Nondestructive health detection method and device for offshore wind turbine pile foundation and storage medium

Abstract

The invention discloses an offshore wind turbine pile foundation nondestructive health detection method and device and a storage medium, and belongs to the field of pile foundation structure safety detection.The method comprises the following steps that a pile body is equally segmented to form a plurality of test units, image collection is conducted on the test units based on a mobile three-dimensional digital image correlation method, and test images are obtained; then performing data processing on the test image to obtain full-field displacement time history response of each segment; carrying out segmented frequency domain identification to obtain each segmented vibration mode; carrying out overall vibration mode reconstruction to obtain an overall spliced vibration mode; and comparing the undamaged vibration mode of the structure with the integral splicing vibration mode, and identifying the damaged position of the offshore wind turbine pile foundation by combining the power fingerprint index. According to the method, the overall splicing vibration mode can be obtained, and the defects that test information with high space density is difficult to obtain and the cost is high in actual operation of a traditional dynamic test method using an acceleration sensor are overcome, so that a more accurate damage position identification result is obtained.

Description

Technical Field

[0001] This invention relates to a non-destructive health testing method, device, and storage medium for offshore wind turbine pile foundations, belonging to the field of pile foundation structure safety testing technology. Background Technology

[0002] With the increasing global demand for clean energy, offshore wind energy, as a clean and renewable energy source, is receiving increasing attention. However, the construction and operation of offshore wind farms face numerous technical challenges, among which damage to the turbine foundations and piles is a major issue. Damage to the turbine foundations and piles not only leads to changes in the natural frequencies and modes of the turbine support structure but may also reduce the buckling capacity of the structure, seriously threatening the stable operation and economic benefits of the offshore wind farm.

[0003] Existing methods for identifying damage to offshore wind turbine foundations and piles mainly rely on vibration sensors such as accelerometers to measure vibration response and obtain structural vibration characteristics, and then identify damage through dynamic fingerprint indicators. Since the spatial resolution of structural mode shapes has a direct impact on the accuracy of damage identification based on structural mode shapes, a large number of vibration sensors need to be densely deployed to collect high-density structural vibration information. However, this brings the following problems: (1) The cost of sensors, installation and acquisition is high; (2) The sensors themselves have a certain weight, and the installation of a large number of sensors will bring a lot of extra mass and damping, affecting the accuracy of mode shape identification. This makes it difficult to achieve high spatial accuracy testing in actual operation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a non-destructive health detection method, device and storage medium for offshore wind turbine pile foundations, which can obtain the overall spliced ​​vibration mode and overcome the defects of traditional dynamic testing methods using accelerometers in practical operation, which are difficult to obtain test information with high spatial density and have high cost, thereby obtaining more accurate damage location identification results.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for non-destructive health testing of offshore wind turbine pile foundations, comprising the following steps:

[0007] The pile body is divided into several test units in equal segments. The test units are image acquired based on the mobile three-dimensional digital image correlation method to obtain test images. Then, the test images are processed using the three-dimensional digital image correlation method to obtain the full field displacement time history response of each segment.

[0008] The segmented full-field displacement time history response is segmented into frequency domains to obtain the mode shapes of each segment.

[0009] The mode shapes of each segment are reconstructed as a whole to obtain the overall spliced ​​mode shape.

[0010] The undamaged vibration modes of the structure are obtained, and the undamaged vibration modes of the structure are compared with the overall spliced ​​vibration modes. Combined with dynamic fingerprint indicators, the location of damage to the offshore wind turbine pile foundation is identified.

[0011] The test images obtained by acquiring images of the test unit based on the mobile three-dimensional digital image correlation method include:

[0012] After the synchronously controlled binocular camera system begins dynamic testing and image acquisition on the current test unit, the camera's field of view is aligned with the next test unit by adjusting the support.

[0013] The step of segmenting the full-field displacement time history response into segments and identifying the frequency domain of each segment to obtain the mode shapes of each segment includes:

[0014] Based on the statistical index of the normal distribution rate density function, the displacement time history response within a small range of the same cross-sectional height in the full field displacement time history response is merged, and the unit test model is reduced to a one-dimensional line model.

[0015] A low-pass filter is used to denoise the displacement time history response of the one-dimensional line model to obtain the denoised displacement time history response signal.

[0016] One-dimensional vibration modes are extracted from the noise-reduced displacement time history response signal based on the environmental excitation method.

[0017] The process of reconstructing the overall mode shape from each segment to obtain the overall spliced ​​mode shape includes:

[0018] The test image is processed by combining the ORB feature detection algorithm and the fast approximate nearest neighbor matching algorithm to match the overlapping area images of adjacent test units and obtain the pixel coordinate representation of a series of matching points in two adjacent segmented test images.

