Permanent magnet included angle optimization-based permanent magnet motor and cogging torque suppression method thereof

Abstract

The invention provides a permanent magnet motor based on permanent magnet included angle optimization and a cogging torque suppression method thereof.The permanent magnet motor comprises a stator iron core, an armature winding, rotor iron cores and permanent magnets, and each pole of rotor iron core is provided with two sets of first V-shaped permanent magnet grooves and second V-shaped permanent magnet grooves which are symmetrical about the center line of the rotor iron core and are different in size; the permanent magnets are arranged in the first V-shaped permanent magnet grooves and the second V-shaped permanent magnet grooves respectively, the permanent magnets in the first V-shaped permanent magnet grooves and the second V-shaped permanent magnet grooves are arranged in a V-V shape, the included angle between the permanent magnets in the first V-shaped permanent magnet grooves is alpha, the included angle between the permanent magnets in the second V-shaped permanent magnet grooves is beta, and the permanent magnets in the first V-shaped permanent magnet grooves and the permanent magnets in the second V-shaped permanent magnet grooves are separated by the aid of an NSGA-II algorithm under the condition that the distance of the magnetic isolation bridge is unchanged. By adjusting the angle between the permanent magnets in the first V-shaped permanent magnet grooves and the second V-shaped permanent magnet grooves, the best matching combination of the small permanent magnet included angle alpha and the large permanent magnet included angle beta is optimized, and the arc-shaped auxiliary grooves are formed in the surface of the rotor iron core, so that the cogging torque of the permanent magnet motor is optimized.

Description

Technical Field

[0001] The present invention belongs to the field of motor manufacturing and its application, and is applicable to a built-in permanent magnet synchronous motor with a VV rotor magnetic circuit structure, specifically a permanent magnet motor based on permanent magnet angle optimization and a cogging torque suppression method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry and strong national support, the public's performance requirements for electric vehicles are increasing. The core technology of new energy vehicles lies in the motor and its drive system, whose technical level directly determines the vehicle's performance and market positioning. In electric vehicles, the drive motor often adopts a variety of topologies, such as asynchronous motors, permanent magnet synchronous motors, and switched reluctance motors. Permanent magnet synchronous motors include surface-mount permanent magnet synchronous motors and interior permanent magnet synchronous motors. The interior permanent magnet synchronous motor has great development potential in the new energy vehicle field due to its high efficiency, high torque density, and wide speed range. However, due to its structural characteristics, cogging torque has always been a key factor limiting its performance. Therefore, reducing cogging torque in interior permanent magnet synchronous motors has become a research focus. Traditional optimization solutions focus on structural optimization design, such as slot skew and pole arc coefficient adjustment, or segmented or asymmetric permanent magnet arrangement. With the development of high-performance computing and optimization algorithms, multi-objective collaborative optimization (combining response surface methods and genetic algorithms) and new topologies (such as non-uniform air gap and auxiliary slot design) have become research hotspots. The placement, shape, and depth of auxiliary slots on the rotor surface can affect the motor's air gap flux density, leading to significant torque fluctuations. This paper addresses the cogging torque issue in interior permanent magnet synchronous motors (IPMS) by designing the rotor's permanent magnets and creating auxiliary slots on the rotor surface to reduce the cogging torque and enhance operational stability. Summary of the Invention

[0003] The present invention proposes a permanent magnet motor based on permanent magnet angle optimization and a cogging torque suppression method thereof, which is suitable for a built-in permanent magnet synchronous motor with a VV rotor magnetic circuit structure. While ensuring that the size of the magnetic isolation bridge remains unchanged, the angles of two pairs of permanent magnets of different sizes are adjusted and auxiliary slots are opened at appropriate positions on the rotor surface. The position, width and depth of the auxiliary slots are studied to reduce the distortion rate of the air gap magnetic field, reduce the back electromotive force harmonics, and further reduce the motor cogging torque.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A permanent magnet motor based on permanent magnet angle optimization includes a stator core, an armature winding, a rotor core, and permanent magnets. An air gap is provided between the stator core and the rotor core. The motor is characterized in that: each pole of the rotor core is provided with two groups of first V-shaped permanent magnet slots and second V-shaped permanent magnet slots of different sizes that are symmetrical about the center line of the rotor core. Permanent magnets are respectively placed in the first V-shaped permanent magnet slots and the second V-shaped permanent magnet slots. The permanent magnets in the first V-shaped permanent magnet slots and the second V-shaped permanent magnet slots form a V-shaped permanent magnet. V-shaped arrangement, the angle between the permanent magnets in the first V-shaped permanent magnet slot is the small permanent magnet angle, recorded as α, the angle between the permanent magnets in the second V-shaped permanent magnet slot is the large permanent magnet angle, recorded as β, while ensuring that the distance of the magnetic isolation bridge remains unchanged, by adjusting the angle between the permanent magnets in the first V-shaped permanent magnet slot and the second V-shaped permanent magnet slot, the best matching combination of the small permanent magnet angle α and the large permanent magnet angle β is optimized, and the surface of the rotor core is provided with an auxiliary slot, and the slot shape of the auxiliary slot is arc-shaped.

