A multi-pole and few-slot unitized permanent magnet hub motor and a coordinated control system and method

Abstract

The present invention discloses a multi-pole and few-slot unitized permanent magnet hub motor and a coordinated control system and method. The motor is composed of N identical motor units uniformly distributed in the circumferential direction of a radial section, each 1 / N outer rotor is divided into M identical rotor segments along the axial direction, and the M rotor segments are rotated in sequence along the same rotation direction by a mechanical staggered angle arrangement; the constant torque area is divided into a first area and a second area, and the constant power area is divided into a third area to an eighth area. The control system includes two control modules, each of which is composed of a power electronic switch, a DSP controller and an inverter connected in series in sequence, the input ends of the two power electronic switches are respectively connected to the output ends of a battery, the output end of each inverter is respectively connected to N / 2 winding electronic switches, one winding electronic switch controls the on and off of a centralized winding in a motor unit, and the mutually independent winding electronic switches realize independent control of the motor unit, thereby improving the motor control freedom and operation efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet motors, and in particular refers to a permanent magnet hub motor suitable for electric vehicles, ship propulsion, electric tractors, etc., which require high efficiency and multi-operating conditions. Background Art

[0002] Permanent magnet hub motors have shown potential application prospects in direct drive fields such as electric vehicles, ship propulsion, and electric tractors due to their advantages such as high torque density and high power density. However, the permanent magnet magnetic field is constant and difficult to adjust, and deep magnetic weakening is difficult, resulting in a small speed regulation range and low high-speed efficiency for this type of motor, making it difficult to apply to multi-operating conditions such as electric vehicles.

[0003] The document with Chinese patent number 202210042232.8 proposes a convex-type hybrid excitation motor, which adopts a hybrid excitation method of permanent magnet steel and excitation current. The feature of adjustable excitation current reduces the difficulty of weak magnetic field of motor excitation magnetic field and realizes multi-operation operation of motor; however, the introduction of excitation current increases the copper loss of motor and reduces the operation efficiency of the whole machine. The document with Chinese patent number 201410768272.6 proposes a stator magnetic concentration hybrid permanent magnet memory motor, which adopts the excitation method of soft magnetic material with low coercive force and rare earth permanent magnetic steel. The magnetic potential of soft magnetic material changes with the change of pulsating winding current, and the strength of excitation magnetic field also changes accordingly, thereby reducing the difficulty of weak magnetic field of motor and realizing multi-operation operation of motor; however, the addition of soft magnetic material and pulsating winding increases the volume and weight of motor and reduces the power density of motor. At the same time, the introduction of pulse winding also increases the loss of motor and reduces the operation efficiency of motor.

[0004] Therefore, how to achieve high efficiency in multi-operating conditions is an urgent problem that permanent magnet hub motors need to solve. Summary of the invention

[0005] The purpose of the present invention is to address the problems existing in the multi-operating conditions of existing permanent magnet hub motors, and to propose a multi-slot, few-pole, unitized permanent magnet hub motor and a multi-unit collaborative control system and method for the motor, so as to improve the operating efficiency and expand the high-efficiency operating area of ​​the permanent magnet hub motor under the premise of meeting the requirements of multi-operating conditions.

[0006] The technical solution adopted by the multi-pole and few-slot unitized permanent magnet hub motor of the present invention is: it is composed of N identical motor units uniformly distributed in the circumferential direction of the radial cross section, each motor unit includes 1 / N outer rotors, 1 / N inner stators and 1 / N concentrated windings, the inner stator is coaxially sleeved inside the outer rotor, the inner stator is wound with concentrated windings, and the concentrated windings in each motor unit are three-phase symmetrical and distributed in the same manner; the outer rotor has a rotor core, 2a permanent magnet steel groups are uniformly distributed on the rotor core in the circumferential direction, and each permanent magnet steel group is composed of first and second rectangular permanent magnet steels and The first and second rectangular permanent magnets are composed of arc-shaped permanent magnets, the first and second rectangular permanent magnets have the same structure and the radial cross-sections are both rectangular, the inner and outer oblique directions are the length direction of the rectangle, and they are arranged in a V-shape with the opening facing the air gap side on the outside of the arc-shaped permanent magnet, symmetrical with respect to the center line of the arc-shaped permanent magnet along the diameter direction; the magnetizing directions of the first and second rectangular permanent magnets are perpendicular to their own length directions, the magnetizing direction of the arc-shaped permanent magnet is consistent with the center line direction, the magnetizing directions of the first and second rectangular permanent magnets and the arc-shaped permanent magnets belonging to the same permanent magnet group are simultaneously directed to or away from the air gap, and the magnetizing directions of the two adjacent permanent magnet groups are opposite; the number of rotor pole pairs P r 、Number of stator slots s , the number of motor phases m, the motor slot angle τ and N must all satisfy: P r >N s , P r =Na, N s =mNb, cτ=d*2π、 N=2i, i, a, b, c, d, e are all positive integers.

[0007] Each of the 1 / N outer rotors is divided into M identical rotor segments along the axial direction, and the M rotor segments are arranged in sequence by rotating a mechanical staggered angle along the same rotation direction, 20mm≤l ef / M≤120mm,l ef is the axial length of the motor.

[0008] Furthermore, each arc-shaped permanent magnet steel is surrounded by an arc-shaped permanent magnet steel outer long side, an arc-shaped permanent magnet steel inner long side and two arc-shaped permanent magnet steel short sides in the radial cross section, the arc center of the arc-shaped permanent magnet steel outer long side and the arc-shaped permanent magnet steel inner long side is the same as the center of the outer rotor, the arc-shaped permanent magnet steel short side and the outer rotor have the same diameter direction, and the inner long side of the arc-shaped permanent magnet steel is a sine curve f1(θ1)=f 1max sin(θ1),θ1∈[π,2π],f 1max is the amplitude, when θ1 is 3π / 2, point f1(3π / 2) is located on the inner surface of the outer rotor.

[0009] Furthermore, each of the first and second rectangular permanent magnets is provided with an inner magnetic barrier at the end close to the air gap side and an outer magnetic barrier at the end away from the air gap side, and each arc-shaped permanent magnet is provided with a virtual slot forming part of the air gap at both tangential ends.

[0010] The technical solution adopted by the collaborative control system of the multi-pole and few-slot unitized permanent magnet hub motor described in the present invention is: it includes a battery, two control modules and N winding electronic switches, one winding electronic switch controls the on-off of the centralized winding in a motor unit, each control module is composed of a power electronic switch, a DSP controller and an inverter connected in series in sequence, the input ends of the two power electronic switches are respectively connected to the output ends of the batteries, the output ends of each inverter are respectively connected to N / 2 winding electronic switches, and the output ends of the centralized windings are connected to the batteries via a rectifier.

[0011] The technical solution adopted by the control method of the cooperative control system described in the present invention is:

[0012] Close two power electronic switches and N winding electronic switches, take the horizontal axis as the motor speed and the vertical axis as the motor output torque, and simulate to obtain the motor's external characteristic curve g; then disconnect one of the power electronic switches and simulate to obtain the motor's external characteristic curve f; the highest speed corresponding to the highest torque on the external characteristic curve f is taken as the critical speed n b , when the motor running point speed n p ≤n b , is the constant torque area;

[0013] The constant torque area is divided into the first area and the second area. When the torque T p ≤T b , is the first zone, when T p >T b , for the second zone, T b is the critical torque T b , is a motor unit (1) peak torque T x N-2 times; the maximum value of the torque at the operating point in the second zone does not exceed the torque corresponding to the external characteristic curve g;

[0014] When the operating point is in the first zone, both power electronic switches are closed, and at least one of the N / 2 motor units connected to each control module is closed. Winding electronic switch, T p1 is the torque of the operating point in the first zone; the two inverters output currents of the same amplitude but different phases; when the operating point is in the second zone, the two power electronic switches and the N winding electronic switches are all closed.

[0015] When the motor running speed n p >n b , is the constant power area;

[0016] The constant power area is divided into the third to eighth areas. When the efficiency of the operating point is η p≥ η b , then it is the fourth zone, η b is the boundary efficiency of the motor when a single control module is running; the area surrounded by the abscissa axis, the external characteristic curve g and a straight line j perpendicular to the abscissa passing through the highest speed point E in the fourth zone is the eighth zone; the area where the torque is less than the torque of the lowest speed point D in the fourth zone and the speed is less than the speed of point D is the zone S 31 The area enclosed by the abscissa, a straight line k passing through point D and perpendicular to the abscissa, the fourth zone point D, the lower half boundary line of E, and the straight line j is area S. 32 , S 31 With S 32 The union of is the third zone; the zone with the same speed as the fourth zone and twice the torque of the fourth zone is the sixth zone, the highest speed point G of the sixth zone is on the straight line j, and the lowest speed point F is on the straight line k; the zone with a torque less than the torque at point F, a torque higher than point D, and a speed less than the speed at point F is zone S 51 The area enclosed by straight line k, straight line j, the upper half boundary of the fourth zone point D and E, and the lower half boundary of the sixth zone point F and G is area S. 52 , S 51 With S 52 The union of is the fifth zone; the remaining area in the constant power zone is the seventh zone;

[0017] When the operating point is in the third zone, only one of the two power electronic switches is closed, all N winding electronic switches are closed, and the power-up operation is adopted to increase the torque without changing the motor speed; when the operating point is in the fourth zone, only one of the two power electronic switches is closed, all N winding electronic switches are closed; when the operating point is in the fifth zone, both power electronic switches are closed, all N winding electronic switches are closed and the power-up operation is adopted; when the operating point is in the sixth zone, both power electronic switches are closed, all N winding electronic switches are closed; when the operating point is in the seventh zone, both power electronic switches are closed, all N winding electronic switches are closed, and the currents output by the two inverters are different; when the operating point is in the eighth zone, both power electronic switches are closed, all N winding electronic switches are closed.

[0018] Furthermore, the motor output torque waveform and the transition current output by the two inverters are simulated and calculated when the K windings are electronically switched, the output torque waveform is Fourier decomposed, the harmonic order r of the main harmonic component is obtained, and the current misalignment angle is calculated. The three-phase current amplitude I of the output of the two inverters is max =1.05I max0 , I max0is the transition current amplitude, the three-phase current phase output by the first inverter leads the transition current phase by β / 2, and the three-phase current phase output by the second inverter lags the transition current phase by β / 2.

[0019] Furthermore, the power-up operation of the third zone is: p3 ,T p3 ) Transition point P3'(n p3 ,T p3’ ), when the condition is met When forming a set S P3 , set S P3 The third or fourth zone and the torque is greater than or equal to T P3 The operating point is the power-up operating point H3 (n H3 ,T H3 ), the simulation obtains that the motor runs at the power increase point H3(n H3 ,T H3 ) when the inverter outputs three-phase current, feeding the excess energy back to the battery; the power-up operation in the fifth zone is similar to the power-up operation in the third zone; n p3 、T p3 and η p3 They are respectively the operating point P3(n p3 ,T p3 ) speed, torque and efficiency, T p3’ and η p3’ are the torque and efficiency at the transition point, η pg For power generation efficiency.

[0020] Furthermore, in the seventh zone, there are two transition points with a rotational speed equal to the seventh zone operating point, and the sum of the torques of the two transition points is equal to the seventh zone operating point torque. The sum of the total system power consumption of the two transition points is calculated. When the sum of the total system power consumption of two operating points is equal to the minimum value of the sum of the total system power consumption of the two transition points, the two operating points are respectively controlled and operated by the corresponding two control modules.

[0021] The present invention has the following beneficial effects after adopting the above technical solution:

[0022] 1. The present invention adopts the concept of multi-unit design to design a unitized motor structure. The unitized design without spatial overlap makes all motor units independent of each other. Each motor unit can be operated and controlled independently, which greatly improves the freedom of operation and control of the motor. The different combination forms and working modes of the multiple units enable the permanent magnet hub motor to have the ability to operate in multiple working conditions.

