A method for identifying modal parameters of a double-unit motor based on sideband harmonic excitation

Abstract

The application discloses a kind of based on sideband harmonic excitation's double-unit motor modal parameter identification method, belong to motor field.This method includes selecting the sideband harmonic current of preset frequency as vibration excitation source;Select the maximum speed of sideband harmonic current as test speed;Switching frequency sweep is carried out to double-unit motor to be measured, and the vibration acceleration data of each test point is obtained;Different phase shift angles are used to carry out carrier phase shift processing to sideband harmonic, and the vibration acceleration data of each test point in different order is obtained by repeating test step;Select multiple suspicious resonance points from vibration acceleration data;According to corresponding vibration acceleration data, mode shape analysis is carried out, and the spatial mode shape, vibration order and natural frequency of real resonance point are confirmed;According to real resonance point, frequency response function is constructed, and the modal parameter of double-unit motor to be measured is extracted from it.The modal parameter identification of low cost, high excitation energy and wide frequency range is realized.

Description

Technical Field

[0001] This invention belongs to the field of electric motors, and more specifically, relates to a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation and a motor vibration measurement system. Background Technology

[0002] Dual-unit surface-mount permanent magnet synchronous motors consist of two spatially independent three-phase windings. Due to their advantages such as power sharing, fault-tolerant operation, and relatively simple control strategies, they are increasingly widely used in high-power applications. For dual-unit motors, the effectiveness of carrier phase shifting in suppressing high-frequency vibrations is highly sensitive to the motor's modal characteristics. Therefore, modal analysis is a crucial prerequisite for accurately predicting and suppressing high-frequency vibrations.

[0003] The hammer impact modal test is the most commonly used modal testing method. This method collects vibration signals generated by multiple impacts from a vibrating hammer on multiple circumferentially evenly arranged accelerometers. After frequency domain synthesis processing by a vibration recorder, the comprehensive vibration response function of the motor can be accurately obtained. However, this method still has the following limitations: First, the experimental platform requires high construction costs and the operation steps are relatively complex; second, the effective excitation bandwidth of the vibrating hammer is determined by the hammer head material and the bandwidth of the hammer head force sensor, and its pulse excitation energy is mainly concentrated in the low and medium frequency range, making it difficult to excite and identify high-frequency modes; third, it is difficult to ensure the consistency of impact force, direction, and point of impact by manual impact, which can easily lead to local response, secondary impact, and overload problems. Multiple impacts are required to reduce human error and increase the signal-to-noise ratio, further increasing the complexity of the experimental operation.

[0004] Electromagnetic excitation is a feasible method for modal testing, which can be categorized into external excitation and internal excitation methods based on whether the excitation source is intrinsic to the motor. Existing external excitation methods require an additional inverter outside the motor as the excitation source, in addition to the inverter driving the motor, resulting in complex equipment. Current internal excitation methods use the low-order slot frequency electromagnetic force due to rotor eccentricity as the excitation source. However, since the slot harmonic amplitude depends on the degree of rotor eccentricity, insufficient excitation energy leads to a small measured response signal amplitude, making it difficult to accurately identify modal parameters. Furthermore, this method is easily limited by motor speed, resulting in a narrow measurement frequency range.

[0005] The aim is to address the problems of conventional scale testing methods, which can only measure low frequencies, are costly, and have large errors. Summary of the Invention

[0006] In view of the shortcomings of related technologies, the purpose of this invention is to provide a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation, which aims to solve the problems of high cost, insufficient excitation energy and small measurement frequency band of existing modal testing methods.

[0007] To achieve the above objectives, the present invention provides a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation, comprising:

[0008] S100. Select a sideband harmonic current of a preset frequency as the vibration excitation source of the dual-unit motor under test; select the rotational speed at which the sideband harmonic current is maximized as the test rotational speed.

[0009] S200. Under the vibration excitation source and test speed, the switching frequency of the dual-unit motor under test is swept to obtain the vibration acceleration data of each test point of the motor.

[0010] S300: Perform carrier phase shifting processing on the sideband harmonic current corresponding to the vibration excitation source, update the vibration excitation source, and repeat step S200 to obtain the vibration acceleration data of each test point at different orders of the motor.

