CN216816727U - Low-frequency FBG acceleration sensor based on cross reed - Google Patents
Low-frequency FBG acceleration sensor based on cross reed Download PDFInfo
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Abstract
The utility model discloses a low-frequency FBG acceleration sensor based on a cross reed, which comprises an FBG, an L-shaped base, a rigid beam, the cross reed, a base and a mass block, wherein the FBG is a fiber Bragg grating; the base is fixed on one end of the L-shaped base and connected with the rigid beam through the cross reed, the FBG (fiber Bragg Grating) is adhered between the rigid beam and the other end of the L-shaped base, the other end of the rigid beam is fixedly provided with the mass block, and the mass block vibrates slightly around the center of the cross reed. According to the FBG acceleration sensor, the influence of friction force is eliminated through the cross reed structure, the sensitivity and stability of the sensor are improved, and the problem that the FBG acceleration sensor is weak in low-frequency vibration measurement capability is solved.
Description
Technical Field
The utility model relates to the technical field of fiber Bragg grating acceleration sensors, in particular to a low-frequency FBG acceleration sensor based on a cross reed.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The measurement of low-frequency vibration signals below 50Hz plays an important role in the fields of seismic monitoring, large and medium engineering structure health monitoring, resource exploration and the like. The traditional electrical sensor is widely applied to the field of vibration acceleration measurement, has the advantages of low cost, high precision, mature technology and the like, is easily subjected to external electromagnetic interference, is complicated in wiring, and can be used for quickly attenuating signals in a long-distance transmission environment, so that the application of the traditional electrical sensor in engineering practice is severely limited. The Fiber Bragg Grating (FBG) acceleration sensor well makes up the defects of the traditional electrical sensor by using the unique advantages of light weight, low transmission loss, strong distributed sensing capability, electromagnetic interference resistance and the like.
In recent years, research on FBG acceleration sensors by researchers at home and abroad has been greatly advanced. Paulo antonnes et al propose a temperature and axial insensitivity single-axis flexible hinge FBG acceleration sensor, the natural frequency is 346.5Hz, and the actual measurement maximum relative error is 0.25%; linessio R P and the like provide a two-dimensional FBG accelerometer based on an omnidirectional flexible hinge, the sensor has a temperature compensation function, the inherent frequencies of an X axis and a Y axis are 747.5Hz and 757.5Hz respectively, and the sensitivity is 100 pm/g; YInyan Weng et al propose a compact fiber grating diaphragm accelerometer based on an L-shaped rigid cantilever beam, the frequency response range is 0-110Hz, and the sensitivity reaches 106.5 pm/g; wei Li et al propose an FBG acceleration sensor based on a diaphragm and a diamond structure, which has a good temperature self-compensation effect at a temperature of 20-90 ℃, a natural frequency of 681.4Hz, a good linear relationship between the sensitivity of the sensor and the vibration frequency in a range of 0-500Hz, and a lateral interference degree of less than 5%.
However, the existing FBG acceleration sensor with a flexible hinge structure has too high natural frequency, and the FBG acceleration sensors with the L-shaped rigid beam structure and the diamond structure rotate to have friction force, so that the sensitivity of the sensor is reduced, and the accurate measurement of low-frequency vibration is difficult to realize in engineering practice.
SUMMERY OF THE UTILITY MODEL
Aiming at the problems and the defects in the prior art, the utility model provides the low-frequency FBG acceleration sensor based on the cross reed, which eliminates the influence of friction force through the structure of the cross reed, improves the sensitivity and the stability of the sensor and solves the problem of weak low-frequency vibration measurement capability of the FBG acceleration sensor.
In order to achieve the purpose, the utility model adopts the following technical scheme:
a low-frequency FBG acceleration sensor based on a cross reed comprises an FBG, an L-shaped base, a rigid beam, the cross reed, a base and a mass block;
the base is fixed on one end of the L-shaped base and connected with the rigid beam through the cross reed, the FBG (fiber Bragg Grating) is adhered between the rigid beam and the other end of the L-shaped base, the other end of the rigid beam is fixedly provided with the mass block, and the mass block vibrates slightly around the center of the cross reed.