[0023] 2. The present invention adopts a structure with more poles and fewer slots, which solves the high requirements of traditional modular motors on pole-slot ratios, provides a new pole-slot ratio for modular motors, increases the number of rotor pole pairs, and enables the permanent magnet hub motor to obtain the performance characteristics of low speed and high torque, better meeting the performance requirements of the hub motor.

[0024] 3. The rotor in the present invention adopts a segmented oblique pole structure in the axial direction, which is beneficial to adjust the rotor torque harmonic phase distribution, realize the mutual compensation of the first segment rotor torque harmonic phase and the second segment rotor torque harmonic phase, eliminate the highest amplitude harmonic of the output torque, thereby greatly reducing the motor torque pulsation and improving the torque quality.

[0025] 4. The arc-shaped permanent magnet steel in the present invention adopts a sinusoidal curve design on the long side close to the air gap, which is beneficial to adjusting the salient pole ratio of the motor and improving the weak magnetic field capability of the motor on the one hand; on the other hand, it improves the sinusoidality of the permanent magnet magnetic potential and reduces the harmonic complexity of the permanent magnet magnetic field, which is beneficial to reducing the motor core loss, while improving the motor operating efficiency. Reduce the motor torque pulsation and improve the overall quality of the motor output performance.

[0026] 5. The rectangular permanent magnet steel in the present invention is provided with a leakage magnetic circuit near the air gap end, so that as the q-axis current changes, the permanent magnetic field of the motor can achieve "more leakage magnetic field under light load and no leakage magnetic field under heavy load", that is, when the motor is overloaded, the permanent magnetic flux is all effective magnetic flux, which is beneficial to improving the torque output capacity of the motor and realizing the operation of the motor under heavy load conditions; when the motor is at high speed, the q-axis current is reduced and the permanent magnetic field is weakened, which is beneficial to widening the motor speed range and realizing high-speed operation of the motor.

[0027] 6. The multi-unit collaborative control system proposed in the present invention uses independent winding electronic switches to realize independent control of the motor units, thereby increasing the freedom of motor control and improving the motor fault tolerance; the independent power supply electronic switches decouple the two control modules of the motor, thereby increasing the freedom of motor control, providing a hardware foundation for achieving high-performance operation of the motor and improving the operating reliability of the motor in the light-load area.

[0028] 7. The present invention proposes that when the motor operates in the first zone of low-speed load, the two inverters output currents of the same frequency, the same amplitude and different phases, and the motor units of the two modules operate at the same operating point. At this time, the main harmonic phase difference of the output torque corresponding to the two controllers is 180°, and the two compensate each other, thereby reducing the motor torque pulsation.

[0029] 8. The present invention proposes that when the motor operates in the third zone of high speed and low load, only one of the first power electronic switch and the second power electronic switch is closed and all the winding electronic switches are closed at the same time, and the corresponding controlled motor unit operates at increased power. At this time, the motor operating efficiency is improved, and the excess energy is fed back to the battery through the rectifier, which is beneficial to improving the efficiency of the motor system.

[0030] 9. The present invention proposes that when the motor operates in the fifth zone high-speed load zone, all power electronic switches are closed and all winding electronic switches are closed at the same time, and the motor unit operates at increased power. At this time, the motor operating efficiency is improved, and excess energy is fed back to the battery through the rectifier, which is beneficial to improving the efficiency of the motor and the control system.

[0031] 10. The present invention proposes that when the motor operates in the seventh zone high-speed overload zone, all power electronic switches are closed and all winding electronic switches are closed at the same time, the unit motors of the two modules operate at different operating points, the output torques are algebraically superimposed, and the losses are also algebraically superimposed. In the collaborative working mode, since all motor units operate in the high-efficiency zone, the total motor loss is reduced, thereby improving the motor operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The radial structure and unitized decomposition schematic diagram of the unitized permanent magnet hub motor with more poles and fewer slots of the present invention;

[0033] Figure 2 for Figure 1 An enlarged structural diagram of a motor unit 1;

[0034] Figure 3 It is a schematic diagram of the axial installation structure of two-section rotors of the unitized permanent magnet hub motor with more poles and fewer slots of the present invention;

[0035] Figure 4 for Figure 3 Radial view in ;

[0036] Figure 5 for Figure 4 Calculation flow chart of mechanical misalignment angle α;

[0037] Figure 6 for Figure 3 The middle two-stage rotor output torque diagram;

[0038] Figure 7 for Figure 6 Composite diagram of rotor torque in the middle two sections;

[0039] Figure 8 for Figure 2 The enlarged diagram of the rotor structure and the marked diagram of the permanent magnet magnetization method;

[0040] Fig. 9 for Figure 8 An enlarged structural diagram and geometric dimension marking diagram of a permanent magnetic steel group;

[0041] Fig.10 for Fig. 9 The enlarged diagram of the structure of the middle arc permanent magnet steel and its geometric dimension marking diagram;

[0042] Fig.11 for Figure 8 An enlarged structural diagram of the first rectangular permanent magnetic steel, the inner magnetic barrier and the outer magnetic barrier and a diagram with geometric dimensions;

[0043] Fig.12 for Figure 8 The structural enlarged diagram and geometric dimension marking diagram of the three permanent magnet steel groups;

[0044] Fig.13 for Fig.12 A magnified schematic diagram of the formation structure of the virtual slot in the middle rotor;

[0045] Fig.14 for Figure 2 A magnified view of the stator structure;

[0046] Fig.15 It is a schematic diagram of the working magnetic circuit of the multi-pole and few-slot unitized permanent magnet hub motor of the present invention under light load;

[0047] Fig.16 It is a schematic diagram of the working magnetic circuit of the multi-pole and few-slot unitized permanent magnet hub motor of the present invention under heavy load;

[0048] Fig.17 It is a structural block diagram of a multi-unit cooperative control system of a multi-pole and few-slot unitized permanent magnet hub motor of the present invention;

[0049] Fig.18 It is a curve diagram of the constant torque area and the constant power area divided according to the critical speed when the multi-unit cooperative control system works;

[0050] Fig.19 For Fig.18 The distribution diagram of the two sub-areas divided by the constant torque area;

[0051] Fig. 20 For Fig.18 Distribution diagram of the eight sub-areas divided by the constant power area.

[0052] Figure 1 Middle: 1. Motor unit; 2. External rotor; 3. Internal stator; 4. Centralized winding; 5. Rotating shaft;

[0053] 2.1. First rotor section; 2.2. Second rotor section; 2.3. Rotor core; 2.4. Permanent magnetic steel group; 2.5. Inner magnetic barrier; 2.6. Outer magnetic barrier; 2.7. Virtual slot;

[0054] 2.4.1. First rectangular permanent magnet; 2.4.2. Second rectangular permanent magnet; 2.4.3. Arc-shaped permanent magnet; 2.4.3.1. Outer long side of arc-shaped permanent magnet; 2.4.3.2. Inner long side of arc-shaped permanent magnet; 2.4.3.3. Short side of arc-shaped permanent magnet;

[0055] 2.5.1. The first side of the inner magnetic barrier; 2.5.2. The second side of the inner magnetic barrier; 2.5.3. The third side of the inner magnetic barrier; 2.5.4. The fourth side of the inner magnetic barrier; 2.5.5. The fifth side of the inner magnetic barrier;

[0056] 2.6.1. The first side of the external magnetic barrier; 2.6.2. The second side of the external magnetic barrier; 2.6.3. The third side of the external magnetic barrier; 2.6.4. The fourth side of the external magnetic barrier; 2.6.5. The fifth side of the external magnetic barrier;

[0057] 3.1. Magnetic ring; 3.2. Stator salient pole; 3.3. Stator pole shoe. DETAILED DESCRIPTION

[0058] See also Figure 1 and Figure 2 As shown, the multi-pole and multi-slot unitized permanent magnet hub motor of the present invention is composed of N identical motor units 1 uniformly distributed along the circumferential direction of the radial section. To ensure that the N motor units 1 can be independently controlled by two control modules, the number N of motor units 1 should satisfy N=2i, where i is a positive integer. The central angle β corresponding to each motor unit 1 on the radial section N =2π / N.

[0059] Each motor unit 1 is composed of 1 / N outer rotors 2, 1 / N inner stators 3, 1 / N concentrated windings 4 and 1 / N rotating shafts 5 along the circumferential direction of the radial section. Therefore, the permanent magnet hub motor composed of N motor units 1 is composed of an outer rotor 2, an inner stator 3, a set of concentrated windings 4 and a rotating shaft 5. The inner stator 3 is coaxial with the outer rotor 2 and is sleeved inside the outer rotor 2. The center of the inner stator 3 is used to place the rotating shaft 5, and the concentrated windings 4 are wound on the inner stator 3. There is an air gap between the inner wall of the outer rotor 2 and the outer wall of the inner stator 3. The thickness of the air gap is related to the power level of the motor, the selected permanent magnet material, and the processing and assembly process of the outer rotor 2 and the inner stator 3. The outer rotor 2 and the inner stator 3 are both laminated by 0.35mm thick silicon steel sheets, and the lamination coefficient is 0.95.

[0060] See also Figure 3 and Figure 4 , the outer rotor 2 of each motor unit 1 is divided into M identical segments along the axial direction, forming M rotor segments, which are the first rotor segment, the second rotor segment, ..., the Mth rotor segment. Considering the reduction of torque pulsation and the reduction of the processing difficulty of the outer rotor 2, the number of M should satisfy: 20mm≤l ef / M≤120mm, where l ef The M rotor segments are arranged and installed in sequence along the same rotation direction by a mechanical offset angle α, and the difference between two adjacent rotor segments is a mechanical offset angle α. Figure 3In the figure, taking M=2 as an example, only two rotor segments are shown, namely the first rotor segment 2.1 and the second rotor segment 2.2. Figure 4 As shown, the first rotor segment 2.1 and the second rotor segment 2.2 are staggered at an angle α, and the mechanical offset angle α is Figure 3 The first rotor segment 2.1 rotates counterclockwise by an angle α relative to the second rotor segment 2.2.

[0061] In order to reduce the torque pulsation of the unitized permanent magnet hub motor, the mechanical misalignment angle α is determined by the following method: Figure 5 As shown:

[0062] Step 1: Assign the initial mechanical misalignment angle α0 to 0.

[0063] Step 2: Use finite element software to simulate the output torque T(t) waveform of motor a when the mechanical misalignment angle is α0, and calculate the motor torque pulsation when the mechanical misalignment angle is α0. The motor torque pulsation is the initial torque pulsation T rip0 Among them, the initial torque ripple T rip0 The calculation method is: first calculate the average value of the output torque T(t), and then make a difference between the maximum and minimum values ​​of the output torque T(t). The percentage of the difference in the average value of the output torque T(t) is the initial torque ripple T. rip0 .

[0064] Step 3: Perform fast Fourier decomposition on the motor output torque T(t) waveform to obtain the harmonic order k of the highest amplitude harmonic component. The motor output torque T(t) waveform is decomposed into a DC component T0, a highest amplitude harmonic component T k cos(kwt+θ k ) and the remaining harmonic components The sum of k is the amplitude of the highest harmonic component, θ k is the phase; s is the number of the remaining harmonic components, and its amplitude is T s , the phase is θ s Therefore, the fast Fourier decomposition expression of the motor output torque T(t) is:

[0065]

[0066] Where t is time and w is the rotation speed of the motor output torque T(t).

[0067] Step 4: Based on the harmonic order k of the highest amplitude harmonic component obtained in step 3, calculate the transition mechanical misalignment angle α1 according to the following formula:

[0068]

[0069] Among them, Pr is the number of motor rotor pole pairs, and M is the number of rotor segments.

[0070] Step 5: Use finite element software to simulate the output torque waveform of the motor when the mechanical misalignment angle is the transition mechanical misalignment angle α1, and calculate the motor torque pulsation at this time, that is, to obtain the transition torque pulsation T rip1 . Transition torque ripple T rip1 Calculation method of the initial torque ripple T in step 2 rip0 The calculation method is similar.

