A method and apparatus for eliminating natural vibration noise of a laser Doppler vibration meter

Abstract

This invention provides a method and apparatus for eliminating self-vibration noise in a laser Doppler vibrometer. The method includes: measuring the vibration signal of the object under test and the vibration signal of the instrument itself (the instrument being a laser Doppler vibrometer); calculating the vibration velocity of the object under test containing noise based on the vibration signal of the object under test; calculating the vibration velocity of the instrument itself based on the vibration signal of the instrument itself; and calculating the noise-reduced vibration velocity of the object under test based on the vibration velocity of the object under test containing noise and the vibration velocity of the instrument itself. This invention, by adding a reflector and a beam splitter to the laser Doppler vibrometer, measures and corrects for the instrument's own vibration, effectively eliminating measurement errors caused by the influence of instrument self-vibration, and providing technical support for obtaining higher-precision remote sensing vibration monitoring data in the field.

Description

Technical Field

[0001] This invention relates to the field of laser vibration measurement technology, and in particular to a method and apparatus for eliminating the self-vibration noise of a laser Doppler vibration meter. Background Technology

[0002] Vibration analysis and modal analysis are crucial components in wind turbine fault detection and wind tower stability testing. Vibration parameters reflect the overall structural safety factor and performance variations of the wind turbine. Due to the complex structure of large wind turbines, fault information is often obscured by other data. Therefore, accurately obtaining the true vibration parameters of the target is a critical issue in this field.

[0003] When using a laser Doppler vibrometer to measure the micro-vibration parameters of a target, the influence of environmental noise and instrument self-vibration noise can cause the target vibration data to be covered by environmental vibration. In addition, the echo signal may be submerged in environmental noise or may not contain Doppler signal, which further increases the difficulty of obtaining accurate on-site measurement data.

[0004] Traditional laser Doppler vibrometers inevitably carry the instrument's own vibration information with the incident light during emission. Traditional vibration measurement principles do not consider interference with the incident light, which means that the processing of the Doppler signal is also affected by interference from the instrument's own vibration. Furthermore, Doppler signal processing methods use Fast Fourier Transform (FFT) for frequency domain conversion, and the accuracy of the frequency domain conversion is determined by the sampling frequency and the number of sampling points. According to the Nyquist sampling theorem, a larger number of sampling points N yields more accurate and characteristic results. However, in actual measurements, a larger number of sampling points also means more interference signals from the instrument's own vibration. While this ensures frequency resolution, the influence of environmental vibrations also interferes with the measurement results. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method and apparatus for eliminating the self-vibration noise of a laser Doppler vibration meter, thereby solving the technical problem that the measurement accuracy of laser Doppler vibration measurement equipment is affected by the instrument's self-vibration in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] On the one hand, a method for eliminating the self-vibration noise of a laser Doppler vibration meter is provided, including the following steps:

[0008] The instrument measures the vibration signal of the object under test and the vibration signal of the instrument itself; the instrument refers to a laser Doppler vibration meter.

[0009] Calculate the vibration velocity of the object containing noise based on the vibration signal of the object being measured.

[0010] Calculate the instrument's own vibration velocity based on its own vibration signal;

[0011] The noise-reduced vibration velocity of the test object is calculated based on the vibration velocity of the noisy object and the vibration velocity of the instrument itself.

[0012] Preferably, the measurement of the vibration signal of the object under test and the vibration signal of the instrument itself includes:

[0013] A reflector and a beam splitter are installed inside the laser Doppler vibrometer. The emitted laser light is split into two optical paths after passing through the beam splitter. One optical path is focused on the surface of the object being measured to measure the vibration signal of the object. The other optical path is focused on the outer shell of the laser Doppler vibrometer. The reflector sends the laser light reflected from the outer shell through the beam splitter into the receiver to measure the vibration signal of the instrument itself.

[0014] Preferably, the calculation of the vibration velocity of the measured object containing noise includes:

[0015] The frequency f of the light reflected by the noisy object under test r The calculation formula is:

[0016]

[0017] Among them, f r λ0 is the frequency of the light reflected by the noisy object, f0 is the wavelength, v is the frequency of the incident light, and v is the vibration velocity of the noisy object.

