KR101698836B1 - Acceleration measuring system using optical fiber - Google Patents

Abstract

The present invention relates to an acceleration measuring system using an optical fiber, in which an accurate earthquake simulation is achieved by accurately measuring acceleration in the three axial directions, power supply on a detecting unit is unnecessary, the configuration is simple, maintenance is almost unnecessary due to improved durability, and a remote control is available. The present invention provides an acceleration measuring system including: a weight matter; an elastic member having one end fixed to the weight matter and an opposite end connected to an object to be measured with acceleration; and an optical fiber extending parallel to the elastic member, having one end connected to the object and an opposite end connected to the weight matter, and including a ring shape part as a portion of the optical fiber.

Description

[0001] ACCELERATION MEASURING SYSTEM USING OPTICAL FIBER [0002]

The present invention relates to an acceleration measuring system using an optical fiber, and more particularly, it is possible to accurately measure acceleration of three axes even at a remote location, to enable a seismic simulation, to improve the durability of the measuring unit, And more particularly, to a triaxial fiber acceleration measurement system capable of saving maintenance costs.

Generally, in order to measure the acceleration of an object, an acceleration sensor generally includes a mass body disposed in the sensor so as to be able to change position, for example, at one end of the spring, and a force acts on the mass body to displace the mass in the longitudinal direction of the spring Has been developed as one of the seismometers for the purpose of measuring the vibration acceleration of an earthquake and measuring the acceleration by using the electric physical quantity, for example, the change of the capacitance in response to the displacement, and recently, It is used for airbag operation, for various purposes such as measurement of acceleration of aircraft, vibration of bridges and so on.

In order to measure an earthquake, the acceleration should be measured for the vibration in the vertical direction to the surface and the vibration in the horizontal direction in parallel. However, since the lateral direction is not specified, a plurality of acceleration sensors must be installed, Has a disadvantage in that the sensitivity is low in the lateral direction.

In order to solve these problems, a three-axis acceleration sensor capable of detecting all of three-axis acceleration is manufactured by MEMS (Micro Electro Mechanical System) technology. Such a three-axis acceleration sensor has a simple manufacturing process and is advantageous in that it is insensitive to temperature change. However, the three-axis acceleration sensor needs to be supplied with power to the sensor unit, and may be damaged due to moisture, short circuit, lightning, There is a durability problem.

Another configuration of the three-axis acceleration is disclosed in Korean Patent No. 10-1427810 (Aug. 1, 2014). Referring to FIG. 6, in the configuration of the three-axis acceleration sensor disclosed in the above patent, a mass body 600 responsive to vibration is disposed inside a case 200 having a rectangular parallelepiped shape in order to measure three-axis acceleration, Y, and z axes guides 300, 400, and 500 for guiding three-axis (x, y, z axis) vibration of the mass body 600 and a sensor unit 700 are provided. However, in such a configuration, the guides 300, 400, and 500 and the mass body 600 are slidably connected to each other so that the configuration is complicated, and accuracy may be lowered due to frictional force inevitably accompanied by sliding. In particular, in sub-zero weather, the moisture entering the guide gap may freeze and become inoperable.

The sensor unit 700 is configured to detect relative displacement of the mass body 600 with a plurality of fiber bragg grating (FBG) sensors, and the maximum measurement range (Gauge Range) is only about 50 mm to 100 mm Therefore, the acceleration detection range is limited.

In addition, the optical fiber FBG sensor uses a low-power broadband light source and the reflected light receiving circuit is accompanied by significant attenuation in the wavelength separation circuit. Therefore, a narrow-band high-power laser light source is used and a very sensitive APD (avalanche photo diode) Compared to the optical time-domain reflector (OTDR), which is used to measure Rayleigh backscattering, the OTDR, which is mainly used for fiber optic cable inspection and maintenance, is mature and has a maximum measuring distance of 260 km. In addition, there is no report on the actual measurement distance of the fiber optic FBG sensor.