[0071] Step 6: Transition torque pulsation T rip1 and the initial torque ripple T in step 2 rip0 By comparison, it is determined whether the transition mechanical misalignment angle α1 can effectively reduce the torque pulsation. rip1 Less than the initial torque ripple T rip0 , then it is determined that the transition mechanical misalignment angle α1 can effectively reduce the torque pulsation, and step 9 is executed; otherwise, if the transition torque pulsation T rip1 Greater than or equal to the initial torque ripple T rip0 , it is determined that the transition mechanical misalignment angle α1 cannot effectively reduce the torque pulsation, and step 7 is executed.

[0072] Step 7: Assign the transition mechanical misalignment angle α1 to the initial mechanical misalignment angle α0.

[0073] Step 8: Based on the initial mechanical misalignment angle α0 assigned in step 7, use finite element software to simulate and obtain the motor output torque T(t) waveform when the mechanical misalignment angle is the initial mechanical misalignment angle α0 assigned; then repeat steps 3 to 6 until the transition torque pulsation T in step 6 is rip1 Less than the initial torque ripple T rip0 If the judgment result is that the torque pulsation can be effectively reduced, execute step 9.

[0074] Step 9: Assign the transitional mechanical misalignment α1 to the mechanical misalignment angle α and output it.

[0075] At this time, the output torque T generated by the first rotor section 2.1 is 2.1 (t) is the DC component Highest amplitude harmonic component And the remaining harmonic components The sum of is:

[0076]

[0077] The second rotor section 2.2 has a phase θ relative to the first rotor section 2.1. k and θ s The output torque T generated by the second rotor section 2.2 changes.2.2 (t) is the DC component Highest amplitude harmonic component And the remaining harmonic components The sum of is:

[0078]

[0079] By analogy, the phase θ k and θ s The jth rotor segment 2.j of the M rotor segments changes in sequence, j is a positive integer and j≤M, and the output torque T generated by the jth rotor segment 2.j 2.j (t) is the DC component Highest amplitude harmonic component And the remaining harmonic components The sum of is:

[0080]

[0081] It can be seen from this that for M rotor segments, the phase of the kth harmonic in the output torque waveform is That is to say, when the output torque waveforms of all rotor segments are synthesized, the kth harmonic will be compensated and the amplitude of the synthesized harmonic will be 0. That is, the output torque T'(t) of the motor magnetic potential is the DC component and the remaining harmonic components The sum of is:

[0082]

[0083] Since k is the harmonic order of the highest amplitude harmonic component, the torque ripple will decrease as the kth harmonic disappears.

[0084] See also Figure 6 , taking M=2 as an example, the effect of introducing a mechanical misalignment angle α into the rotor is shown. The horizontal axis is the rotor position, in electrical degrees; the vertical axis is the cogging torque, in Nm. Figure 6 The midpoint line is the cogging torque waveform of the first rotor segment 2.1, and the dotted line is the cogging torque waveform of the second rotor segment 2.2. When the rotor position changes in the electrical angle of 0-360°, the cogging torque of the first rotor segment 2.1 and the second rotor segment 2.2 oscillates evenly between [-6.4, 6.1], and when the cogging torque of the first rotor segment 2.1 takes the maximum value, the cogging torque of the second rotor segment 2.2 takes the minimum value, and vice versa. It can be seen that the output torque of the first rotor segment 2.1 and the output torque of the second rotor segment 2.2 achieve peak-to-valley compensation, which is conducive to eliminating the highest amplitude harmonic component, reducing motor torque pulsation, and improving motor torque quality.

[0085] See also Figure 7, the horizontal axis is the rotor position, the unit is electrical degree; the vertical axis is the cogging torque, the unit is Nm. Figure 7 The solid line curve is the actual rotor torque curve after the output torque of the first rotor section 2.1 is combined with the output torque of the second rotor section 2.2. When the rotor position changes in the electrical angle of 0-360°, the rotor torque oscillates evenly between [-1.1, 1]. Figure 6 The torque curve in Figure 7 The peak value of the torque curve in the embodiment is greatly reduced. Therefore, the mechanical misalignment angle α adopted in the present invention can greatly reduce the torque pulsation of the motor and improve the torque quality.

[0086] See also Figure 8 The outer rotor 2 of the permanent magnet hub motor is composed of a rotor core 2.3, 2a permanent magnet steel groups 2.4, 4a inner magnetic barriers 2.5, 4a outer magnetic barriers 2.6 and 4a virtual slots 2.7, where a is a positive integer. The 2a permanent magnet steel groups 2.4 are evenly distributed on the entire rotor core 2.3 along the circumferential direction.

[0087] See also Fig. 9 Each permanent magnet steel group 2.4 is composed of a first rectangular permanent magnet steel 2.4.1, a second rectangular permanent magnet steel 2.4.2 and an arc-shaped permanent magnet steel 2.4.3. The 2a arc-shaped permanent magnet steels 2.4.3 are embedded inside the inner surface of the outer rotor 2, and the 2a arc-shaped permanent magnet steels 2.4.3 are evenly arranged along the circumferential direction. The center line of each arc-shaped permanent magnet steel 2.4.3 on the radial section is consistent with the diameter direction, and the center line of the permanent magnet steel group 2.4 coincides with the center line of the arc-shaped permanent magnet steel 2.4.3. The first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 have the same structure, and the radial cross-sections are both rectangular. They are both located outside the arc-shaped permanent magnet steel 2.4.3. The first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 belonging to the same permanent magnet steel group 2.4 are symmetrically placed relative to the center line of the permanent magnet steel group 2.4, and the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 are also symmetrically placed relative to the center of the arc-shaped permanent magnet steel 2.4.3. The first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 belonging to the same permanent magnet steel group 2.4 are arranged in a "V" shape with the opening facing the air gap side, and the inner and outer oblique directions are the length direction of the rectangle. The arc-shaped permanent magnet steel 2.4.3 is placed in the middle of the V-shaped opening formed by the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2, and the three permanent magnet steels do not contact each other.

[0088] like Figure 8, the magnetization directions of the first rectangular permanent magnet 2.4.1 and the second rectangular permanent magnet 2.4.2 in the same permanent magnet group 2.4 are perpendicular to the long sides of the magnets themselves and consistent with their width directions, and the magnetization direction of the arc permanent magnet 2.4.3 is consistent with the center line direction, pointing to or away from the center of the circle. The magnetization directions of the first rectangular permanent magnet 2.4.1, the second rectangular permanent magnet 2.4.2 and the arc permanent magnet 2.4.3 belonging to the same permanent magnet group 2.4 are simultaneously pointing to or away from the air gap, and the magnetization directions of two adjacent permanent magnet groups 2.4 are opposite.

[0089] The first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 are each provided with a magnetic barrier at the end close to the air gap and the end away from the air gap, that is, the inner end and the outer end of the rectangular permanent magnet steel are each provided with a magnetic barrier. Respectively: the inner end of each first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 each has an inner magnetic barrier 2.5, so there are 4a inner magnetic barriers 2.5; the outer end of each first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 each has an outer magnetic barrier 2.6, so there are 4a outer magnetic barriers 2.6. Along the inner side surface of the outer rotor 2, a virtual slot 2.7 is provided at each end of each arc-shaped permanent magnet steel 2.4 along the tangent direction, so there are 4a virtual slots 2.7, and the virtual slots 2.7 are connected to the air gap, become one with the air gap, and become part of the air gap.

[0090] See also Fig. 9 In order to take into account both the weak magnetic speed expansion capability and the peak torque output capability of the permanent magnet hub motor, the V-shaped angle β formed between the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 is pm Should meet: 40°≤β pm ≤65°. In addition, in order to strengthen the strength of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 and to ensure the difficulty of processing and stress distribution, the long side length w of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 is pm With wide side length h pm Should satisfy: 2≤w pm / h pm ≤4.

[0091] See also Fig.10Each arc-shaped permanent magnet 2.4.3 is surrounded by an arc-shaped permanent magnet outer long side 2.4.3.1, an arc-shaped permanent magnet inner long side 2.4.3.2 and two arc-shaped permanent magnet short sides 2.4.3.3 symmetrical along the center of the arc-shaped permanent magnet 2.4.3.3. The arc center of the arc-shaped permanent magnet outer long side 2.4.3.1 is the same as the center of the outer rotor 2. The center angle corresponding to the arc-shaped permanent magnet inner long side 2.4.3.2 is the same as the center angle corresponding to the arc-shaped permanent magnet outer long side 2.4.3.1. The arc-shaped permanent magnet short side 2.4.3.3 is consistent with the diameter direction of the outer rotor 2 and is on a radius of the outer rotor 2. The inner long side 2.4.3.2 of the arc-shaped permanent magnet steel is a half-period sine curve, and the independent variable θ1 of the sine curve ranges from [π, 2π], that is, the sine curve function of the inner long side 2.4.3.2 of the arc-shaped permanent magnet steel is:

[0092] f1(θ1)=f 1max sin(θ1),θ1∈[π,2π],

[0093] where f 1max is the amplitude of the sine curve, which is determined by the specific performance requirements of the motor. When θ1 is 3π / 2, the corresponding point f1(3π / 2) on the sine curve is exactly located on the inner surface of the outer rotor 2. Therefore, the arc-shaped permanent magnet steel 2.4.3 is integrally embedded inside the inner surface of the outer rotor 2, and the point f1(3π / 2) when θ1 is 3π / 2 coincides with the inner surface of the outer rotor 2.

[0094] The design of the sinusoidal curve shape of the inner long side 2.4.3.2 of the arc-shaped permanent magnet changes the magnetic potential waveform of the arc-shaped permanent magnet 2.4.3. The magnetic potential waveform of the arc-shaped permanent magnet 2.4.3 changes from the original square wave to the superposition waveform of the rectangular wave and the sine wave, which changes the harmonic distribution of the magnetic potential of the arc-shaped permanent magnet 2.4.3, improves the sinusoidality of the magnetic potential waveform of the arc-shaped permanent magnet 2.4.3, and increases the amplitude of the magnetic potential base wave, which is beneficial to the improvement of the motor torque output capacity. At the same time, the design of this sinusoidal curve shape also reduces the amplitude of the permanent magnet magnetic potential base wave, which is beneficial to the reduction of the motor core loss.

[0095] See also Fig.10 In order to enhance the permanent magnetic field of the motor and reduce the magnetic resistance of the main magnetic circuit to increase the peak torque of the motor, the minimum width h of the arc permanent magnet steel in the radial direction is pmin Should meet: 6 ≤ h pm / h pmin ≤8. In addition, in order to reduce the harmonics of the permanent magnetic field and reduce the iron loss of the motor, while reducing the average air gap width of the motor and the magnetic resistance of the main magnetic circuit, the minimum width h of the arc permanent magnetic steel 2.4.3 is pmin The maximum width h of the arc permanent magnet 2.4.3 pmax Should meet: 1.5≤hpmax / h pmin ≤2.

[0096] See also Fig.11 and Fig.12 The inner magnetic barriers 2.5 respectively arranged at the ends of the first rectangular permanent magnetic steel 2.4.1 and the second rectangular permanent magnetic steel 2.4.2 near the air gap have the same structure and are symmetrically distributed along the center line of the permanent magnetic steel group 2.4. Take the inner magnetic barrier 2.5 at the end of the first rectangular permanent magnetic steel 2.4.1 as an example: the radial cross section of the inner magnetic barrier 2.5 is a "pentagon", which is surrounded by the first side 2.5.1 of the inner magnetic barrier, the second side 2.5.2 of the inner magnetic barrier, the third side 2.5.3 of the inner magnetic barrier, the fourth side 2.5.4 of the inner magnetic barrier and the fifth side 2.5.5 of the inner magnetic barrier. The first side 2.5.1 of the inner magnetic barrier is an extended side of the long side of the first rectangular permanent magnetic steel 2.4.1 near the air gap, and the second side 2.5.2 of the inner magnetic barrier is an arc side coaxial with the outer rotor 2 of the motor. In order to construct a permanent magnetic field leakage magnetic circuit, broaden the motor speed regulation range and improve the motor high-speed area operating efficiency while controlling the motor leakage degree, and improve the motor low-speed light-load area torque output capacity, the distance h between the second side of the inner magnetic barrier 2.5.2 and the inner surface of the outer rotor 2 is b1 Should meet: 0.75≤h b1 / h pm ≤0.9. The third side 2.5.3 of the inner magnetic barrier is located on the radius of the outer rotor 2. The fourth side 2.5.4 of the inner magnetic barrier is parallel to the first side 2.5.1 of the inner magnetic barrier and is located outside the first side 2.5.1 of the inner magnetic barrier, that is, away from the air gap side. In order to ensure that the uncontrollable magnetic leakage of the first rectangular permanent magnetic steel 2.4.1 and the second rectangular permanent magnetic steel 2.4.2 is reduced while ensuring the reliability of their installation, the distance h between the first side 2.5.1 of the inner magnetic barrier and the fourth side 2.5.4 of the inner magnetic barrier is b2 Smaller than the width of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2, and should meet the following requirements: 0.8h pm ≤h b2 ≤0.9h pm The fifth side 2.5.5 of the inner magnetic barrier coincides with the short sides of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 close to the air gap.

