KR20160007945A - Intensity-based self-referencing fiber optic vibration sensor - Google Patents

Intensity-based self-referencing fiber optic vibration sensor Download PDF

Info

Publication number
KR20160007945A
KR20160007945A KR1020140086807A KR20140086807A KR20160007945A KR 20160007945 A KR20160007945 A KR 20160007945A KR 1020140086807 A KR1020140086807 A KR 1020140086807A KR 20140086807 A KR20140086807 A KR 20140086807A KR 20160007945 A KR20160007945 A KR 20160007945A
Authority
KR
South Korea
Prior art keywords
light
opening surface
intensity
vibration
length
Prior art date
Application number
KR1020140086807A
Other languages
Korean (ko)
Inventor
반재경
김현호
최상진
호일
김종권
Original Assignee
전북대학교산학협력단
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 전북대학교산학협력단 filed Critical 전북대학교산학협력단
Priority to KR1020140086807A priority Critical patent/KR20160007945A/en
Publication of KR20160007945A publication Critical patent/KR20160007945A/en

Links

Images

Classifications

    • 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

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber vibration sensor capable of precisely measuring vibration of an object using light, and a vibration sensor according to an embodiment of the present invention includes an opening surface for adjusting the intensity of light transmitted according to vibration of a measurement object, A signal processor for calculating a light attenuation factor and an amount of vibration based on the calculated light attenuation factor using the intensity of light and the intensity of the reference light detected by the photodetector and the photodetector, the intensity of which is adjusted at the opening surface; Wherein the length of the first side of the opening surface is longer than the diameter of the light and the length of the second side of the opening surface is shorter than the diameter of the light.

Figure P1020140086807

Description

[0001] Optical intensity-based self-referencing fiber optic vibration sensor [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration sensor, and more particularly, to an optical fiber vibration sensor capable of precisely measuring vibration of an object to be measured using light.

Conventional vibration measurement using electric signals has already been developed to a great extent, but there is a problem in that it can not be accurately measured due to interference from electromagnetic waves and other external environments (humidity, temperature, etc.) there was.

Therefore, research and development of vibration measurement using an optical fiber for exceeding the limit of influence of electromagnetic wave, external environment, precision and the like are actively being actively carried out. These optical fiber vibration sensors are widely installed to measure and understand the state of measurement objects in the transportation industry such as the renewable energy industry such as wind turbine, train, ship, and aircraft, and the construction industry such as bridge, tunnel and building.

However, since the conventional optical fiber vibration sensor has a disadvantage in that it is complicated in structure and expensive, development of a fiber optic vibration sensor capable of being cost-competitive and applicable to parts requiring monitoring of large structures such as bridges, high-rise buildings, tunnels and ships This is a required situation.

Korean Patent Laid-Open Publication No. 2005-0048347 (filed on November 11, 2003)

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber vibration sensor capable of measuring the vibration of an object to be measured through a change in the output light intensity of the sensor in accordance with the vibration of the weight and the elastic body.

It is another object of the present invention to provide an optical fiber vibration sensor capable of adjusting a measurable frequency range of a sensor by changing a natural frequency of a weight and an elastic body.

It is still another object of the present invention to provide an optical fiber vibration sensor capable of changing sensitivity and operating range characteristics of a sensor in accordance with a structural shape and diameter of an aperture.

According to an aspect of the present invention, there is provided a vibration sensor comprising: an opening surface for adjusting intensity of light transmitted according to vibration of a measurement object; A photodetector for detecting intensity-controlled light in the opening surface; And a signal processor for compensating the attenuation of the light source using the intensity of the light detected by the photodetector and the intensity of the reference light and calculating the amount of vibration based on the optical attenuation factor, The length of the second side of the opening surface is shorter than the diameter of the light.

In addition, the length of the second side may be determined by the movement range of the opening surface.

The opening surface may be a rectangular shape in which the first side and the second side are perpendicular to each other.

The vibration sensor according to an embodiment of the present invention may further include an elastic body provided on upper and lower portions of the opening surface and formed symmetrically on both the upper and lower portions of the opening surface.

The elastic body may include zigzag springs.

In addition, the springs may be a right angle zigzag structure.

