Mechanical vibration measuring device and method based on composite vibration sensing stripes

Abstract

The invention provides a mechanical vibration measurement device and method based on composite vibration sensing stripes, and relates to the technical field of mechanical vibration measurement. The vibration measuring device comprises a composite vibration sensing stripe target, a high-speed camera and a computer; the composite vibration sensing stripe target is attached to the mechanical structure to capture vibration change information of the mechanical structure; the camera is used for carrying out image acquisition on the composite vibration sensing stripe pattern attached to the target and sending the acquired image to the computer for analysis; and the computer performs post-processing on the vibration sensing stripe image to obtain vibration information such as frequency and amplitude of the mechanical structure. The method and the device have the advantages of wide detection visual field and high detection precision; the method is suitable for mechanical structure vibration measurement tasks in various environments, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of visual measurement of vibration, and particularly relates to a mechanical vibration measurement device and method based on composite vibration-sensing fringes. Background Art

[0002] In the existing mechanical system control environment, accurate measurement of mechanical vibration is very important for ensuring the stable operation and precise control of equipment. Traditional vibration measurement methods mainly rely on hardware devices such as sensors and encoders. Although they can provide a certain positioning accuracy, their equipment costs are relatively high, and their layout and maintenance are cumbersome under complex working conditions. On the other hand, vision-based vibration measurement methods have lower costs, but they require the construction of complex spatial associations between the mechanical structure and the camera, and are easily affected by factors such as light and noise in some application scenarios, and may have problems such as insufficient accuracy and poor real-time performance. Evaluating the vibration characteristics and control accuracy of mechanical structures under variable working conditions, as well as verifying their vibration positioning and response accuracy during actual operation, is an essential task.

[0003] Based on this, we propose a mechanical vibration measurement device and method based on composite vibration-sensing fringes. By arranging the designed composite vibration-sensing fringe targets at key parts of the measured mechanical structure and combining corresponding detection and decoding methods, multi-dimensional acquisition and rapid identification of vibration information such as amplitude and frequency are achieved. Summary of the Invention

[0004] The purpose of the present invention is to propose a mechanical vibration measurement device and method based on composite vibration-sensing fringes, and the measurement device has the characteristics of a wide detection range and high detection accuracy.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows: The present invention proposes a mechanical vibration measurement method based on composite vibration-sensing fringes, including the following steps: Step S1: Attach the composite vibration-sensing fringe pattern to the mechanical structure to be measured, and establish a three-dimensional coordinate at the center point of the composite vibration-sensing fringe pattern. Taking the camera optical axis perpendicular to the camera imaging plane as the Z axis, define the horizontal direction perpendicular to the imaging optical axis as the X-axis, and the vertical direction perpendicular to the imaging optical axis as the Y-axis for sensing the vibration signal of the mechanical structure; Place the high-speed camera in a stable area, and set the focal length and aperture size according to the sensor size and shooting distance so that the composite vibration-sensing fringe pattern is captured by the high-speed camera; Step S2: When the mechanical structure vibrates, the relative position of the composite vibration-sensing fringe pattern attached to the mechanical structure also changes accordingly; Acquire the vibration-sensing fringe image with multi-dimensional vibration signals through the high-speed camera. Step S3: Transmit the collected vibration-sensing fringe signals to a computer, which decodes the vibration-sensing fringe signals and extracts the multi-vibration information of the mechanical structure; specifically, it includes the following steps: Step S31: For each frame of vibration-sensing fringe image, calculate the Pearson correlation coefficient between the gray values of the calculation region and the reference region of the vibration-sensing fringe image in the X-axis and Y-axis directions respectively, and obtain the Pearson correlation coefficient curve; taking the initial frame as the reference frame, perform cross-correlation calculations on the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions at different vibration offset values respectively, obtain the vibration offset value indices corresponding to the maximum cross-correlation values of the reference frame and the vibration frame in the X-axis and Y-axis directions, and calculate the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration-sensing fringe images of the reference frame and the vibration frame according to the obtained vibration offset value indices; Step S32: For each frame of vibration-sensing fringe image, calculate the fringe frequency using the frequency correction method; and based on the mathematical model of frequency and object distance, calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of vibration-sensing fringe image; Step S33: According to the gray information of each frame of vibration-sensing fringe image, use the vibration-sensing fringe decoding strategy based on the Gabor filter to identify the in-plane rotation angle information of the mechanical structure; Step S34: Calculate the object distance based on the fringe frequencies of each row and each column that have been obtained and the mathematical model of frequency and object distance, and obtain the corrected object distance through data fitting; deduce the mathematical model between the composite vibration-sensing fringe pattern and the vibration of the mechanical structure, so as to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance.

