Harmonic blocking alternating pole permanent magnet wheel hub motor and harmonic group difference vibration suppression method

Abstract

This invention belongs to the field of electric motors and discloses a harmonic-blocking alternating-pole permanent magnet hub motor and a method for differentiated vibration suppression of harmonic groups. The harmonic-blocking alternating-pole permanent magnet hub motor provided by this invention employs a harmonic trap stator and a rotor structure with local magnetic short-circuit magnetic barriers under alternating poles to actively suppress the amplitude of harmonic sources. The method for differentiated vibration suppression of harmonic groups provided by this invention is as follows: actively identifying the main vibration source under the current operating condition, extracting its dominant harmonic group characteristic frequencies as the core optimization object, employing a multi-objective optimization method to obtain the Pareto front and its solution set under each operating condition, taking the intersection of parameters under different operating conditions, selecting the parameter set with the best overall performance, classifying the basic harmonics of the vibration source as a monitoring layer, monitoring them without active compensation, and achieving differentiated and precise control. This invention overcomes the limitations of traditional methods being fixed and singular, realizing the active suppression of dynamically changing main vibration sources within the entire operating range of the alternating-pole permanent magnet hub motor.

Description

Technical Field

[0001] This invention belongs to the field of motors, specifically relating to a harmonic blocking type alternating pole permanent magnet hub motor and a harmonic group differentiated vibration suppression method. Background Technology

[0002] With the rapid development of new energy vehicles, especially distributed drive technology, in-wheel motors, as core components for achieving efficient and flexible vehicle drive, directly determine the vehicle's dynamic performance and ride quality. Alternating pole permanent magnet motors, with their unique magnetic circuit design, significantly reduce the amount of permanent magnets used and lower manufacturing costs while maintaining high torque density and efficiency, making them one of the most promising technologies in the current in-wheel motor field. However, the architecture of directly integrating the motor into the wheel means that electromagnetic vibration and noise are transmitted directly to the vehicle body without the attenuation of a traditional transmission system, posing a serious challenge to the vehicle's noise, vibration, and harshness (NVH) performance. Therefore, developing efficient and reliable vibration suppression technology is a key challenge that must be overcome to achieve the industrial application of alternating pole permanent magnet in-wheel motors.

[0003] Chinese patent CN202510977119.2 discusses various skewing methods, such as stator skew, rotor skew, stepped skew, and herringbone skew, primarily aimed at reducing cogging torque and thus vibration. Furthermore, Chinese patent CN202510861327.6 proposes other methods, including chamfering, grooving, permanent magnet segmentation, changing magnetic pole curvature, and modifying tooth profile; these methods also reduce vibration by decreasing torque pulsation. However, these structural fine-tuning methods have some drawbacks, such as reduced output torque, difficulty in achieving automated production, increased manufacturing costs, and decreased mechanical strength. Chinese patent CN202311038076.9 studies a method of injecting appropriate compensation current. This method can obtain a new electromagnetic force with the same spatial order and frequency as the original electromagnetic force but opposite phase, thereby weakening the total radial electromagnetic force to reduce vibration. However, this method inevitably increases the difficulty of drive control and reduces output torque.

[0004] It is evident that most existing methods for suppressing motor vibration are based on specific operating points (such as the rated point) or designed for a single type of vibration source. However, in actual vehicle operation, hub motors need to cover complex operating conditions across the entire speed range, from extremely low-speed crawling and frequent start-stop to high-speed cruising. Furthermore, under different speeds and loads, the dominance of the aforementioned main vibration sources will dynamically shift.

[0005] Therefore, there is an urgent need to develop an active vibration suppression technology for motors that can accurately suppress key harmonic amplitudes and has the ability to adapt to operating conditions. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a harmonic-blocking alternating-pole permanent magnet hub motor and a harmonic group-differentiated vibration suppression method. This harmonic-blocking alternating-pole permanent magnet hub motor employs a harmonic-trapping stator and a rotor structure with local magnetic short-circuit barriers under alternating poles to actively suppress the amplitude of harmonic sources. The harmonic group-differentiated vibration suppression method not only effectively suppresses the amplitude of key harmonics from the main vibration source but also achieves high-efficiency, low-noise operation by actively and dynamically identifying and layering the dominant harmonic groups of the main vibration source across the entire operating speed range.

[0007] In a first aspect, the present invention provides a harmonic blocking alternating pole permanent magnet hub motor, the harmonic blocking alternating pole permanent magnet hub motor comprising a stator and a rotor sleeved outside the stator.

[0008] The stator teeth have N circular closed slots circumferentially opened inside, and harmonic absorption rings are embedded in the circular closed slots.

[0009] Inside the rotor, there are g U-shaped grooves with openings facing the air gap and 2g arc-shaped two-section magnetic barriers arranged alternately along the circumference.

[0010] The U-shaped groove includes two side arms and a transverse part connecting the tops of the two side arms. A bread-shaped permanent magnet is embedded in the middle of the transverse part, and a rectangular permanent magnet is embedded in the middle of the side arms.

[0011] The arc-shaped two-segment magnetic barrier consists of two spaced arc-shaped segments embedded on both sides of the side arm. In the arc-shaped two-segment magnetic barrier, the radius of curvature of the arc-shaped segment between the two side arms of the U-shaped groove is R1, and the radius of curvature of the arc-shaped segment between each U-shaped groove is R2, where R1 > R2.