[0006] As a preferred technical solution of the present invention: the sizes of the magnetic isolation bridges between the first V-shaped permanent magnet slots, the magnetic isolation bridges between the second V-shaped permanent magnet slots, the magnetic isolation bridges from the first V-shaped permanent magnet slots to the surface of the rotor core, and the magnetic isolation bridges from the second V-shaped permanent magnet slots to the surface of the rotor core remain unchanged.

[0007] As a preferred technical solution of the present invention: the optimal angle of the small permanent magnet angle α is 136 degrees, and the optimal angle of the large permanent magnet angle β is 95 degrees.

[0008] As a preferred technical solution of the present invention: the auxiliary slots on the surface of the rotor core are evenly distributed, with two slots per pole, for a total of 16 slots, and the included angle γ of the midpoint of the auxiliary slots of each pole is 30 degrees.

[0009] As a preferred technical solution of the present invention: the auxiliary groove on the surface of the rotor core has a depth D of 0.37 mm and a width W of 11.4 mm.

[0010] As a preferred technical solution of the present invention: the stator core and the rotor core are both made of laminated silicon steel sheets.

[0011] As a preferred technical solution of the present invention: the stator core is provided with pear-shaped slots, and the armature windings wound around the teeth of the stator core are flat wire windings.

[0012] In the above structure, while maintaining the distance of the magnetic isolation bridge, the present invention adjusts the angles α and β between the two sets of permanent magnets in the interior permanent magnet motor to optimize the angle combination of the two sets of permanent magnets, namely, the angle of the small permanent magnet is 136 degrees and the angle of the large permanent magnet is 95 degrees, thereby reducing the cogging torque of the interior permanent magnet synchronous motor. Arc-shaped auxiliary slots are added to the rotor surface to make the motor's air gap non-uniform, thereby reducing the distortion rate of the air gap magnetic field and weakening the back-electromotive force harmonics. The cogging torque and torque ripple of the interior permanent magnet motor are optimized using the NSGA-II (non-dominated sorting genetic algorithm). Combined with Maxwell finite element simulation, the auxiliary slot depth (D) is determined to be 0.37 mm and the width (W) is determined to be 11.4 mm. The angle (γ) between the two auxiliary slots in each rotor pole is determined to be 30 degrees. This suppresses the motor's back-electromotive force harmonics and further reduces the motor's cogging torque without affecting the effective value of the motor's back-electromotive force.

[0013] A method for suppressing cogging torque of a permanent magnet motor based on optimization of the angle between permanent magnets is characterized by comprising the following steps:

[0014] S1. Initial plan:

[0015] The NSGA-II algorithm is used to optimize the cogging torque and torque ripple of the permanent magnet motor. Maxwell finite element simulation is used to determine the depth and width of the auxiliary slots, as well as the angle between the two auxiliary slots in each pole rotor, to suppress the back electromotive force harmonics of the permanent magnet motor.

[0016] S2. Motor cogging torque optimization:

[0017] The parameters and optimization range of the permanent magnet motor are selected. Without changing the size of the magnetic isolation bridge of the permanent magnet motor, a finite element simulation is performed on the permanent magnet motor within the selected range. First, the influence of the small permanent magnet angle on the motor cogging torque is determined. The small permanent magnet angle α is changed with the midpoint of the magnetic isolation bridge in the middle of the small permanent magnet as the center of the circle, so that the small permanent magnet angle range is from 110 degrees to 140 degrees. Similarly, the influence of the large permanent magnet angle β on the motor cogging torque is determined. The large permanent magnet angle range is from 80 degrees to 108 degrees. Based on the above optimization, finite element simulation is performed on the width W and depth D of the auxiliary slot on the surface of the rotor core of the permanent magnet motor and the angle γ of the midpoint of the auxiliary slot of each pole at different times.