[0011] S400: Select the frequency points corresponding to the peaks of the vibration acceleration spectrum from the vibration acceleration data to obtain multiple suspected resonance points; perform mode shape analysis on the dual-unit motor under test based on the vibration acceleration data of each suspected resonance point to confirm the spatial mode shape, vibration order and natural frequency of the real resonance point.

[0012] S500. Arrange the real resonance points in ascending order, connect the vibration amplitude points of different real resonance points, construct a frequency response function based on the preset electromagnetic force wave density, and extract the modal parameters of the dual-unit motor under test from it.

[0013] Optionally, step S100 includes:

[0014] S110. During the operation of the dual-unit motor under test, the sideband harmonic current generated by the interaction between the sideband harmonic generated by the PWM of the measurement controller and the magnetic field of the dual-unit motor under test is measured. The sideband harmonic current is subjected to fast Fourier transform to calculate and solve the main high-frequency electromagnetic force waves in the dual-unit motor under test.

[0015] S120. Analyze the frequency components of the main high-frequency electromagnetic force waves within the single unit, from... f s ± f 1. f s ±3 f 1, 2 f s and 2 f s ±2 f One frequency is selected as the vibration excitation source, using an electromagnetic force wave of any frequency; where, f s This refers to the carrier frequency, i.e., the switching frequency. f1 represents the fundamental frequency, which is the input frequency of the power supply;

[0016] S130. Select the speed of the dual-unit motor under test when the harmonic current is at its maximum as the test speed. Optionally, step S200 includes:

[0017] S210. Apply the vibration excitation source to the dual-unit motor under test, and fix the rotational speed of the dual-unit motor under test to the test rotational speed;

[0018] S220. Starting from a low frequency, gradually change the switching frequency of the dual-unit motor under test at fixed intervals Δf, test and record the vibration response acceleration data of the dual-unit motor under test; when the vibration response acceleration increases sharply, reduce the interval Δf.

[0019] S230. Measure the vibration acceleration data of the dual-unit motor under test at each test point corresponding to the current vibration excitation source.

[0020] Optionally, step S300 includes:

[0021] S310. According to the preset phase shift angle, perform carrier phase shift processing on the sideband harmonic current corresponding to the vibration excitation source and update the vibration excitation source.

[0022] S320. When the phase shift angle takes different values, repeat the test steps of S200 to obtain the vibration acceleration spectrum of each test point of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources.

[0023] Optionally, step S400 includes:

[0024] S410. By using the modal superposition method, the vibration acceleration spectra of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources are superimposed. From the superimposed vibration acceleration spectrum, the frequency points corresponding to the peaks of the vibration acceleration spectrum are selected to obtain multiple suspected resonance points.

[0025] S420. Using working deformation analysis technology, analyze multiple suspected resonance points, match the spatial mode shapes corresponding to different vibration orders with the suspected resonance points, confirm the real resonance points among the multiple suspected resonance points, and obtain the spatial mode shapes and vibration orders corresponding to each real resonance point.

[0026] S430. Confirm that the frequency of the spectral peak corresponding to the true resonance point is the natural frequency of the dual-unit motor under test.

[0027] Optionally, step S500 includes:

[0028] S510. Arrange the resonance points in ascending order, connect the vibration amplitude points of different resonance points, and select a preset electromagnetic force wave density to construct the frequency response function of the dual-unit motor under test.

[0029] S520. Analyze the frequency response function and extract the damping ratio and amplitude of the dual-unit motor under test.

[0030] In a second aspect, the present invention also provides a motor vibration measurement system for performing the modal parameter identification method for a dual-unit motor based on sideband harmonic excitation as described in any one of the first aspects, comprising: a controller, an acceleration sensor, a vibration signal acquisition device, and a dual-unit motor under test;

[0031] The acceleration sensor is arranged in the circumferential position in the middle of the housing of the dual-unit motor under test, and is used to acquire vibration acceleration data at each test point at the test speed.

