Stay cable force identification method, device and equipment based on high-order vibration mode

Abstract

The invention discloses an inhaul cable force identification method, device and equipment based on a high-order vibration mode. The method comprises the following steps: acquiring a vibration video of a stay cable, amplifying the vibration video by using a phase-based motion amplification algorithm to obtain an amplified vibration video, acquiring vibration displacement of the stay cable in the amplified vibration video by using a center line detection algorithm, and acquiring a high-order vibration mode of the stay cable by using a preset subspace recognition method according to the vibration displacement. And calculating the middle half-wavelength of any two-order high-order vibration mode, and determining the cable force of the inhaul cable according to the middle half-wavelength. According to the scheme, when the cable force of the inhaul cable is calculated, the effective length of the inhaul cable is replaced with the middle half-wavelength of the high-order vibration mode, the influence of complex boundary conditions on calculation of the effective length of the inhaul cable can be eliminated, and therefore the recognition precision of the cable force of the bridge inhaul cable is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge health monitoring, and in particular to a cable force identification method, device and equipment based on high-order mode. BACKGROUND

[0002] Cables are the main load-bearing members of cable-supported bridges, and their stress state is an important indicator for evaluating the health status of bridges. Accurate measurement of cable force is crucial for ensuring the structural safety of bridges during the construction phase and operation period.

[0003] Currently, the commonly used cable force measurement methods in engineering include oil pressure gauge method, pressure sensor method, magnetic flux method and frequency method, etc. Although these methods have been applied in practical engineering, they each have certain limitations. The oil pressure gauge method and the pressure sensor method can provide relatively accurate cable force measurement, but their high cost and complex installation process make them mainly suitable for cable force measurement during the construction phase. The magnetic flux method estimates the cable force through the relationship between the cable force and the change in magnetic flux, and has high precision and stability, but its application is limited by factors such as complex calibration process and the need to customize electromagnetic sensors according to the cable diameter. The frequency method has been widely used in practical engineering due to its low cost and simple operation, but its precision is easily affected by factors such as boundary conditions, bending stiffness and effective length, thereby limiting its applicability in complex working conditions.

[0004] In recent years, non-contact cable force measurement methods have developed rapidly, such as microwave radar, laser Doppler vibrometer and computer vision-based measurement methods. Although microwave radar and laser Doppler vibrometer have high measurement accuracy, their high price and complex operation requirements limit their application in practical engineering. In contrast, computer vision-based cable force measurement methods have great potential for engineering application due to their non-contact, low cost and simple operation advantages. However, existing technologies use computer vision to obtain the modal frequency of the cable, and then use the frequency method to estimate the cable force, without effectively breaking through the inherent precision limitation.

[0005] Therefore, how to provide a solution to the above technical problems is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0006] To solve the above technical problems, the present application provides a cable force identification method, device, equipment and medium based on high-order mode, which can eliminate the influence of complex boundary conditions on the calculation of cable effective length, thereby improving the identification precision of bridge cable force.

[0007] In one aspect, the present application provides a cable force identification method based on high-order mode, comprising: acquiring a vibration video of the cable; amplifying the vibration video by using a phase-based motion magnification algorithm to obtain an amplified vibration video; obtaining a vibration displacement of the cable in the amplified vibration video by using a centerline detection algorithm; obtaining high-order modes of the cable by using a preset subspace identification method according to the vibration displacement; calculating a middle half-wavelength of any two high-order modes, and determining a cable force of the cable according to the middle half-wavelength.

[0008] Preferably, after the vibration video of the cable is acquired, the method further comprises: preprocessing the vibration video to eliminate noise information in the vibration video.

[0009] Preferably, the vibration video is amplified by using the phase-based motion magnification algorithm to obtain the amplified vibration video, comprising: performing 2D Fourier transform on the vibration video to obtain a frequency domain image sequence; decomposing the frequency domain image sequence by using a complex steerable pyramid to obtain an amplitude spectrum and a phase spectrum; performing noise reduction processing on the phase spectrum by using a 2D Gabor wavelet filter to obtain a noise-reduced phase spectrum; calculating a phase difference according to the noise-reduced phase spectrum, and amplifying the phase difference to obtain an amplified phase difference; reconstructing the amplitude spectrum and the amplified phase difference by using inverse Fourier transform to obtain the amplified vibration video.

