Long-distance non-contact cable force recognition device for laser array vibration measurement and cable force recognition method of long-distance non-contact cable force recognition device

Abstract

The invention relates to the technical field of bridge and structural engineering, in particular to a long-distance non-contact cable force recognition device for laser array vibration measurement and a cable force recognition method of the long-distance non-contact cable force recognition device. The device comprises a supporting assembly and a measuring assembly arranged above the supporting assembly. The measuring assembly comprises a substrate, a laser vibration meter, a laser range finder and a dipmeter; when the device is used for measuring a target cable, the laser vibration measurer projects a vibration measurement light beam to the target cable to obtain a measurement point, and the vibration response of the target cable at the measurement point is observed; a laser range finder projects a ranging beam to measure a distance, a dipmeter is combined to measure an included angle between a vibration measuring beam and a horizontal plane and an included angle between the ranging beam and the horizontal plane, and an included angle between the vibration measuring beam and a target cable and a distance between measuring points on the target cable are calculated so as to identify a vibration mode and a cable force of the target cable. The device provided by the invention can be suitable for long cables, short cables and long and short cables which have complex boundary conditions and are provided with restraining devices such as internal and external dampers.

Description

Technical Field

[0001] This invention relates to the field of bridge and structural engineering technology, and in particular to a long-distance non-contact cable force identification device and cable force identification method based on laser array vibration measurement. Background Technology

[0002] In large-scale infrastructure projects, cable structures are widely used in long-span structures and bridges due to their excellent axial load-bearing capacity. They are key components of cable-stayed bridges, suspension bridges, and through-arch bridges. Because they bear enormous axial forces, accurately determining the internal forces of the cables is crucial for assessing the structural condition during structural construction, operation and maintenance, and cable component replacement, and is of significant engineering importance.

[0003] There are two main methods for measuring and observing the axial force of cable structures. The first is to directly install force gauges or strain sensors near the cable end anchorage. This method requires direct sensor installation on the cable. However, for operational cable structures, adding or replacing sensors is very difficult. Furthermore, these sensors have issues such as the need for regular calibration and insufficient lifespan, thus limiting their widespread adoption. In engineering operation and maintenance inspections and long-term monitoring, the vibration method is primarily used. The core of the vibration method is to employ non-destructive vibration measurement methods, including accelerometers and microwave radar, to measure the transverse vibration response of the cable. Then, combined with a mathematical model describing the relationship between the cable vibration characteristics and its force, the cable force is analyzed and identified. The vibration method is widely used due to its economic efficiency and ease of operation.

[0004] Vibration methods for measuring cable force can be divided into two categories: frequency methods and frequency-based methods. Frequency-based methods aim to obtain the frequency by observing the cable's vibration. This method has no strict requirements on the direction and absolute magnitude of the measured vibration and can employ contact accelerometers, non-contact displacement gauges, microwave radar, laser vibrometers, and photogrammetry, without requiring precise location of the measurement point. Because this method only obtains the cable frequency information, the cable model used is relatively idealized. It typically assumes that the cable's mass and length are known (design cable length) and that there are no lateral constraints (or that constraint information is known). These assumptions are suitable for long cables and cables without built-in / external dampers, resulting in high cable force identification accuracy that meets engineering requirements. However, for shorter cables and cables with built-in / external dampers at the ends, the error in cable force identification can exceed 20%, failing to meet engineering needs.

[0005] For cables with short lengths, complex boundary conditions, and those equipped with built-in / external dampers at the ends, existing research has proposed identification methods combining modal measurements. For example, the equivalent hinged beam method treats a free segment of the cable without lateral constraints as an equivalent tension beam hinged at both ends, but the beam's length is unknown. The measurement requires multiple sensors to measure the vibration response at multiple points on the cable segment. Modal analysis is used to obtain the mode shapes at the measurement points, and then the mode shape function of the equivalent hinged beam is fitted to obtain its length. Further, the tension force on the beam, i.e., the internal force of the target cable, is identified by combining the frequency. This method offers excellent accuracy and wide applicability, but its drawback lies in the need to install multiple sensors to identify the mode shapes. Currently, accelerometers are mainly used, which presents difficulties in installing accelerometers at multiple locations and at high altitudes, thus limiting its practical application. Non-contact methods for measuring vibration modes have been a recent research focus. For example, machine vision is used for cable vibration mode measurement. However, this method currently requires obvious feature points on the cable (e.g., light strips), and a universal method has not yet been developed. Furthermore, visual measurements require large data storage and complex processing, which also presents difficulties. Another approach is microwave radar for cable vibration mode measurement. However, the target measurement points for microwave radar are not clearly defined, and estimations based on geometric relationships introduce errors. Additionally, its sampling frequency is currently limited to around 200Hz, which cannot fully cover the high-frequency vibrations of short cables, and its measurement accuracy is only around 0.01mm, which is insufficient for the high-frequency vibrations of short cables. Laser vibrometers can achieve long-distance vibration measurement, with measurement accuracy reaching the picometer level and sampling frequencies exceeding MHz. They typically use visible light to directly mark measurement points. However, currently, their application in cable vibration measurement is limited to single-point vibration and frequency measurement, lacking integrated equipment and methods for acquiring cable vibration modes.