[0012] Along the circumferential edge of the rotor near the air gap, g magnetic barrier groups are arranged at intervals. Each magnetic barrier group includes two semi-elliptical magnetic barriers and a parallelogram magnetic barrier positioned between the two semi-elliptical magnetic barriers. The centerline of the parallelogram magnetic barrier is offset by an angle θ relative to the axis of the U-shaped groove. p Used to break magnetic circuit symmetry to suppress specific subharmonics, 1.5deg≤θ p ≤3deg. The offset angle θ p The design method is as follows: Based on the characteristic frequencies of the dominant harmonic group of the main oscillator, the magnetic flux density fluctuation curves of different frequency harmonics on the circumference of the motor are obtained. According to the spatial position / mechanical angle of the peaks and troughs, the peak values ​​of each frequency amplitude are marked as peak points. The offset angle θ is obtained by single-parameter scanning. p .

[0013] In some embodiments, there is a gap between the two arc-shaped segments of the arc-shaped two-segment magnetic barrier and their corresponding side arms, the gap being used to increase the magnetic shielding effect.

[0014] In some embodiments, the width of the gap is 0.5mm-1mm.

[0015] In some embodiments, the harmonic absorption ring is made of amorphous alloy or nanocrystalline soft magnetic composite material.

[0016] In a second aspect, the present invention provides a harmonic group differential vibration suppression method for the above-mentioned harmonic blocking alternating pole permanent magnet hub motor, the harmonic group differential vibration suppression method comprising the following steps:

[0017] S1. Determine the range of values ​​for the structural parameters of the harmonic blocking alternating pole permanent magnet hub motor;

[0018] S2. Actively identify the main vibration source under the current operating conditions and extract the characteristic frequencies of its dominant harmonic group;

[0019] S3. Using the characteristic frequencies of the dominant harmonic group of the main source obtained in step S2 as the core optimization object, a multi-objective optimization method is adopted to obtain the Pareto front and its solution set under each working condition. The intersection of parameters under different working conditions is taken to select the parameter set with the best comprehensive performance.

[0020] In some embodiments, in step S2, the main vibration source under high-speed conditions is the radial electromagnetic force density F as shown in the following formula. r (θ,t);

[0021] ;

[0022] In the formula, μ0 is the free permeability, and f PM (θ,t) represents the permanent magnet magnetomotive force, f ARM (θ,t) represents the armature magnetomotive force field, Λ s (θ) is the relative permeability of the stator, Λ r (θ,t) is the relative permeability of the rotor; F μ Let F be the magnetomotive force amplitude of the μth spatial harmonic. ν Let μp be the magnetomotive force amplitude of the νth spatial harmonic, μ = 2m + 1 (m = 0, 1, 2, ...), p be the number of rotor pole pairs, θ be the rotor mechanical angle, ω be the current angular frequency, and Λ0 be the average magnetic permeability. k Λ represents the amplitude of the k-th harmonic permeability of the stator, and Z represents the number of stator slots; i S is the amplitude of the i-th harmonic permeability of the rotor; ν The direction of rotation of the armature magnetic field harmonic ν is indicated by "1" and "-1" indicating forward and reverse rotation, respectively. α is the number of motor units, and να is the harmonic order of the armature magnetic field magnetomotive force.

[0023] In some embodiments, in step S2, the main vibration source in the low-speed condition is torque pulsation T. rippleand cogging torque T cog Torque pulsation T ripple With cogging torque T cog The relationship is shown in the following formula:

[0024] ;

[0025] ;

[0026] In the formula, T pm It is the permanent magnet torque, T r It is the reluctance torque, T out-max It is the maximum torque, T out-min It is the minimum torque, T out-avg It is the average torque; B mn and G mn Here are the Fourier expansion coefficients, where B mn The Fourier coefficients of the toothed structure for magnetic permeability modulation are affected by the rotor pole distribution. mn The amplitude of the m-th spatial harmonic is obtained by Fourier decomposition of the air gap magnetic flux density in the radial direction. This is influenced by the stator slot distribution, where Z is the number of stator slots, and p... pm R is the number of pole pairs of the permanent magnet, l is the axial length, and R is the axial length. r It is the inner radius of the rotor, R s θ is the outer radius of the stator, and θ is the mechanical angle of the rotor. rt It is the circumferential angle of the rotor teeth. θ ss G1 is the circumferential angle between the stator slots. G1 is the permeability per unit area of ​​the stator tooth region.

[0027] In some embodiments, the method for extracting the characteristic frequencies of the dominant harmonic group in step S2 is as follows:

[0028] Based on the main vibration source signal and the motor electrical signal, order analysis is performed using finite element software to analyze the vibration energy spectrum distribution corresponding to a specific speed and load under the current working condition in real time.

[0029] Multiple peak frequency components with an energy proportion exceeding a set threshold are identified as the dominant harmonic group of the main oscillator, and their key characteristic frequencies are extracted as the characteristic frequencies of the dominant harmonic group.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the harmonic blocking permanent magnet hub motor structure proposed in this invention, a harmonic trap stator and a local magnetic short-circuit magnetic barrier rotor structure under alternating poles are adopted to actively suppress the amplitude of the source harmonics; the stator harmonic absorption ring is made of amorphous alloy or nanocrystalline soft magnetic composite material, which can form a short-circuit loop of high-frequency harmonic flux, preventing the high-frequency harmonic flux from propagating in the stator teeth, thereby effectively reducing high-frequency vibration; the four arc segments in the rotor have different radii of curvature, which can form multi-frequency suppression for different orders of harmonics, effectively weakening the amplitude of specific harmonics such as the 5th, 7th, and 11th orders; the parallelogram magnetic barrier asymmetric design breaks the harmonic cycle, suppresses the magnetic permeability change caused by the tooth slot harmonics, and keeps the fundamental magnetic circuit unaffected, thus achieving a balance between source harmonic suppression and fundamental performance.