[0018] Frequency shift f of reflected light from a noisy object D The calculation formula is:

[0019]

[0020] Among them, f D The frequency shift of the light reflected from the noisy object being tested;

[0021] The formula for calculating the vibration velocity v of the noisy object being measured is:

[0022]

[0023] Preferably, the vibration velocity of the computing instrument itself includes:

[0024] The frequency f of the reflected light from the instrument r ’ The calculation formula is:

[0025]

[0026] Among them, f r ’v is the frequency of the reflected light from the instrument. d The vibration velocity of the instrument;

[0027] The frequency shift f of the reflected light from the instrument D ’ The calculation formula is:

[0028]

[0029] Among them, f D ’ This refers to the frequency shift of the reflected light from the instrument.

[0030] The vibration velocity v of the instrument itself d The calculation formula is:

[0031]

[0032] Preferably, the calculation of the denoised vibration velocity of the measured object includes:

[0033] The noise-reduced vibration velocity v of the measured object t The calculation formula is:

[0034]

[0035] Where v is the vibration velocity of the measured object containing noise, v d v is the vibration velocity of the instrument. t The vibration velocity of the object being measured after noise reduction.

[0036] On the other hand, a self-vibration noise cancellation device for a laser Doppler vibration meter is provided, comprising:

[0037] The measurement module is used to measure the vibration signal of the object under test and the vibration signal of the instrument itself, wherein the instrument refers to a laser Doppler vibration meter;

[0038] The first calculation module is used to calculate the vibration velocity of the object under test, including the vibration signal.

[0039] The second calculation module is used to calculate the instrument's own vibration velocity based on the instrument's own vibration signal.

[0040] The third calculation module is used to calculate the denoised vibration velocity of the test object based on the vibration velocity of the noisy test object and the vibration velocity of the instrument itself.

[0041] On the other hand, an electronic device is provided, comprising a processor and a memory, wherein the memory stores at least one instruction, which is loaded and executed by the processor to implement the above-described method for eliminating the self-vibration noise of a laser Doppler vibrometer.

[0042] On the other hand, a computer-readable storage medium is provided, wherein at least one instruction is stored in the storage medium, the at least one instruction being loaded and executed by a processor to implement the above-described method for eliminating the self-vibration noise of a laser Doppler vibrometer.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0044] This invention adds a reflector and a beam splitter to a laser Doppler vibration meter to measure and correct the instrument's own vibration, effectively eliminating measurement errors caused by the instrument's own vibration and providing technical support for obtaining higher-precision remote sensing vibration monitoring data in the field. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the self-vibration noise elimination method of the laser Doppler vibration meter provided by the present invention;

[0047] Figure 2 This is a schematic diagram of the experimental model provided in the embodiments of the present invention;

[0048] Figure 3 It is a time-domain comparison graph of the measurement results of the traditional system, the measurement results of the optimized system, and the actual vibration signal (collected by the vibration sensor);

[0049] Figure 4 It is a comparison chart of the spectrum of measurement results from the traditional system, the optimized system, and the actual vibration signal;

[0050] Figure 5 This is a graph showing the signal-to-noise ratio improvement under different amplitude ratio conditions provided in the embodiments of the present invention;

[0051] Figure 6 The embodiment of the present invention provides a graph showing the relationship between the percentage reduction of the mean square error under different amplitude ratio conditions. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0053] Embodiments of the present invention provide a method for eliminating the self-vibration noise of a laser Doppler vibrometer, such as... Figure 1 As shown, the method includes the following steps:

[0054] S1. Measure the vibration signal of the object under test and the vibration signal of the instrument itself. The instrument refers to a laser Doppler vibration meter.

[0055] The measurement of the vibration signal of the object under test and the vibration signal of the instrument itself includes:

[0056] A reflector and a beam splitter are installed inside the laser Doppler vibrometer. The emitted laser light is split into two optical paths after passing through the beam splitter. One optical path is focused on the surface of the object being measured to measure the vibration signal of the object. The other optical path is focused on the outer shell of the laser Doppler vibrometer. The reflector sends the laser light reflected from the outer shell through the beam splitter into the receiver to measure the vibration signal of the instrument itself.

[0057] S2. Calculate the vibration velocity of the object under test containing noise based on the vibration signal of the object under test.

[0058] Specifically, the calculation of the vibration velocity of the measured object containing noise includes:

[0059] The frequency f of the light reflected by the noisy object under test r The calculation formula is:

[0060]

[0061] Among them, f r λ0 is the frequency of the light reflected by the noisy object, f0 is the wavelength, v is the frequency of the incident light, and v is the vibration velocity of the noisy object.