[0006] In summary, efficient, widely applicable, and easy-to-operate cable internal force identification technology remains a key technical challenge that urgently needs to be overcome in the field of structural inspection and monitoring. Although laser vibrometers have applications in cable frequency measurement, they have not yet been used for remote and non-contact cable vibration mode identification or mode-based cable force identification. How to use laser vibrometers to achieve long-distance, non-contact, accurate, and efficient measurement of cable internal forces remains an unsolved problem in this field. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a long-distance non-contact cable force identification device and its cable force identification method based on laser array vibration measurement.

[0008] The non-contact cable force identification device and its cable force identification method provided by this invention comprehensively utilize technologies and methods such as long-distance laser vibration measurement, laser ranging, spatial geometric calculation, and high-precision cable force identification using vibration modes to achieve completely non-contact and long-distance measurement of cable force. It can be applied to long cables, short cables, and long and short cables with complex boundary conditions and constraint devices such as built-in and external dampers, greatly improving the accuracy, efficiency and operability of cable force identification.

[0009] The objective of this invention can be achieved through the following technical solutions: The first objective of this invention is to provide a long-distance non-contact cable force identification device for laser array vibration measurement, comprising a support assembly and a measuring assembly disposed above the support assembly; The measurement components include a substrate, a laser vibrometer for observing the vibration response of the target cable, a laser rangefinder for measuring the distance between the substrate and / or the laser vibrometer and the target cable, and an inclination meter for measuring the angle between the vibration beam of the laser vibrometer and the horizontal plane, measuring the angle between the distance beam of the laser rangefinder and the horizontal plane, and / or measuring the inclination angle of the substrate and the target cable along the horizontal plane. The substrate is used to fix the laser vibrometer, the laser rangefinder, and the tilt meter; When using this device to measure the target cable, the laser vibrometer projects a vibration measuring beam onto the target cable to obtain the measuring point, and observes the vibration response of the target cable at the measuring point; the laser rangefinder projects a ranging beam to measure the distance, and the tilt meter measures the angle between the vibration measuring beam and the horizontal plane, as well as the angle between the ranging beam and the horizontal plane, to calculate the angle between the vibration measuring beam and the target cable and the distance between each measuring point on the target cable, which is then used to identify the mode shape and cable force of the target cable.

[0010] In one embodiment of the present invention, one or more laser rangefinders are provided; The laser rangefinder has a measurement accuracy better than 1 cm.

[0011] In one embodiment of the present invention, the laser rangefinder is movably connected to the substrate, allowing rotation along the plane of the substrate (facilitating adjustment of the position of the measuring point of the laser rangefinder's measuring beam on the target cable when the substrate is fixed) and allowing disassembly and installation.

[0012] In this invention, the laser rangefinder can be detachably mounted on the substrate, allowing it to be removed during use to measure the length of each vibration beam separately, or it can be integrated with a laser vibrometer to directly measure the length of the vibration beam.

[0013] In one embodiment of the present invention, two or more laser vibrometers are provided; The vibration measurement beams of two or more laser vibration meters are located in the same plane; The laser vibrometer has a measurement accuracy better than 0.1 mm and a measurement range greater than 1 m.

[0014] In one embodiment of the present invention, the laser vibrometer is movably connected to the substrate, allowing it to rotate along the plane of the substrate (to facilitate adjusting the position of the measuring beam of the laser vibrometer on the measuring point on the target cable when the substrate is fixed).

[0015] In one embodiment of the present invention, one or more tilt measuring instruments are provided; The tilt measuring instrument has a measurement accuracy better than 0.1 degrees.

[0016] In one embodiment of the invention, the tilt measuring instrument is movably connected to the base plate, allowing for disassembly and installation.

[0017] In this invention, the tilt measuring instrument can be detachably mounted on the substrate, and can be removed during use to measure the angle between the vibration measuring beam and the horizontal plane, the angle between the distance measuring beam and the horizontal plane, and the tilt angle of the substrate and the target cable along the horizontal plane. At the same time, it can also be integrated with a laser vibrometer and a laser distance measuring instrument to directly measure the angle between the vibration measuring beam and the horizontal plane and the angle between the distance measuring beam and the horizontal plane.

[0018] In one embodiment of the present invention, the substrate is fixed above the support assembly by a rotation and lifting assembly, the rotation and lifting assembly being used to adjust the vibration measuring beam of the laser vibrometer, the distance measuring beam of the laser rangefinder, and the target cable to be coplanar.

