Variable magnetic pole domain alternating permanent magnet wheel hub motor and design and copper loss optimal control method

Abstract

The application discloses a variable magnetic pole area alternating permanent magnet wheel hub motor and a design and copper consumption optimal control method, adopts alternating variable magnetic pole area units and non-variable magnetic pole area units, each variable magnetic pole area unit includes four permanent magnets, a first permanent magnet, a third magnetic barrier and a third permanent magnet are sequentially connected into a U-shaped structure with an opening facing outward and symmetrical to a q axis; the tangential direction outside of the U-shaped structure is a second permanent magnet and a fourth permanent magnet; the non-variable magnetic pole area unit includes a fifth permanent magnet and a sixth permanent magnet which are arranged in a V-shaped symmetry relative to the q axis, the actual minimum permanent magnet air gap magnetic flux value and the actual maximum permanent magnet air gap magnetic flux value under rated load are compared with maximum and minimum ideal values respectively, and the permanent magnet length and width are optimal values when the requirements are met; the torque current size is adjusted by changing the magnetic regulation coefficient, so that the q-axis current reference value is equal to the real-time q-axis current, and the motor copper consumption is minimum; the output torque of the motor is ensured, and the speed regulation range of the motor is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electric machines, electric vehicles and electric tractors, and relates to a permanent magnet wheel hub motor, in particular, a variable magnetic pole domain alternating permanent magnet wheel hub motor. BACKGROUND

[0002] The wheel hub motor integrates power output, transmission device and brake device in the tire. Compared with the traditional centralized drive type electric machine, the vehicle equipped with the wheel hub motor has no transmission system and auxiliary system parts such as clutch and transmission, and the chassis structure is simple and the transmission efficiency is high. According to the driving mode, the current wheel hub motor can be divided into two categories: reduction drive and direct drive. The reduction drive is to place a reduction mechanism between the motor and the wheel, and to achieve the purpose of speed reduction and torque increase through the reduction mechanism. Since the gear transmission structure is added, the gear will be worn out at high speed, reducing the service life of the motor. In addition, the heat dissipation condition of this type of motor is relatively poor. The direct drive mode has the advantages of simple structure, small axial size and high transmission efficiency since no intermediate link is set. At present, for the wheel hub motor for vehicles, the wheel hub motor plus reducer is usually used in the technical scheme to realize single-wheel high-torque output, for example, a first-stage reducer with a reduction ratio of 2 is used, and the motor is designed at high speed to achieve peak torque through multi-stage reduction; for another example, a wheel hub motor unit is equipped with a two-stage mechanical reducer, and two motors are connected in series and two-stage planetary gear mechanisms are used to output torque to a single wheel. These multi-stage reduction devices improve the torque density of the wheel hub motor, but objectively reduce the expansion range of the motor, and the design of multi-stage mechanical planetary gears is difficult, which is not conducive to the lightweight design of the vehicle. As can be seen, the bottleneck technology of the wheel hub motor is to have high peak torque and wide speed regulation range, that is, the motor needs to have high speed and large torque. Especially for electric tractors, when the electric tractor works in the field, it is easy to be affected by mud immersion, soil and stone embedding and other operating conditions. Therefore, the permanent magnet wheel hub motor needs to have the characteristics of low speed and large torque to adapt to the complex field work requirements; at the same time, when the electric tractor changes the field, the permanent magnet wheel hub motor should have a wide speed regulation range.

[0003] The document with Chinese patent application number 201810024859.4 proposes a high-efficiency permanent magnet wheel hub motor inner stator-rotor-outer stator structure, which can adapt to different operating conditions of the wheel hub motor by controlling the on-off of the stator current to realize the switching of different modes of the rotor. Although this motor can realize the requirements of low-speed large torque and high-speed characteristics, the motor is relatively complex, and the structure of the two-layer stator and the intermediate rotor makes the motor have two-layer air gap, which reduces the torque density and the utilization rate of the permanent magnet of the motor. The document with Chinese patent application number 201310135075.6 proposes an embedded low-speed large torque permanent magnet wheel hub motor, which can realize a substantial increase in torque output capacity at low speed by adding variable permanent magnets. However, this type of motor can only operate in the low-speed range, and the speed regulation range is limited. In general, for the permanent magnet wheel hub motors proposed at present, although they can partially realize the characteristics of low-speed large torque and wide speed regulation range, they still face many problems such as increased complexity of the motor, decreased torque density, and low utilization rate of permanent magnets. At present, there is still a lack of an effective permanent magnet wheel hub motor that can meet the multiple operating characteristics of low-speed large torque and high-speed wide speed regulation range. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, provide a variable magnetic pole domain alternating permanent magnet wheel hub motor and a design method for the main structural parameters of the motor, improve the flux-weakening capability of the high-speed permanent magnet wheel hub motor, increase the effective flux at low speed, ensure the output torque of the motor, and improve the speed regulation range of the motor.

[0005] The present application also provides a targeted copper loss optimal decoupling control method for the motor, which takes into account the change in the optimal phase angle of the current caused by the variable flux in the low-speed range, and realizes the minimum copper loss control under different load conditions.

[0006] To achieve the above object, the technical scheme of the variable magnetic pole area alternating permanent magnet wheel hub motor of the application is that the rotor is located outside the stator, the rotor is provided with the same number of variable magnetic pole area units and non-variable magnetic pole area units arranged in a staggered manner along the circumferential direction, each variable magnetic pole area unit includes four permanent magnets, the outer end of each of the four permanent magnets is provided with a magnetic separation dam, the first permanent magnet, the third magnetic separation dam and the third permanent magnet are sequentially connected into a U-shaped structure with an opening facing outward and symmetrical to the q-axis; an elliptical magnetic induction dam symmetrical to the q-axis is arranged in the middle of the U-shaped structure; the tangential direction outside of the U-shaped structure is the second and fourth permanent magnets arranged in a figure-eight shape with the bottom facing outward and symmetrical to the q-axis; the first and second permanent magnets are on one side of the q-axis, and the third and fourth permanent magnets are on the other side of the q-axis; the non-variable magnetic pole area unit includes the fifth and sixth permanent magnets arranged in a V shape symmetrical to the q-axis with the V-shaped opening facing outward, the inner and outer ends of the fifth and sixth permanent magnets are each provided with a magnetic separation dam, and the two magnetic separation dams at the inner end do not contact; the radial section of all the permanent magnets is a rectangle, the length direction of the rectangle is obliquely along the inner and outer directions; the magnetization direction of all the permanent magnets is along the width direction of the permanent magnet, the magnetization direction of the first, second and sixth permanent magnets is obliquely away from the q-axis, the magnetization direction of the third, fourth and fifth permanent magnets is obliquely directed to the q-axis, the magnetization directions of the four permanent magnets in the two adjacent variable magnetic pole area units are consistent, and the magnetization directions of the permanent magnets in the two adjacent non-variable magnetic pole area units are consistent.