[0010] Preferably, the vibration displacement of the cable in the amplified vibration video is obtained by using the centerline detection algorithm, comprising: obtaining a candidate centerline of the cable at a pixel level in the amplified vibration video; determining a target centerline of the cable at a sub-pixel level according to the candidate centerline; obtaining the vibration displacement of the cable according to the target centerline.

[0011] Preferably, the preset subspace identification method is a data-driven random subspace identification method.

[0012] Preferably, the high-order modes of the cable are obtained by using the preset subspace identification method according to the vibration displacement, comprising: constructing a Hankel matrix according to the vibration displacement; performing projection transformation on the Hankel matrix to obtain a projection matrix; respectively performing QR decomposition and singular value decomposition on the projection matrix, and calculating eigenvalues and eigenvectors by using a least square method; According to the eigenvalue and the eigenvector, the high-order mode shape of the cable is obtained.

[0013] Preferably, the intermediate half-wavelength of any two high-order mode shapes is calculated, and the cable force of the cable is determined according to the intermediate half-wavelength, including: The cable force of the cable is calculated by the following formula:

[0014] wherein, T represents the cable force of the cable, m represents the unit length mass of the cable, L p represents the intermediate half-wavelength of the first p high-order mode shape, f p represents the first p frequency of the cable, L q represents the intermediate half-wavelength of the second q high-order mode shape, f q represents the second q frequency of the cable, p and q is a positive integer greater than or equal to 3.

[0015] Another aspect of the present application provides a cable force identification device based on high-order mode shape, including: An acquisition module is configured to acquire a vibration video of a cable. An amplification module is configured to amplify the vibration video by using a phase-based motion amplification algorithm to obtain an amplified vibration video. A vibration displacement acquisition module is configured to acquire a vibration displacement of the cable in the amplified vibration video by using a center line detection algorithm. A high-order mode shape acquisition module is configured to acquire a high-order mode shape of the cable by using a preset subspace identification method according to the vibration displacement. A cable force determination module is configured to calculate an intermediate half-wavelength of any two high-order mode shapes, and determine a cable force of the cable according to the intermediate half-wavelength.

[0016] Still another aspect of the present application provides an electronic device, including: A memory is configured to store a computer program. A processor is configured to execute the computer program to implement the steps of the cable force identification method based on high-order mode shape as described above.

[0017] Still another aspect of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the cable force identification method based on high-order mode shape as described above.

[0018] The present application has at least the following beneficial effects: The present application obtains the vibration video of the cable, uses the phase-based motion magnification algorithm to magnify the vibration video, obtains the magnified vibration video, uses the center line detection algorithm to obtain the vibration displacement of the cable in the magnified vibration video, uses the preset subspace identification method to obtain the high-order mode of the cable according to the vibration displacement, calculates the intermediate half wavelength of any two high-order modes, and determines the cable force of the cable according to the intermediate half wavelength. When calculating the cable force of the cable, the intermediate half wavelength of the high-order mode is used to replace the effective length of the cable, so that the influence of the complex boundary condition on the calculation of the effective length of the cable can be eliminated, and the identification accuracy of the cable force of the bridge cable can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A flowchart of a cable force identification method based on high-order mode provided by the embodiment of the present application is shown in the figure. Figure 2 A schematic diagram of the intensity of the vibration video image provided by the embodiment of the present application is shown in the figure. Figure 3 A principle diagram of the center line detection algorithm provided by the embodiment of the present application is shown in the figure. Figure 4 An equivalent model diagram of the high-order mode provided by the embodiment of the present application is shown in the figure. Figure 5 A schematic diagram of the vibration displacement identification result provided by the embodiment of the present application is shown in the figure. Figure 6 A schematic diagram of the high-order mode identification result provided by the embodiment of the present application is shown in the figure. Figure 7 A structural schematic diagram of a cable force identification device based on high-order mode provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0021] The core of the present application is to provide a cable force identification method, device, equipment and medium based on high-order mode, which can eliminate the influence of complex boundary conditions on the calculation of the effective length of the cable, thereby improving the identification accuracy of the cable force of the bridge cable.

