A bearingless double-sided motor construction method with low suspension force pulsation

Abstract

The present invention discloses a method for constructing a bearingless bilateral motor with low suspension force pulsation. First, a pole-slot matching design scheme based on short-pitch winding harmonic analysis is proposed, so that the even harmonics and modulation amounts generated by the suspension winding using centralized windings will not generate suspension force pulsation with the permanent magnets. While using centralized windings to reduce end losses, it still has a stable suspension force. Secondly, a continuous rotor similar to a cosine shape is proposed to modulate the original air gap magnetic field to generate the required various modulated magnetic potentials. Compared with the original discontinuous, square-shaped rotor, the modulated magnetic potential has a larger fundamental wave amplitude, a smaller harmonic amplitude, a smaller number of harmonics, and a more cosine-like waveform of the air gap magnetic potential. The present invention effectively suppresses the suspension force pulsation caused by the high-order motion harmonics of the magnetic modulation block.

Description

Technical Field

[0001] The present invention relates to the field of modulated bilateral motors, and mainly to a rotor construction method of a modulated bilateral suspension motor. Background Art

[0002] Double-sided motors use two stators, each housing the windings and permanent magnets. This increases the space for the permanent magnets and the armature coils, improving electromagnetic torque and the thermal state of the permanent magnets. Compared to air suspension, magnetic levitation offers the advantages of greater rigidity and load-bearing capacity. It is also adaptable to ultra-clean environments and vacuum manufacturing, eliminating the need for precision machining of the air bearing support surface, thus reducing system manufacturing costs. Consequently, it is widely used.

[0003] At present, there is no relatively correct and unified theory on the rotor construction method of bilateral motors. Therefore, for a bilateral motor with a fixed physical structure, it is necessary to find a rotor construction method to further optimize the motor performance.

[0004] The doctoral dissertation, "Basic Research on Bearingless Thin-Layer Motors, Nanjing University of Aeronautics and Astronautics, 2009," proposed that a motor can generate a controllable levitation force if the armature magnetic field and the levitation magnetic field differ by one pole. However, this method targets traditional non-modulated motors and is not directly applicable to modulated double-sided motors. It is necessary to consider the modulation effect in double-sided motors, add new constraints, and redesign the levitation winding method.

[0005] The construction method proposed in the document "Construction Method for a Bilateral Suspension Motor (Application No. 202210891366.7)" eliminates the levitation force pulsation caused by the fundamental wave of the suspension magnetic field and the stationary wave of the permanent magnet. However, it does not account for the levitation force pulsation caused by the harmonics of the armature magnetic field and the harmonics of the permanent magnet before and after modulation. The bearingless magnetic gear bilateral motor constructed using the construction method proposed in the document "Construction Method for a Bilateral Suspension Motor (Application No. 202210891366.7)" still exhibits significant levitation force pulsation.

[0006] The method proposed in the document "General Construction Method for Bearingless Magnetic Geared Bilateral Motors with Global Cancellation of Fundamental Harmonics (Application No. 202211323058.0)" is divided into three levels: preliminary optimization, cancellation constraints between the armature magnetic field harmonics and the permanent magnet harmonics before modulation (Constraint 1), and cancellation constraints between the armature magnetic field harmonics and the permanent magnet harmonics after modulation (Constraint 2). Preliminary optimization can and can only reduce the pulsation caused by the fundamental wave of the suspension magnetic field and the stationary wave of the permanent magnet. On this basis, Constraint 1 is proposed to reduce the suspension force pulsation caused by the armature magnetic field harmonics and the permanent magnet harmonics before modulation, and Constraint 2 is proposed to reduce the suspension force pulsation caused by the armature magnetic field harmonics and the permanent magnet harmonics after modulation. By using the principle of global cancellation of fundamental harmonics, the suspension force pulsation of the bearingless magnetic geared bilateral motor is effectively reduced, overcoming the shortcomings of traditional and existing suspension motor construction methods.

[0007] However, the method proposed in the document "General Construction Method for Bearingless Magnetic Gear Bilateral Motor with Global Cancellation of Fundamental Harmonics (Application No. 202211323058.0)" still has the following shortcomings:

[0008] (1) The suspension winding in this method must adopt a distributed full-pitch winding structure to reduce the pulsation of the suspension force. The ends of the distributed full-pitch winding structure are longer (copper loss is larger) and the slot fill rate is not high.

[0009] (2) In this method, the magnetic block is a moving component, and the pulsation of the suspension force caused by the high-order motion harmonics of the magnetic block is not effectively suppressed.

