CN107631739B - Fiber grating vibration/stress composite sensor - Google Patents

Fiber grating vibration/stress composite sensor Download PDF

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Publication number
CN107631739B
CN107631739B CN201710801884.4A CN201710801884A CN107631739B CN 107631739 B CN107631739 B CN 107631739B CN 201710801884 A CN201710801884 A CN 201710801884A CN 107631739 B CN107631739 B CN 107631739B
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fiber grating
fiber
stress
vibration
grating
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CN107631739A (en
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林启敬
姚坤
蒋庄德
赵娜
田边
伍子荣
史鹏
彭纲定
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Xian Jiaotong University
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Xian Jiaotong University
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Abstract

The invention discloses a fiber grating vibration/stress composite sensor, which comprises a substrate thin plate and an optical fiber, wherein the optical fiber is adhered to a central axis on the upper surface of the substrate thin plate; the two fiber gratings are correspondingly adhered to the central position of the shielding device, and the axial direction of the two fiber gratings is coincided with the central axis of the shielding device. The invention can avoid the interference caused by the change of the environmental temperature and simultaneously measure the vibration signal and the stress signal.

Description

Fiber grating vibration/stress composite sensor
Technical Field
The invention relates to a fiber grating vibration/stress composite sensor, in particular to a fiber grating sensor for realizing vibration and stress signal measurement under the condition of temperature environment change.
Technical Field
With the development of miniaturization and integration of devices, a composite sensor capable of measuring two or more signals simultaneously is receiving more and more attention.
Vibration and stress are very important parameters in the engineering field, and often reflect the working and operating states of the equipment or some important parts, so that operators can conveniently understand and regulate the working and operating states, and the working and operating states have important significance for correct use and maintenance and prolonging the service life of the equipment or the important parts.
Compared with the traditional piezoelectric and piezoresistive sensors, the optical fiber sensor is not influenced by electricity and magnetic fields in the environment, and has obvious advantages in harsh environments such as high temperature, high voltage, electronic noise and the like. The optical fiber sensor is easy to realize distributed measurement, long-distance continuous measurement and control can be realized by using the same optical fiber, and information such as strain, damage, vibration, temperature and the like on a manufacturing point can be accurately measured. The main material of the common optical fiber is quartz glass, and the outer layer of the common optical fiber is wrapped with a cladding made of high polymer materials, so that the optical fiber has stronger corrosion resistance compared with a metal sensor, and the service life is long. The optical fiber sensor has various types, and different structural forms and detection methods can be selected according to different use occasions and requirements. The optical fiber sensor has high sensitivity, wide signal frequency band and large transmission capacity.
Disclosure of Invention
The invention aims to provide a fiber grating sensor which can avoid interference caused by environmental temperature change and simultaneously measure vibration signals and stress signals.
In order to achieve the purpose, the invention adopts the technical scheme that:
the fiber grating vibration/stress composite sensor comprises a substrate thin plate and an optical fiber, wherein the optical fiber is adhered to a central axis on the upper surface of the substrate thin plate, the fiber grating is correspondingly adhered to the middle position of the clamped beams at the two ends, and the axial direction of the fiber grating is superposed with the central axis of the clamped beams at the two ends; the two fiber gratings are correspondingly adhered to the central position of the shielding device, and the axial direction of the two fiber gratings is coincided with the central axis of the shielding device.
The optical fiber is engraved with two sections of a first fiber grating and a second fiber grating which are equal in length, and the distance between the head and the tail of the two sections of the gratings is centimeter-level.
The 3dB bandwidth widths of the first fiber grating and the second fiber grating are the same, and the difference value of the central wavelengths of the reflection spectrums of the first fiber grating and the second fiber grating is about half of the 3dB bandwidth width.
The length of the two end clamped beams is greater than that of the first fiber grating, and the length of the shielding device is greater than that of the second fiber grating.
Compared with the prior art, the invention has the following technical advantages:
1. compared with the traditional vibration and stress sensor, the fiber grating vibration/stress composite sensor can simultaneously measure vibration and stress signals, so that the sensor has smaller occupied space and convenient arrangement, and is favorable for the integration development of sensing devices.
2. Compared with the traditional piezoelectric and piezoresistive stress or vibration sensor, the fiber bragg grating vibration/stress composite sensor is not influenced by electricity and a magnetic field in the environment, and has obvious advantages in harsh environments such as high temperature, high voltage, electronic noise and the like; distributed measurement is easy to realize, and long-distance continuous measurement and control can be realized by using the same optical fiber; based on optical fiber sensing, the sensitivity is high, the signal frequency band is wide, and the transmission capacity is large.
3. The interference of the change of the environmental temperature to the vibration signal and the temperature signal measurement result can be effectively eliminated.
4. The fiber grating vibration/stress composite sensor allows the use of light intensity type rear end detection demodulation equipment, and has the advantages of low cost, convenient use and visual result.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention
FIG. 2 is a top view of the present invention
FIG. 3 is a bottom view of the base sheet
Detailed Description
The bottom of the base thin plate 1 of the invention is pasted on the surface of the part to be tested through pasting agent.