[0018] S3. Modify the permanent magnet angle matching and auxiliary slot parameters:

[0019] Within the range of small permanent magnet angle and large permanent magnet angle, finite element simulation is performed after modifying the matching of small permanent magnet and large permanent magnet angle and the auxiliary slot parameters;

[0020] S4. Determination:

[0021] Perform finite element simulation, make a judgment after the simulation is completed, generate an error function, if the error value of the error function is less than the specified value, directly output the result, if the error value of the error function is greater than the specified value, continue optimization, and repeat step S4 after modifying the variable value;

[0022] S5. Output results

[0023] Through finite element simulation comparison, when the small permanent magnet angle α of the permanent magnet motor is 136 degrees, the large permanent magnet angle β is 95 degrees, the arc-shaped auxiliary slot width W is 11.4mm, the depth D is 0.37mm, and the auxiliary slot midpoint angle γ is 30 degrees, the motor slot torque is minimum, and the slot torque fluctuation amplitude decreases by 63% from the original 1.2Nm to the optimized 440mNm.

[0024] As a preferred technical solution of the present invention: in step S2, when performing finite element simulation on the auxiliary slot on the surface of the rotor core in the permanent magnet motor, the position of the auxiliary slot is first determined, and then the depth and width of the auxiliary slot are simulated. By comparing the influence of different factors on the change of the motor cogging torque, the optimal motor cogging torque optimization solution is determined.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention is applicable to interior permanent magnet synchronous motors with a VV rotor magnetic circuit structure. While ensuring the size of the magnetic isolation bridge remains unchanged, the present invention adjusts the V-shaped angles of the two pairs of permanent magnets in the rotor magnetic circuit of the interior permanent magnet synchronous motor to achieve an optimal matching angle between the two pairs of permanent magnets. Auxiliary slots are also provided on the rotor surface to reduce the cogging torque of the interior permanent magnet synchronous motor and weaken the harmonics of the back electromotive force. Compared with the prior art, the present invention has the following advantages:

[0027] 1. The motor no-load back electromotive force waveform is improved, the harmonic content is reduced, and the waveform distortion rate is reduced.

[0028] 2. The motor's cogging torque is more significantly weakened, and the motor torque pulsation is also greatly reduced, making the motor operation more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the transverse cross-sectional structure of the built-in permanent magnet motor of the present invention;

[0030] Figure 2 A partially enlarged view of the built-in permanent magnet motor of the present invention;

[0031] Figure 3 This is an enlarged view of the auxiliary slots on the surface of the rotor core in the present invention;

[0032] Figure 4Flowchart for motor cogging torque optimization;

[0033] Figure 5 Comparison of the no-load cogging torque waveforms of the interior permanent magnet motor before and after optimization;

[0034] Figure 6 The figure shows the comparison of the output torque waveforms of the built-in permanent magnet motor under rated load conditions before and after optimization.

[0035] Description of reference numerals:

[0036] 1. Stator core; 2. Armature winding; 3. Rotor core; 4. Permanent magnet; 5. Auxiliary slot. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0038] like Figure 1-3 As shown, the permanent magnet motor based on the optimization of the permanent magnet angle proposed in the present invention comprises a stator core 1, an armature winding 2, a rotor core 3 and a permanent magnet 4. An air gap is provided between the stator core 1 and the rotor core 3. Two groups of first V-shaped permanent magnet slots and second V-shaped permanent magnet slots of different sizes are opened on each pole of the rotor core 3, which are symmetrical about the center line of the rotor core 3. The first V-shaped permanent magnet slot and the second V-shaped permanent magnet slot are respectively placed with permanent magnets 4. The permanent magnets in the first V-shaped permanent magnet slot and the second V-shaped permanent magnet slot are respectively placed with permanent magnets 4. The rotor core 3 has a first V-shaped permanent magnet slot and a second V-shaped permanent magnet slot, wherein the angle between the permanent magnets 4 is a small permanent magnet angle, denoted as α; the angle between the permanent magnets 4 in the second V-shaped permanent magnet slot is a large permanent magnet angle, denoted as β; while ensuring that the distance of the magnetic isolation bridge remains unchanged, the angle between the permanent magnets 4 in the first V-shaped permanent magnet slot and the second V-shaped permanent magnet slot is adjusted to optimize the combination of the small permanent magnet angle α and the large permanent magnet angle β; an auxiliary slot 5 is provided on the surface of the rotor core 3, and the slot shape of the auxiliary slot 5 is arc-shaped.