[0019] The second objective of this invention is to provide a non-contact cable force identification method, using the aforementioned laser array vibration measurement long-distance non-contact cable force identification device. The non-contact cable force identification method includes the following steps: (S1) Adjust the rotating lifting assembly to make the substrate and the target cable coplanar; (S2) Adjust the position of the measuring point on the target cable of each laser vibrometer beam to meet the target requirements and then fix the laser vibrometer. (S3) Measure the necessary distance using a laser rangefinder and the necessary tilt angle using an inclination meter, and calculate the distance between each measuring point on the target cable and the angle between the vibration measuring beam and the target cable; (S4) Under environmental excitation or by striking the target cable with an excitation hammer, record the vibration response (including velocity, acceleration, etc.) at each measuring point on the target cable using a laser vibrometer, and repeat the measurement at least twice; (S5) Divide the vibration response of each measuring point obtained by the laser vibration meter by the sine value of the angle between the corresponding vibration beam and the target cable at each measuring point to obtain the vibration response of the cable perpendicular to the cable axis at each measuring point; (S6) Based on the vibration response of the cable perpendicular to the cable axis at each measuring point obtained in step (S5), perform modal analysis to obtain the mode shape value and cable frequency of the target cable at each measuring point, and obtain the frequency and mode shape of at least two vibrations; (S7) Combine the spacing between the measuring points on the target cable obtained in step (S3), and the mode shape and cable frequency obtained in (S6), calculate the cable force value.

[0020] In one embodiment of the present invention, when measuring the same target cable, it is allowed to fix the measuring beam of one laser vibrometer at the measuring point on the target cable, and adjust other laser vibrometers to repeat the measurement at the corresponding measuring point on the target cable. Then, the vibration mode values ​​of more than the number of laser vibrometers on the target cable are combined with the measuring point corresponding to the fixed laser vibrometer as the reference point to improve the identification accuracy of cable force.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The laser array vibration measurement long-distance non-contact cable force identification device provided by the present invention can measure a distance of more than 100m. Compared with the traditional vibration mode measurement method using accelerometers, it completely avoids the work of installing accelerometers at multiple locations and high places on the cable using a climbing vehicle, which greatly improves the identification efficiency and safety of cable force. (2) The laser array vibration measurement long-distance non-contact cable force identification device provided by the present invention has simpler data storage and processing methods and stronger operability compared with the vibration mode measurement method using machine vision. In addition, the machine vision measures the vibration response in the direction perpendicular to the shooting direction, and the actual application has high requirements for the position of its measurement equipment. (3) The laser array vibration measurement long-distance non-contact cable force identification device provided by the present invention can achieve higher precision measurement point positioning, higher sampling frequency and measurement accuracy compared with microwave radar measurement technology; (4) The laser array vibration measurement long-distance non-contact cable force identification device and method provided by the present invention can use a small number of laser vibration meters to measure the vibration mode at multiple positions on the cable through a fixed reference point, which can improve the measurement accuracy while ensuring economy and efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a long-distance non-contact cable force identification device for laser array vibration measurement provided by the present invention; Figure 2 A partial enlarged view of a long-distance non-contact cable force identification device for laser array vibration measurement provided by the present invention; Figure 3 For along Figure 2 Sectional view of AA; Figure 4This is a diagram illustrating the method for determining the spatial position of the vibration measurement beam and the cable in Example 3; Figure 5 This is a diagram illustrating the method for determining the spatial position of the vibration measurement beam and the cable in Example 4. Figure 6 The diagram and photographs show the arrangement of the three laser vibrometers measuring the test cable in Example 5. Figure 7 The data are displacement data recorded in the three laser vibration meter tests in Example 5, and the converted cable vibration displacement diagram is shown. Figure 8 The graph shows the cable vibration modes and the fitting results of the mode shape function obtained by measuring the three laser vibrometers in Example 5. Figure 9 The graph shows the cable vibration modes and the fitting results of the mode shape function obtained by measuring the three laser vibrometers in Example 6. Figure 10 The image shows the mode shape and mode shape function fitting results combined using the second measuring point as the reference point, based on the mode shape test results in Examples 5 and 6. The following are the labels in the diagram: 1. Laser vibration meter; 2. Laser rangefinder; 3. Inclinometer; 4. Base plate; 5. Rotation and lifting assembly; 6. Support assembly; 7. Target cable; 8. Vibration beam; 9. Rangefinder beam; 10. Measuring point. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0027] In the following embodiments, unless otherwise specified, the structures or components used are conventional structures or components in the art, as long as they can achieve the corresponding functions.