[0032] (2) In the harmonic blocking permanent magnet hub motor structure proposed in this invention, a semi-elliptical magnetic barrier is set on the inner edge of the rotor and extends from the side arm of the U-shaped magnetic barrier to the edge, effectively guiding the leakage flux in the inter-pole region, reducing end leakage flux, and improving the utilization rate of permanent magnets; the parallelogram magnetic barrier is located in the middle region between the two semi-elliptical magnetic barriers, further optimizing the inter-pole magnetic circuit distribution and improving the overall magnetic circuit efficiency of the motor.

[0033] (3) This invention proposes a full-condition vibration suppression method based on the optimization of the main vibration source, which clarifies the different dominant vibration sources of the hub motor under different operating conditions and derives the characteristics of each dominant vibration source by formula; differentiated stratification is carried out by contribution evaluation, and the limited high-performance computing resources are concentrated on compensating the core layer harmonics with the largest amplitude and the most significant harm; a multi-objective optimization method is adopted for the dominant harmonic group of the core layer, and only observation is performed on the basic harmonic group of the monitoring layer; this differentiated control design avoids excessive investment in secondary harmonics, and while achieving excellent suppression effect, it significantly reduces the computing load and memory consumption of the controller, and improves the overall energy efficiency and economy of the system. Attached Figure Description

[0034] Figure 1 This is a topology diagram of a harmonic blocking alternating pole permanent magnet hub motor;

[0035] Figure 2 yes Figure 1 Enlarged view of a portion of the image;

[0036] Figure 3 yes Figure 1 Geometric dimension annotation diagram and permanent magnet magnetization schematic diagram;

[0037] Figure 4 This is a flowchart illustrating the method of the present invention;

[0038] Figure 5 The parallelogram magnetic barrier offset angle θ of this invention p Single-parameter scan diagram;

[0039] Figure 6 This is the Pareto front for multi-objective optimization under low-speed conditions in this invention;

[0040] Figure 7 This is the Pareto front for multi-objective optimization under high-speed conditions in this invention;

[0041] Figure 8 It is the three-dimensional waveform of the radial electromagnetic force density of the initial motor under high-speed operating conditions;

[0042] Figure 9 It is the three-dimensional waveform of the radial electromagnetic force density of the optimal motor under high-speed operating conditions;

[0043] Figure 10 This refers to torque performance under low-speed conditions;

[0044] Figure 11 It refers to torque performance under high-speed operating conditions;

[0045] In the diagram: 1. Rotor; 2. Stator; 3. Armature winding; 4. Shaft; 5. Circular closed slot; 6. Harmonic absorption ring; 7. U-shaped slot; 8. Bread-shaped permanent magnet; 9. Rectangular permanent magnet; 10. Two-section arc-shaped magnetic barrier; 11. Semi-elliptical magnetic barrier; 12. Parallelogram magnetic barrier; 13. Air gap. Detailed Implementation

[0046] An embodiment of the first aspect of the present invention provides a harmonic blocking alternating pole permanent magnet hub motor, see [link to previous document]. Figure 1 The stator (2) includes a stator (2) and a rotor (1) fitted outside the stator (2); N circular closed slots (5) are opened circumferentially inside the teeth of the stator (2), and a harmonic absorption ring (6) is embedded in the circular closed slot (5); g U-shaped slots (7) with openings facing the air gap (13) and 2g arc-shaped two-section magnetic barriers (10) are arranged circumferentially inside the rotor (1); the U-shaped slot (7) includes two side arms and a transverse part connecting the top of the two side arms, a bread-shaped permanent magnet (8) is embedded in the middle of the transverse part, and a rectangular permanent magnet (9) is embedded in the middle of the side arm; the arc-shaped two-section magnetic barrier (10) is composed of two arc-shaped segments embedded on both sides of the side arm.

[0047] In some embodiments of the present invention, see Figure 2 The two arc-shaped segments of the two-section magnetic barrier (10) have gaps between their corresponding side arms. These gaps are used to increase the magnetic isolation effect of the magnetic barrier and reduce eddy current losses. The width of the gap is preferably 0.5mm-1mm. On the side of the rotor (1) near the air gap, g magnetic barrier groups are arranged circumferentially. Each magnetic barrier group includes two semi-elliptical magnetic barriers (11) and a parallelogram magnetic barrier (12) arranged between the two semi-elliptical magnetic barriers.

[0048] In some embodiments of the present invention, see Figure 1-3 The bread-shaped permanent magnet (8) is arranged tangentially, and the arc-shaped convex surface of the bread-shaped permanent magnet (8) faces the outside of the rotor. Rectangular permanent magnets (9) are embedded in the middle of the two side arms respectively. Each rectangular permanent magnet (9) is arranged radially, and its length direction is consistent with the extension direction of the side arm.