[0010] (3) In this method, the modulation blocks are multiple separate square iron blocks. In actual processing, a fixture is required to position them into a whole. The presence of the fixture increases the effective air gap, reducing the power density and suspension force density. Summary of the Invention

[0011] Purpose of the Invention: To address the problems encountered in the aforementioned background technology, the present invention provides a bearingless, bilateral motor construction method with low suspension force pulsation. The windings are centralized, reducing end losses. Furthermore, the magnetic tuning block features a continuous sinusoidal structure, effectively suppressing suspension force pulsation caused by the higher-order harmonics of the tuning block's motion. This eliminates the need for a fixing device, improving both power density and suspension force density.

[0012] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0013] 1. A bearingless double-sided motor construction method with low suspension force pulsation. The number of permanent magnet pole pairs and the number of modulation blocks are preliminarily determined, and the magnetic potential of the permanent magnet is modified to be sinusoidal. The Fourier decomposition method is used to determine the number of fundamental pole pairs of the permanent magnet's rotation and stationary waves. The suspension winding is wound according to the conditions for the suspension force generation, and constraints are set to eliminate the suspension force pulsation caused by the suspension magnetic field fundamental wave and the permanent magnet stationary wave. The sinusoidal permanent magnet magnetic potential is Fourier decomposed to determine the number of pole pairs generated by the permanent magnet in the motor air gap is p. s The static magnetic field of the permanent magnet is generated by a magnetic field with a pole pair number of n. r After the modulation of the modulation block, the number of pole pairs generated in the air gap is kn r +(2i-1)p s and|kn r -(2i-1)p s | a rotating magnetic field, where k = 1, 2, 3, ..., i = 1, 2, 3, ..., and the number of pole pairs is kn r +(2i-1)p s The rotation speed of the magnetic field is The number of pole pairs is kn r -(2i-1)p s The rotation speed of the magnetic field is Ω r is the mechanical angular velocity of the rotor modulation block. When the number of pole pairs of the rotating magnetic field in the air gap is (n r -p s ) satisfies(n r -p s )=p s -2, the suspension winding is wound into (n r -p s -1) pairs of poles; when the number of pole pairs of the rotating magnetic field in the air gap is (n r -p s ) satisfies(n r -p s )=p s +2, the suspension winding is wound into (n r -p s +1) pairs of poles; when the number of pole pairs of the rotating magnetic field in the air gap is (n r -p s ) does not satisfy (n r -p s )=p s ±2, the suspension winding is wound into (n r -p s -1) opposite pole or (n r -p s +1). For the P determined above s 、n rThe armature magnetic field harmonics and the permanent magnet harmonics before the modulation of the suspension magnetic field pole pair number are constrained to cancel each other, that is, the armature magnetic field of the suspension winding before modulation and the permanent magnet harmonics do not have such a relationship, the pole pair number of a certain armature magnetic field and a certain harmonic of the permanent magnet differs by 1 and the electrical angular frequency of the two is not equal. s 、n r The armature magnetic field harmonics and the permanent magnet harmonics after the suspension magnetic field pole pair number is modulated, that is, the armature magnetic field of the modulated suspension winding and the permanent magnet harmonics do not have such a relationship, the pole pair number of a certain armature magnetic field and a certain harmonic of the permanent magnet differs by 1 and the electrical angular frequency of the two is not equal. P is determined by the above constraints. s 、n r The number of pole pairs of the suspension magnetic field needs to be further screened, and the steps are as follows:

[0014] 1-1, 2(|n r -P s |±1) cannot be compared with P s The difference is 1, and 2(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0015] 1-2, 4(|n r -P s |±1) cannot be compared with P s The difference is 1, and 4(|n r -P s |±1) cannot be combined with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0016] 1-3, 8(|n r -P s |±1) cannot be compared with P s The difference is 1, and 8(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0017] 1-4, 2(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 2(|nr -P s |±1)+n r Cannot be used with |2n r ±P s The difference between | is 1.

[0018] 1-5, 2(|n r -P s |±1)-n r Cannot be used with |n r ±P s The difference between | is 1, and 2(|n r -P s |±1)-n r Cannot be used with P s The difference is 1.

[0019] 1-6, 4(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1)+n r Cannot be used with P s The difference is 1.

[0020] 1-7, 4(|n r -P s |±1)-n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1)-n r Cannot be used with |2n r ±P s The difference between | is 1.

[0021] 1-8, 4(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1)+n r Cannot be used with |2n r ±P s The difference between | is 1.

[0022] 1-9, 2(|n r -P s |±1)-n r Cannot be used with |nr ±P s The difference between | is 1, and 2(|n r -P s |±1)-n r Cannot be used with P s The difference is 1, and 2(|n r -P s |±1)-n r Cannot be used with |2n r ±P s The difference between | is 1.

[0023] Preferably, the number of suspended pole pairs determined through screening is W, and the number of designed external stator slots is 2*3*W, so that the suspended winding is 3-phase and the winding form is a centralized winding.