[0097] The ends of the first rectangular permanent magnet 2.4.1 and the second rectangular permanent magnet 2.4.2 away from the air gap are respectively provided with external magnetic barriers 2.6, and the two external magnetic barriers 2.6 have the same structure and are symmetrically distributed along the center line of the permanent magnet group 2.4. Take the external magnetic barrier 2.6 at the end of the first rectangular permanent magnet 2.4.1 as an example: the radial cross section of the external magnetic barrier 2.6 is also a "pentagon", which is surrounded by the first side 2.6.1 of the external magnetic barrier, the second side 2.6.2 of the external magnetic barrier, the third side 2.6.3 of the external magnetic barrier, the fourth side 2.6.4 of the external magnetic barrier and the fifth side 2.5.5 of the external magnetic barrier. The first side 2.6.1 of the external magnetic barrier is located on the extension line of the long side of the first rectangular permanent magnet 2.4.1 close to the air gap, and the second side 2.6.2 of the external magnetic barrier is located on the radius of the outer rotor 2. The third side 2.6.3 of the external magnetic barrier is an arc side coaxial with the outer rotor 2. In order to reduce the uncontrollable magnetic leakage of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2 while reducing the q-axis magnetic resistance to maximize the torque, the distance h between the third side 2.6.3 of the external magnetic barrier and the outer surface of the outer rotor 2 is b3 Should meet: 0.2(R ro -R ri )≤h b3 ≤0.35(R ro -R ri ), where R ro is the outer diameter of the outer rotor 2, R ri is the inner diameter of the outer rotor 2. The fourth side 2.6.4 of the outer magnetic barrier is parallel to the first side 2.6.1 of the outer magnetic barrier and is located outside the first side 2.6.1 of the outer magnetic barrier, that is, away from the air gap side. In order to reduce the magnetic leakage of the first rectangular permanent magnet 2.4.1 and the second rectangular permanent magnet 2.4.2 while ensuring their installation reliability, the distance h between the first side 2.6.1 of the outer magnetic barrier and the fourth side 2.6.4 of the outer magnetic barrier is b4 Smaller than the width of the first rectangular permanent magnet steel 2.4.1 and the second rectangular permanent magnet steel 2.4.2, and should meet the following requirements: 0.8h pm ≤h b4 =h b1 ≤0.9h pm The fifth side 2.5.5 of the outer magnetic barrier coincides with the short sides of the first rectangular permanent magnetic steel 2.4.1 and the second rectangular permanent magnetic steel 2.4.2 away from the air gap. Fig.13In order to improve the sinusoidality of the air gap magnetic density and reduce the iron loss and torque pulsation of the motor, two virtual slots 2.7 are symmetrically arranged at both ends of the arc-shaped permanent magnet steel 2.4.3 along the center line of the arc-shaped permanent magnet steel 2.4.3. Each virtual slot 2.7 is a sine curve. On the radial cross section, the intersection of the virtual slot 2.7 and the end of the inner long side 2.4.3.2 of the arc-shaped permanent magnet steel 2.4.3 is point A, which is also the intersection of the inner long side 2.4.3.2 of the arc-shaped permanent magnet steel and the short side 2.4.3.3 of the arc-shaped permanent magnet steel. The intersection of the second side 2.5.2 of the inner magnetic barrier and the third side 2.5.3 of the inner magnetic barrier is point B, and the intersection of a radius passing through point B and the inner surface of the outer rotor 2 is point C. Then from point A to point C is a sine curve, forming a virtual slot 2.7. The range of the independent variable θ2 of this sine curve of the virtual slot 2.7 is [π / 2,π], and the sine curve function of the virtual slot 2.7 is:

[0098] f2(θ2)=f 2max sin(θ2),

[0099] Among them, f 2max is the amplitude of the function, which is determined by the specific performance requirements of the motor. When θ2 is π / 2, point f2(π / 2) on the sine curve coincides with point A, and when θ2 is π, point f2(π) on the sine curve coincides with point C.

[0100] The virtual slot 2.7 can change the magnetic permeability waveform of the outer rotor 2 and the air gap magnetic potential waveform of the permanent magnetic field. The magnetic permeability is transformed from the original square wave to the superimposed waveform of the square wave and the sine wave. At the same time, the pole clipping treatment of the permanent magnetic potential waveform of the permanent magnetic steel group 2.4 is realized, and the sinusoidality of the magnetic potential waveform of the arc-shaped permanent magnetic steel 2.4.3 is improved, so that the amplitude of the magnetic potential base wave is increased, which is beneficial to the improvement of the torque output capacity of the motor. At the same time, the design of the virtual slot 2.7 reduces the amplitude of the permanent magnetic potential base wave, which is beneficial to the reduction of the motor core loss.

[0101] See also Fig.14 The inner stator 3 of the permanent magnet hub motor is composed of a magnetic ring 3.1, B stator salient poles 3.2 and 2B stator pole shoes 3.3, where B = mj, m is the number of motor phases, and j is a positive integer. A stator pole shoe 3.3 extends tangentially from the outer end of each stator salient pole 3.2. The stator salient pole 3.2 is rectangular in radial cross-section and is evenly distributed along the circumferential direction of the outer surface of the magnetic ring 3.1. At the same time, a completely identical stator pole shoe 3.3 is provided on both tangential sides of the outer end of the stator salient pole 3.2. The radial width of the magnetic ring 3.1, the radial length and tangential width of the stator salient pole 3.2, and the tangential width of the stator pole shoe 3.3 are determined by the motor power.

[0102] The rotor pole pair number P of the multi-pole and few-slot unitized permanent magnet hub motor of the present invention isr , number of stator slots N s , the number of motor phases m, the number of motor units 1 N should meet the following conditions: (1) more poles and fewer slots: the number of rotor pole pairs P r Greater than the number of stator slots N s ; The motor slot angle τ is the number of rotor pole pairs P r Divide by the number of stator slots N s The product of the quotient and 2π. (2) Rotor unitization: Unitized motors require that the rotor can be divided into N parts, that is, the number of rotor pole pairs P r It should be an integer multiple of the number N of motor units 1; (3) Stator unitization: The stator is required to be divided into N parts, so the number of stator slots N s It should be an integer multiple of the number of phases m, and an integer multiple of the number of motor units 1 N; (4) Unitization of control modules: In order to improve the degree of freedom of unitized motor control and improve the overall operating efficiency and performance of the motor, the multi-pole and few-slot unitized permanent magnet hub motor described in the present invention is equipped with two control modules. It is required that the number of motor units 1 N is an integer multiple of 2; (5) Centralized winding: The winding is a centralized winding 4, that is, the winding span should be 1; (6) Unitization of windings: On the basis of stator unitization, it is necessary to satisfy that the windings in each motor unit 1 are three-phase symmetrical and have the same distribution, that is, there are positive integers i, a, b, c, d, e that make the following equations hold simultaneously:

[0103]

[0104] For the multi-pole and few-slot unitized permanent magnet hub motor described in the present invention, the condition for its light-load operation is defined as the motor output torque T satisfies: T≤0.6T rated , where T rated is the rated output torque of the motor; the heavy-load operation condition is that the motor output torque T satisfies: T>0.6T rated The condition for low-speed operation is defined as the motor speed n meeting the condition: n≤n rated , where n rated is the rated speed of the motor; the condition for high-speed operation is that the motor speed n satisfies the condition: n>n rated .

[0105] See also Fig.15When the multi-pole and few-slot unitized permanent magnet hub motor described in the present invention is running under light load, the two magnetic circuits in the motor are the main magnetic circuit I and the leakage magnetic circuit II, and the main magnetic circuit I is connected in parallel with the leakage magnetic circuit II. The magnetic flux path of the main magnetic circuit I is as follows: starting from the first rectangular permanent magnet 2.4.1 in the first permanent magnet group 2.4, it passes through the rotor core 2.3, the first arc-shaped permanent magnet 2.4.3, the air gap, the inner stator 3, the air gap, the second arc-shaped permanent magnet 2.4.3 adjacent to the first arc-shaped permanent magnet 2.4.3, the rotor core 2.3, the second rectangular permanent magnet 2.4.2 in the second permanent magnet group 2.4 adjacent to the first permanent magnet group 2.4, the rotor core 2.3, and finally returns to the first rectangular permanent magnet 2.4.1 to form a closed magnetic circuit. Due to the existence of the leakage magnetic circuit, there is a leakage magnetic circuit II in the motor which is different from the traditional magnetic circuit. The magnetic flux path of the leakage magnetic circuit II is: starting from the first rectangular permanent magnetic steel 2.4.1 in the first permanent magnetic steel group 2.4, passing through the rotor core 2.3, the second arc-shaped permanent magnetic steel 2.4.3 adjacent to the first arc-shaped permanent magnetic steel 2.4.3, the rotor core 2.3, the second rectangular permanent magnetic steel 2.4.2 in the second permanent magnetic steel group 2.4 adjacent to the first permanent magnetic steel group 2.4, the rotor core 2.3, and finally returning to the first rectangular permanent magnetic steel 2.4.1 to form a closed magnetic circuit in the outer rotor 2. It can be seen that the main magnetic circuit I is connected in parallel with the leakage magnetic circuit II.

[0106] See also Fig.16 When the multi-pole and few-slot unitized permanent magnet hub motor of the present invention is running under heavy load, there are two magnetic circuits in the motor, namely the main magnetic circuit I and the q-axis magnetic circuit III, and the main magnetic circuit I and the q-axis magnetic circuit III run in parallel. Fig.15 The magnetic flux path of the q-axis magnetic circuit III is the same as the main magnetic circuit I during light load operation in the embodiment. The magnetic flux path of the q-axis magnetic circuit III is: starting from the inner stator 3, passing through the air gap, the arc-shaped permanent magnetic steel 2.4.3, the rotor core 2.3, the adjacent arc-shaped permanent magnetic steel 2.4.3, the air gap, and finally returning to the inner stator 3 to form a closed magnetic circuit. It can be seen that the main magnetic circuit I is connected in parallel with the q-axis magnetic circuit III.

[0107] Combination Fig.15 and Fig.16 It can be seen that the leakage magnetic circuit II and the q-axis magnetic circuit III partially overlap and the magnetic resistance of the overlapping section is large, which is very easy to saturate. When the multi-pole and few-slot unitized permanent magnet hub motor of the present invention is running at low speed and light load, the motor speed and torque are both low, so the current amplitude I output by the concentrated winding 4 is small, then the q-axis current component i qThat is, the magnetic flux of q-axis magnetic circuit III is weak, and the section where leakage magnetic circuit II and q-axis magnetic circuit III overlap is saturated by the magnetic flux of leakage magnetic circuit II. When the motor is running at high speed and light load, the motor torque is high at this time, the output current amplitude I of the concentrated winding 4 is large, and its current angle is large, and the q-axis current component i q The magnetic circuit distribution is the same as that of low-speed and light-load operation. At the same time, since the magnetic flux of the q-axis magnetic circuit III is weak and the magnetic flux of the leakage magnetic circuit II is strong, the excitation magnetic field of the motor is weakened. This phenomenon makes the copper loss of the motor of the present invention lower in the high-speed area compared with the traditional motor. In addition, when the motor of the present invention is running under heavy load, as the q-axis current component i q As the magnetic flux of the motor q-axis magnetic circuit III increases, the magnetic flux of the leakage magnetic circuit II will gradually weaken until it disappears. At this time, all the magnetic flux of the permanent magnet steel group 2.4 forms an effective magnetic flux through the main magnetic circuit I, thereby improving the motor torque output capacity.