Further technical scheme, the stiffening beam is kept away from the top of the one end of quality piece with the top of the L shape base other end is equipped with corresponding slotted hole respectively, fiber bragg grating FBG passes the slotted hole, and both ends are pasted respectively and are fixed the stiffening beam with on the L shape base.
According to the further technical scheme, the cross reed is composed of two reeds, and the middle points of the two reeds are fixedly connected and always form a cross shape.
In a further technical scheme, the base is connected with the rigid beam through the cross reeds, that is, two ends of one of the reeds of the cross reeds are fixedly connected with the top surface of the top end of the base and the bottom surface of the rigid beam on a horizontal plane respectively, and two ends of the other reed of the cross reeds are fixedly connected with the side surface of the top end of the base and the side surface of the rigid beam on a vertical plane respectively.
The further technical scheme comprises two symmetrical cross reeds formed by four reeds, and the base is connected with the rigid beam through the two symmetrical cross reeds.
According to a further technical scheme, the rigid beam and the mass block are made of brass alloy with good rigidity and high density.
In a further technical scheme, the diameter of the slotted hole is 1 mm.
According to a further technical scheme, the mass of the mass block is 10 g.
In a further technical scheme, the ratio of the distance from the center of the cross reed to the FBG and the distance from the center of the cross reed to the center of the mass block is 0.2.
In a further technical scheme, the elastic coefficient of the cross reed is 20000N/m.
Compared with the prior art, the utility model has the following beneficial effects:
1. according to the FBG acceleration sensor based on the cross reed, disclosed by the utility model, when the sensor vibrates, the mass block slightly rotates around the center of the cross reed, so that the influence of friction force is eliminated, the natural frequency of the sensor is reduced, and the sensitivity and the stability are improved.
2. The utility model adopts two symmetrical cross reed structures, thereby effectively inhibiting the influence of transverse crosstalk.
3. The sensor has flat sensitivity response in a low frequency range of 1-65Hz, the dynamic range is 81.89dB, the linearity is 99.97%, the cross reed effectively increases the structural stability, the relative standard deviation of the repeatability of the sensor is 0.89%, and when the transverse crosstalk is-26.97 dB in a working frequency range, the real-time accurate measurement of low-frequency weak vibration signals is realized.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the utility model, and are included to illustrate an exemplary embodiment of the utility model and not to limit the utility model.
FIG. 1 is a schematic view of the overall structure of the sensor of the present invention;
FIG. 2 is a structural vibration model of the sensor of the present invention;
FIG. 3 is a graph of the effect of mass on sensor sensitivity and natural frequency;
FIG. 4 shows the distance L1Distance L3The effect on sensor sensitivity and natural frequency;
FIG. 5 shows the cross spring coefficient k2The effect on sensor sensitivity and natural frequency;
FIG. 6 is a schematic diagram of a test system according to a second embodiment;
FIG. 7 is a time domain response curve and a frequency domain response curve of the sensor output at different frequencies in the second embodiment;
FIG. 8 is the amplitude-frequency characteristics of the sensor according to the second embodiment;
FIG. 9 is a linear fit of the sensor of the second embodiment;
FIG. 10 is a graph showing the results of the sensor stability test in example two;
FIG. 11 is the time domain and frequency domain impulse response curves of the sensor in the second embodiment;
FIG. 12 is a graph showing the results of the lateral immunity test of the sensor according to the second embodiment.
The device comprises a fiber Bragg grating FBG (fiber Bragg Grating), a L-shaped base, a rigid beam, a cross reed, a base, a mass block, a slot hole and a rigid beam, wherein the FBG1 is a fiber Bragg Grating, 2 is an L-shaped base, 3 is a rigid beam, 4 is a cross reed, 5 is a base, 6 is a mass block, 7 is a slot hole.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The terms "mounted," "connected," "fixed," and the like in this application are to be construed broadly, e.g., as meaning a fixed connection, a detachable connection, or an integral connection; the connection may be direct, indirect through an intermediate medium, an internal connection between two elements, or an interaction relationship between two elements; to those skilled in the art, the above terms are to be understood as having the specific meanings of the present invention according to specific situations and not as being limiting.