[0028] Example 1 This embodiment provides a long-distance, non-contact cable force identification device based on laser array vibration measurement, such as... Figures 1-3 As shown, the system includes a support assembly 6 and a measuring assembly disposed above the support assembly 6. The measuring assembly includes a base plate 4, a laser vibrometer 1 for observing the vibration response of the target cable 7, a laser rangefinder 2 for measuring the distance between the base plate 4 and / or the laser vibrometer 1 and the target cable 7, and an inclination measuring instrument 3 for measuring the angle between the vibration beam 8 of the laser vibrometer 1 and the horizontal plane, the angle between the distance beam 9 of the laser rangefinder 2 and the horizontal plane, and / or the angle between the base plate 4 and the target cable 7 and the horizontal plane. The base plate 4 is used to fix the laser vibrometer 1. The device includes a laser rangefinder 2 and an inclination meter 3. When measuring the target cable 7, the laser vibrometer 1 projects a vibration measuring beam 8 onto the target cable 7 to obtain a measuring point 10, and observes the vibration response of the target cable 7 at the measuring point 10. The laser rangefinder 2 projects a ranging beam 9 to measure the distance, and the inclination meter 3 measures the angle between the vibration measuring beam 8 and the horizontal plane, as well as the angle between the ranging beam 9 and the horizontal plane. The angle between the vibration measuring beam 8 and the target cable 9, as well as the distance between each measuring point 10 on the target cable 7, are calculated, and then used to identify the vibration mode and cable force of the target cable 7.

[0029] Furthermore, one or more laser rangefinders 2 are provided, and the measurement accuracy of the laser rangefinders 2 is better than 1 cm; the laser rangefinders 2 are movably connected to the base plate 4, allowing rotation along the plane of the base plate 4 (to facilitate adjusting the position of the measuring beam 9 of the laser rangefinder 2 aligned with the measuring point 10 on the target cable 7 when the base plate 4 is fixed) and allowing disassembly and installation; the laser rangefinders 2 can be detachably installed on the base plate 4, allowing them to be removed during use to measure the length of each vibration measuring beam 8 separately, and also allowing them to be integrated with the laser vibration meter 1 to directly measure the length of the vibration measuring beam 8.

[0030] Furthermore, the laser vibrometer 1 is provided in two or more forms, and the vibration measuring beams 8 of the two or more laser vibrometers 1 are located on the same plane; the measurement accuracy of the laser vibrometer 1 is better than 0.1 mm, and the measurement range is greater than 1 m; the laser vibrometer 1 is movably connected to the substrate 4, allowing it to rotate along the plane of the substrate 4 (to facilitate adjusting the position of the vibration measuring beam 8 of the laser vibrometer 1 on the measuring point 10 on the target cable 7 when the substrate 4 is fixed).

[0031] Furthermore, one or more tilt measuring instruments 3 are provided; the measurement accuracy of the tilt measuring instruments 3 is better than 0.1 degrees; the tilt measuring instruments 3 are movably connected to the base plate 4 and can be disassembled and installed; the tilt measuring instruments 3 can be detachably installed on the base plate 4, and can be removed during use to measure the angle between the vibration measuring beam 8 and the horizontal plane, the angle between the distance measuring beam 9 and the horizontal plane, and the angle between the base plate 4 and the target cable 7 and the horizontal plane; at the same time, it can also be integrated with the laser vibration meter 1 and the laser distance measuring meter 2 to directly measure the angle between the vibration measuring beam 8 and the horizontal plane, and the angle between the distance measuring beam 9 and the horizontal plane.

[0032] Furthermore, the substrate 4 is fixed above the support assembly 6 (e.g., a triangular support frame) by a rotating lifting assembly 5 (e.g., a universal adjustment bracket). The rotating lifting assembly 5 is used to adjust the vibration measuring beam 8 of the laser vibration meter 1 and the distance measuring beam 9 of the laser rangefinder 2 to be coplanar with the target cable 7.

[0033] Example 2 This embodiment provides a non-contact cable force identification method, using the long-distance non-contact cable force identification device with laser array vibration measurement provided in Embodiment 1. The non-contact cable force identification method includes the following steps: (S1) Adjust the rotating lifting assembly to make the substrate and the target cable coplanar; (S2) Adjust the position of the measuring point on the target cable of each laser vibrometer beam to meet the target requirements and then fix the laser vibrometer. (S3) Measure the necessary distance using a laser rangefinder and the necessary tilt angle using an inclination meter, and calculate the distance between each measuring point on the target cable and the angle between the vibration measuring beam and the target cable; (S4) Under environmental excitation or by striking the target cable with an excitation hammer, record the vibration response (including velocity, acceleration, etc.) at each measuring point on the target cable using a laser vibrometer, and repeat the measurement at least twice; (S5) Divide the vibration response of each measuring point obtained by the laser vibration meter by the sine value of the angle between the corresponding vibration beam and the target cable at each measuring point to obtain the vibration response of the cable perpendicular to the cable axis at each measuring point; (S6) Based on the vibration response of the cable perpendicular to the cable axis at each measuring point obtained in step (S5), perform modal analysis to obtain the mode shape value and cable frequency of the target cable at each measuring point, and obtain the frequency and mode shape of at least two vibrations; (S7) Combine the spacing between the measuring points on the target cable obtained in step (S3), and the mode shape and cable frequency obtained in (S6), calculate the cable force value.

