KR101059466B1 - Water level optical fiber displacement meter using optical fiber strain sensor and displacement measurement method of structure using same - Google Patents

Abstract

The present invention relates to a displacement meter using an optical fiber strain sensor configured to measure a vertical displacement of a structure by measuring a relative fluid level change according to a vertical position change of the water level change tank with respect to a plurality of water level change tanks.

According to the present invention, a water level displacement gauge (1) for measuring the amount of vertical displacement of the structure, including a plurality of water level change tank that changes the level of the fluid in accordance with the vertical displacement of the structure at the installation point, the plurality of water level change tank A reference point water level change tank S1 and general water level change tanks S2 and S3 placed at positions where the vertical displacement amount is to be measured; The optical fiber strain sensor 12 measuring the strain of the optical fiber 13 by measuring the change of light caused by the deformation of the cantilever member 11 and the optical fiber 13 in the water level change tanks S1, S2, and S3, respectively. A level gauge (10) comprising an optical fiber (13) having a) and a lifting member (14) which raises and lowers according to the fluid level change and causes the bending deformation in the cantilever member (11); When the fluid level inside the general water level change tanks S2 and S3 is changed by the vertical displacement, bending of the cantilever member 11 is caused by the elevating of the elevating member 14, and thus the optical fiber 13 The strain level of the optical fiber strain sensor 12 by measuring the level change amount of the level change tank (S2, S3) by measuring the vertical displacement amount of the structure is provided.

Description

Displacement Meter using Fiber Bragg Grating Sensor and Method for Estimating of Displacement with such Displacement Meter}

The present invention relates to a water level optical fiber displacement meter using an optical fiber strain sensor and a displacement measurement method of a structure using the same. More specifically, the relative fluid level change according to the vertical position change of the water level change tank for a plurality of water level change tanks. The present invention relates to a water level optical fiber displacement meter using a fiber strain sensor and a structure displacement measuring method using the fiber strain sensor configured to measure the vertical displacement of the structure by measuring the optical fiber strain sensor.

In structures such as bridge decks and girders, it is very important to accurately measure displacements. There are various types of displacement meters for measuring displacement, but such conventional displacement meters are not satisfactory in their accuracy.

On the other hand, with the development of optical fiber technology, an optical fiber strain sensor for measuring strain by measuring a change in light caused by the occurrence of deformation has been developed. An example of such an optical fiber strain sensor is a grating fiber strain sensor (Fiber Bragg Grating fiber) that accurately measures the strain by forming a grating on the optical fiber and measuring the change in refraction in the grating caused by the strain induced in the optical fiber. Sensor / also called "FBG sensor". Since the optical fiber strain sensor uses light, its measurement accuracy is known to be very high.

The present invention was developed to provide a displacement meter having a higher precision than a conventional displacement meter, and specifically, by using an optical fiber strain sensor having excellent strain measurement accuracy for displacement measurement of a structure such as a girder, the displacement of the structure can be accurately measured. An object of the present invention is to provide a level optical fiber displacement meter using an optical fiber strain sensor that can be measured, and a displacement measuring method of a structure using the same.

In the present invention, in order to achieve the above object, the optical fiber strain sensor is provided in each of the plurality of water level change tank, and by placing the optical fiber which causes tensile strain or compressive strain in the optical fiber by the rise or fall of the water level, After measuring the tensile strain or compression strain of the optical fiber according to the optical fiber strain sensor, the water level change is measured, and then the relative displacement amount at the installation position of the water level change tank is accurately measured using the water level change between the plurality of water level change tanks. There is provided a water level optical fiber displacement meter and a displacement measurement method of the structure using the same.

According to the present invention, since the optical fiber strain sensor having high measurement accuracy is used for measuring the displacement of the structure, the effect of improving the accuracy of the displacement measurement results is exerted.

In particular, since a plurality of optical fiber strain sensors are provided in one optical fiber, a plurality of optical fiber strain sensors can be used at the same time when measuring the strain due to the change in water level, thereby improving the accuracy.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The present invention has been described with reference to the embodiments shown in the drawings, which are described as one embodiment by which the technical spirit of the present invention and its core configuration and operation are not limited.

First, a configuration of a water level displacement meter 1 (hereinafter, abbreviated as "optical fiber displacement meter") using an optical fiber strain sensor according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

1 and 2 is a schematic view showing a state in which the optical fiber displacement meter (1) according to the invention consisting of a plurality of water level change tank is installed on the displacement measurement target structure, a beam simple beam form as an example of the displacement measurement target structure in the figure The water level change tank (reference point level change tank) installed at the point where displacement does not occur (both ends of the beam in the drawing) according to the installation position of the water level change tank is indicated as part number S1. The water level change tank placed at the point where the displacement is to be measured is denoted by the member numbers S2 and S3 in order from each point.