[0032] The controller is connected to the dual-unit motor under test and is used to select a sideband harmonic current of a preset frequency as the vibration excitation source and select the speed at which the sideband harmonic current of the motor is maximized as the test speed.

[0033] The controller is also used to set the dual-unit motor under test according to the vibration excitation source and the test speed, perform modal testing on it, and change the vibration excitation source to perform modal testing under different excitation sources;

[0034] The vibration signal acquisition device is connected to the acceleration sensor and is used to process the vibration acceleration data of each test point when the motor uses electromagnetic force waves of different orders as vibration excitation sources to obtain the modal parameters of the dual-unit motor under test.

[0035] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0036] 1. This invention provides a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation. It utilizes high-frequency electromagnetic force as the internal excitation source of the motor. The frequency characteristics of the high-frequency electromagnetic force are determined by the frequency of the sideband harmonic current, which can be precisely controlled over a wide frequency range by changing the switching frequency. Simultaneously, the carrier phase shift angle determines the spatial distribution characteristics of the electromagnetic force. Testing is conducted using electromagnetic force waves of different orders as vibration excitation sources to obtain vibration acceleration data of different orders. In this scheme, by modifying the switching frequency and the carrier phase shift angle, frequency sweep excitation over a wide frequency range can be achieved for the motor, thereby obtaining the motor's modal parameters based on the vibration response data. This solves the problems of high cost, insufficient excitation energy, and limited measurement frequency band in existing modal testing methods. It achieves low-cost, high-excitation-energy, and wide-frequency-range modal parameter identification.

[0037] 2. The present invention provides a method for identifying the modal parameters of a dual-unit motor based on sideband harmonic excitation. The test equipment is simple, and the high-frequency sideband harmonics of the inverter itself are used as the excitation source. No additional test equipment (such as a hammer or an additional inverter) is introduced. The vibration amplitude of the excited motor is controlled, and the frequency range of the excitation is large. Attached Figure Description

[0038] Figure 1 This is a schematic flowchart of a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation provided in an embodiment of the present invention;

[0039] Figure 2 This is a diagram showing the effect of carrier shift on the order of electromagnetic force.

[0040] Figure 3 These are the vibration sweep frequency curves of the 12s10p motor without carrier phase shift, at the 2nd and 4th order.

[0041] Figure 4 This is the vibration sweep frequency curve of a 12s10p motor without carrier phase shift, 0th order experimental vibration.

[0042] Figure 5 These are the vibration sweep frequency curves of a 12s10p motor with 90° carrier phase shift, first and third order.

[0043] Figure 6 These are the vibration sweep frequency curves of a 12s10p motor with 180° carrier phase shift, first and third order.

[0044] Figure 7 It is the first-order experimental frequency response function after fitting and averaging of the 12s10p motor;

[0045] Figure 8 It is the second-order experimental frequency response function after fitting and averaging of the 12s10p motor;

[0046] Figure 9 It is the third-order experimental frequency response function after fitting and averaging of the 12s10p motor;

[0047] Figure 10 It is the fourth-order experimental frequency response function after fitting and averaging of the 12s10p motor. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0050] Example 1

[0051] This invention provides a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation, comprising:

[0052] S100. Select a sideband harmonic current of a preset frequency as the vibration excitation source of the dual-unit motor under test; select the rotational speed at which the sideband harmonic current is maximized as the test rotational speed.

[0053] S200. Under the vibration excitation source and test speed, the switching frequency of the dual-unit motor under test is swept to obtain the vibration acceleration data of each test point of the motor.

[0054] S300: Perform carrier phase shifting processing on the sideband harmonic current corresponding to the vibration excitation source, update the vibration excitation source, and repeat step S200 to obtain the vibration acceleration data of each test point at different orders of the motor.

[0055] S400: Select the frequency points corresponding to the peaks of the vibration acceleration spectrum from the vibration acceleration data to obtain multiple suspected resonance points; perform mode shape analysis on the dual-unit motor under test based on the vibration acceleration data of each suspected resonance point to confirm the spatial mode shape, vibration order and natural frequency of the real resonance point.