Example one
Aiming at the problem that the low-frequency vibration measurement capability of the FBG acceleration sensor is weak, the utility model provides the low-frequency FBG acceleration sensor based on the cross reed, the influence of friction force is eliminated through the structure of the cross reed, and the sensitivity and the stability of the sensor are improved.
As shown in the following FIG. 1, the utility model provides a low-frequency FBG acceleration sensor based on a cross reed, which comprises a fiber Bragg grating FBG1, an L-shaped base 2, a rigid beam 3, a cross reed 4, a base 5 and a mass block 6;
the base 5 is fixed on one end of the L-shaped base 2, the base 5 is connected with the rigid beam 3 through the cross reed 4, the fiber Bragg grating FBG1 is pasted between the rigid beam 3 and the other end of the L-shaped base 2, the other end of the rigid beam 3 is fixedly provided with the mass block 6, and the mass block 6 slightly vibrates around the center of the cross reed 4.
The top end of one end of the rigid beam 3, which is far away from the mass block 6, and the top end of the other end of the L-shaped base 2 are respectively provided with a corresponding slotted hole 7 with the diameter of 1mm, the fiber bragg grating FBG1 penetrates through the slotted hole 7, and two ends of the fiber bragg grating FBG1 are respectively fixed on the rigid beam 3 and the L-shaped base 2 in a two-point bonding manner, so that the chirp phenomenon caused by bonding of a grid area is avoided.
In this embodiment, the mass block 6 is an inert mass block, which is commonly used for damping, and on one hand, the center of gravity of the device can be reduced, and on the other hand, the vibration amplitude can be reduced, which is beneficial to improving the low-frequency vibration measurement capability of the sensor.
The cross reed 4 is composed of two reeds, the middle points of the two reeds are fixedly connected and always form a cross shape, the base 5 is connected with the rigid beam 3 through the cross reed 4, namely, the two ends of one of the cross reeds 4 are fixedly connected with the top surface of the top end of the base 5 and the bottom surface of the rigid beam 3 on the horizontal plane respectively, and the two ends of the other reed of the cross reed 4 are fixedly connected with the side surface of the top end of the base 5 and the side surface of the rigid beam 3 on the vertical plane respectively.
In this embodiment, two symmetrical cross-shaped reeds are included, and the base is connected with the rigid beam through the two symmetrical cross-shaped reeds. Through cross reed connection base and rigid beam, can reduce the influence of horizontal crosstalk, eliminate the influence of frictional force, improve sensor sensitivity and stability.
In addition, the sensor of the utility model uses a single optical fiber, which can not eliminate the influence of temperature, further optimize the structure, adopt double optical fiber measurement, eliminate the influence of temperature and improve the sensitivity of the sensor.
The realization principle of the sensor provided by the utility model is as follows:
when the sensor is excited by external vibration, the mass block can vertically deflect along with the inertial force, and the rigid beam is used as a translation structure to convert the vertical deflection of the mass block into the axial deflection of the FBG. The mass block vibrates slightly around the center of the cross reed to enable the FBG to generate uniform strain, so that the central wavelength of reflected light of the mass block is influenced, the drift amount of the central wavelength of the reflected light is proportional to the linear displacement amount of the mass block and is also proportional to acceleration, and therefore the acceleration can be obtained by measuring the drift amount of the central wavelength of the reflected light, and sensing of external vibration is achieved.
Specifically, as shown in fig. 2, when the vibration excitation signal acceleration a acts in the sensitive direction of the sensor, the mass vibrates slightly around the cross reed under the action of the inertial force.
When an acceleration a is applied to the sensor, the displacement Δ x of the mass relative to the base under the action of a resultant force F directed vertically downwards can be expressed as:
in the formula, m is mass of the mass block, and K is total elastic coefficient (N/m) of a system consisting of the optical fiber and the cross reed.