[0039] The sizes of the magnetic isolation bridges between the first V-shaped permanent magnet slots, the magnetic isolation bridges between the second V-shaped permanent magnet slots, the magnetic isolation bridges from the first V-shaped permanent magnet slots to the surface of the rotor core 3, and the magnetic isolation bridges from the second V-shaped permanent magnet slots to the surface of the rotor core 3 are all unchanged.

[0040] The optimal angle of the small permanent magnet included angle α is 136 degrees, and the optimal angle of the large permanent magnet included angle β is 95 degrees.

[0041] The auxiliary slots 5 on the surface of the rotor core 3 are evenly distributed, with two slots per pole, for a total of 16 slots. The included angle γ of the midpoint of the auxiliary slot 5 at each pole is 30 degrees.

[0042] The auxiliary groove 5 on the surface of the rotor core 3 has a depth D of 0.37 mm and a width W of 11.4 mm.

[0043] The stator core 1 and the rotor core 3 are both formed by laminating silicon steel sheets.

[0044] The stator core 1 is provided with pear-shaped slots, and the armature winding 2 wound around the teeth of the stator core 1 is a flat wire winding.

[0045] While maintaining the distance of the magnetic isolation bridge, this invention optimizes the angles α and β between the two sets of permanent magnets 4 in an interior permanent magnet synchronous motor (IPMS) to achieve the optimal matching of the two sets of permanent magnet angles: a 136-degree angle for the small permanent magnet and a 95-degree angle for the large permanent magnet. This reduces the cogging torque of the IPMSM. Arc-shaped auxiliary slots 5 are created on the rotor's inner surface to create a non-uniform air gap, thereby reducing the distortion of the air gap magnetic field and weakening back-electromotive force harmonics. The cogging torque and torque ripple of the IPMSM were optimized using the NSGA-II (non-dominated sorting genetic algorithm). Combined with Maxwell finite element simulation, the depth (D) and width (W) of the auxiliary slots 5 were determined to be 0.37 mm and 11.4 mm, respectively. The midpoint angle (γ) between the two auxiliary slots 5 in each rotor pole was set to 30°. This suppresses the motor's back-electromotive force harmonics and further reduces the motor's cogging torque without affecting the effective back-electromotive force value.

[0046] like Figure 4-6 As shown, the method for suppressing the cogging torque of a permanent magnet motor based on the optimization of the permanent magnet angle proposed in the present invention includes the following steps:

[0047] S1. Initial plan:

[0048] The NSGA-II algorithm is used to optimize the cogging torque and torque ripple of the permanent magnet motor. Maxwell finite element simulation is used to determine the depth and width of the auxiliary slot 5, and the angle between the two auxiliary slots 5 in each pole rotor to suppress the back electromotive force harmonics of the permanent magnet motor.

[0049] S2. Motor cogging torque optimization:

[0050] Select the parameters and optimization range of the permanent magnet motor. Without changing the size of the magnetic isolation bridge of the permanent magnet motor, perform finite element simulation on the permanent magnet motor within the selected range. First, determine the influence of the small permanent magnet angle on the motor cogging torque. Change the small permanent magnet angle α with the midpoint of the magnetic isolation bridge in the middle of the small permanent magnet as the center of the circle, so that the small permanent magnet angle range is from 110 degrees to 140 degrees. Similarly, determine the influence of the large permanent magnet angle β on the motor cogging torque. The large permanent magnet angle range is from 80 degrees to 108 degrees. On the basis of the above optimization, perform finite element simulation on the width W, depth D and midpoint angle γ of the auxiliary slot 5 on the surface of the rotor core 3 of the permanent magnet motor. When performing finite element simulation on the auxiliary slot 5 on the surface of the rotor core 3 of the permanent magnet motor, first determine the position of the auxiliary slot 5, and then simulate the depth and width of the auxiliary slot 5. By comparing the influence of different factors on the change of the motor cogging torque, determine the optimal motor cogging torque optimization scheme;