[0056] S500: Select the frequency point corresponding to the peak of the vibration acceleration spectrum from the vibration acceleration data to obtain multiple suspected resonance points; perform mode shape analysis on the dual-unit motor under test based on the vibration acceleration data of each suspected resonance point to confirm the spatial mode shape, vibration order and natural frequency of the real resonance point.

[0057] The specific steps include: selecting a suitable high-frequency electromagnetic excitation source; determining the specific operating conditions for the motor experimental test and finding a suitable fixed speed for modal testing; performing frequency sweeping at the switching frequency to measure the vibration of the motor at different switching frequencies, obtaining the vibration distribution of some orders of the motor, and refining the frequency sweeping near the natural frequency; repeating the above steps after shifting the carrier phase to remove the motor vibration sources of other orders; performing operational deformation shape (ODS) analysis on each suspected resonance point to confirm the spatial mode shape of each resonance point and verify the predicted vibration order; and fitting the experimental results to construct a frequency response function (FRF) to extract the modal parameters of the motor.

[0058] Optionally, step S100 includes:

[0059] S110. During the operation of the dual-unit motor under test, the sideband harmonic current generated by the interaction between the sideband harmonic generated by the PWM of the measurement controller and the magnetic field of the dual-unit motor under test is measured. The sideband harmonic current is subjected to fast Fourier transform to calculate and solve the main high-frequency electromagnetic force waves in the dual-unit motor under test.

[0060] S120. Analyze the frequency components of the main high-frequency electromagnetic force waves within the single unit, and select... f s ± f 1. f s ±3 f 1, 2 f s and 2 f s ±2 f Electromagnetic force waves of frequency 1 are used as the vibration excitation source; among which, f s This refers to the carrier frequency, i.e., the switching frequency. f 1 represents the fundamental frequency, which is the input frequency of the power supply;

[0061] S130. Select the speed of the dual-unit motor under test when the harmonic current is at its maximum as the test speed.

[0062] In this embodiment, a dual-unit permanent magnet synchronous motor is used. For a PWM-modulated dual-unit permanent magnet synchronous motor, the sideband harmonic current generated by the PWM interacts with the magnetic field of the permanent magnet, producing a sideband electromagnetic force that ultimately interacts with the motor modes, resulting in significant high-frequency vibration. A fixed-frequency sideband harmonic induces a fixed-order electromagnetic force, thereby exciting modal vibration. There is a one-to-one correspondence between these three factors; therefore, the motor modal vibration can be excited based on the sideband harmonics.

[0063] According to Maxwell's stress tensor method, under the action of the sideband harmonic current generated by PWM, the dual-unit surface-mounted permanent magnet synchronous motor at ω... m,n The radial component σ of the electromagnetic force wave at a given frequency rx (ω m,n It can be approximated as:

[0064] (1)

[0065] Where v is the spatial order of the armature magnetomotive force in the unit motor. The number of unit motors is equal to the number of motor pole pairs. p With the number of slots z The greatest common divisor, θ The mechanical angle of the motor rotation. Λ 0 represents the air gap magnetic flux density. s n,vThe direction of rotation of the armature magnetomotive force, the first x ( x =1,2) The amplitude of the element sideband harmonic current and the current component in the opposite phase sequence to the excitation voltage are 1,2) Phase is , The radial magnetomotive force amplitude coefficient can be obtained by solving the boundary conditions of the motor's magnetic field or by finite element simulation. It is the magnetomotive force of the permanent magnet.

[0066] The tangential component of the electromagnetic force wave can be expressed as:

[0067] (2)

[0068] High-frequency electromagnetic force waves in a dual-unit surface-mount permanent magnet synchronous motor across the entire motor range σ (ω m,n It can be written as:

[0069] (3)

[0070] Based on the sideband harmonic current components of the dual-unit surface-mounted permanent magnet synchronous motor, substituting them into the above formula yields the main high-frequency electromagnetic force wave components and orders of a single unit in the dual-unit surface-mounted permanent magnet synchronous motor. The sideband harmonic current frequency component with the largest proportion is selected as the vibration excitation source.

[0071] In one specific embodiment, a 12s10p motor is used, and the parameters are shown in Table 1 below.