The effect of the resultant force F on the entire system is now divided into two parts, one of which F1Stretching the optical fiber by a rigid beam1Comprises the following steps:
T1＝k1·Δx1 (2)
in the formula, k1Is the modulus of elasticity of the optical fiber. Let the Young's modulus of the optical fiber be EfCross sectional area AfThe effective working length of the optical fiber is l, then
Another part F2The cross reed generates the bending amount Deltax through the rigid beam2Is composed of
T2＝4k2·Δx2 (3)
In the formula, k2Is the spring constant of the reed. Assuming that the spring plate has an elastic modulus E, a width b, a thickness h and a length d, the spring plate has a thickness of h
The distance from the center of the cross reed to the optical fiber is set to be L1Distance L from the rigid beam2Distance L from the center of the mass3Then, according to the geometrical characteristics of the structure and the lever principle, it can be known that: f1＝T1·L1/L3，F2＝T2·L2/L3；Δx1＝Δx·L1/L3，Δx2＝Δx·L2/L3. From F to F1+F2Therefore, the following steps are carried out:
simplifying the system total elastic coefficients K and K1、k2The relationship of (1) is:
the strain epsilon experienced by the fiber is:
finally, the sensitivity S of the FBG acceleration sensor is obtained as follows:
in the formula, λBIs the central wavelength of the grating, PeIs the effective elasto-optic coefficient of the fiber.
The natural frequency f of the FBG acceleration sensor is:
the natural frequency of the low-frequency FBG acceleration sensor based on the cross reed is 90Hz because the vibration signal frequency of earthquakes, large and medium engineering structures and the like is below 50Hz, so that the sensor has flat sensitivity response below 50 Hz. Based on the above, the key structural parameters of the sensor are optimized so as to improve the sensitivity of the sensor.
As can be seen from the equations (7) and (8), the mass m of the mass of the sensor, and the distance L from the center of the cross reed to the optical fiber1Distance L from the center of the mass3Ratio L of1/L3Elastic coefficient k of cross reed2And the effective length l of the fiber has a direct effect on the sensor sensitivity and natural frequency. The grating region length of the fiber grating is generally 10mm, and the effective length of the selected optical fiber in this embodiment is 15 mm.
This example uses Origin software to analyze m, L1/L3、k2Influence of three key parameters on the sensitivity and natural frequency of the sensor, wherein the rigid beam and the mass block of the sensor are made of brass alloy with good rigidity and high density, the elastic modulus of the brass alloy is 100GPa, and the density of the brass alloy is 8500kg/m3(ii) a The cross reed is made of spring steel with good elasticity, the elastic modulus of the spring steel is 210GPa, and the density of the spring steel is 7850kg/m3(ii) a The cross-sectional area of the optical fiber was 1.23X 10-8m2The elastic modulus is 73GPa, and the central wavelength of the grating is 1558.5 nm.
Firstly, the mass m of the mass is changed from 1g to 40g, and other parameters are respectively substituted into a theoretical derivation formula to obtain the influence of the mass m on the sensitivity and the natural frequency of the sensor, as shown in fig. 3.
As can be seen from fig. 3, the mass blocks of different masses have a large influence on the sensor sensitivity and the natural frequency. The larger the mass of the mass, the higher the sensitivity of the sensor and the smaller the natural frequency. When m is 5g, the natural frequency of the sensor reaches about 140Hz, and the sensitivity is only 110 pm/g; when m is 40g, the natural frequency of the sensor is reduced to about 50Hz, and the sensitivity is increased to 940 pm/g. In order to meet the requirement of low-frequency measurement below 50Hz, the mass of the mass block is selected to be 10g, the natural frequency of the sensor is about 90Hz, and the sensitivity is more than 200 pm/g.
Secondly, let the distance L from the center of the cross reed to the optical fiber1Distance L from the center of the mass3The ratio of (a) to (b) varies from 0 to 1.5,other parameters are respectively substituted into a theoretical derivation formula to obtain L1/L3The effect on sensor sensitivity and natural frequency is shown in fig. 4.
As can be seen from FIG. 4, with L1/L3The natural frequency of the sensor is increased continuously, and the sensitivity is increased firstly and then reduced. When the ratio is 0.1, the sensor has higher sensitivity which is 260pm/g, but the natural frequency is only 50Hz, which does not meet the design requirement. When the ratio reaches 0.4, the natural frequency is more than 150Hz, and meanwhile, the sensitivity is reduced to only 150pm/g, so that the requirement is not met; when the ratio is more than 0.4, the requirement is further not satisfied. When the ratio is 0.2, the natural frequency is 90Hz, the sensitivity is about 250pm/g, the requirement of low-frequency measurement below 50Hz can be realized, and the sensitivity is high.