[0024] Preferably, the number of pole pairs of the magnetic tuning block determined after screening is n r According to the number of modulation blocks, the required cosine function period is determined, that is, the value of ω is determined; a cosine function model is constructed, that is, the mathematical model of mcosωθ+B; the Fourier decomposition method is used to determine the size of other parameters of the constructed cosine function model; according to the various parameters of the function model, a continuous rotor with a cosine function shape is constructed within the range of 360°. Assume that the number of modulation blocks is n r , then the period of the cosine function of the required mathematical model is Also because So finally ω=n rThe parameter m represents the amplitude of the constructed cosine function, while B represents the size of the thinnest part of the cosine-shaped rotor. The sizes of these two parameters need to be finally confirmed based on actual needs and the subsequent Fourier decomposition (under the premise of ensuring mechanical strength, the smaller the value of B, the better; under the premise of ensuring that the motor does not have a swept bore and meets mechanical installation requirements, the larger the value of m, the better). Because the position of the permanent magnet on the inner stator is fixed, the expression of its magnetic potential is only related to the angle θ distributed along the air gap radius. According to the setting of the permanent magnet of the motor, the expression of the magnetic potential distributed along the air gap radius under the permanent magnet magnetic field, F(θ), is derived; the air gap magnetic resistance P(θ, t) of the motor is further derived. Since the rotor rotates continuously in the air gap, the magnetic resistance P is not only related to the angle θ distributed along the air gap radius, but also to the time t. Since the air gap magnetic flux is equal to the air gap magnetomotive force multiplied by the air gap magnetic resistance, the expression of the air gap magnetic flux of the motor can be obtained as B(θ, t) = F(θ) * P(θ, t). After obtaining the expression for the air gap flux density, the remaining parameters m and B of the cosine function are selected based on the desired functionality and actual requirements. The parameters of the function model are currently known, and a rotor model is established based on these parameters. Its appearance is specifically described as follows: the rotor's outer contour is the shape of the cosine function, the inner contour is circular, and the center is filled with magnetic material. The overall shape conforms to the function shape of mcosωθ+B. Simply put, if the inner contour is the X-axis direction of the rectangular coordinate, and the direction perpendicular to the inner contour outward is the positive Y-axis direction, then the rotor's shape is the cosine function translated in the positive Y-axis direction by a distance B. The portion enclosed by the cosine function and the X-axis is the portion filled with magnetic material.

[0025] Preferably, the P determined after preliminary optimization s 、n r The cancellation constraints of the armature magnetic field harmonics and the permanent magnet harmonics before the pole pair number of the suspension magnetic field is modulated:

[0026] If the number of suspended pole pairs obtained by preliminary optimization is |n r -P s |+1, then |n r -P s |+1 needs to meet the following constraints:

[0027] (1)|n r -P s |+1≠P s ±1 and |n r -P s |+1≠2n r +P s ±1 and |n r -P s |+1≠3n r +P s ±1 and |n r -P s|+1≠|2n r -P s |±1 and|n r -P s |+1≠|3n r -P s |±1;

[0028] (2)5(|n r -P s |+1)≠P s ±1 and 5(|n r -P s |+1)≠2n r +P s ±1 and 5(|n r -P s |+1)≠3n r +P s ±1 and 5(|n r -P s |+1)≠|2n r -P s |±1 and 5(|n r -P s |+1)≠|3n r -P s |±1;

[0029] (3)7(|n r -P s |+1)≠P s ±1 and 7(|n r -P s |+1)≠2n r +P s ±1 and 7(|n r -P s |+1)≠3n r +P s ±1 and 7(|n r -P s |+1)≠|2n r -P s |±1 and 7(|n r -P s |+1)≠|3n r -P s |±1 and

[0030] 7(|n r -P s |+1)≠n r +P s ±1 and 7(|n r -P s |+1)≠|n r -Ps |±1;

[0031] If the number of suspended pole pairs obtained by preliminary optimization is |n r -P s |-1, then |n r -P s |-1 needs to satisfy the following constraints:

[0032] (1)|n r -P s |-1≠P s ±1 and |n r -P s |-1≠2n r +P s ±1 and |n r -P s |-1≠3n r +P s ±1 and |n r -P s |-1≠|2n r -P s |±1 and|n r -P s |-1≠|3n r -P s |±1;

[0033] (2)5(|n r -P s |-1)≠P s ±1 and 5(|n r -P s |-1)≠2n r +P s ±1 and 5(|n r -P s |-1)≠3n r +P s ±1 and 5(|n r -P s |-1)≠|2n r -P s |±1 and 5(|n r -P s |-1)≠|3n r -P s |±1;

[0034] (3)7(|n r -P s |-1)≠P s ±1 and 7(|n r -P s |-1)≠2n r +P s±1 and 7(|n r -P s 1-1)≠3n r +P s ±1 and 7(|n r -P s |-1)≠|2n r -P s |±1 and 7(|n r -P s |-1)≠|3n r -P s |±1 and 7(|n r -P s |-1)≠n r +P s ±1 and 7(|n r -P s |-1)≠|n r -P s |±1.