[0007] The technical scheme of the design method of the variable magnetic pole area alternating permanent magnet wheel hub motor of the application is that:

[0008] Step 1): according to the parameters and working condition requirements of the motor, the maximum and minimum ideal permanent magnet air gap magnetic flux values Φ max , Φ min are determined;

[0009] Step 2): according to the formula h x3 l x3 = Φ min R pmb , the product of the length h x3 and the width l x3 of the fifth and sixth permanent magnets is obtained, R pmb is the permanent magnet reluctance of the non-variable magnetic pole area unit; the initial width of l x3 is determined in the range of (0, 5mm), and the initial length of h x3 is obtained;

[0010] Step 3): according to the formula , the product of the length h x1 and the width l x1 of the first and third permanent magnets, and the product of the length h x2 and the width l x2 of the second and fourth permanent magnets are obtained, Fpma Permanent magnet magnetic potential of the variable magnetic pole area unit; l is determined in the range of (0, 5mm) x1 , l x2 The initial width of the permanent magnet magnetic potential of the variable magnetic pole area unit is h x1 , h x2 The initial length of the permanent magnet magnetic potential of the variable magnetic pole area unit is h

[0011] Step 4): Simulate to obtain the actual minimum permanent magnet air gap magnetic flux value Φ' min and the actual maximum permanent magnet air gap magnetic flux value Φ' max under rated load, and make corresponding comparisons with Φ min , Φ max respectively, if Φ' max is greater than Φ max and Φ' min is less than or equal to Φ min , then the length h x1 , h x2 , h x3 and the width l x1 , l x2 , l x3 satisfy the optimal value required; otherwise, repeat steps 2)-step 4), re-determine the values of width l x3 and l x1 , l x2 , to obtain the corresponding length h x3 , h x1 , h x2 , until the design requirements are met.

[0012] The copper loss optimal control method of the variable magnetic pole area alternating permanent magnet wheel hub motor of the application adopts the technical scheme of:

[0013] Step (1): According to the real-time dq axis current, voltage and angular velocity ω of the motor, the real-time permanent magnet flux linkage ψ δ is obtained through parameter identification;

[0014] Step (2): According to the real-time permanent magnet flux linkage ψ δ , the equivalent leakage magnetic current component i k under load and the equivalent leakage magnetic current component i0 under no load of the motor are calculated, and the magnetic regulating current vector i qc is obtained as i k -i0;

[0015] Step (3): When the load size of the motor is different, based on the magnetic regulating current vector i qc , the value of the magnetic regulating coefficient M is changed to adjust the size of the torque current , so that the q-axis current reference value is equal to the real-time q-axis current i q , and the optimal q-axis current reference value iq * the minimum copper loss of the motor; ψ0 is the no-load permanent magnet flux linkage value, P is the pole pair number of the motor rotor, q0 * the q-axis inductance when no load, d * the d-axis inductance when load.

[0016] After the technical scheme is adopted, the present application has the following beneficial effects compared with the prior art:

[0017] 1. On the basis of the traditional V-shaped built-in outer rotor permanent magnet wheel hub motor, the present application adopts alternately arranged variable magnetic pole domain units and non-variable magnetic pole domain units, which are simple in structure and high in reliability. The variable magnetic pole domain units improve the field weakening capability of the traditional permanent magnet wheel hub motor, reduce the required field weakening current of the traditional permanent magnet wheel hub motor at high speed, and thus reduce the irreversible demagnetization risk of the motor. The non-variable magnetic pole domain units ensure the torque output capability of the permanent magnet wheel hub motor and improve the load carrying capacity in the low speed region.

[0018] 2. Due to the integer slot winding and built-in uneven rotor magnetic field distribution of the traditional motor, the torque ripple of the outer rotor leakage magnetic field controllable permanent magnet wheel hub motor is large. The present application adopts a U-shaped rotor slot design on the rotor, changes the rotor magnetic permeability distribution, and improves the rotor unit period number, thereby effectively reducing the cogging torque and torque ripple of the motor.

[0019] 3. Four variable flux branches are arranged in the variable magnetic pole domain units, corresponding to multiple operating points of the motor. When the size of the armature current of the permanent magnet wheel hub motor is changed, the armature flux can be coupled with the leakage flux in different variable flux branches, thereby indirectly changing the size of the effective air gap flux of the motor, so that the permanent magnet wheel hub motor can adapt to the load condition changes of light load, medium load and heavy load.

[0020] 4. The present application can especially adapt to various operating conditions of electric tractor field operation and field transfer. At low speed, the motor presents a P-pole magnetic pole characteristic, which can improve the torque density of the motor and thus improve the torque output capability at low speed. At high speed, the motor presents a P / 2-pole magnetic pole characteristic, which can reduce the induced electromotive force at high speed and thus is conducive to improving the speed regulation range of the motor.

[0021] 5. The present application proposes a copper loss optimal decoupling control method. For the variable flux characteristic of the variable magnetic pole domain units and the constant permanent magnet magnetic field of the non-variable magnetic pole domain units of the motor, the method further decouples the cross-axis current on the basis of the traditional permanent magnet wheel hub motor cross-axis current decoupling control, decomposes the cross-axis current into a cross-axis flux regulating current and a cross-axis torque current, constructs a new torque equation of the motor, introduces a flux regulating coefficient, and realizes the minimum copper loss control of the motor by changing the flux regulating coefficient, thereby further reducing the copper loss of the motor at low speed. The control method provides a new idea and scheme for solving the control of the armature current coupled permanent magnet wheel hub motor. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The radial structure diagram of the variable magnetic pole area alternate permanent magnet wheel hub motor of the present application;

[0023] Wherein: 1. rotor; 2. stator; 2-1. armature tooth; 2-2. stator yoke; 3. stator winding; 4. variable magnetic pole area unit; 5. non-variable magnetic pole area unit; 6. air gap; 7. U-shaped slot; the arrow direction is the magnetizing direction of the permanent magnet;

[0024] Figure 2 The structure enlarged view of a single variable magnetic pole area unit 4 in the present application; Figure 1

[0025] Figure 3 The dimension parameter marked diagram of the present application; Figure 2

[0026] Wherein: 4-1. first magnetic barrier, 4-2. second magnetic barrier, 4-3. third magnetic barrier, 4-4. magnetic induction barrier, 4-5. first permanent magnet, 4-6. second permanent magnet, 4-7. third permanent magnet, 4-8. fourth permanent magnet, 4-9. magnetic leakage area.

