CN103471702A - Fiber grating vibrating sensor with temperature insensitivity, tunable damping and high precision - Google Patents

Abstract

The invention discloses a fiber grating vibrating sensor with temperature insensitivity, tunable damping and high precision. The fiber grating vibrating sensor comprises a cantilever beam. A permanent magnet is connected at the end portion of the cantilever beam. The upper side and the lower side of the permanent magnet are respectively provided with a sealing coil, wherein the sealing coils are the same in diameter and number of wire turns. The upper surface and the lower surface of the cantilever beam are respectively provided with a sensing grating, wherein the sensing gratings are symmetric. The sensing gratings are led out through transmission optical fibers. The gratings are stuck to the upper side and the lower side of the central axis of the cantilever beam with the constant strength respectively. Due to the fact that the cantilever beam can be stretched or compressed by vibration, the central wavelengths of the two sensing gratings can drift in the negative direction, the measurement of vibration acceleration can be achieved by demodulating the changes of the central wavelengths of the two sensing gratings, the signal measurement accuracy can be effectively improved by the adoption of the double-grating structure, the influences, caused by temperature changes, on the measurement result are eliminated, and the sensor has the temperature insensitivity.

Description

A kind of damping of temperature-insensitive is tunable high precision optical fiber grating vibration transducer

Technical field

The present invention specifically discloses a kind of tunable high precision optical fiber grating vibration transducer of damping of temperature-insensitive.

Background technology

Exist a large amount of oscillation phenomenons in field of engineering technology, vibration survey, in main equipment operation conditions health detection, has vital role in fault pre-alarming.At present method for detecting vibration commonly used is mostly based on the piezoelectric type vibration transducer, and its shortcoming is that measuring accuracy is low, poor stability, and be subject to the impact of electromagnetic interference (EMI), greatly affected measurement and the analysis of vibration signal.With traditional electrical sensor, compare, fiber-optic grating sensor is because having the employing Wavelength-encoding, highly sensitive, and anti-electromagnetic interference (EMI) can work, be easy to the characteristics such as networking and be subject to increasing attention under rugged environment.Fiber-optic grating sensor itself also exists temperature, strain cross sensitivity degree problem, affected to a great extent sensor be applied to popularize.This patent designs a kind of optical fibre vibration sensor of double grating structure, realize the measurement of vibration signal by the difference of two raster center wavelength, effectively solve temperature variation, light source fluctuation, the impact of the factor such as photoelectric transformation efficiency, signal attenuation on sensor performance, increase precision and the stability that tunable electromagnetic damping structure ensures the sensor response in sensor, to adapt to different measurement environment and measurement demand.There is important engineering using value under the application circumstances such as civil engineering, coal, chemical industry.

Summary of the invention

The shortcoming existed in order to solve prior art, the technical solution used in the present invention is as follows:

The technical solution used in the present invention is as follows:

A kind of damping of temperature-insensitive is tunable high precision optical fiber grating vibration transducer, comprise a semi-girder, and the end of described semi-girder connects a block permanent magnet, at described permanent magnet, places respectively up and down the encapsulated coil that diameter is identical with the wire number of turns; The upper surface of described semi-girder and lower surface are symmetrical respectively is provided with a sensing grating, and described sensing grating is drawn by Transmission Fibers.

Described semi-girder adopts beryllium-bronze to make, elastic modulus E=128GPa, and calculation on Natural Frequency can obtain f _n=330Hz.

Described semi-girder is of a size of length L=90mm, height h=1mm, width b=5mm.

The quality m=8g of described permanent magnet.

The centre wavelength of described sensing grating is λ _b=1548.63nm.

Respectively establish a sulculus on the center line of the upper and lower end face at distance semi-girder stiff end 10mm place, described sensing grating adopts epoxide-resin glue that sensing grating is sticked in sulculus.

The annealed processing of described sensing grating.

Described optical fiber raster vibration sensor is arranged in a housing, and Transmission Fibers is drawn in housing, and the position that Transmission Fibers is drawn on housing is provided with a flange.