Korea Utility Model Registration No. 20-0429342 (2006.10.16) Korean Patent No. 10-1427810 (2014. 08. 01)

D. Marcuse, " Curvature loss formula for optical fibers ", J. Opt. Soc. Amer. B, vol. 66, pp. 216-220, Mar 1976. Copyright ⓒ 2002 Taylor & Francis 0146-8030 / 02 $ 12.00 C .00 DOI: 10.1080 / 0146803029008772, "Simplified Formula of Bending Loss for Optical Fiber ", " SHYH-LIN TSAO, WEN-MING CHENG, Sensors ", National Taiwan Normal University Optical Fiber System Laboratory of Electro-Optical Science and Technology Taipei, Taiwan Andre Martins, Ana M. Rocha, B. Neto, A. L. J. Teixeira, M. Facao, R. N. Nogueira, M. J. Lima, Andre, Modeling of Bend Losses in Single-Mode Optical Fibers, Instituto de Telecomunicacoes, Campus de Santiago, 3810-193 Aveiro, Portugal

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide an acceleration sensor capable of precisely measuring an acceleration in an axial direction without using a guide sliding on a mass body under frictional force, Axis fiber optic acceleration measurement system that is simple in construction, durable and requires little maintenance, and can be operated remotely (for example, approximately 200 km or less).

To achieve this object, according to one aspect of the present invention, An elastic member having one end fixed to the mass body and the other end connected to an object to be measured; And an optical fiber, wherein the optical fiber includes a ring-shaped portion as a portion of an optical fiber extending in parallel with the elastic member, one end connected to the object, and the other end connected to the mass.

The acceleration measurement system may further include an operation unit that calculates a change amount of the radius using a change in the bending light loss generated when the radius of the ring-shaped portion is changed.

The calculation unit may calculate the length change amount of the elastic member from the change amount of the radius and calculate the acceleration from the length change amount.

The calculation unit may calculate the length change amount of the elastic member from the change amount of the radius and calculate the displacement from the length change amount.

According to another aspect of the present invention, there is provided a display device comprising: a rectangular parallelepiped case; A mass disposed within the case; A first elastic member having one end connected to a first vertical edge of the case and the other end connected to the mass; A second elastic member having one end connected to a second vertical edge of the case and the other end connected to the mass; A third elastic member having one end connected to a third vertical edge symmetrical with the first vertical edge of the case and the other end connected to the mass; A fourth elastic member having one end connected to an upper surface of the case and the other end connected to the mass; And first to fourth optical fibers respectively extending along the first to fourth elastic members, wherein one end of each of the first to fourth optical fibers is connected to the mass body, the other end of each of the first to fourth elastic fibers is connected to the case, 1 to 4 < th > optical fiber.

The acceleration measurement system may further include a measurement unit connected to the first through fourth optical fibers to measure a bending light loss.

The present invention is capable of precise seismic simulation by accurately measuring the acceleration in the three-axis direction without using a guide that slides while the mass is subjected to frictional force, does not require power supply to the sensing unit, And can be used semi-permanently. Therefore, it is possible to solve the malfunction and maintenance difficulties experienced in the field of the seismic system and provide a simple and reliable seismic measuring means. In addition, since the remote sensor can be operated by about 200 km, it is possible to provide an early warning of about one minute in comparison with the conventional seismometer, and it is possible to vividly monitor the epicenter behavior which can not be easily detected by the conventional seismometer, It is expected that this earthquake forecast can be realized as a typhoon can be forecasted a few days ago by observing a typhoon that occurred in a region 1,000 km away.

1 is a block diagram schematically showing a configuration of a three-axis optical fiber acceleration measuring system using an optical fiber according to an embodiment of the present invention,
2 is a schematic conceptual view of the sensing part of the optical fiber acceleration measurement system according to an embodiment of the present invention in an initial state,
Fig. 3 is a schematic conceptual view of the sensing unit of Fig. 2 in a state in which a force is applied,
Fig. 4 is a graph conceptually showing the state of Fig. 3,
5 is a graph showing the relationship between the bending radius and the optical loss,
6 is a schematic perspective view of a prior art triaxial acceleration measurement system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, and the advantages and features of the present invention and methods of achieving the same can be clearly understood.