[0035] Preferably, the P determined by the cancellation constraint of the armature magnetic field harmonics and the permanent magnet harmonics before modulation is s 、n r The cancellation constraints of the armature magnetic field harmonics and the permanent magnet harmonics after the pole pairs of the suspension magnetic field are modulated are:

[0036] If the number of suspended pole pairs obtained by the optimization of the armature magnetic field harmonics before modulation and the permanent magnet harmonics is |n r -P s |+1, then |n r -P s |+1 needs to meet the following constraints:

[0037] (1)|n r -P s |+1+n r ≠P s ±1 and |n r -P s |+1+n r ≠n r +P s ±1 and |n r -P s |+1+n r ≠3n r +P s ±1 and |n r -P s |+1+n r ≠|n r -P s |±1 and|n r -P s |+1+nr ≠|3n r -P s |±1;

[0038] (2)||n r -P s |+1-n r |≠n r +P s ±1 and ||n r -P s |+1-n r |≠2n r +P s ±1 and ||n r -P s |+1-n r |≠3n r +P s ±1 and ||n r -P s |+1-n r |≠|2n r -P s |±1 and||n r -P s |+1-n r |≠|3n r -P s |±1 and||n r -P s |+1-n r |≠|n r -P s |±1

[0039] (3)|n r -P s |*5+5+n r ≠P s ±1 and |n r -P s |*5+5+n r ≠n r +P s ±1 and |n r -P s |*5+5≠3n r +P s ±1 and |n r -P s |*5+5+n r ≠|n r -P s |±1 and|n r -P s |*5+5+n r ≠|3n r -P s|±1;

[0040] (4)||n r -P s |*5+5-n r |≠n r +P s ±1 and ||n r -P s |*5+5-n r |≠2n r +P s ±1 and ||n r -P s |*5+5-n r |≠3n r +P s ±1 and ||n r -P s |*5+5-n r |≠|2n r -P s |±1 and||n r -P s |*5+5-n r |≠|3n r -P s |±1 and||n r -P s |*5+5-n r |≠|n r -P s |±1;

[0041] (5)|n r -P s |*7+7+n r ≠2n r +P s ±1 and |n r -P s |*7+7+n r ≠n r +P s ±1 and |n r -P s |*7+7≠3n r +P s ±1 and |n r -P s |*7+7+n r ≠|n r -P s |±1 and|n r -P s |*7+7+n r ≠|3n r -P s |±1 and|nr -P s |*7+7+n r ≠|2n r -P s |±1;

[0042] (6)||n r -P s |*7+7-n r |≠n r +P s ±1 and ||n r -P s |*7+7-n r |≠2n r +P s ±1 and ||n r -P s |*7+7-n r |≠3n r +P s ±1 and ||n r -P s |*7+7-n r |≠|2n r -P s |±1 and||n r -P s |*7+7-n r |≠|3n r -P s |±1 and||n r -P s |*7+7-n r |≠|n r -P s |±1 and||n r -P s |*7+7-n r |≠P s ±1;

[0043] If the number of suspended pole pairs obtained by the optimization of the armature magnetic field harmonics and the permanent magnet harmonics before modulation is |n r -P s |-1, then |n r -P s |-1 needs to satisfy the following constraints:

[0044] (1)|n r -P s |-1+n r ≠P s ±1 and |n r -P s |-1+n r ≠n r +Ps ±1 and |n r -P s |-1+n r ≠3n r +P s ±1 and |n r -P s |-1+n r ≠|n r -P s |±1 and|n r -P s |-1+n r ≠|3n r -P s |±1;

[0045] (2)||n r -P s |-1-n r |≠n r +P s ±1 and ||n r -P s |-1-n r |≠2n r +P s ±1 and ||n r -P s |-1-n r |≠3n r +P s ±1 and ||n r -P s |-1-n r |≠|2n r -P s |±1 and||n r -P s |-1-n r |≠|3n r -P s |±1 and||n r -P s |-1-n r |≠|n r -P s |±1

[0046] (3)|n r -P s |*5-5+n r ≠P s ±1 and |n r -P s |*5-5+n r ≠n r +P s ±1 and |n r -Ps |*5-5≠3n r +P s ±1 and |n r -P s |*5-5+n r ≠|n r -P s |±1 and|n r -P s |*5-5+n r ≠|3n r -P s |±1;

