A key electromagnetic force harmonic extraction method and system for an outer rotor permanent magnet synchronous motor

Abstract

The application discloses a key electromagnetic force wave harmonic extraction method and system of an outer rotor permanent magnet synchronous motor, and the method comprises the following steps: calculating the electromagnetic force density of the inner surface of the permanent magnet of the outer rotor permanent magnet synchronous motor; performing two-dimensional Fourier decomposition on the radial electromagnetic force and the tangential electromagnetic force respectively according to the obtained electromagnetic force density data; and obtaining the modal vibration mode data of the inner surface of the permanent magnet; performing one-dimensional Fourier decomposition on the radial modal vibration mode and the tangential modal vibration mode at each axial position respectively according to the obtained vibration mode data of each order modal; obtaining the modal vibration mode values at the response points; retaining the selected radial electromagnetic force harmonic; calculating the modal generalized force corresponding to the radial component and the tangential component of each order modal; calculating the complex domain vibration acceleration generated by the electromagnetic force harmonic, and the electromagnetic force harmonic with a larger vibration acceleration amplitude is the key harmonic. The electromagnetic force harmonic extracted by the method of the application is taken as an optimization target to guide the electromagnetic scheme design of the outer rotor motor and inhibit the vibration noise of the outer rotor permanent magnet synchronous motor.

Description

TECHNICAL FIELD

[0001] The application relates to a key electromagnetic force harmonic extraction method and system of an outer rotor permanent magnet synchronous motor, and belongs to the technical field of multi-harmonic optimization of an outer rotor permanent magnet synchronous motor. BACKGROUND

[0002] At present, an outer rotor permanent magnet synchronous motor is widely applied to many industrial occasions such as two-wheel electric hub motors, rotary-wing vertical take-off and landing aircrafts and robot joint modules due to advantages such as direct driving of a load, large torque density and compact structure. However, the outer rotor motor is usually accompanied by high-frequency whistling during operation, which directly affects the user-side use experience, and low electromagnetic vibration and noise performance design has become one of the core performance indicators of the outer rotor permanent magnet synchronous motor.

[0003] The electromagnetic force wave of the prior art is mainly based on an inner rotor structure permanent magnet synchronous motor, a two-dimensional or three-dimensional Fourier decomposition analysis method or a modal vibration mode analysis method is adopted, the time / space harmonic characteristics of the radial electromagnetic force wave of the inner rotor permanent magnet synchronous motor are analyzed, and then the main harmonic components of the electromagnetic force wave are determined according to the harmonic characteristics, the motor structure is optimized, and the electromagnetic noise is reduced. For example, the electromagnetic force wave analysis method based on three-dimensional Fourier decomposition is disclosed in CN 115996006A, the time, space axial and space tangential three-dimensional harmonic characteristics of the motor electromagnetic force are determined; the modal characteristic analysis method is disclosed in CN 115994445A, the two-dimensional modal vibration mode data of the spatial radial and axial multiple degrees of freedom of each modal vibration mode are Fourier decomposed, the modal displacement is converted from the spatial domain to the "wave number domain", and the amplitude and wave number are used for analyzing the electromagnetic force excited inner rotor permanent magnet synchronous motor vibration noise. The stator concentrated force method is disclosed in CN 113468786A, the concentrated force of each tooth surface is calculated by respectively calculating the concentrated force of each tooth surface through stator tooth surface area integration. The permanent magnet synchronous motor stator grid node electromagnetic force acquisition method is disclosed in CN 117875128A, the stator grid node time domain electromagnetic force at each speed point is obtained by reading the stator grid file.

[0004] However, for the outer rotor structure of the permanent magnet synchronous motor, the current mainstream scheme is the surface-mounted permanent magnet rotor topology. Since the permeability of the permanent magnet and the air gap of the motor are similar, the tangential electromagnetic force amplitude is large, and a large radial electromagnetic vibration can also be generated. In addition, the vibration amplitudes and phases generated by different electromagnetic force waves are not the same, and the vibration acceleration of the same frequency can be excited by multiple electromagnetic force waves at the same time. The existing electromagnetic force wave decomposition method mainly focuses on the radial electromagnetic force wave, and cannot extract the relationship between the vibration accelerations generated by the vibration of each order electromagnetic force. Therefore, a new key electromagnetic force harmonic extraction method for the outer rotor permanent magnet synchronous motor is proposed by combining the vibration acceleration generation mechanism of the outer rotor permanent magnet synchronous motor, so as to provide an electromagnetic force harmonic optimization target for the vibration and noise suppression of the outer rotor permanent magnet synchronous motor. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a key electromagnetic force harmonic extraction method for an outer rotor permanent magnet synchronous motor, to provide an electromagnetic force harmonic optimization target for low vibration and noise design of the outer rotor permanent magnet synchronous motor, and to further suppress the vibration and noise of the outer rotor permanent magnet synchronous motor.