According to another aspect of the present invention, there is provided a vibration sensing method comprising: adjusting intensity of transmitted light according to vibration of an object to be measured; Detecting intensity-controlled light on the opening surface; And calculating the optical attenuation factor using the intensity of light and the intensity of the reference light detected in the detecting step and calculating the amount of vibration based on the calculated optical attenuation factor, wherein the length of the first side of the opening surface is Is longer than the diameter of the light, and the length of the second side of the opening surface is shorter than the diameter of the light.

The length of the second side may be determined by the movement range of the opening surface.

According to the optical fiber vibration sensor of the present invention, the vibration of the measurement object is measured through the change of the output light intensity of the sensor according to the vibration of the weight-elastic body, so that the structure can be simplified and the price can be reduced.

In addition, the sensitivity and operating range characteristics of the sensor can be changed by changing the structure and diameter of the opening surface.

In addition, it has the advantage of multipoint sensing, and can also be fabricated using MEMS technology.

1 is a conceptual view of an optical fiber vibration sensor according to a preferred embodiment of the present invention,
2 is a conceptual diagram of an optical fiber vibration sensor system,
3 is a view showing a rectangular opening surface having a width b which is aligned perpendicular to the traveling direction of light,
4 is a graph showing the result of measurement of the modulated output optical power for d with four opening widths (b = 1.5, 3.0, 4.5, 6.0 mm)
5 is a graph showing the ratio of the relative displacement Z to the external acceleration a according to the vibration frequency of the base when six attenuation coefficients (ζ = 0.1, 0.5, 0.6, 0.7, 1.0 and 2.0)
6 is a view showing a spring structure applicable to an embodiment of the present invention,
FIG. 7 is a view showing a simulation result of the spring structure shown in FIG. 6 by a three-dimensional finite element method based on ANSYS 10.0;
8 is a table showing the parameters for the designed mass-spring structure,
9 is a graph showing a result of simulation of normalized relative displacement of an opening surface according to an acceleration in which a base vibrates at four different frequencies,
10 is a graph showing a corrected output signal P cal according to the attenuation of the light source and P out and P r according to the attenuation of the source,
11 is a table showing an average value and a standard deviation of the corrected output signal P cal according to attenuation of the light source,
FIG. 12 shows a result of comparison between the proposed sensor response and the commercial sensor response,
13 shows the result of checking the linearity of the proposed sensor response,
14 is a photograph of an experimental apparatus manufactured on a laboratory scale.

Hereinafter, an optical fiber vibration sensor according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, an optical fiber vibration sensor according to a preferred embodiment of the present invention includes a base 100 connected to an oscillating measurement object, and a case 200 surrounding the inside of the sensor.

The interior of the sensor includes a weight 210, an elastic body 220, an aperture 230, a collimator 240, and a mirror 250, It carries up and down motion and has mass m.

The elastic body 220 can be realized as a spring connecting the weight 210 and the case 200 and the opening surface 230 adjusts the intensity of light transmitted through the weight. The optical splitter 240 transmits the light passing through the optical fiber in parallel, and the mirror 250 reflects the light passing through the aperture 230.

2 is a schematic view showing an optical fiber vibration sensor system including the above-described optical fiber vibration sensor. 2, the optical fiber vibration sensor system includes a base 100, a sensor inside the case 200, a light source 300, an optical coupler 400, an optical circulator 500, a photodetector 600, And a signal processing unit 700.

Since the sensors in the base 100 and the case 200 are as described above, the description is omitted.

The light emitted from the light source 300 is divided into the reference light P r and the signal light by the optical coupler 400 and the signal light is input to the optical splitter 240 through the optical circulator 500, do.

The parallel light enters the opening surface 230 whose position changes according to the vibration in the optical fiber vibration sensor, is reflected by the mirror, and the reflected parallel light is input to the optical fiber again by the optical splitter.

At this time, the intensity of the signal varies depending on the position of the opening surface 230 varying with the vibration. Specifically, when the measurement object connected to the base 100 vibrates, the position of the opening surface 230 connected to the elastic bodies 220a and 220b is changed, and the intensity of light passing through the opening surface 230 is reduced.

The opening surface 230 may be formed in various shapes such as a circle, a rectangle, and an ellipse, if necessary. The rectangular opening surface 230 will be described later in detail with reference to Fig.

The signal light P out changed in accordance with the vibration is incident on the photo detector (photo diode or photo detector) 600 after passing through the optical circulator 500. The signal processor 700 calculates the optical attenuation factor using the intensity of the light detected by the optical detector 600 and the intensity of the reference light, and calculates the amount of vibration based on the calculated optical attenuation factor.