[0072] Table 1

[0073]

[0074] During motor operation, the motor current is measured using an oscilloscope to identify the main sideband harmonic current frequency components and perform harmonic modeling analysis. Based on the sideband harmonic current components of the dual-unit surface-mount permanent magnet synchronous motor, the main high-frequency electromagnetic force wave components and orders of a single unit in the dual-unit surface-mount permanent magnet synchronous motor can be obtained by substituting them into equations (1) to (3).

[0075] Through derivation, the main high-frequency electromagnetic force frequency components within a single unit of the dual-unit surface-mount permanent magnet synchronous motor prototype are concentrated in the following frequency range. f s ± f 1. 2f s ± f 1. f s ±2f 1. f s ±3 f 1. fs ±5 f 1, 2 f s 2 f s ±4 f 1 and 2 f s ±6 f 1. All of the above components can serve as vibration excitation sources; however, due to sideband harmonic currents... f s ±2 f 1 and 2 f s ± f The frequency component 1 is the most significant. Therefore, f s ± f 1. f s ±3 f 1, 2 f s and 2 f s ±2 f Electromagnetic force at frequency 1 is the optimal source of vibration excitation. Without carrier phase shift, the 0th and 2nd order vibrations of the motor are more pronounced.

[0076] Since this test method uses a fixed rotational speed for measurement, it is necessary to select an appropriate test speed for the motor. Theoretically, modal testing can be performed at any rotational speed, but in order to highlight the vibration characteristics of the resonance point and reduce measurement errors, the optimal operating speed should be selected when the sideband harmonic current is relatively large, so as to ensure that the electromagnetic force of excitation and the vibration amplitude are large.

[0077] The operating speed for motor testing should be selected when the motor's low-order vibrations (first and second orders) are relatively large. Using an oscilloscope, the sideband current variation with speed is obtained. Then, a Fast Fourier Transform (FFT) is performed on the motor's sideband current, and the speed value where the first and second order current components are larger is selected. From the sideband current variation with speed, it can be seen that the first-order sideband current gradually increases with increasing speed, while the second-order sideband current first increases and then decreases. To ensure that the sideband current is as large as possible, the inflection point of the second-order sideband current change, 720 rpm, is selected to ensure that the first and second order sideband currents are at their maximum. This speed is chosen as the test speed, that is, the speed at which the motor's harmonic current is at its maximum.

[0078] Optionally, step S200 includes:

[0079] S210. Apply the vibration excitation source to the dual-unit motor under test, and fix the rotational speed of the dual-unit motor under test to the test rotational speed;

[0080] S220. Starting from a low frequency, gradually change the switching frequency of the dual-unit motor under test at fixed intervals Δf, test and record the vibration response data of the dual-unit motor under test; when the switching frequency is close to the natural frequency, reduce the interval Δf to improve the measurement resolution.

[0081] S230. Measure the vibration acceleration data of the dual-unit motor under test at each test point corresponding to the current vibration excitation source.

[0082] Vibration sensors are used to measure the vibration of a motor during operation. The acceleration data from the vibration sensors reflects the electromagnetic vibration of the motor. Specifically, the motor stator is subjected to electromagnetic force, which causes electromagnetic vibration. Vibration sensors are used to collect the vibration acceleration signal on the surface of the motor stator, process and record the motor vibration amplitude at the sideband harmonic frequency. When the frequency and order of the electromagnetic force are close to the natural frequency and mode shape of the motor, resonance will occur.

[0083] The test should begin at a low frequency, gradually changing the motor's switching frequency at fixed intervals Δf, and recording the motor's vibration response using a vibration measurement system. When the excitation frequency approaches the natural frequency, the Δf interval should be reduced to improve measurement resolution. Specifically, a fixed test speed is used, scanning begins at 1 kHz and ends at 10 kHz, with a standard switching frequency interval of 0.25 kHz, and densified to 0.1 kHz intervals near the resonance point. Figure 3 and Figure 4 As shown, without carrier phase shift, FFT processing is performed on the vibration results to obtain the vibration acceleration data of the motor at the 0th, 2nd and 4th orders, i.e., the vibration spectrum.