[0006] To solve the above technical problems, the present application provides a key electromagnetic force wave harmonic extraction method for an outer rotor permanent magnet synchronous motor, comprising the following steps:

[0007] Step S1, calculating the electromagnetic force density of the inner surface of the permanent magnet of the outer rotor permanent magnet synchronous motor, wherein the electromagnetic force density data at least includes electromagnetic force density data of the inner surface of the permanent magnet in radial, circumferential and axial directions;

[0008] Step S2, performing two-dimensional Fourier decomposition on the radial and tangential electromagnetic forces respectively according to the obtained electromagnetic force density data, to obtain spatial order ε rp, , time order ξ rp , amplitude and phase of the radial electromagnetic force density; and

[0009] spatial order ε tp , time order ξ tp , amplitude and phase of the tangential electromagnetic force density;

[0010] Step S3, calculating the modal shape and frequency of each order of the rotor of the permanent magnet synchronous motor, and obtaining the modal shape data of the inner surface of the permanent magnet, wherein each modal shape data at least includes the modal shape value of the inner surface of the permanent magnet in radial, circumferential and axial directions;

[0011] Step S4, according to the obtained mode shape data of each order mode, one-dimensional Fourier decomposition is performed on the radial and tangential mode shapes at each axial position, respectively, to obtain the radial mode shape σ r corresponding to the amplitude of the sub-harmonic and phase , and the tangential mode shape σ t corresponding to the amplitude of the sub-harmonic and phase ;

[0012] Step S5, according to the coordinate values at the response position in the obtained mode shape data of the hth order mode, the mode shape values at the response point are obtained;

[0013] Step S6, according to the spatial order ε rp of the radial electromagnetic force density obtained in step 2 and the spatial order σ r of the radial component of the mode shape obtained in step 4, only the radial electromagnetic force harmonics with the spatial order ε rp equal to the spatial order σ r of the radial component of the mode shape are retained;

[0014] Similarly, according to the spatial order ε tp of the tangential electromagnetic force density obtained in step 2 and the spatial order σ t of the tangential component of the mode shape obtained in step 4, only the radial electromagnetic force harmonics with the spatial order ε tp equal to the spatial order σ t of the tangential component of the mode shape are retained;

[0015] Step S7, according to the harmonic amplitude and phase of the radial electromagnetic force density obtained in step 2, the harmonic amplitude and phase of the radial mode shape at each axial position, the modal generalized force corresponding to the radial component of each order mode is calculated ;

[0016] According to the harmonic amplitude and phase of the tangential electromagnetic force density obtained in step 2, the harmonic amplitude and phase of the tangential mode shape at each axial position, the modal generalized force corresponding to the tangential component of each order mode is calculated ;

[0017] Step S8, according to the modal generalized force corresponding to the radial electromagnetic force of each order mode, the mode shape value ϕ r at the response point, the modal generalized force corresponding to the radial component of each order mode is calculated h, angular frequency ω of electromagnetic force, h-order modal frequency ω h and damping ζ h , calculate the response point by (ε rp ,ξ rp )-order radial electromagnetic force harmonics generated by the complex domain vibration acceleration; similarly, calculate the (ε tp ,ξ tp ) order tangential electromagnetic force harmonic vibration acceleration;

[0018] Step S9: extracting key harmonics according to the vibration acceleration amplitudes generated by electromagnetic force harmonics of various orders. The electromagnetic force harmonics with larger vibration acceleration amplitudes are the key harmonics.

[0019] In the aforementioned method for extracting key electromagnetic force wave harmonics of an outer rotor permanent magnet synchronous motor, in step 1, electromagnetic finite element software is used to calculate the electromagnetic force density on the inner surface of the permanent magnet of the outer rotor permanent magnet synchronous motor.