[0027] Figure 4 The structure enlarged view of a single non-variable magnetic pole area unit 5 in the present application; Figure 1

[0028] Figure 5 The dimension parameter marked diagram of the present application; Figure 4

[0029] Wherein: 5-1. fourth magnetic barrier, 5-2. fifth magnetic barrier, 5-3. fifth permanent magnet, 5-4. sixth permanent magnet.

[0030] Figure 6 The four variable magnetic leakage paths schematic diagram of the variable magnetic pole area unit 4 in the present application when no load; Figure 1

[0031] The four effective magnetic flux paths schematic diagram of the variable magnetic pole area unit 4 in the present application when load; Figure 7 Figure 1 The magnetic circuit model schematic diagram of the non-variable magnetic pole area unit 5 in the present application when no load;

[0032] Figure 8 Figure 1 The magnetic circuit model schematic diagram of the non-variable magnetic pole area unit 5 in the present application when load;

[0033] Figure 9 The magnetic circuit model schematic diagram of the non-variable magnetic pole area unit 5 in the present application when load; Figure 1

[0034] Figure 10 The magnetic circuit model schematic diagram of the non-variable magnetic pole area unit 5 in the present application when load;​​​​​​​Figure 1 Schematic diagram of the magnetic circuit model of variable magnetic pole domain unit 4 under no-load conditions;

[0035] Figure 11 for Figure 1 Schematic diagram of the magnetic circuit model of the variable magnetic pole domain unit 4 under load;

[0036] Figure 12 The torque distribution curves of the motor of the present invention under different quadrature-axis currents are shown.

[0037] Figure 13 The graph shows the variation of the d-axis air gap flux under different quadrature-axis currents applied to the motor of the present invention.

[0038] Figure 14 The quadrature-axis and direct-axis inductance L of the motor of the present invention under different quadrature-axis currents q L d Change diagram;

[0039] Figure 15 This is a torque distribution diagram of the motor of the present invention under different currents and current angles.

[0040] Figure 16 This is a speed-torque curve diagram of the present invention;

[0041] Figure 17 The control system block diagram for realizing the optimal control method of motor copper loss of the present invention;

[0042] Figure 18 This is a flowchart of the optimal control method for motor copper loss according to the present invention;

[0043] Figure 19 This is the dq-axis vector decomposition diagram in the optimal control method for motor copper loss. Detailed Implementation

[0044] like Figure 1 The variable magnetic pole alternating permanent magnet hub motor of the present invention includes a stator 2 and a rotor 1, wherein the rotor 1 is located outside the stator 2, and an air gap 6 is provided between the stator 2 and the rotor 1. The rotor 1 is fixed to the outer casing. The stator 2 consists of a stator yoke 2-2 and m armature teeth 2-1. The stator winding 3 is wound on the armature teeth 2-1 and is a distributed integer slot winding. The rotor 1 has the same number of n variable magnetic pole unit 4 and n non-variable magnetic pole unit 5. The n variable magnetic pole unit 4 and n non-variable magnetic pole unit 5 are arranged alternately in the circumferential direction, that is, there is a non-variable magnetic pole unit 5 between every two variable magnetic pole unit 4 and a variable magnetic pole unit 4 between every two non-variable magnetic pole unit 5. Therefore, the number of rotor poles is n. Several U-shaped slots 7 are provided in the circumferential direction on the inner surface of the rotor 1. The U-shaped opening of the U-shaped slot 7 faces the air gap side, that is, the inner side.

[0045] The pole-slot matching of the variable magnetic pole region alternating permanent magnet wheel hub motor must be the integer slot winding arrangement, that is, the stator slot number m is an integer multiple of the rotor pole number n, and the rotor pole number n needs to be a positive even number, as shown in formula (1):

[0046] m = 2kn (m, n ∈ N + ) (1)

[0047] In the formula, k is a positive natural number, and the pole-slot matching is 36 / 6, 48 / 8, 96 / 16, etc., which are alternative pole-slot matching schemes of the present application.

[0048] The inner side surface of each variable magnetic pole region unit 4 is provided with 2 U-shaped grooves 7, and the rotor 1 has a total of 2n U-shaped grooves 7.

[0049] As shown in Figure 2 and Figure 3 , each variable magnetic pole region unit 4 is symmetrically arranged relative to the q-axis and consists of four permanent magnets, four magnetic barriers and a magnetic barrier 4-4, wherein the four permanent magnets are a first permanent magnet 4-5, a second permanent magnet 4-6, a third permanent magnet 4-7 and a fourth permanent magnet 4-8. The first permanent magnet 4-5, the third magnetic barrier 4-3 and the third permanent magnet 4-7 are sequentially connected into a U-shaped structure, the opening of the U-shaped structure faces outward, the U-shaped structure is symmetric relative to the q-axis, the first permanent magnet 4-5 and the third permanent magnet 4-7 have the same structure and are two side walls of the U-shaped structure, and the third magnetic barrier 4-3 is the bottom wall of the U-shaped structure. The third magnetic barrier 4-3 is perpendicular to the q-axis, and the first permanent magnet 4-5 and the third permanent magnet 4-7 each form an angle with the q-axis, the angle being β1, and satisfying 0<β1<90deg. Inside the U-shaped structure region is the magnetic barrier 4-4, which is symmetric relative to the q-axis, and the radial cross section of the magnetic barrier 4-4 is elliptical, with the major axis of the ellipse perpendicular to the q-axis and the minor axis of the ellipse coinciding with the q-axis.

[0050] Outside the tangential direction of the U-shaped structure is the second permanent magnet 4-6 and the fourth permanent magnet 4-8, which are symmetric relative to the q-axis and arranged in an eight-character shape, with the opening of the eight-character shape facing outward. The second permanent magnet 4-6 and the fourth permanent magnet 4-8 do not contact at the top of the eight-character shape and each form an angle with the q-axis, the angle being β2, and satisfying 0<β2<90deg, and β2>β1. The second permanent magnet 4-6 and the first permanent magnet 4-5 are on the same side of the q-axis, and the fourth permanent magnet 4-8 and the third permanent magnet 4-7 are on the other side of the q-axis.