[0022] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0023] The embodiment of the present application provides a cable force identification method based on high-order mode. Figure 1 The method comprises the following steps. In step S110, the vibration video of the cable is obtained.

[0024] In the embodiment of the present application, the fixed camera can be used to collect the slight vibration video of the cable under environmental excitation.

[0025] Optionally, in the above embodiment, after the vibration video of the cable is obtained, the vibration video can be preprocessed to eliminate the noise information in the vibration video. In specific implementation, the digital image processing software can be used to perform preprocessing such as cropping, rotating and scaling on the vibration video image, so as to preliminarily eliminate the noise information in the image sequence, avoid the noise being enlarged at the same proportion when the video motion is enlarged in the subsequent step, and thus eliminate the influence of the noise on the video enlargement result.

[0026] In step S120, the phase-based motion magnification algorithm is used to enlarge the vibration video, so as to obtain the enlarged vibration video.

[0027] In the embodiment of the present application, the vibration amplitude of the cable under environmental load (such as wind and vehicle load) is usually very small and difficult to measure. In this case, the traditional computer vision-based displacement measurement method is no longer applicable, and the phase-based motion magnification (PMM) algorithm is an effective method, which can magnify the slight vibration of the cable to be visible, so as to track by using the target tracking algorithm.

[0028] In step S130, the center line detection algorithm is used to obtain the vibration displacement of the cable in the enlarged vibration video.

[0029] In the embodiment of the present application, the center line detection algorithm comprises two parts of pixel-level coarse search and sub-pixel-level accurate search. The purpose of the pixel-level coarse search is to determine the approximate position of the cable in the image sequence, and the purpose of the sub-pixel-level accurate search is to accurately calculate the center line position of the cable. After the center line position of the cable is determined, any point on the center line of the cable is selected as a tracking point, and the target tracking algorithm is used for tracking, so as to obtain the vibration displacement of the cable in the enlarged vibration video.

[0030] In step S140, according to the vibration displacement, a preset subspace identification method is used to obtain the high-order mode of the cable.

[0031] In a specific implementation, a data-driven random subspace identification method (Date-SSI) can be used to identify the high-order mode of the cable. The identification method has the advantages of strong noise resistance and high identification accuracy, and has been widely used in pure output structural mode identification.

[0032] In step S150, the intermediate half-wavelength of any two high-order modes is calculated, and the cable force of the cable is determined according to the intermediate half-wavelength.

[0033] It should be noted that the frequency method for calculating the cable force in the prior art is only applicable to the case where the boundary conditions at both ends of the cable are simply supported, and the bending stiffness and effective length of the cable need to be determined. In general, the bending stiffness of the cable can be found in the design drawing. However, the physical properties of the cable may degrade due to corrosion and corrosion of the cable during use, resulting in changes in the actual bending stiffness and making it difficult to accurately measure. In addition, the effective length of the cable is greatly affected by the boundary conditions at both ends of the cable. For cables in actual engineering, the boundary conditions are often between simply supported and clamped, which poses a challenge to the calculation of the effective length.

[0034] In the embodiment of the present application, regardless of whether the boundary conditions at both ends of the cable model are simply supported or clamped, the boundary conditions at both ends of the cable for any intermediate half-wave of the high-order mode can be considered to be simply supported. Therefore, any intermediate half-wave of the high-order mode is no longer affected by the boundary conditions at both ends, and the intermediate half-wavelength of the high-order mode can be used to calculate the cable force instead of the effective length of the cable. By calculating the intermediate half-wavelength of any two high-order modes, and substituting it into the cable force-frequency calculation formula as the effective length of the cable, the cable force under the intermediate half-wavelength of any two high-order modes can be obtained by solving the two formulas, thereby eliminating the influence of the bending stiffness and complex boundary conditions of the cable.

[0035] As described above, the cable force identification method based on higher-order vibration modes provided in this invention acquires a vibration video of the cable, amplifies the vibration video using a phase-based motion amplification algorithm to obtain an amplified vibration video, uses a centerline detection algorithm to obtain the vibration displacement of the cable in the amplified vibration video, and uses a preset subspace identification method to obtain the higher-order vibration modes of the cable based on the vibration displacement. The middle half-wavelength of any two higher-order vibration modes is calculated, and the cable force is determined based on the middle half-wavelength. By using the scheme of this application, the middle half-wavelength of the higher-order vibration modes is used instead of the effective length of the cable when calculating the cable force, which can eliminate the influence of complex boundary conditions on the calculation of the effective length of the cable, thereby improving the identification accuracy of bridge cable force.