[0047] (4)||n r -P s |*5-5-n r |≠n r +P s ±1 and ||n r -P s |*5-5-n r |≠2n r +P s ±1 and ||n r -P s |*5-5-n r |≠3n r +P s ±1 and ||n r -P s |*5-5-n r |≠|2n r -P s |±1 and||n r -P s |*5-5-n r |≠|3n r -P s |±1 and||n r -P s |*5-5-n r |≠|n r -P s |±1;

[0048] (5)|n r -P s |*7-7+n r ≠2n r +P s ±1 and |n r -P s |*7-7+n r ≠n r +P s ±1 and |n r -P s|*7-7≠3n r +P s ±1 and |n r -P s |*7-7+n r ≠|n r -P s |±1 and|n r -P s |*7-7+n r ≠|3n r -P s |±1 and|n r -P s |*7-7+n r ≠|2n r -P s |±1;

[0049] (6)||n r -P s |*7-7-n r |≠n r +P s ±1 and ||n r -P s |*7-7-n r |≠2n r +P s ±1 and ||n r -P s |*7-7-n r |≠3n r +P s ±1 and ||n r -P s |*7-7-n r |≠|2n r -P s |±1 and||n r -P s |*7-7-n r |≠|3n r -P s |±1 and||n r -P s |*7-7-n r |≠|n r -P s |±1 and

[0050] ||n r -P s |*7-7-n r |≠P s ±1.

[0051] Beneficial effects:

[0052] (1) Since the present invention proposes a pole-slot matching design scheme based on short-distance winding harmonic analysis for screening conditions 1-1 to 1-9, the even harmonics and their modulation amounts generated by the centralized winding of the suspension winding will not generate suspension force pulsations with the permanent magnet. While the centralized winding reduces end losses, it still has a stable suspension force.

[0053] (2) The design of the continuous pole rotor reduces the suspension force pulsation introduced by the high-frequency motion harmonics of the traditional magnetic tuning block. The specific comparison is as follows:

[0054] First, the specific steps of the air gap magnetic flux expression of the continuous rotor of the present invention are as follows:

[0055] Step S1: Using the Fourier decomposition method, since the permanent magnet is stationary on the inner stator surface, the Fourier expression of the permanent magnet magnetic potential is:

[0056]

[0057] Where θ1 is the semi-arc angle of the permanent magnet, θ3 is the semi-arc angle of the permanent magnet plus the stator tooth arc angle, F PM is the magnetomotive force amplitude of the permanent magnet.

[0058] At this time, the number of modulation blocks is n r , the cosine function model of the modulation block is

[0059]

[0060] The Fourier expression of the air gap permeance of the modulation block is:

[0061] P(θ,t)=B+mcosn r (θ-Ω r t)

[0062] Among them, Ω r is the mechanical speed of the rotor.

[0063] Since the air gap magnetic flux density is equal to the product of magnetomotive force and air gap magnetic permeance, the Fourier expression of the air gap magnetic flux density is:

[0064]

[0065] For comparison, the expression of air gap flux density after modulation by traditional discontinuous, block-shaped modulation block is derived here.

[0066] The Fourier expression of the air gap permeance of the traditional modulation block is:

[0067]

[0068] Where θ2 is the half-arc angle of the modulation block, P0 is the DC component of the magnetic permeance, and P2 is half of the difference between the peak and valley values ​​of the magnetic permeance waveform.

[0069] Then the Fourier expression of the air gap magnetic flux density is obtained as follows:

[0070]

[0071] By comparison, it is found that in the air gap magnetic flux of the present invention, there is (2i-1)p s +n r The harmonics of the opposite poles, and the air gap flux density generated by the traditional modulation block has (2i-1)p s +kn r The harmonic content of the opposite poles is significantly increased. That is to say, after using the modulation block of the present invention, the harmonic content in the air gap magnetic field will be significantly reduced after the magnetic field modulation effect. And according to different needs, after adopting different parameters, it is possible to achieve the effect of enhancing the fundamental amplitude, reducing the harmonic amplitude, and reducing the number of harmonics. Ultimately, the air gap magnetic field is made more cosine in waveform, reducing the harmonic loss of the motor, improving the performance of the motor, and making up for the shortcomings of the traditional modulation block in the modulated bilateral suspension motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is the structural diagram of the traditional rotor modulation block.

[0073] Figure 2 It is a structural diagram of the rotor modulation block of the present invention.

[0074] Figure 3 This is a structural detail diagram of the rotor modulation block of the present invention.

[0075] Figure 4 This is the overall structural diagram of the bilateral motor.

[0076] Figure 5 It is the air gap magnetic flux waveform of the permanent magnet.

[0077] Figure 6 It is a Fourier decomposition diagram of the air gap magnetic flux waveform of the permanent magnet.

