CN117387742A - Vibration sensor based on fiber bragg grating and testing method thereof - Google Patents
Vibration sensor based on fiber bragg grating and testing method thereof Download PDFInfo
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- CN117387742A CN117387742A CN202210790130.4A CN202210790130A CN117387742A CN 117387742 A CN117387742 A CN 117387742A CN 202210790130 A CN202210790130 A CN 202210790130A CN 117387742 A CN117387742 A CN 117387742A
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- 239000000835 fiber Substances 0.000 title claims abstract description 124
- 238000012360 testing method Methods 0.000 title claims abstract description 16
- 238000001514 detection method Methods 0.000 claims abstract description 23
- 239000002184 metal Substances 0.000 claims description 24
- 238000009434 installation Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 239000010963 304 stainless steel Substances 0.000 claims description 3
- 238000012935 Averaging Methods 0.000 claims description 3
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 claims description 3
- 238000004026 adhesive bonding Methods 0.000 claims 2
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 238000005259 measurement Methods 0.000 description 7
- 239000013307 optical fiber Substances 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 208000010392 Bone Fractures Diseases 0.000 description 1
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- 238000005299 abrasion Methods 0.000 description 1
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- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002146 bilateral effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
The invention relates to the technical field of vibration sensors, in particular to a vibration sensor based on fiber bragg gratings and a testing method thereof. The vibration sensor based on the fiber bragg grating has smaller volume, is suitable for more use environments, and has more accurate detection results and small errors.
Description
Technical Field
The invention relates to the technical field of vibration sensors, in particular to a vibration sensor based on a fiber bragg grating and a testing method thereof.
Background
The vibration sensor, namely a sensor for vibration test, comprises a mechanical vibration sensor and an electric vibration sensor, wherein the mechanical vibration sensor has the earliest development, but has the defects of low measurable frequency, high abrasion degree, poor precision and the like; the electric vibration sensor comprises a capacitive type, an inductive type, a piezoelectric type and the like, has better performance than the traditional mechanical vibration sensor, can basically meet the requirements of general vibration measurement, and has the defects of low sensitivity, easy interference, small dynamic range and the like. With the development of optical fiber technology, fiber Bragg Gratings (FBGs) are widely applied in the field of vibration sensing due to the advantages of strong anti-interference capability, no need of power supply driving, high sensitivity, large dynamic range and the like.
The existing fiber bragg grating is mostly applied to vibration sensing by utilizing the center wavelength drift caused by the axial strain of the fiber bragg grating, and the concrete implementation mode is that a mass block is connected to an optical fiber ejector rod, when a mechanism fixed by a sensor vibrates, the mass block is driven to vibrate, and the vibration of the mass block drives the fiber bragg grating to axially stretch, so that the vibration of the mechanism can be tested. However, this approach still has a problem: 1. the mass block needs to be connected to one end of the optical fiber, so that the size of the sensor is increased, and the adaptability to the measurement environment is somewhat insufficient, for example, the sensor is difficult to install in a scene with a narrow space; 2. during testing, the vibration can change the period of the fiber bragg grating, and the temperature can influence the period of the fiber bragg grating, so that the detection result is inaccurate.
Disclosure of Invention
The invention provides a vibration sensor based on fiber bragg gratings, which has smaller volume, is suitable for more use environments, and has more accurate detection results and small errors, so as to solve the technical problems of large volume, less applicable environment and large detection errors in the vibration test mode adopting fiber bragg gratings in the prior art.
The technical scheme of the invention is as follows:
the utility model provides a vibration sensor based on fiber bragg grating, is including the elasticity sheetmetal, the elasticity sheetmetal is including installation district and vibration detection area, the installation district be used for with vibration sensor installs on the equipment that awaits measuring, vibration detection area's front is glued and is had a plurality of first fiber bragg grating, vibration detection area's back is glued and is had a plurality of second fiber bragg grating, a plurality of first fiber bragg grating and second fiber grating symmetry set up.
Further, a plurality of the first fiber gratings and the second fiber gratings are each disposed near a root of the mounting area.
Further, the first fiber gratings are arranged in parallel at equal intervals, and the second fiber gratings are arranged in parallel at equal intervals.
Further, the first ends of the plurality of first fiber gratings converge towards the same point, the second ends of the plurality of first fiber gratings diverge, and the angles between every two adjacent first fiber gratings are the same; the first ends of the second fiber gratings converge towards the same point, the second ends of the second fiber gratings diverge, and the angles between every two adjacent second fiber gratings are the same.
Further, the mounting area is provided with mounting holes, and the mounting area is mounted on the equipment to be tested through a fastener.
Further, the mounting area is mounted on the device to be tested in an adhesive manner.
Further, the elastic metal sheet is a 304 stainless steel sheet.