[0019] Based on the eight-point method, the pixel coordinate representation of the matching points is processed to establish a spatial transformation matrix of adjacent test unit images. Then, the pixel coordinate position of each unit node in the adjacent segment image is found through the spatial transformation matrix.

[0020] Based on the pixel coordinates of each unit node, the one-dimensional vibration modes of each test unit are spliced ​​together to obtain the overall vibration mode after splicing.

[0021] The overall spliced ​​mode shape is obtained by denoising the spliced ​​mode shape using the wavelet threshold denoising method.

[0022] The acquisition of the undamaged vibration modes of the structure includes:

[0023] A finite element model was established based on test data when the pile body was undamaged, and the vibration mode of the structure without damage was obtained from the finite element model.

[0024] The dynamic fingerprint index includes flexibility mode, curvature mode, and modal strain energy.

[0025] Secondly, the present invention provides a non-destructive health testing device for offshore wind turbine pile foundations, characterized in that it comprises:

[0026] The signal acquisition module is used to divide the pile body into several test units in equal segments. The test units are image acquired based on the mobile three-dimensional digital image correlation method to obtain test images. Then, the three-dimensional digital image correlation method is used to process the test images to obtain the full field displacement time history response of each segment.

[0027] The segmented frequency domain identification module is used to perform segmented frequency domain identification on the full-field displacement time history response of each segment to obtain the mode shape of each segment.

[0028] The overall mode shape reconstruction module is used to reconstruct the overall mode shape of each segment to obtain the overall spliced ​​mode shape.

[0029] The damage identification module is used to obtain the undamaged vibration modes of the structure, compare the undamaged vibration modes with the overall spliced ​​vibration modes, and combine them with dynamic fingerprint indicators to identify the location of damage to the offshore wind turbine pile foundation.

[0030] Thirdly, the present invention provides a computer-readable storage medium storing a computer program / instruction thereon, which, when executed by a processor, implements the steps of the described method for non-destructive health testing of offshore wind turbine pile foundations.

[0031] The beneficial effects of this invention are as follows: This invention provides a method, device, and storage medium for non-destructive health testing of offshore wind turbine pile foundations. It acquires test images of the test unit based on a mobile three-dimensional digital image correlation (3D-DIC) method, then processes the test images using the 3D-DIC method. A mobile segmented 3D-DIC dynamic measurement strategy is proposed to obtain complete pile foundation vibration modes (overall spliced ​​vibration modes) with high spatial resolution. This overcomes the shortcomings of traditional dynamic testing methods using accelerometers, which struggle to obtain high spatial density test information and are costly in practice, thus obtaining more accurate damage location identification results. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a non-destructive health testing method for offshore wind turbine pile foundations provided in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the established mobile 3d-DIC segmented dynamic measurement principle provided in an embodiment of the present invention;

[0034] Figure 3 This is a flowchart of the image feature matching algorithm provided in an embodiment of the present invention;

[0035] Figure 4 This is a diagram showing the damage identification results in Embodiment 2 of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, this invention discloses a non-destructive health testing method for offshore wind turbine pile foundations, comprising the following steps:

[0039] Step 1: Divide the pile body into several test units in equal segments. Use the mobile three-dimensional digital image correlation method to acquire test images of the test units. Then, use the three-dimensional digital image correlation method to process the test images and obtain the full-field displacement time history response of each segment.

[0040] Step 2: Perform segmented frequency domain identification on the full-field displacement time history response of each segment to obtain the mode shape of each segment.

[0041] Step 3: Reconstruct the overall vibration mode of each segment to obtain the overall spliced ​​vibration mode.

[0042] In this invention, the spatial density of the signal acquisition of the test structure is called the spatial resolution. The overall spliced ​​vibration mode obtained by using 3D-DIC to carry out the test contains vibration signals with high spatial density.

[0043] Step 4: Obtain the undamaged vibration mode of the structure, compare the undamaged vibration mode with the overall spliced ​​vibration mode, and combine with the dynamic fingerprint index to identify the location of damage to the offshore wind turbine pile foundation.

[0044] This invention employs the non-contact optical measurement method DIC and proposes a mobile segmented 3d-DIC dynamic measurement strategy to obtain complete pile foundation vibration modes with high spatial resolution. This overcomes the shortcomings of traditional dynamic testing methods using accelerometers, which are difficult to obtain high spatial density test information and are costly in actual operation, thereby obtaining more accurate damage location identification results.