Referring to the figure, the optical signal of the broadband light source is injected from the right side of the fiber grating II 3-2. When the environment of the fiber grating vibration/stress composite sensor does not have vibration and stress signals, the optical signals of the broadband light source are transmitted into the fiber grating II 3-2 on the optical fiber 2, due to the reflection effect of the fiber grating II 3-2 on the light, one part of the optical signals return according to the original optical path, and the other part of the optical signals are transmitted through the fiber grating II 3-2 and are transmitted into the fiber grating I3-1. Due to the reflection effect of the first fiber grating 3-1 on light, one part of the light signal which is transmitted into the first fiber grating 3-1 returns according to the original light path, and the other part of the light signal is transmitted through the first fiber grating 3-1 and then is scattered into the air from the end face of the optical fiber, wherein the part of the light signal which is reflected by the first fiber grating 3-1 is transmitted through the second fiber grating 3-2. The central wavelengths of the reflection spectrums of the first fiber grating 3-1 and the second fiber grating 3-2 have a certain difference which is half of the 3dB bandwidth, so that the reflection spectrums of the first fiber grating 3-1 and the second fiber grating 3-2 are overlapped but not completely overlapped.
When the environment of the fiber grating vibration/stress composite sensor has vibration in the direction vertical to the plane of the substrate thin plate 1, the clamped beams 4 at the two ends generate corresponding forced vibration along with the vibration in the environment and drive the fiber grating I3-1 to generate axial strain, and the center of the reflection spectrum of the fiber grating I3-1 is changed along with the tensile effect and the photoelastic effect. And because the grating fiber 3-2 is adhered to the shielding device 5, the grating fiber is insensitive to vibration in the environment, and the center of the reflection spectrum is basically unchanged, the overlapped area of the reflection spectrums of the fiber grating I3-1 and the fiber grating II 3-2 can generate oscillation change along with the vibration in the environment, namely, the intensity of the optical signal which is returned according to the original optical path and is transmitted through the fiber grating II 3-2 can generate oscillation change, and therefore, the vibration signal which is vertical to the plane direction of the substrate sheet in the environment can be obtained by measuring the reflected optical signal.
When the environment of the fiber grating vibration/stress composite sensor has stress along the axial direction of the clamped beams 4 at the two ends, the substrate thin plate 1 is tightly attached to the surface of a measured object, the thickness of the substrate thin plate is small, the clamped beams 4 at the two ends and the fiber grating I3-1 generate corresponding strain under the stress action, and the center of a reflection spectrum of the fiber grating I3-1 can generate displacement under the stretching action and the photoelastic effect. And because the shielding device 5 is insensitive to strain signals in the environment, and the center of the reflection spectrum of the fiber grating II 3-2 is basically unchanged, the area of the overlapped part of the reflection spectrums of the fiber grating I3-1 and the fiber grating II 3-2 can be changed along with the change of stress signals in the environment, namely, the intensity of optical signals returned according to the original optical path can be changed, and therefore, the stress signals in the environment along the axial direction of the clamped beams 4 at the two ends can be obtained by measuring the reflected optical signals.
When the environment of the fiber grating vibration/stress composite sensor has vibration perpendicular to the plane direction of the substrate thin plate 1 and stress along the axial direction of the clamped beams at the two ends 4, the optical signals reflected by the fiber grating I3-1 and the fiber grating II 3-2 simultaneously comprise vibration signals and stress signals, but the change frequency of the stress signals is very low relative to the vibration signals, so that the stress signals along the axial direction of the clamped beams at the two ends 4 in the environment can be obtained by carrying out a low-frequency filter on the collected intensity signals, and the collected intensity signals are subjected to high-pass filtering, so that the vibration signals perpendicular to the plane direction of the substrate thin plate 1 in the environment can be obtained.
When temperature changes exist in a measuring environment, the base sheet 1 is made of uniform materials, the expansion coefficients of all parts of the base sheet 1 are the same, the Bragg wavelengths of the first fiber grating 3-1 and the second fiber grating 3-2 are very close to each other, and under the action of thermal expansion and thermo-optic effects, the Bragg wavelength change values of the first fiber grating 3-1 and the second fiber grating 3-2 are equal, namely the overlapped area of the reflection spectrums of the first fiber grating 3-1 and the second fiber grating 3-2 are kept unchanged, so that the measured value of the fiber grating vibration/stress composite sensor cannot be interfered by the changes of the environment temperature.
The length of the two-end clamped beam 4 in the figure 2 is greater than that of the first fiber grating 3-1; the length of the shielding device 5 is larger than that of the second fiber grating 3-2. The shielding device 5 is insensitive to vibration and stress signals in the environment, so that the optical fiber grating II 3-2 adhered to the shielding device 5 is insensitive to vibration and stress signals in the environment.
When the optical fiber 2 is pasted on the substrate thin plate 1, the first optical fiber grating 3-1 is correspondingly pasted at the middle position of the two end clamped beams 4, and the axial direction of the first optical fiber grating 3-1 is superposed with the central axis of the two end clamped beams 4; the second fiber grating 3-2 is correspondingly adhered to the central position of the shielding device 5, and the axial direction of the second fiber grating 3-2 is superposed with the central shaft of the shielding device 5.
When the fiber grating vibration/stress composite sensor works, the bottom of the base thin plate 1 is adhered to the surface of a part to be measured. The optical signal of the broadband light source enters from the right side of the fiber grating II 3-2.