In another aspect of the present invention, a method for testing a vibration sensor based on a fiber bragg grating is provided, including the steps of:
s1, installing the vibration sensor on equipment to be tested through the installation area;
s2, vibration of the equipment to be tested is transmitted to a plurality of first fiber gratings and a plurality of second fiber gratings, and vibration frequency and vibration amplitude detected by each pair of fiber gratings are obtained according to acquisition signals of each pair of fiber gratings;
s3: and averaging the vibration frequency and the vibration amplitude obtained by each pair of fiber gratings to obtain the final vibration frequency and the final vibration amplitude.
After the technical scheme is adopted, compared with the prior art, the invention has the following beneficial effects:
1. the elastic metal sheet is arranged on the equipment to be tested through the mounting area of the elastic metal sheet, and the elastic metal sheet is thin and has small overall volume, so that the elastic metal sheet can be arranged at a very narrow position and is suitable for more scenes.
2. According to the invention, the first fiber bragg grating and the second fiber bragg grating are symmetrically arranged on the front surface and the back surface of the elastic metal sheet, and the influence of temperature can be eliminated by subtracting the measured wavelengths of the pair of symmetrically arranged fiber bragg gratings, so that the measurement result is more accurate; in addition, the number of the fiber gratings is multiple, and compared with the method of directly taking data of one fiber grating, the method has lower error.
Drawings
FIG. 1 is a schematic front view of a resilient metal sheet according to a first embodiment;
FIG. 2 is a schematic view showing the back structure of a resilient metal sheet according to the first embodiment;
FIG. 3 is a schematic diagram of a fiber grating;
fig. 4 is a flowchart of a testing method according to the first embodiment.
Fig. 5 is a schematic front view of a resilient metal sheet according to a second embodiment;
fig. 6 is a schematic view of the back structure of the elastic metal sheet according to the second embodiment.
Wherein,
the vibration detection device comprises an elastic metal sheet 1, a mounting area 11, a mounting hole 111, a vibration detection area 12, a first fiber grating 121 and a second fiber grating 122.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
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 in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.
In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.
Embodiment one:
as shown in fig. 1-2, the present embodiment provides a vibration sensor based on fiber bragg gratings, which can be used for detecting vibration of a mechanical arm, the vibration sensor includes an elastic metal sheet 1, the elastic metal sheet 1 includes a mounting area 11 and a vibration detection area 12, wherein the mounting area 11 is used for mounting the vibration sensor on a device to be tested, the vibration detection area 12 is used for arranging Fiber Bragg Gratings (FBGs), specifically, a plurality of first fiber bragg gratings 121 are glued on a front surface of the vibration detection area 12, a plurality of second fiber bragg gratings 122 are glued on a back surface of the vibration detection area 12, the plurality of first fiber bragg gratings 121 and the second fiber bragg gratings 122 are symmetrically arranged one by one, and each fiber bragg grating is connected to a fiber demodulator (indicated by a dotted line).
FIG. 3 is a schematic diagram of a fiber grating (FBG) in which Bragg gratings are formed, light in the fiber core being reflected and transmitted at each grating face, wherein the reflection at each grating face is weak and most of the light is transmitted for light that does not meet the Bragg condition; for light satisfying the bragg condition, reflection occurs at each grating face, and finally a reflection peak is formed. When the device to be tested vibrates, each fiber bragg grating generates strain, and strain sensing can be realized by monitoring the change of the central wavelength of the reflected light.
Thus, the mounting area 11 of the elastic metal sheet 1 is mounted on the device to be tested, and the elastic metal sheet 1 is thin due to the fact that no mass block exists, the whole size is small, the device can be mounted at a very narrow position, the applicable scene is more, and the risk of fracture caused by too strong stress is hardly existed due to the fact that no mass block exists, so that the safety is higher. In actual measurement, in addition to the fact that the strain causes the center wavelength of the reflected light to drift, the temperature also has a certain influence, and in this embodiment, the front and back surfaces of the elastic metal sheet 1 are symmetrically provided with the first fiber grating 121 and the second fiber grating 122, and taking a pair of fiber gratings as an example, the measured wavelength of the first fiber grating 121 contains an increment caused by the temperature, and the measured wavelength of the second fiber grating 122 corresponding to the first fiber grating 121 also contains an increment caused by the temperature, and the measured wavelengths of the two fiber gratings are subtracted to cancel the influence of the temperature, so that the measurement result is more accurate; in addition, the number of the fiber gratings is multiple, so that the error is lower compared with that of directly taking the data of one fiber grating, and the data of the fiber gratings with extremely large phase difference with the data of other fiber gratings can be removed if necessary, so that the fiber gratings do not participate in calculation, and inaccurate measurement results caused by faults or damages of the fiber gratings are avoided.
