Vibration table vibration level calibration test system and method based on distributed optical fibers

Abstract

The invention discloses a distributed optical fiber-based vibration table vibration level calibration test system and method. The system comprises a clamp, a test structural member, a vibration table and a data acquisition device. The test method comprises the steps of designing a test structural member, installing the test device, carrying out a vibration test on the vibration table, processing and analyzing collected vibration signals, simulating a test process by adopting simulation software, and verifying the rationality of the test. The device can accurately monitor the fine change of rail transit vibration, is good in simulation effect and economical efficiency, is high in test accuracy, can achieve the complete coverage and stable monitoring, and reduces the maintenance and replacement cost of equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration monitoring, and particularly relates to a vibration table vibration level calibration test system and method based on distributed optical fiber. Background Art

[0002] With the acceleration of the urbanization process and the rapid development of rail transit, the vibration induced along the track and the environmental noise problems during train operation have seriously affected the surrounding residents. At present, the research on vibration isolation and shock absorption measures for rail transit has been relatively complete, and the focus of attention has gradually shifted to the smoothness of track operation. Therefore, the intelligent monitoring and evaluation system for rail transit vibration has become a research hotspot. In the context of "intelligent, high-precision, and flexible", the traditional vibration level monitoring methods can no longer meet the requirements of rapid real-time monitoring, and there are limitations in terms of accuracy, sensitivity, real-time performance, monitoring range, and connection and data sharing with other devices.

[0003] Distributed optical fiber vibration monitoring technology has the advantages of high-precision monitoring, comprehensive coverage, strong anti-interference ability, long service life, and stable performance. However, it is difficult to install and wire in the rail transit system, the working environment may affect its performance and stability, and its ability to capture tiny vibration signals is unknown. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the technical solution adopted by the present invention to solve its technical problems is: a vibration table vibration level calibration test system based on distributed optical fiber, including:

[0005] A fixture for fixing the test structural member;

[0006] The test structural member is composed of a deformation structure and a distributed optical fiber. The deformation structure is used to generate deformation under the action of the vibration table, and the distributed optical fiber is used to sense the vibration of the deformation structure;

[0007] A vibration table for providing vibration excitation;

[0008] A data acquisition device for acquiring the vibration signals sensed by the distributed optical fiber.

[0009] Preferably, the fixture includes a bottom plate, a clamping plate, and a support rod. The clamping plate is connected to the bottom plate through the support rod, and screw holes are provided on the bottom plate and the clamping plate for fixing the test structural member with screws.

[0010] Preferably, the deformation structure is a rectangular plate made of stainless steel.

[0011] Preferably, the distributed optical fiber is arranged on the deformation structure. The length of the sensing section of the optical fiber on each deformation structure is not less than 1 section, each section is 5 m, and the optical fibers between multiple deformation structures are connected in series in a longitudinal arrangement.

[0012] Preferably, the data acquisition device is a grating type Φ-OTDR.

[0013] A vibration level calibration test method for a shaking table based on distributed optical fiber includes the following steps:

[0014] Step 1: Design test structural members, including a deformation structure and a fixture;

[0015] Step 2: Install the test device, arrange the distributed optical fiber on the deformation structure, fix the deformation structure on the shaking table through the fixture, and connect the data acquisition device;

[0016] Step 3: Conduct a shaking table vibration test, set the acceleration amplitude and frequency of the shaking table, and collect the vibration signals sensed by the distributed optical fiber;

[0017] Step 4: Process and analyze the collected vibration signals, obtain the vibration acceleration, and convert it into vibration level calculation;

[0018] Step 5: Use simulation software to simulate the test process, compare the simulation results with the test results, and verify the rationality of the test.

[0019] Preferably, in the step of designing the test structural members, according to the vibration mode of the structural members, the deformation structure is designed as a rectangular plate with appropriate thickness, and the material is stainless steel; according to the form of the shaking table surface of the structure, according to the structural installation form and the optical fiber arrangement form, the fixture is designed in a specific form.

[0020] Preferably, in the step of conducting the shaking table vibration test, adjust the parameters of the data acquisition device to obtain stable and clear signals.