[0051] S3. Modify the permanent magnet angle matching and auxiliary slot 5 parameters:

[0052] Within the range of the small permanent magnet angle and the large permanent magnet angle, the finite element simulation is performed after modifying the matching of the small permanent magnet and the large permanent magnet angle and the parameters of the auxiliary slot 5;

[0053] S4. Determination:

[0054] Perform finite element simulation, make a judgment after the simulation is completed, generate an error function, if the error value of the error function is less than the specified value, directly output the result, if the error value of the error function is greater than the specified value, continue optimization, and repeat step S4 after modifying the variable value;

[0055] S5. Output results

[0056] Through finite element simulation comparison, when the small permanent magnet angle α of the permanent magnet motor is 136 degrees, the large permanent magnet angle β is 95 degrees, the width W of the arc-shaped auxiliary slot 5 is 11.4 mm, the depth D is 0.37 mm, and the midpoint angle γ of the auxiliary slot 5 is 30 degrees, the motor cogging torque is minimum, and the cogging torque fluctuation amplitude decreases by 63% from the original 1.2 Nm to the optimized 440 mNm.

[0057] Example:

[0058] Taking a three-phase stator 72 slots / rotor 8-pole interior permanent magnet synchronous motor as an example, the technical solution of the present invention is specifically described.

[0059] The internal permanent magnet motor involved in this optimization solution has a small permanent magnet angle α of 118 degrees before optimization, a large permanent magnet angle β of 87 degrees, and the permanent magnets 4 are symmetrical about the center line of the rotor core 3 of each pole.

[0060] The NSGA-II algorithm (non-dominated sorting genetic algorithm) is one of the most widely used multi-objective optimization algorithms in the field of evolutionary computing. Its core idea is to introduce two key innovations based on traditional algorithms.

[0061] 1: Fast Non-dominated Sort

[0062] 1. The first frontier: not dominated by any individual;

[0063] 2. Second frontier: solutions dominated only by individuals on the first frontier

[0064] 3. And so on

[0065] 2. Crowing Distance Calculation

[0066] It is used to measure the density of surrounding solutions of cells in the same front and maintain the diversity of solutions.

[0067] The main steps of the NSGA-II algorithm (non-dominated sorting genetic algorithm) are as follows

[0068] 1. Parametric modeling of the motor and setting of constraints;

[0069] 2. Algorithm initialization and main optimization loop;

[0070] 3. Pareto frontier visualization;

[0071] 4. Select the best solution;

[0072] 5. Finite element verification;

[0073] The specific parameters of the interior permanent magnet synchronous motor with 72 stator poles and 8 rotor poles are shown in Table 1.

[0074] Basic parameters Numerical Basic parameters Numerical Stator outer diameter / mm 90 Rotor outer diameter / mm 67 Stator inner diameter / mm 67.5 Rotor inner diameter / mm 20 Number of stator teeth 72 Motor stack thickness / mm 90 Number of rotor poles 8 Rated power / kW 30 Air gap length / mm 0.5 Speed / rpm 3000

[0075] Table 1

[0076] Due to the limitations of the motor model, the large permanent magnet angle should be neither too large nor too small. If it is too large, the effective value of the back EMF will decrease, while if it is too small, the cogging torque ripple will increase. Although the small permanent magnet angle has a smaller impact on the effective value of the back EMF, a too small angle will increase the cogging torque ripple, while a too large angle will not ensure the magnetic isolation bridge distance and increase magnetic leakage. Therefore, it is necessary to continuously adjust the angle between the two sets of permanent magnets 4 to achieve the optimal match for the permanent magnet motor.

