JP2004257932A - Optical fiber type displacement gauge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber type displacement gauge hardly affected by the external factors such as weather and high-voltage electrical power lines, having high durability, and capable of being monitored from a remote place. <P>SOLUTION: This optical fiber type displacement gauge comprises a plate member receiving the displacement in accordance with the displacement of a measured object, a cylinder mounted on the plate member at least when the measured object is not displaced, a displacement direction converting part for converting the displacement received by the plate member into the displacement in the direction perpendicular to the displacement, and moving the cylinder by the converted displacement, and an optical fiber positioned approximately in parallel with a face of the plate member when the measured object is not displaced, and is pressed from a circular side face part of the cylinder by the movement of the cylinder in accordance with the displacement to be curved, when the measured object is displaced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical fiber type displacement meter which is suitable for, for example, installing on a large civil engineering structure such as a bridge girder of a bridge and monitoring a state change, particularly a displacement, of the civil engineering structure due to seismic motion or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, state changes of large civil engineering structures have been monitored, for example, by patrol inspections by security personnel, electric displacement meters (for example, see Non-Patent Documents 1 to 3), and the like.
[0003]
[Non-patent document 1]
"Measurement equipment for civil engineering and construction, displacement meter", [online], Kyowa Dengyo Co., Ltd., [searched on February 25, 2003], Internet <URL: http: // www. kyowa-ei. co. jp / japanese / product / index_2002-10. htm>
[0004]
[Non-patent document 2]
"Displacement meter", [online], Tokyo Sokki Laboratory, [searched on February 25, 2003], Internet <URL: http: // www. tokyosoki. co. jp / product / transducer / displacement. html>
[0005]
[Non-Patent Document 3]
"Multi Displacement Meter", [online], Kowa Co., Ltd., [searched on February 25, 2003], Internet <URL: http: // www. kowa-net. co. jp / product / multi / multi. htm>
[0006]
[Problems to be solved by the invention]
Among the above-mentioned prior arts, the patrol inspection by security personnel lacks responsiveness and has a problem in safety.
[0007]
In addition, although the electric displacement meter has high accuracy, it has problems in that it is affected by lightning damage and the like, and requires durability and frequent maintenance.
[0008]
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an optical fiber type displacement which is hardly affected by external factors such as weather and high voltage electric wires, has excellent durability, and can be monitored remotely. To provide a total.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is an optical fiber type displacement meter that detects a displacement of a measurement target, and a plate-shaped member that receives a displacement following the displacement of the measurement target, When the object to be measured is not displaced, the cylinder placed on the plate member and the displacement received by the plate member are converted into a displacement in a direction orthogonal to the displacement, and the cylinder is moved according to the converted displacement. When the measurement object does not displace, the displacement direction conversion unit is substantially parallel to the surface of the plate-shaped member, while when the measurement object displaces, the cylinder moves in accordance with the displacement to move the cylindrical side surface. An optical fiber that is pressed from a portion and is bent is provided.
[0010]
According to the first aspect of the present invention, since the optical fiber is used as a displacement meter and a signal transmission path, it is possible to remotely monitor the optical fiber. Further, according to the present invention, since electric parts are not used for the displacement meter portion, it is not affected by the weather such as thunder or the induction as an external factor by the high voltage electric wire or the like, and the durability is excellent. .
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, the displacement direction conversion section is a substantially triangular prism-shaped inclined section that separates the cylinder from the plate-shaped member by contacting an annular side face of the cylinder, The inclined portion has a cutout which can enter the interior with the displacement of the plate member while accommodating the cylinder inside, and the moving direction of the cylinder is perpendicular to the displacement direction of the plate member. And a guide portion that can be restricted in the direction.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the accompanying drawings.
[0013]
FIG. 1 is an explanatory diagram showing a configuration of an optical fiber displacement meter according to one embodiment of the present invention. The optical fiber type displacement meter 1 shown in FIG. 1 detects the displacement of a measurement target by using the bending of the optical fiber 11. The measurement targets of the optical fiber type displacement meter 1 are, for example, displacements caused by earthquakes or secular changes of large civil engineering structures such as tunnels, bridges, dams, buildings, river embankments, port facilities, and grounds. And the collapse of snow and ice on the slopes of mountainous areas, but it is needless to say that the present invention is not necessarily limited thereto.