The test macro of described optical fiber raster vibration sensor comprises vibrator, wideband light source, coupling mechanism, demodulating equipment and calculator display organization, described vibrator carries out exciting to sensor, described wideband light source is by a Transmission Fibers coupling of coupling mechanism and sensor, another Transmission Fibers is connected with demodulating equipment from the exit of coupling mechanism, and described demodulating equipment is connected with computing machine.

The invention has the beneficial effects as follows:

The present invention adopts the passive electromagnetic damping structure to regulate the response characteristic of sensor.The end of semi-girder adopts a block permanent magnet as (oscillator) mass m, place respectively up and down at permanent magnet the encapsulated coil that diameter is identical with the wire number of turns, when electromagnet moves in coil, according to Faraday effect, first in the circle, can produce contrary electromagnetic force and suppress the cantilever vibration of beam, and the acceleration of semi-girder is larger, oppositely electromagnetic force is also larger, makes semi-girder reach as early as possible steady state (SS).In this structure, to produce be passive in damping, and the large I of damping controlled by the number of turn of coil, thereby be highly suitable in vibration transducer and use.

In addition, the present invention sticks on grating respectively the both sides up and down of equi intensity cantilever axis, vibration causes that semi-girder generation stretching/compressing changes, cause the centre wavelength of two sensing gratings that drift in the other direction occurs, by the variation of demodulation two sensing grating central wavelength difference, realize the measurement of vibration acceleration, adopt the double grating structure can effectively promote the signal measurement precision, and eliminated the impact of temperature variation on measurement result, made sensor there is temperature-insensitive; The variation of passing through the double grating central wavelength difference due to this sensor realizes the measurement to vibration signal, thereby the measurement result of sensor is not subject to light source fluctuation, the impact of the factors such as photoelectric transformation efficiency, keep sensing capabilities stable, for adapting to the demand of different measuring situation, sensor adopts the electromagnetic damping structure, good stability and be easy to realize, can regulate the damping of sensor according to the different measuring requirement, realize flexibly the Measurement accuracy of vibration and resonance.The designed optical fibre vibration sensor of the present invention has good prospect of the application under high temperature, high pressure, the deep-etching particular surroundingss such as chemical industry, oil, coal.

The accompanying drawing explanation

Fig. 1: Double-grating sensor principle schematic;

Fig. 2: working sensor schematic diagram;

Fig. 3: structural drawing of the present invention;

Fig. 4: sensor performance test macro;

Fig. 5: the centre wavelength drift under the sensing grating tensile strain;

Fig. 6: the centre wavelength drift under the sensing grating compressive strain;

Fig. 7: two sensing grating central wavelength difference and strain stress relations;

Fig. 8: respond during piezoelectric sensor 30Hz

Fig. 9: respond during piezoelectric sensor 90Hz;

Figure 10: respond during Fibre Optical Sensor 30Hz;

Figure 11: respond during Fibre Optical Sensor 90Hz;

Figure 12: optical fiber and piezoelectric sensor amplitude response trend map;

Figure 13: the vibratory response characteristic of Fibre Optical Sensor under different damping;

Figure 14: Fibre Optical Sensor output and temperature variation graph of a relation;

Figure 15: Fibre Optical Sensor output and time-varying relationship figure;

In figure: 1 flange, 2 Transmission Fibers, 3 sensing gratings, 4 semi-girders, 5 permanent magnets, 6 housings, 7 encapsulated coils, 8 vibrators, 9 optical fiber raster vibration sensors, 10 coupling mechanisms, 11 wideband light sources, 12 demodulating equipments, 13 computing machines.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in detail:

1. theory of the fiber optical is analyzed as follows:

Fiber grating is the light sensitive characteristic that utilizes fiber optic materials, forms a kind of structure of refractive index cycle variation on the fibre core of optical fiber by ultraviolet irradiation technique.The variations in refractive index of fiber grating has changed the waveguide condition of optical fiber, waveguide theory according to fiber grating, when the broadband light wave transmits in sensing grating (FBG), incident light is coupled at the grid region emergence pattern, the light of specific wavelength is reflected back, impregnable transmission is by fiber grating for remaining light, and in fact fiber grating has played the light wave reflection wavelength selector like this.When the temperature of fiber grating surrounding environment or stress change, can cause that grating cycle and refractive index all can change, thereby cause the FBG reflection wavelength to drift about, this variation by the detection of reflected wavelength, just can realize the measurement to strain or temperature variation.