The optical fiber displacement meter 1 according to the present invention includes a plurality of level change tanks in which a fluid is contained and equipped with an optical fiber strain sensor for measuring a change in fluid level. As mentioned earlier in the brief description of Figures 1 and 2, the plurality of level change tanks, the reference point level change tank (S1) and the other displacement amount which is placed at the position where the reference point of the measurement does not occur according to the installation position Are divided into general level change tanks (S2, S3) placed at the position to be measured. However, the reference point level change tank (S1) and the general level change tanks (S2, S3) is merely a division by the installation position, the following description of the configuration is applied to all of the level change tank.

First, the principle of measuring the displacement amount of the optical fiber displacement meter 1 according to the present invention composed of a plurality of water level changing tanks will be described with reference to FIGS. 1 and 2 that illustrate simple beams. In the present invention, the plurality of level change tanks S1 and S2 contain fluids, and each of the level change tanks S1, S2 and S3 is in communication with each other by a communication tube. Therefore, if the plurality of water level changing tanks S1, S2, and S3 are all located at the same height, the fluid level in the water level changing tanks S1, S2, and S3 is the same based on the sea level. That is, for example, if the displacement measuring object structure is a simple horizontal beam as shown in Figure 1, the plurality of level change tanks (S1, S2, S3) placed on the simple beam are all the same fluid level therein. When the vertical displacement due to the bending deformation occurs in the simple beam, since the vertical displacement does not occur at the point as shown in FIG. 2, the position where the reference point level change tank S1 is not changed, but the remaining level change tank The position of S2 and S3 will change its vertical position as the vertical displacement is generated in the simple beam, and the fluid level inside the water level change tanks S2 and S3 will change accordingly. That is, since the fluid in each of the water level change tank (S1, S2, S3) is in communication with each other by the communication pipe, the fluid level inside the water level change tank (S2, S3) itself rises or falls due to the displacement of the structure. Will also change.

As such, when the vertical positions of the water level change tanks S2 and S3 change according to the displacement generated in the structure to be measured, the relative vertical displacement of the structure to be measured at the corresponding point can be known by measuring the amount of fluid level change. .

In the above, the plurality of level change tanks S1, S2, and S3 are all located at the same height, so that the fluid levels in the level change tanks S1, S2, and S3 are all the same, but the optical fiber displacement meter according to the present invention. In measuring the displacement with (1), it is not necessary to be in the above condition. That is, in the start stage, which is the previous stage at the time of measuring the displacement amount, the plurality of level change tanks S1, S2, and S3 are located at different heights so that the fluid level in the level change tanks S1, S2, and S3 is increased. It can be different. For example, the state shown in FIG. 2 may be a starting step, and subsequently the displacement amount may be measured for a state in which another form of bending deformation occurs. This is because, as described above, in the present invention, the relative vertical displacement amount of the structure at the corresponding position is measured based on the water level change amount in each of the water level change tanks S2 and S3.

In the present invention, the change in the internal water level in each of the level change tanks S1, S2, and S3 is measured by the level gauge 10 having the optical fiber strain sensor.

FIG. 3 is a schematic perspective view of an example of the cantilever member 11 included in the water level change tank and constituting the water level gauge 10 for measuring a change in water level therein, and FIGS. 4 and 5 respectively. It is a sectional view of the inside of a water level change tank showing the inside of the water level change tank with the measuring device 10 installed. FIG. 5 shows a state in which a bending deformation occurs in the cantilever member 11 because the fluid level is higher than that shown in FIG. 4. As shown in the figure, the water level gauge 10 according to the present invention includes a cantilever member 11 in which bending deformation occurs due to a water level change, and an optical fiber strain sensor 12 disposed on the cantilever member 11. The optical fiber 13 and the elevating member 14 which bends the cantilever member 11 according to the fluid level change and induces a bending deformation are comprised.

The cantilever member 11 is made of a rod member made of a material having elasticity such as synthetic resin, steel, etc., and one end thereof is integrally fixed to the water level changing tank so as to extend to face the fluid surface inside the water level changing tank.