[0014]
The optical fiber type displacement meter 1 has a plate-like member 12 that moves by receiving a displacement following a displacement of a measurement target in which the optical fiber-type displacement meter 1 is installed, and a measurement target to assist the movement of the plate-like member 12. A plurality of rollers 16 fixedly arranged. When the object to be measured is not moving, a cylinder 15 is placed on the upper surface of the plate-shaped member 12, and the cylinder 15 has a side surface portion in the moving direction of the plate-shaped member 12 (the left-right direction in FIG. 1). Abut. The cylinder 15 is housed in a guide portion 13 for restraining the moving direction only in a direction (vertical direction in FIG. 1) orthogonal to the moving direction of the plate member 12, and the upper surface of the cylinder 15 has an initial state (plate The optical fiber 11 penetrates the guide portion 13 so that the optical fiber 11 contacts at one point in a state where the member 12 does not move).
[0015]
FIG. 2 is a side view when the guide portion 13 is viewed from the direction of arrow A in FIG. As shown in the figure, the guide portion 13 has a notch 131, and a substantially triangular prism-shaped pedestal is formed on the notch 131, and the side surface of the cylinder 15 rises obliquely on the slope of the pedestal. A slope 14, a possible ramp, is arranged. For this reason, the slope 14 is fixed to the plate-shaped member 12, and can enter the space inside the guide portion 13 from the notch 131 of the guide portion 13 with the movement of the plate-shaped member 12. The member 12 can be moved only in a direction perpendicular to the moving direction.
[0016]
Next, the operation of the optical fiber displacement meter 1 having the above configuration will be described with reference to the explanatory diagram of FIG. In the figure, for comparison, the state of the optical fiber type displacement meter 1 before and after the displacement of the measurement target is generated (FIG. 3A) and after the displacement is generated (FIG. 3B) are also shown above and below.
[0017]
As shown in FIG. 3A, in a state before the occurrence of displacement (initial state), the cylinder 15 is placed on the plate-shaped member 12 as described above, and is not in contact with the slope 14. The optical fiber 11 is substantially parallel to the surface of the plate member 12, and the bending loss generated in the optical fiber 11 is small or almost non-existent.
[0018]
Thereafter, the slope 14 also moves in accordance with the amount of displacement of the plate member 12 in the right direction in the drawing and enters the inside of the guide portion 13, whereby the cylinder 15 separates from the plate member 12 and When the cylinder 15 is moved upward (upward), the cylinder 15 presses the optical fiber 11 which is in contact with the annular side surface thereof, thereby bending the optical fiber 11. That is, the displacement of the plate-shaped member 12 is converted into the rise of the cylinder 15 housed in the guide portion 13 via the slope 14. Therefore, in the initial state shown in FIG. 3A, the optical fiber 11 that has been in straight contact with the uppermost end of the cylinder 15 receives bending stress, and as a result, the optical pulse incident on the optical fiber 11 is Bending loss will occur as described later. In this sense, the displacement direction converting unit that converts the displacement received by the plate member 12 into a displacement in a direction orthogonal to the displacement and moves the cylinder 15 in accordance with the converted displacement includes at least the guide unit 13 and the slope 14. It is composed of
[0019]
As described above, according to the present embodiment, when the plate member 12 is displaced, the amount of displacement can be detected by the bending loss generated in the optical fiber 11. Therefore, after the optical fiber type displacement meter 1 of the present embodiment is installed at the measurement target site, a bending loss measuring device for measuring the bending loss of the optical fiber 11 is connected to the optical fiber type displacement meter 1, and the initial position before the displacement is measured. From the difference from the state, the displacement amount of the measurement target part can be detected and converted.
[0020]
That is, according to the present embodiment, the physical quantity based on the position change (displacement) of the measurement target portion can be measured not electrically but based on the bending loss of the optical fiber 11 based on the position change. For example, it is less susceptible to weather changes such as lightning and external factors such as high-voltage wires, so that the measurement accuracy can be improved and the durability can be improved.
[0021]
Further, according to the present embodiment, it is possible to measure a physical quantity based on a change in load on a measurement target portion without using an electrical component, and thus it is possible to reduce the cost of the optical fiber displacement meter 1 itself. .
[0022]
As a result, it is possible to reduce the cost (initial installation cost) when the optical fiber displacement meter 1 is first installed for detecting a change in the position of the measurement target site and the maintenance cost involved in maintenance such as replacement. .
[0023]
Note that a substantially spherical object may be used instead of the cylinder 15 that ascends the guide portion 13. Needless to say, the length of the slope 14 is determined according to the allowable displacement amount of the measurement object.