It is to be understood that the present invention is not limited to the embodiments described below, but may be embodied in various forms other than those described in the following description without departing from the technical spirit of the present invention It will be apparent to those skilled in the art.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed and will become apparent to persons skilled in the art upon a reading of this disclosure. It is only defined by the claims.

On the other hand, well-known components, well known operations, and well-known techniques in some embodiments described below are not specifically described for the sake of brevity and for the sake of brevity.

It is also to be noted that like reference numerals refer to like elements throughout the specification and the terms used herein are intended to be illustrative of the embodiments and not to limit the invention.

In this specification, the singular forms include plural forms unless the context clearly dictates otherwise, and the constituents and acts referred to as " comprising (or having) " do not exclude the presence or addition of one or more other constituents and actions .

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs.

Also, commonly used predefined terms are not ideally or excessively interpreted unless they are defined.

Referring to FIG. 1, there is shown a block diagram illustrating a schematic configuration of a three-axis optical fiber acceleration measurement system using an optical fiber according to an embodiment of the present invention. Referring to FIG. 2, 1 is a schematic view of a sensing part of a three-axis optical fiber acceleration measuring system using the optical fiber shown in Fig. 1, and Fig. 3 is a schematic view of the sensing part shown in Fig. 2 A schematic conceptual diagram showing a state in which the acceleration is measured in a state where the sum of the forces acting on the mass is not 0 is shown. Referring to FIG. 4, in the three-axis optical fiber acceleration measurement system shown in FIG. 3, Fig. 7 is a graph showing the coordinates of displaced masses. Fig.

2, the three-axis optical fiber acceleration measurement system according to an embodiment of the present invention may include a measurement unit 1, an optical transmission unit 2, and a sensing unit 3. [ The light source 11 emits light having a predetermined wavelength according to a signal from the control unit 17 and the light is transmitted through the light input / output port 16 and the optical transmission unit 2 to the sensing unit 3, . The optical transmission unit 2 may include an optical fiber connected to the optical fibers 31, 32, 33, and 34 provided in the sensing unit 3. More specifically, as described below, the light transmitted from the ring-shaped portions 27, 28, 29 and 30 of the optical fibers 31, 32, 33, and 34 is transmitted from the sensing portion 3 to the optical transmission portion 2, And then returns to the light input / output port 16 to detect the bending light loss value in the light detecting unit 15. The calculating unit 14 calculates the first to fourth elastic members 23, 24, 25, 26 (A _x , a _y , a _z ) of the three axes is calculated by using the length (the distance between the mass and the reference point) of the three axes. The acceleration thus obtained can be sent to the display unit 13 and displayed to the operator. When a danger sign is detected at a preset value or more, the alarm unit, the warning lamp, and the like can be driven in the I / F (interface) unit 12. Further, the data detected above and the calculated data may be transmitted to another server (not shown).

The sensing unit 3 will be described with reference to Figs. 2 and 3. Fig. The sensing unit 3 may be mounted on an object or an object for detecting acceleration, for example, a vehicle, an aircraft, or a seismic wave to be detected. The sensing unit 3 is connected to the optical port 16 by the optical transmission unit 2.

2, the sensing unit 3 includes a case 50 having a rectangular parallelepiped shape, a mass body 22 disposed inside the case 50, one end connected to the mass body 22 and the other end connected to the case 50, A second elastic member 24 having one end connected to the mass 22 and the other end connected to the second vertical edge of the case 50, a first resilient member 23 connected to the first vertical edge of the mass 22 And the other end is connected to the third vertical edge of the case 50. The other end of the elastic member 25 is connected to the upper surface of the case 50 And may include a fourth elastic member 26.