[0062] Frequency shift f of reflected light from a noisy object D The calculation formula is:

[0063]

[0064] Among them, f D The frequency shift of the light reflected from the noisy object being tested;

[0065] The formula for calculating the vibration velocity v of the noisy object being measured is:

[0066]

[0067] S3. Calculate the instrument's own vibration velocity based on its own vibration signal.

[0068] Specifically, the vibration velocity of the computing instrument itself includes:

[0069] The frequency f of the reflected light from the instrument r ’ The calculation formula is:

[0070]

[0071] Among them, f r ’ v is the frequency of the reflected light from the instrument. d The vibration velocity of the instrument;

[0072] The frequency shift f of the reflected light from the instrument D ’ The calculation formula is:

[0073]

[0074] Among them, f D ’ This refers to the frequency shift of the reflected light from the instrument.

[0075] The vibration velocity v of the instrument itself d The calculation formula is:

[0076]

[0077] S4. Calculate the noise-reduced vibration velocity of the object under test based on the vibration velocity of the object containing noise and the vibration velocity of the instrument itself.

[0078] Specifically, the calculation of the vibration velocity of the measured object after noise reduction includes:

[0079] The noise-reduced vibration velocity v of the measured object t The calculation formula is:

[0080]

[0081] Where v is the vibration velocity of the measured object containing noise, v d v is the vibration velocity of the instrument. t The vibration velocity of the object being measured after noise reduction.

[0082] The self-noise reduction of the laser Doppler vibration meter can be achieved by following the steps above.

[0083] The effectiveness and practicality of the method of the present invention will be illustrated below with reference to more specific embodiments.

[0084] The laser Doppler vibrometer used in this embodiment employs a He-Ne laser beam with a wavelength of 632.8 nm and a high-frequency bandwidth of up to 20 MHz. The laser Doppler vibrometer and the target are positioned on the same horizontal plane, with the measuring laser perpendicularly directed towards the target surface. A vibration pickup is mounted on top of the target to obtain the actual vibration signal of the target block. The experimental model is as follows: Figure 2 As shown in the figure, the laser Doppler vibrometer and the target under test are on the same horizontal plane. The internal structure of the laser Doppler vibrometer is shown in the figure. A reflector is installed inside the outer shell of the laser Doppler vibrometer. The reflector sends the laser light reflected from the instrument shell through a beam splitter to the receiver. The receiver processes the light to obtain the instrument's own vibration signal. To further verify the universality of the improved system (or optimized system) under different vibration conditions, four sets of vibration data (labeled a, b, c, d) were randomly selected as examples for experimental analysis. The sampling frequency was 1000 Hz and the sampling period was 1 second.

[0085] Figure 3 This is a time-domain comparison graph of measurement results from the traditional system, measurement results from the optimized system, and actual vibration signals (collected by the vibration sensor). Figure 3 (a) is a time-domain comparison diagram of the measurement results of the traditional system and the actual vibration signal. Figure 3 Figure (b) shows a time-domain comparison between the measurement results of the optimized system of the present invention and the actual vibration signal.

[0086] It can be seen that there is a significant difference between the signal measured by the traditional measurement system and the actual signal measured by the seismic pickup, indicating that the instrument's natural vibration has a significant impact on the signal during measurement. The figure also reflects the comparison between the measurement results of the optimized system and the actual signal. The measurement results of the improved system are highly consistent with the actual signal, and the signal optimization effect is very obvious.

[0087] The time-domain signals of a selected set of data are processed using a Fast Fourier Transform (FFT). The spectra of the traditional system measurement results, the optimized system measurement results, and the actual vibration signal are compared as follows: Figure 4 As shown. Figure 4 (a) shows a comparison of the spectrum of the measurement results from the traditional system and the actual vibration signal. Figure 4 (b) is a comparison of the spectrum of the optimized system measurement results and the actual vibration signal.

[0088] Due to interference from the instrument's own vibration, the frequency peaks of the measurement results from the traditional system differ significantly from the actual signal, exhibiting marked frequency peak shifts and amplitude differences in both the 50-100Hz and 450-500Hz frequency ranges. Comparison shows that the improved system effectively eliminates the frequency peaks caused by the instrument's own vibration in the traditional measurement system and corrects for frequency peak shifts and amplitude differences caused by instrument interference.