[0024]
FIG. 4 is an explanatory diagram illustrating a schematic configuration of a displacement measurement system that measures displacement of a measurement target using a plurality of optical fiber displacement meters 1 according to the present embodiment. The displacement measuring system 100 shown in FIG. 1 uses a plurality of optical fiber displacement meters 1 to detect a bending loss generated in the optical fiber 11. In the following description, a plurality of optical fiber displacement meters are represented as 1-1, 1-2,..., 1-n (n is a positive integer of 2 or more).
[0025]
Each of the optical fiber displacement meters 1-1, 1-2,..., 1-n is connected in series via the same optical fiber 11, and each of them is installed at, for example, a site to be measured. I have. A more specific example will be described later with reference to FIG. The other components of the optical fiber type displacement meters 1-1, 1-2,..., 1-n are the same as those of the optical fiber type displacement meter 1 described with reference to FIG. The description is omitted.
[0026]
Also, the plurality of optical fiber type displacement meters 1-1,..., 1-n connected in series via the same optical fiber 11 are pulled out from the optical fiber type displacement meter 1-1 on one end side. The optical fiber 11 is connected to a bending loss measuring device 20 which measures the bending loss of the optical fiber 11, converts the bending loss into electrical loss data, and outputs the data. The bending loss measuring device 20 is communicably connected to a computer 30, which is an electronic computer such as a personal computer, via a communication network such as a LAN, a public line, or a dedicated line. The calculator 30 receives the loss data output from the bending loss measuring device 20, calculates a load change amount and a change position of the measurement target based on the received loss data, and sets a predetermined threshold based on the calculation result. The presence or absence of the corresponding position change is determined, and an alarm or the like is issued.
[0027]
Here, a schematic configuration of the bending loss measuring device 20 will be described with reference to FIG. The bending loss measuring device 20 shown in FIG. 4 is based on, for example, an OTDR (Optical-Fiber-Time Domain Reflectometer) method, and includes a light-emitting unit 21 that is a light source that outputs a light pulse P1 and a light-emitting unit 21 that is output from the light-emitting unit 21. The output light pulse P1 is output to the optical fiber 11, the backscattered light B1 returning to itself is branched, and a beam splitter 23 is output to a light receiving unit 22, which will be described later. 11, that is, the loss distribution due to the bending of the optical fiber 11 in the plurality of optical fiber displacement meters 1-1,..., 1-n, and the measured loss distribution is used as electrical loss data. And a light-receiving unit 22 that converts the data into a data and outputs it to the computer 30.
[0028]
Next, the operation of the entire displacement measurement system 100 will be described.
[0029]
An optical pulse P1 is transmitted from the bending loss measuring device 20 to the plurality of optical fiber displacement meters 1-1, 1-2,..., 1-n and is incident on the optical fiber 11.
[0030]
At this time, at least one optical fiber displacement meter 1-j (1 ≦ j ≦ n; j is an integer) among the plurality of optical fiber displacement meters 1-1, 1-2,..., 1-n. When a displacement occurs in the measurement target portion on which is installed, the optical fiber 11 which comes into contact with the cylinder 15-j of the optical fiber displacement meter 1-j, the slope 14 according to the displacement of the plate member 12-j. A bending stress is applied by the cylinder 15-j raised through -j, and as a result, bending occurs at a corresponding portion of the optical fiber 11 (hereinafter, this portion is referred to as a fiber portion). Here, "-j" is added to all the reference numerals of the components of the optical fiber type displacement meter 1-j.
[0031]
The light pulse P1 generates the backscattered light B1 while propagating through the optical fiber 11. In particular, bending loss due to bending occurs in the backscattered light from the fiber portion of the optical fiber 11 to which bending stress is applied. Therefore, if a displacement occurs somewhere in the measurement object, the bending loss of the optical fiber 11 accompanying the displacement becomes larger than in a normal state. The occurrence can be detected.
[0032]
The backscattered light B1 generated in this way propagates through the optical fiber 11 toward the light pulse P1 incident side, that is, toward the bending loss measuring device 20, and branches off via the beam splitter 23 to be received by the light receiving unit 22. Is done.
[0033]
The light receiving unit 22 generates electrical data corresponding to the bending loss distribution, that is, loss data including the generated bending loss, based on the incident backscattered light B1.
[0034]
The generated loss data is transmitted to the computer 30. The calculator 30 performs an analysis process based on the loss data, and calculates a position change (displacement) of the measurement target portion.