[0049] In some embodiments of the present invention, see Figure 3 The centerline of the parallelogram magnetic barrier (12) is offset by an angle θ relative to the axis of the U-shaped groove (7). p It is used to break the symmetry of the magnetic circuit to suppress specific subharmonics.

[0050] In some embodiments of the present invention, the harmonic absorption ring (6) is made of amorphous alloy or nanocrystalline soft magnetic composite material, and has significant permeability attenuation characteristics at specific high frequency frequencies (such as 1000Hz and above), which can form a short-circuit loop of high frequency harmonic flux, prevent high frequency harmonic flux from propagating in the stator teeth, thereby effectively reducing high frequency vibration.

[0051] In some embodiments of the present invention, in the arc-shaped two-segment magnetic barrier (10), the radius of curvature of the arc segment located between the two side arms of the U-shaped groove (7) is R1, and the radius of curvature of the arc segment located between each U-shaped groove (7) is R2, where R1 > R2.

[0052] See Figure 3 ,for Figure 1 The figure shows the geometric dimensions and a schematic diagram of the permanent magnets being magnetized. As shown, the bread-shaped permanent magnets are magnetized radially, while the rectangular permanent magnets are magnetized tangentially, and the two rectangular permanent magnets in each pair of poles are magnetized in opposite directions. Figure 3 The green arrow in the image illustrates one possible magnetization strategy. This direction is for illustrative purposes only, and the magnetization direction can also be completely opposite.

[0053] A second aspect of the present invention also provides a harmonic group differential vibration suppression method for the above-described harmonic blocking alternating pole permanent magnet hub motor, such as... Figure 4 As shown, it includes the following steps:

[0054] S100: Determine the range of structural parameters for the harmonic blocking alternating pole permanent magnet hub motor. Six key design variables for this motor are selected as the design variables to be optimized: length L of the bread-shaped permanent magnet. pm1 Width H pm1 The length L of the rectangular permanent magnet pm2 Width H pm2 Circumferential angle θ of stator slots ss The circumferential angle θ of the rotor teeth rtThe central angle θz2 of the arc-shaped magnetic barrier located inside the transverse part of the U-shaped magnetic barrier, the central angle θz1 of the arc-shaped magnetic barrier located outside the transverse part of the U-shaped magnetic barrier, and the offset angle θ of the parallelogram magnetic barrier. p Based on previous design experience and references, their initial ranges are determined to be L. pm1 For [10mm, 15mm], H pm1 For [3mm, 5mm], L pm2 For [10mm, 15mm], H pm2 For [2mm, 4mm], θ ss is [0.5deg,1.5deg], θ rt θz1 is [5deg, 15deg], θz2 is [20deg, 30deg], θz3 is [40deg, 50deg], θ p [1.4deg, 2.8deg].

[0055] S200: Active identification and feature extraction of dominant harmonic groups of the main oscillator source, that is, actively identifying the type of oscillator source and its dominant harmonic group characteristics that play a dominant role under the current working conditions (torque and load conditions).

[0056] Theoretically, the main factors affecting the electromagnetic vibration of a motor are cogging torque, torque pulsation, and radial force, and their contribution to vibration varies under different operating conditions. For example, under low-speed conditions, the frequency distribution of radial electromagnetic force does not change when the load increases; only the amplitude of radial electromagnetic force increases slightly in the low-frequency region. Therefore, disturbances such as cogging torque and torque pulsation are considered the main sources of vibration. However, under high-speed conditions, the fundamental frequency of radial electromagnetic force increases with the increase of rotational speed. Since the natural frequency of hub motors is relatively high, the probability of motor resonance increases, making radial electromagnetic force the main source of vibration.

[0057] (1) Analysis of the main vibration source under high-speed operating conditions

[0058] Radial electromagnetic force density F r (θ,t) Analysis:

[0059] (4)

[0060] In the formula, μ0 is the free permeability, and f PM (θ,t) represents the permanent magnet magnetomotive force, f ARM (θ,t) represents the armature magnetomotive force field, Λ s (θ) is the relative permeability of the stator, Λ r (θ,t) is the relative permeability of the rotor; F μ Let F be the magnetomotive force amplitude of the μth spatial harmonic. νLet μp be the magnetomotive force amplitude of the νth spatial harmonic, μ = 2m + 1 (m = 0, 1, 2, ...), p be the number of rotor pole pairs, θ be the rotor mechanical angle, ω be the current angular frequency, and Λ0 be the average magnetic permeability. k Λ represents the amplitude of the k-th harmonic permeability of the stator, and Z represents the number of stator slots; i S is the amplitude of the i-th harmonic permeability of the rotor; ν The direction of rotation of the armature magnetic field harmonic ν is indicated by "1" and "-1" indicating forward and reverse rotation, respectively. α is the number of motor units, and να is the harmonic order of the armature magnetic field magnetomotive force.

