CN104848980B - Bridge cable Suo Li online test methods and system based on Fibre Optical Sensor - Google Patents
Bridge cable Suo Li online test methods and system based on Fibre Optical Sensor Download PDFInfo
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- CN104848980B CN104848980B CN201510308842.8A CN201510308842A CN104848980B CN 104848980 B CN104848980 B CN 104848980B CN 201510308842 A CN201510308842 A CN 201510308842A CN 104848980 B CN104848980 B CN 104848980B
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Abstract
The present invention provides a kind of bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor, including optical fiber raster vibration sensor group, optical fiber raster vibration (FBG) demodulator and inhaul cable vibration signal processing unit, optical fiber raster vibration sensor group includes series connection several optical fiber raster vibration sensors over the same fiber, each optical fiber raster vibration sensor is based on cantilever beam structure and double grating matching method is designed, Bragg grating is replaced using chirp grating, expand the detection range of sensor, improve the stability and antijamming capability of sensor, the manufacture difficulty of sensor is reduced simultaneously；Optical fiber raster vibration (FBG) demodulator is designed based on edge filter demodulation demodulation principle, and the distributed measurement of Cable power is realized using wavelength-division multiplex technique, make that in fiber-optic signal all the way multiple optical fiber raster vibration sensors can be multiplexed, improve the detectability of system, make it possible the distributed measurement of Cable power, for the on-line checking of Longspan Bridge drag-line provides more reliable technological means.
Description
Technical field
The invention belongs to optical fiber sensing detection technology field, and in particular to a kind of bridge cable Suo Li based on Fibre Optical Sensor
Online test method and system.
Background technology
Drag-line is the important primary structure member of rope class (suspension cable, suspension cable etc.) bridge, and its stress is to evaluate bridge structure
One of whether safe important indicator.Therefore, the Suo Li detection methods of drag-line, particularly online test method are studied, to evaluating
The health status of bridge is significant.
At present, the Suo Li detection methods of suspension cable have various, and such as oil pressure gauge method, magnetic flux method, dynamometry be around-France, frequency method
Deng.But for built bridge, frequency method is almost unique selection.So-called frequency method is exactly to measure to draw by vibrating sensor
The intrinsic frequency of rope is come the method that calculates its Suo Li indirectly.The characteristics of frequency method be it is convenient, flexibly, low cost, precision it is good, available
In on-line measurement.The key of frequency method is the selection of detection means and the recognition methods of drag-line intrinsic frequency.
The conventional monitoring device based on piezoelectric type vibration pickup, exports weak electric signal, and direct transmission range is no more than hundreds of meters,
And be afraid of moist, and easily it is disturbed, it is impossible to the long-term work under natural environment, it is typically only used for periodic detection.In addition, matched
Cable tension test software, it is impossible to realize the automatically retrieval to inhaul cable vibration characteristic frequency, it is impossible to realize automatic measurement.
In recent years, with the development of optical fiber sensing technology, the seminar where me has carried out based on optical fiber grating sensing
Bridge cable force on-line monitoring system research, achieve some achievements, such as 2006《Wuhan University of Technology's journal》Volume 28
The article " novel fiber grating vibrating sensor tests stay cable force " of the 8th phase.But also sent out while these achievements are summarized
It is now following not enough：
(1) less stable of Fibre Optical Sensor.Main cause is that the reflectance spectrum of the sensing element FBG for using is narrower, is received
The influence of mounting process and variation of ambient temperature, the probability of double grating matching failure is big, the design of assembly structure in addition
It is one of the reason for causing sensor failure.
(2) spot measurement, the multiplexing capacity of system is poor, it is difficult to form extensive sensing network, it is impossible to realize distributed survey
Amount.
(3) reliability of recognition methods is poor.The method of identification for using at present mainly recognizes the first natural frequency of drag-line, this
Sample identification difficulty is very big, and reliability is very poor.Reason is (such as) that the intrinsic frequency of some ropes long is very low, or even beyond the low of sensor
Frequency cutoff range, identification will fail.
For above-mentioned problem, the relevant report of solution is up to the present yet there are no.
The content of the invention
The technical problem to be solved in the present invention is：A kind of bridge cable Suo Li on-line checking sides based on Fibre Optical Sensor are provided
Method and system, for the on-line checking of Longspan Bridge drag-line provides more reliable technological means.