The optical fiber 13 is provided with an optical fiber strain sensor 12 that measures the strain generated in the optical fiber by measuring the change of light caused by the deformation of the optical fiber 13. As an example of the optical fiber strain sensor 12 may use the above-described FBG sensor. The optical fiber 13 may be fixed to the cantilever member 11 so that the optical fiber strain sensor 12 is located on the upper surface of the cantilever member 11 as shown in the figure, the position of the optical fiber strain sensor 12 Is not limited thereto, and may be located on the bottom surface of the cantilever member 11. In particular, when the optical fiber strain sensor 12 is installed on both the upper and lower surfaces of the cantilever member 11, since the strain of the optical fiber 13 can be measured in duplicate, the reliability of the measured result is improved and the temperature is changed. Even if deformation is caused in the optical fiber 13, since the optical fiber strain sensor 12 is installed on both the upper and lower surfaces, the compensation for the deformation according to the temperature is made to maintain the high measurement accuracy of the optical fiber strain sensor 12 It has the advantage of being able to.

In addition, since the plurality of optical fiber strain sensors 12 may be disposed in a plurality of optical fibers 13, in the present invention, the optical fiber 13 having a plurality of optical fiber strain sensors 12 is provided to the cantilever member 11. By providing it, the effect which can raise a measurement accuracy through the multiple measurement of the strain by the some optical fiber strain sensor 12 is exhibited.

On the other hand, as shown in the figure, the cantilever member 11 preferably has a tapered shape that becomes narrower from the fixed end toward the free end. When the cantilever member 11 has a tapered shape in this manner, when the force in the direction perpendicular to the free end acts by the lifting and lowering of the elevating member 14, the load action point is concentrated on the small area of the free end, Due to the wide distribution of the load action point there is an advantage that can minimize the possibility that the torsion (torsion) can occur in the cantilever member (11). However, in the present invention, the shape of the cantilever member 11 is not necessarily limited to the above tapered shape.

The elevating member 14 moves up and down in the water level changing tank according to the fluid level, and when the fluid level rises, the lifting force is applied to the cantilever member 11 and when the fluid level falls, the descending force on the cantilever member 11 is lowered. It is a component that generates a bending deformation in the cantilever member 11 in accordance with the change in the fluid level. In the embodiment shown in the figure, the elevating member 14, buoy 141 floating in the fluid, one end is connected to the free end end to the cantilever member 11 and the other end is connected to the buoy 141. It is configured to include a pressing member 142 that is. Therefore, as the buoy 141 moves up and down by the change of the fluid level, the force member 142 moves to apply a force to the end of the cantilever member 11 to cause bending deformation in the cantilever member 11.

1 to 5, the cantilever member 11 is extended to face the water on the fluid level inside the water level change tank, so that the fluid level inside the water level change tank is increased accordingly. The buoy 141 also rises and the urging member 142 presses the cantilever member 11 to cause bending deformation. On the contrary, when the fluid level drops, the buoy 141 descends and the urging member 142 cantilever. The end of the member 11 is pulled down to cause bending deformation.

In the present invention, the force member 142 may be made of a rigid body such as a rod member, but may also be made of an elastic spring as illustrated in the drawings. In this case, if necessary, the guide member 143 surrounding the elastic spring may be further provided in the elevating member 14 to guide the elastic spring constituting the urging member 142 in a vertical motion. In the drawing, member number 144 is an installation frame 144 installed inside the water level change tank to fix the guide member 143. When the force member 142 is made of a rigid body, the length of the cantilever member 11 must be long to measure a relatively large displacement amount occurring in the structure. However, when the force member 142 is composed of an elastic spring as described above, even if the water level change is large due to a relatively large displacement amount occurs in the structure, the amount of displacement transmitted to the cantilever member 11 is thereby reduced by the elastic spring. For example, the cantilever member 11 having a relatively small length may be used. That is, the effect of being able to measure a large displacement amount of the structure by using the cantilever member 11 having a relatively small length is exerted. When the cantilever member 11 having a small length is used as described above, the size of the water level change tank can also be reduced, thereby reducing the size of the displacement gauge 1 as a whole.

Next, when the force member 142 is made of an elastic spring, a specific configuration of the displacement measuring method according to the present invention for measuring the displacement of the structure by measuring the fluid level change will be described in more detail with reference to FIGS. 4 and 5. .

First, as shown in the embodiment shown in Figure 4, the elastic spring is disposed as a force member 142 in the guide member 143 (in the embodiment shown in the drawing is made of a cylindrical shape) fixed to the installation frame 144, One end of the elastic spring is connected to the free end of the cantilever member 11 and the other end is provided with a lifting member 14 so as to be connected to the buoy 141 floating on the fluid and the fixed end of the cantilever member 11 is changed in water level Make it fixed to the tank.