[0034] In one embodiment of the present invention, when measuring the same target cable, it is allowed to fix the measuring beam of one laser vibrometer at the measuring point on the target cable, and adjust other laser vibrometers to repeat the measurement at the corresponding measuring point on the target cable. Then, the vibration mode values ​​of more than the number of laser vibrometers on the target cable are combined with the measuring point corresponding to the fixed laser vibrometer as the reference point to improve the identification accuracy of cable force.

[0035] Example 3 This embodiment provides an application of a long-distance, non-contact cable force identification device based on laser array vibration measurement, such as... Figure 4 As shown, taking the calculation of the geometric relationship between two vibration measurement beams and the target cable as an example, the angle between each vibration measurement beam and the target cable, as well as the distance between each measurement point, are measured and calculated using the following method: In the various distance and tilt angle measurements, a laser rangefinder is used to measure a point on the first laser vibration meter 1-1 that is collinear with the first vibration measurement beam 8-1. The distance from the first measuring point 10-1 is denoted as . The tilt angle of the first vibration measuring beam 8-1 was measured using a tilt meter and recorded as follows: That is, the angle between the first vibration measuring beam 8-1 and the horizontal plane; similarly, a point on the second laser vibration meter 1-2 that is collinear with the second vibration measuring beam 8-2 is measured using a laser rangefinder. The distance from the second measuring point 10-2 is denoted as The tilt angle of the second vibration beam 8-2 was measured using a tilt meter and recorded as follows: . on substrate and The length and angle of inclination of the line connecting the two points are known or measured using a laser rangefinder and an inclination meter, and are respectively denoted as . and (It can be directly measured during application).

[0036] Next, the calculations will be performed as follows. The first vibration measurement beam 8-1 and... The angle between the lines is : The second vibration measuring beam 8-2 and The angle between the lines is : The extensions of the first vibration measurement beam 8-1 and the second vibration measurement beam 8-2 intersect at point [missing information]. The triangle formed interior angle of : = The sides can be determined using trigonometric relationships. Length is: Similarly, the edges are obtained. Length is: At the same time, such as Figure 4 As shown, the first vibration measurement beam 8-1 and the second vibration measurement beam 8-2 form a triangle with the target cable, with the three vertices being points 1, 2, and 3 respectively. Using the law of cosines, the distance between the first measuring point 10-1 and the second measuring point 10-2 can be obtained. for: The cosine value of the angle between the corresponding first vibration measurement beam 8-1 and the target cable for: The cosine of the angle between the corresponding second vibration measurement beam 8-2 and the target cable for: After obtaining the cosine values ​​of the two angles mentioned above, their angle values ​​can be calculated (respectively...). and ) and the sine of the angle ( and ).

[0037] It should be noted that when there are three or more laser vibrometers, two adjacent ones can be used as a pair, and the angle between all the vibration beams and the target cable and the distance between the measuring points can be obtained according to the calculation method provided above in this embodiment.

[0038] In addition, when the vibration direction of the target cable is not in the vertical plane during measurement, the substrate is adjusted to be coplanar with the target cable and its vibration direction to be measured, and the tilt angle of the plane is measured using an inclination meter; then, all tilt angles are converted to the angle between the plane and the horizontal line using the above calculation method and then calculated.

[0039] Example 4 This embodiment provides an application of a long-distance, non-contact cable force identification device based on laser array vibration measurement, such as... Figure 5As shown, taking the calculation of the geometric relationship between two vibration measurement beams and the cable as an example, the angles between each vibration measurement beam, the distance measurement beam and the target cable, as well as the distance between each measurement point, are measured and calculated as follows: When measuring distance, the intersection of the first vibration measuring beam 8-1 and the target cable is recorded as the first measuring point 10-1, and the intersection of the second vibration measuring beam 8-2 and the target cable is recorded as the second measuring point 10-2. The laser rangefinder is fixed to the base at this point. First, align the first ranging beam 9-1 with the first measuring point 10-1, and measure the length of the first ranging beam 9-1 as follows: Inclination angle is Then rotate the laser rangefinder so that the second ranging beam 9-2 is aligned with the second measuring point 10-2, and measure the length of the second ranging beam. Inclination angle is Simultaneously, the tilt angle of the first vibration measuring beam 8-1 is measured using an inclination meter and recorded as follows: The tilt angle of the second vibration beam 8-2 is denoted as... .