[0089] To further highlight the effectiveness of the system improvement and optimization, the mean square error (RMSE) of the measurement results from the traditional system and the actual vibration signal of the block, the mean square error (RMSE) of the measurement results from the improved system and the actual vibration signal of the object, and the signal-to-noise ratio (SNR) of the measurement results from the improved system and the traditional system were calculated to describe the signal optimization effect. The SNR is the ratio of effective signal to noise in the system; a higher SNR indicates that the noise mixed into the signal is relatively smaller. The calculation results are shown in Table 1. According to the data in the table, the average RMSE of the measurement results from the traditional measurement system is [value missing], while the average RMSE of the measurement results from the improved system is 0.08%, a reduction of 1.06% compared to the average error of the traditional measurement system (1.14%). The accuracy of the signal is significantly improved after the measurement system is improved. The signal-to-noise ratio (SNR) calculation results show that the SNR of the traditional vibration measurement system is relatively low, averaging around 4.2 dB, and the effective signal ratio is low. After the system is improved, the SNR of the effective signal is increased by an average of 22.72 dB, and the effective signal ratio is significantly increased. This indicates that the method proposed in this invention can effectively reduce the interference of instrument self-vibration.

[0090] Table 1. Calculation results of mean square error and signal-to-noise ratio

[0091]

[0092] By comparing the changes in signal-to-noise ratio (SNR) data, it was found that the greater the degree of interference in the traditional system's measurement results, the greater the increase in the SNR of the signal after system improvement, indicating a more significant effect on eliminating self-oscillation interference. For example, the traditional measurement SNRs for working conditions a and c were relatively high. Compared to working conditions b and d, the effective SNRs of groups a and c increased by 22.47 dB and 20.53 dB, respectively. In contrast, the effective SNRs of groups b and c, which had relatively lower SNRs, increased by 24.18 dB and 23.85 dB, respectively, higher than groups a and c. This indicates that signals with high original SNRs actually show a lower increase in the effective SNR after system improvement, and vice versa.

[0093] If the amplitude ratio of traditional measurement results and the natural vibration signal is used to represent the degree of interference with the signal, the larger the amplitude ratio, the greater the interference from instrument vibration. Figure 5 As can be seen, with the increase of instrument vibration interference, the improvement in the effective signal-to-noise ratio obtained by this technique increases significantly; through Figure 6 It can be seen that the percentage reduction in the mean square error of the signal after the system improvement shows the same trend as the improvement in the signal-to-noise ratio. The larger the amplitude ratio, the greater the reduction in the mean square error relative to the original error. This indicates that even under conditions of significant self-vibration interference, the improved system can still effectively reduce instrument vibration interference and ensure the measurement accuracy of the target object.

[0094] It is worth noting that excessive natural vibration intensity of the instrument can lead to over-correction in the proposed algorithm. When the natural vibration intensity is too high, even exceeding the target vibration intensity, the corrected data may overwrite the original actual vibration. Therefore, there are certain threshold limitations for the amplitude ratio increase and the root mean square error reduction percentage. Calculations show that the signal-to-noise ratio increase stops at around 24.5 dB, and the root mean square error reduction percentage plateaus at around 93.5%. It is foreseeable that when the natural vibration intensity of the instrument continues to increase and the amplitude ratio (natural vibration signal / original signal) exceeds 0.95, the correction effect of this method will no longer improve further, and over-correction may even occur.

[0095] This invention adds a reflector and a beam splitter to a laser Doppler vibration meter to measure and correct the instrument's own vibration, effectively eliminating measurement errors caused by the instrument's own vibration and providing technical support for obtaining higher-precision remote sensing vibration monitoring data in the field.

[0096] Accordingly, embodiments of the present invention also provide a self-vibration noise cancellation device for a laser Doppler vibration meter, the device comprising:

[0097] The measurement module is used to measure the vibration signal of the object under test and the vibration signal of the instrument itself, wherein the instrument refers to a laser Doppler vibration meter;

[0098] The first calculation module is used to calculate the vibration velocity of the object under test, including the vibration signal.

[0099] The second calculation module is used to calculate the instrument's own vibration velocity based on the instrument's own vibration signal.