The expression formula of fiber grating foveal reflex wavelength is:

λ _B=2n _effΛ (1)

In formula, n _effrepresent the fiber grating effective refractive index, Λ is the grating cycle.

By (1) formula, can be found out, fiber grating (Bragg) centre wavelength is with n _effwith the conversion of periods lambda and change, the thermo-optic effect that the elasto-optical effect that grating is caused by stress and temperature cause can affect n _eff, the thermal expansion effects that the elastic deformation that strain causes and temperature cause can affect the variation of Λ.When fiber grating cycle and refractive index change, centre wavelength drift formula is:

Δλ＝λ _B(1-P _e)Δε+λ _B(α+ξ)ΔT (2)

In formula, P _erepresent elasto-optical coefficient, Δ ε represents axial strain, and α represents thermal expansivity, and ξ represents thermo-optical coeffecient, Δ T representation temperature variable quantity.In the actual fiber sensor-based system, λ _b, P _e, α, ξ be definite value for specific optical fiber.From (2) formula, fiber grating foveal reflex wavelength is understood the variation of Yin Wendu and stress and is changed, and centre wavelength is simultaneously responsive to temperature and strain.The variation of the centre wavelength that only very difficult differentiation temperature and strain cause respectively from the drift of single fiber bragg grating center wavelength, this temperature and stress cross sensitivity problem that namely optical fiber grating sensing exists in detecting.Thereby, in optical fiber grating sensing application, take measures to eliminate the cross sensitivity problem of sensing grating, realize the measurement respectively of strain or temperature signal, the practical application of fiber-optic grating sensor is had to important value.

Optical fiber raster vibration sensor 9 of the present invention utilizes the strain sensitive characteristic of sensing grating, grating is fixed on to the midline of an equi intensity cantilever designed in advance 4 near stiff end, paste the grating of a same size at the dorsal part of semi-girder 4 simultaneously, because two gratings are in identical external environment, the variation of temperature can cause that two gratings produce wavelength variations simultaneously, eliminates the impact of temperature variation on measurement result.Two gratings are connected in parallel on to two output terminals of coupling mechanism 10, avoid producing the shadow effect of sensing grating.Reflection receivable end connection sensing grating signal demodulating equipment 12(FBGA at coupling mechanism 10), obtain the variable quantity of sensing grating wave length shift, realize the measurement of vibration signal.

As shown in Figure 1, sensing grating 3 sticks on respectively the identical position, both sides up and down of equi intensity cantilever 4, when semi-girder 4 is stressed while bending, sensing grating 3 tension stress modulation, sensor fibre 2 is subject to the compressive stress of formed objects, thereby cause the wavelength of two sensing gratings along contrary direction drift, choose two sensing gratings with identical central wavelength, when semi-girder 4 is stressed while bending deformation, record the variation of two sensing grating wavelength differences, can characterize semi-girder 4 vibrational states, thereby realize the measurement of vibration signal.

Sensor based on semi-girder 4 structures in Fig. 1 can be equivalent to one by lumped mass m, the single-degree-of-freedom second order vibrational system of concentrating spring k and ratio of damping c to form, as shown in Figure 2,

When testee vibrates with a certain speed, if the seat vibration displacement is x, the absolute displacement xm of mass m vibrations, spring force can be expressed as k (x-xm), damping force is c (x-xm), and the displacement of doing simple harmonic oscillation at the effect bottom base of external force F is:

x＝d cos(ωt) (3)

ω is the angular frequency of vibration, and d is the amplitude of vibration.According to Newton second law, following vibration descriptive equation is arranged:

$m{\stackrel{..}{x}}_m+c({\stackrel{.}{x}}_m-\stackrel{.}{x})+k(x_m-x+x_0)=\mathrm{mg}---\left(4\right)$

Kx in formula ₀=mg, make x _r=x _m-x can obtain:

$m({\stackrel{..}{x}}_r+\stackrel{..}{x})+c{\stackrel{.}{x}}_r+{\mathrm{kx}}_r=0---\left(5\right)$

Bringing (3) formula into (5) obtains:

${\stackrel{..}{x}}_r+{2\mathrm{\ξ\ω}}_n{\stackrel{.}{x}}_r+{\mathrm{\ω}}_n^2{x}_r=d{\mathrm{\ω}}^2\cos \left(\mathrm{\ωt}\right)---\left(6\right)$

In formula, damping ratio natural frequency

its steady state solution is:

In formula,

for response amplitude,

for lagging phase, r=ω/ω _nfor frequency ratio.