[0006] Preferably, the composite vibration-sensing fringe pattern is based on sine fringes, and by modulating the sine fringe frequency and direction information, composite coding fringe patterns with the same frequency in different directions are formed, including an intermediate single sine fringe region and four surrounding oblique fringe regions; The intermediate single sine fringe region includes four square single sine fringe regions, the sides of the four single sine fringe regions are respectively connected to the sides of the middle square gray block and are in a cross shape with the gray block, and the fringe directions of the four single sine fringe regions are respectively parallel to the sides of the gray block; The four surrounding oblique fringe regions include four square oblique fringe regions located in the blank areas around the intermediate single sine fringe region, the fringe directions of the four square oblique fringe regions are the same, and are connected to the fringes of the single sine fringe region.

[0007] Preferably, the specific method for calculating the Pearson correlation coefficient between the gray values of the calculation region and the reference region of the vibration-sensing fringe image in the X-axis and Y-axis directions is as follows: When calculating the Pearson correlation coefficient between the gray value of the calculation region and the gray value of the reference region of the vibration sensation fringe image in the X-axis direction, two single sine fringe regions perpendicular to the X-axis direction of the fringe and the middle square gray block are used as the reference region, and other regions except the reference region are used as the calculation region; Take the gray value of any row in the reference region as the reference row gray value, and calculate the Pearson correlation coefficient: where is the reference row r gray value and the PCC correlation coefficient of the gray value of the i th row in the calculation region; I r is the gray value of the reference row, I i is the gray value of the i th row in the calculation region; is I r and I i covariance; is I r standard deviation, is I i standard deviation; is the gray value of the r th j column in the reference row, the gray value of the i th row and the j th column in the calculation region, n is the number of columns; and are respectively I r and I i mean; When calculating the Pearson correlation coefficient between the gray value of the calculation region and the gray value of the reference region of the vibration sensation fringe image in the Y-axis direction, two single sine fringe regions perpendicular to the Y-axis direction of the fringe and the middle square gray block are used as the reference region, and other regions except the reference region are used as the calculation region; Take the gray value of any column in the reference region as the reference column gray value, and calculate the Pearson correlation coefficient: where is the PCC correlation coefficient between the gray value of the reference column c and the gray value of the j th column in the calculation region; I cis the grayscale value of the reference column, I j is the grayscale value of the j th column in the calculation region; is I c and I j 's covariance; is I c 's standard deviation, is I j 's standard deviation; is the grayscale value of the c th i row of the reference column, the grayscale value of the j th i row of the m th column in the calculation region, and are respectively I c and I j 's mean values.

[0008] Preferably, the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions are respectively subjected to cross-correlation calculation at different vibration offset values to obtain the vibration offset value indexes corresponding to the maximum cross-correlation values of the reference frame and the vibration frame in the X-axis and Y-axis directions, and the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration sense stripe images of the reference frame and the vibration frame is calculated according to the obtained vibration offset value indexes; specifically as follows: After respectively performing Fourier transforms on the obtained Pearson correlation coefficient curves in the X-axis and Y-axis directions, zero-padding in the frequency domain is used to upsample the Fourier-transformed correlation coefficient curves, and then the time-domain information is returned through inverse Fourier transform to increase the pixel resolution of vibration measurement; cross-correlation calculations are respectively performed using the processed Pearson correlation coefficient curves in the X-axis and Y-axis directions of the reference frame and the vibration frame: where h 1 s is the Pearson correlation coefficient value of the reference frame signal h 1 at the data point s , h 2 s + k is the Pearson correlation coefficient value of the corresponding vibration frame signal h 2 at the data point s + k , Sis the signal length; k is the vibration offset value, which can be positive, negative or zero; R 12 k is the cross-correlation value of the reference frame and the vibration frame signals in the X-axis or Y-axis direction h 1 and h 2 under the vibration offset value k ; After obtaining the vibration offset value index k corresponding to the maximum cross-correlation value of the reference frame and the vibration frame in the X-axis and Y-axis directions respectively, correct it through the peak correction method k , and multiply the corrected offset in the corresponding direction by the scale factor to obtain the vibration magnitudes in the X-axis and Y-axis directions; The calculation formula of the scale factor in the X-axis or Y-axis direction is as follows: where M is the scale factor, L is the actual length of the composite vibration sensing fringe pattern in the X-axis or Y-axis direction, a is the size of a single pixel of the imaging camera, r' is the number of pixels of the side length of the vibration sensing fringe image in the X-axis or Y-axis direction occupied by the camera sensor.

[0009] Preferably, for each frame of the vibration sensing fringe image, the fringe frequency is calculated by the frequency correction method; specifically: Perform Fourier transform on the gray values of the vibration sensing fringe image row by row and column by column to obtain the fringe frequencies of each row and each column in the vibration sensing fringe image, and use the peak correction method to correct the fringe frequencies of each row and each column obtained, and obtain multiple groups of fringe frequencies of the corrected vibration sensing fringe image in the X-axis and Y-axis directions.