[0036] Optionally, in the above embodiments, step S120 includes: Perform a 2D Fourier transform on the vibration video to obtain a frequency domain image sequence; The frequency domain image sequence is decomposed using a complex, controllable pyramid to obtain the amplitude spectrum and phase spectrum; The phase spectrum is denoised using a 2D Gabor wavelet filter to obtain the denoised phase spectrum. The phase difference is calculated based on the phase spectrum after noise reduction, and the phase difference is amplified to obtain the amplified phase difference. The amplitude spectrum and the amplified phase difference are reconstructed using inverse Fourier transform to obtain the amplified vibration video.

[0037] In this embodiment of the invention, the vibration video is first subjected to a 2D Fast Fourier Transform (FFT) to obtain a frequency domain image sequence. Then, the frequency domain image sequence is decomposed using a Complex Steerable Pyramid Decomposition (CSPD) to obtain the amplitude spectrum, phase spectrum, low-pass residual, and high-pass residual. Next, the phase spectrum is denoised using a 2D Gabor wavelet filter to obtain a denoised phase spectrum. The phase difference is then calculated based on the denoised phase spectrum and amplified using a preset amplification factor to obtain an amplified phase difference. Finally, the amplified phase difference is combined with the amplitude spectrum, low-pass residual, and high-pass residual, and reconstructed using an inverse Fourier transform to obtain the amplified vibration video.

[0038] It should be noted that in the image sequence of the vibration video, at any position x In t Image intensity at time I It is a function of time and position. Let's take the lateral vibration of a cable as an example to illustrate this, such as... Figure 2 As shown, when hour, At t greater than 0, the cable has a small displacement x at position , and the image intensity becomes . The image intensity at time 0 and time t can be expressed by Fourier series decomposition as a sum of complex sinusoidal signals corresponding to the frequency . That is:

[0039]

[0040] where is the amplitude, is the phase, is the natural frequency of the cable, i is the conjugate complex number, and .

[0041] t The phase difference between time and time 0 is:

[0042] After the phase difference is amplified by times, the image intensity is:

[0043] where is the preset amplification factor.

[0044] Optionally, in the above embodiment, step S130 comprises: obtaining a candidate center line of the cable at the pixel level in the amplified vibration video; determining a target center line of the cable at the sub-pixel level according to the candidate center line; obtaining the vibration displacement of the cable according to the target center line.

[0045] In the embodiment of the present application, as shown in Figure 3 , the purpose of the pixel-level coarse search is to determine the approximate position of the cable in the image sequence, and the purpose of the sub-pixel-level accurate search is to accurately calculate the position of the center line of the cable. First, the left and right sides of the image in the amplified vibration video are searched in the vertical direction by using a square frame respectively, and the candidate center points (i.e. P l and P r); then the rectangular frame is moved horizontally between the candidate center points to search, and the pixel-level candidate center line of the cable, i.e. the rough center line, is obtained to determine the approximate position of the cable. Then, the bicubic interpolation is used to difference the gray value of the search frame to determine the sub-pixel level target center line of the cable, i.e. the accurate center line. Finally, any point on the cable center line is selected as a tracking point, and the target tracking algorithm is used for tracking, so that the vibration displacement of the cable in the zoomed-in vibration video is obtained.

[0046] Optionally, in the above embodiment, the step S140 comprises: constructing a Hankel matrix according to the vibration displacement; performing projection transformation on the Hankel matrix to obtain a projection matrix; performing QR decomposition and singular value decomposition on the projection matrix respectively, and calculating eigenvalues and eigenvectors by using a least square method; obtaining high-order vibration modes of the cable according to the eigenvalues and the eigenvectors.

[0047] In the embodiment of the application, the input oscillation system can be represented by a data-driven stochastic subspace identification method using a state space as follows:

[0048] wherein, and are state vectors and output vectors of the system at time t , respectively, is a state vector of the system at time , A and C are a space state matrix and an output matrix, respectively, and are process noise and measurement noise, respectively.