When r<<1, ξ<1 o'clock, system is done the stable state excited vibration.(7) formula can be reduced to:

Above formula shows the displacement x of mass m with respect to pedestal _rbe directly proportional to the acceleration of pedestal, can realize the measurement of the suffered acceleration of sensor by the change in displacement of measurement quality piece.The spring that Fig. 1 medium tenacity semi-girder 4 is equivalent in mechanical model, (length is L, and thickness is h, and the root width is bl).Fiber grating sticks on respectively the upper and lower surperficial midline near stiff end semi-girder 4, avoids like this grating to produce chirp phenomenon when stressed, improves sensitivity and the stability of grating measuring strain simultaneously.Semi-girder 4 is equivalent to the spring in the second order vibrational system, and the displacement of mass m (being the amount of deflection of semi-girder 4) can mean by the strain of semi-girder 4.During the sensor vibration, the effect that semi-girder 4 is subject to inertial force produces bending, causes that near the strain of the fiber grating of stiff end is:

$\mathrm{\&epsiv;}=\frac{6L}{{\mathrm{Ebh}}^2}F---\left(8\right)$

According to the Elasticity formula,

be that the suffered inertial force of semi-girder 4 is that vibration by matrix causes, and and vibration acceleration be directly proportional.Bringing above formula into obtains:

$\mathrm{\&epsiv;}=\frac{6L}{{\mathrm{Ebh}}^2}F=-\frac{6\mathrm{Lm}}{{\mathrm{Ebh}}^2}\stackrel{..}{x}---\left(9\right)$

When semi-girder 4 vibrations are bent upwards, sensing grating FBG1 produces compressive strain, and FBG2 produces tensile strain; When vibration is crooked downwards, sensing grating FBG2 produces compressive strain, and FBG1 produces tensile strain.From formula (2), the drift of strain and two grating wavelengths of influence of temperature change is:

$\frac{{\mathrm{\&Delta;\&lambda;}}_1}{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000381248880000013.png"\; state="\{\{state\}\}">B</figure-callout>}1}}=(1-P_e)\mathrm{\&epsiv;}+(\mathrm{\&alpha;}+\mathrm{\&xi;})\mathrm{\&Delta;T}=-(1-P_e)\frac{6\mathrm{Lm}}{{\mathrm{Ebh}}^2}\stackrel{..}{x}+(\mathrm{\&alpha;}+\mathrm{\&xi;})\mathrm{\&Delta;T}---\left(10\right)$

$\frac{{\mathrm{\&Delta;\&lambda;}}_2}{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="HDA0000381248880000013.png,HDA0000381248880000081.png"\; state="\{\{state\}\}">B</figure-callout>}2}}=-(1-P_e)\mathrm{\&epsiv;}+(\mathrm{\&alpha;}+\mathrm{\&xi;})\mathrm{\&Delta;T}=(1-P_e)\frac{6\mathrm{Lm}}{{\mathrm{Ebh}}^2}\stackrel{..}{x}+(\mathrm{\&alpha;}+\mathrm{\&xi;})\mathrm{\&Delta;T}---\left(11\right)$

Because two gratings have identical making material and physical characteristics, thereby have identical temperature and the coefficient of strain, temperature is cancelled the impact of sensor wavelength drift.Suppose the reflected wavelength lambda of two sensing gratings _b1=λ _b2, when semi-girder 4 produces the vibration strain, the central wavelength difference of FBG1 and two gratings of FBG2 is:

${\mathrm{\&Delta;\&lambda;}}_{12}={\mathrm{\&Delta;\&lambda;}}_1-{\mathrm{\&Delta;\&lambda;}}_2=-2(1-P_e){\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="6"\; label="B"\; filenames="HDA0000381248880000013.png"\; state="\{\{state\}\}">B</figure-callout>}}\frac{6\mathrm{Lm}}{{\mathrm{Ebh}}^2}\stackrel{..}{x}---\left(12\right)$

The elastic modulus that wherein E is semi-girder 4.From formula (12), the variation that fiber bragg grating center wavelength is poor and the vibration acceleration of exciting source

linear, the difference of passing through in this sensing scheme to measure two raster center wavelength, as sensitive information, has been avoided the impact of temperature variation factor on measurement result in the measuring process, and has been significantly improved sensitivity and resolution.Can realize the measurement to vibration acceleration by the variation of measuring two sensing grating central wavelength difference.