[0051] A first magnetic flux barrier 4-1 is provided at the outer ends of the first permanent magnet 4-5 and the third permanent magnet 4-7 respectively, and a second magnetic flux barrier 4-2 is provided at the outer ends of the second permanent magnet 4-6 and the fourth permanent magnet 4-8 respectively. Therefore, there are a total of four magnetic flux barriers. The two first magnetic flux barriers 4-1 have the same structure and are symmetric about the q-axis. The two second magnetic flux barriers 4-2 have the same structure and are symmetric about the q-axis.

[0052] The region enclosed by the extension line of the inner end of the fourth permanent magnet 4-8, the extension line of the inner end of the second permanent magnet 4-6, the inner side surface of the third magnetic flux barrier 4-3, the connection lines between the two ends of the inner side surface of the third magnetic flux barrier 4-3 and the inner ends of the second permanent magnet 4-6 and the fourth permanent magnet 4-8, and the inner wall of the rotor 1 is regarded as the magnetic leakage region 4-9.

[0053] As Figure 3 , the radial thickness of the rotor 1 is r. The radial cross-sections of the first permanent magnet 4-5 and the third permanent magnet 4-7 are both rectangular, and the length direction of the rectangle is along the inner and outer oblique directions. The length needs to satisfy 0 < h x1 < 0.8r, and the width is l x1 .

[0054] The radial cross-sections of the second permanent magnet 4-6 and the fourth permanent magnet 4-8 are both rectangular, and the length direction of the rectangle is along the inner and outer oblique directions. The length h x2 needs to satisfy 0 < h x2 < 0.8r, and the width is l x2 , and 0 < l x1 ≤ l x2 , h x1 < h x2 , and the length and width are respectively greater than or equal to the length and width of the first permanent magnet 4-5 and the third permanent magnet 4-7.

[0055] The distance from the outer end of the magnetic flux guiding barrier 4-4 to the outer side surface of the rotor 1 and the distance from the inner end of the magnetic flux guiding barrier 4-4 to the third magnetic flux barrier 4-4 both need to be greater than 0.05r.

[0056] The two U-shaped grooves 7 on the inner side surface of each variable magnetic pole domain unit 4 are symmetrically distributed about the q-axis. The width j of the U-shaped groove 7 in the tangential direction needs to satisfy 0 < j < 0.1r. The pole arc width β n of the U-shaped groove 7 and the pole arc width β m of the inner surface of the rotor 1 should satisfy the relationship 0 < β n < β m .

[0057] As Figure 4 and Figure 5As shown, the non-variable magnetic pole domain unit 5 consists of two permanent magnets and four magnetic barriers. The two permanent magnets are the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4. The fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 have the same structure and are arranged symmetrically in a figure-eight shape with respect to the q-axis, with the bottom of the figure-eight shape facing outward. The fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 form an angle with the q-axis, and the angle is β3, which satisfies 0 < β3 < 90°.

[0058] Each of the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 has a fourth magnetic barrier 5-1 at its outer end and a fifth magnetic barrier 5-2 at its inner end. The two fifth magnetic barriers 5-2 at the inner ends have identical structures and do not contact each other, and are symmetrical about the q-axis. The two fourth magnetic barriers 5-1 have identical structures and are symmetrical about the q-axis.

[0059] The radial cross-sections of the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 are rectangular, with the length of the rectangles running obliquely inwards and outwards, and the length being h. x3 h x3 Requires 0 <h x3 <0.9r, width is l x3 .

[0060] The radial width of the magnetic bridge between the two fifth magnetic barriers 5-2 and the inner side of rotor 1 is l. x4 Width l x4 Should satisfy 0 <l x4 <0.1r.

[0061] The angle between the q-axis of the adjacent variable magnetic pole unit, the q-axis of the non-variable magnetic pole unit, and the center of the rotor 1 is 180°.

[0062] like Figure 1 As shown, the magnetization direction of the four permanent magnets in each variable magnetic pole domain unit 4 is along the width direction of the permanent magnet, and the magnetization direction of the two permanent magnets on the same side of the q-axis is the same. The magnetization direction of the first permanent magnet 4-5 and the second permanent magnet 4-6 is obliquely away from the q-axis along the width direction of the permanent magnet, while the magnetization direction of the third permanent magnet 4-7 and the fourth permanent magnet 4-8 is obliquely towards the q-axis along the width direction of the permanent magnet. The magnetization direction of the four permanent magnets in two adjacent variable magnetic pole domain units 4 is consistent.

[0063] The magnetization directions of the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 are both along the width direction of the permanent magnet, one obliquely away from the q-axis and the other obliquely towards the q-axis. The fifth permanent magnet 5-3, closest to the fourth permanent magnet 4-8 in the variable magnetic pole domain unit 4, is magnetized obliquely towards the q-axis. The sixth permanent magnet 5-4, closest to the second permanent magnet 4-6 in the variable magnetic pole domain unit 4, is magnetized obliquely away from the q-axis. The permanent magnets in adjacent non-variable magnetic pole domain units 5 have the same magnetization direction.

[0064] The stator 2 and rotor 1 are made of silicon steel sheet material, and the first permanent magnet 4-5, the second permanent magnet 4-6, the third permanent magnet 4-7, the fourth permanent magnet 4-8, the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4 are all made of neodymium iron boron material.

[0065] like Figure 6 The variable magnetic pole domain unit 4 shown has four variable leakage magnetic paths under no-load conditions. Two of these are autonomous leakage magnetic paths A1 and A2, and two are inter-pole leakage magnetic paths A3 and A4. Autonomous leakage magnetic path A1 starts from the inner end of the fourth permanent magnet 4-8, passes through leakage magnetic domain 4-9, and returns to the fourth permanent magnet 4-8. Autonomous leakage magnetic path A2 starts from the inner end of the second permanent magnet 4-6, passes through leakage magnetic domain 4-9, and returns to the second permanent magnet 4-6. Inter-pole leakage magnetic path A3 starts from the inner end of the first permanent magnet 4-5, passes through the inner end of the third permanent magnet 4-7, then passes through leakage magnetic domain 4-9, and returns to the first permanent magnet 4-5. The variable leakage magnetic path between poles includes path A4, which starts from the outer end of the second permanent magnet 4-6, passes through the outer end of the first permanent magnet 4-5, then through the outer end of the third permanent magnet 4-7 and the outer end of the fourth permanent magnet 4-8, and then passes through the leakage magnetic field 4-9 back to the second permanent magnet 4-6.