[0061] (2) Analysis of the main vibration source under low-speed operating conditions

[0062] Torque pulsation T ripple and cogging torque T cog Analysis shows that the two have the following relationship:

[0063] (5)

[0064] (6)

[0065] In the formula, T pm It is the permanent magnet torque, T r It is the reluctance torque, T out-max It is the maximum torque, T out-min It is the minimum torque, T out-avg It is the average torque; B mn and G mn Here are the Fourier expansion coefficients, where B mn The Fourier coefficients of the toothed structure for magnetic permeability modulation are affected by the rotor pole distribution. mn The amplitude of the m-th spatial harmonic is obtained by Fourier decomposition of the air gap magnetic flux density in the radial direction. This is influenced by the stator slot distribution, where Z is the number of stator slots, and p... pm R is the number of pole pairs of the permanent magnet, l is the axial length, and R is the axial length. r It is the inner radius of the rotor, R s θ is the outer radius of the stator, and θ is the mechanical angle of the rotor. rt It is the circumferential angle of the rotor teeth. θ ss G1 is the circumferential angle between the stator slots. G1 is the permeability per unit area of ​​the stator tooth region.

[0066] It can be seen that the cogging torque is related to the motor structural parameter θ rt and θ ss Closely related.

[0067] (3) Feature extraction of dominant harmonic group

[0068] Based on the main vibration source signal and the motor electrical signal, including the cogging torque and torque pulsation under low-speed conditions, and the radial electromagnetic force under high-speed conditions, order analysis is performed using finite element software. The spectral distribution of vibration energy under the current operating condition (specific speed and load) is analyzed in real time. Multiple peak frequency components with energy proportions exceeding a set threshold are identified and categorized into the dominant harmonic group of the main vibration source. Key characteristics are extracted: harmonic order, energy amplitude, and phase. The weight of this harmonic's contribution to the total vibration is calculated. Table 1 shows the harmonic characteristics of torque pulsation under low-speed conditions, Table 2 shows the harmonic characteristics of cogging torque under low-speed conditions, and Table 3 shows the harmonic characteristics of radial electromagnetic force under high-speed conditions.

[0069] Table 1. Torque ripple harmonic distribution of a 36-slot 50-pole alternating pole permanent magnet hub motor under low-speed conditions.

[0070] <![CDATA[Harmonic order i th > <![CDATA[2 th ]]> <![CDATA[4 th ]]> <![CDATA[6 th ]]> <![CDATA[8 th ]]> <![CDATA[10 h ]]> <![CDATA[12 th ]]> <![CDATA[14 th ]]> <![CDATA[16 th ]]> <![CDATA[18 th ]]> <![CDATA[20 th ]]> <![CDATA[22 th ]]> <![CDATA[24 th ]]> <![CDATA[26 th ]]> <![CDATA[28 th ]]> Amplitude (Nm) 0.08 0.14 0.06 0.01 0.23 0.15 0.18 0.35 0.26 0.54 0.25 0.82 0.48 0.25 Phase (°) 32 121 212 307 15 108 199 284 48 138 226 310 73 162 Total vibration contribution weight (%) 2.1 3.7 1.6 0.3 6.1 3.9 4.7 9.2 6.8 14.2 6.6 21.6 12.6 6.6

[0071] Table 2. Harmonic Distribution of Cogging Torque in Low-Speed ​​Operation of a 36-Slot 50-Pole Alternating Pole Permanent Magnet Hub Motor

[0072] <![CDATA[Harmonic order i th > <![CDATA[2 th ]]> <![CDATA[4 th ]]> <![CDATA[6 th ]]> <![CDATA[8 th ]]> <![CDATA[10 h ]]> <![CDATA[12 th ]]> <![CDATA[14 th ]]> <![CDATA[16 th ]]> <![CDATA[18 th ]]> <![CDATA[20 th ]]> <![CDATA[22 th ]]> <![CDATA[24 th ]]> <![CDATA[26 th ]]> <![CDATA[28 th ]]> Amplitude (Nm) 0.13 0.34 0.67 0.34 0.30 0.15 0.16 0.24 0.31 0.18 0.23 0.16 0.09 0.16 Phase (°) 15 82 45 118 63 156 89 203 124 275 197 312 256 348 Total vibration contribution weight (%) 3.2 12.5 28.4 12.5 9.6 4.1 4.3 6.8 9.2 4.9 6.1 4.3 2.1 4.3

[0073] Table 3. Radial electromagnetic force harmonic distribution of a 36-slot 50-pole alternating pole permanent magnet hub motor under high-speed operating conditions.

[0074] <![CDATA[Harmonic order i th > <![CDATA[2 th ]]> <![CDATA[4 th ]]> <![CDATA[6 th ]]> <![CDATA[8 th ]]> <![CDATA[10 h ]]> <![CDATA[12 h ]]> <![CDATA[14 th ]]> <![CDATA[16 th ]]> <![CDATA[18 th ]]> <![CDATA[20 th ]]> <![CDATA[22 th ]]> <![CDATA[24 th ]]> <![CDATA[26 h ]]> <![CDATA[28 th ]]> <![CDATA[Amplitude (×10 4 Nm)]]> 0.12 0.56 0.98 0.21 0.14 0.19 0.27 0.54 0.16 0.58 0.02 0.32 0.87 0.17 Phase (°) 15 28 42 56 70 84 98 112 126 140 154 168 182 196 Total vibration contribution weight (%) 1.2 8.5 23.6 3.8 1.9 2.5 3.9 14.2 2.1 12.7 0.3 5.2 18.3 2.6

[0075] The total vibration contribution weight is calculated as a percentage of the source amplitude of each harmonic to the sum of all harmonic amplitudes. The formula is: Total vibration contribution weight = (Amplitude of the i-th harmonic of the source / Σ) j The formula is calculated as follows: (Harmonic Amplitude) × 100%, where i is the harmonic order and j is the index of the summation, indicating that all harmonic orders in the table are traversed, i.e., 2nd, 4th, ..., 28th. Harmonics with a total vibration contribution weight greater than or equal to 14% are selected as dominant harmonics. The 14% limit is based on "2 times the average contribution," because there are a total of 14 harmonics (2nd to 28th), and the average weight of each harmonic is approximately 100% / 14. Therefore, 2 times the average contribution = 2 × 100% / 14, which is approximately equal to 14%, used to filter out the few harmonics that play a dominant role in the vibration.