[0084] Optionally, step S300 includes:

[0085] S310. According to the preset phase shift angle, perform carrier phase shift processing on the sideband harmonic current corresponding to the vibration excitation source and update the vibration excitation source.

[0086] S320. When the phase shift angle takes different values, repeat the test steps of S200 to obtain the vibration acceleration spectrum of each test point of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources.

[0087] like Figure 2As shown, carrier phase shift significantly alters the distribution of sideband harmonic currents, thus affecting the order of the electromagnetic force. For integer-slot permanent magnet synchronous motors, the sideband harmonic electromagnetic force primarily excites 0th and 2p-order motor vibrations in space. For dual-unit motors (p=1), the sideband harmonics mainly cause 0th, 2nd, and 4th-order vibrations. Based on the structural symmetry of dual-unit motors, carrier phase shift can effectively control the order of the electromagnetic force. Theoretical analysis shows that when the carrier phase shift angle of the two windings is set to 180°, the original nth-order electromagnetic force component will be completely converted into n±1, n±3, and n±5 order harmonic components. Furthermore, if the carrier phase shift angle is set to... Then the harmonic phase shift angle near the m-th carrier is also m. Carrier phase shifting converts even-order electromagnetic forces into odd-order vibration components, thereby broadening the test frequency band and improving measurement accuracy. Therefore, by adjusting the carrier phase shift angle and repeating the test steps, modal information of other orders of the motor can be further obtained.

[0088] Specifically, regarding the vibrations of the motor at the 1st, 3rd, and 5th orders, such as Figure 5 As shown, when the phase shift angle is 90°, the harmonics around the twice-carrier frequency can be used as the excitation source. By repeating the above test steps, the first-order and third-order vibration spectra can be obtained. Figure 6 As shown, when the phase shift angle is 180°, the harmonics around the carrier frequency can be used as the excitation source. By repeating the above test steps, the first-order and third-order vibration spectra can be obtained.

[0089] Optionally, step S400 includes:

[0090] S410. By using the modal superposition method, the vibration spectra of each test point of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources are superimposed. From the superimposed vibration acceleration spectrum, the frequency points corresponding to the peaks of the vibration acceleration spectrum are selected to obtain multiple suspected resonance points.

[0091] S420. The working deformation analysis technology is used to analyze multiple suspected resonance points. The spatial mode shapes corresponding to different vibration orders are matched with the suspected resonance points to confirm the real resonance points among the multiple suspected resonance points, and the spatial mode shapes and vibration orders corresponding to each real resonance point are obtained.

[0092] S430. Confirm that the frequency of the spectral peak corresponding to the true resonance point is the natural frequency of the dual-unit motor under test.

[0093] The vibration spectra of the dual-unit motor under test at each test point are superimposed. The frequency points corresponding to the peaks of the vibration acceleration spectrum obtained in the above steps are selected as suspected resonance frequencies. The mode shapes of each resonance point are analyzed using working deformation analysis technology, thereby verifying the modal order corresponding to each resonance point. For each suspected resonance frequency, the vibration mode shape at that frequency is extracted. The mode shape is observed to determine the order of the resonance point. The true resonance points among multiple suspected resonance points are confirmed, and the spatial mode shape, vibration order, and natural frequency corresponding to each true resonance point are obtained to ensure the correctness of the modal parameters.

[0094] Optionally, step S500 includes:

[0095] S510. Arrange the resonance points in ascending order, connect the vibration amplitude points of different resonance points, and select a preset electromagnetic force wave density to construct the frequency response function of the dual-unit motor under test.

[0096] S520. Analyze the frequency response function and extract the damping ratio and amplitude of the dual-unit motor under test.

[0097] In the experimental data processing stage, the resonant points were arranged in ascending order, and the vibration amplitude points of different resonant points were connected. A specific electromagnetic force density was selected, and the spectrum diagrams of each order were fitted to calculate the frequency response function (FRF) of the motor. Through FRF analysis, key modal parameters such as the motor's natural frequency, damping ratio, and amplitude can be further extracted, thereby achieving a comprehensive measurement of the motor's modal characteristics.