[0108] See also Fig.17 , for the multi-pole and few-slot unitized permanent magnet hub motor described in the present invention, a coordinated control system is used to control it. The coordinated control system includes a battery, two control modules and N winding electronic switches, wherein a winding electronic switch is connected to a centralized winding 4 in a motor unit 1 to control the on and off of the centralized winding 4 in a motor unit 1. Each control module is composed of a power electronic switch, a DSP controller and an inverter connected in series in sequence, the input ends of the two power electronic switches are respectively connected to the output ends of the battery, and the output ends of each inverter are respectively connected to N / 2 winding electronic switches, that is, the first control module is composed of a first power electronic switch, a first DSP controller and a first inverter connected in series in sequence, and the second control module is composed of a second power electronic switch, a second DSP controller and a second inverter connected in series in sequence. The power electronic switches in the two control modules are independent of each other, and the two control modules are independent of each other and have the same structure. Each controls N / 2 motor units 1, which reduces the coupling between the two modules and improves the degree of freedom and control quality of the multi-pole and few-slot unitized permanent magnet hub motor.

[0109] The N winding electronic switches are divided into two independent groups, and each group of winding electronic switches controls N / 2 motor units 1. The N winding electronic switches are divided into two groups and connected to two control modules respectively. For example, the first winding electronic switch is connected to the first motor unit 1, the second winding electronic switch is connected to the second motor unit 1, the N / 2 winding electronic switch is connected to the N / 2 motor unit 1, the N / 2+1 winding electronic switch is connected to the N / 2+1 motor unit 1, and the N winding electronic switch is connected to the N motor unit 1. The input ends of the first winding electronic switch to the N / 2 winding electronic switch, a total of N / 2 winding electronic switches, are respectively connected to the first inverter in the first control module. The input ends of the N / 2+1 winding electronic switch to the N winding electronic switch, a total of N / 2 winding electronic switches, are respectively connected to the second inverter in the second control module. In this way, each motor unit 1 can be independently controlled to be turned on and off through the corresponding winding electronic switch, and the total armature magnetic field strength of the motor can be transformed in multiple levels, which is conducive to adjusting the motor magnetic field and realizing multi-condition operation of the motor. The control of the independent motor units 1 can further improve the operating freedom of the multi-pole and few-slot unitized permanent magnet hub motor, and provide a hardware foundation for improving the working efficiency of the motor and its coordinated control system.

[0110] In addition, the output ends of the concentrated windings 4 of all motor units 1 are connected to the battery via a feedback module. The main component of the feedback module is a rectifier. When the energy generated by the motor in the power-up operation mode is higher than the energy required for the wheel hub drive, the remaining energy is recovered to the battery through the feedback module.

[0111] The collaborative control system adopts the following control strategy to control the multi-pole and few-slot unitized wheel hub permanent magnet motor proposed in the present invention:

[0112] Step 1: Use finite element software simulation to obtain the external characteristic curve of the motor when the control module is working.

[0113] The two power electronic switches and N winding electronic switches are closed, and the external characteristic curve g of the motor is obtained by finite element simulation, as shown in Fig.18 As shown. Keep N winding electronic switches closed, so that only one of the first power electronic switch and the second power electronic switch is closed, that is, one of the power electronic switches is disconnected, and only one control module is working. Finite element software is used to simulate and obtain the external characteristic curve f of the motor at this time; the horizontal axis is the motor speed n, in rpm; the vertical axis is the motor output torque T, in Nm.

[0114] Step 2: Based on the obtained external characteristic curve, divide the motor into a constant torque region and a constant power region.

[0115] Step 2.1: First calculate the critical speed n bThe maximum torque T is obtained from the external characteristic curve f max , critical speed n b is the maximum torque T max The corresponding maximum speed is:

[0116]

[0117] Among them, n i It is the speed set of the working point when the motor outputs peak torque.

[0118] Step 2.2: According to the critical speed n b , divide the constant torque area and the constant power area. Set point P(n p ,T p ) is any operating point of the motor, n p is the speed at that point, T p is the torque at this point. p Satisfy n p ≤n b When , this point belongs to the constant torque area, that is, the speed n of the motor running point in the constant torque area p ≤n b ; If the speed of the point n p Satisfy n p >n b When , this point belongs to the constant power area. Fig.18 The vertical dotted line h in the figure is the boundary between the constant torque zone and the constant power zone. The speed n at the boundary is p =n b .

[0119] Step 3: Then divide the constant torque area into the first area, a low-speed load area, and the second area, a low-speed overload area, according to the critical torque.

[0120] Step 3.1: Calculate the peak torque T of a motor unit 1 based on finite element software simulation x Under the premise that both the first power switch and the second power electronic switch are closed, that is, both the first control module and the second control module are working, and only one of the winding electronic switches is closed, the peak torque of the motor at this time is simulated by finite element software. The torque is the peak torque T of a motor unit 1. x ;

[0121] According to the peak torque T of a motor unit 1 x Calculate the critical torque T b . Critical torque T b is the peak torque T of a motor unit 1 x N-2 times, that is:

[0122] T b =(N-2)Tx .

[0123] Step 3.3: See Fig.19 , the horizontal axis is the motor speed, in rpm; the vertical axis is the motor output torque, in Nm. Based on the critical torque T b , two zones are determined, namely the first zone low speed load zone and the second zone low speed overload zone. p ,T p ) meets the following conditions: T p ≤T b , n p ≤n b When the operating point P(n p ,T p ) belongs to the first zone low speed load zone, that is, in the constant torque zone, if the operating point P(n p ,T p ) of the torque T p Equal to or less than the critical torque T b , then the operating point P(n p ,T p ) belongs to the first zone, low speed load zone S1; on the contrary, P(n p ,T p ) meets the following conditions: T p >T b , n p ≤n b When the point P belongs to the second zone low speed overload zone S2, the operating point P (n p ,T p ) of the torque T p The maximum value does not exceed the torque of the external characteristic curve g. The differentiation result of the constant torque area is:

[0124]

[0125] Fig.19 The horizontal straight line j in is the boundary between the first zone low speed load zone and the second zone low speed overload zone, and its function expression is:

[0126] T(n)=T b ,n∈[0,n b ].

[0127] The two sub-regions of the constant torque area are shown with different marks. Fig.19 Middle: The grid area is the first zone low speed and load area, and the left diagonal area is the second zone low speed and low load area.

[0128] Step 4: Based on the partitioning result of the constant torque zone in step 3, determine the control method of the first zone low-speed load zone. The main control principle of the first zone low-speed load zone is the principle of minimum torque pulsation: the first power electronic switch and the second power electronic switch are both closed, the first inverter and the second inverter output currents of the same amplitude but different phases, and adjust the output torque phases of the two control modules to achieve valley-peak overlap and eliminate high-order harmonics. For any operating point P1(n p1 ,T p1 ), n p1 is the speed at that point, T p1 For the torque at this point, the control method is implemented according to the following steps:

[0129] Step 4.1: Output torque T according to motor requirements p1 , calculate the number K of closed winding electronic switches connected to each control module, 1≤K≤N / 2.

[0130] Since at the operating point P1(n p1 ,T p1 ), the output torque required by the motor is T p1 , so the required torque output of a single control module is T p1 / 2. The peak torque of the single motor unit 1 obtained from step 3.1 is T x Therefore, in the N / 2 motor units 1 connected to each control module, the number of winding electronic switches that need to be closed at least is (T p1 / 2T x ). In order to ensure the torque output capacity of the motor, the number of closed electronic switches K of the winding in each control module is rounded by the "round-up method", that is:

[0131]

[0132] Step 4.2: Based on the number K of closed winding electronic switches in 4.1, finite element software is used to simulate and calculate the transition current output by the two inverters at the output torque T2(t) when the number of closed winding electronic switches is K.

[0133] The first power electronic switch and the second power electronic switch are both closed, and K switches are arbitrarily closed from the first winding electronic switch to the N / 2 winding electronic switch, and K switches are arbitrarily closed from the (N / 2+1) winding electronic switch to the N winding electronic switch. At this time, the output currents of the two inverters are exactly the same. The finite element software is used to simulate and calculate the motor output torque waveform T2(t) and the transition current output by the two inverters at this time, which is the transition current amplitude I max0 , the transition current phase is a sinusoidal function of θ0, and the expression is:

[0134]

[0135]

[0136] in are respectively transition currents output by the first inverter; are the transient current output by the second inverter, n p is the operating point P(n p ,T p ) speed, P r is the number of rotor pole pairs.

[0137] Step 4.3: Based on the result of step 4.2, the waveform of the output torque T2(t) is obtained by fast Fourier decomposition to obtain the harmonic order r of the main harmonic component.

[0138] The waveform of the output torque T2(t) is decomposed into the DC component T by fast Fourier transform. 20 , the main harmonic component T r cos(rw2t+θ r ) and the remaining harmonic components The sum of the main harmonic components T r cos(rw2t+θ r ) has an amplitude of T r , the phase is θ r ; Residual harmonic components The number is v and the amplitude is T v , the phase is θ v Therefore, the fast Fourier decomposition expression of the output torque T2(t) is:

[0139]

[0140] Here, w2 is the rotation speed of the output torque T2(t).

[0141] Step 4.4: Based on the main harmonic components T r cos(rw2t+θ r ) and calculate the current misalignment angle β. The current misalignment angle β is the angle difference between the current phases output by the two inverters, and its calculation method is the quotient of π / 2 and the harmonic order r of the main harmonic component, that is:

[0142]

[0143] Step 4.5: Transition current based on the output of the two inverters in step 4.2 And the current misalignment angle β calculated in step 4.4 is used to determine the ABC three-phase currents output by the two inverters.

[0144] In order to ensure the motor torque output capacity, the current amplitude I max At the transition current amplitude I max0 5% increase on the basis of I max =1.05I max0 The phase of the ABC three-phase current output by the first inverter leads the excessive current Phase β / 2, the phase of the ABC three-phase current output by the second inverter lags behind the excessive current The phase is β / 2, that is, the expression is:

[0145]

[0146]

[0147] Among them, I 1A , I 1B and I 1C I is the ABC three-phase current output by the first inverter; 2A , I 2B and I 2C is the ABC three-phase current output by the second inverter, n p is the operating point P(n p ,T p ) speed, P r is the number of rotor pole pairs.

[0148] The three-phase current I 1A , I 1B and I 1C , I 2A , I 2B and I 2C The three-phase currents are stored in the first and second DSP controllers respectively, and the first and second DSP controllers respectively control the first inverter and the second inverter to output three-phase currents.

[0149] Step 5: Based on the partitioning result of the constant torque zone in step 3, determine the control method of the second zone low speed overload zone. Since the second zone low speed overload zone requires higher motor torque, all motor units 1 are made to work together, that is, for any operating point P2 (n p2 ,T p2 ), all power electronic switches and all winding electronic switches are closed, and then the finite element software is used to simulate and calculate the motor running at point P2 (n p2 ,T p2 ) is the ABC three-phase current output by the two inverters.

[0150] Step 6: At the same time as step 3, based on the result in step 2, the constant power zone is partitioned in detail. In view of the fact that the operating conditions in the constant power zone are relatively complex, the constant torque zone is divided into 6 sub-areas, divided into the third to eighth zones. Among them, the third zone is the high-speed low-load zone, denoted as S3; the fourth zone is the high-speed high-efficiency zone, denoted as S4; the fifth zone is the high-speed load zone, denoted as S5; the fifth zone is the double high-efficiency zone, denoted as S6; the seventh zone is the high-speed overload zone, denoted as S7; the eighth zone is the high-speed weak magnetic zone, denoted as S8. The operating point P(n p ,T p )The maximum value of the torque does not exceed the torque corresponding to the external characteristic curve g.