[0078] Figure 7 It is a waveform diagram of the air gap flux density after adding a permanent magnet to the traditional modulation block in the document "General construction method of bearingless magnetic gear bilateral motor with global cancellation of fundamental harmonics (application number 202211323058.0)".

[0079] Figure 8 It is a Fourier decomposition diagram of the waveform of the air gap magnetic density after the permanent magnet is added to the document "General construction method of bearingless magnetic gear bilateral motor with global cancellation of fundamental harmonics (application number 202211323058.0)".

[0080] Figure 9It is a waveform diagram of the air gap magnetic flux density after the permanent magnet is added with the modulation block of the present invention.

[0081] Figure 10 It is a Fourier decomposition diagram of the waveform of the air gap magnetic flux after the permanent magnet is added with the modulation block of the present invention.

[0082] Figure 11 This is a waveform diagram of the suspension force after the suspension motor is equipped with the modulation block of the present invention.

[0083] Figure 12 It is a suspension force waveform diagram after the suspension motor is added with a permanent magnet and the traditional modulation block in the document "General construction method of bearingless magnetic gear bilateral motor with global cancellation of fundamental harmonics (application number 202211323058.0)". DETAILED DESCRIPTION

[0084] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the embodiments described herein are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0085] The present invention provides a method for constructing a rotor of a bilateral suspension motor. The method adopts a commonly used bilateral motor structure. The bilateral motor has a partitioned stator, an outer stator with 36 slots, an inner stator with a disc, and 14 intermediate rotor modulation blocks. The inner stator is a permanent magnet surface-mounted NS radial magnetization with a pole pair number P. S =9. Therefore, in this specific bilateral motor, the number of rotor modulation blocks n r =14, where the rotor modulation block structure is shown in Figure 1 As shown. s =9,n r =14 satisfies the following constraints:

[0086] 1-1, 2(|n r -P s |±1) cannot be compared with P s The difference is 1, and 2(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0087] 1-2, 4(|n r -P s |±1) cannot be compared with P s The difference is 1, and 4(|n r -P s |±1) cannot be combined with |n r ±P sThe difference between | is 1, and 4(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0088] 1-3, 8(|n r -P s |±1) cannot be compared with P s The difference is 1, and 8(|n r -P s |±1) cannot be combined with |2n r ±P s The difference between | is 1.

[0089] 1-4, 2(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 2(|n r -P s |±1)+n r Cannot be used with |2n r ±P s The difference between | is 1.

[0090] 1-5, 2(|n r -P s |±1)-n r Cannot be used with |n r ±P s The difference between | is 1, and 2(|n r -P s |±1)-n r Cannot be used with P s The difference is 1.

[0091] 1-6, 4(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1)+n r Cannot be used with P s The difference is 1.

[0092] 1-7, 4(|n r -P s |±1)-n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -Ps |±1)-n r Cannot be used with |2n r ±P s The difference between | is 1.

[0093] 1-8, 4(|n r -P s |±1)+n r Cannot be used with |n r ±P s The difference between | is 1, and 4(|n r -P s |±1)+n r Cannot be used with |2n r ±P s The difference between | is 1.

[0094] 1-9, 2(|n r -P s |±1)-n r Cannot be used with |n r ±P s The difference between | is 1, and 2(|n r -P s |±1)-n r Cannot be used with P s The difference is 1, and 2(|n r -P s |±1)-n r Cannot be used with |2n r ±P s The difference between | is 1.

[0095] Since the above constraints are met, the even harmonics and their modulation generated by the centralized winding of the suspension winding will not produce suspension force pulsation with the permanent magnet. The centralized winding reduces the end loss (such as Figure 4 ), still has a stable suspension force, such as Figure 11 shown.

[0096] Details of the rotor modulation block are shown in the figure below. Figure 3 As shown, the overall structure of the bilateral motor is shown in Figure 4. The arrows indicate the magnetizing direction of the inner stator permanent magnet, and the shape of the permanent magnet can be modified.

[0097] Step S1: Using the Fourier decomposition method, since the permanent magnet is stationary on the inner stator surface, the Fourier expression of the permanent magnet magnetic potential is:

[0098]

[0099] Where θ1 is the semi-arc angle of the permanent magnet, θ3 is the semi-arc angle of the permanent magnet plus the stator tooth arc angle, F PM is the magnetomotive force amplitude of the permanent magnet.

[0100] Step S2: The number of modulation blocks selected is 12, and the cosine function model parameters of the modulation blocks are selected as

[0101] cos14θ+2

[0102] The Fourier expression of the air gap permeance of the modulation block is:

[0103] P(θ,t)=2+cos12(θ-Ω r t)

[0104] Among them, Ω r is the mechanical speed of the rotor.