When the water level change tank is located in the water level change tank corresponding to the general water level change tanks S2 and S3 as shown in FIG. 1 and the downward displacement occurs in the structure as shown in FIG. As can be seen, the fluid level inside the level change tank is raised. As a result, the urging member 142 made of an elastic spring exerts a lifting force on the free end of the cantilever member 11, thereby causing the cantilever member 11 to bend deformation due to the positive moment. On the contrary, when an upward displacement occurs in the structure and the fluid level is lowered, the buoy 141 descends and the force member 142 pulls the end of the cantilever member 11 downward in a certain range, thereby causing the parent to the cantilever member 11. Will cause bending deformation.

This bending deformation of the cantilever member 11 becomes a deformation of the optical fiber 13 disposed on the cantilever member 11, and as a result, by measuring the amount of deformation induced in the optical fiber 13 by the optical fiber strain sensor 12, The fluid level change in the level change tank is measured. Since the fluid level change in the water level change tank is caused by the displacement generated in the structure at the corresponding water level change tank installation position, the measured fluid level change in the water level change tank is installed at the level change tank installation position. The displacement amount of the structure can be known.

Meanwhile, in the above-described embodiment of the present invention, the cantilever member 11 and the force member 142 are installed on the surface of the fluid, but the cantilever member 11 and the force member 142 are locked below the surface of the fluid. It may also be configured to.

6 and 7 are cross-sectional views of the inside of the level change tank showing the inside of the level change tank for the embodiment of the present invention, wherein the cantilever member 11 and the force member 142 are submerged below the surface of the fluid, respectively. In the embodiment shown in Figs. 6 and 7, the cantilever member 11 whose one end is integrally fixed to the water level changing tank and extending into the water level changing tank is immersed in water. The buoy 141 is floating on the surface of the water, and an elastic spring is connected to the buoy 141 and the free end of the cantilever member 11 as the force member 142.

Other configuration and operation of this embodiment is the same as the embodiment of Figures 4 and 5 described above, for example, as shown in Figure 7 the downward displacement occurs in the structure as shown in Figure 7 the water level change tank When the fluid level increases, the urging member 142 made of an elastic spring exerts a lifting force on the free end of the cantilever member 11, and thus the cantilever member 11 causes bending deformation due to a positive moment. Deformation of the optical fiber 13, measurement by the optical fiber strain sensor 12 of the deformation amount of the optical fiber 13, measurement of the fluid level change in the water level change tank and the measurement of the structure displacement amount are made. On the contrary, when an upward displacement occurs in the structure and the fluid level is lowered, the buoy 141 is lowered, and the force member 142 pushes the end of the cantilever member 11 downward in a certain range so that the cantilever member 11 is moved to its parent. Cause bending deformation. 6 and 7, the installation frame 144 and the guide member 143 are provided in the same manner as the above-described embodiment.

As described above, in the present invention, the fluid level change in the level change tank is measured by using the optical fiber strain sensor 12 with high precision, and based on this, the displacement amount of the structure at the installation position of the level change tank is measured. The effect of the high reliability of the displaced amount is exerted.

The displacement meter 1 according to the present invention having such a configuration can be very useful for the vertical degree management or the camber management of the bridge during the construction of the main tower of the long bridge, for example, a plurality of general level change tanks inside the box of the box girder bridge. By arranging (S2, S3) in the axial direction at intervals and placing the reference water level change tank (S1) at the pier position, it is possible to easily and accurately measure the displacement on the box girder bridge by the principle described above.

1 and 2 are examples of the displacement measuring method according to the present invention, each of which is a schematic diagram showing a state in which the optical fiber displacement meter according to the present invention consisting of a plurality of water level change tank is installed on the displacement measuring structure according to the measuring method of the present invention.

3 is a schematic perspective view of an example of a cantilever member which is provided inside the level change tank in the displacement meter according to the present invention and constitutes a level gauge for measuring a level change therein.

4 and 5 are cross-sectional views of the inside of the water level change tank showing the inside of the water level change tank with the level gauge installed in the displacement meter according to the present invention, respectively.

6 and 7 are cross-sectional views of the inside of the level change tank showing the inside of the water level change tank with the level gauge installed in the displacement meter according to another embodiment of the present invention, respectively.