[0077] The selected permanent magnet motor parameters and optimization ranges are shown in Table 2. Without changing the size of the permanent magnet motor's magnetic isolation bridge, finite element simulations were performed on the same internal permanent magnet motor within the following ranges. First, the effect of the small permanent magnet angle on the motor's cogging torque was determined. The small permanent magnet angle α was modified, with the midpoint of the magnetic isolation bridge between the small permanent magnets as the center, so that the small permanent magnet angle ranged from 110 degrees to 140 degrees. Similarly, the effect of the large permanent magnet angle β on the motor's cogging torque was determined, with the large permanent magnet angle ranging from 80 degrees to 108 degrees. Based on this optimization, finite element simulations were performed with varying width (W), depth (D), and midpoint angle (γ) of the auxiliary slot 5 of the permanent magnet motor. Due to the influence of the position and shape of the permanent magnet slots 4 on the stator core 1, the angle between the midpoints of the auxiliary slots 5 is too small or too large, which will affect the size of the magnetic isolation bridge and thus affect the performance of the permanent magnet motor. Therefore, the position of the auxiliary slots 5 is first determined, and then the depth and width of the auxiliary slots 5 are simulated. By comparing the influence of different factors on the change of the cogging torque of the permanent magnet motor, the optimal motor cogging torque optimization scheme is determined.

[0078] Basic parameters Numerical range Small permanent magnet angle, (deg) 110-140 Large permanent magnet angle, (deg) 80-105 Auxiliary groove depth, (mm) 0.35-0.4 Auxiliary groove width, (mm) 10-11.8 Auxiliary slot midpoint angle, (deg) 26-32

[0079] Table 2

[0080] Through finite element simulation comparison, when the small permanent magnet angle α of the permanent magnet synchronous motor is 136 degrees, the large permanent magnet angle β is 95 degrees, the width (W) of the arc-shaped auxiliary slot 5 is 11.4mm, the depth (D) is 0.37mm, and the midpoint angle (γ) of the auxiliary slot 5 is 30 degrees, the motor cogging torque is minimum, and the cogging torque fluctuation amplitude decreases by 63% from the original 1.2Nm to the optimized 440mNm. At this time, the no-load cogging torque comparison of the motor before and after optimization is as follows: Figure 5 shown.

[0081] When the permanent magnet motor is loaded with rated load, it can be seen that the average output torque of the permanent magnet motor after optimization is reduced by 1.6% from the original 87.2Nm to 85.8Nm, which is slightly weakened compared with the original state, but the torque fluctuation is greatly improved. Figure 6 shown.

[0082] Therefore, the present invention proposes a permanent magnet motor and a method for suppressing cogging torque thereof based on the optimization of the permanent magnet angle, which optimizes the motor performance by adjusting the angle of the two pairs of permanent magnets 4 of the built-in permanent magnet synchronous motor. Compared with the previous single auxiliary slot 5, the effect of weakening the cogging torque of the motor is obvious, which helps to improve the motor efficiency and has good application prospects in the electric drive of electric vehicles.

[0083] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A permanent magnet motor based on permanent magnet angle optimization, comprising a stator core (1), an armature winding (2), a rotor core (3) and a permanent magnet (4), wherein an air gap is provided between the stator core (1) and the rotor core (3), and characterized in that: Two groups of first V-shaped permanent magnet slots and second V-shaped permanent magnet slots of different sizes symmetrical about the center line of the rotor core (3) are provided on each pole rotor core (3); permanent magnets (4) are respectively placed in the first V-shaped permanent magnet slots and the second V-shaped permanent magnet slots; the permanent magnets (4) in the first V-shaped permanent magnet slots and the second V-shaped permanent magnet slots are arranged in a VV shape; the angle between the permanent magnets (4) in the first V-shaped permanent magnet slots is a small permanent magnet angle, denoted as α; the angle between the permanent magnets (4) in the second V-shaped permanent magnet slots is a large permanent magnet angle, denoted as β; while ensuring that the distance of the magnetic isolation bridge remains unchanged, the angle between the permanent magnets (4) in the first V-shaped permanent magnet slots and the second V-shaped permanent magnet slots is adjusted to optimize the best matching combination of the small permanent magnet angle α and the large permanent magnet angle β; the surface of the rotor core (3) is provided with auxiliary slots (5); the slot shape of the auxiliary slots (5) is arc-shaped.

2. The permanent magnet motor based on permanent magnet angle optimization according to claim 1, characterized in that: The sizes of the magnetic isolation bridges between the first V-shaped permanent magnet slots, the magnetic isolation bridges between the second V-shaped permanent magnet slots, the magnetic isolation bridges from the first V-shaped permanent magnet slots to the surface of the rotor core (3), and the magnetic isolation bridges from the second V-shaped permanent magnet slots to the surface of the rotor core (3) are all unchanged.