[0105] Since the air gap magnetic flux density is equal to the product of magnetomotive force and air gap magnetic permeance, the Fourier expression of the air gap magnetic flux density is:

[0106]

[0107] Step S3: Construct a rotor for a modulated bilaterally suspended motor according to the present invention. The rotor's outer contour is a cosine function, its inner contour is circular, and its center is filled with magnetically conductive material. The overall shape conforms to the function shape of mcosωθ+B. Simply put, if the inner contour is the X-axis direction of the rectangular coordinate system, and the direction perpendicular to the inner contour is the positive Y-axis direction, then the rotor's shape is the cosine function translated in the positive Y-axis direction by a distance B. The portion enclosed by the cosine function and the X-axis is the portion filled with magnetically conductive material.

[0108] Next, we modeled and simulated the model in MAXWELL simulation software to verify the above conclusions.

[0109] 1. Simulate the permanent magnet first

[0110] The air gap magnetic flux waveform of the permanent magnet is as follows Figure 5 As shown, the Fourier decomposition of the air gap magnetic flux waveform of the permanent magnet is as follows Figure 6 As shown, it can be seen that the constructed permanent magnet basically only has fundamental wave content, and the harmonic amplitude is almost 0, which basically eliminates the interference of the permanent magnet magnetic potential harmonics on the simulation verification.

[0111] 2. For comparison, after adding the traditional modulation block, simulation is performed

[0112] After adding the traditional modulation block, the waveform of the air gap magnetic flux density is as follows: Figure 7 As shown, the Fourier decomposition of the air gap magnetic flux waveform is as follows Figure 8 As shown, observe Figure 7 It can be seen that the waveform of the air gap magnetic flux is severely distorted and the cosine difference is large. Figure 8 , there are many harmonic contents in the air gap magnetic potential.

[0113] 3. After adding the modulation block of the present invention, the simulation

[0114] After adding the modulation block of the present invention, the waveform of the air gap magnetic flux density is as follows: Figure 9 As shown, the Fourier decomposition of the air gap magnetic flux waveform is as follows Figure 10 First, by comparing the waveform of the air gap magnetic density, it can be found that the cosine property of the waveform of the air gap magnetic density with the modulation block of the present invention is better, which means that the harmonic content is less; by comparing the Fourier decomposition diagram, it can be clearly found that the harmonic content in the air gap magnetic density with the modulation block of the present invention is significantly reduced compared with the traditional modulation block; by comparing the amplitude data diagram, it can be found that the amplitude of the fundamental wave in the air gap with the modulation block of the present invention is greatly enhanced, and the increase is far greater than that of the traditional modulation block.

[0115] 4. The levitation force of the levitation motor after adding the modulation block of the present invention

[0116] The suspension force of the suspension motor after adopting the modulation block of the present invention is as follows: Figure 11 As shown, it can be seen that the fluctuation is relatively small.

[0117] 5. Suspension force of the suspension motor after adding the traditional modulation block

[0118] The suspension force of the suspension motor after adopting the modulation block of the present invention is as follows: Figure 12 As shown, by comparison, it can be found that the fluctuation of the levitation force of the levitation motor with the modulation of the present invention is significantly lower than that of the levitation force of the levitation motor with the traditional modulation block.

[0119] Through simulation data, it can be found that the modulation block of the present invention can indeed enhance the fundamental wave amplitude, reduce the harmonic amplitude, and reduce the number of harmonics, ultimately making the air gap magnetic field more cosine in the waveform, reducing the harmonic loss of the motor, and improving the performance of the motor, making up for the shortcomings of the traditional modulation block in the modulated bilateral suspension motor.