[0151] Step 6.1: Determine the scope of the fourth zone high-speed and high-efficiency zone.

[0152] Step 6.1.1: Simulate and calculate the efficiency map of a single control module. At this time, only one of the first power electronic switch and the second power electronic switch is closed, and all winding electronic switches are closed. Under this premise, the efficiency map of the motor operation is obtained by simulation using finite element software, and the maximum efficiency η of the motor operated by a single control module is determined based on the efficiency map. max .

[0153] Step 6.1.2: Maximum motor efficiency η based on single control module operation max , calculate the boundary efficiency η b : Boundary efficiency η b 95% of the maximum efficiency of the motor running with a single control module, that is:

[0154] η b =0.95η max .

[0155] Step 6.1.3: Based on the boundary efficiency η b Determine the scope of the fourth zone high speed and high efficiency zone. The fourth zone high speed and high efficiency zone is the boundary efficiency η b That is, when any operating point P(n p , T p ) efficiency η p Satisfy the conditions: η p≥ η b , then point P(n p , T p ) belongs to the fourth zone, high-speed and high-efficiency zone, that is:

[0156] S4={P(n p ,T p )|η p ≥η b And n p >nb}.

[0157] After the fourth zone high speed and high efficiency zone is determined, the highest speed point E and the lowest speed point D of the fourth zone high speed and high efficiency zone are obtained, such as Fig. 20 shown.

[0158] Step 6.2: Based on the result of step 6.1, determine the scope of the high-speed weakening magnetic zone in the eighth zone.

[0159] Step 6.2.1: The highest speed point E in the fourth zone of high speed and high efficiency is not unique, so the lowest torque point among all the highest speed points is taken as the required highest speed point E, and a straight line j perpendicular to the horizontal axis passing through the required highest speed point E is obtained.

[0160] Step 6.2.2: Determine the range of the eighth zone high-speed weak magnetic zone. The area enclosed by the horizontal axis, curve g and straight line j is the eighth zone high-speed weak magnetic zone. The speed of the eighth zone high-speed weak magnetic zone is higher than the speed n of the required maximum speed point E. E .

[0161] Step 6.3: Based on the results in step 6.1 and step 6.2, determine the range of the third zone high speed low load zone.

[0162] Step 6.3.1: Based on the results in step 6.1, if the lowest speed point D(n D ,T D ) is not unique, where n D and T D They are the lowest speed point D(n D ,T D ) speed and torque, then take the lowest speed point D(n D ,T D ) The lowest torque point is the required lowest speed point D, and a straight line k perpendicular to the horizontal axis passing through the required lowest speed point D is obtained.

[0163] Step 6.3.2: Based on the results in step 6.3.1, determine the range of the third zone high speed low load zone in the area where the speed is less than point D, denoted as S 31 In the constant power area, the torque is less than the torque T at point D. D And the speed is less than the speed n at point D D The area belongs to the third zone, high speed and low load zone. That is, when point P(n P ,T P ) satisfies the following conditions: n p <n D And T P <T D When point P(n P ,T P ) belongs to the third zone, high speed and low load zone, that is:

[0164] S 31 = {P(n p ,T p )|n b <n p <n D ,0≤T p <T D}.

[0165] Step 6.3.3: Determine the speed greater than point D(n D ,T D ) and is less than point E(n E ,T E ) in the area of ​​the third zone, high speed and low load zone, denoted as S 32 . S 32 It is the area enclosed by the abscissa axis, straight line k, the lower half boundary line of the fourth zone high-speed and high-efficiency zone (the lower half connecting line between point E and point D) and straight line j.

[0166] Step 6.3.4: Based on Step 6.3.2 and Step 6.3.3, determine the range of the third zone high speed low load zone. The third zone high speed low load zone is S 31 With S 32 The union of , that is:

[0167] S3=S 31 ∪S 32 .

[0168] It is worth noting that the third zone, high speed and low load zone S 31 With S 32 The size of will change with the change of motor characteristics. For some motors, some sets may be empty sets.

[0169] Step 6.4: At the same time as step 6.3, based on the high-speed and high-efficiency zone of the fourth zone determined in step 6.1, the double high-school zone of the sixth zone is determined. The double high-school zone of the sixth zone is a double expansion area of ​​the high-speed and high-efficiency zone of the fourth zone, and its expansion method is that the speed remains unchanged and the torque is expanded to twice the original; that is, the speed of the double high-school zone of the sixth zone is the same as the speed of the high-speed and high-efficiency zone of the fourth zone, the highest speed point G of the double high-school zone of the sixth zone is on the straight line j, and the lowest speed point F is on the straight line k; for each operating point P6(n P6 ,T P6 ), the torque is the same speed n in the fourth zone high speed and high efficiency zone P6 For any point P6(n P6 ,T P6 ) are all double expansion points of a certain point in the high-speed and high-efficiency zone of the fourth zone. That is, when point P(nP ,T P ) belongs to the sixth zone double efficiency zone, point P must meet the following conditions: P' is a point in the high-speed and high-efficiency zone of the fourth zone, that is:

[0170]

[0171] Step 6.5: Based on the results in step 6.1 and step 6.4, determine the range of the fifth zone high-speed load zone.

[0172] Step 6.5.1: The torque is less than the torque T at point F F And the torque is higher than point D and the speed is lower than point F speed n F The area belongs to the fifth zone high-speed load zone, denoted as S 51 That is, when point P(n P ,T P ) satisfies the following conditions: n p <n F And T D ≤T P <T F When point P(n P ,T P ) belongs to the fifth zone high-speed load zone, that is:

[0173] S 51 = {P(n p ,T p )|n b <n p <n F ,T D ≤T p ≤T F}.

[0174] Step 6.5.2: Determine the speed greater than point F(n F ,T F ) and is smaller than point G(n G ,T G ) in the area of ​​the fifth zone high-speed load zone, denoted as S 52 . S 52 It is the area formed by straight line k, straight line j, the upper half boundary of the fourth zone high speed and high efficiency zone and the lower half boundary of the sixth zone double high efficiency zone.

[0175] Step 6.5.3: Based on Step 6.5.1 and Step 6.5.2, determine the range of the fifth zone high-speed load zone. The fifth zone high-speed load zone is S 51 With S 52 The union of , that is:

[0176] S5=S 51 ∪S 52.

[0177] It is worth noting that the fifth zone high-speed load zone S 51 With S 52 The size of S will change with the change of motor characteristics. For some motors, S may appear 51 With S 52 There are cases where one or both of them are empty sets.

[0178] Step 6.6: Based on the results in steps 6.1 to 6.5, determine the range of the high-speed overload zone of zone 7.

[0179] The seventh zone is the range of the constant power zone that does not belong to the third, fourth, fifth, sixth, and eighth zones, that is, the remaining area of ​​the constant power zone is the seventh zone. P ,T P )Meet the conditions:

[0180]

[0181] Then point P(n P ,T P ) belongs to the seventh zone high speed overload zone, that is:

[0182]

[0183] See also Fig. 20 , the 6 sub-areas of the constant power area are shown in the figure with different marks. The right oblique line area is the high-speed low-load area of ​​the third area, the dark gray area is the high-speed high-efficiency area of ​​the fourth area, the oblique grid area is the high-speed load area of ​​the fifth area, the white area is the double high-efficiency area of ​​the sixth area, the dot area is the high-speed overload area of ​​the seventh area, and the light gray area is the high-speed weak magnetic area of ​​the eighth area.

[0184] Step 7: Based on the partition results of the constant power zone in step 6, determine the control method of the high-speed low-load zone in the third zone. Since the torque of the high-speed low-load zone in the third zone is lower than that in the fifth zone, the sixth zone and the seventh zone, and the speed is also lower than that in the eighth zone, for any point P3(n p3 ,T p3 ), n p3 and T p3 They are the speed and torque of any point in the high-speed and low-load zone of the third zone, and only one of the first power electronic switch and the second power electronic switch is closed while all the winding electronic switches are closed. In addition, the main control principle of the high-speed and low-load zone of the third zone is the principle of maximum system efficiency, which is to use the method of motor power increase operation, that is, without changing the motor speed, while increasing the output torque, the motor runs at the power increase operation point H3 (n H3 ,T H3), the excess energy is fed back to the battery, thereby improving the efficiency of the motor system. For any point P3(n p3 ,T p3 ), the control method is determined by the following steps:

[0185] Step 7.1: Calculate any point P3(n p3 ,T p3 ) The system consumes a total power of W3. When the motor runs at point P3 (n p3 ,T p3 ), its efficiency is η p3 , then point P3(n p3 ,T p3 ) The total power consumption of the system W3 is the product of the speed and torque divided by 2π times the value of 60 efficiency, that is:

[0186]

[0187] Step 7.2: Simultaneously with step 7.1, calculate the transition point P3'(n p3 ,T p3’ ) The total power consumed by the system is W3', the transition point P3'(n p3 ,T p3’ ) is point P3(n p3 ,T p3 ) any point with the same speed. When the motor runs at the transition point P3'(n p3’ ,T p3’ ), its efficiency is η p3’ , the power generation efficiency is η pg , then the transition point P3'(n p3’ ,T p3’ ) The total power consumed by the system is the power consumed by the motor at this time minus the efficiency of the power fed back to the battery, that is:

[0188]

[0189] Step 7.3: Based on steps 7.1 and 7.2, establish a mathematical model for power-up operation. The mathematical model for power-up operation is the total power consumption W3' of the system at the transition point P3' minus the total power consumption W3 of the system at the P3 point, which is:

[0190]

[0191] Step 7.4: Based on step 7.3, determine the set S P3 . Let the mathematical model of power-up operation be greater than 0, then from the above formula The following formula can be obtained:

[0192]

[0193] Then all conditions that meet The transition point P3'(n p3 ,T p3’ ) is a set S P3 .

[0194] It should be noted that for some points P3(n p3 ,T p3 ), S P3 It may be an empty set, which mainly depends on the motor power and specific performance of the motor. P3 When it is an empty set, the motor power increase operation method is not adopted, but direct operation is performed.

[0195] Step 7.5: Based on step 7.4, in S P3 It may be a non-empty set. When the motor is running at increased power, further in the set S P3 The power increase operation point H3(n H3 ,T H3 ).

[0196] In order to maximize the efficiency of the motor system within the normal operating range of the motor unit 1, the power operation point H3 (n H3 ,T H3 ) needs to belong to S P3 At the same time, it needs to belong to the third zone high speed low load zone or the fourth zone high speed high efficiency zone, and it also needs to meet the torque T of the power increase operation point H3. H3 Greater than or equal to T P3 That is to say, the power-up operation point H3 (n H3 ,T H3 ) needs to meet:

[0197]

[0198] It should be noted that if S P3 There exists a point H3(n H3 ,T H3 ) is not unique, then take the maximum value of the power increase mathematical model function f(T p3' )point.

[0199] Step 7.6: Use finite element software to simulate and obtain the motor running at point H3 (n H3 ,T H3 ) when the inverter outputs ABC three-phase current.

[0200] Step 8: At the same time as step 7, based on the partition result of step 6, determine the control method of the fourth zone high speed and high efficiency zone. Since the torque of the fourth zone high speed and high efficiency zone is lower than that of the fifth zone, the sixth zone and the seventh zone, and the speed is also lower than that of the eighth zone, for any point P4(n p4 ,T p4 ), only one of the first power electronic switch and the second power electronic switch is closed while all the winding electronic switches are closed. In addition, the main control principle of the fourth zone high speed and high efficiency zone is the principle of maximum system efficiency. Since the operating point efficiency of the fourth zone high speed and high efficiency zone is higher than that of the third zone, the fifth zone, the seventh zone and the eighth zone, the operating point P4 (n p4 ,T p4 ) works normally. Finite element software simulation is used to obtain the motor running at P4 (n p4 ,T p4 ) when the inverter outputs three-phase current ABC.