[0040] point The distance between the two measuring points, forming a triangle, can be obtained using the law of cosines. : The angle between the corresponding first ranging beam 9-1 and the target cable is The angle between the second ranging beam 9-2 and the target cable is... Calculate using the following formula: Using the tilt angle of the first ranging beam 9-1 The angle between the first ranging beam 9-1 and the target cable The inclination angle of the target cable can be obtained as follows: This allows us to obtain the angle between the target cable and the first vibration measurement beam 8-1. : This allows us to obtain the angle between the target cable and the second vibration measurement beam 8-2. : The above two angles are obtained ( and Then its sine value can be calculated.

[0041] It should be noted that when there are three or more laser vibration measurement modules, two adjacent modules can be paired up, and the angles between all vibration measurement beams and the target cable and the distances between measurement points can be obtained according to the calculation method provided above in this embodiment.

[0042] In addition, when the vibration direction of the target cable is not in the vertical plane during measurement, the substrate is adjusted to be coplanar with the target cable and its vibration direction to be measured, and the tilt angle of the plane is measured using an inclination meter; then, all tilt angles are converted to the angle between the plane and the horizontal line using the above calculation method and then calculated.

[0043] Example 5 This embodiment describes the application of a long-distance, non-contact cable force identification device based on laser array vibration measurement, such as... Figure 6 As shown, a horizontal high-stretch cable (hereinafter referred to as "cable") was tensioned using a tensioning platform for testing. Its length between the anchor plates at both ends was 8m, and the cable's mass per unit length was 5.93kg / m. Both ends had a thickened anchoring section, with one end connected in series with a hydraulic tensioning device to adjust the cable force, and the other end connected in series with a pressure sensor to measure the cable force. An intermediate support was added near the non-tensioned end to simulate the built-in damper installed on an actual cable. Three laser vibrometers were used to measure the vibration at three points on the cable, achieving a displacement resolution of 0.01nm and a sampling frequency of up to 5MHz (16000Hz in this embodiment). One laser rangefinder was used to adjust and measure the length of the three measuring beams three times, and one tilt meter was used to measure the tilt angle of each measuring beam.

[0044] This embodiment obtains the angles between the first vibration measuring beam 8-1, the second vibration measuring beam 8-2, and the third vibration measuring beam 8-3 and the cable according to the method provided in embodiment 4 (respectively...). The distance between the first measuring point 10-1 and the second measuring point 10-2 And the distance between the second measuring point 10-2 and the third measuring point 10-3 .

[0045] The measured distances include the lengths of the first ranging beam 9-1, the second ranging beam 9-2, and the third ranging beam 9-3; the measured tilt angles include the tilt angles of the first ranging beam 9-1, the second ranging beam 9-2, the third ranging beam 9-3, the first vibration measuring beam 8-1, the second vibration measuring beam 8-2, and the third vibration measuring beam 8-3; the distance between the first measuring point 10-1 and the second measuring point 10-2 is obtained using the lengths of the first ranging beam 9-1 and the second ranging beam 9-2 and their included angle. =1.082m, the angles between the first vibration measuring beam 8-1 and the second vibration measuring beam 8-2 and the cable are respectively and =29.064°; using the lengths of the second ranging beam 9-2 and the third vibration measuring beam 9-3 and their included angle, the distance between the second measuring point 10-2 and the third measuring point 10-3 is obtained. =2.744m, the angle between the third vibration measurement beam 8-3 and the cable is 16.499°.

[0046] For verification, the distance between adjacent measuring points was directly measured using a tape measure, and the result was 2.765m. ) and 1.058m ( The result is highly consistent with the calculation method of this embodiment, and the absolute value of the error is less than 2.5%.

[0047] The original data signal was recorded after striking the cable five times with an excitation hammer. The transformed cable displacement signal was obtained by dividing the original displacement signal by the sine of the angle between the vibration beam and the cable. Figure 7 As shown.

[0048] use Figure 7 The converted cable vibration displacement signal shown is filtered out by a high-pass filter to remove drift components. Then, the Natural Excitation Technique and Feature System Implementation Algorithm (ERA) are used to identify the mode shapes of the cable at three measuring points. Based on the actual distances between the measuring points, the signal is plotted on... Figure 8 In the diagram, solid dots represent measured mode shapes. A total of four mode shapes were identified, including frequencies (…). f n ,in, n The Hz frequencies (in order) are 16.360Hz, 32.809Hz, 49.615Hz and 67.191Hz respectively.

[0049] An equivalent two-end hinged tension beam model is adopted, where the middle section of the cable is equivalent to a two-end hinged tension beam, but the beam length is unknown. The frequencies of the two-end hinged tension beam are consistent with the original cable frequencies, and the mode shapes are approximately the same as the cable even when not near the cable anchorage point or intermediate support position. Note that in this example, the three measuring points are not close to the cable anchorage point or support point; therefore, the mode shapes of the two-end hinged tension beam can be fitted using the three measuring points. It is known that the mode shapes are sinusoidal functions, and their... n The mode shape can be represented by the following expression: in, Indicates at the measuring point s The measured value of the vibration mode at that location, , and The coefficients to be identified, For the equivalent length of the tension beam with hinges at both ends, This indicates the number of sensors or measuring points. ; Here are the coordinates of the measuring points. Their absolute values ​​are not necessary; the key is their relative positions. We take the coordinates of the first measuring point (10-1), the second measuring point (10-2), and the third measuring point (10-3) as follows: , m、 m. Substituting the identified mode shape values ​​of the fourth mode into the above formula, the lengths of the tension beams with hinged ends are found to be 7.008m, 6.951m, 6.907m, and 6.940m, respectively. Then, based on the frequency and cable force relationship of the tension beams with hinged ends, i.e. To identify the cable force, the above equation has two unknowns: cable force. and bending stiffness .