[0066] like Figure 7 The variable magnetic pole domain unit 4 shown has four effective magnetic flux paths A5, A6, A7, and A8 under load. Effective magnetic flux path A5 starts from the inner end of the fourth permanent magnet 4-8, passes through the air gap and stator 2, and returns to the fourth permanent magnet 4-8. Effective magnetic flux path A6 starts from the inner end of the second permanent magnet 4-6, passes through the air gap and stator 2, and returns to the second permanent magnet 4-6. Effective magnetic flux path A7 starts from the inner end of the first permanent magnet 4-5, passes through the inner end of the third permanent magnet 4-7, then passes through the air gap and stator 2, and returns to the first permanent magnet 4-5. Effective magnetic flux path A8 starts from the outer end of the second permanent magnet 4-6, passes through the outer ends of the first permanent magnet 4-5, the third permanent magnet 4-7, the fourth permanent magnet 4-8, the air gap, and stator 2, and returns to the second permanent magnet 4-6.

[0067] The key parameters in the variable magnetic pole alternating permanent magnet hub motor of the present invention are the length and width of each permanent magnet in the variable magnetic pole unit 4 and the non-variable magnetic pole unit 5. The design method specifically includes the following steps:

[0068] Step 1: Considering the operating conditions of electric vehicles, including heavy-load hill climbing, frequent start-stop, and high-speed cruising, determine the maximum motor speed requirement and maximum torque output capability requirement, thus obtaining the maximum speed as ω. max The maximum torque is T. Based on the motor parameters: q-axis rated current i... q1 Number of motor turns N, bus voltage U dc The maximum ideal permanent magnet air gap flux value Φ of the motor was determined.max The minimum ideal permanent magnetic air-gap magnetic flux value Φ min :

[0069]

[0070]

[0071] Wherein: P is the number of motor rotor pole pairs.

[0072] Step 2: Establish Figure 8 The non-variable magnetic pole domain unit 5 no-load magnetic circuit model and Figure 9 The non-variable magnetic pole domain unit 5 load magnetic circuit model, including air gap reluctance R g , permanent magnet reluctance R pmb , permanent magnetic flux Φ pmb and armature magnetic potential F s , since the non-variable magnetic pole domain unit 5 permanent magnetic flux Φ pmb is all effective flux, when the motor is running at no load, the non-variable magnetic pole domain unit 5 permanent magnetic flux Φ pmb is the effective air-gap magnetic flux Φ δb of the motor into the stator 2, that is, the effective air-gap magnetic flux Φ δb of the non-variable magnetic pole domain unit 5 is equal to its permanent magnetic flux Φ pmb .

[0073] Step 3: According to the minimum ideal permanent magnetic air-gap magnetic flux value Φ min and permanent magnet reluctance R pmb , the length h x3 and width l x3 of the permanent magnet in the non-variable magnetic pole domain unit 5, that is, the fifth permanent magnet 5-3 and the sixth permanent magnet 5-4, are calculated. Multiplying Φ min and R pmb equals the product of h x3 and l x3 . The minimum ideal permanent magnetic air-gap magnetic flux value Φ min and the length h x3 and width l x3 of the permanent magnet of the non-variable magnetic pole domain unit 5 can be expressed as follows:

[0074] h x3 l x3 = F pmb = Φ min R pmb (4)

[0075] Wherein, F pmb is the permanent magnetic potential of the non-variable magnetic pole domain unit 5.

[0076] According to the design experience, the permanent magnet width lx3 The width range is (0, 5mm). Within the width range (0, 5mm), the initial width value of the permanent magnet is determined first. Then, according to formula (4), the initial length value of the permanent magnet can be determined.

[0077] Step 4: When the motor is under load, the effective air gap magnetic flux of the variable magnetic pole domain unit 4 is not zero. The variable magnetic pole domain unit 4 and the non-variable magnetic pole domain unit 5 jointly excite the motor. These two units together construct the effective magnetic flux of the variable magnetic pole domain alternating permanent magnet hub motor. Establishment Figure 10 The magnetic circuit model of the variable magnetic pole domain unit 4 under no-load conditions is shown. Figure 11 The magnetic circuit model shown is for variable magnetic pole domain unit 4 under load, including air gap reluctance R. g Armature magnetomotive force F s The permanent magnet reluctance R of the variable magnetic pole domain unit 4 pma The permanent magnet flux Φ of the variable magnetic pole domain unit 4 pma The magnetic reluctance R of the autonomous leakage flux path A1 b1 The magnetic reluctance R of the autonomous leakage flux path A2 b2 The magnetic reluctance R of the variable leakage path A3 between poles b3 The magnetic reluctance R of the variable leakage path A4 between poles b4 And the leakage flux magnitudes corresponding to the four paths are Φ σ1 =k1i q Φ σ2 =k2i q Φ σ3 =k3i q Φ σ4 =k4i q Where k1, k2, k3, and k4 are the leakage flux coefficients for the four corresponding paths, reflecting the magnitude of the leakage flux and the q-axis current i. q The changing relationship.

[0078] Under no-load conditions, the effective air gap magnetic flux Φ of the variable magnetic pole domain unit 4 δa The permanent magnet flux Φ of the variable magnetic pole domain unit 4 is 0. pma The effective air gap flux Φ enters stator 2 through loops formed by paths A1, A2, A3, and A4 respectively. δa =0, such as Figure 6 As shown. Under load, as Figure 7 As shown, when the q-axis current i q Increase the magnetic reluctance R of the leakage flux path b1 R b2 R b3 R b4 Increase the permanent magnet flux Φ of the variable magnetic pole domain unit 4 pma The effective air gap magnetic flux Φ is formed in stator 2. δa, effective air-gap flux Φ δa increased.

[0079] Step 5: considering the change of silicon steel sheet permeability caused by magnetic circuit saturation, estimating the magnetic reluctance of each leakage magnetic flux path after saturation, according to the given maximum ideal permanent magnet air-gap flux value Φ max , the length h x1 of the permanent magnet of the variable magnetic pole region unit 4 is calculated x2 , and the product of the width l x1 , l x2 , that is, the length h x1 of the first permanent magnet 4-5 and the third permanent magnet 4-7 and the width l x1 , the length h x2 of the second permanent magnet 4-6 and the fourth permanent magnet 4-8 and the width l x2 .