[0098] Generally, motor modal parameters include natural frequency, mode shape, damping ratio, and amplitude. The natural frequency can be directly identified from the resonance point, while the mode shape is given by ODS analysis. For example... Figure 7 As shown, to reduce experimental error, the results were fitted with an electromagnetic force density of 100 to obtain the FRF. The amplitude was extracted, and then the damping ratio was obtained using the half-power bandwidth method.

[0099] Traditional hammer-driven modal measurement systems are costly and have limited excitation capabilities at high frequencies. Compared to traditional testing methods, this method eliminates the need for manual hammer strikes, requiring only electromagnetic excitation and vibration response measurement. This expands the modal identification bandwidth and reduces operational requirements compared to hammer-driven testing. Furthermore, compared to existing electromagnetic excitation methods based on rotor eccentricity, this method uses inverter control as the excitation source, independent of the specific motor structure, thus offering wider applicability and versatility. It provides a clearer understanding of the electromagnetic vibration monitoring principle based on sideband harmonics, resulting in a wider testing range and higher accuracy. Table 2 compares the high-frequency electromagnetic force sweep modal identification results with the hammer-driven modal experimental results.

[0100] Table 2

[0101]

[0102] In this embodiment, by modifying the switching frequency and carrier phase shift angle, frequency sweep excitation over a wide frequency range can be achieved in the motor, thereby obtaining the motor's modal parameters based on the vibration response. This enables accurate extraction of modal parameters, providing a reliable theoretical basis and experimental support for the motor's vibration analysis and optimized design.

[0103] Example 2

[0104] The present invention also provides a motor vibration measurement system for performing the modal parameter identification method for a dual-unit motor based on sideband harmonic excitation as described in any one of Embodiments 1, comprising: a controller, an acceleration sensor, a vibration signal acquisition device, and a dual-unit motor under test;

[0105] The acceleration sensor is arranged in the circumferential position in the middle of the housing of the dual-unit motor under test, and is used to acquire vibration acceleration data at each test point at the test speed.

[0106] The controller is connected to the dual-unit motor under test and is used to select a sideband harmonic current of a preset frequency as the vibration excitation source and select the speed at which the sideband harmonic current of the motor is maximized as the test speed.

[0107] The controller is also used to set the dual-unit motor under test according to the vibration excitation source and the test speed, perform modal testing on it, and change the vibration excitation source to perform modal testing under different excitation sources;

[0108] The vibration signal acquisition device is connected to the acceleration sensor and is used to process the vibration acceleration data of each test point when the motor uses electromagnetic force waves of different orders as vibration excitation sources to obtain the modal parameters of the dual-unit motor under test.

[0109] If only the natural frequency of the motor needs to be measured, there are no requirements regarding the number and placement of the acceleration sensors. In this design, for a standard motor housing model, at least eight acceleration sensors should be arranged circumferentially in the middle of the housing.

[0110] The motor vibration measurement system provided in this embodiment of the invention performs a method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation, and has the same beneficial effects.

[0111] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying modal parameters of a dual-unit motor based on sideband harmonic excitation, characterized in that, include: S100. Select a sideband harmonic current of a preset frequency as the vibration excitation source of the dual-unit motor under test. The rotational speed at which the sideband harmonic current is maximized is selected as the test rotational speed. S200. Under the vibration excitation source and test speed, the switching frequency of the dual-unit motor under test is swept to obtain the vibration acceleration data of each test point of the motor. S300: Perform carrier phase shifting processing on the sideband harmonic current corresponding to the vibration excitation source, update the vibration excitation source, and repeat step S200 to obtain the vibration acceleration data of each test point at different orders of the motor. S400: Select the frequency points corresponding to the peaks of the vibration acceleration spectrum from the vibration acceleration data to obtain multiple suspected resonance points; perform mode shape analysis on the dual-unit motor under test based on the vibration acceleration data of each suspected resonance point to confirm the spatial mode shape, vibration order and natural frequency of the real resonance point. S500. Arrange the real resonance points in ascending order, connect the vibration amplitude points of different real resonance points, construct the frequency response function based on the preset electromagnetic force wave density, and extract the modal parameters of the dual-unit motor under test from it. Step S100 includes: S110. During the operation of the dual-unit motor under test, the sideband harmonic current generated by the interaction between the sideband harmonic generated by the PWM of the measurement controller and the magnetic field of the dual-unit motor under test is measured. The sideband harmonic current is subjected to fast Fourier transform to calculate and solve the main high-frequency electromagnetic force waves in the dual-unit motor under test. S120. Analyze the frequency components of the main high-frequency electromagnetic force waves within a single unit, from... f s ± f 1. f s ±3 f 1, 2 f s and 2 f s ±2 f One frequency is selected as the vibration excitation source, using an electromagnetic force wave of any frequency; where, f s This refers to the carrier frequency, i.e., the switching frequency. f 1 represents the fundamental frequency, which is the input frequency of the power supply; S130. Select the speed of the dual-unit motor under test when the harmonic current is at its maximum as the test speed.