The present invention is for the solution technical scheme taken of above-mentioned technical problem：A kind of bridge cable based on Fibre Optical Sensor
Suo Li on-line detecting systems, including optical fiber raster vibration sensor group, optical fiber raster vibration (FBG) demodulator and the drag-line being sequentially connected
Vibration signal processing unit, it is characterised in that：Described optical fiber raster vibration sensor group includes series connection over the same fiber
Several optical fiber raster vibration sensors, each optical fiber raster vibration sensor includes being arranged on cantilever on bridge cable
Beam, the end of cantilever beam is connected with mass, and the upper and lower surface of cantilever beam is arranged with a pair of chirp gratings, 2 chirp gratings
On an optical fiber；Described optical fiber raster vibration (FBG) demodulator includes wideband light source, coupler, wavelength division multiplexer and light electrical resistivity survey
Device array is surveyed, the light of wideband light source enters optical fiber raster vibration sensor group through coupler, and optical fiber raster vibration sensor group is returned
The optical signal for returning enters wavelength division multiplexer by photo-coupler, and the output end of wavelength division multiplexer passes through photodetector array by light
Signal is converted to electric signal and inputs to described inhaul cable vibration signal processing unit again；
Described wavelength division multiplexer includes an input and n output end, the n light positioned at different-waveband of output, light
Wavestrip is wider than the maximum bandwidth of optical fiber raster vibration sensor group reflectance spectrum, and each output end connects a photodetector, n
Individual photodetector constitutes described photodetector array.
By said system, described chirp grating is arranged on the upper and lower surface of cantilever beam by the way of being pasted using 2 points,
And applying prestressing force, wavelength variable quantity is controlled in the range of 1 ± 0.1nm.
By said system, the three dB bandwidth of 2 chirp gratings in same optical fiber raster vibration sensor is 2nm, just
Central wavelength difference under beginning state is less than 0.5nm, and the difference of temperature control coefficient is less than 2pm/ DEG C.
The online test method realized using the bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor, its feature is existed
In：The vibratory response of drag-line is obtained by the optical fiber raster vibration sensor group installed on bridge cable, the vibration of drag-line is analyzed
Frequency spectrum, identifies the fundamental vibration frequency of drag-line, and the relation according to Suo Li and fundamental frequency calculates the Suo Li of drag-line.
As stated above, the method for the fundamental vibration frequency of identification drag-line is：According to any two ranks adjacent spectral peaks in drag-line frequency spectrum
Frequency statistics value ask for the fundamental vibration frequency of drag-line.
Beneficial effects of the present invention are：Bragg grating is replaced using chirp grating, the detection range of sensor is expanded,
The stability and antijamming capability of sensor are improve, while reducing the manufacture difficulty of sensor；Optical fiber raster vibration is demodulated
Instrument is designed based on edge filter demodulation demodulation principle, and the distributed measurement of Cable power is realized using wavelength-division multiplex technique, is made all the way
Multiple optical fiber raster vibration sensors can be multiplexed in fiber-optic signal, the detectability of system is not only increased, also make Cable
The distributed measurement of power is possibly realized, for the on-line checking of Longspan Bridge drag-line provides more reliable technological means；Using filter
Ripple method, reduces frequency identification interval, improves the accuracy of identification；Obtained using the frequency statistics value of the rank spectral peak of arbitrary neighborhood two
The fundamental frequency of inhaul cable vibration is taken, the identification difficulty of guy cable vibrating base frequency is reduced.
Brief description of the drawings
Fig. 1 is the system structure diagram of one embodiment of the invention.
Fig. 2 is the structural representation of fiber-optic grating sensor.
Fig. 3 is optical fiber raster vibration sensor fundamental diagram.
Fig. 4 is the structural representation of optical fiber raster vibration (FBG) demodulator.
In figure：1- optical fiber, the chirp gratings of 2- first, the chirp gratings of 3- second, 4- masses, 5- cantilever beams.
Specific embodiment
With reference to instantiation and accompanying drawing, the present invention will be further described.
A kind of bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor, as shown in figure 1, including the light being sequentially connected
Fine grating vibration sensor group, optical fiber raster vibration (FBG) demodulator and inhaul cable vibration signal processing unit, can also preferably increase
The alarm unit being connected with inhaul cable vibration signal processing unit, analyzes and judges whether drag-line state is safe.Described optical fiber light
Grid vibrating sensor group includes series connection several optical fiber raster vibration sensors over the same fiber, and each fiber grating shakes
Dynamic sensor is as shown in Fig. 2 the cantilever beam 5 (single cantilever beam structure) including being arranged on bridge cable, the end of cantilever beam 5 connects
Mass 4 is connected to, the upper and lower surface of cantilever beam 5 is arranged with a pair of chirp gratings, respectively the first chirp grating 2 and the 2nd Zhou
3,2 chirp gratings of grating of singing are located on an optical fiber 1.Described optical fiber raster vibration (FBG) demodulator is as shown in figure 4, including broadband
Light source, coupler, wavelength division multiplexer and photodetector array, the light of wideband light source are passed through coupler into optical fiber raster vibration
Sensor group, the optical signal that optical fiber raster vibration sensor group is returned enters wavelength division multiplexer, wavelength division multiplexer by photo-coupler
Output end electric signal converted optical signals to by photodetector array input to described inhaul cable vibration signal transacting again
Unit；Described wavelength division multiplexer includes an input and n output end, the n light positioned at different-waveband of output, band of light
The maximum bandwidth of optical fiber raster vibration sensor group reflectance spectrum is wider than, each output end connects a photodetector, n light
Electric explorer constitutes described photodetector array.