Since the light emitted from the light source 300 generally has an unstable value whose intensity changes with time, it is required to have a self-referencing characteristic for correcting the signal light using the change in the intensity of the reference light, Increase. The functions such as noise cancellation and magnetic reference compensation are performed in the signal processor 700.

Equation 1 below shows the ratio between P out and P r , and Equation 2 shows the ratio due to the variation of the source.

Figure pat00001

Figure pat00002

α: Spectral ratio

R : Mirror reflection

Figure pat00003
: Loss in the propagation path of modulated light

Figure pat00004
: Loss in path of reference beam

Figure pat00005
: Input light source power

A (d) : Optical power passed through the opening surface displacement

Figure pat00006
: Power change of input light source

Figure pat00007
: Output optical power

Figure pat00008
: Reference light power

Figure pat00009
: Compensated optical power

Figure pat00010
: Compensated optical power when the light source fluctuates

3 is a view showing an opening surface 230 implemented in a rectangular shape. The light emitted from the light source 240 travels widely and parallelly and has a Gaussian distribution shape. If there is no vibration as shown in FIG. 3, it is installed so as to pass through the center of the opening surface 230.

On the other hand, the transverse dimension of the opening surface 230 is sufficiently longer than the diameter of the light, and is made sufficiently longer than the longitudinal length b. The vertical length b is shorter than the diameter of the light, but it is also possible to make it longer.

More specifically, using a BLS having a wavelength of 1550 nm and an input power of 2 mW as the light source 300, a 1 × 2 optical coupler 400 having a coupling ratio of 1:99, a light source having a beam diameter of 7 mm in diameter The optical fiber vibration sensor can be realized by using the micro stage having the operating range of 0 to 6 mm. In this case, if the distance that the opening surface moves at the center is d, the light passing through the opening surface is d = 0 when the intensity is greatest.

4 is a graph illustrating simulation results of optical power output according to d when the vertical length b of the opening surface 230 is 1.5, 3.0, 4.5, and 6.0 mm, respectively. According to FIG. 4, when the diameter of the opening surface 230 is 4.5 mm in the region of 0.65 mm to 2.35 mm, the sensitivity is 135.4 μW / mm, which is the best linearity.

Accordingly, it is preferable that the vertical length b of the opening surface 230 is determined according to the movement range of the opening surface.

On the other hand, the base time 100 is to vibrate by y (t) = weight (210) is x (t) vibration in Ydinω b t, and having a mass of m of size Y, the frequency ω b, relative between the two Assuming that the vibration is z (t), it can be expressed as shown in Equation 3 below.

Figure pat00011

On the other hand, the vibration of the mass-spring system can be expressed by the following equation (4).

Figure pat00012

Here, z (t) can be summarized as Equation (5) below, with m being the mass, k being the spring constant, and c being the damping coefficient.

Figure pat00013

Here, J is a constant,

Figure pat00014
Wow
Figure pat00015
Represents the phase between the vibration due to the applied force and the vibration of the base.
Figure pat00016
Is the attenuation coefficient,
Figure pat00017
Is the resonance frequency.

The response in the steady state can be expressed as Equation (6) below.

Figure pat00018

Therefore, the ratio between the relative displacement Z of the acceleration and the steady state is applied from the outside when s = ω b / ω n, equal to the equation (7) below.

Figure pat00019

5 is a graph showing the ratio of the relative displacement Z to the external acceleration a according to the vibration frequency of the base when six attenuation coefficients (ζ = 0.1, 0.5, 0.6, 0.7, 1.0 and 2.0) are obtained. As shown in Fig. 5, the region where the acceleration can best be measured is 0? B /? N ? 0.2 and? = 0.7. When ω n is larger than 0.2, it is difficult to measure because it exhibits a nonlinear tendency.

On the other hand, a typical spiral spring may vibrate in the direction of the axis we do not want, and vibration measurements may be inaccurate. Accordingly, in the embodiment of the present invention, a spring having a structure as shown in Fig. 6 can be used.

In the spring structure shown in Fig. 6, the lower part is a spring corresponding to "220a" in Fig. 1, and the upper part is a spring corresponding to "220b" in Fig. As shown, both upper and lower springs symmetrically implement two springs.

Each of the springs is a structure in which the "d" shape is bent in a repeated shape (rectangularly zigzag). The spring constant is expressed by Equation (8) below.