[0021] Preferably, in the step of processing and analyzing the collected vibration signals, use IQ demodulation technology to obtain the vibration acceleration, obtain the real-time acceleration a through the way of second derivative, and then calculate the root mean square value and vibration level according to a specific formula, and conduct frequency weighting analysis of the vibration quantity value.

[0022] Preferably, in the step of using simulation software to simulate the test process, simulate that both ends of the steel plate are fixed on the shaking table, set the vibration frequency and amplitude of the shaking table, select multiple center frequencies for simulation, and conduct acceleration process and spectrum analysis on the simulation results.

[0023] The beneficial effects of the present invention are as follows:

[0024] The local deformation information is accurately reflected: The distributed optical fiber measurement obtains the overall deformation effect of the structure on the spatial resolution length, which can reflect whether there is deformation in this length of the structure, while the accelerometer can only reflect the overall vibration of the structure. In the present invention, the higher the spatial resolution, the more accurate the reflection of the local deformation information of the structure, which helps to more accurately monitor and analyze the subtle changes in rail transit vibration.

[0025] Superior simulation effect and economy: The vibration level calibration test of the shaking table can simulate various vibration conditions that may occur in reality. By setting different acceleration amplitudes and frequencies, various data under different vibration levels in actual engineering can be obtained in advance, and various possible problems can be discovered. Compared with the existing calibration methods, the equipment loading and operation of the present invention are simpler, which can effectively reduce the test cost, improve the test efficiency, and have better simulation effect and economy.

[0026] High test accuracy: The present invention uses numerical simulation to verify the accuracy of the test. On the basis of the existing test data, the actual engineering is further simulated. Through the comparative analysis with the test results, the possible errors and problems in the test can be found in time, so as to optimize and improve the test method and system, and improve the accuracy and reliability of the test. This method not only saves time and labor costs, but also can provide more accurate data support for the monitoring and evaluation of rail transit vibration.

[0027] Comprehensive coverage and stable monitoring: The distributed optical fiber sensor has strong anti-interference ability, long service life and stable performance, and can stably and reliably carry out vibration monitoring in complex environments. Taking advantage of this feature of the distributed optical fiber, the present invention can realize comprehensive vibration monitoring of a relatively long range of rail transit systems, including various parts such as tracks, bridges, and tunnels, providing a strong guarantee for the safe operation of rail transit.

[0028] Reduce the equipment maintenance and replacement costs: Since the distributed optical fiber sensor has a long service life and stable performance, it can carry out vibration monitoring stably for a long time, reducing the frequency of equipment maintenance and replacement, thereby reducing the equipment maintenance and replacement costs and improving the operation efficiency of the rail transit system. Brief Description of the Drawings

[0029] Figure 1 Schematic diagram of the structural member fixture in the shaking table test provided by the embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the structural member deformation test body in the shaking table test provided by the embodiment of the present invention;

[0031] Figure 3 Schematic diagram of the overall structure of the shaking table test provided by the embodiment of the present invention;

[0032] Figure 4 Fiber layout diagram for vibration table test provided by an embodiment of the present invention;

[0033] Figure 5 Vibration simulation of a structure tested on a vibration table provided in an embodiment of the present invention (4 Hz vibration);

[0034] Figure 6 The vibration simulation acceleration process and spectrum analysis (4Hz vibration position 1) provided in the embodiment of the present invention;

[0035] Figure 7 Vibration simulation acceleration process and spectrum analysis provided by the embodiment of the present invention (4Hz vibration position 2)

[0036] In the figure: 1- fixture bottom plate, 2- fixture clamping plate, 3- support rod, 4- fixture screw hole, 5- metal test piece, 6- metal test piece screw hole, 7- vibration machine fixing plate, 8- distributed optical fiber; DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0038] Example:

[0039] In view of the above-mentioned problems, it is necessary to consider factors such as environmental complexity and data rationality in advance, carry out vibration table calibration tests to simulate the real environment, and use numerical calculation methods to verify its practicality and rationality. The target application scenario of the present invention is the vibration acceleration measurement on the concrete structure of the tunnel wall. The vibration is mainly when the train passes by, the rails are stimulated to form dense shock waves, and the shock waves are transmitted to the side walls of the tunnel, forming a solid wave process on the structure. Microscopically, it manifests as a periodic deformation process of the structure, and the vibration processes of different microscopic local areas are inconsistent. The purpose of the present invention is to use distributed grating optical fiber to carry out structural vibration acceleration spectrum measurement tests under the standard environment of the vibration table to verify the feasibility and accuracy of the measurement system.