[0045] Example 2

[0046] like Figure 1 As shown, this invention discloses a non-destructive health testing method for offshore wind turbine pile foundations, based on 3D-DIC splicing measurement, including the following steps:

[0047] Step 1, Signal Acquisition. The dynamic response images of offshore wind turbine pile foundations are acquired using a mobile three-dimensional digital image correlation (3D-DIC) method. The specific implementation process is as follows: (1) Divide the pile body into several test units, and name the junctions of the units as nodes. (2) During each test, a complete image of the target unit and images of the boundary areas of adjacent units (forming an overlap of about 10% between test areas) need to be captured, sequentially numbered as Test Area 1, Test Area 2, etc. (3) Using a synchronously controlled binocular camera system, a step-by-step testing strategy is adopted: after completing the dynamic test and image acquisition of Test Area 1, the support is adjusted so that the camera's field of view is aligned with Test Area 2 for subsequent testing, and so on, to complete the measurement of the entire pile body. Figure 2 As shown. Finally, a digital image correlation algorithm is applied to process the image data of each survey area independently to obtain the full-field displacement time history response of each segment.

[0048] Step 2, segmented frequency domain identification. (1) Dimension reduction processing is carried out. Under the premise of meeting the test accuracy requirements, the displacement time history response within a small range of the same cross-sectional height of the displacement field is merged based on the statistical index of the normal distribution rate density function, and each unit test model is simplified into a one-dimensional line model. (2) A low-pass filter is used to denoise the displacement time history response of each unit line model after dimensional reduction processing. (3) Frequency domain identification is carried out based on the environmental excitation method (NExT / ERA), and the one-dimensional mode shape of each unit is extracted from the denoised signal.

[0049] Step 3, overall mode shape reconstruction. (1) Image matching is performed based on the test images from Step 1. For example... Figure 3 As shown, ORB feature detection (FAST feature points + BRIEF descriptors) and fast approximate nearest neighbor (FLANN) matching algorithm are used together to match the overlapping area images and obtain the pixel coordinate expression of a series of matching points in the two segmented images. Based on the eight-point method, the pixel coordinate expression of the matching points is processed to establish the spatial transformation matrix of the adjacent test area images and determine the pixel coordinate mapping relationship of the matching points. Thus, the pixel coordinate position of the unit node in the adjacent segment image is found through the transformation matrix. (2) Match all segments to achieve the matching of all unit nodes in the image. Based on the pixel coordinate position of each pixel coordinate position, the one-dimensional vibration mode of each unit obtained in step two is spliced. Since the identification results of the vibration mode of the same node in different segments may be inconsistent due to the different normalized dimensions inside the unit, but they are consistent in practice, it is necessary to perform normalization between units to achieve the splicing of the one-dimensional vibration mode of each unit. (3) The overall vibration mode after splicing is denoised by the wavelet threshold denoising method to obtain a smooth overall spliced ​​vibration mode.

[0050] Step four, damage identification. A finite element model is established using test data from the undamaged state of the structure to obtain the undamaged vibration modes. Based on the undamaged vibration modes and the measured overall spliced ​​vibration modes obtained in step three, combined with dynamic fingerprint indicators, including flexibility modes, curvature modes, modal strain energy, and other derived indicators, the location of damage to the offshore wind turbine pile foundation is identified. For large wind turbine structures, the measurement accuracy of low-order vibration modes is relatively high in the actual working environment. Since flexibility modes are mainly determined by low-order modes, they are more sensitive to damage in low-order modes and are therefore selected as a superior damage indicator for this system. Figure 4 As shown in the figure, a damage identification example with various damage levels at cell 5 is presented. It can be seen from the figure that in the damage identification of different damage levels based on the method of this invention, the maximum value of the flexibility modal difference index always appears at node 5, biased towards cell 5. Therefore, the damage location can be identified as cell 5.

[0051] This invention employs the non-contact optical measurement method DIC and proposes a mobile segmented 3d-DIC dynamic measurement strategy. Through image feature matching, dimensionality reduction processing, and signal denoising, it can solve the problems of high cost and practical difficulty in obtaining the overall spliced ​​vibration mode in traditional dynamic testing, as well as the limitation of the DIC test area by the camera's measurement field of view, thereby obtaining more accurate damage location identification results.

[0052] Example 3

[0053] This example discloses a non-destructive health testing device for offshore wind turbine pile foundations, including:

[0054] The signal acquisition module is used to divide the pile body into several test units in equal segments. The test units are image acquired based on the mobile three-dimensional digital image correlation method to obtain test images. Then, the three-dimensional digital image correlation method is used to process the test images to obtain the full field displacement time history response of each segment.