[0100] The third calculation module is used to calculate the denoised vibration velocity of the test object based on the vibration velocity of the noisy test object and the vibration velocity of the instrument itself.

[0101] The apparatus of this embodiment can be used to perform Figure 1 The technical solutions of the method embodiments shown are similar in principle and in effect, and will not be described again here.

[0102] Embodiments of the present invention also provide an electronic device, which may vary considerably due to different configurations or performance. It may include one or more central processing units (CPUs) and one or more memories, wherein the memory stores at least one instruction, which is loaded and executed by the processor to implement the steps of the above-described method for eliminating the self-vibration noise of the laser Doppler vibrometer.

[0103] In an exemplary embodiment, a computer-readable storage medium is also provided, such as a memory including instructions that can be executed by a processor in a terminal to complete the self-vibration noise cancellation method of the laser Doppler vibrometer described above. For example, the computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0104] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

[0105] The use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0106] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0107] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for eliminating the self-vibration noise of a laser Doppler vibration meter, characterized in that, Includes the following steps: The instrument measures the vibration signal of the object under test and the vibration signal of the instrument itself; the instrument refers to a laser Doppler vibration meter. The measurement includes the vibration signal of the object being measured and the vibration signal of the instrument itself, including: A reflector and a beam splitter are installed inside the laser Doppler vibrometer. The emitted laser light is split into two optical paths after passing through the beam splitter. One optical path is focused on the surface of the object being measured to measure the vibration signal of the object. The other optical path is focused on the outer shell of the laser Doppler vibrometer. The reflector sends the laser light reflected from the outer shell through the beam splitter into the receiver to measure the vibration signal of the instrument itself. Calculate the vibration velocity of the object containing noise based on the vibration signal of the object being measured. Calculate the instrument's own vibration velocity based on its own vibration signal; The noise-reduced vibration velocity of the test object is calculated based on the vibration velocity of the noisy object and the vibration velocity of the instrument itself. The noise-reduced vibration velocity of the measured object v t The calculation formula is: （7） in, v The vibration velocity of the measured object, including the noise. v d The vibration velocity of the instrument. v t The vibration velocity of the measured object after noise reduction; λ 0 represents the wavelength. f 0 represents the incident light frequency. f D The frequency shift of the light reflected from the noisy object under test is calculated. f D ’ This refers to the frequency shift of the reflected light from the instrument.

2. The method for eliminating the natural noise of a laser Doppler vibrometer according to claim 1, characterized in that, The calculation of the vibration velocity of the measured object containing noise includes: Frequency of light reflected from the noisy object f r The calculation formula is: （1） in, f r The frequency of the light reflected from the noisy object being measured. v The vibration velocity of the measured object containing noise; Frequency shift of reflected light from the noisy test object f D The calculation formula is: （2） The vibration velocity of the object under test containing noise v The calculation formula is: （3）。 3. The method for eliminating the natural noise of a laser Doppler vibration meter according to claim 1, characterized in that, The vibration velocity of the computing instrument itself includes: The frequency of the reflected light of the instrument f r ’ The calculation formula is: （4） in, f r ’ The frequency of the reflected light from the instrument. v d The vibration velocity of the instrument; Frequency shift of reflected light from the instrument f D ’ The calculation formula is: （5） The vibration velocity of the instrument itself v d The calculation formula is: （6）。 4. A self-vibration noise cancellation device for a laser Doppler vibration meter, used to implement the method according to any one of claims 1-3, characterized in that, The device includes: The measurement module is used to measure the vibration signal of the object under test and the vibration signal of the instrument itself, wherein the instrument refers to a laser Doppler vibration meter; The first calculation module is used to calculate the vibration velocity of the object under test, including the vibration signal. The second calculation module is used to calculate the instrument's own vibration velocity based on the instrument's own vibration signal. The third calculation module is used to calculate the denoised vibration velocity of the test object based on the vibration velocity of the noisy test object and the vibration velocity of the instrument itself.

5. An electronic device, characterized in that, The electronic device includes a processor and a memory, the memory storing at least one instruction, which is loaded and executed by the processor to implement the self-vibration noise elimination method of the laser Doppler vibrometer as described in any one of claims 1-3.

6. A computer-readable storage medium, characterized in that, The storage medium stores at least one instruction, which is loaded and executed by a processor to implement the self-vibration noise elimination method of the laser Doppler vibrometer as described in any one of claims 1-3.

Images