β is the mechanical angle occupied by an arc-shaped tangentially magnetized permanent magnet 1-1-2, and p is the number of rotor pole pairs.

[0048] The present invention arranges radially magnetized permanent magnets and tangentially magnetized permanent magnets alternately on the surface of the rotor core in the form of an optimized Halbach magnet array. The rotor permanent magnets 1-1 are divided into two categories: radially magnetized permanent magnets 1-1-1 and tangentially magnetized permanent magnets 1-1-2. The rotor permanent magnets 1-1 use reasonable permanent magnet brands, materials and geometric size parameters, so that the motor has high anti-demagnetization performance under complex working conditions; the permanent magnets are distributed in the form of a Halbach magnet array, which can gather magnetic lines of force on the side of the permanent magnet close to the air gap and weaken the magnetic lines of force on the other side away from the air gap, thereby improving the magnetic concentration effect, greatly increasing the magnetic flux on the air gap side, and reducing the magnetic flux of the rotor yoke to reduce the thickness of the rotor yoke, effectively reducing the weight and inertia of the rotor, and improving the rapid responsiveness of the system; in addition, the Halbach magnet array can obtain a unilateral high-sinusoidal permanent magnetic field, reduce useless harmonic content, reduce motor iron loss, improve motor efficiency, and also help to reduce cogging torque and torque ripple, thereby improving the motor torque output performance.

[0049] In order to improve the anti-demagnetization capability, the material, grade and geometric dimensions of the radially magnetized permanent magnet 1-1-1 and the tangentially magnetized permanent magnet 1-1-2 are independently adjustable, and their parameters meet the anti-demagnetization constraints:

[0050] Constraint 1: I = max(I1,I s )

[0051] Where, I is the amplitude of the motor demagnetization current, I1 is the maximum current amplitude when the motor is working normally, and I s It is the maximum current amplitude of the short-circuit current when the motor is short-circuited;

[0052] This constraint is used to characterize that the demagnetization resistance is directly related to the magnitude of the demagnetization current in the motor winding.

[0053] Constraint 2: To ensure that the motor has high anti-demagnetization capability under complex operating conditions, the amplitude of the motor demagnetization current I and the permanent magnet parameters must satisfy the following conditions:

[0054]

[0055] Where μ r is the relative magnetic permeability of the permanent magnet, N is the number of turns of the stator armature winding, g is the air gap length, h is the b is the height difference between the boss and the groove on the rotor core surface;

[0056] The parameters of the permanent magnet include: H cr is the coercive force of radially magnetized permanent magnet 1-1-1 at 20°C, H crd (t) is the function of the coercive force of the radially magnetized permanent magnet 1-1-1 at the demagnetization point with respect to temperature; W r is the length of the center arc of the circular radial magnetized permanent magnet 1-1-1, T r H is the ring width of the arc-shaped radially magnetized permanent magnet 1-1-1, ct is the coercive force of the tangentially magnetized permanent magnet 1-1-2 at 20°C, H crt (t) is the function of the coercive force of the tangentially magnetized permanent magnet 1-1-2 at the demagnetization point with respect to temperature, W t is the length of the center arc of the circular tangential magnetized permanent magnet 1-1-2, T t It is the ring width of the arc-shaped tangentially magnetized permanent magnet 1-1-2.

[0057] Reasonable selection of the brand, material and geometric size parameters of the permanent magnet according to the above formula is conducive to improving the anti-demagnetization performance of the permanent magnet rotor, so that the motor has high anti-demagnetization ability under complex working conditions; at the same time, it can enhance the air gap magnetic field of the motor and improve the sinusoidality of the air gap magnetic field, so that the motor can achieve comprehensive improvements in torque output capacity, torque output stability and anti-demagnetization ability of the motor.

[0058] See also Figure 2The stator 3 includes a stator core 3-1 and a stator winding 3-2; the stator winding 3-2 is arranged inside the stator slot of the stator core 3-1, and the notch of the stator slot is on the air gap side; the stator teeth of the stator core 3-1 have a notch at the tooth symmetry axis.