[0010] Preferably, based on the mathematical model of frequency and object distance, calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of the vibration sensing fringe image; specifically: Construct a mathematical model of the fringe frequency and the distance between the target along the Z-axis of the camera optical axis: where f I is the fringe frequency of the vibration sensing fringe image on the sensor, D is the distance between the imaging camera and the composite vibration sensing fringe pattern along the Z-axis of the camera optical axis, F is the focal length of the imaging lens, a is the size of a single pixel of the imaging camera, p is the fringe period of the composite vibration sensing fringe pattern; ​For multiple groups of fringe frequencies of the corrected vibration-induced fringe image in the X-axis and Y-axis directions, take the median of the fringe frequencies of each column in the X-axis direction and the median of the fringe frequencies of each row in the Y-axis direction, and calculate their average as the frequency of the vibration-induced fringe image on the sensor. f I , substitute it into the mathematical model to calculate the object distance. D , and obtain the position information of the mechanical structure in the Z-axis direction.

[0011] Preferably, the step S33 is specifically: Perform convolution on the vibration-induced fringe image: where R ( x , y ) is the output response of the Gabor filter at the pixel position ( x , y ); I ( u , v ) is the gray value of the vibration-induced fringe image at the position ( u , v ), is the Gabor filter kernel with a spatial frequency of f and a direction of θ ; The two-dimensional calculation formula of the Gabor filter is as follows:

[0012] where is the two-dimensional Gabor function, represents the coordinates after rotation transformation:

[0013] where, represents the Gabor filter wavelength, and ; represents the Gaussian standard deviation; represents the spatial aspect ratio; represents the phase shift; represents the imaginary unit; Set the Gabor filter wavelength to the reciprocal of the fringe frequency f I in the vibration-induced fringe image; set the value range of the Gabor filter direction θ to 0 - 360°, and set the step size to be between 0.01° and 1°. Traverse all directions of the Gabor filter according to the preset step size and calculate the filtering output response for each direction. The Gabor filter angle corresponding to the maximum output responseθ , as the in-plane rotation angle of the mechanical structure in the Z-axis direction.

[0014] Preferably, the object distance is calculated based on the obtained stripe frequencies of each row and each column and the mathematical model of frequency and object distance, and the corrected object distance is obtained through data fitting; specifically: In the X-axis direction, based on the obtained stripe frequencies of each column, the corresponding object distances are calculated respectively according to the mathematical model of frequency and object distance D x1 , D x2 ,… D xc , and the corrected object distance is obtained through least squares fitting D' x1 , D' x2 ,… D' xc ; In the Y-axis direction, based on the obtained stripe frequencies of each row, the corresponding object distances are calculated respectively according to the mathematical model of frequency and object distance D y1 , D y2 ,… D yr , and the corrected object distance is obtained through least squares fitting D' y1 , D' y2 ,… D' yr .

[0015] Preferably, the mathematical model between the composite vibration sensing stripe pattern and the mechanical structure vibration is deduced to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance; specifically: The out-of-plane rotation angle in the X-axis direction α is expressed as: where D' x1 is the distance between the first column of stripes in the corrected composite vibration sensing stripe pattern and the imaging camera in the Z-axis direction, D' xc is the distance between the last column of stripes in the corrected composite vibration sensing stripe pattern and the imaging camera in the Z-axis direction; D is the distance between the imaging camera and the composite vibration sensing stripe pattern along the camera optical axis Z-axis obtained in step S32; r x is the number of camera sensor pixels occupied by the composite vibration sensing stripe pattern in the X-axis direction; Out-of-plane rotation angle in the Y-axis direction β It is expressed as: Wherein, D' y1 is the distance between the first row of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction, D' yr is the distance between the last row of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction; r y is the number of camera sensor pixels occupied by the composite vibration-sensing fringe pattern in the Y-axis direction.

[0016] The present invention also provides a mechanical vibration measurement device based on composite vibration-sensing fringes. The device is implemented by using any one of the above-mentioned mechanical vibration measurement methods based on composite vibration-sensing fringes, and includes a composite vibration-sensing fringe target, a high-speed camera, and a computer; The composite vibration-sensing fringe target is provided with a composite vibration-sensing fringe pattern, and the composite vibration-sensing fringe target is attached to the mechanical structure to be measured for obtaining vibration perception information; The high-speed camera is responsible for collecting images of the composite vibration-sensing fringe pattern and transmitting the images to the computer; The computer extracts the vibration perception information of the target image and performs analysis and processing to obtain the multi-dimensional vibration information of the mechanical structure.

[0017] Compared with the prior art, the present invention has the following beneficial effects: A mechanical vibration measurement device and method based on composite vibration-sensing fringes. By attaching the composite vibration-sensing fringe pattern to the mechanical structure, collecting the motion images of the object to be measured through a high-speed camera, and finally analyzing and processing the vibration-sensing fringe images through a computer to obtain the multi-dimensional vibration information of the mechanical structure. Compared with the existing algorithms, this calculation method has the advantages of a wide detection range and high measurement accuracy, and has extremely high practical value and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of the mechanical vibration measurement device based on composite vibration-sensing fringes of the present invention.

[0019] In the figure: 1 - high-speed camera; 2 - computer; 3 - composite vibration-sensing fringe target; 4 - mechanical structure to be measured. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following combines the attached Figure 1 , and specifically describes the technical solutions of the present invention.