[0040] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical solutions:

[0041] Step 1: Design the structural parts required for the test, including the deformation structure and fixture.

[0042] Step 1.1, considering the vibration mode of the structural member, ensuring that the frequency and acceleration of the generated solid wave are controllable, designing the deformed structure as a rectangular plate with appropriate thickness, and the material is stainless steel;

[0043] Step 1.2, considering the form of the vibration table surface of the structure, comprehensively considering the structure installation form and the optical fiber layout form, designing the fixture as 4 identical "L" - shaped fixtures, which can fix the stainless - steel plate on the vibration table;

[0044] Step 2, install the test device and conduct the vibration test on the vibration table;

[0045] Step 2.1, arrange the grating - type optical fiber on the vibrating structural member. The length of the sensing section of the optical fiber on each structural member is not less than 1 section (5 m). The optical fibers between multiple structural members are connected in series in sequence, and the longitudinal arrangement method is set;

[0046] Step 2.2, fix the deformed steel plate through the fixture. The fixture is set on both sides of the "wide side" of the deformed steel plate and fixed with nuts;

[0047] Step 2.3, fix the fixed deformed steel plate and the fixture to the vibration table with nuts;

[0048] Step 2.4, turn on the grating - type Φ - OTDR, measure the reflected optical signal returned by the optical fiber, and adjust the parameters of the laser, EDFA, pulse signal generator, etc. in the grating - type Φ - OTDR to obtain a stable and clear signal;

[0049] Step 2.5, set the acceleration amplitude and frequency of the vibration table;

[0050] Step 2.6, turn on the vibration table. When the vibration table performs simple harmonic motion, solid waves can be generated in the structural member, and use the acquisition program of the grating - type Φ - OTDR to collect the reflected optical signal;

[0051] Step 2.7, import the recorded signal data into the computer for data processing and analysis;

[0052] Step 3, obtain the vibration acceleration through the grating - type Φ - OTDR technology, and then convert it into vibration level calculation;

[0053] Step 3.1, the demodulation technology used in the present invention is IQ demodulation. The grating - type Φ - OTDR technology is used to measure the vibration ε(t) of the structure on the vibration table in real - time, and the real - time acceleration a is obtained by means of second - order differentiation:

[0054]

[0055] Step 3.2, acceleration is the basic quantity describing the intensity of the whole - body vibration environment of the human body, in m / s 2The unit is used. The magnitude of vibration is expressed by the root mean square value (r.m.s). The general expression of the root mean square value (r.m.s) is:

[0056]

[0057] Where: a(t) — the acceleration value at a certain moment t, m / s 2 ;

[0058] T — the integration time, s.

[0059] Step 3.3, the magnitude of vibration (abbreviation: vibration level) can be expressed in decibels (dB). The general expression of the vibration level (L) is:

[0060]

[0061] Where: a 0 — the reference acceleration, equal to 10 -6 m / s 2 .

[0062] Step 3.4, in order to represent the whole-body vibration environment of the human body in different axial directions with a single value, frequency weighting analysis of the vibration magnitude can be carried out. The analysis can be calculated according to the following formula on the basis of 1 / 3 octave analysis. The analysis result can be expressed as the root mean square value or decibel value.

[0063] Calculate the root mean square value of the weighted acceleration (a we ).

[0064]

[0065] Where: W j — the weighting coefficient of the j-th 1 / 3 octave band;

[0066] a j — the root mean square value of the acceleration of the j-th 1 / 3 octave band, m / s 2 .

[0067] Step 3.5, calculate the weighted vibration level (L w ):

[0068]

[0069] Where: L j — the vibration level of the j-th 1 / 3 octave band, dB.