[0049] A Hankel matrix is constructed by using the vibration displacement obtained by the foregoing steps H , and H is divided into a past output matrix and a future output matrix :

[0050] wherein, 2 j and k are the number of rows and the number of columns of the Hankel matrix, respectively, is a column vector composed of the vibration displacement, and are the past output matrix and the future output matrix of the Hankel matrix, respectively.

[0051] The matrix Projection to matrix Upper compute orthogonal projection matrix , and to QR decomposition can be obtained:

[0052] According to the subspace system identification theory, the projection matrix Can be decomposed into the observation matrix And Kalman filter state matrix The product, that is:

[0053] The singular value decomposition (Singular value decomposition, SVD) of the projection matrix Can be obtained:

[0054] Wherein, , , And All are orthogonal matrix; Diagonal matrix.

[0055] According to the above formula can be obtained:

[0056]

[0057] Because And Irrelevant to the system state, can be calculated by using the least square method space state matrix A And output matrix C , that is:

[0058] When the eigenvalue A And eigenvector Of the space state matrix Is obtained, the frequency , damping ratio And mode shape of the cable can be calculated by using the above formula, that is:

[0059]

[0060]

[0061] ​This allows for the automatic acquisition of higher-order vibration modes of the cables.

[0062] Optionally, in the above embodiments, step S150 includes: The cable force is calculated using the following formula:

[0063] in, T The tension of the cable represents the cable force. m This represents the mass per unit length of the cable. L p Representing the p The middle half wavelength of higher-order vibration modes, f p The representative of Lasso p First frequency, L q Representing the q The middle half wavelength of higher-order vibration modes, f q The representative of Lasso q First frequency, p and q It is a positive integer greater than or equal to 3.

[0064] It should be noted that the vibration equation of the cable can be expressed as:

[0065] in, EI For the bending stiffness of the cable, u ( x,t )for t The cable is in position x Vibration displacement at that location.

[0066] Assumption Substituting this into the above formula, we can obtain:

[0067] in, Let be the mode shape function of the cable. ,and .

[0068] To solve the above formula, we can substitute it with:

[0069] in, , ; B 1. B 2. B 3 and B 4 represents the four coefficients determined based on the initial and boundary conditions.

[0070] When the boundary condition of the cable is simply supported, the boundary condition can be expressed as:

[0071] wherein, L is the effective length of the cable.

[0072] Solving the above formula, the calculation formula of the cable force when the boundary condition of the two ends is simply supported can be obtained as:

[0073] wherein, n is the order of the frequency of the cable; f n is the frequency of the cable. n

[0074] It can be understood that the above formula for calculating the cable force is only applicable when the boundary condition of the two ends is simply supported, and the bending stiffness EI and the effective length L of the cable are known.

[0075] In the embodiment of the application, the cable force can be determined according to the middle half wavelength regardless of whether the boundary condition of the two ends of the cable model is simply supported or fixed. Assuming that the boundary condition of the two ends of the cable model is fixed, the p ( ) order high-order mode of the cable can be as shown in FIG. 1. According to structural mechanics, for any one middle half wave of the Figure 4 order high-order mode of the cable, the boundary condition of the two nodes of the high-order mode can be considered as simply supported. Therefore, any one middle half wave of the high-order mode is no longer affected by the boundary condition of the two ends, and the middle half wavelength of the high-order mode can be used to replace the effective length of the cable to calculate the cable force, so as to obtain the cable force under the middle half wavelength of the p order high-order mode, that is: p

[0076] Similarly, the middle half wavelength q of the order mode of the cable can be calculated. L q The above formula can be obtained by substituting the middle half wavelength of the q order high-order mode into the above formula, that is:

[0077] By solving the above two formulas, the cable force under the middle half wavelength of any two high-order modes can be obtained as: ​​

[0078] Thus, the bending stiffness of the cable is eliminated EI and the influence of boundary conditions, suitable for cable force calculation under complex boundary conditions.

[0079] Next, the application of the cable force identification method based on high-order modes provided by the present application will be described in combination with specific implementation cases.