Finally, let the cross reed elastic coefficient k2Changing from 0 to 95000N/m, and substituting other parameters into theoretical derivation formula to obtain cross reed elastic coefficient k2The effect on sensor sensitivity and natural frequency is shown in fig. 5.
As can be seen from FIG. 5, the spring constant k of the cross spring2Has a great influence on the sensitivity of the sensor and has a small influence on the natural frequency. k is a radical of2Varying from 0 to 95000N/m, the sensitivity dropped from 300pm/g to 150pm/g and the natural frequency increased from 85Hz to 125 Hz. Therefore, the cross reed with the elastic coefficient of 20000N/m is selected as the elastic element in the embodiment, and the natural frequency of the sensor is about 90Hz and the sensitivity reaches 250 pm/g.
According to the engineering application requirement of low-frequency measurement, the natural frequency is ensured to be 90Hz, the sensitivity is about 250pm/g, the size and the weight of the sensor are considered, and the structural parameters of the sensor are shown in Table 1 according to structural parameter analysis.
TABLE 1 sensor construction parameters
In this embodiment, Solidworks software is used to model the sensor, and the results are imported into COMSOL software to perform static stress and modal simulation analysis on the sensor structure. Through simulation analysis, it is further verified that the sensor provided by the utility model can realize the response to the displacement and the strain of the free end, and the deformation quantity does not influence the physical properties of the optical fiber, so that the stability of the sensor can be ensured; the vibration can be regarded as single-degree-of-freedom vibration under the vibration condition, and has stronger transverse anti-interference capability; the cross coupling is small, and the cross interference is effectively reduced.
Example two
The embodiment provides a performance test system of a low-frequency FBG acceleration sensor based on a cross reed, which comprises the FBG acceleration sensor, a vibration table, a signal generator, a signal amplifier, a fiber bragg grating demodulator (built-in light source) and a computer, as shown in FIG. 6.
In the embodiment, the vibration table comprises a calibration table with the model number of MWY-JZQ50, the maximum amplitude of the vibration table reaches 12.5mm, and the maximum acceleration of the vibration table is 45.5 g; a signal function generator (DG1022) of RIGOL company, the sampling rate of which is 1GSa/a, and 14 quasi-wave-shaped functions and rich standard configuration interfaces are provided; the signal amplifier (MWY-TZQ50) has a frequency response range of 1-15000Hz and a signal-to-noise ratio of more than 75dB, and is matched with a signal function generator to amplify the function signal.
Firstly, before testing, the optical fiber is pasted by a two-point pasting method, so that the chirp phenomenon caused by pasting in a grid region is avoided, specifically, one end of the optical fiber is placed in a corresponding slot hole in a rigid beam, pasted by UV glue and fixed by irradiating an ultraviolet lamp for 40s, the tail end of the optical fiber is prestressed by a weight with the mass of 20g, and then the optical fiber is fixed by the UV glue and the ultraviolet lamp.
In the testing process, the circulator is used as a connecting component, light waves of the broadband light source are transmitted to the acceleration sensor, the light within a certain wavelength range is reflected back after the FBG, then the light is transmitted to the demodulator through the circulator, the central wavelength of the light waves changing along with the vibration moment is demodulated, and finally the acquired data is transmitted to the computer. The demodulation wavelength range of the fiber grating demodulator (MWY-FBG-CS800) used in the test is 1528-.
The performance test system provided by the embodiment is used for testing the performance of the FBG acceleration sensor, and specifically comprises:
(1) in the test of the output response characteristic of the sensor, the amplitude of the output acceleration of the vibration table is set to be 5m/s2The vibration frequencies are 20Hz and 40Hz respectively, and the time domain signal and the corresponding frequency domain signal measured by the FBG acceleration sensor are shown in fig. 7.