<Explanation of symbols for the main parts of the drawings>

1: displacement meter

11: cantilever member

12: fiber strain sensor

13: optical fiber

Claims (9)

A water level displacement gauge (1) for measuring the amount of vertical displacement of a structure, And a plurality of level change tanks containing fluid and communicating fluids to communicate with each other by a communication tube and varying the level of the fluid according to the vertical displacement of the structure at the installation point. , According to the installation position in the structure to be measured, the reference point level change tank (S1) placed at the position of the reference point of measurement without displacement occurs, and the general level change tank (S2,) placed at the position where the vertical displacement is to be measured. S3); Each of the level change tanks S1, S2, and S3 has one end portion integrally fixed to the level change tank and extends into the water level change tank, and the cantilever member 11 is disposed on the cantilever member 11 and has an optical fiber ( The optical fiber 13 having the optical fiber strain sensor 12 measuring the strain of the optical fiber 13 by measuring the change of light caused by the deformation of the optical fiber 13, and the cantilever member 11 by raising and lowering according to the change of the fluid level. Is provided with a water level measuring device 10 including a lifting member 14 for causing a bending deformation; When the fluid level inside the general water level change tanks S2 and S3 is changed by the vertical displacement generated in the structure, the bending deformation of the cantilever member 11 is caused by the elevating of the elevating member 14. Deformation occurs in the optical fiber 13, and by measuring the amount of deformation of the optical fiber 13 by the optical fiber strain sensor 12, the amount of change in the level of the water level change tank (S2, S3) to measure the vertical displacement of the structure at the corresponding position Water level optical fiber displacement meter, characterized in that for measuring. The method of claim 1, Cantilever member 11 is installed on the fluid surface, The elevating member 14 includes a buoy 141 floating in the fluid, and an urging member 142 having one end connected to a free end of the cantilever member 11 and the other end connected to the buoy 141. Composed by The buoy 141 is raised and lowered in accordance with the change in the fluid level inside the water level change tank, so that the force member 142 presses the cantilever member 11 to cause bending deformation. The method of claim 1, Cantilever member 11 is installed in a state submerged in the fluid, The elevating member 14 includes a buoy 141 floating in the fluid, and an urging member 142 having one end connected to a free end of the cantilever member 11 and the other end connected to the buoy 141. Composed by The buoy 141 is raised and lowered in accordance with the change in the fluid level inside the water level change tank, so that the force member 142 presses the cantilever member 11 to cause bending deformation. The method according to any one of claims 1 to 3, The optical fiber strain sensor 12 is provided on both the upper surface and the lower surface of the cantilever member (11). The method according to claim 2 or 3, In the elevating member (14), the force member (142) is a water level optical fiber displacement meter, characterized in that made of an elastic spring. The method of claim 5, The elevating member 14 is further provided with a elevating member 14, the guide member 143 surrounding the elastic spring to guide the elastic spring constituting the elastic member 142 in the vertical movement when it is stretched. A water level optical fiber displacement meter. The method according to any one of claims 1 to 3, The cantilever member (11) has a tapered shape, the width of which narrows toward the free end from the fixed end portion, characterized in that the optical fiber displacement meter. As a method of measuring the amount of vertical displacement of a structure, A plurality of level change tanks containing fluid and communicating fluids to communicate with each other by a communication tube, and varying in the level of the fluid depending on the vertical displacement of the structure at the installation point. The cantilever member 11, whose one end is integrally fixed to the water level changing tank and extends into the water level changing tank, is disposed on the cantilever member 11 and changes the light caused by the deformation of the optical fiber 13. The optical fiber 13 having the optical fiber strain sensor 12 measuring the strain of the optical fiber 13 and the elevating member 14 which raises and lowers according to the fluid level change and causes the bending deformation to the cantilever member 11. Measuring the displacement of the structure using an optical fiber displacement meter having a structure having a level gauge 10 configured to include; The plurality of water level change tanks are divided into reference point level change tanks S1 and general water level change tanks S2 and S3, so that the vertical displacement of the structure does not occur, so that the reference point level change tanks are located at the reference point of measurement. S1) is disposed, and general water level change tanks S2 and S3 are disposed at the position where the vertical displacement amount is to be measured;  When the fluid level inside the general level change tanks S2 and S3 is changed by the vertical displacement generated in the structure, the bending deformation is caused to the cantilever member 11 by the elevating of the elevating member 14. As a result, deformation occurs in the optical fiber 13, and by measuring the amount of deformation of the optical fiber 13 by the optical fiber strain sensor 12, the amount of change in the level of the water level change tanks S2 and S3 is measured and the structure perpendicular to the corresponding position. Displacement measurement method of a structure using an optical fiber displacement meter, characterized in that for measuring the displacement amount. The method of claim 8, In the optical fiber displacement meter, the elevating member 14, buoy 141 floating in the fluid, one end is connected to the free end of the cantilever member 11, the other end is the force connected to the buoy 141. It is configured to include a member 142, buoy 141 is raised and lowered in accordance with the fluid level change in the water level change tank inside the water level change tank, the force member 142 presses the cantilever member 11 to cause bending deformation. Displacement measurement method of a structure using an optical fiber displacement meter.

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