Claims (4)

1. A fiber grating vibration/stress composite sensor is characterized by comprising a substrate thin plate (1) and an optical fiber (2), wherein the optical fiber (2) is adhered to a central axis of the upper surface of the substrate thin plate (1), a first fiber grating (3-1) is correspondingly adhered to the middle position of a fixed support beam (4) at two ends, and the axial direction of the first fiber grating is superposed with the central axis of the fixed support beam at two ends; the second fiber grating (3-2) is correspondingly adhered to the central position of the shielding device (5), the axial direction of the second fiber grating is coincided with the central shaft of the shielding device (5), the sensor uses a light intensity demodulation method for measurement, the reflection spectrums of the first fiber grating (3-1) and the second fiber grating (3-2) are overlapped but not completely overlapped, when the fiber grating senses the measured signal, the overlapped area between the reflection spectrums of the two fiber gratings is changed, thereby realizing the joint demodulation of two fiber bragg grating signals through the measurement of light intensity change, the length of the clamped beam (4) at the two ends is larger than that of the first fiber bragg grating (3-1), the supporting direction of the beam is the stress measuring direction, in the stress measurement direction, two ends of the shielding device (5) are not connected with the substrate thin plate (1) through the square through holes, in the direction perpendicular to the stress measurement, the two ends of the shield (5) are partially connected with the base sheet (1) through spaced square through holes.
2. The fiber grating vibration/stress composite sensor according to claim 1, wherein two fiber grating I (3-1) and two fiber grating II (3-2) with equal length are engraved on the optical fiber (2), and the distance between the head and the tail of the two fiber grating I (3-1) and the fiber grating II (3-2) is in centimeter level.
3. The fiber grating vibration/stress composite sensor according to claim 2, wherein the 3dB bandwidth widths of the first fiber grating (3-1) and the second fiber grating (3-2) are the same, and the difference between the central wavelengths of the reflection spectra of the first fiber grating (3-1) and the second fiber grating (3-2) is about half of the 3dB bandwidth width thereof.
4. The fiber grating vibration/stress composite sensor according to claim 2, wherein the length of the clamped beam (4) at both ends is greater than the length of the first fiber grating (3-1), and the length of the shield (5) is greater than the length of the second fiber grating (3-2).
CN201710801884.4A 2017-09-07 2017-09-07 Fiber grating vibration/stress composite sensor Active CN107631739B (en)

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CN109631964A (en) * 2019-01-23 2019-04-16 安徽理工大学 A kind of single mode optical fiber sensing probe of the two-parameter multiple groups measuring section of no gelatinization
CN109655033B (en) * 2019-01-24 2020-11-24 中国人民解放军海军工程大学 Real-time monitoring method and system for deformation state of pipe body
CN111504219B (en) * 2020-05-01 2021-11-16 西安交通大学 Few-mode fiber bragg grating three-parameter composite sensor and working method thereof
CN111504220A (en) * 2020-05-01 2020-08-07 西安交通大学 Fiber grating temperature/vibration/strain composite sensor and working method thereof

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CN2575612Y (en) * 2002-10-31 2003-09-24 南开大学 Liquid crystal type liquid level analog display
WO2005083379A1 (en) * 2004-02-26 2005-09-09 Sif Universal Private Limited Multi-arm fiber optic sensor
CN1257388C (en) * 2004-03-12 2006-05-24 吉林大学 Stress strain sensor based on temp insensitiveness of fiber glass raster
CN200955961Y (en) * 2006-08-10 2007-10-03 浙江大学 Coherence multiplexing device for optical fiber Bragg grating sensor
CN100533086C (en) * 2006-12-07 2009-08-26 中国科学院半导体研究所 Optical fiber optical grating pressure sensor and its usage method
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Inventor after: Lin Qijing

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