[0021] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] The present invention proposes a mechanical vibration measurement method based on composite vibration-sensing fringes, referring to Figure 1 , and includes the following steps: Step S1: Attach the composite vibration-sensing fringe pattern to the mechanical structure 4 to be measured, and establish a three-dimensional coordinate at the center point of the composite vibration-sensing fringe pattern. Taking the camera optical axis perpendicular to the camera imaging plane as the Z axis, define the horizontal direction perpendicular to the imaging optical axis as the X-axis, and the vertical direction perpendicular to the imaging optical axis as the Y-axis, for sensing the vibration signal of the mechanical structure; Place the high-speed camera 1 in a stable area, and set the focal length and aperture size according to the sensor size and shooting distance, so that the composite vibration-sensing fringe pattern is captured by the high-speed camera 1; Step S2: When the mechanical structure vibrates, the relative position of the composite vibration-sensing fringe pattern attached to the mechanical structure also changes accordingly; Collect the vibration-sensing fringe image with multi-dimensional vibration signals through the high-speed camera 1; Step S3: Transmit the collected vibration-sensing fringe signal to the computer 2, and the computer 2 decodes the vibration-sensing fringe signal and extracts the multi-dimensional vibration information of the mechanical structure; Specifically, it includes the following steps: Step S31: For each frame of the vibration-sensing fringe image, calculate the Pearson correlation coefficient between the gray value of the calculation area and the gray value of the reference area of the vibration-sensing fringe image in the X-axis and Y-axis directions respectively, and obtain the Pearson correlation coefficient curve; Taking the initial frame as the reference frame, perform cross-correlation calculations on the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions at different vibration offset values respectively, obtain the vibration offset value index corresponding to the maximum cross-correlation value of the reference frame and the vibration frame in the X-axis and Y-axis directions, and calculate the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration-sensing fringe images of the reference frame and the vibration frame according to the obtained vibration offset value index; Step S32: For each frame of vibration-sensing fringe image, calculate the fringe frequency using the frequency correction method; and calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of vibration-sensing fringe image based on the mathematical model of frequency and object distance. Step S33: According to the gray-scale information of each frame of vibration-sensing fringe image, use the vibration-sensing fringe decoding strategy based on the Gabor filter to identify the in-plane rotation angle information of the mechanical structure. Step S34: Calculate the object distance based on the obtained fringe frequencies of each row and each column and the mathematical model of frequency and object distance, and obtain the corrected object distance through data fitting; deduce the mathematical model between the composite vibration-sensing fringe pattern and the vibration of the mechanical structure to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance.

[0024] In this embodiment, the composite vibration-sensing fringe pattern is based on sine fringes. By modulating the frequency and direction information of the sine fringes, composite coding fringe patterns with the same frequency in different directions are formed, including an intermediate single-sine fringe area and a peripheral oblique fringe area. The intermediate single-sine fringe area includes four square single-sine fringe areas. The sides of the four single-sine fringe areas are respectively connected to the sides of the central square gray block and form a cross with the gray block. The fringe directions of the four single-sine fringe areas are respectively parallel to the sides of the gray block. The peripheral oblique fringe area includes four square oblique fringe areas located in the blank areas around the intermediate single-sine fringe area. The fringe directions of the four square oblique fringe areas are the same and are connected to the fringes of the single-sine fringe area.

[0025] In this embodiment, the Pearson correlation coefficients between the gray-scale values of the calculation area and the reference area of the vibration-sensing fringe image in the X-axis and Y-axis directions are calculated as follows: When calculating the Pearson correlation coefficient between the gray-scale values of the calculation area and the reference area of the vibration-sensing fringe image in the X-axis direction, two single-sine fringe areas with fringes perpendicular to the X-axis direction and the central square gray block are used as the reference area, and other areas except the reference area are used as the calculation area. Take the gray-scale value of any row in the reference area as the reference row gray-scale value and calculate the Pearson correlation coefficient: where is the PCC correlation coefficient between the reference row r gray-scale value and the gray-scale value of the i th row in the calculation area; I r is the gray-scale value of the reference row, I i is the gray-scale value of the i th row in the calculation area; is I r and I i 's covariance; is I r 's standard deviation, is I i 's standard deviation; is the reference row r the j column gray value, the calculation area's i row j column gray value, n is the number of columns; and are respectively I r and I i 's mean value; When calculating the Pearson correlation coefficient between the gray values of the calculation area and the reference area of the vibration sensation stripe image in the Y-axis direction, two single sine stripe areas perpendicular to the Y-axis direction of the stripe and the middle square gray block are used as the reference area, and the other areas except the reference area are used as the calculation area; Take any column gray value of the reference area as the reference column gray value and calculate the Pearson correlation coefficient: where is the reference column c gray value and the PCC correlation coefficient of the gray value of the j column in the calculation area; I c is the gray value of the reference column, I j is the gray value of the j column in the calculation area; is I c and I j 's covariance; is I c 's standard deviation, is I j 's standard deviation; is the reference column c the i row gray value, the calculation area's j column i row gray value, m is the number of rows; and are respectively I c and I j mean values.