[0020] In the aforementioned method for extracting key electromagnetic force wave harmonics of an outer rotor permanent magnet synchronous motor, in step 3, structural finite element software is used to calculate the modal vibration shapes and frequencies of each order of the motor rotor.

[0021] In the aforementioned method for extracting key electromagnetic force waves harmonics of an outer rotor permanent magnet synchronous motor, in step S7, the modal generalized force corresponding to the radial component of each order mode is calculated according to the following formula: ;

[0022]

[0023] Among them, R PM is the radius of the inner surface of the permanent magnet, L is the stack length of the motor, ω is the angular frequency of the electromagnetic force, ω r is the mechanical angular frequency, t is the time, and z is the axial position coordinate.

[0024] In the aforementioned method for extracting key electromagnetic force waves harmonics of an outer rotor permanent magnet synchronous motor, in step S7, the modal generalized force corresponding to the tangential component of each order mode is calculated according to the following formula: ;

[0025] .

[0026] In the aforementioned method for extracting key electromagnetic force waves harmonics of an outer rotor permanent magnet synchronous motor, in step S8, the following formula is used to calculate the harmonics of the response point (ε rp ,ξ rp )-order radial electromagnetic force harmonics generate complex domain vibration acceleration,

[0027]

[0028] Wherein, N is the highest modal order of the motor, i is the imaginary unit, and projection of the complex domain vibration acceleration to the real number coordinate axis is the actual vibration acceleration amplitude

[0029]

[0030] Wherein, Real is a real part function.

[0031] The key electromagnetic force wave harmonic extraction method of the aforementioned outer rotor permanent magnet synchronous motor calculates the vibration acceleration generated by the (epsilon tp ,xi tp ) order tangential electromagnetic force harmonic according to the following formula in step S8.

[0032]

[0033] .

[0034] A computer device / apparatus / system includes a memory, a processor, and a computer program stored on the memory, and the processor executes the computer program to implement the steps of the above method.

[0035] A computer readable storage medium has a computer program / instruction stored thereon, and the computer program / instruction is executed by a processor to implement the steps of the above method.

[0036] A computer program product includes a computer program / instruction, and the computer program / instruction is executed by a processor to implement the steps of the above method.

[0037] Advantages achieved by the application: The method of the application calculates the radial vibration acceleration generated by each harmonic in the radial / tangential electromagnetic force of the outer rotor permanent magnet synchronous motor, further quantitatively evaluates the acceleration amplitude of the radial electromagnetic vibration caused by the radial and tangential electromagnetic force density, and analyzes the phase relationship between the radial electromagnetic vibration accelerations generated by each electromagnetic force wave, so as to extract the key harmonics in the radial and tangential electromagnetic force harmonics. The key harmonics extracted by the application can provide an electromagnetic force harmonic optimization target for the outer rotor structure permanent magnet synchronous motor in the industrial fields of robot joint modules, wheel hub motors, and rotors, so as to suppress the electromagnetic vibration and noise of the outer rotor permanent magnet synchronous motor. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is an electromagnetic topology structure schematic diagram of the outer rotor permanent magnet synchronous motor used in the embodiment of the application;

[0039] Figure 2 is an electromagnetic force space distribution diagram corresponding to 24 times frequency in the embodiment of the application;

[0040] Figure 3is a two-dimensional spectrum diagram of space and time corresponding to the radial and tangential electromagnetic force densities on the inner surface of the permanent magnet in an embodiment of the present invention;

[0041] Figure 4 Schematic diagram of radial and tangential components of the inner surface of the outer rotor permanent magnet of the second-order modal vibration mode in an embodiment of the present invention;

[0042] Figure 5 1. The radial and tangential modal shape distributions and their one-dimensional spectrum of the inner surface of the permanent magnet at a certain axial position in an embodiment of the present invention;

[0043] Figure 6 Schematic diagram of radial acceleration amplitudes generated by various spatial harmonics of the 24-fold rotational frequency electromagnetic force calculated in an embodiment of the present invention;

[0044] Figure 7 Schematic diagram of radial acceleration amplitudes generated by various spatial harmonics of the 48-fold rotational frequency electromagnetic force calculated in an embodiment of the present invention;

[0045] Figure 8 1 is a flow chart of a method for extracting key electromagnetic force wave harmonics of an outer rotor permanent magnet synchronous motor according to an embodiment of the present invention.