(two ends of grating are only pasted by the way of described chirp grating is pasted using 2 points) be arranged on cantilever beam
Upper and lower surface, and apply prestressing force when pasting, wavelength variable quantity is controlled in the range of 1 ± 0.1nm.
The three dB bandwidth of 2 chirp gratings in same optical fiber raster vibration sensor is under 2nm, original state
Central wavelength difference is less than 0.5nm, and the difference of temperature control coefficient is less than 2pm/ DEG C.
The operation principle of optical fiber raster vibration sensor, as shown in Figure 3.(do not have when fiber grating is in original state
State during vibration), the state of the reflectance spectrum of double grating as shown in the picture left above, the now corresponding output signal of sensor such as lower-left
It is a horizontal linear shown in figure.After sensor does sinusoidal vibration, under the effect of inertia of mass, cantilever beam becomes
Shape, produces periodic strain, thus double grating reflectance spectrum also generating period movement, as shown in top right plot, now sensor
Corresponding output signal is a sinusoidal waveform as shown in bottom-right graph.The output signal of sensor has reproduced the vibration shape of sensor
State.
Such as Fig. 4, in optical fiber raster vibration (FBG) demodulator, 1 × 8 type wavelength division multiplexer is increased, its effect is 8 different ripples
The optical fiber raster vibration sensor of section is multiplexed on optical fiber all the way in a passage for entering into (FBG) demodulator, through wavelength division multiplexer
Afterwards, 8 reflected signals of sensor are separated, and are projected from 8 different ports, then be converted into corresponding electricity by photodetector
Signal.
The interval between wave band and sensor wave band shared by above-mentioned optical fiber raster vibration sensor is and wavelength-division
The index of correlation correspondence of multiplexer.
The online test method realized using the above-mentioned bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor, is passed through
The optical fiber raster vibration sensor group installed on bridge cable obtains the vibratory response of drag-line, analyzes the rumble spectrum of drag-line, knows
Do not go out the fundamental vibration frequency of drag-line, the relation according to Suo Li and fundamental frequency calculates the Suo Li of drag-line.
Recognize that the method for the fundamental vibration frequency of drag-line is specially：According to the frequency system of any two ranks adjacent spectral peaks in drag-line frequency spectrum
Evaluation asks for the fundamental vibration frequency of drag-line.
The method mainly includes following three step：(1) rumble spectrum of drag-line is obtained：In the present embodiment, system acquisition is frequently
Rate is set to 20Hz, and the time course datas of every 10 seconds are carried out with a fft analysis, obtains the rumble spectrum of drag-line；(2) drag-line fundamental frequency
Signal identification：Design rope force value according to drag-line, estimates the base frequency range of drag-line, then carries out band logical filter to inhaul cable vibration frequency spectrum
Ripple, reduces frequency identification interval, the corresponding frequency of each rank peak value is read from filtered signal, if there is any three ranks adjacent frequency
Rate meets formula fi+1-fi=fi-fi-1=f0, then difference f0It is the fundamental vibration frequency of drag-line；(3) Suo Li of drag-line is calculated：According to public affairs
Formula T=4ml2f0 2, the Suo Li T of drag-line are calculated, m is the line density of drag-line in formula, and l is the effective length of drag-line.
The link of drag-line state is being evaluated, the Suo Lizuo with the drag-line a certain moment is not as evaluation index, and with one section of division of day and night
Interior Cable power variation tendency is used as Appreciation gist.
Above example is merely to illustrate design philosophy of the invention and feature, its object is to make technology in the art
Personnel will appreciate that present disclosure and implement according to this that protection scope of the present invention is not limited to above-described embodiment.So, it is all according to
The equivalent variations made according to disclosed principle, mentality of designing or modification, within protection scope of the present invention.