[0120] The above is only a preferred embodiment of the present invention. This solution can also be used to design the rotor for other bilateral motors with tooth slots. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for constructing a bearingless bilateral motor with low suspension force pulsation, comprising: Preliminarily determine the number of permanent magnet pole pairs and the number of modulation blocks, and modify the magnetic potential of the permanent magnet to be sinusoidal; The Fourier decomposition method is used to determine the fundamental pole pairs of the permanent magnet in rotation and at rest. The suspension winding is wound according to the conditions for the suspension force, and the constraint conditions are set to eliminate the suspension force pulsation caused by the suspension magnetic field fundamental wave and the permanent magnet stationary wave; the permanent magnet magnetic potential modified into a sinusoidal shape is subjected to Fourier decomposition to determine the number of pole pairs generated by the permanent magnet in the motor air gap is p. s The static magnetic field of the permanent magnet is generated by a magnetic field with a pole pair number of n. r After the modulation of the modulation block, the number of pole pairs generated in the air gap is kn r +(2i-1)p s and|kn r -(2i-1)p s | suspension magnetic field, where k=1,2,3,...,i=1,2,3,..., the number of pole pairs is kn r +(2i-1)p s The rotation speed of the magnetic field is The number of pole pairs is |kn r -(2i-1)p s The rotation speed of the magnetic field is Ω r is the mechanical angular velocity of the rotor modulation block; when the number of pole pairs of the suspension magnetic field in the air gap is (n r -p s ) satisfies(n r -p s )=p s -2, the suspension winding is wound into (n r -p s -1) pairs of poles; when the number of pole pairs of the suspended magnetic field in the air gap is (n r -p s ) satisfies(n r -p s )=p s +2, the suspension winding is wound into (n r -p s +1) pairs of poles; when the number of pole pairs of the suspended magnetic field in the air gap is (n r -p s ) does not satisfy (n r -p s )=p s ±2, the suspension winding is wound into (n r -p s -1) opposite pole or (n r -p s +1); for the above p s 、n r The armature magnetic field harmonics and the permanent magnet harmonics before the suspension magnetic field pole pair number is modulated are constrained to cancel each other; s 、n r The armature magnetic field harmonics and the permanent magnet harmonics after the suspension magnetic field pole pair number is modulated are constrained to cancel each other; It is characterized by further comprising: the p determined by the above constraints s 、n r And the number of pole pairs of the suspension magnetic field are further screened, and the screening conditions are: 1-1, 2(|n r -p s |±1) cannot be compared with p s The difference is 1, and 2(|n r -p s |±1) cannot be combined with |2n r ±p s The difference of | is 1; 1-2, 4(|n r -p s |±1) cannot be compared with p s The difference is 1, and 4(|n r -p s |±1) cannot be combined with |n r ±p s The difference between | is 1, and 4(|n r -p s |±1) cannot be combined with |2n r ±p s The difference of | is 1; 1-3, 8(|n r -p s |±1) cannot be compared with p s The difference is 1, and 8(|n r -p s |±1) cannot be combined with |2n r ±p s The difference of | is 1; 1-4, 2(|n r -p s |±1)+n r Cannot be used with |n r ±p s The difference between | is 1, and 2(|n r -p s |±1)+n r Cannot be used with |2n r ±p s The difference of | is 1; 1-5, 2(|n r -p s |±1)-n r Cannot be used with |n r ±p s The difference between | is 1, and 2(|n r -p s |±1)-n r Cannot be used with p s The difference is 1; 1-6, 4(|n r -p s |±1)+n r Cannot be used with |n r ±p s The difference between | is 1, and 4(|n r -p s |±1)+n r Cannot be used with p s The difference is 1; 1-7, 4(|n r -p s |±1)-n r Cannot be used with |n r ±p s The difference between | is 1, and 4(|n r -p s |±1)-n r Cannot be used with |2n r ±p s The difference of | is 1; 1-8, 4(|n r -p s |±1)+n r Cannot be used with |n r ±p s The difference between | is 1, and 4(|n r -p s |±1)+n r Cannot be used with |2n r ±p s The difference of | is 1; 1-9, 2(|n r -p s |±1)-n r Cannot be used with |n r ±p s The difference between | is 1, and 2(|n r -p s |±1)-n r Cannot be used with p s The difference is 1, and 2(|n r -p s |±1)-n r Cannot be used with |2n r ±p s The difference between | is 1.

2. The method for constructing a bearingless bilateral motor with low suspension force pulsation according to claim 1, characterized in that: The bilateral motor adopts a modulation block with a continuous sinusoidal structure, whose outer contour is in the shape of a cosine function, the inner contour is circular, and the middle is filled with magnetic conductive material. The overall shape conforms to the function shape of mcosωθ+B, where m represents the amplitude of the cosine function, B represents the size of the thinnest part of the continuous sinusoidal structure, ω represents the period of the cosine function, and θ represents the angle of the air gap radius distribution.

3. The method for constructing a bearingless bilateral motor with low suspension force pulsation according to claim 2, characterized in that: The method for solving the parameters of the cosine function comprises the following steps: Step 1: According to the number of modulation blocks n r , determine the value of the period ω of the cosine function; Step 2: Use the Fourier decomposition method to obtain the Fourier expression of the air gap magnetic flux density; Step 3: Select the residual parameters m and B of the cosine function based on the Fourier expression of the air gap magnetic flux, the mechanical strength requirements, and the actual air gap size requirements.

4. The method for constructing a bearingless bilateral motor with low suspension force pulsation according to claim 3, characterized in that: The period of the cosine function is We get ω = n r .

5. The method for constructing a bearingless bilateral motor with low suspension force pulsation according to claim 1, characterized in that: After screening and determining the number of suspended pole pairs W, the number of external stator slots is designed to be 2*3*W, so that the suspended winding is 3-phase and the winding form is centralized winding.

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