[0050] Therefore, at least two modal frequencies and the equivalent beam model length are required for identification. For modal information with more than two orders, the least squares method is used to identify the parameters. In this embodiment, based on the known mass per unit length of the cable and the fourth modal information, the cable force is obtained as 307.3 kN, which is in very good agreement with the 306.6 kN measured by the pressure sensor, with an error of 0.23%.

[0051] Example 6 This embodiment describes the application of a long-distance, non-contact cable force identification device using laser array vibration measurement. The cable arrangement and the device are the same as in Embodiment 5. In this embodiment, the second vibration measurement beam 8-2 and the second measurement point 10-2 are fixed. By adjusting the first laser vibration meter 1 and the third laser vibration meter 3, the first measurement point 10-1 and the third measurement point 10-3 are adjusted, and the measurement is repeated. Then, the vibration mode measurement result of the second measurement point 10-2 is used as a reference to merge the vibration modes of the two measurements, resulting in vibration mode values ​​at five locations on the cable (this embodiment aims to demonstrate how to use the provided device to identify the vibration mode values ​​of more than the number of laser vibration meters).

[0052] The distances between the adjusted first measuring point 10-1, the third measuring point 10-3, and measuring point 10-2 were determined using the methods described in Examples 4 and 5. =1.317m and =3.284m.

[0053] The measured vibration modes are as follows Figure 9 As shown, the solid squares mark the tested mode shape values, and the solid lines represent the fitted mode shape function, corresponding to the fourth-order frequencies ( ). f n ,in, nThe Hz frequencies (orders) are 16.305Hz, 32.809Hz, 49.640Hz, and 67.090Hz, respectively. Similar to Example 5, using these three measurement points, the equivalent lengths of the tension beams with hinged ends can be obtained as 6.932m, 7.037m, 6.923m, and 6.982m, respectively. The identified cable force is 306.3kN, and the absolute value of the error between this and the sensor-measured cable force of 306.6kN is less than 0.1%.

[0054] Using the mode shape value measured at the second measuring point 10-2 as a reference, the mode shape values ​​of the two measurements are scaled up to make the mode shape value at the second measuring point 10-2 equal, thus obtaining the mode shape values ​​at a total of 5 points, as follows. Figure 10 As shown in the figure, the sinusoidal functions fitted using these four vibration modes are also displayed. The corresponding lengths of the tension beam with hinged ends are 6.959m, 6.930m, 6.919m, and 6.968m, respectively. It can be seen that the equivalent beam lengths identified are closer and more stable in each mode. Simultaneously, the frequencies from the two measurements are averaged to obtain the first four frequencies (…). f n ,in, n The frequencies (orders) are 16.362Hz, 32.809Hz, 49.618Hz, and 67.141Hz, respectively, corresponding to a cable force of 303.4kN. The cable force measured by the pressure sensor remains 306.6kN. Since the accuracy of the three-point identification method is already high enough, there is no significant improvement in the identification accuracy of the cable force.

[0055] In summary, the long-distance non-contact cable force identification device using laser array vibration measurement provided by this invention operates by having at least two laser vibrometers emit vibration beams that are aligned with the target cable in the same plane. Measurement points are formed at different locations on the target cable to obtain the vibration response at corresponding positions. Simultaneously, a laser rangefinder and an inclination meter are used to measure the relative spatial positions of the substrate, the vibration beams, and the target cable, calculating the angle between the vibration beams and the cable axis, as well as the spacing between the measurement points on the cable. The angle between the vibration beams and the cable is used to convert the cable vibration response obtained by the laser vibrometers into a true vibration response perpendicular to the cable axis. Modal analysis is then performed to obtain the mode shape values ​​at the measurement points. Combined with the obtained measurement point spacing, high-precision mode shape and frequency measurements are used in conjunction with the cable vibration model to identify the cable force. Furthermore, by fixing one vibration beam as a reference measurement point and adjusting the positions of the remaining beams for multiple measurements, the mode shape information obtained under different measurement conditions is stitched together using the reference measurement point as a benchmark, thereby constructing a more refined cable vibration mode shape and further improving the accuracy of cable force identification. In summary, the device and detection method provided by this invention enable long-distance, non-contact, multi-point cable vibration mode identification and cable force estimation, effectively improving the accuracy and on-site operability of cable force identification under the influence of short cables and auxiliary components, and has good engineering adaptability and broad application prospects.