[0046] Reference numerals: 1. stator, 2. rotor, 3. permanent magnet, 4. coil, 5. inner surface of permanent magnet, 6. end cover, 7. rotor back iron, 8. acceleration sensor. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention.

[0048] Example 1

[0049] This embodiment provides a method for extracting key electromagnetic force wave harmonics of an outer rotor permanent magnet synchronous motor. The outer rotor permanent magnet synchronous motor has 24 slots and 22 poles. The topology of the two-dimensional cross section and the three-dimensional rotor structure topology are as follows: Figure 1 As shown, the method proposed in this embodiment is used to extract the key harmonics of the electromagnetic force to optimize the electromagnetic vibration and noise of the outer rotor permanent magnet synchronous motor, which includes the following steps:

[0050] Step S1, using electromagnetic finite element software to calculate the electromagnetic force density on the inner surface of the surface-mounted permanent magnet of the outer rotor permanent magnet synchronous motor, and then uniformly sampling the electromagnetic force density data on the inner surface of the permanent magnet;

[0051] The electromagnetic finite element software can be commercial software ANSYS Maxwell, JMAG Designer, Hyperworks Flux or open source software FEMM, etc.

[0052] The electromagnetic force density data at least includes: the electromagnetic force density data of the radial, circumferential and axial three degrees of freedom of the inner surface of the plurality of permanent magnets;

[0053] Step S2, according to the obtained electromagnetic force density data, the radial electromagnetic force is two-dimensional Fourier decomposition, the spatial order ε rp, , time order ξ rp , amplitude and phase of the radial electromagnetic force density corresponding to the radial electromagnetic force density are obtained;

[0054] Similarly, by two-dimensional Fourier decomposition of the tangential electromagnetic force density, the spatial order ε tp , time order ξ tp , amplitude and phase of the tangential electromagnetic force density corresponding to the tangential electromagnetic force density are obtained; the results are shown in Figure 3 ;

[0055] Figure 2 is the 24 times frequency corresponding electromagnetic force space distribution map in this embodiment, Figure 2 , (a) is the spatial distribution vector diagram of the total electromagnetic force section, Figure 2 , (b) is the radial electromagnetic force component spatial distribution vector diagram, Figure 2 , (c) is the tangential electromagnetic force component spatial distribution vector diagram, by Fourier decomposition, the radial / tangential electromagnetic force component can be further decomposed into each harmonic, and the electromagnetic vibration generated by each harmonic is calculated;

[0056] Step S3, the modal shape and frequency of each order of the motor rotor are calculated by using the structure finite element software, and the modal shape data of the inner surface of the surface-mounted permanent magnet is obtained. Each modal shape data at least includes: the modal shape value of the radial, circumferential and axial three degrees of freedom of the inner surface of the plurality of permanent magnets; wherein, the radial and tangential components of the second order modal are shown in Figure 4 , Figure 4 , (a) is the radial component, (b) is the tangential component;

[0057] The structure finite element software can be software Ansys Mechanical, JMAG Designer or Hyper works, etc.

[0058] Step S4, according to the obtained modal shape data of each order, the radial modal shape at each axial position is one-dimensional Fourier decomposition, and the radial modal shape σr amplitude of the sub-harmonic and phase ; similarly, the tangential component of the modal shape is one-dimensionally Fourier decomposed to obtain the tangential modal shape t amplitude of the sub-harmonic and phase , the results are shown in (b) and (c) of FIG. 6; Figure 5

[0059] Figure 5 In FIG. 6, (a) is the spatial distribution diagram of the 2nd, 3rd, and 4th modal shapes, (b) is the amplitude spectrum diagram of the 2nd, 3rd, and 4th modal shapes, and (c) is the phase spectrum diagram of the 2nd, 3rd, and 4th modal shapes. It can be seen that in addition to the ideal 2nd, 3rd, and 4th spatial harmonics, there are also multiple high-order spatial harmonics, which will interact with high-order electromagnetic force harmonics to generate larger electromagnetic vibration acceleration.

[0060] In step S5, the modal shape values of each order at the response point are obtained according to the position coordinate values of the response position in the obtained hth modal shape data, and the modal shape values of each order at least include the modal shape values of each order of the radial direction at the response point position;

[0061] In step S6, the spatial order of the radial electromagnetic force density ε rp obtained in step 2 and the spatial order of the radial component of the modal shape σ r obtained in step 4 are compared, and only the radial electromagnetic force harmonics with the spatial order of the radial electromagnetic force density ε rp equal to the spatial order of the radial component of the modal shape σ r are retained.