Figure pat00020

Here, k 'is a single spring constant, E is Young's modulus, t is the spring thickness, n is the number of winding the spring, the spring length l, w l represents the width of the spring.

Fig. 6 can be simulated as shown in Fig. 7 using ANSYS 10.0 based on 3D FEM. Here, the same color means the same displacement. Also, it has a Young's modulus of 0.703 × 10 11 N / m 2 , a mass m of 6.325 g, and a size of 10 mm × 4.5 mm. The length of the beam is 50 mm and the thickness is 1 mm.

In this case, according to Equation (8), the spring constant is k c = 0.562 N / m and the natural frequency is ω n '= 300.227 Hz. Simulation results were similar to the values calculated as k = 0.530N / mm, ω n = 291.640Hz.

Since the most suitable result is obtained when the vertical length b of the opening surface 230 is 4.5 mm, the parameters of the mass-spring structure designed by applying the result can be shown in FIG.

9 shows the result of simulating the relative displacement of the opening surface 230 according to four frequencies (0.05? N , 0.1? N , 0.2? N , and 0.4? N ) of the base 100. FIG. Referring to Figure 9, since n 0.2ω waveform can be confirmed from being distorted significantly. In Fig. 9, (a) shows the acceleration at which the base vibrates, (b) shows the normalized relative displacement of the opening surface, and (c) shows the spectrum of (b).

10 is a graph showing the compensated output signal P cal and P out and P r due to the attenuation of the source. 11 is a table showing the compensated P cal average value and the standard deviation according to the attenuation of the source. 10 and 11, it can be confirmed that the optical fiber vibration sensor according to the embodiment of the present invention has a good reliability value showing a relative error within an average of 0.75%. All measurements are the result of 10,000 measurements.

It is also possible to implement an optical fiber vibration sensor with a spiral spring instead of the spring structure shown in FIG. 6, and the experimental results will be described below.

In this experiment, a vibration signal was given using an electric-dynamic shaker (ET-126) controlled by a signal generator. A commercial acceleration sensor (352C33) was installed to compare the performance of the sensor. Data was collected in the LabVIEW program through the DAQ card, and the signal processing was performed using the MATLAB program.

Vibration tests were carried out step by step in the frequency bands of 20, 100, 150, 400, 600 and 2000 Hz. A sinusoidal signal with increasing frequency is delivered by the shaker. The response of the proposed sensor is compared with the commercial sensor. A comparison of the responses with the commercial sensors at various vibrations can be seen in FIG.

Also, as shown in FIG. 13, experiments were performed at various frequencies (20, 100, 150, 400, 600, and 2000 Hz) to verify the linearity of the proposed sensor response. The input voltage was controlled with the frequency of the shaker kept constant. The results show relatively good linearity similar to commercial sensors.

The results obtained from the proposed sensor can be used as a vibration sensor. And the response time of the sensor is slower than that of the commercial sensor. Also, it is susceptible to resonance. However, this can be overcome by using the MEMS method. The sensitivity of the sensor can be optimized by adjusting the mass and spring constant.

14 is a photograph of an experimental apparatus manufactured on a laboratory scale. All experiments were conducted in the environment of general experiment (T = 20 ℃, P = 101325 Pa and H2O = 50%) to exclude the influence of external environment.

Although the optical fiber vibration sensor of the present invention has been described with reference to the preferred embodiments of the present invention, the scope of the present invention is not limited to the above-described embodiments, and modifications, changes And various modifications thereof are possible.

100: Case 200: Case
210: weight 220: elastic body
230: opening surface 240:
250: Mirror 300: Light source
400: optical coupler 500: optical circulator
600: photodetector 700: signal processor

Claims (8)