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A long-distance non-contact cable force identification device based on laser array vibration measurement, characterized in that, Includes a support assembly and a measuring assembly positioned above the support assembly; The measurement components include a substrate, a laser vibrometer for observing the vibration response of the target cable, a laser rangefinder for measuring the distance between the substrate and / or the laser vibrometer and the target cable, and an inclination meter for measuring the angle between the vibration beam of the laser vibrometer and the horizontal plane, measuring the angle between the distance beam of the laser rangefinder and the horizontal plane, and / or measuring the inclination angle of the substrate and the target cable along the horizontal plane. The substrate is used to fix the laser vibrometer, the laser rangefinder, and the tilt meter; When using this device to measure the target cable, the laser vibrometer projects a vibration measuring beam onto the target cable to obtain the measuring point, and observes the vibration response of the target cable at the measuring point; the laser rangefinder projects a ranging beam to measure the distance, and the tilt meter measures the angle between the vibration measuring beam and the horizontal plane, as well as the angle between the ranging beam and the horizontal plane, to calculate the angle between the vibration measuring beam and the target cable and the distance between each measuring point on the target cable, which is then used to identify the mode shape and cable force of the target cable.

2. The long-distance non-contact cable force identification device for laser array vibration measurement according to claim 1, characterized in that, The laser rangefinder is provided in one or more locations; The laser rangefinder has a measurement accuracy better than 1 cm.

3. The long-distance non-contact cable force identification device for laser array vibration measurement according to claim 2, characterized in that, The laser rangefinder is movably connected to the substrate, allowing it to rotate along the substrate plane and to be disassembled and installed.

4. The long-distance non-contact cable force identification device for laser array vibration measurement according to claim 1, characterized in that, The laser vibration meter is provided in two or more units; The vibration measurement beams of two or more laser vibration meters are located in the same plane; The laser vibrometer has a measurement accuracy better than 0.1 mm and a measurement range greater than 1 m.

5. A long-distance non-contact cable force identification device for laser array vibration measurement according to claim 4, characterized in that, The laser vibrometer is movably connected to the substrate, allowing it to rotate along the plane of the substrate.

6. The long-distance non-contact cable force identification device for laser array vibration measurement according to claim 1, characterized in that, The tilt measuring instrument is provided in one or more locations; The tilt measuring instrument has a measurement accuracy better than 0.1 degrees.

7. A long-distance non-contact cable force identification device for laser array vibration measurement according to claim 6, characterized in that, The tilt measuring instrument is movably connected to the base plate, allowing for disassembly and installation.

8. The long-distance non-contact cable force identification device for laser array vibration measurement according to claim 1, characterized in that, The base plate is fixed above the support assembly by a rotating and lifting assembly, which is used to adjust the vibration beam of the laser vibrometer, the distance measuring beam of the laser rangefinder, and the target cable to be coplanar.

9. A non-contact cable force identification method, using the long-distance non-contact cable force identification device based on laser array vibration measurement as described in any one of claims 1 to 8, characterized in that, The non-contact cable force identification method includes the following steps: (S1) Adjust the rotating lifting assembly to make the substrate and the target cable coplanar; (S2) Adjust the position of the measuring point on the target cable of each laser vibrometer beam to meet the target requirements and then fix the laser vibrometer. (S3) Measure the necessary distance using a laser rangefinder and the necessary tilt angle using an inclination meter, and calculate the distance between each measuring point on the target cable and the angle between the vibration measuring beam and the target cable; (S4) Under environmental excitation or by striking the target cable with an excitation hammer, record the vibration response at each measuring point on the target cable using a laser vibrometer, and repeat the measurement at least twice. (S5) Divide the vibration response of each measuring point obtained by the laser vibration meter by the sine value of the angle between the corresponding vibration beam and the target cable at each measuring point to obtain the vibration response of the cable perpendicular to the cable axis at each measuring point; (S6) Based on the vibration response of the cable perpendicular to the cable axis at each measuring point obtained in step (S5), perform modal analysis to obtain the mode shape value and cable frequency of the target cable at each measuring point, and obtain the frequency and mode shape of at least two vibrations; (S7) Combine the spacing between the measuring points on the target cable obtained in step (S3), and the mode shape and cable frequency obtained in (S6), calculate the cable force value.

10. The non-contact cable force identification method according to claim 9, characterized in that, When measuring the same target cable, it is allowed to fix the measuring beam of one laser vibrometer at the measuring point on the target cable, and adjust other laser vibrometers to repeat the measurement at the corresponding measuring points on the target cable. Then, the vibration mode values ​​of more than the number of laser vibrometers on the target cable are obtained by merging the measuring points corresponding to the fixed laser vibrometers as reference points.

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