[0070] Step 4: Simulate that both ends of the steel plate are fixed on the shaker. Use Abaqus to simulate the change of acceleration vibration level on the steel plate, and compare and analyze it with the test results to verify the rationality. The vibration frequency of the shaker is between 4 and 250 Hz, and the amplitude is 1 mm. Here, 18 center frequencies of 1 / 3 octave are taken as examples (4 Hz, 5 Hz, 6.3 Hz, 8 Hz, 10 Hz, 12.5 Hz, 16 Hz, 20 Hz, 25 Hz, 31.5 Hz, 40 Hz, 50 Hz, 63 Hz, 80 Hz, 100 Hz, 125 Hz, 160 Hz, 200 Hz). The acceleration amplitude is shown in Table 1, and the maximum amplitude diagram is shown in Figure 5 (taking the vibration at 4 Hz as an example), and analyze its acceleration process and spectrum, as shown in Figure 6 and Figure 7 .

[0071] Table 1 Statistical Results of Simulation

[0072]

[0073] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art and related fields without creative work shall fall within the protection scope of the present invention. The structures, devices, and operation methods not specifically described and explained in the present invention, unless otherwise specified and limited, are implemented according to the conventional means in the art.

Claims

1. A vibration table level calibration test system based on distributed optical fiber, characterized in that: include: A fixture used to fix the test structure; A test structure, composed of a deformable structure and a distributed optical fiber, wherein the deformable structure is used to generate deformation under the action of a vibration table, and the distributed optical fiber is used to sense the vibration of the deformable structure; A vibration table for providing vibration excitation; A data acquisition device is used to collect vibration signals sensed by distributed optical fibers.

2. The vibration table level calibration test system based on distributed optical fiber according to claim 1 is characterized in that: The fixture comprises a base plate, a clamping plate and a support rod, wherein the clamping plate is connected to the base plate via the support rod, and screw holes are arranged on the base plate and the clamping plate for fixing the test structure by screws.

3. The vibration table level calibration test system based on distributed optical fiber according to claim 1 is characterized in that: The deformation structure is a rectangular plate made of stainless steel.

4. The vibration table level calibration test system based on distributed optical fiber according to claim 1 is characterized in that: The distributed optical fiber is arranged on the deformable structure. The length of the sensing optical fiber section on each deformable structure is not less than one section, and each section is 5m. The optical fibers between multiple deformable structures are connected in series in sequence and arranged in a longitudinal manner.

5. The vibration table level calibration test system based on distributed optical fiber according to claim 1, characterized in that: The data acquisition device is a grating type Φ-OTDR.

6. A vibration table level calibration test method based on distributed optical fiber, characterized in that: The following steps are involved: Step 1: Design the test structure, including the deformation structure and fixture; Step 2: Install the test device, arrange the distributed optical fiber on the deformable structure, fix the deformable structure on the vibration table by a clamp, and connect the data acquisition device; Step 3: Conduct a vibration test on a vibration table, set the acceleration amplitude and frequency of the vibration table, and collect vibration signals sensed by distributed optical fibers; Step 4: Process and analyze the collected vibration signal, obtain the vibration acceleration, and convert it into vibration level calculation; Step 5: Use simulation software to simulate the test process, compare the simulation results with the test results, and verify the rationality of the test.

7. The vibration table level calibration test method based on distributed optical fiber according to claim 6 is characterized in that: In the step of designing the test structure, the deformation structure is designed as a rectangular plate of moderate thickness and made of stainless steel according to the vibration mode of the structure; the fixture is designed into a specific form according to the form of the structural vibration table table, the structural installation form and the optical fiber arrangement form.

8. The vibration table level calibration test method based on distributed optical fiber according to claim 6, characterized in that: In the step of performing the vibration test on a vibration table, the parameters of the data acquisition device are adjusted to obtain a stable and clear signal.

9. The vibration table level calibration test method based on distributed optical fiber according to claim 6, characterized in that: In the step of processing and analyzing the collected vibration signal, the vibration acceleration is obtained by using IQ demodulation technology, the real-time acceleration a is obtained by quadratic differentiation, and then the root mean square value and vibration level are calculated according to a specific formula, and the frequency-weighted analysis of the vibration value is performed.

10. The vibration table level calibration test method based on distributed optical fiber according to claim 6, characterized in that: In the step of simulating the test process using simulation software, the two ends of the steel plate are simulated to be fixed on the vibration table, the vibration frequency and amplitude of the vibration table are set, multiple center frequencies are selected for simulation, and the acceleration process and spectrum analysis are performed on the simulation results.

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