[0076] According to Tables 1 and 2, under low-speed conditions, the 20th and 24th harmonics are selected as the dominant harmonics for the torque pulsation vibration source, and the 6th harmonic is selected as the dominant harmonic for the cogging torque; according to Table 3, the 6th, 16th, and 26th harmonics are selected as the dominant harmonics for the radial electromagnetic force vibration source under high-speed conditions; based on this, the dominant harmonic group of the main vibration source in the full speed range and the dominant harmonic group of the main vibration source in the low-speed condition can be obtained [6]. th T cog , 20th T ripple , twenty four th T ripple ] and the dominant harmonic group of the main oscillator under high-speed operating conditions [6 th F r , 16 th F r 26 th F r The remaining orders are all fundamental harmonics.

[0077] S300: Actively blocks harmonic paths.

[0078] Based on the characteristic frequencies of the dominant harmonic group of the main oscillator, the magnetic flux density fluctuation curves of different frequency harmonics on the circumference of the motor are obtained. Carefully observe the spatial position / mechanical angle of the peaks and troughs, and mark the peak values ​​of each frequency. A parallelogram magnetic barrier is placed at the critical bottleneck position where the harmonic flux attempts to "take a shortcut" or "concentrate its passage," i.e., the position of the peak point determines the offset angle θ. p offset angle θ p Single-parameter scan, such as Figure 5 Obtain the offset angle θ p Optimal design, θ p The minimum value is 2deg. According to... Figure 5 It can be seen that when the asymmetric magnetic barrier offset angle is 2deg, the dominant harmonic group of the main oscillator in the low-speed condition [6] th T cog , 20 th T ripple ,twenty four th T ripple ] and the dominant harmonic group of the main oscillator under high-speed operating conditions [6 th F r , 16 th F r , 26 th F r The overall low amplitude indicates that the source harmonics are effectively suppressed, which helps to suppress motor vibration.

[0079] S400: Differentiated design of the main source harmonic group in the full speed domain.

[0080] (1) Optimization design of dominant harmonic groups of core layer vibration source

[0081] 1) Setting the objective function and constraints for low-speed operation

[0082] In the low-speed range, the torque pulsation has a 20th harmonic. th T ripple 24th harmonic th T ripple and cogging torque 6th harmonic 6 th Tcog The radial electromagnetic force is simultaneously set as the primary objective; it acts as a constraint in the optimization and plays a crucial role in the vibration; the objective function and constraint conditions are as follows:

[0083] (7)

[0084] In the formula, F r-max It is the maximum radial electromagnetic force, T out It is the output torque, T ripple It is torque pulsation, T cog This is the cogging torque. Output torque T out This is the basic capability of a motor to drive a load, and it must meet the minimum torque requirements of electric vehicle applications. 20 Nm is a medium-low torque level. To ensure the motor can operate normally at low speeds, the torque limit condition is greater than or equal to 20 Nm; Torque ripple T ripple This can lead to speed fluctuations, vibration, and noise, affecting system control accuracy and comfort. For passenger vehicle drive motors, 15% is an acceptable engineering upper limit, so the constraint is set to less than or equal to 15%; cogging torque T cog This is a unique positioning torque of permanent magnet motors, which can cause low-speed vibration and unstable starting. It is generally desirable for its absolute value to be as small as possible, typically less than 5% to 10% of the rated torque. Therefore, the limiting condition is set to less than or equal to 2 Nm; radial electromagnetic force F r Acting on the stator teeth and rotor surface, excessive radial magnetic pull can lead to stator deformation, increased noise, and even bearing overload. In motor design, the radial magnetic pull is generally controlled within the range of 0.1–1 MPa. To control stator modal vibration or avoid concentrated forces caused by local magnetic saturation, the maximum radial electromagnetic force F... r-max It must be less than or equal to 3.5 x 10 5 N / m 2 (0.35MPa).

[0085] 2) Setting the objective function and constraints for high-speed operating conditions

[0086] In the high-speed region, the radial electromagnetic force has a 6th harmonic. th F r 16th harmonic th F r and the 26th harmonic 26 th F r It was simultaneously set as the primary objective; during the optimization process, the cogging torque T was selected. cog and torque pulsation T ripple As a constraint.