[0026] In this embodiment, the cross-correlation calculation is respectively performed on the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions at different vibration offset values, and the vibration offset value index corresponding to the maximum cross-correlation value of the reference frame and the vibration frame in the X-axis and Y-axis directions is obtained, and the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration sense stripe images of the reference frame and the vibration frame is calculated according to the obtained vibration offset value index; specifically as follows: After respectively performing Fourier transforms on the obtained Pearson correlation coefficient curves in the X-axis and Y-axis directions, zero-padding in the frequency domain is used to upsample the Fourier-transformed correlation coefficient curves, and then the time-domain information is returned through inverse Fourier transform to increase the pixel resolution of vibration measurement; the cross-correlation calculation is respectively performed using the Pearson correlation coefficient curves in the X-axis and Y-axis directions of the processed reference frame and vibration frame: where h 1 s is the Pearson correlation coefficient value of the reference frame signal h 1 at the data point s h 2 s + k is the Pearson correlation coefficient value of the corresponding vibration frame signal h 2 at the data point s + k S is the signal length; k is the vibration offset value, taking positive, negative or zero; R 12 k is the cross-correlation value of the reference frame and vibration frame signals h 1 and h 2 at the vibration offset value k ; After respectively obtaining the vibration offset value index k corresponding to the maximum cross-correlation value of the reference frame and the vibration frame in the X-axis and Y-axis directions, k is corrected by the peak correction method, and the corrected offset in the corresponding direction is multiplied by the scale factor to obtain the vibration magnitudes in the X-axis and Y-axis directions; The calculation formula of the scale factor in the X-axis or Y-axis direction is as follows: where,​​​M is the scale factor, L is the actual length of the composite vibration sensing fringe pattern in the X-axis or Y-axis direction, a is the size of a single pixel of the imaging camera, r' is the number of pixels of the camera sensor occupied by the side length of the vibration sensing fringe image in the X-axis or Y-axis direction.

[0027] In this embodiment, for each frame of the vibration sensing fringe image, the fringe frequency is calculated by using the frequency correction method; specifically: Perform Fourier transform on the gray values of the vibration sensing fringe image row by row and column by column to obtain the fringe frequencies of each row and each column in the vibration sensing fringe image, and use the peak correction method to correct the fringe frequencies of each row and each column obtained, so as to obtain multiple groups of fringe frequencies in the X-axis and Y-axis directions of the corrected vibration sensing fringe image.

[0028] In this embodiment, based on the mathematical model of frequency and object distance, calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of the vibration sensing fringe image; specifically: Construct a mathematical model of the fringe frequency and the distance between the target along the Z-axis of the camera optical axis: where, f I is the fringe frequency of the vibration sensing fringe image on the sensor, D is the distance between the imaging camera and the composite vibration sensing fringe pattern along the Z-axis of the camera optical axis, F is the focal length of the imaging lens, a is the size of a single pixel of the imaging camera, p is the fringe period of the composite vibration sensing fringe pattern; For the multiple groups of fringe frequencies in the X-axis and Y-axis directions of the corrected vibration sensing fringe image, take the median of the fringe frequencies of each column in the X-axis direction and the median of the fringe frequencies of each row in the Y-axis direction and average them as the frequency of the vibration sensing fringe image on the sensor f I , substitute it into the mathematical model to calculate the object distance D , and obtain the position information of the mechanical structure in the Z-axis direction.

[0029] In this embodiment, step S33 is specifically: Perform convolution on the vibration sensing fringe image: where R ( x , y ) is the output response of the Gabor filter at the pixel position ( x , y ) I (u , v ) is the gray value of the vibration-induced fringe image at the position ([ u , v ), is the Gabor filter kernel with a spatial frequency of f and a direction of θ ; The two-dimensional calculation formula of the Gabor filter is as follows:

[0030] where is the two-dimensional Gabor function, represents the coordinates after rotation transformation:

[0031] where, represents the Gabor filter wavelength, and ; represents the Gaussian standard deviation; represents the spatial aspect ratio; represents the phase shift; represents the imaginary unit; Set the Gabor filter wavelength to the reciprocal of the fringe frequency in the vibration-induced fringe image f I ; Set the value range of the Gabor filter direction θ to 0 - 360°, and set the step size to be between 0.01° and 1°. Traverse all directions of the Gabor filter according to the preset step size and calculate the filtered output response for each direction. The Gabor filter angle θ corresponding to the maximum output response is used as the in-plane rotation angle of the mechanical structure in the Z-axis direction.