2, the mass body 22 is disposed at the origin of the xyz coordinate system in a state where the sum of the forces acting on the object to which the sensing unit 3 is mounted is zero, The longitudinal axes of the first elastic member 23 and the third elastic member 25 are on the y axis and the other ends are respectively at Y ₀ and -Y ₀ and the longitudinal axis of the second elastic member 24 is on the x axis , The other end is disposed at X ₀ , the longitudinal axis of the fourth elastic member 26 is on the z-axis, and the other end is disposed at Z ₀ . Therefore, the length of each of the first to fourth elastic members 23, 24, 25, and 26 corresponds to the coordinate value of the other end.

Each of the first to fourth optical fibers 31, 32, 33, and 34 has first to fourth ring-shaped portions 27, 28, 29, and 30 formed by winding once. Each of the first to fourth optical fibers 31, 32, 33 and 34 is connected to the first to fourth elastic members 23, 24, 25 and 26 and the first to fourth connection members 41, 42, 43 and 44 ). The first to fourth connecting members 41, 42, 43 and 44 are formed by the expansion and contraction of the first to fourth elastic members 23, 24, 25 and 26, The first to fourth optical fibers 31, 32, 33 and 34 are arranged at a portion of the first to fourth elastic members 23, 24, 25 and 26, for example, at a central point Connect. The positions of the first to fourth optical fibers 31, 32, 33 and 34 passing through the case 50 are such that the first to fourth optical fibers 31, 32, 33 and 34 are located outside the case 50 Or may be fixed to the case 50 so as not to be drawn in from the outside. Further, the ends of each of the first to fourth optical fibers 31, 32, 33, and 34 may be fixed to the mass body 22.

라고 하면, 도 4와 같이 표현될 수 있다.If the sum of the forces acting on the object to which the sensing part 3 is mounted is not 0, the sum of the forces acting on the mass body 22 is not zero, and therefore, the mass body 22 is operated in any direction It can be displaced by force, for example, as shown in Fig. That is, the coordinates of the mass body 22 are changed to (x, y, z) instead of the origin, and the coordinates of the ends of each of the first to fourth elastic members 23, 24, 25, z) (for convenience, the mass body 22 is regarded as having no volume). At this time, the length of each of the first to fourth elastic members 23, 24, 25,

, It can be expressed as shown in FIG.

)이 도시된다.4, the coordinates (x, y, z) of the mass M located in the three-dimensional space and the four reference points (X ₀ , Y ₀ , -Y ₀ , Z ₀ ) located on the three axes Respectively.

).

)가 산출되었다고 전제하고, 질량체(M)의 좌표값(x, y, z)의 계산 방법이 설명된다.First, as will be described later,

(X, y, z) of the mass M is calculated based on the assumption that the coordinates (x, y, z) of the mass M are calculated.

The relationship between the four distances and the three coordinates can be expressed by the following four equations (1 to 4).

을 얻고, 그 다음 수학식(5)에서 y를 얻는다.Subtracting Equation (3) from Equation (4)

, And then obtains y in the following equation (5).

The final desired y-axis acceleration a _y from ma _y = -ky is then obtained as:

The elastic modulus of the first to fourth elastic members 23, 24, 25, and 26 were all selected to be equal to k.

을 얻고, 수학식(4)에서 수학식(1)을 빼면

를 얻고, 다시 이 두 식간에 빼기를 하면

를 얻고, 다음 식에서 z를 얻는다.Subtracting Equation (3) from Equation (1)

And subtracting the equation (1) from the equation (4)

, And subtracting again between these two

And z is obtained from the following equation.

From the coordinate z in the z-axis direction, z-direction acceleration a _{z is obtained} from ma _z = -kz-mg as follows.

Where g is the gravitational acceleration.

를 얻고, 수학식(4)에서 수학식(2)를 빼면

를 얻는다. 다시 위 두 식을 합하면

를 얻고, 다음 식에서 x를 얻는다.Subtracting Equation (2) from Equation (3)

And subtracting the equation (2) from the equation (4)

. Again, the above two equations

And obtains x in the following equation.