[0080] Taking a certain long-span highway cable-stayed bridge as an example, the cable force identification method based on high-order modes provided by the present application is applied to measure the cable force of the cable. A fixed camera with a resolution of 1920x1080 pixels and a sampling frequency of 60 Hz is used to record the vibration video of the cable. The distance from the fixed camera to the test cable is about 120 m. In order to reduce the influence of the interlaced cables on the mode identification, only the vibration video of the downstream cable is collected. The vibration amplitude of the cable in the video is very small and almost invisible to the naked eye.

[0081] Taking a certain cable as an example, the cable force is measured by using the technical solution provided by the present application. The cable length is 136.829 m, and the unit length mass is 53.6 kg / m. The vibration video of the cable is cropped, and the image resolution is reduced to 800x120 pixels to improve the processing speed of the centerline detection algorithm. Then the improved motion magnification algorithm is used to magnify the vibration video of the cable, and the frequency band of the magnification is set to , and the magnification multiple is set to . The vibration displacement of the cable is extracted from the magnified video by using the centerline detection algorithm, as shown in Figure 5 . According to the vibration displacement of the cable, the 7th and 8th modes of the cable are automatically identified by using the Data-SSI algorithm, as shown in Figure 6 .

[0082] According to the middle half wavelength of the high-order mode of the cable, the cable force is calculated by using the above formula, and the results are shown in Table 1.

[0083] Table 1 Comparison of cable force identification results

[0084] As can be seen from Table 1, the relative error of the cable force determined by using the technical solution provided by the present application and the accurate value of the cable force is 2.37%, which meets the engineering precision requirement of 5%. The results show that the estimation of the cable force by using the middle half wavelength of the high-order mode has high precision, and the cable force can be identified even if the boundary conditions and the bending stiffness of the cable are unknown. The technical solution provided by the present application indirectly considers the bending stiffness of the cable, and successfully eliminates the influence of the boundary conditions on the effective length of the cable, significantly improves the measurement precision of the cable force, and has good application prospect in practical engineering.

[0085] In another aspect, the application provides a cable force identification device based on high-order mode, which can be used in conjunction with the method described above.

[0086] Referring to Figure 7 The device comprises: The acquisition module 710 is configured to acquire a vibration video of the cable. The amplification module 720 is configured to amplify the vibration video by using a phase-based motion magnification algorithm to obtain an amplified vibration video. The vibration displacement acquisition module 730 is configured to acquire the vibration displacement of the cable in the amplified vibration video by using a centerline detection algorithm. The high-order mode acquisition module 740 is configured to acquire the high-order mode of the cable by using a preset subspace identification method according to the vibration displacement. The cable force determination module 750 is configured to calculate the intermediate half-wavelength of any two high-order modes and determine the cable force according to the intermediate half-wavelength.

[0087] As can be seen from the above, the cable force identification device based on high-order mode provided by the application can acquire a vibration video of the cable, amplify the vibration video by using a phase-based motion magnification algorithm to obtain an amplified vibration video, acquire the vibration displacement of the cable in the amplified vibration video by using a centerline detection algorithm, acquire the high-order mode of the cable by using a preset subspace identification method according to the vibration displacement, calculate the intermediate half-wavelength of any two high-order modes, and determine the cable force according to the intermediate half-wavelength. By using the intermediate half-wavelength of the high-order mode to replace the effective length of the cable when calculating the cable force, the application can eliminate the influence of complex boundary conditions on the calculation of the effective length of the cable, thereby improving the identification accuracy of the cable force of the bridge.

[0088] In another aspect, the application provides an electronic device, which comprises: The memory is configured to store a computer program. The processor is configured to execute the computer program to implement the steps of the cable force identification method based on high-order mode described above.

[0089] In another aspect, the application provides a computer readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the cable force identification method based on high-order mode described above are implemented.