[0080] The maximum ideal permanent magnet air-gap flux value Φ max , the minimum ideal permanent magnet air-gap flux value Φ min , and the length h x1 of the permanent magnet of the variable magnetic pole region unit 4 h x2 , the width l x1 , l x2 can be expressed as follows

[0081]

[0082] where F pma is the permanent magnet magnetic potential of the variable magnetic pole region unit 4. The effective flux of the variable magnetic pole region unit 4 under load should be equal to the constant permanent magnet flux of the non-variable magnetic pole region unit 5, so it should satisfy:

[0083] F pmb = F pma (6)

[0084] F pmb is the permanent magnet magnetic potential of the non-variable magnetic pole region unit 5.

[0085] Similarly, according to the permanent magnet width range (0, 5mm), the value of the permanent magnet width l x1 , l x2 is determined in advance, and combined with formula (5), the initial length and width of the permanent magnet can be obtained.

[0086] Step 6: build a simulation model as shown in Figure 1 , the permanent magnet air-gap flux value of the motor under no load is simulated as the actual minimum permanent magnet air-gap flux value Φ min , and the permanent magnet air-gap flux value under rated load is simulated as the actual maximum permanent magnet air-gap flux value Φ maxVerify the permanent magnetic flux value of the variable magnetic pole area unit 4 and the non-variable magnetic pole area unit 5 entering the air gap respectively, compare the actual maximum permanent magnetic air gap flux value Φ max , the actual minimum permanent magnetic air gap flux value Φ min , and the ideal maximum permanent magnetic air gap flux Φ max , the minimum permanent magnetic air gap flux value Φ min respectively:

[0087] If the actual maximum permanent magnetic air gap flux value Φ max is greater than or equal to the ideal maximum permanent magnetic air gap flux Φ max , and the actual minimum permanent magnetic air gap flux value Φ min is less than or equal to the ideal minimum permanent magnetic air gap flux value Φ min , then the permanent magnet length h x3 , width l x3 of the non-variable magnetic pole area unit 5, the permanent magnet h x1 , h x2 , width l x1 , l x2 of the variable magnetic pole area unit 4 meet the design requirements of the ideal air gap flux, which are the optimal parameters. Otherwise, the design requirements are not met, and steps 2 to 6 are repeated, the width value of the permanent magnet width l x3 in the non-variable magnetic pole area unit 5 is determined again in step 3, and the corresponding permanent magnet length is obtained; the width value of the permanent magnet width l x1 , l x2 in the variable magnetic pole area unit 4 is determined again in step 5, and the corresponding permanent magnet length is obtained. Repeat the selection of permanent magnet width and the calculation of permanent magnet length until the design requirements are met, and the optimal permanent magnet length and width are obtained. When the permanent magnet width is selected iteratively, the width is selected in an equal step size manner.

[0088] Referring to Figure 12 , the torque distribution curve of the variable magnetic pole area alternating permanent magnet wheel hub motor of the application under different cross-axis current is shown. The torque constant of the traditional permanent magnet motor is a certain value, and the curve is a straight line, that is, the torque and the current have a linear growth relationship. The torque constant of the motor of the application is a growing nonlinear change value due to the special rotor design, and accordingly, the torque-current relationship of the motor is no longer a straight line. When the current increases, the torque increase is correspondingly increased.

[0089] Referring to Figure 13The graph shows the change in d-axis air gap flux linkage of the variable magnetic pole alternating permanent magnet hub motor of this invention under different quadrature-axis currents. In a traditional permanent magnet motor, due to the constant permanent magnet air gap magnetic field, the curve is a linearly decreasing curve due to the influence of the saturated magnetic field. However, the motor of this invention, by employing the variable magnetic pole unit 4, allows the effective turn flux linkage to change with the quadrature-axis current. When the current reaches the rated value, its flux linkage rise rate is approximately 34.4%, thus enabling the variable magnetic pole alternating permanent magnet hub motor proposed in this invention to have an adjustable magnetic field, adapt to various operating conditions, and have the potential for multi-condition operation.

[0090] See Figure 14 The present invention relates to the variable magnetic pole domain alternating permanent magnet hub motor, which applies different quadrature axis currents to the quadrature and direct axis inductance L. q L d The graph shows the change in the direct-axis inductance L as the magnetic flux saturation level increases. q L d The inductance L decreases under large quadrature-axis currents, but the quadrature-axis inductance L... q The decrease is more pronounced; when the current reaches a certain value, the direct-axis inductance L... q L d The magnitude relationship has changed, from the no-load quadrature axis inductance L q Greater than the direct-axis inductance L d Change to direct-axis inductance L d Greater than the quadrature axis inductance L q The motor exhibits a near-anti-salient pole characteristic, thereby enabling the use of the motor's positive reluctance torque by applying a positive shaft current, thus reducing the risk of irreversible demagnetization of the motor.

[0091] See Figure 15 The torque distribution of the variable magnetic pole alternating permanent magnet hub motor of the present invention under different currents and current angles is shown. It can be seen that the motor torque reaches its maximum value near a current angle of 25 degrees, and the reluctance torque accounts for about 30%. The motor has good torque output capability.

[0092] See Figure 16 The speed-torque curve of the variable magnetic pole domain alternating permanent magnet hub motor of the present invention is shown in the figure. Figure 16 As can be seen, the maximum speed of the motor of this invention can reach 2250 rpm, which is about 5 times the rated base speed, and it has a wide speed range, enabling it to operate within a wide speed range.

[0093] The present invention provides an optimal copper loss control method for a variable magnetic pole domain alternating permanent magnet hub motor, such as... Figure 17As shown, based on the traditional control system, the traditional control system is a current feedback system composed of a photoelectric encoder, a PI controller, a Park converter module, a Carke converter module, an SVPWM module, an inverter module, and a flux linkage estimation module. In this invention, a magnetic flux estimation module and a minimum copper loss allocation module are connected in series between the output of the flux linkage estimation module and the output of the PI controller. The photoelectric encoder detects the rotor angle θ of the variable magnetic pole alternating permanent magnet hub motor of this invention, obtaining the angular velocity ω. The angular velocity ω is input to the current feedback loop, and the difference between this angular velocity and the estimated angular velocity ω* is output as the armature current vector i after passing through the PI controller. s *. The present invention relates to the three identical currents i of a variable magnetic pole alternating permanent magnet hub motor. a i b i c The coordinate transformation of Carke and Park into dq-axis current i d i q , and the dq axis voltage u d u q The motor angular velocity ω is input into the flux linkage estimation module. The flux linkage estimation module uses a model reference adaptive parameter identification method to obtain the real-time permanent magnet flux linkage ψ of the motor. δ Then, the effective air gap flux linkage value ψ of the permanent magnet. δ The magnetizing current vector i is calculated by the magnetizing current calculation module. qc Magnetic current vector i qc and the armature current vector i output by the PI controller s *A common input minimum copper loss allocation module is used to obtain the optimal dq-axis current i. d *、i q *Value. Reference Figure 18 The flowchart shown is as follows:

[0094] In the flux linkage estimation module, the real-time permanent magnet flux linkage ψ is obtained through parameter identification. δ The magnetic flux linkage calculation module calculates the magnetic flux based on the real-time permanent magnet flux linkage ψ. δ First, calculate the equivalent leakage current component i of the motor under load. k And the equivalent leakage current component i0 under no-load conditions:

[0095]

[0096]

[0097] Where ψ0 is the unloaded permanent magnet flux linkage, L d Let be the d-axis inductance of the motor.

[0098] Then, based on the two current components i k The magnetizing current vector i is calculated from i0.qc ,

[0099] i qc =i k -i0 (9)

[0100] Direct-axis current i in the armature winding dq-axis synchronous coordinate system d and cross-axis current i q Based on the formed current plane, for the variable magnetic pole domain unit 4 and the non-variable magnetic pole domain unit 5, see [reference needed]. Figure 19 As shown, the torque current vector i is defined. qt And modulated magnetic current vector i qc Torque current vector i qt A constant magnetic flux acting on the non-variable magnetic pole domain unit 5 generates a constant torque, and the magnetic current vector i is adjusted. qc It acts on the variable magnetic pole domain unit 4, adjusting its effective magnetic flux. Torque current vector i qt And modulated magnetic current vector i qc Synthesize the q-axis current reference value i on the plane q *. Torque current vector i qt , tuning current vector i qc and d-axis current reference value i d The vector sum of * is the ideal armature current vector i. s *. When the q-axis current reference value i q * and the actual cross-axis current vector i q When the phase and magnitude are the same, the actual armature current vector i s With the ideal armature current vector i s *Same. Therefore, the torque equation for the reconfigurable variable magnetic pole alternating permanent magnet hub motor is:

[0101]

[0102] Among them, T e T is the motor torque. e0 T represents the torque increment caused by the non-variable magnetic pole domain unit 5. ec The torque increment caused by the variable magnetic pole domain unit 4, P is the number of rotor pole pairs of the motor, ψ0 is the no-load permanent magnet flux linkage value, Δψ is the change in air gap flux linkage caused by load change, and ΔL is the torque increment caused by the variable magnetic pole domain unit 4. q L represents the change in q-axis inductance caused by load variation. q0 L is the q-axis inductance under no-load conditions. d The d-axis inductance is under load.

[0103] For the torque equation of the motor in equation (10), by introducing the field adjustment coefficient M, a new torque equation is obtained:

[0104]

[0105] To optimize copper loss, a copper loss P of a variable magnetic pole domain alternating permanent magnet hub motor is constructed. Cu equation:

[0106]

[0107] Among them, R s This is the stator resistance value.

[0108] Construct the Lagrangian function for the copper loss equation in equation (12):

[0109]

[0110] Where λ is the Lagrange coefficient.

[0111] Find i for the Lagrange function in equation (13) qt i qc i d Taking the partial derivative of * and setting it to 0, we can solve the simultaneous equations to obtain the d-axis current reference value i. d *, Torque current i qt With the magnetizing current i qc The mathematical relationship between them:

[0112]

[0113] The reference value i of the vector superposition of the q-axis current is calculated using the following formula. q *for:

[0114]

[0115] Actual feedback q-axis current value i q Size:

[0116]

[0117] Where: i s This represents the actual stator current amplitude.

[0118] Actual q-axis current i q With q-axis current reference value i q Whether they are equal is used as a criterion for minimizing copper loss. For example... Figure 18 As shown, under any load condition, by adjusting the value of the magnetic field adjustment coefficient M, the q-axis current reference value i is adjusted. q * and the actual feedback q-axis current i q equal.

[0119] As can be seen from equation (14), when the magnetic field coefficient M is changed, the torque current i can be adjusted. qt , Thus, the adjusted torque current value i qt is calculated according to the formula (15) q : The value of the magnet adjustment coefficient M can be obtained so that the q-axis current reference value i q *is equal to the actual feedback q-axis current i q . At this time, the phase difference between the adjusted torque current i qt and the magnet current i qc is 90°, and the torque current i qt and the magnet current i qc are in quadrature. When the q-axis current i q is not equal to the q-axis current reference value i q *, i.e., the phase difference between the torque current i qt and the magnet current i qc is not 90°, the value of the magnet adjustment coefficient M is adjusted, and the torque current i qt and the q-axis current reference value i q *are recalculated until they are equal.

[0120] When the load of different sizes is given, the value of the magnet adjustment coefficient M needs to be dynamically adjusted, and the size of the q-axis current reference value i q *under the magnet adjustment coefficient M value is compared with the actual q-axis current value i q . When the two values are equal, the optimal i d *and i q *values are obtained, the torque current i qt and the magnet current i qc are completely decoupled, and the amplitude of the combined stator winding current i s *is minimum, and the copper loss of the motor under the torque can be minimized.

[0121] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A variable pole field alternating permanent magnet wheel motor, the rotor is located outside the stator, characterized in that: The rotor is provided with the same number of variable magnetic pole domain units (4) and non-variable magnetic pole domain units (5) arranged alternately along the circumference. Each variable magnetic pole domain unit (4) includes four permanent magnets. Each of the four permanent magnets has a magnetic barrier at its outer end. The first permanent magnet (4-5), the third magnetic barrier (4-3), and the third permanent magnet (4-7) are connected in sequence to form a U-shaped structure with the opening facing outward and symmetrical with respect to the q-axis. An elliptical magnetic barrier (4-4) symmetrical with respect to the q-axis is set in the middle of the U-shaped structure. The second and fourth permanent magnets (4-6, 4-8) are arranged in a figure-eight shape with the bottom facing outward and symmetrical with respect to the q-axis on the outside of the tangential direction of the U-shaped structure. The first and second permanent magnets (4-5, 4-6) are on one side of the q-axis, and the third and fourth permanent magnets (4-7, 4-8) are on the other side of the q-axis. The element (5) includes the fifth and sixth permanent magnets (5-3, 5-4) arranged in a V-shape with the V-shaped opening facing outwards relative to the q-axis. Each of the inner and outer ends of the fifth and sixth permanent magnets (5-3, 5-4) is provided with a magnetic barrier, and the two magnetic barriers at the inner ends do not contact each other. The radial cross-section of all permanent magnets is rectangular, and the length direction of the rectangle is obliquely along the inside and outside. The magnetization direction of all permanent magnets is along the width direction of the permanent magnet. The magnetization direction of the first, second, and sixth permanent magnets (4-5, 4-6, 5-4) is obliquely away from the q-axis. The magnetization direction of the third, fourth, and fifth permanent magnets (4-7, 4-8, 5-3) is obliquely pointing towards the q-axis. The magnetization direction of the four permanent magnets in two adjacent variable magnetic pole domain units (4) is consistent. The magnetization direction of the permanent magnets in two adjacent non-variable magnetic pole domain units (5) is consistent.