2. The method as described in claim 1, characterized in that, Step S200 includes: S210. Apply the vibration excitation source to the dual-unit motor under test, and fix the rotational speed of the dual-unit motor under test to the test rotational speed; S220. Starting from a low frequency, gradually change the switching frequency of the dual-unit motor under test at fixed intervals Δf, test and record the vibration response acceleration data of the dual-unit motor under test; when the vibration response acceleration increases sharply, reduce the interval Δf. S230. Measure the vibration acceleration data of the dual-unit motor under test at each test point corresponding to the current vibration excitation source.

3. The method as described in claim 1, characterized in that, Step S300 includes: S310. According to the preset phase shift angle, perform carrier phase shift processing on the sideband harmonic current corresponding to the vibration excitation source and update the vibration excitation source. S320. When the phase shift angle takes different values, repeat the test steps of S200 to obtain the vibration acceleration spectrum of each test point of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources.

4. The method as described in claim 3, characterized in that, Step S400 includes: S410. By using the modal superposition method, the vibration acceleration spectra of the dual-unit motor under test when electromagnetic force waves of different orders are used as vibration excitation sources are superimposed. From the superimposed vibration acceleration spectrum, the frequency points corresponding to the peaks of the vibration acceleration spectrum are selected to obtain multiple suspected resonance points. S420. Using working deformation analysis technology, analyze multiple suspected resonance points, match the spatial mode shapes corresponding to different vibration orders with the suspected resonance points, confirm the real resonance points among the multiple suspected resonance points, and obtain the spatial mode shapes and vibration orders corresponding to each real resonance point. S430. Confirm that the frequency of the spectral peak corresponding to the true resonance point is the natural frequency of the dual-unit motor under test.

5. The method as described in claim 4, characterized in that, Step S500 includes: S510. Arrange the resonance points in ascending order, connect the vibration amplitude points of different resonance points, and select a preset electromagnetic force wave density to construct the frequency response function of the dual-unit motor under test. S520. Analyze the frequency response function and extract the damping ratio and amplitude of the dual-unit motor under test.

6. A motor vibration measurement system, used to perform the modal parameter identification method for a dual-unit motor based on sideband harmonics as described in any one of claims 1-5, characterized in that, include: Controller, vibration acceleration sensor, vibration signal acquisition device, and dual-unit motor under test; The acceleration sensor is arranged in the circumferential position in the middle of the housing of the dual-unit motor under test, and is used to acquire vibration acceleration data at each test point at the test speed. The controller is connected to the dual-unit motor under test and is used to select a sideband harmonic current of a preset frequency as the vibration excitation source and select the speed at which the sideband harmonic current of the motor is maximized as the test speed. The controller is also used to set the dual-unit motor under test according to the vibration excitation source and the test speed, perform modal testing on it, and change the vibration excitation source to perform modal testing under different excitation sources. The vibration signal acquisition device is connected to the acceleration sensor and is used to process the vibration acceleration data of each test point when the motor uses electromagnetic force waves of different orders as vibration excitation sources to obtain the modal parameters of the dual-unit motor under test.

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