[0032] In this embodiment, the object distance is calculated based on the obtained fringe frequencies of each row and each column and the mathematical model of the frequency and the object distance, and the corrected object distance is obtained through data fitting; specifically: For the X-axis direction, based on the obtained fringe frequencies of each column, calculate the corresponding object distances D x1 , D x2 ,… D xc according to the mathematical model of the frequency and the object distance, and obtain the corrected object distance D' x1 , D' x2 ,… D' xc through least squares fitting; In the Y-axis direction, based on the stripe frequencies of each row that have been obtained, the corresponding object distances are calculated respectively according to the mathematical model of frequency and object distance D y1 , D y2 ,… D yr , and the corrected object distance is obtained by least squares fitting D' y1 , D' y2 ,… D' yr 。

[0033] In this embodiment, the mathematical model between the derived composite vibration-sensing fringe pattern and the mechanical structure vibration is used to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance; specifically: The out-of-plane rotation angle in the X-axis direction α is expressed as: where, D' x1 is the distance between the first column of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction, D' xc is the distance between the last column of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction; D is the distance between the imaging camera and the composite vibration-sensing fringe pattern along the Z-axis of the camera optical axis obtained in step S32; r x is the number of camera sensor pixels occupied by the composite vibration-sensing fringe pattern in the X-axis direction; The out-of-plane rotation angle in the Y-axis direction β is expressed as: where, D' y1 is the distance between the first row of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction, D' yr is the distance between the last row of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction; r y is the number of camera sensor pixels occupied by the composite vibration-sensing fringe pattern in the Y-axis direction.

[0034] The present invention also proposes a mechanical vibration measurement device based on composite vibration-sensing fringes. The device is implemented by using any of the above-mentioned mechanical vibration measurement methods based on composite vibration-sensing fringes, and includes a composite vibration-sensing fringe target 3, a high-speed camera 1, and a computer 2; The composite vibration-sensing stripe target is provided with a composite vibration-sensing stripe pattern, and the composite vibration-sensing stripe target is attached to the mechanical structure 4 to be measured for obtaining vibration perception information; The high-speed camera 1 is responsible for collecting images of the composite vibration-sensing stripe pattern and transmitting the images to the computer 2; The computer 2 extracts the vibration perception information of the target image and performs analysis and processing to obtain multi-dimensional vibration information of the mechanical structure.

[0035] The above are only the preferred embodiments of the present invention, and are not limitations to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A mechanical vibration measurement method based on composite vibration-sensing fringes, characterized in that, It includes the following steps: Step S1: Attach the composite vibration sensing fringe pattern to the mechanical structure to be measured, and establish a three-dimensional coordinate at the center point of the composite vibration sensing fringe pattern. Take the camera optical axis perpendicular to the camera imaging plane as Z the axis, define the horizontal direction perpendicular to the imaging optical axis as the X-axis, and the vertical direction perpendicular to the imaging optical axis as the Y-axis for sensing the vibration signal of the mechanical structure; Place the high-speed camera in a stable area, set the focal length and aperture size according to the sensor size and shooting distance, so that the composite vibration sensing fringe pattern is captured by the high-speed camera; Step S2: When the mechanical structure vibrates, the relative position of the composite vibration-sensing fringe pattern attached to the mechanical structure also changes accordingly on the imaging sensor of the high-speed camera; the vibration-sensing fringe image with multi-dimensional vibration signals is acquired through the high-speed camera; Step S3: Transmit the acquired vibration-sensing fringe signals to a computer, and the computer decodes the vibration-sensing fringe signals and extracts the multi-dimensional vibration information of the mechanical structure; specifically, it includes the following steps: Step S31: For each frame of the vibration-sensing fringe image, calculate the Pearson correlation coefficient between the gray value of the calculation area and the gray value of the reference area of the vibration-sensing fringe image in the X-axis and Y-axis directions respectively, and obtain the Pearson correlation coefficient curve; taking the initial frame as the reference frame, perform cross-correlation calculations on the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions at different vibration offset values respectively, obtain the vibration offset value indexes corresponding to the maximum cross-correlation values of the reference frame and the vibration frame in the X-axis and Y-axis directions, and calculate the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration-sensing fringe images of the reference frame and the vibration frame according to the obtained vibration offset value indexes; Step S32: For each frame of the vibration-sensing fringe image, calculate the fringe frequency using the frequency correction method; and calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of the vibration-sensing fringe image based on the mathematical model of frequency and object distance; Step S33: According to the gray information of each frame of the vibration-sensing fringe image, use the vibration-sensing fringe decoding strategy based on the Gabor filter to identify the in-plane rotation angle information of the mechanical structure; Step S34: Calculate the object distance based on the fringe frequencies of each row and each column that have been obtained and the mathematical model of frequency and object distance, and obtain the corrected object distance through data fitting; deduce the mathematical model between the composite vibration-sensing fringe pattern and the vibration of the mechanical structure, so as to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance.

2. The mechanical vibration measurement method based on composite vibration sensing fringes according to claim 1, characterized in that The composite vibration-sensing fringe pattern is based on sine fringes, and by modulating the sine fringe frequency and direction information, a composite coding fringe pattern with the same frequency in different directions is formed, including an intermediate single sine fringe area and a surrounding oblique fringe area; The intermediate single sine fringe area includes four square single sine fringe areas, the sides of the four single sine fringe areas are respectively connected to the sides of the middle square gray block and are in a cross shape with the gray block, and the fringe directions of the four single sine fringe areas are respectively parallel to the sides of the gray block; The surrounding oblique fringe area includes four square oblique fringe areas located in the blank areas around the intermediate single sine fringe area, the fringe directions of the four square oblique fringe areas are the same, and are connected to the fringes of the single sine fringe area.