As a preferred implementation of this embodiment, a plurality of first fiber gratings 121 and second fiber gratings 122 are each disposed near the root of the mounting area 11 to ensure that the maximum strain can be measured (because the strain is greater nearer the cantilever root when the free end is stressed).
As a preferred implementation manner of this embodiment, the plurality of first fiber gratings 121 are disposed in parallel at equal intervals, and the plurality of second fiber gratings 122 are disposed in parallel at equal intervals.
As a preferred implementation of this embodiment, the mounting region 11 is provided with mounting holes 111, and the mounting region 11 is mounted on the device under test by fasteners, and the vibration detection region 12 is formed as a suspended portion. Alternatively, in other embodiments, the mounting region 11 may be mounted to the device under test by means of adhesive.
As a preferred embodiment of the present example, the elastic metal sheet 1 is 304 stainless steel sheet, and has good elastic resilience.
As a preferred embodiment of the present embodiment, the elastic metal sheet 1 is T-shaped, wherein the length-width-thickness dimension of the mounting region 11 is 20mm×5mm×0.3mm, and the length-width-thickness dimension of the vibration detection region 12 is 15mm×10mm×0.3mm. During manufacturing, firstly selecting a steel sheet with the thickness of 0.3mm, and cutting the steel sheet into the size; and then, three fiber gratings (a 1, b1 and c 1) are bonded on the front surface of the steel sheet in a parallel and 2mm equidistant way by adopting a CC-33A adhesive, and the other three fiber gratings (a 2, b2 and c 2) are bonded on the back surface of the steel sheet in a symmetrical way, wherein the specifications of a pair of fiber gratings at the symmetrical positions are the same.
As shown in fig. 4, the present embodiment further provides a method for testing the vibration sensor based on the fiber bragg grating, which includes the following steps:
s1, mounting a vibration sensor on equipment to be tested through a mounting area 11;
the mounting area 11 is provided with mounting holes 111 for mounting the vibration sensor to the device under test by means of fasteners and suspending the vibration detection area 12.
S2, vibration of the equipment to be tested is transmitted to a plurality of first fiber gratings 121 and a plurality of second fiber gratings 122, and the vibration frequency and the vibration amplitude detected by each pair of fiber gratings are obtained according to signals of each pair of fiber gratings;
vibration of the device to be tested can drive the elastic metal sheet 1 to generate periodic deformation, the periodic deformation can drive the fiber grating (FBG) attached to the cloth to generate strain, and the strain causes the change of the central wavelength of reflected light of the fiber grating.
Time series of fiber grating obtained during actual measurement
The vibration frequency and the vibration amplitude of the time series of the three pairs of fiber gratings a, b and c are respectively solved according to the following steps:
s21: for the obtained time series lambda i (t) performing a Fast Fourier Transform (FFT):
record lambda i And (t) is a vector X with the length of N, and Y is obtained after fast Fourier transform, and the calculation mode is as follows:
wherein,
W n ＝e (-2π)/n
s22: calculating a bilateral spectrum P 2 Then, a single-sided spectrum P is calculated based on the sum of the even signal length L and the single-sided spectrum P 1 ：
Let P 1 Is P 2 Front L/2+1 item, let P thereafter 1 Each item is doubled.
S23: defining a frequency domain f and drawing a single-side amplitude spectrum P 1 ：
Let the sampling frequency of the optical fiber demodulator be f s F is 0 to f s Step length f/2 s Sequence of/L. Establishing f and P 1 Functional relation of P 1 The maximum value of f can be regarded as the vibration frequency measured by the vibration sensor, P 1 The maximum value can be regarded as the maximum amount of wavelength shift, denoted as Deltalambda max ，
Δλ max ＝2K ε ε
Wherein K is ε The FBG strain coefficient, ε is the root strain. In addition, the device comprises a plurality of control circuits,
wherein F is the stress of the free end, L 1 E is the elastic modulus of the cantilever beam material, h is the thickness of the cantilever beam, and b is the width of the cantilever beam root. The deflection at the free end is:
wherein I is a cross-sectional moment of inertia. The free end deflection is obtained by combining the above methods:
thus, the vibration frequency and amplitude measured by each pair of fiber gratings can be obtained.
S3: and averaging the vibration frequency and the vibration amplitude obtained by each pair of fiber gratings to obtain the final vibration frequency and the final vibration amplitude.
The vibration frequencies measured by the FBGs of the three groups a, b and c are equal to |omega B The result of the mean operation can be regarded as the final vibration frequency and amplitude.
From the above, it can be seen that the vibration sensor based on the fiber bragg grating provided in this embodiment has a smaller volume, is suitable for more use environments, and has more accurate detection results and small errors.