[0090] Embodiments of the present application are described herein with reference to the drawings, wherein: The embodiments are described in progressively greater detail throughout the present specification. Each embodiment is directed to the differences over the other embodiments, and each embodiment shares the features of the other embodiments. It is further noted that the terms first, second, etc. are used merely as label to distinguish one element from another, and do not necessarily indicate a physical, chronological or relational order of such elements. Also, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0091] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-order mode-based cable force identification method for a cable, characterized in that, The method comprises the following steps: obtaining a vibration video of a cable; amplifying the vibration video by using a phase-based motion magnification algorithm to obtain an amplified vibration video; obtaining a vibration displacement of the cable in the amplified vibration video by using a center line detection algorithm; obtaining high-order vibration modes of the cable by using a preset subspace identification method according to the vibration displacement; calculating a middle half wavelength of any two of the high-order vibration modes, and determining a cable force of the cable according to the middle half wavelength.

2. The high mode shape based cable force identification method according to claim 1, wherein, After the step of obtaining the vibration video of the cable, the method further comprises the following steps: preprocessing the vibration video to remove noise information in the vibration video.

3. The high mode shape based cable force identification method according to claim 1, wherein, The step of amplifying the vibration video by using the phase-based motion magnification algorithm to obtain the amplified vibration video comprises the following steps: performing 2D Fourier transform on the vibration video to obtain a frequency domain image sequence; decomposing the frequency domain image sequence by using a complex steerable pyramid to obtain an amplitude spectrum and a phase spectrum; performing noise reduction processing on the phase spectrum by using a 2D Gabor wavelet filter to obtain a noise-reduced phase spectrum; calculating a phase difference according to the noise-reduced phase spectrum, and amplifying the phase difference to obtain an amplified phase difference; reconstructing the amplitude spectrum and the amplified phase difference by using inverse Fourier transform to obtain the amplified vibration video.

4. The high mode shape based cable force identification method according to claim 1, wherein, The step of obtaining the vibration displacement of the cable in the amplified vibration video by using the center line detection algorithm comprises the following steps: obtaining a candidate center line of the cable at a pixel level in the amplified vibration video; determining a target center line of the cable at a sub-pixel level according to the candidate center line; obtaining the vibration displacement of the cable according to the target center line.

5. The high mode shape based cable force identification method according to claim 1, wherein, The preset subspace identification method is a data-driven random subspace identification method.

6. The high mode shape based cable force identification method according to claim 5, wherein, The step of obtaining the high-order vibration modes of the cable by using the preset subspace identification method according to the vibration displacement comprises the following steps: constructing a Hankel matrix according to the vibration displacement; performing projection transformation on the Hankel matrix to obtain a projection matrix; performing QR decomposition and singular value decomposition on the projection matrix respectively, and calculating eigenvalues and eigenvectors by using a least square method; obtaining the high-order vibration modes of the cable according to the eigenvalues and the eigenvectors.

7. The high mode shape based cable force identification method according to claim 1, wherein, The step of calculating the middle half wavelength of any two of the high-order vibration modes, and determining the cable force of the cable according to the middle half wavelength comprises the following steps: calculating the cable force of the cable by using the following formula: ； wherein, T a cable force representative of the cable, m a unit length mass representative of the cable, L p a middle half-wavelength representative of the high order mode of the p f p a frequency representative of the cable, p a middle half-wavelength representative of the high order mode of the L q a frequency representative of the cable, q a middle half-wavelength representative of the high order mode of the f q a frequency representative of the cable, q and p and q is a positive integer greater than or equal to 3.​ 8. A cable force identification device based on higher-order vibration modes, characterized in that, The method comprises the following steps: an obtaining module, configured to obtain a vibration video of a cable; an amplifying module, configured to amplify the vibration video by using a phase-based motion magnification algorithm to obtain an amplified vibration video; a vibration displacement obtaining module, configured to obtain a vibration displacement of the cable in the amplified vibration video by using a center line detection algorithm; a high-order vibration mode obtaining module, configured to obtain high-order vibration modes of the cable by using a preset subspace identification method according to the vibration displacement; a cable force determining module, configured to calculate a middle half wavelength of any two of the high-order vibration modes, and determine a cable force of the cable according to the middle half wavelength.

9. An electronic device, comprising: The method comprises the following steps: a memory, configured to store a computer program; A processor for implementing the steps of the high-order mode-based cable force identification method according to any one of claims 1 to 7 when the computer program is executed.

10. A computer-readable storage medium, characterized in that, A computer readable storage medium having stored thereon a computer program, the computer program being executed by a processor to implement the steps of the high-order mode-based cable force identification method according to any one of claims 1 to 7.

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