[0059] The air gap 2 includes three parts: a uniform annular physical air gap between the stator core 3-1 and the sheath 1-3, an air gap section at the slot of the stator slot, and an air gap section at the stator tooth notch. The air gap changes periodically.

[0060] The air gap permeability Λ of the motor satisfies the following formula:

[0061]

[0062] Where N s is the number of motor slots, i is the permeability order, i=1,2,...,n, n￡3, θ m is the motor position angle, Λ i and θ i are the amplitude and phase of the i-th order permeability component respectively;

[0063] Λ0 is the average magnetic permeability, is the harmonic permeance;

[0064] The annular physical air gap segment between the stator and rotor is used to generate average magnetic permeability;

[0065] The air gap section at the slot of the stator slot and the air gap section at the stator tooth gap are used to edit the harmonic magnetic permeance of multiples of the number of motor slots.

[0066] Rotor magnetic field: The Halbach array rotor generates a high-sinusoidal, high-amplitude permanent magnetomotive force fundamental wave. The permanent magnetomotive force fundamental wave component is the main component and satisfies the following formula:

[0067]

[0068] Where ω is the motor rotation angular frequency, p is the number of motor pole pairs, j is the permanent magnet order, F pmj and θ j are the amplitude and phase of the j-order permanent magnet magnetomotive force component respectively.

[0069] The periodically changing air gap permeability modulates the permanent magnet magnetomotive force. The permanent magnet magnetic field modulated by the permeability includes a sum modulation component, a difference modulation component, and a permanent magnet magnetic field component of the average permeability effect, as shown in the following formula.

[0070]

[0071] where b pm0 、b pm+ and b pm-They are respectively the permanent magnetic field component of the average magnetic permeability effect, the permanent magnetic sum modulation component and the permanent magnetic difference modulation component.

[0072] Multiple harmonic components of the armature magnetomotive force can output torque and satisfy the following formula:

[0073]

[0074] Among them F ak and θ k are the amplitude and phase of the k-order armature magnetomotive force component respectively.

[0075] It can be seen that the magnetomotive force f generated by the armature current is a Including multiple spatial harmonics; the armature magnetomotive force is also modulated by the air gap magnetic permeability, and the armature magnetic field modulated by magnetic permeability includes the sum modulation component, the difference modulation component and the armature magnetic field component of the average magnetic permeability effect, as shown in the following formula.

[0076]

[0077] where b a0 、b a+ and b a- They are the armature magnetic field component of the average magnetic permeability, the armature and modulation component and the armature difference modulation component respectively.

[0078] After modulation, multiple harmonic components with the same pole pairs and rotation speed will be generated in the permanent magnet magnetic field and the armature magnetic field. These paired magnetic field harmonics interact with each other and can be superimposed in the same direction to produce an average electromagnetic torque. The design of the stator tooth gap optimizes the specific order of magnetic permeability harmonics (mainly N s Multiple harmonics) allow more effective modulated harmonics to participate in the torque output, thereby improving torque density and smoothness. The armature magnetic field and the permanent magnet magnetic field have multiple magnetic field harmonics with the same rotation frequency, can output average torque, and satisfy the following formula:

[0079] iN s ±k=iN s ±jp or

[0080] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A magnetic field modulated permanent magnet servo motor, characterized in that: The invention comprises a rotor (1) and a stator (3), wherein the rotor (1) is arranged inside the stator (3), and a radial air gap (2) is left between the rotor (1) and the stator (3), and the air gap (2) changes periodically; The rotor (1) comprises a rotor core (1-2), a permanent magnet array attached to the outer surface of the rotor core, and a sheath (1-3) sleeved outside the permanent magnet; the permanent magnet array comprises radially magnetized permanent magnets (1-1-1) and tangentially magnetized permanent magnets (1-1-2) alternately arranged in a Halbach array to form continuous arc magnetic poles; The teeth of the stator (3) are provided with a notch structure that is symmetrical about the tooth axis. The symmetrical notch structure of the stator teeth is combined with the periodic change of the air gap to directionally construct a multi-harmonic air gap permeability. Through the modulation of the air gap permeability, multiple harmonic components of the permanent magnetic field of the rotor (1) and the armature magnetic field of the stator (3) are circumferentially superimposed to output torque.