Claims (4)
1. a kind of bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor, including the optical fiber raster vibration being sequentially connected are passed
Sensor group, optical fiber raster vibration (FBG) demodulator and inhaul cable vibration signal processing unit, it is characterised in that：Described optical fiber raster vibration
Sensor group includes series connection several optical fiber raster vibration sensors over the same fiber, each optical fiber grating vibration sensor
Device includes the cantilever beam being arranged on bridge cable, and the end of cantilever beam is connected with mass, and the upper and lower surface of cantilever beam is symmetrical
A pair of chirp gratings are provided with, 2 chirp gratings are located on an optical fiber；Described optical fiber raster vibration (FBG) demodulator includes broadband light
Source, coupler, wavelength division multiplexer and photodetector array, the light of wideband light source enter optical fiber grating vibration sensor through coupler
Device group, the optical signal that optical fiber raster vibration sensor group is returned enters wavelength division multiplexer by photo-coupler, wavelength division multiplexer
Output end converts optical signals to electric signal and inputs to described inhaul cable vibration signal transacting list again by photodetector array
Unit；
Described wavelength division multiplexer includes an input and n output end, the n light positioned at different-waveband of output, band of light
The maximum bandwidth of optical fiber raster vibration sensor group reflectance spectrum is wider than, each output end connects a photodetector, n light
Electric explorer constitutes described photodetector array；
Described chirp grating is arranged on the upper and lower surface of cantilever beam by the way of being pasted using 2 points, and applies prestressing force, ripple
Variable quantity control long is in the range of 1 ± 0.1nm.
2. bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor according to claim 1, it is characterised in that：Together
The three dB bandwidth of 2 chirp gratings in one optical fiber raster vibration sensor is the central wavelength difference under 2nm, original state
Less than 0.5nm, the difference of temperature control coefficient is less than 2pm/ °C.
3. the on-line checking realized using the bridge cable Suo Li on-line detecting systems based on Fibre Optical Sensor described in claim 1
Method, it is characterised in that：The vibratory response of drag-line is obtained by the optical fiber raster vibration sensor group installed on bridge cable, point
The rumble spectrum of drag-line is analysed, the fundamental vibration frequency of drag-line is identified, the relation according to Suo Li and fundamental frequency calculates the Suo Li of drag-line.
4. online test method according to claim 3, it is characterised in that：The method of fundamental vibration frequency for recognizing drag-line is：
Frequency statistics value according to any two ranks adjacent spectral peaks in drag-line frequency spectrum asks for the fundamental vibration frequency of drag-line.
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| CN105954791A (en) * | 2016-06-01 | 2016-09-21 | 长江大学 | Vibration ground wave fiber sensing detection system for prevention of burglary and excavation of underground historical relics |
| CN108318158B (en) * | 2017-01-18 | 2020-08-04 | 上银科技股份有限公司 | Method for detecting change of preload value of linear slide rail of machine tool |
| CN108563111A (en) * | 2018-03-28 | 2018-09-21 | 大连理工大学 | Wireless distributed control system and method are vibrated for three layers of chain structure |
| CN108613763B (en) * | 2018-05-11 | 2023-11-03 | 上海市建筑科学研究院 | Fiber bragg grating type inhaul cable force monitoring sensor and sensing method based on frequency method |
| CN109334715A (en) * | 2018-10-24 | 2019-02-15 | 西南交通大学 | A kind of optical fiber orbit occupancy monitoring system and method based on vibration measurement |
| CN109827697A (en) * | 2019-03-19 | 2019-05-31 | 东南大学 | Suspension cable time-varying Suo Li recognition methods based on local mean value mode decomposition |
| CN111238710B (en) * | 2020-01-13 | 2021-04-27 | 武汉理工大学 | Bridge cable force state monitoring device and monitoring method based on weak grating array |
| CN111735532A (en) * | 2020-06-24 | 2020-10-02 | 淮阴工学院 | Bridge resonance testing device and method |
| CN113624267B (en) * | 2021-07-21 | 2024-05-03 | 浙江理工大学 | Fiber bragg grating center wavelength demodulation system and demodulator based on edge filtering |
| CN113720435A (en) * | 2021-09-09 | 2021-11-30 | 长沙深之瞳信息科技有限公司 | Indoor text security fiber sensing system and monitoring method |
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| US6212306B1 (en) * | 1999-10-07 | 2001-04-03 | David J. F. Cooper | Method and device for time domain demultiplexing of serial fiber Bragg grating sensor arrays |
| CN202403851U (en) * | 2011-12-28 | 2012-08-29 | 昆明理工大学 | Fiber Bragg grating load cell of anchor cable frame composite structure |
| CN104215321B (en) * | 2014-09-22 | 2017-02-01 | 西安工程大学 | Circuit breaker vibration monitor system and method based on optical fiber sensors |
| CN104848927A (en) * | 2015-05-21 | 2015-08-19 | 武汉理工大学 | Vibration detection system based on chirped grating sensing and wavelength division multiplexing technology |
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