[0062] Similarly, according to the spatial order of the tangential electromagnetic force density ε tp obtained in step 2 and the spatial order of the tangential component of the modal shape σ t obtained in step 4, only the radial electromagnetic force harmonics with the spatial order of the tangential electromagnetic force density ε tp equal to the spatial order of the tangential component of the modal shape σ t are retained.

[0063] In step S7, the harmonic amplitude A and phase φ of the radial electromagnetic force density in step 2, the harmonic amplitude A and phase φ of the radial modal shape of each axial position, and the harmonic amplitude A and phase φ of each order of the radial component of the modal shape are calculated according to the following formula.

[0064]

[0065] Among them, R PM is the radius of the inner surface of the permanent magnet, L is the stack length of the motor, ω is the angular frequency of the electromagnetic force, ω r is the mechanical angular frequency, t is the time, and z is the axial position coordinate;

[0066] Similarly, according to the harmonic amplitude of the tangential electromagnetic force density in step 2 and phase , harmonic amplitude of the tangential mode shape at each axial position and phase , calculate the modal generalized force corresponding to the tangential component of each mode according to the following formula ;

[0067] .

[0068] Step S8, according to the modal generalized force corresponding to the radial electromagnetic force of each order mode , modal vibration value φ at the response point r h , angular frequency ω of electromagnetic force, h-order modal frequency ω h and damping ζ h , calculate the response point by (ε rp ,ξ rp )-order radial electromagnetic force harmonics generate complex domain vibration acceleration,

[0069]

[0070] Where N is the highest modal order of the motor, i is the imaginary unit, and the actual vibration acceleration amplitude is obtained by projecting the complex domain vibration acceleration onto the real coordinate axis.

[0071]

[0072] Among them, Real is the real part function;

[0073] Similarly, the calculation is done by (ε tp ,ξ tp )-order tangential electromagnetic force harmonic vibration acceleration

[0074]

[0075] ;

[0076] Step S9: extracting key harmonics according to the vibration acceleration amplitudes generated by electromagnetic force harmonics of various orders. The electromagnetic force harmonics with larger vibration acceleration amplitudes are the key harmonics.

[0077] according to Figure 7, it can be seen that for the 24-fold frequency vibration, the electromagnetic vibrations generated by the radial and tangential electromagnetic forces are in opposite phases, and the 2nd, 20th, 24th, and 46th spatial harmonics are the key harmonics; for the 48-fold frequency vibration, the 4th, 26th, 48th, and 70th spatial harmonics are the key harmonics. The radial electromagnetic vibrations generated by the 24-fold frequency spatial harmonics are based on Figure 6 It can be seen that the 2nd, 20th, 24th and 46th order electromagnetic forces are the key electromagnetic force harmonics in the 24th frequency electromagnetic force; the radial electromagnetic vibrations generated by the 48th frequency spatial harmonics are Figure 7 It can be seen that the 4th, 26th, 48th and 70th order electromagnetic forces are the key electromagnetic harmonics in the 48-fold rotation frequency electromagnetic force. Figure 6 and Figure 7 It can be seen that each order of electromagnetic force contains both radial and tangential components, and the electromagnetic vibration accelerations they generate are in opposite phases and cancel each other out. Therefore, the multiple key electromagnetic force harmonics calculated by this method can be used as optimization targets to suppress the vibration noise of the outer rotor permanent magnet synchronous motor.

[0078] A computer device / apparatus / system comprises a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above method.

[0079] A computer-readable storage medium stores a computer program / instruction thereon, which implements the steps of the above method when executed by a processor.