[0087] The objective function and constraints are as follows:

[0088] (8)

[0089] In the formula, P core This refers to iron loss. Under high-speed conditions, the motor typically operates in the constant power region or the weak magnetic field region, resulting in an output torque lower than the low-speed peak torque. 5 Nm represents the minimum driving capability required to maintain vehicle cruising at high speeds; the torque limit is set to be greater than or equal to 5 Nm. Radial electromagnetic force F r At high speeds, stator modal resonance and high-frequency noise are easily induced. Furthermore, due to the coupling of centrifugal force and magnetic pull, their amplitude must be strictly controlled. Also, because even a small radial force at high speeds can cause severe vibrations due to the excitation frequency approaching the structure's natural frequency, the radial electromagnetic force constraint is reduced by an order of magnitude compared to low-speed conditions. Here, the constraint condition is set to less than or equal to 2.3 × 10⁻⁶. 4 N / m 2 Iron loss P core Including hysteresis loss and eddy current loss, which increase sharply with increasing speed, these are the main heat sources of high-speed motors. Excessive iron loss can lead to excessive temperature rise and decreased efficiency. This constraint is used to limit the losses caused by high-frequency magnetic fields. Generally, iron loss should not exceed 1% to 2% of the motor's rated power to ensure controllable temperature rise during high-speed operation. For small and medium power motors (10kW level), the iron loss limit is less than or equal to 100W; torque pulsation T ripple The limiting conditions remain the same as for low-speed operation, still less than or equal to 15%; cogging torque T cog It mainly affects low-speed start-stop performance. At high speeds, the inertia will filter out the fluctuations, so the impact is smaller, but it still needs to be limited to avoid transient impacts or increased control difficulty during acceleration and deceleration. Furthermore, cogging torque is not the main problem at high speeds, and a larger residual value is allowed. Therefore, the limiting conditions are consistent with those at low speeds, and are set to less than or equal to 2 Nm.

[0090] 3) Multi-objective optimization under varying operating conditions

[0091] To address the conflict between multiple objectives during the optimization process, the Non-Dominated Sorting Genetic Algorithm (NSGA-II) based on genetic algorithms is applied to the decision space exploration. According to the objective function and constraints in equation (7), the Pareto front of NSGA-II under low-speed conditions is as follows: Figure 6 As shown, the Pareto front clearly meets the above design requirements. It can be seen that the front is discretely distributed rather than a continuous curve, and the points on the front represent the optimal compromise under the current design variable constraints. Any attempt to improve one objective alone will lead to the deterioration of another objective. That is, the 6th order cogging torque, the 20th order torque ripple, and the 24th order torque ripple cannot be optimal at the same time, reflecting the trade-off between objectives. According to the objective function and constraints of equation (8), the Pareto front of NSGA-II under low-speed conditions is as follows: Figure 7As shown, this Pareto front clearly meets the above design requirements and has better overall performance; based on Figure 6 and Figure 7 The solution sets shown are used to select the optimal motor model by taking the intersection of parameters under different operating conditions and finding the parameter set with the best overall performance. Based on the actual design requirements, the final optimized design variable size of the motor is determined to be: L. pm1 It is 13.4mm, H pm1 It is 4.8mm, L pm2 It is 12mm, H pm2 It is 3.4mm, θ ss For 1deg, θ rt The value is 5.9 degrees, θz1 is 22 degrees, θz2 is 43 degrees, and θ p It is 2deg.

[0092] (2) Design of basic harmonic groups of vibration source in monitoring layer

[0093] The contribution of fundamental harmonics is relatively small, and the cost-effectiveness of real-time suppression is extremely low, so they are monitored but not actively compensated for. However, if the high-frequency harmonics are close to or exceed the effective bandwidth of the controller, the response surface methodology is used for suppression.

[0094] See Figure 8 The radial electromagnetic force density of the motor before optimization under high-speed operating conditions. Figure 9 This represents the optimized radial electromagnetic force density of the motor under high-speed operating conditions. Compared to the initial design, the optimized design exhibits a smaller peak value and lower amplitude. Specifically, the average radial electromagnetic force density of the optimized design is 2.1 × 10⁻⁶. 4 N / m, less than the initial design value of 2.6 × 10 N / m. 5 N / m 2 .

[0095] See Figure 10 For low-speed torque characteristics, Figure 11 The optimized motor exhibits improved torque characteristics under high-speed conditions. Under low-speed conditions, the output torque increased from 45.6 Nm to 46.3 Nm. Compared to the initial design, the optimized motor torque ripple decreased by 0.8%. The optimized motor cogging torque is 1.1 Nm, a 69.4% reduction compared to the initial motor's 3.6 Nm. Under high-speed conditions, the initial motor's output torque is 7.2 Nm, while the optimized motor's output torque is 7.4 Nm, a 2.8% increase. Therefore, optimization improved the torque characteristics under different operating conditions, including average output torque, torque ripple, and cogging torque under low-speed conditions, as well as the output torque under high-speed conditions.

[0096] While some embodiments of the present general inventive concept have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A harmonic blocking alternating pole permanent magnet hub motor, the harmonic blocking alternating pole permanent magnet hub motor comprising a stator (2) and a rotor (1) sleeved outside the stator (2); The stator (2) has N circular closed slots (5) circumferentially opened inside the teeth, and a harmonic absorption ring (6) is embedded in the circular closed slot (5). Inside the rotor (1), there are g U-shaped grooves (7) with openings facing the air gap (13) and 2g arc-shaped two-section magnetic barriers (10) arranged in a staggered manner along the circumference. The U-shaped groove (7) includes two side arms and a transverse part connecting the tops of the two side arms. A bread-shaped permanent magnet (8) is embedded in the middle of the transverse part, and a rectangular permanent magnet (9) is embedded in the middle of the side arms. The arc-shaped two-segment magnetic barrier (10) is composed of two arc-shaped segments that are embedded on both sides of the side arm. In the arc-shaped two-segment magnetic barrier (10), the radius of curvature of the arc-shaped segment between the two side arms of the U-shaped groove (7) is R1, and the radius of curvature of the arc-shaped segment between each U-shaped groove (7) is R2, where R1 > R2. The rotor (1) has g magnetic barrier groups arranged circumferentially on the side near the air gap. Each magnetic barrier group includes two semi-elliptical magnetic barriers (11) and a parallelogram magnetic barrier (12) arranged between the two semi-elliptical magnetic barriers. The center line of the parallelogram magnetic barrier (12) is offset by an angle θ relative to the axis of the U-shaped groove (7). p Used to break magnetic circuit symmetry to suppress specific subharmonics, 1.5deg≤θ p ≤3deg; Offset angle θ p The design method is as follows: Based on the characteristic frequencies of the dominant harmonic group of the main oscillator, the magnetic flux density fluctuation curves of different frequency harmonics on the circumference of the motor are obtained. According to the spatial position / mechanical angle of the peaks and troughs, the peak values ​​of each frequency amplitude are marked as peak points, and the offset angle θ is obtained by single-parameter scanning. p .