2. The magnetic field modulated permanent magnet servo motor according to claim 1, characterized in that: A single rotor pole consists of a radially magnetized permanent magnet (1-1-1) and a tangentially magnetized permanent magnet (1-1-2). The mechanical angle θ of the rotor pole satisfies: Where α is the mechanical angle occupied by an arc-shaped radially magnetized permanent magnet (1-1-1), β is the mechanical angle occupied by an arc-shaped tangentially magnetized permanent magnet (1-1-2), and p is the number of rotor pole pairs.

3. A magnetic field modulated permanent magnet servo motor according to claim 1 or 2, characterized in that: The materials, grades and geometric dimensions of the radially magnetized permanent magnet (1-1-1) and the tangentially magnetized permanent magnet (1-1-2) are independently adjustable, and their parameters satisfy the anti-demagnetization constraints: Constraint 1: I = max(I1,I s ) Where, I is the amplitude of the motor demagnetization current, I1 is the maximum current amplitude when the motor is working normally, and I s It is the maximum current amplitude of the short-circuit current when the motor is short-circuited; Constraint 2: Where μ r is the relative magnetic permeability of the permanent magnet, N is the number of turns of the stator armature winding, g is the air gap length, h is the b is the height difference between the boss and the groove on the rotor core surface; The parameters of permanent magnets include: H cr is the coercive force of radially magnetized permanent magnet (1-1-1) at 20℃, H crd (t) is the function of the coercive force of the radially magnetized permanent magnet (1-1-1) at the demagnetization point with respect to temperature; W r is the length of the center arc of the circular radially magnetized permanent magnet (1-1-1), T r H is the ring width of the arc-shaped radially magnetized permanent magnet (1-1-1), ct is the coercive force of the tangentially magnetized permanent magnet (1-1-2) at 20°C, H crt (t) is the function of the coercive force of the tangentially magnetized permanent magnet (1-1-2) at the demagnetization point with respect to temperature, W t is the length of the center arc of the circular tangential magnetized permanent magnet (1-1-2), T t It is the ring width of the arc-shaped tangentially magnetized permanent magnet (1-1-2).

4. The magnetic field modulated permanent magnet servo motor according to claim 1, characterized in that: The stator (3) comprises a stator core (3-1) and a stator winding (3-2); the stator winding (3-2) is arranged inside a stator slot of the stator core (3-1), and the slot opening of the stator slot is on the air gap side; the stator teeth of the stator core (3-1) have a notch structure at the tooth symmetry axis.

5. The magnetic field modulated permanent magnet servo motor according to claim 4, characterized in that: The air gap (2) comprises three parts: a uniform annular physical air gap between the stator core (3-1) and the sheath (1-3), an air gap section at the slot of the stator slot, and an air gap section at the stator tooth notch. The air gap varies periodically.

6. The magnetic field modulated permanent magnet servo motor according to claim 5, characterized in that: The air gap permeability Λ of the motor satisfies the following formula: Where N s is the number of motor slots, i is the permeability order, i=1,2,...,n, n￡3, θ m is the motor position angle, Λ i and θ i are the amplitude and phase of the i-th order permeability component respectively; Λ0 is the average magnetic permeability, is the harmonic permeance; The annular physical air gap segment between the stator and rotor is used to generate average magnetic permeability; The air gap section at the slot of the stator slot and the air gap section at the stator tooth gap are used to edit the harmonic magnetic permeance of multiples of the number of motor slots.

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