[0080] A computer program product comprises a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0081] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0082] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the processFigure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0083] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0084] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor, characterized in that: The following steps are involved: Step S1, calculating the electromagnetic force density on the inner surface of the permanent magnet of the outer rotor permanent magnet synchronous motor, wherein the electromagnetic force density data includes at least electromagnetic force density data of the inner surface of multiple permanent magnets in radial, circumferential and axial directions of three degrees of freedom; Step S2: Based on the acquired electromagnetic force density data, perform two-dimensional Fourier decomposition on the radial and tangential electromagnetic forces to obtain the spatial order ε corresponding to the radial electromagnetic force density. rp , time order ξ rp , amplitude and phase ;and The spatial order ε corresponding to the tangential electromagnetic force density tp , time order ξ tp , amplitude and phase ; Step S3, calculating the modal vibration shape and frequency of each order of the permanent magnet synchronous motor rotor, and obtaining the modal vibration shape data of the inner surface of the permanent magnet, wherein each modal vibration shape data includes at least the modal vibration shape values ​​of the radial, circumferential, and axial degrees of freedom of the inner surface of the permanent magnet; Step S4: Based on the acquired vibration mode data of each order mode, perform one-dimensional Fourier decomposition on the radial and tangential vibration modes at each axial position to obtain the radial vibration mode σ at each axial position z. r The amplitude corresponding to the subharmonic and phase , and the tangential mode shape σ t The amplitude corresponding to the subharmonic and phase ; Step S5, obtaining the modal vibration mode values ​​of each order at the response point according to the coordinate value of the response position in the obtained h-th order modal vibration mode data; Step S6, according to the spatial order ε of the radial electromagnetic force density obtained in step 2 rp and the spatial order σ of the radial component of the modal vibration shape obtained in step 4 r , only the spatial order ε of the radial electromagnetic force density is retained rp and the spatial order σ of the radial component of the modal vibration shape r Equal radial electromagnetic force harmonics; Similarly, according to the spatial order ε of the tangential electromagnetic force density obtained in step 2 tp and the spatial order σ of the tangential component of the modal vibration shape obtained in step 4 t , only the spatial order ε of the tangential electromagnetic force density is retained tp and the spatial order of the tangential component of the modal vibration shape σ t Equal radial electromagnetic force harmonics; Step S7, according to the radial electromagnetic force density harmonic amplitude in step 2 and phase , harmonic amplitude of radial mode shape at each axial position and phase , calculate the modal generalized force corresponding to the radial component of each mode ; According to the harmonic amplitude of the tangential electromagnetic force density in step 2 and phase , harmonic amplitude of the tangential mode shape at each axial position and phase , calculate the modal generalized force corresponding to the tangential component of each mode ; Step S8, according to the modal generalized force corresponding to the radial electromagnetic force of each order mode , modal vibration value φ at the response point r h , angular frequency ω of electromagnetic force, h-order modal frequency ω h and damping ζ h , calculate the response point by (ε rp ,ξ rp )-order radial electromagnetic force harmonics generated by the complex domain vibration acceleration; similarly, calculate the (ε tp ,ξ tp ) order tangential electromagnetic force harmonic vibration acceleration; Step S9: extracting key harmonics according to the vibration acceleration amplitudes generated by electromagnetic force harmonics of various orders. The electromagnetic force harmonics with larger vibration acceleration amplitudes are the key harmonics.

2. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 1, characterized in that: In step 1, electromagnetic finite element software is used to calculate the electromagnetic force density on the inner surface of the permanent magnet of the outer rotor permanent magnet synchronous motor.

3. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the modal vibration shapes and frequencies of the motor rotor are calculated using structural finite element software.

4. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 1, characterized in that: In step S7, the modal generalized force corresponding to the radial component of each mode is calculated according to the following formula: ; ； Among them, R PM is the radius of the inner surface of the permanent magnet, L is the stack length of the motor, ω is the angular frequency of the electromagnetic force, ω r is the mechanical angular frequency, t is the time, and z is the axial position coordinate.

5. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 4, characterized in that: In step S7, the modal generalized force corresponding to the tangential component of each mode is calculated according to the following formula: ; 。 6. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 1, characterized in that: In step S8, the following formula is used to calculate the response point (ε rp ,ξ rp )-order radial electromagnetic force harmonics generate complex domain vibration acceleration, ； Where N is the highest modal order of the motor, i is the imaginary unit, and the actual vibration acceleration amplitude is obtained by projecting the complex domain vibration acceleration onto the real coordinate axis. ； Among them, Real is the real part function.

7. The method for extracting key electromagnetic force waves and harmonics of an outer rotor permanent magnet synchronous motor according to claim 1, characterized in that: In step S8, the following formula is used to calculate (ε tp ,ξ tp ) order tangential electromagnetic force harmonic vibration acceleration; ； 。 8. A computer device / apparatus / system comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method of claim 1 .

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to claim 1 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to claim 1 are implemented.

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