3. The permanent magnet motor based on permanent magnet angle optimization according to claim 1, characterized in that: The optimal angle of the small permanent magnet included angle α is 136 degrees, and the optimal angle of the large permanent magnet included angle β is 95 degrees.

4. The permanent magnet motor based on permanent magnet angle optimization according to claim 1, characterized in that: The auxiliary slots (5) on the surface of the rotor core (3) are evenly distributed, with two slots provided on each pole, for a total of 16 slots, and an included angle γ of the midpoint of the auxiliary slot (5) on each pole is 30 degrees.

5. The permanent magnet motor based on permanent magnet angle optimization according to claim 4, characterized in that: The auxiliary groove (5) on the surface of the rotor core (3) has a depth D of 0.37 mm and a width W of 11.4 mm.

6. The permanent magnet motor based on permanent magnet angle optimization according to claim 1, characterized in that: The stator iron core (1) and the rotor iron core (3) are both formed by laminating silicon steel sheets.

7. The permanent magnet motor based on permanent magnet angle optimization according to claim 1, characterized in that: The stator core (1) is provided with pear-shaped slots, and the armature winding (2) wound around the teeth of the stator core (1) is a flat wire winding.

8. The method for suppressing cogging torque of a permanent magnet motor based on optimization of the permanent magnet angle according to any one of claims 1 to 7, characterized in that: The steps include: S1. Initial plan: The NSGA-II algorithm is used to optimize the cogging torque and torque ripple of the permanent magnet motor, and the depth, width, and midpoint angle of the auxiliary slots (5) and the two auxiliary slots (5) in each pole rotor are determined by Maxwell finite element simulation to suppress the back electromotive force harmonics of the permanent magnet motor. S2. Motor cogging torque optimization: The parameters and optimization range of the permanent magnet motor are selected. Without changing the size of the magnetic isolation bridge of the permanent magnet motor, the finite element simulation of the permanent magnet motor is performed within the selected range. First, the influence of the small permanent magnet angle on the motor cogging torque is determined. The small permanent magnet angle α is changed with the midpoint of the magnetic isolation bridge in the middle of the small permanent magnet as the center of the circle, so that the small permanent magnet angle range is from 110 degrees to 140 degrees. Similarly, the influence of the large permanent magnet angle β on the motor cogging torque is determined. The large permanent magnet angle range is from 80 degrees to 108 degrees. Based on the above optimization, the finite element simulation is performed on the auxiliary slot (5) on the surface of the rotor core (3) in the permanent magnet motor with different widths W and depths D and the midpoint angle γ of the auxiliary slot (5) per pole; S3. Modify the permanent magnet angle matching and auxiliary slot (5) parameters: Within the range of the small permanent magnet angle and the large permanent magnet angle, the matching of the small permanent magnet angle and the large permanent magnet angle and the parameters of the auxiliary slot (5) are modified and then a finite element simulation is performed; S4. Determination: Perform finite element simulation, make a judgment after the simulation is completed, generate an error function, if the error value of the error function is less than the specified value, directly output the result, if the error value of the error function is greater than the specified value, continue optimization, and repeat step S4 after modifying the variable value; S5. Output results Through finite element simulation comparison, when the small permanent magnet angle α of the permanent magnet motor is 136 degrees, the large permanent magnet angle β is 95 degrees, the width W of the arc-shaped auxiliary slot (5) is 11.4 mm, the depth D is 0.37 mm, and the midpoint angle γ of the auxiliary slot (5) is 30 degrees, the motor cogging torque is minimum at this time, and the cogging torque fluctuation amplitude decreases by 63% from the original 1.2 Nm to the optimized 440 mNm.

9. The method for suppressing cogging torque of a permanent magnet motor based on optimization of the permanent magnet angle according to claim 8, characterized in that: In step S2, when performing finite element simulation on the auxiliary slot (5) on the surface of the rotor core (3) in the permanent magnet motor, the position of the auxiliary slot (5) is first determined, and then the depth and width of the auxiliary slot (5) are simulated. By comparing the influence of different factors on the change of the motor cogging torque, the optimal motor cogging torque optimization scheme is determined.

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