2. The variable pole-field alternate permanent magnet wheel motor of claim 1, wherein: The angle β1 between the first and third permanent magnets (4-5, 4-7) and the q-axis satisfies 0 < β1 < 90°; the angle β2 between the second and fourth permanent magnets (4-6, 4-8) and the q-axis satisfies 0 < β2 < 90°, and β2 > β1; the angle β3 between the fifth and sixth permanent magnets (5-3, 5-4) and the q-axis satisfies 0 < β3 < 90°.

3. The variable pole-field alternate permanent magnet wheel motor of claim 1, wherein: Length h of the first and third permanent magnets (4-5, 4-7) x1 0 < h < 0.8r x1 <0.8r, length h of the second and fourth permanent magnets (4-6, 4-8) x2 0 < h < 0.8r x2 <0.8r, and h x1 <h x2 ; width l of the first and third permanent magnets (4-5, 4-7) x1 and width l of the second and fourth permanent magnets (4-6, 4-8) x2 0 < l < 0.8r x1 ≤ l < 0.8r x2 ; length h of the fifth and sixth permanent magnets (5-3, 5-4) x3 0 < h < 0.9r x3 <0.9r, width l x3 r is the radial thickness of the rotor.

4. The variable pole pitch alternate permanent magnet wheel motor of claim 1, wherein: The distance from the outer end of the magnetic barrier (4-4) to the outer side of the rotor and the distance from the inner end of the magnetic barrier (4-4) to the third magnetic barrier (4-4) are both greater than 0.05r, where r is the radial thickness of the rotor.

5. The variable pole pitch alternate permanent magnet wheel motor of claim 1, wherein: On the inner surface of each variable magnetic pole domain unit 4, there are two U-shaped grooves (7) with openings facing inward and symmetrically distributed about the q-axis. The tangential width j of the U-shaped groove (7) satisfies 0 < j < 0.1r, and the pole arc width β of the U-shaped groove (7) n and the pole arc width β of the inner surface of the rotor m satisfy the relationship 0 < β n < β m , where r is the radial thickness of the rotor.

6. The design method of a variable pole pitch alternate permanent magnet wheel motor as claimed in claim 1, characterized in that include: Step 1): Determine the maximum and minimum ideal permanent magnet air gap magnetic flux value Φ of the motor according to the parameters of the motor and the working condition requirements max , Φ min ; Step 2): According to formula h x3 l x3 =Φ min R pmb The lengths h of the fifth and sixth permanent magnets (5-3, 5-4) are obtained. x3 With width l x3 The product of R pmb The permanent magnet reluctance of the non-variable magnetic pole domain unit (5) is determined in the range of (0, 5 mm). x3 The initial width is obtained by h. x3 The initial length; Step 3): according to the formula the length h of the first, third permanent magnets (4-5, 4-7) x1 and the width l x1 , and the length h of the second, fourth permanent magnets (4-6, 4-8) x2 and the width l x2 , F is the permanent magnetic potential of the variable magnetic pole field unit (4); l pma is determined in the range (0, 5 mm) x1 , the initial width of l x2 , the initial length of h x1 , h x2 ; Step 4): simulate to obtain the actual minimum permanent magnet air gap magnetic flux value Φ' of the motor at no load min and the actual maximum permanent magnet air gap magnetic flux value Φ' under rated load max , and make corresponding comparisons with Φ min , Φ max , respectively, if Φ' max is greater than Φ max and Φ' min is less than or equal to Φ min , then the lengths h x1 , h x2 , h x3 and the widths l x1 , l x2 , l x3 meet the required optimal values; otherwise, repeat steps 2) to 4), re-determine the values of widths l x3 and l x1 , l x2 , and obtain the corresponding lengths h x3 , h x1 , h x2 , until the design requirements are met.

7. The method of claim 6, wherein: In step 1), according to the formula and Calculate the maximum and minimum ideal permanent magnet air gap flux Φ respectively. max Φ min T is the maximum torque of the motor, N is the number of turns of the motor, P is the number of rotor pole pairs of the motor, and i q1 U is the q-axis rated current. dc The bus voltage value, ω max This is the maximum speed of the motor.

8. The copper loss optimal control method of the variable pole pitch alternate permanent magnet wheel hub motor of claim 1, characterized in that include: Step (1): According to the real-time dq-axis current, voltage and angular velocity ω of the motor, the real-time permanent magnet flux linkage ψ is obtained through parameter identification δ ; Step (2): The real-time permanent magnet flux linkage ψ δ The equivalent leakage flux current component i k and the equivalent leakage flux current component i0under no load are calculated, and the magnetizing current vector i qc = i k - i0; Step (3): When the motor load size is different, based on the field current vector i qc , change the value of the field coefficient M to adjust the size of the torque current , so that the q-axis current reference value is equal to the real-time q-axis current i q , get the optimal q-axis current reference value i q *, the motor copper loss is minimum; ψ0 is the no-load permanent magnet flux value, P is the number of motor rotor pole pairs, L q0 is the q-axis inductance when no load, L d is the d-axis inductance when loaded.

9. The method of claim 8, wherein: In step (2), the equivalent leakage current component i of the motor under load is calculated from the formula In step (2), the equivalent leakage current component i of the motor under load is calculated from the formula k In step (2), the equivalent leakage current component i of the motor under load is calculated from the formula In step (2), the equivalent leakage current component i of the motor under load is calculated from the formula 10. The method of claim 8, wherein: The d-axis current reference value is calculated according to the magnetic modulation coefficient M

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