As can be seen from fig. 10, the sensor can obtain the sine excitation inputted from the outside well, and the perfect sine waveform shows that the stress applied to the FBG is uniform, and there is no chirp and multi-peak phenomenon. The time domain curve amplitudes measured at two different frequency points under the same acceleration input are similar, and the fact that the response of the sensor in the working frequency band is flat is proved.
(2) In the test of the amplitude-frequency characteristic and the dynamic range of the sensor, the acceleration of the vibration table is set to be 10m/s2The signal generator generates 1-150Hz excitation, the output frequency of the vibration table is changed by the step length of 5Hz, and when the natural frequency of the sensor is approached, the step length is reduced to 2Hz, and an amplitude-frequency response curve of the acceleration sensor is obtained, as shown in figure 8.
As can be seen from FIG. 11, the sensor has a good flat area at 1-65Hz, 1Hz being the minimum vibration frequency that the signal generator can produce. The natural frequency of the sensor is 94 Hz.
The dynamic range of the FBG acceleration sensor can be expressed as the maximum drift lambda of the FBG center wavelengthmaxAnd demodulation system resolution lambdaminThe relation expression of the ratio of the logarithm of (A) is as follows:
the maximum drift amount of the center wavelength of the FBG in the test is 1243pm, and the resolution of the fiber grating demodulator used by the test system is 0.1 pm. The dynamic range of the FBG acceleration sensor is calculated to be 81.89 dB.
(3) In the test of the sensitivity and the linearity of the sensor, the output frequencies of the vibration table are set to be 10Hz, 20Hz, 40Hz and 60Hz respectively, and the step length is 1m/s2Changing accelerationThe degree is 1-20m/s2And recording the change of the FBG center wavelength under different frequencies to obtain a linearity fitting line, as shown in FIG. 9.
The sensitivity of the acceleration sensor is 242.70pm/g, 241.64pm/g, 240.89pm/g and 249.14pm/g when the input frequency is 10Hz, 20Hz, 40Hz and 60Hz, and the corresponding linearity is R2＝0.9998、R2＝0.9994、R2＝0.9996、R20.9999. The result shows that the FBG acceleration sensor has good linear relation between the central wavelength drift amount and the input acceleration amplitude, the average sensitivity is 243.59pm/g, and the minimum detectable acceleration of the sensor in the test is 0.05m/s2。
(4) In the sensor stability test, the output frequencies of the vibration table are set to be 20Hz and 40Hz respectively, and the acceleration is set to be 5m/s respectively2、10m/s2、15m/s2The sensor output was recorded every 1 hour to test the stability of the sensor output response. The test adopts relative standard deviation RSD to express the repeatability error of the sensor, and the expression is as follows:
in the formula, SD is a standard deviation,
are the corresponding average values.
The results of the experiment are shown in FIG. 10, when the frequency was 20Hz, 5m/s2、10m/s2、15m/s2The relative standard deviations of the corresponding FBG center wavelength drift amounts are respectively 1.75%, 0.54% and 1.09%, and when the frequency is 40Hz, the relative standard deviations of the corresponding FBG center wavelength drift amounts are respectively 0.67%, 0.54% and 0.77%, so that the repeatability error of the sensor is small, and the stability is good.
(5) In the sensor impact response test, an impact signal is applied to the FBG acceleration sensor, the output of the sensor is as shown in fig. 11, and fig. 11 is a time domain curve of the impact response and a frequency domain response after FFT of the time domain signal. The experimental result shows that the maximum amplitude of the impact response is 94.29Hz, and the natural frequency of the sensor is about 94Hz from the side, which is consistent with the amplitude-frequency response test result, so that the correctness of the experimental result is further verified.
(6) The transverse anti-interference capability is an important performance index of the single-degree-of-freedom FBG acceleration sensor, and the transverse interference is the FBG central wavelength drift lambda when the acceleration excitation signal acts on the transverse axis direction under the same frequencyCdAnd FBG central wavelength drift amount lambda when acting on the main shaft directionMdThe logarithmic ratio of (c) is expressed by the transverse crosstalk eta, and the expression is as follows:
the sensor has improved the lateral immunity to interference from structural considerations including the cross spring design and the use of rigid beams.