2. sensor design

According to above-mentioned sensing grating principle analysis, the tunable damping optical fiber raster vibration sensor 9 that design has the temperature-insensitive characteristic, sensor semi-girder 4 adopts beryllium-bronze to make as shown in Figure 3, elastic modulus E=128GPa, elastic beam is of a size of L=90mm, h=1mm, b=5mm, mass m=8g, the calculation on Natural Frequency of elastic beam can obtain f _n=330Hz, sensing grating FBG1 and the FBG2 centre wavelength in static situation is λ _b=1548.63nm; sensing grating is carried out to annealing in process and keep reflection wavelength stability; carve a sulculus on the center line of equal strength amount; adopt epoxide-resin glue that sensing grating is sticked on respectively apart from the sulculus on semi-girder 4 stiff end 10mm place center lines; make sensing grating stressed consistent with the deflection of beam direction; dependent variable vibration caused by semi-girder 4 passes on grating; sulculus can play the contact area that increases fiber grating and semi-girder 4; make it become organic whole, play the effect of protection grating simultaneously.In manufacturing process, sensing grating is carried out to pretension and process and to make sensing grating centre wavelength identical and closely attaches with semi-girder 4, the generation that prevents from warbling with the multimodal phenomenon.

Optical fiber raster vibration sensor 9 is arranged in a housing, and Transmission Fibers is drawn in housing, and the position that Transmission Fibers is drawn on housing is provided with a flange 1.

Principle according to Elasticity, when semi-girder 4 free ends are bent by the effect of exciting force, can produce a contrary restitution power on semi-girder 4, if composed of external damping not, the damping of sensor mainly consists of structural damping and air damping two parts of semi-girder 4, because damping is very little, arrives stable state during working sensor long transit time, cause the signal measurement distortion, affect the measuring accuracy of sensor.Therefore, be necessary to make sensor reach as early as possible steady-state response by increasing damper regulation mechanism, promote response speed, sensitivity and the Hz-KHz of sensor, reduce distorted signals.

The damping meeting of semi-girder 4 directly affects response speed and the measuring accuracy of sensor, mostly adopt traditionally the hydraulic damping structure to regulate the vibratory response performance of sensor, slow for the hydraulic damper response speed, the phase place drag angle is large, damping is fixed, and to the vibration of high frequency or amplitude low-frequency can not be controlled effectively by a narrow margin characteristics.The response characteristic that in the present invention, design passive electromagnetic damping structure is regulated sensor.The end of semi-girder 4 adopts a block permanent magnet 5 as (oscillator) mass m, place respectively up and down at permanent magnet 5 encapsulated coil 7 that diameter is identical with the wire number of turns, when electromagnet moves in coil, according to Faraday effect, first in the circle, can produce the vibration that contrary electromagnetic force suppresses semi-girder 4, and the acceleration of semi-girder 4 is larger, oppositely electromagnetic force is also larger, makes semi-girder 4 reach as early as possible steady state (SS).In this structure, to produce be passive in damping, and the large I of damping controlled by the number of turn of coil, thereby be highly suitable in vibration transducer and use.

As shown in Figure 4, the light that wideband light source 11 sends outputs to sensing grating by 2X2 coupling mechanism 10 to the sensor performance test macro, and the light of specific wavelength returns the opposite side A of coupling mechanism 10 by optical grating reflection ₂exit, carry out demodulation by demodulation module FBGA, obtains the variation of two sensing grating centre wavelengths.When 8 pairs of semi-girders 4 of vibrator are vibrated, the wavelength of sensing grating 3 drifts about along contrary direction, by measuring the poor variation of grating wavelength, can realize the measurement to vibration signal.