[0201] Step 9: At the same time as step 8, based on the partition result of step 6, determine the control method of the fifth zone high-speed load zone. Since the torque of the fifth zone high-speed load zone is higher than that of the third zone and the fourth zone, for any point P5(n p5 ,T p5 ), all power electronic switches are closed and all winding electronic switches are closed. In addition, the main control principle of the fifth zone high-speed load zone is the principle of maximum system efficiency. The main method is to use the method of motor power increase operation, that is, without changing the motor speed, increase the output torque, and the motor runs at the power increase operation point H5 (n H5 ,T H5 ) excess energy is fed back to the battery, thereby improving the efficiency of the motor system. For any point P5(n p5 ,T p5 ), the control method is the following steps:

[0202] Step 9.1: Calculate point P5(n p5 ,T p5 ) The system consumes a total power of W5. When the motor runs at point P5 (n p5 ,T p5 ), the efficiency is η p5 , then point P5(n p5 ,T p5 ) The total power consumed by the system W5 is the speed n p5 and torque T p5 The product of the two is divided by 60, which is 2π times the efficiency value, that is:

[0203]

[0204] Step 9.2: Simultaneously with step 9.1, calculate the transition point P5'(n p5 ,T p5’ ) The total power consumed by the system is W5', and the transition point is P5'(n p5 ,T p5’ ) is point P5(n p5 ,T p5 ) any point with the same speed. When the motor runs at point P5'(n p5 ,T p5’ ), its efficiency is η p5 , then the transition point P5'(n p5 ,T p5’ ) The total power consumed by the system is the power consumed by the motor at this time minus the efficiency of the power fed back to the battery, that is:

[0205]

[0206] Step 9.3: Based on steps 9.1 and 9.2, establish a mathematical model for power-up operation. The mathematical model for power-up operation is the total power consumption W5' of the system at the transition point P5' minus the total power consumption W5 of the system at the P5 point, which is:

[0207]

[0208] Step 9.4: Based on step 9.3, determine the set S P5 . Let the mathematical model f(T p5' ) is greater than 0, the following formula is obtained:

[0209]

[0210] Transition point P5'(n p5 ,T p5’ ) should satisfy the above conditions, and the transition point P5'(n p5 ,T p5’ ) forms a set S P5 It should be noted that for some points P5(n p5 ,T p5 ), S P5 It may be an empty set, which mainly depends on the motor power and specific performance of the motor. P5 When it is an empty set, the fifth zone high-speed load zone does not use the motor power increase operation method, but runs directly.

[0211] Step 9.5: When the set S P5 For a non-empty set, when the motor is running at increased power, in the set S P5 The power increase operation point H5(n H5 ,T H5In order to maximize the efficiency of the motor system within the normal operating range of the motor unit, the power operation point H5 (n H5 ,T H5 ) needs to belong to S P5 At the same time, it needs to belong to the fifth zone high-speed load zone or the sixth zone double high efficiency zone. In addition, it needs to meet T H5 Greater than or equal to T P5 That is to say, the power-up operation point H5 (n H5 ,T H5 ) needs to meet:

[0212]

[0213] It should be noted that if the set S P5 There is a point H5(n H5 ,T H5 ) is not unique, then take the power increase mathematical model function f(T p5' ) maximum point.

[0214] Step 9.6: Based on the results in step 9.5, the finite element software is used to simulate the motor running at point H5 (n H5 ,T H5 ) when the inverter outputs three-phase current ABC.

[0215] Step 10: At the same time as step 9, based on the partition result of step 6, determine the control method of the sixth zone double high efficiency zone. Since the torque of the sixth zone double high efficiency zone is higher than that of the third zone, the fourth zone and the fifth zone, for any point P6(n p6 ,T p6 ), all power electronic switches are closed and all winding electronic switches are closed. In addition, the main control principle of the sixth zone double high efficiency zone is the principle of maximum system efficiency. Since the operating point efficiency of the sixth zone double high efficiency zone is higher than that of the third zone, the fifth zone, the seventh zone and the eighth zone, the operating point P6 (n p6 ,T p6 ) works normally. Finite element software simulation is used to obtain the motor running at P6 (n p6 ,T p6 ) when the inverter outputs ABC current, and the inverter output is controlled by the DSP controller.

[0216] Step 11: At the same time as step 10, based on the partition result of step 6, determine the control method of the seventh zone high speed overload zone. Since the torque of the seventh zone high speed overload zone is higher than that of the third zone, the fourth zone and the fifth zone, for any operating point P7 (n p7 ,T p7), all power electronic switches are closed and all winding electronic switches are closed. In addition, the main control principle of the seventh zone high-speed overload zone is the principle of maximum system efficiency. Therefore, the seventh zone control strategy is the coordinated work of two control modules, that is, the current output by the first inverter and the second inverter is different, and the two N / 2 motor units 1 work at two operating points. Then the first control module makes the motor work at point P 71 (n p71 ,T p71 ); The second control module makes the motor work at point P 72 (n p72 ,T p72 ). For any point P7(n p7 ,T p7 ), the control method is the following steps:

[0217] Step 11.1: Establish the coordinated operation power function. There are two different points in the seventh zone high speed overload zone, namely the first transition point P 71 '(n p71’ ,T p71’ ) and the second transition point P 72 '(n p72’ ,T p72’ ), the speeds of the two transition points are both the same as the seventh zone operation point P7 (n p7 ,T p7 ) are equal and the sum of the torques is T P7 ,Right now:

[0218]

[0219] The set of transition points that meet the conditions is denoted as S P7 .

[0220] The first transition point P 71 '(n p71’ ,T p71’ )Total system power consumption W 71’ is the speed n p71’ and torque T p71’ The product of the two is divided by 60, which is 2π times the efficiency value, that is:

[0221]

[0222] Similarly, the second transition point P 72 '(n p72’ ,T p72’ )Total system power consumption W 72’ It is the product of speed and torque divided by 2π times the value of 60 efficiency, that is:

[0223]

[0224] The coordinated operation power function is the first transition point P 71 '(n p71’ ,T p71’ )Total system power consumption W 71’ With the second transition point P 72 '(n p72’ ,T p72’ )Total system power consumption W 72’ The sum is:

[0225]

[0226] Step 11.2: Based on the cooperative operation power function W7(T p71 ',T p72 '), determine two operating points P 71 (n p71 ,T p71 ) and P 72 (n p72 ,T p72 ).

[0227] The first operating point P 71 (n p71 ,T p71 ) The total power consumed by the system is W 71 , the second operating point P 72 (n p72 ,T p72 ) The total power consumed by the system is W 72 , then the two operating points P 71 (n p71 ,T p71 ) and P 72 (n p72 ,T p72 )'s coordinated operation power function W7(T p71 ,T p72 )=W 71 +W 72 , when the two operating points meet their coordinated operating power function W7(T p71 ,T p72 ) is equal to the two transition points P 71 '(n p71 ',T p71 ') and P 72 '(n p72 ',T p72 ') of the coordinated operation power function W7(T p71 ',T p72 ') is the minimum value, the motor operates at these two operating points P 71 (n p71 ,Tp71 ) and P 72 (n p72 ,T p72 ), operating point P 71 (n p71 ,T p71 ) and P 72 (n p72 ,T p72 ) are controlled and operated by the first control module and the second control module respectively.

[0228] Step 11.3: Based on the point P determined in step 11.2 71 (n p71 ,T p71 ), determine the output current of the first inverter. At this time, when all the winding electronic switches are closed, only the first power electronic switch is closed, and the output current of the first inverter is obtained by finite element software simulation.

[0229] At the same time, the current output by the second inverter is determined. At this time, when all the winding electronic switches are closed, only the second power electronic switch is closed, and the output current of the second inverter is obtained by finite element software simulation.

[0230] Step 12: At the same time as step 11, based on the partitioning result of step 6, determine the control strategy of the eighth zone high-speed weak magnetic zone. Since the speed of the eighth zone high-speed weak magnetic zone is higher than that of all other sub-zones, for any point P8 (n p8 ,T p8 ), all power electronic switches are closed and all winding electronic switches are closed, and the finite element software is used to simulate the motor running at P8 (n p8 ,T p8 ) when the inverter output current.

[0231] In summary, the motor is divided into 8 working modes according to the characteristics of the sub-regions:

[0232] 1. When the motor is running in the first zone low-speed load zone, the first power electronic switch and the second power electronic switch are both closed, and K switches are arbitrarily closed from the first winding electronic switch to the N / 2 power electronic switch, and K switches are arbitrarily closed from the (N / 2+1)th winding electronic switch to the Nth power electronic switch. The two inverters output currents with the same frequency, amplitude and different phases, and the motor units 1 of the two parts work at the same operating point. The torque waveform trough is compensated, which greatly reduces the torque pulsation of the motor in this sub-area and improves the torque quality.

[0233] 2. When the motor runs in the second zone, the low-speed overload zone, all power electronic switches and winding electronic switches are closed. The two inverters output currents with the same frequency, amplitude and phase. The motor units 1 of the two parts work at the same operating point. The torque output by the motor unit 1 is algebraically superimposed, which effectively increases the peak torque of the motor and enhances the torque output capacity of the motor.

[0234] 3. When the motor runs in the third zone, high speed and low load zone, only one of the first power electronic switch and the second power electronic switch is closed, and all winding electronic switches are closed. The motor unit runs at 1 liter power, which effectively improves the working efficiency of the motor and the operation efficiency of the whole machine.

[0235] 4. When the motor runs in the fourth zone, high speed and high efficiency zone, only one of the first power electronic switch and the second power electronic switch is closed, and all winding electronic switches are closed. N / 2 unit motors run normally, and the motor running efficiency is high at this time.

[0236] 5. When the motor runs in the fifth zone high-speed load zone, all power electronic switches are closed and all winding electronic switches are closed, and all motor units run at 1 liter power, which effectively improves the motor working efficiency and motor system operating efficiency.

[0237] 6. When the motor operates in the sixth zone, the double high efficiency zone, all power electronic switches are closed and all winding electronic switches are closed, all motor units 1 operate normally, and the motor operates with high efficiency.

[0238] 7. When the motor operates in the seventh double high efficiency zone, all power electronic switches are closed and all winding electronic switches are closed. Two inverters output current, the two parts of the motor unit 1 operate at different operating points, and the output torque is algebraically superimposed, which greatly improves the motor operation efficiency.

[0239] 8. When the motor runs in the eighth zone high-speed weak magnetic field zone, all power electronic switches are closed and all winding electronic switches are closed, all motor units 1 operate normally, and the motor runs at high speed.

[0240] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent methods or changes that do not deviate from the technical creation of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-pole and multi-slot unitized permanent magnet hub motor, characterized by: The invention comprises N identical motor units (1) uniformly distributed along the circumferential direction of the radial cross section, each motor unit (1) comprising 1 / N outer rotors (2), 1 / N inner stators (3) and 1 / N concentrated windings (4), the inner stators (3) being coaxially sleeved inside the outer rotor (2), the concentrated windings (4) being wound on the inner stators (3), the concentrated windings (4) in each motor unit (1) being three-phase symmetrical and uniformly distributed; the outer rotor (2) having a rotor core (2.3), 2a permanent magnet steel groups (2.4) uniformly distributed along the circumferential direction on the rotor core (2.3), each permanent magnet steel group (2.4) comprising first and second rectangular permanent magnet steels (2.4.1, 2.4.2) and arc-shaped permanent magnet steels (2.4.3), the first and second rectangular permanent magnet steels (2.4.1, 2.4.2) and arc-shaped permanent magnet steels (2.4.3), the first and second rectangular permanent magnet steels (2.4.1, 2.4.2) and arc-shaped permanent magnet steels (2.4.3) being uniformly distributed along the circumferential direction on the rotor core (2 ... The rectangular permanent magnets (2.4.1 and 2.4.2) have the same structure and the radial cross-sections are both rectangular, the inner and outer oblique directions are the length direction of the rectangle, and they are arranged in a V-shape with the opening facing the air gap side on the outside of the arc-shaped permanent magnet (2.4.3), symmetrical with respect to the center line of the arc-shaped permanent magnet (2.4.3) along the diameter direction; the magnetizing directions of the first and second rectangular permanent magnets (2.4.1 and 2.4.2) are perpendicular to their own length directions, the magnetizing direction of the arc-shaped permanent magnet (2.4.3) is consistent with the center line direction, the magnetizing directions of the first and second rectangular permanent magnets (2.4.1 and 2.4.2) and the arc-shaped permanent magnet (2.4.3) belonging to the same permanent magnet group (2.4) are simultaneously directed to or away from the air gap, and the magnetizing directions of two adjacent permanent magnet groups (2.4) are opposite; the number of rotor pole pairs P r 、Number of stator slots s , the number of motor phases m, the motor slot angle τ and N must all satisfy: P r >N s , P r =Na, N s =mNb, cτ=d*2π、 N=2i, i, a, b, c, d, e are all positive integers.

2. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 1 is characterized by: Each of the 1 / N outer rotors (2) is divided into M identical rotor segments along the axial direction, and the M rotor segments are arranged in sequence by rotating a mechanical offset angle along the same rotation direction, 20 mm ≤ l ef / M≤120mm,l ef is the axial length of the motor.

3. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 2 is characterized by: The method for determining a mechanical misalignment angle is: Step 1): first assign the initial mechanical misalignment angle to 0; Step 2): Simulate the torque waveform output by the motor and calculate the initial torque pulsation; Step 3): Perform Fourier decomposition of the torque waveform, obtain the harmonic order k of the highest amplitude harmonic component, and calculate the transition mechanical misalignment angle Then simulate the torque waveform at the transition mechanical misalignment angle α1 and calculate the transition torque pulsation; Step 4): Compare the transition torque pulsation with the initial torque pulsation. If the transition torque pulsation is smaller than the initial torque pulsation, the transition mechanical misalignment angle α1 is a mechanical misalignment angle of the rotor segment rotation. Otherwise, the transition mechanical misalignment angle α1 is assigned to the initial mechanical misalignment angle and steps 2)-3) are repeated.

4. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 1 is characterized by: Each arc-shaped permanent magnet (2.4.3) is surrounded by an arc-shaped permanent magnet outer long side (2.4.3.1), an arc-shaped permanent magnet inner long side (2.4.3.2) and two arc-shaped permanent magnet short sides (2.4.3.3) on the radial cross section. The arc center of the arc-shaped permanent magnet outer long side (2.4.3.1) and the arc-shaped permanent magnet inner long side (2.4.3.2) is the same as the center of the outer rotor (2). The diameter direction of the arc-shaped permanent magnet short side (2.4.3.3) and the outer rotor (2) is consistent. The inner long side (2.4.3.2) of the arc-shaped permanent magnet is a sine curve f1(θ1)=f 1max sin(θ1),θ1∈[π,2π],f 1max is the amplitude, when θ1 is 3π / 2, point f1(3π / 2) is located on the inner surface of the outer rotor (2).

5. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 4 is characterized by: Each of the first and second rectangular permanent magnetic steels (2.4.1, 2.4.2) is provided with an inner magnetic barrier (2.5) at the end close to the air gap side, and an outer magnetic barrier (2.6) at the end away from the air gap side, and each arc-shaped permanent magnetic steel (2.4.3) is provided with a virtual slot (2.7) forming part of the air gap at both tangential ends.

6. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 5 is characterized by: The radial cross section of the inner magnetic barrier (2.5) is a pentagon, the first side of the pentagon is an extension of the long side of the first and second rectangular permanent magnets (2.4.1, 2.4.2) close to the air gap, the second side is an arc side coaxial with the outer rotor (2), the third side is located on the radius of the outer rotor (2), the fourth side is parallel to the first side and located outside the first side, the distance between the first side and the fourth side is less than the width of the first and second rectangular permanent magnets (2.4.1, 2.4.2), and the fifth side coincides with the short side of the first and second rectangular permanent magnets (2.4.1, 2.4.2) close to the air gap.

7. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 5 is characterized by: The radial cross section of the external magnetic barrier (2.6) is a pentagon, the first side of the pentagon is the extension line of the long side of the first and second rectangular permanent magnets (2.4.1, 2.4.2) close to the air gap, the second side is located on the radius of the outer rotor (2), the third side is an arc side coaxial with the outer rotor (2), the fourth side is parallel to the first side and is located outside the first side, the distance between the first side and the fourth side is less than the width of the first and second rectangular permanent magnets (2.4.1, 2.4.2), and the fifth side coincides with the short sides of the first and second rectangular permanent magnets (2.4.1, 2.4.2) away from the air gap.

8. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 6 is characterized by: The virtual groove (2.7) is a sine curve f2(θ2)=f 2max sin(θ2), θ2 is [π / 2,π], f2max is the amplitude, when θ2 is π / 2, point f2(π / 2) is the intersection of the inner long side (2.4.3.2) of the arc-shaped permanent magnet and the short side (2.4.3.3) of the arc-shaped permanent magnet, when θ2 is π, point f2(π) is the intersection of a radius passing through the intersection of the second side and the third side of the inner magnetic barrier (2.5) and the inner surface of the outer rotor (2).

9. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 1, characterized in that: The first and second rectangular permanent magnets (2.4.1, 2.4.2) form a V-shaped angle β pm Satisfy: 40°≤β pm ≤65°, long side length w pm With wide side length h pm Satisfies: 2≤w pm / h pm ≤4.

10. The multi-pole and few-slot unitized permanent magnet hub motor according to claim 1, characterized in that: The minimum width h of the arc-shaped permanent magnet steel 2.4.3 in the radial direction is pmin With maximum width h pmax Satisfy: 1.5 ≤ h pmax / h pmin ≤2.

11. A coordinated control system of a multi-pole and few-slot unitized permanent magnet hub motor as claimed in claim 1, characterized in that: The invention comprises a battery, two control modules and N winding electronic switches. One winding electronic switch controls the on and off of a concentrated winding (4) in a motor unit (1). Each control module is composed of a power electronic switch, a DSP controller and an inverter connected in series in sequence. The input ends of the two power electronic switches are respectively connected to the output ends of the battery. The output end of each inverter is respectively connected to N / 2 winding electronic switches. The output end of the concentrated winding (4) is connected to the battery via a rectifier.

12. A control method of a cooperative control system according to claim 11, characterized in that The following steps are involved: Step 1): close two power electronic switches and N winding electronic switches, take the horizontal axis as the motor speed and the vertical axis as the motor output torque, and simulate to obtain the external characteristic curve g of the motor; Then disconnect one of the power electronic switches and simulate to obtain the external characteristic curve f of the motor; the highest speed corresponding to the highest torque on the external characteristic curve f is taken as the critical speed n b , when the motor running point speed n p ≤n b , is the constant torque area; Step 2): Divide the constant torque area into a first area and a second area. When the torque T p ≤T b , is the first zone, when T p >T b , for the second zone, T b is the critical torque T b , is a motor unit (1) peak torque T x N-2 times; the maximum value of the torque at the operating point in the second zone does not exceed the torque corresponding to the external characteristic curve g; Step 3): When the operating point is in the first zone, both power electronic switches are closed, and at least one of the N / 2 motor units (1) connected to each control module is closed. Winding electronic switch, T p1 is the torque of the operating point in the first zone; the two inverters output currents of the same amplitude but different phases; when the operating point is in the second zone, the two power electronic switches and the N winding electronic switches are all closed.

13. The control method according to claim 12, characterized in that: In step 3), the motor output torque waveform and the transition current output by the two inverters are simulated and calculated when the K windings are electronically switched, the output torque waveform is Fourier decomposed, the harmonic order r of the main harmonic component is obtained, and the current misalignment angle is calculated. The three-phase current amplitudes I of the outputs of the two inverters are max =1.05I max0 , I max0 is the transition current amplitude, the three-phase current phase output by the first inverter leads the transition current phase by β / 2, and the three-phase current phase output by the second inverter lags the transition current phase by β / 2.

14. A control method of a cooperative control system according to claim 11, characterized in that The following steps are involved: Step (I): close two power electronic switches and N winding electronic switches, take the horizontal axis as the motor speed and the vertical axis as the motor output torque, and simulate to obtain the external characteristic curve g of the motor; Then disconnect one of the power electronic switches and simulate to obtain the external characteristic curve f of the motor; the highest speed corresponding to the highest torque on the external characteristic curve f is taken as the critical speed n b , when the motor running speed n p >n b , is the constant power area; Step (II): Divide the constant power area into the third to eighth areas, when the efficiency η of the operating point p≥ η b , then it is the fourth zone, η b is the boundary efficiency of the motor when a single control module is running; the area surrounded by the abscissa axis, the external characteristic curve g and a straight line j perpendicular to the abscissa passing through the highest speed point E in the fourth zone is the eighth zone; the area where the torque is less than the torque of the lowest speed point D in the fourth zone and the speed is less than the speed of point D is the zone S 31 The area enclosed by the abscissa, a straight line k passing through point D and perpendicular to the abscissa, the fourth zone point D, the lower half boundary line of E, and the straight line j is area S. 32 , S 31 With S 32 The union of is the third zone; the zone with the same speed as the fourth zone and twice the torque of the fourth zone is the sixth zone, the highest speed point G of the sixth zone is on the straight line j, and the lowest speed point F is on the straight line k; the zone with a torque less than the torque at point F, a torque higher than point D, and a speed less than the speed at point F is zone S 51 The area enclosed by straight line k, straight line j, the upper half boundary of the fourth zone point D and E, and the lower half boundary of the sixth zone point F and G is area S. 52 , S 51 With S 52 The union of is the fifth zone; the remaining area in the constant power zone is the seventh zone; Step (III): when the operating point is in the third zone, only one of the two power electronic switches is closed, the N winding electronic switches are all closed, and the motor speed is not changed while the torque is increased. When the operating point is in the fourth zone, only one of the two power electronic switches is closed, and the N winding electronic switches are all closed; When the operating point is in the fifth zone, both power electronic switches are closed, N winding electronic switches are closed and the power is increased; when the operating point is in the sixth zone, both power electronic switches are closed, N winding electronic switches are closed; When the operating point is in the seventh zone, both power electronic switches are closed, N winding electronic switches are closed, and the currents output by the two inverters are different; When the operating point is in the eighth zone, both power electronic switches are closed and the N winding electronic switches are closed.

15. The control method according to claim 14, characterized in that: The power increase operation of the third zone in step (III) is: p3 ,T p3 ) Transition point P3'(n p3 ,T p3’ ), when the condition is met When forming a set S P3 , set S P3 The third or fourth zone and the torque is greater than or equal to T P3 The operating point is the power-up operating point H3 (n H3 ,T H3 ), the simulation obtains that the motor runs at the power increase point H3(n H3 ,T H3 ) when the inverter outputs three-phase current, feeding the excess energy back to the battery; The power-up operation in the fifth zone is similar to that in the third zone; p3 , T p3 and η p3 They are respectively the operating point P3(n p3 ,T p3 ) speed, torque and efficiency, T p3’ and η p3’ are the torque and efficiency at the transition point, η pg For power generation efficiency.

16. The control method according to claim 14, characterized in that: In step (III), in the seventh zone, there are two transition points with a rotational speed equal to the seventh zone operating point, and the sum of the torques of the two transition points is equal to the seventh zone operating point torque. The sum of the total power consumption of the system at the two transition points is calculated. When the sum of the total power consumption of the system at two operating points is equal to the minimum value of the sum of the total power consumption of the system at the two transition points, the two operating points are respectively controlled and operated by the corresponding two control modules.

17. The control method according to claim 16, characterized in that: When N winding electronic switches are closed and only the first power electronic switch is closed, the output current of the first inverter is obtained by simulation, and the first operating point of the two operating points is controlled; when N winding electronic switches are closed and only the second power electronic switch is closed, the output current of the second inverter is obtained by simulation, and the second operating point of the two operating points is controlled.

Images