The following obtains the final desired x-axis acceleration a _x from ma _x = - kx as follows:

를 구하면, 위 수학식(6), 수학식(8), 수학식(10)에서 본 발명에서 최종적으로 구하고자 하는 3축 방향의 가속도 a_x, a_y, a_z 를 각각 구할 수 있다.Therefore, four distances from the coordinates (x, y, z) of the mass M to the four reference points (X ₀ , Y ₀ , -Y ₀ , Z ₀ )

The acceleration a _x , a _y , and a _z in the three-axis directions to be finally obtained in the present invention can be obtained from the above equations (6), (8), and (10), respectively.

A method of calculating the changed lengths of the first to fourth elastic members 23, 24, 25, and 26 in the calculating unit 14 using the bending light loss detected by the optical detecting unit 15 and A method of calculating acceleration (a _x , a _y , a _z ) of three axes using this will be described below.

D. Marcuse theoretically analyzed how the optical loss changes when the optical fiber bends, and the relationship between the radius of curvature (R) and the optical loss (L) is derived as follows.

Where η ₁ and η ₂ are constants determined by the index of refraction of the optical fiber, the diameter of the core, the wavelength of the light traveling, and are independent of the radius of curvature.

Fig. 5 shows the relationship between the bending radius (R) and the optical loss (L) obtained on the basis of the results of SHYH-LIN TSAO and WEN-MING CHENG experimentally measured at a wavelength of 1.55 μm. Here, the relationship between the bending radius R and the optical loss L is more approximate to the simple exponential function relation of the following equation (12) than the equation (11).

In addition, the relationship between the bending radius (R) and the optical loss (L) is found to be related to the simple exponential function in the results of the experiment by three persons besides Baekseong and Andre Martins et al. In the present invention, the principle of displacement measurement using an optical fiber is introduced by introducing Equation (12).

가 산출할 수 있다.If the optical loss (L) is obtained by introducing light having a wavelength of 1.55 μm into an optical fiber ring whose radius of curvature is unknown, the radius of curvature (R) can easily be obtained from the following equation (13). The change value of the radius of curvature (that is, the changed length of the elastic member) can be known from the radius of curvature thus obtained, and from this,

Can be calculated.

That is, when the mass body 22 is displaced from the initial state of Fig. 2 as shown in Fig. 3, when the second elastic member 24 is extended and both ends of the second optical fiber 32 are pulled, The radius of the ring-shaped portion 28 is reduced. As a result, the bending light loss becomes large as shown in Fig. 5, and the change is detected by the photodetector 15, and the radius of curvature change DELTA R is obtained in the calculating unit 14, Can be obtained by the following equation (14). Further, the distance X becomes X ₀ +? D.

및 Z)도 거리(X)와 같이 상술된 방법을 변형하여 구해질 수 있으며, 간략성을 위해서 그 설명은 생략된다. 이와 같이 산출된 거리

를 상술된 수학식(6), (6) 및 (7)에 대입하면, x, y, z 축의 가속도가 각각 산출된다.Distance (Y,

And Z can also be obtained by modifying the above-described method such as the distance X, and the description thereof is omitted for the sake of simplicity. The calculated distance

(6), (6), and (7), the accelerations in the x, y, and z axes are respectively calculated.

The first through fourth optical fibers 31, 32, 33 and 34 of the sensing unit 3 can be respectively connected to the optical port 16 through the optical transmission unit 2 and the first through fourth optical fibers 31 and 32 The change in the radius that is generated in the first to fourth ring-shaped portions 27, 28, 29, 30 of the first to third ring-shaped portions 33, 34 can be measured by the photodetector portion 15 as described above. For example, in the case of the 1.55 μm OTDR currently available on the market, the single mode optical fiber measurement distance reaches 260 km. Therefore, a single mode optical fiber is used as the transmission unit 2, and a single mode optical fiber having a wavelength of 1.55 μm When light is used, it is possible to separate the sensing unit 3 and the measuring unit 1 by approximately 200 km.