Embodiment two:
the manner of attaching the fiber gratings in this embodiment is different from that in the first embodiment. Specifically, as shown in fig. 5, the first ends of the plurality of first fiber gratings 121 converge toward the same point, i.e., point to the same point, and the second ends of the plurality of first fiber gratings 121 diverge outwardly in an annular shape, and the angles between every two adjacent first fiber gratings 121 are the same; correspondingly, as shown in fig. 6, the first ends of the second fiber gratings 122 converge toward the same point, i.e., point to the same point, and the second ends of the second fiber gratings 122 diverge outwardly in a ring shape, and the angles between every two adjacent second fiber gratings 122 are the same.
As a preferred implementation manner of this embodiment, the number of the first fiber gratings 121 is seven, and the angle between every two adjacent first fiber gratings 121 is 15 degrees; correspondingly, the number of the second fiber gratings 122 is seven, and the angle between every two adjacent second fiber gratings 122 is 15 degrees.
As a preferred embodiment of the present embodiment, the elastic metal sheet 1 is rectangular, and the left half in the longitudinal direction is configured as a mounting area, and the right half in the longitudinal direction is configured as a vibration detection area. The first fiber bragg grating 121 at the middle of the front surface of the vibration detection area is parallel to the length direction of the elastic metal sheet 1; at the back of the vibration detection area, the most middle one of the second fiber gratings 122 is parallel to the length direction of the elastic metal sheet 1. Each fiber grating is disposed near the root of the mounting region.
As one embodiment of the present example, the length, width and thickness dimensions of the elastic metal sheet 1 are 30mm×15mm×0.3mm. During manufacturing, firstly selecting a steel sheet with the thickness of 0.3mm, and cutting the steel sheet into the size of 30mm multiplied by 15 mm; then, seven fiber gratings (a 1, b1, c1, d1, e1, f1, g 1) are bonded to the front surface of the steel sheet in a 15-degree arrangement, and seven other fiber gratings (a 2, b2, c2, d2, e2, f2, g 2) are bonded to the back surface of the steel sheet in a symmetrical arrangement. The specific calculation method can refer to the first embodiment, and will not be described herein.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (8)
1. The utility model provides a vibration sensor based on fiber bragg grating, its characterized in that, including elasticity sheetmetal (1), elasticity sheetmetal (1) is including installation district (11) and vibration detection area (12), installation district (11) are used for with vibration sensor installs on the equipment that awaits measuring, the front of vibration detection area (12) is glued there is a plurality of first fiber bragg grating (121), the back gluing of vibration detection area (12) has a plurality of second fiber bragg grating (122), a plurality of first fiber grating (121) and second fiber grating (122) symmetry set up.
2. A fibre-optic grating based vibration sensor according to claim 1, characterized in that a plurality of the first fibre-optic gratings (121) and the second fibre-optic gratings (122) are each arranged near the root of the mounting area (11).
3. The fiber grating-based vibration sensor according to claim 2, wherein a plurality of the first fiber gratings (121) are arranged in parallel at equal intervals, and a plurality of the second fiber gratings (122) are arranged in parallel at equal intervals.
4. The fiber grating-based vibration sensor according to claim 2, wherein first ends of the plurality of first fiber gratings (121) converge toward the same point, second ends of the plurality of first fiber gratings (121) diverge, and an angle between each two adjacent first fiber gratings (121) is the same; the first ends of the second fiber gratings (122) converge towards the same point, the second ends of the second fiber gratings (122) diverge, and the angles between every two adjacent second fiber gratings (122) are the same.
5. A vibration sensor based on fiber bragg gratings according to claim 1, characterized in that the mounting area (11) is provided with mounting holes (111), the mounting area (11) being mounted on the device under test by means of fasteners.
6. A vibration sensor based on fiber bragg gratings according to claim 1, characterized in that the mounting area (11) is mounted on the device under test by means of gluing.
7. A vibration sensor based on fiber bragg gratings according to claim 1, wherein said elastic metal sheet (1) is 304 stainless steel sheet.
8. The method for testing the vibration sensor based on the fiber bragg grating is characterized by comprising the following steps of:
s1, installing the vibration sensor on equipment to be tested through the installation area (11);
s2, vibration of the equipment to be tested is transmitted to a plurality of first fiber gratings (121) and a plurality of second fiber gratings (122), and vibration frequency and vibration amplitude detected by each pair of fiber gratings are obtained according to acquisition signals of each pair of fiber gratings;
s3: and averaging the vibration frequency and the vibration amplitude obtained by each pair of fiber gratings to obtain the final vibration frequency and the final vibration amplitude.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210790130.4A CN117387742A (en) | 2022-07-05 | 2022-07-05 | Vibration sensor based on fiber bragg grating and testing method thereof |
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| CN202210790130.4A CN117387742A (en) | 2022-07-05 | 2022-07-05 | Vibration sensor based on fiber bragg grating and testing method thereof |
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