In order to verify the transverse anti-interference characteristic of the sensor, the sensor is respectively fixed on a vibration table longitudinally and transversely, the same sinusoidal excitation signal is set, the frequency of the sinusoidal excitation signal is 40Hz, and the acceleration is 10m/s2. The central wavelength drift of the transverse and longitudinal vibrations FBG of the sensor is recorded and the result is shown in fig. 12. As can be seen from fig. 12, the longitudinal response and the lateral response of the sensor are 244.40pm and 10.95pm, respectively, and the lateral crosstalk is calculated to be-26.97 dB, indicating that the sensor can effectively suppress the effect of the lateral interference.
Aiming at the problems that the natural frequency of the flexible hinge structure acceleration sensor is too high, and friction force exists when the L-shaped rigid beam structure and the diamond structure rotate, the utility model provides the FBG acceleration sensor based on the cross reed. The sensor has flat sensitivity response in a low frequency range of 1-65Hz, the dynamic range is 81.89dB, the linearity is 99.97 percent, the cross reed effectively increases the structural stability, the repeatability relative standard deviation of the sensor is 0.89 percent, the transverse crosstalk in a working frequency range is-26.97 dB, and the real-time accurate measurement of low-frequency weak vibration signals can be realized.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (10)
1. The utility model provides a low frequency FBG acceleration sensor based on cross reed which characterized in that: the device comprises an optical fiber Bragg grating FBG, an L-shaped base, a rigid beam, a cross reed, a base and a mass block;
the base is fixed to one end of the L-shaped base and connected with the rigid beam through the cross reed, the Fiber Bragg Grating (FBG) is pasted between the rigid beam and the other end of the L-shaped base, the mass block is fixedly installed at the other end of the rigid beam, and the mass block vibrates slightly around the center of the cross reed.
2. The cross reed based low frequency FBG acceleration sensor of claim 1, characterized in that: the top of the one end of quality piece is kept away from to the stiffening beam with the top of the L shape base other end is equipped with corresponding slotted hole respectively, fiber bragg grating FBG passes the slotted hole, and both ends are pasted respectively and are fixed the stiffening beam with on the L shape base.
3. The cross reed based low frequency FBG acceleration sensor of claim 2, characterized in that: the diameter of the slotted hole is 1 mm.
4. The cross reed based low frequency FBG acceleration sensor of claim 1, characterized in that: the base is connected with the rigid beam through the two symmetrical cross reeds.
5. The cross reed based low frequency FBG acceleration sensor according to claim 1 or 4, characterized in that: the cross reed is composed of two reeds, and the middle points of the two reeds are fixedly connected and always form a cross shape.
6. The cross reed based low frequency FBG acceleration sensor of claim 5, characterized in that: and two ends of one reed of the cross reeds are fixedly connected with the top surface of the top end of the base and the bottom surface of the rigid beam on a horizontal plane respectively, and two ends of the other reed of the cross reeds are fixedly connected with the side surface of the top end of the base and the side surface of the rigid beam on a vertical plane respectively.
7. The cross reed based low frequency FBG acceleration sensor of claim 1, characterized in that: the rigid beam and the mass block are made of brass alloy with good rigidity and high density.
8. The cross reed based low frequency FBG acceleration sensor according to claim 1, characterized in that: the mass of the mass block is 10 g.
9. The cross reed based low frequency FBG acceleration sensor according to claim 1, characterized in that: the ratio of the distance from the center of the cross reed to the FBG to the distance from the center of the cross reed to the center of the mass block is 0.2.
10. The cross reed based low frequency FBG acceleration sensor of claim 1, characterized in that: the elastic coefficient of the cross reed is 20000N/m.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202220608223.6U CN216816727U (en) | 2022-03-18 | 2022-03-18 | Low-frequency FBG acceleration sensor based on cross reed |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202220608223.6U CN216816727U (en) | 2022-03-18 | 2022-03-18 | Low-frequency FBG acceleration sensor based on cross reed |
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| CN216816727U true CN216816727U (en) | 2022-06-24 |
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| CN202220608223.6U Expired - Fee Related CN216816727U (en) | 2022-03-18 | 2022-03-18 | Low-frequency FBG acceleration sensor based on cross reed |
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