3. The mechanical vibration measurement method based on composite vibration sensing fringes according to claim 2, wherein The specific method for calculating the Pearson correlation coefficient between the gray value of the calculation area and the gray value of the reference area of the vibration-sensing fringe image in the X-axis and Y-axis directions respectively is as follows: When calculating the Pearson correlation coefficient between the gray value of the calculation region and the gray value of the reference region of the vibration sense stripe image in the X-axis direction, two single sine stripe regions perpendicular to the X-axis direction of the stripe and the middle square gray block are used as the reference region, and other regions except the reference region are used as the calculation region; Take the gray value of any row of the reference region as the reference row gray value, and calculate the Pearson correlation coefficient: Among them is the reference line r The PCC correlation coefficient between the gray value and the gray value of the i th row in the calculation area; I r is the gray value of the reference line, I i is the gray value of the i th row in the calculation area; is I r and I i 's covariance; is I r 's standard deviation, is I i 's standard deviation; is the gray value of the r th j column of the reference line, the gray value of the i th j row and n th and are respectively I r and I i 's means; When calculating the Pearson correlation coefficient between the gray value of the calculation region and the gray value of the reference region of the vibration sense stripe image in the Y-axis direction, two single sine stripe regions perpendicular to the Y-axis direction of the stripe and the middle square gray block are used as the reference region, and other regions except the reference region are used as the calculation region; Take the gray value of any column of the reference region as the reference column gray value, and calculate the Pearson correlation coefficient: Among them is the reference column c The PCC correlation coefficient between the grayscale value and the grayscale value of the j th column in the calculation area; I c is the gray value of the reference column, I j is the gray value of the j th column in the calculation area; is I c and I j 's covariance; is I c 's standard deviation, is I j 's standard deviation; is the gray value of the reference column c the i th row, the gray value of the j th column and the i th row in the calculation area, m is the number of rows; and are respectively I c and I j 's means.

4. The mechanical vibration measurement method based on the composite vibration sensing stripes according to claim 2, characterized in that, The cross-correlation calculation is respectively performed on the Pearson correlation coefficient curves of the reference frame and the vibration frame in the X-axis and Y-axis directions under different vibration offset values, and the vibration offset value index corresponding to the maximum cross-correlation value of the reference frame and the vibration frame in the X-axis and Y-axis directions is obtained, and the two-dimensional vibration information of the mechanical structure in the X-axis and Y-axis directions in the vibration sense stripe images of the reference frame and the vibration frame is calculated according to the obtained vibration offset value index; specifically as follows: After respectively performing Fourier transforms on the obtained Pearson correlation coefficient curves in the X-axis and Y-axis directions, up-sample the Fourier-transformed correlation coefficient curves by zero-padding in the frequency domain, and then return the time-domain information through inverse Fourier transform to increase the pixel resolution of vibration measurement; perform cross-correlation calculations respectively using the processed Pearson correlation coefficient curves in the X-axis and Y-axis directions of the reference frame and the vibration frame: where h 1 s is the reference frame signal in the X-axis or Y-axis direction h 1 at the data point s is the Pearson correlation coefficient value at that point, h 2 s+ k is the vibration frame signal corresponding to the X-axis or Y-axis direction h 2 at the data point s + k is the Pearson correlation coefficient value at that point, S is the signal length; k is the vibration offset value, which can be positive, negative or zero; R 12 k is the cross-correlation value between the reference frame and the vibration frame signals in the X-axis or Y-axis direction h 1 and h 2 at the vibration offset value k ;​ Obtain the vibration offset value indexes corresponding to the maximum cross-correlation values between the reference frame and the vibration frame in the X-axis and Y-axis directions respectively k After that, correct it by the peak correction method k Multiply the corrected offset in the corresponding direction by the scale factor to obtain the vibration magnitudes in the X-axis and Y-axis directions; The calculation formula of the scale factor in the X-axis or Y-axis direction is as follows: Among them, M is the scale factor, L is the actual length of the composite vibration sensing fringe pattern in the X-axis or Y-axis direction, a is the size of a single pixel of the imaging camera, r' is the number of camera sensor pixels occupied by the side length of the vibration sensing fringe image in the X-axis or Y-axis direction.

5. The mechanical vibration measurement method based on composite vibration-sensing fringes according to claim 2, characterized in that, For each frame of vibration sense stripe image, the frequency correction method is used to calculate the stripe frequency; specifically: Perform Fourier transforms on the gray values of the vibration sense stripe image row by row and column by column to obtain the stripe frequencies of each row and each column in the vibration sense stripe image, and use the peak correction method to correct the stripe frequencies of each row and each column obtained, and obtain multiple groups of stripe frequencies in the X-axis and Y-axis directions of the corrected vibration sense stripe image.