In the above description, the first to fourth optical fibers 31, 32, 33 and 34 are each provided with one first to fourth ring-shaped portions 27, 28, 29 and 30, Or more of the ring-shaped portion may be formed.

)는 0으로 하여 계산할 수 있다.In addition, although the above description has been described for three axes, it can also be applied to fewer than three axes. For example, if only the z-axis is present, the distance (X, Y,

) Can be calculated as zero.

Further, the ring-shaped portion of the optical fiber must have a predetermined self-elasticity so that the radius of curvature changes in accordance with the change in length of the elastic member. For example, the optical fiber disclosed in Utility Model Registration No. 20-0429342 "Intrusion Detection Optical Cable for Optical Network" May be used. In this case, a structure having an outer diameter of 3 mm surrounded by a Kevlar stiffener may be formed around the single mode optical fiber.

The optical fiber of the optical transmission unit may have a structure reinforced by a Kevlar reinforcement material, a steel wire, a polyurethane coating material, or the like depending on installation conditions and use environment.

As described above, the three-axis optical fiber acceleration measuring system according to the present invention can measure all the accelerations in three axial directions using one mass without using a guide accompanied by a frictional force, It is possible, and moreover, to make precise earthquake measurements. In addition, since the power supply to the sensing unit is not required and the configuration is simple, it is excellent in durability and can be operated remotely. Therefore, it can be used not only on the surface but also near the epicenter, It is expected to be able to monitor the earthquake early in about one minute because it can monitor more clearly.

    Also, the acceleration measurement system using the optical fiber of the present invention can be utilized for measuring three-axis displacement as well as three-axis acceleration. When the origin is fixed to one end of the object to be measured and the mass body 22 is fixed to the other end of the object to be measured in FIG. 2, three axes coordinates according to the displacement (5), (7) x, y, z) can be easily obtained.

The embodiments of the present invention described above are intended to facilitate understanding of the present invention, and the present invention is not limited to these embodiments. For example, the optical fiber acceleration measuring system of the present invention may be constructed in such a manner that the measuring unit measures the optical loss from the back scattering light generated in the sensing unit, and measures the difference between the amount of light incident on the sensing unit and the amount of light passing through the sensing unit It will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.

1:
11: Light source
12: I / F section
13:
14:
15:
16: Optical outlets
2:
22: mass
23, 24, 25, 26: first to fourth elastic members
27, 28, 29, 30: first to fourth ring-
3:
31, 32, 33, 34: first to fourth optical fibers
41, 42, 43, 44:
50: Case

Claims (6)

Mass;
An elastic member having one end fixed to the mass body and the other end connected to an object to be measured; And
And the optical fiber includes a ring-shaped portion as a portion of an optical fiber extending in parallel with the elastic member, one end connected to the object, and the other end connected to the mass. The acceleration measurement system according to claim 1, further comprising: an arithmetic unit for calculating a change amount of a radius using a change in a bending light loss generated when a radius of the ring-shaped portion is changed. The acceleration measurement system according to claim 2, wherein the calculation unit calculates a length change amount of the elastic member from the change amount of the radius and calculates an acceleration from the length change amount. The acceleration measurement system according to claim 2, wherein the calculation unit calculates a length change amount of the elastic member from the radius change amount, and calculates a displacement from the length change amount. Rectangular parallelepiped case;
A mass disposed within the case;
A first elastic member having one end connected to a first vertical edge of the case and the other end connected to the mass;
A second elastic member having one end connected to a second vertical edge of the case and the other end connected to the mass;
A third elastic member having one end connected to a third vertical edge symmetrical with the first vertical edge of the case and the other end connected to the mass;
A fourth elastic member having one end connected to an upper surface of the case and the other end connected to the mass; And
First to fourth optical fibers extending along the first to fourth elastic members, respectively, wherein one end is connected to the mass body, the other end is connected to the case, and the ring- To fourth optical fibers. The acceleration measurement system according to claim 5, further comprising a photodetector coupled to the first through fourth optical fibers for measuring a bending loss.

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