2. The harmonic blocking alternating pole permanent magnet hub motor according to claim 1, characterized in that, The two arc-shaped segments of the arc-shaped two-segment magnetic barrier (10) have gaps between their corresponding side arms, which are used to increase the magnetic shielding effect.

3. The harmonic blocking alternating pole permanent magnet hub motor according to claim 2, characterized in that, The width of the gap is 0.5mm-1mm.

4. The harmonic blocking alternating pole permanent magnet hub motor according to claim 1, characterized in that, The harmonic absorption ring (6) is made of amorphous alloy or nanocrystalline soft magnetic composite material.

5. A method for differentiated vibration suppression of harmonic groups in a harmonic blocking alternating pole permanent magnet hub motor according to any one of claims 1-4, characterized in that, The harmonic group differential vibration suppression method includes the following steps: S1. Determine the range of values ​​for the structural parameters of the harmonic blocking alternating pole permanent magnet hub motor; S2. Actively identify the main vibration source under the current operating conditions and extract the characteristic frequencies of its dominant harmonic group; S3. Using the characteristic frequencies of the dominant harmonic group of the main source obtained in step S2 as the core optimization object, a multi-objective optimization method is adopted to obtain the Pareto front and its solution set under each working condition. The intersection of parameters under different working conditions is taken to select the parameter set with the best comprehensive performance.

6. The method for differentiated vibration suppression of harmonic groups according to claim 5, characterized in that, In step S2, the main vibration source in high-speed operation is radial electromagnetic force; Radial electromagnetic force density F r (θ,t) is shown in the following equation; ； In the formula, μ0 is the free permeability, and f PM (θ,t) represents the permanent magnet magnetomotive force, f ARM (θ,t) represents the armature magnetomotive force field, Λ s (θ) is the relative permeability of the stator, Λ r (θ,t) is the relative permeability of the rotor; F μ Let F be the magnetomotive force amplitude of the μth spatial harmonic. ν Let μp be the magnetomotive force amplitude of the νth spatial harmonic, μ = 2m + 1 (m = 0, 1, 2, ...), p be the number of rotor pole pairs, θ be the rotor mechanical angle, ω be the current angular frequency, and Λ0 be the average magnetic permeability. k Λ represents the amplitude of the k-th harmonic permeability of the stator, and Z represents the number of stator slots; i S is the amplitude of the i-th harmonic permeability of the rotor; ν The direction of rotation of the armature magnetic field harmonic ν is indicated by "1" and "-1" indicating forward and reverse rotation, respectively. α is the number of motor units, and να is the harmonic order of the armature magnetic field magnetomotive force.

7. The method for differentiated vibration suppression of harmonic groups according to claim 5, characterized in that, In step S2, the main vibration source under low-speed conditions is torque pulsation T. ripple and cogging torque T cog ; Torque pulsation T ripple With cogging torque T cog The relationship is shown in the following formula: ； ； In the formula, T pm It is the permanent magnet torque, T r It is the reluctance torque, T out-max It is the maximum torque, T out-min It is the minimum torque, T out-avg It is the average torque; B mn and G mn Here are the Fourier expansion coefficients, where B mn The Fourier coefficients of the toothed structure for magnetic permeability modulation are affected by the rotor pole distribution. mn The amplitude of the m-th spatial harmonic is obtained by Fourier decomposition of the air gap magnetic flux density in the radial direction. This is influenced by the stator slot distribution, where Z is the number of stator slots, and p... pm R is the number of pole pairs of the permanent magnet, l is the axial length, and R is the axial length. r It is the inner radius of the rotor, R s θ is the outer radius of the stator, and θ is the mechanical angle of the rotor. rt It is the circumferential angle of the rotor teeth, θ ss G1 is the circumferential angle between the stator slots and G2 is the permeability per unit area of ​​the stator tooth region.

8. The method for differentiated vibration suppression of harmonic groups according to claim 5, characterized in that, In step S2, the method for extracting the characteristic frequencies of the dominant harmonic group is as follows: Based on the main vibration source signal and the motor electrical signal, order analysis is performed using finite element software to analyze the vibration energy spectrum distribution corresponding to a specific speed and load under the current working condition in real time. Multiple peak frequency components with an energy proportion exceeding a set threshold are identified as the dominant harmonic group of the main oscillator, and their key characteristic frequencies are extracted as the characteristic frequencies of the dominant harmonic group.

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