[0055] The segmented frequency domain identification module is used to perform segmented frequency domain identification on the full-field displacement time history response of each segment to obtain the mode shape of each segment.

[0056] The overall mode shape reconstruction module is used to reconstruct the overall mode shape of each segment to obtain the overall spliced ​​mode shape.

[0057] The damage identification module is used to obtain the undamaged vibration modes of the structure, compare the undamaged vibration modes with the overall spliced ​​vibration modes, and combine them with dynamic fingerprint indicators to identify the location of damage in the offshore wind turbine pile foundation.

[0058] Example 4

[0059] This embodiment describes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method described in Embodiment 1 or 2.

[0060] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0061] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0062] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0063] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A non-destructive health testing method for offshore wind turbine pile foundations, characterized in that: Includes the following steps: The pile body is divided into several test units in equal segments. The test units are image acquired based on the mobile three-dimensional digital image correlation method to obtain test images. Then, the test images are processed using the three-dimensional digital image correlation method to obtain the full field displacement time history response of each segment. The segmented full-field displacement time history response is segmented into frequency domains to obtain the mode shapes of each segment. The mode shapes of each segment are reconstructed as a whole to obtain the overall spliced ​​mode shape. The undamaged vibration modes of the structure are obtained, and the undamaged vibration modes of the structure are compared with the overall spliced ​​vibration modes. Combined with dynamic fingerprint indicators, the location of damage to the offshore wind turbine pile foundation is identified.

2. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 1, characterized in that: The test images obtained by acquiring images of the test unit based on the mobile three-dimensional digital image correlation method include: After the synchronously controlled binocular camera system begins dynamic testing and image acquisition on the current test unit, the camera's field of view is aligned with the next test unit by adjusting the support.

3. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 2, characterized in that: The step of segmenting the full-field displacement time history response into segments and identifying the frequency domain of each segment to obtain the mode shapes of each segment includes: Based on the statistical index of the normal distribution rate density function, the displacement time history response within a small range of the same cross-sectional height in the full field displacement time history response is merged, and the unit test model is reduced to a one-dimensional line model. A low-pass filter is used to denoise the displacement time history response of the one-dimensional line model to obtain the denoised displacement time history response signal. One-dimensional vibration modes are extracted from the noise-reduced displacement time history response signal based on the environmental excitation method.

4. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 3, characterized in that: The process of reconstructing the overall mode shape from each segment to obtain the overall spliced ​​mode shape includes: The test image is processed by combining the ORB feature detection algorithm and the fast approximate nearest neighbor matching algorithm to match the overlapping area images of adjacent test units and obtain the pixel coordinate representation of a series of matching points in two adjacent segmented test images. Based on the eight-point method, the pixel coordinate representation of the matching points is processed to establish a spatial transformation matrix of adjacent test unit images. Then, the pixel coordinate position of each unit node in the adjacent segment image is found through the spatial transformation matrix. Based on the pixel coordinates of each unit node, the one-dimensional vibration modes of each test unit are spliced ​​together to obtain the overall vibration mode after splicing. The overall spliced ​​mode shape is obtained by denoising the spliced ​​mode shape using the wavelet threshold denoising method.

5. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 4, characterized in that: The acquisition of the undamaged vibration mode of the structure includes: A finite element model was established based on test data when the pile body was undamaged, and the vibration modes of the undamaged structure were obtained from the finite element model.

6. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 5, characterized in that: The dynamic fingerprint index is a flexibility modality.

7. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 5, characterized in that: The dynamic fingerprint index is a curvature mode.

8. The non-destructive health testing method for offshore wind turbine pile foundations according to claim 5, characterized in that: The dynamic fingerprint index is modal strain energy.

9. A non-destructive health testing device for offshore wind turbine pile foundations, characterized in that: include: The signal acquisition module is used to divide the pile body into several test units in equal segments. The test units are image acquired based on the mobile three-dimensional digital image correlation method to obtain test images. Then, the three-dimensional digital image correlation method is used to process the test images to obtain the full field displacement time history response of each segment. The segmented frequency domain identification module is used to perform segmented frequency domain identification on the full-field displacement time history response of each segment to obtain the mode shape of each segment. The overall mode shape reconstruction module is used to reconstruct the overall mode shape of each segment to obtain the overall spliced ​​mode shape. The damage identification module is used to obtain the undamaged vibration modes of the structure, compare the undamaged vibration modes with the overall spliced ​​vibration modes, and combine them with dynamic fingerprint indicators to identify the location of damage to the offshore wind turbine pile foundation.

10. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that: When the computer program / instruction is executed by the processor, it implements the steps of the non-destructive health testing method for offshore wind turbine pile foundations as described in any one of claims 1-8.

Images