Optical fiber raster vibration sensor 9 is arranged in a housing 6, and Transmission Fibers 2 is drawn in housing 6.

The test macro of described optical fiber raster vibration sensor 9 comprises wideband light source 11, coupling mechanism 10, demodulating equipment 12 and calculator display organization, described wideband light source 11 is the Transmission Fibers coupling with sensor by coupling mechanism 10, another Transmission Fibers is connected with demodulating equipment 12 from the exit of coupling mechanism 10, and described demodulating equipment 12 is connected with computing machine 13.

The ASE wideband light source 11 that test macro adopts Shenzhen Lang Guang company to produce is as the system testing light source, and output wavelength is 1525-1565nm, and output power is 10mW; The FBGA high speed optic fiber grating photoelectric conversion module that demodulating equipment 12 adopts U.S. Bayspec company to produce, sweep frequency is 5000Hz, step-length is 10pm, signal acquisition module adopts the AD171416 position high-speed signal acquisition module grind magnificent company, by Labview gather, the analyte sensors vibration response signal.

The sensor performance test:

The static properties checking:

Designed double grating sensing arrangement is carried out to the steady-error coefficient property verification, two identical gratings of annealed processing enter wavelength are sticked on respectively to the both sides up and down of equi intensity cantilever 4, apart from stiff end 10mm position, keep direction and semi-girder 4 axis directions of sensing grating to suppress, prevent that chirp phenomenon from appearring in the sensing grating reflection configuration.Sensing grating length is 9mm, centre wavelength 1548.63nm, reflection efficiency 85%, side mode suppression ratio 17.5dB; Two gratings are carried out to the pretension processing, avoid sensing grating to produce slippage errors in stretching and compression process.Be sidelong and set high the precision resistance strain gage at one of sensing grating, the strain-responsive performance of measurement of comparison sensing grating; Adopt the microstrain instrument to regulate the amount of deflection of semi-girder, adopt the response characteristic of strain ga(u)ge and spectrometer (HPDq6103, resolution is 0.1pm) measurement of comparison sensing grating; Semi-girder 4 upwards stretches, is compressed to 500 μ ε from 0 μ ε, and pointwise is offloaded to 0 μ ε, then stretches, is compressed to 500 μ ε downwards, and pointwise is offloaded to 0 μ ε, shown in measurement result following Fig. 5-7:

From Fig. 5-7, there are good linear response relationship in the centre wavelength of sensing grating and strain, the centre wavelength of sensing grating is linear monotonic with stretching strain and rises, when receiving compressive strain, sensing grating centre wavelength is linear monotonic and descends, and the rate of change of sensing grating wave length shift is 1.16pm/ μ ε.When bending strain up or down occurs in semi-girder 4, with the increase of strain, linear monotonic rises two center sensor wavelength difference, the rate of change of sensing grating wave length shift is 2.36pm/ μ ε, and the variable quantity of wave length shift has increased by one times than the sensitivity of monochromatic light gate sensor.

The sensor Dynamic performance examination:

By installation of sensors on shaking table, by the dynamic response performance of ipc monitor sensor.When the shaking table vibration-generating, the vibration force of alternation can cause the bending of sensor semi-girder 4 generating periods, cause that sensing grating produces stretching and compression variation, the drift of sensing grating centre wavelength is through the demodulation of FBGA optical-electric module, analyze the variation of double grating wavelength difference by upper computer software, realize the measurement of vibration acceleration and frequency.YJ9A precision piezoelectric acceleration transducer and optical fibre vibration sensor are fixed on shaking table simultaneously and carry out measurement of comparison, piezoelectric acceleration sensor measurement range 0-10g, sensitivity is 0.1g.The acceleration of setting shaking table is 1g,

Adjust the excited frequency of shaking table, the frequency response curve of sensor is as shown in Fig. 8-12:

Fig. 8-12 be respectively into Fibre Optical Sensor from piezoelectric sensor under different vibration frequencies the time, frequency response curve figure, from diagram, in the scope inner fiber sensor of the 0-100Hz vibration frequency of measuring vibrations platform accurately, frequency error is within 0.1%; Increase along with vibration frequency, the measurement amplitude kept stable of Fibre Optical Sensor, between the wavelength vibrating area, change very little, and the response amplitude of piezoelectric sensor is along with the increase of vibration frequency, the trend reduced occurred, in the survey frequency scope of sensor, Fibre Optical Sensor has more smooth response characteristic, its response amplitude is the sensing grating centre wavelength formed wavelength difference of drifting about, thereby is not subject to the impact of the factors such as environment temperature, intensity of light source fluctuation, photoelectric transformation efficiency; Piezoelectric sensor is owing to itself being variation by the pressurized principle of induction acceleration measurement of piezoelectric ceramics, thereby is subject to the impact of the factors such as piezoelectricity conversion efficiency, sensor response speed, electromagnetic interference (EMI), and Fibre Optical Sensor has higher sensitivity and stability.In experiment, slight fluctuations appears in the optical fibre vibration sensor response curve, and this is because the encapsulating structure of Fibre Optical Sensor in laboratory is stablized and caused not.

Change the number of turns of sensor electrical magnetic damping winding coil, the further frequency response performance of measuring fiber vibration transducer, the vibratory response characteristic of sensor under different damping as shown in figure 13,

As shown in Figure 13, marked change occurs with the difference of damping in the vibration characteristics of sensor, when damping ratio ξ=0.7, optical fibre vibration sensor can be realized the stably measured of vibration signal in the scope of 0-230Hz, along with the frequency of vibration signal constantly increases, the amplitude enlargement factor of sensor changes, and frequency is sensor generation resonance response at 330Hz, the resonant frequency that is sensor is 330Hz, and this is consistent with theoretical analysis result.

The temperature-responsive of sensor and testing fatigue:

In order to verify the response performance of Fibre Optical Sensor under the different temperatures environment, sensor is fixed on shaking table, acceleration is 1g, adjusts calorstat temperature from-10-50 ℃, the accordingly result of sensor as shown in figure 14:

As shown in Figure 14, the fluctuation of the response amplitude of sensor under different temperatures is less than 0.5%, basic not variation.Experimental result shows, adopts the vibration transducer of double grating structure, by measuring the variation of two raster center wavelength difference, can eliminate the impact that temperature variation produces measurement result.Sensing grating is carried out on shaking table to 12 hours testing fatigues, its vibratory response compatible degree as a result is greater than 99%, remains stable response, as shown in figure 15.

Claims (8)

1. the tunable high precision optical fiber grating vibration transducer of the damping of a temperature-insensitive, comprise a semi-girder, it is characterized in that: the end of described semi-girder connects a block permanent magnet, at described permanent magnet, places respectively up and down the encapsulated coil that diameter is identical with the wire number of turns; The upper surface of described semi-girder and lower surface are symmetrical respectively is provided with a sensing grating, and described sensing grating is drawn by Transmission Fibers.

2. sensor as claimed in claim 1 is characterized in that: respectively establish a sulculus on the center line of the upper and lower end face at distance semi-girder stiff end 10mm place, described sensing grating adopts epoxide-resin glue that sensing grating is sticked in sulculus.

3. sensor as claimed in claim 1, it is characterized in that: described optical fiber raster vibration sensor is arranged in a housing, and Transmission Fibers is drawn in housing, and the position that Transmission Fibers is drawn on housing is provided with a flange.

4. sensor as claimed in claim 1, it is characterized in that: the test macro of described optical fiber raster vibration sensor comprises vibrator, wideband light source, coupling mechanism, demodulating equipment and calculator display organization, described vibrator carries out exciting to sensor, described wideband light source is by a Transmission Fibers coupling of coupling mechanism and sensor, another Transmission Fibers is connected with demodulating equipment from the exit of coupling mechanism, and described demodulating equipment is connected with computing machine.

5. sensor as claimed in claim 1 is characterized in that: described semi-girder adopts beryllium-bronze to make, elastic modulus, and calculation on Natural Frequency can obtain, and described semi-girder is of a size of length L=90mm, height h=1mm, width b=5mm.

6. sensor as claimed in claim 1, is characterized in that: the quality m=8g of described permanent magnet.

7. sensor as claimed in claim 1, it is characterized in that: the centre wavelength of described sensing grating is.

8. sensor as claimed in claim 1, is characterized in that: the annealed processing of described sensing grating.

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