6. The mechanical vibration measurement method based on the composite vibration sensing stripes according to claim 5, characterized in that Based on the mathematical model of frequency and object distance, calculate the one-dimensional vibration information of the mechanical structure in the Z-axis direction in the current frame of vibration sense stripe image; specifically: Construct a mathematical model of stripe frequency and the distance between the target along the camera optical axis Z-axis: Among them, f I is the fringe frequency of the vibration-induced fringe image on the sensor, D is the distance between the imaging camera and the composite vibration-induced fringe pattern along the Z-axis of the camera optical axis, F is the focal length of the imaging lens, a is the size of a single pixel of the imaging camera, p is the fringe period of the composite vibration-induced fringe pattern; For multiple groups of fringe frequencies of the corrected vibration-sensing fringe image in the X-axis and Y-axis directions, take the median of the fringe frequencies of each column in the X-axis direction and the median of the fringe frequencies of each row in the Y-axis direction, and calculate the average as the frequency of the vibration-sensing fringe image on the sensor. f I , substitute it into the mathematical model to calculate the object distance D , and obtain the position information of the mechanical structure in the Z-axis direction.

7. The mechanical vibration measurement method based on composite vibration sensing stripes according to claim 2, wherein The specific step S33 is: Perform convolution on the vibration sense stripe image: Among them R ( x , y ) is the output response of the Gabor filter at the pixel position ( x , y ); I ( u , v ) is the gray value of the vibration-induced fringe image at the position ( u , v ), is the Gabor filter kernel with a spatial frequency of f and a direction of θ ; The two-dimensional calculation formula of the Gabor filter is as follows: ； Among them is a two-dimensional Gabor function, represents the coordinates after rotation transformation: ； Among them, represents the wavelength of the Gabor filter, and ; represents the Gaussian standard deviation; represents the spatial aspect ratio; represents the phase shift; represents the imaginary unit; Set the Gabor filter wavelength to the reciprocal of the fringe frequency in the vibration-induced fringe image f I ; set the value range of the Gabor filter orientation θ to 0 - 360°, and set the step size to be between 0.01° and 1°. Traverse all orientations of the Gabor filter according to the preset step size and calculate the filtered output response for each orientation. The angle of the Gabor filter θ corresponding to the maximum output response is used as the in-plane rotation angle of the mechanical structure in the Z-axis direction.

8. The mechanical vibration measurement method based on composite vibration sensing fringes according to claim 6, wherein Based on the stripe frequencies of each row and each column already obtained and the mathematical model of frequency and object distance, calculate the object distance, and obtain the corrected object distance through data fitting; specifically: In the X-axis direction, based on the stripe frequencies of each column that have been obtained, calculate the corresponding object distances respectively according to the mathematical model of frequency and object distance D x1 , D x2 ,… D xc , and obtain the corrected object distance through least squares fitting D' x1 , D' x2 ,… D' xc ; In the Y-axis direction, based on the fringe frequencies of each row that have been obtained, calculate the corresponding object distances respectively according to the mathematical model of frequency and object distance D y1 , D y2 ,… D yr , and obtain the corrected object distance through least squares fitting D' y1 , D' y2 ,… D' yr 。 9. The mechanical vibration measurement method based on the composite vibration sensing stripes according to claim 8, wherein Derive the mathematical model between the composite vibration sense stripe pattern and the vibration of the mechanical structure to obtain the out-of-plane rotation angle information of the mechanical structure according to the corrected object distance; specifically: Out-of-plane rotation angle in the X-axis direction α Expressed as: Among them, D' x1 is the distance between the first column of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction, D' xc is the distance between the last column of fringes in the corrected composite vibration-sensing fringe pattern and the imaging camera in the Z-axis direction; D is the distance between the imaging camera and the composite vibration-sensing fringe pattern along the Z-axis of the camera optical axis obtained in step S32; r x is the number of camera sensor pixels occupied by the composite vibration-sensing fringe pattern in the X-axis direction; Out-of-plane rotation angle in the Y-axis direction β Expressed as: Among them, D' y1 is the distance between the first row of fringes in the corrected composite vibration-induced fringe pattern and the imaging camera in the Z-axis direction, D' yr is the distance between the last row of fringes in the corrected composite vibration-induced fringe pattern and the imaging camera in the Z-axis direction; r y is the number of camera sensor pixels occupied by the composite vibration-induced fringe pattern in the Y-axis direction.

10. A mechanical vibration measurement device based on composite vibration sensing fringes, characterized in that The device is implemented by using the mechanical vibration measurement method based on composite vibration sense stripes described in any one of claims 1-9, and includes a composite vibration sense stripe target, a high-speed camera, and a computer; The composite vibration-sensing fringe target is provided with a composite vibration-sensing fringe pattern, and the composite vibration-sensing fringe target is attached to the mechanical structure to be measured for obtaining vibration perception information; The high-speed camera is responsible for collecting images of the composite vibration-sensing fringe pattern and transmitting the images to the computer; The computer extracts the vibration perception information of the target image and performs analysis and processing to obtain the multi-dimensional vibration information of the mechanical structure.

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