An opening surface for adjusting the intensity of light transmitted according to the vibration of the measurement object;
A photodetector for detecting intensity-controlled light in the opening surface; And
And a signal processor for compensating the attenuation of the light source using the intensity of the light detected by the photodetector and the intensity of the reference light and calculating the amount of vibration based on the light attenuation factor,
The length of the first side of the opening surface is longer than the diameter of the light,
And the length of the second side of the opening surface is shorter than the diameter of the light.
The method according to claim 1,
The length of the second side
And the movement range of the opening surface is determined by the movement range of the opening surface.
3. The method of claim 2,
Wherein the opening surface is a rectangular shape in which the first side and the second side are perpendicular to each other.
The method according to claim 1,
And an elastic body provided on upper and lower portions of the opening surface and formed symmetrically on both upper and lower portions of the opening surface.
5. The method of claim 4,
The elastic body may be,
Wherein the vibration sensor comprises zigzag shaped springs.
6. The method of claim 5,
The springs,
Wherein the vibration sensor is a zigzag structure.
Adjusting the intensity of transmitted light according to the vibration of the object to be measured;
Detecting intensity-controlled light on the opening surface; And
Calculating a light attenuation ratio using the intensity of the light detected in the detecting step and the intensity of the reference light, and calculating a vibration amount based on the calculated light attenuation rate,
The length of the first side of the opening surface is longer than the diameter of the light,
And the length of the second side of the opening surface is shorter than the diameter of the light.
8. The method of claim 7,
The length of the second side
And the movement range of the opening surface is determined by the movement range of the opening surface.
KR1020140086807A 2014-07-10 2014-07-10 Intensity-based self-referencing fiber optic vibration sensor KR20160007945A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020140086807A KR20160007945A (en) 2014-07-10 2014-07-10 Intensity-based self-referencing fiber optic vibration sensor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020140086807A KR20160007945A (en) 2014-07-10 2014-07-10 Intensity-based self-referencing fiber optic vibration sensor

Publications (1)

Publication Number Publication Date
KR20160007945A true KR20160007945A (en) 2016-01-21

Family

ID=55308473

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020140086807A KR20160007945A (en) 2014-07-10 2014-07-10 Intensity-based self-referencing fiber optic vibration sensor

Country Status (1)

Country Link
KR (1) KR20160007945A (en)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20050048347A (en) 2003-11-19 2005-05-24 대한민국(전남대학교총장) Vibration sensor using optical fiber and vibration measuring method using the same

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20050048347A (en) 2003-11-19 2005-05-24 대한민국(전남대학교총장) Vibration sensor using optical fiber and vibration measuring method using the same

Similar Documents

Publication Publication Date Title
CN105116168B (en) Optical fibre grating three-dimensional acceleration sensor based on flexible hinge
CN108508233B (en) Resonant opto-mechanical accelerometer for use in navigation-level environments
US10401377B2 (en) Optical sensor system and methods of use thereof
Parida et al. Double-L cantilever-based fiber Bragg grating accelerometer
JP5705111B2 (en) Oscillating element sensor for detecting boundary layer transition 1
CN107076584B (en) Optical sensor device, and cable
NL2014518B1 (en) A device for measuring fluid parameters, a method for measuring fluid parameters and a computer program product.
Nishiyama et al. Frequency characteristics of hetero-core fiber optics sensor for mechanical vibration
CN104296856A (en) Sensitization platform fiber bragg grating vibration sensor
CN109945965A (en) The arm-type sensitive diaphragm of optical fiber EFPI ultrasonic sensor supporting beam
Urakseev et al. Microcontroller information-measuring systems on bragg gratings
Fan et al. A dual oblique wing-based low-frequency FBG accelerometer
US9512715B2 (en) Systems and methods for pressure and temperature measurement
Liu et al. Detection of Fundamental Shear Horizontal Guided Waves Using a Surface-Bonded Chirped Fiber-Bragg-Grating Fabry–Perot Interferometer
US20210018531A1 (en) Optomechanical structure with corrugated edge
KR20160007945A (en) Intensity-based self-referencing fiber optic vibration sensor
Nguyen et al. An Optical Fiber Acceleration Sensor Based on a V-Shaped Flexure Hinge Structure
Vallan et al. An intensity based fiber accelerometer
JP5162275B2 (en) Vibration detector
Guan et al. Polymer MOEMS accelerometer
RU2484436C1 (en) Measurement method of pulse pressure, and device for its implementation
Qiu et al. A temperature-insensitive FBG acceleration sensor with sinusoid-shaped curved beams
KR101008120B1 (en) Ultrasonic measuring apparatus using resonator length selective optical fiber interferometer
Villatoro et al. Ultrasensitive vibration sensor based on an asymmetric multi-core optical fiber
JP2005030796A (en) Optical accelerometer

Legal Events

Date Code Title Description
A201 Request for examination
E902 Notification of reason for refusal
AMND Amendment
E90F Notification of reason for final refusal
AMND Amendment
E601 Decision to refuse application
AMND Amendment