[0035]
Further, based on the calculated position change of the measurement target part, it is determined whether or not a position change has occurred according to a preset threshold value (for example, representing the maximum allowable displacement level of the measurement target). As a result, When it is determined that a position change exceeding the threshold has occurred, the computer 30 outputs an alarm.
[0036]
As described above, even when the displacement measurement system 100 is configured using a plurality of optical fiber displacement meters 1 shown in FIG. 1, for example, weather changes such as lightning, external factors such as high-voltage wires, etc. , Greatly improve the measurement accuracy, and further reduce the cost of the entire displacement measurement system 100 based on the cost reduction of each of the optical fiber displacement meters 1-1,..., 1-n. And the initial installation cost and the maintenance cost can be reduced.
[0037]
Such a displacement measurement system 100 is particularly suitable for measuring a large measurement target at a plurality of locations. That is, the optical fiber displacement meters 1-1,..., 1-n provided at the respective measurement sites and one bending loss measuring device 20 are wired in series using one optical fiber 11. Since it is not necessary to individually wire each of the optical fiber displacement meters 1-1,..., 1-n, the entire displacement measurement system 100 can be simplified.
[0038]
Further, no power supply is required for each of the optical fiber displacement meters 1-1,..., 1-n, so that the cost for the power supply is reduced, and maintenance such as power supply replacement is also unnecessary.
[0039]
As described above, since the optical fiber type displacement gauges 1-1,..., 1-n and the bending loss measuring device 20 can be wired only by the optical fiber 11, the bending loss measuring device 20 can be used. Is remotely arranged with respect to the optical fiber displacement meters 1-1,..., 1-n, and a change in the position of the measurement target site can be monitored on the remote side.
[0040]
The displacement measurement system 100 according to the present embodiment is installed, for example, at a connecting portion of a bridge girder in a bridge, and can be applied to a case where a moving state of the bridge girder is detected. FIG. 5 is a side view when the optical fiber type displacement meter 1 according to the present embodiment is attached to a connecting portion of a bridge girder. The two bridge girders 41 and 42 shown in the figure are connected with a pier 51 as a pedestal, and both bridge girders 41 and 42 are provided with a fall prevention device 61 connected thereto.
[0041]
For convenience, the reference numeral 1-j (1 ≦ j ≦ n; j is an integer) is given to the optical fiber type displacement meter installed on the side surface of the connecting portion, and the reference number of each part of the optical fiber type displacement meter 1-j. "-J" is additionally described. The right end of the plate member 12-j is fixedly attached to the bridge girder 42, and the rotating shaft of each roller 16 is also attached to the bridge girder 41 or 42. The guide part 13-j is also attached to the bridge girder 41. Accordingly, the plate member 12-j is also displaced rightward as the bridge girder 42 is displaced rightward in FIG. As a result, the cylinder 15 rises and bending loss occurs in the optical fiber 11, and the displacement of the bridge girder 42 can be detected.
[0042]
In the case shown in the figure, the displacement in the left direction cannot be dealt with, but this can be detected, for example, by providing the same optical fiber type displacement meter 1 on the opposite side of the figure (opposite the paper surface). I can do it.
[0043]
If the optical fiber type displacement meter 1-j is subjected to a treatment such as coating using a cover member as appropriate, the durability can be further increased.
[0044]
【The invention's effect】
As is clear from the above description, according to the present invention, there is provided an optical fiber type displacement meter which is hardly affected by external factors such as weather and high voltage wires, has excellent durability, and can be remotely monitored. be able to.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of an optical fiber displacement meter according to an embodiment of the present invention.
FIG. 2 is a side view showing a schematic configuration of a guide section in the direction of arrow A in FIG. 1;
FIG. 3 is an explanatory diagram showing a change of an optical fiber type displacement meter before and after displacement.
FIG. 4 is an explanatory diagram illustrating a schematic configuration of a displacement measurement system including a plurality of optical fiber displacement meters according to an embodiment of the present invention.
FIG. 5 is a side view of a connecting portion of a bridge showing one application example of the displacement measurement system shown in FIG. 4;
[Explanation of symbols]
, 1-n, 1-2,..., 1-n Optical fiber displacement meter 11 Optical fiber 12 Plate member 13 Guide part 14 Slope 15 Cylinder 16 Roller 20 Bending loss measuring instrument 21 Light emitting part 22 Beam splitter 23 Light receiving unit 20 Computer 41, 42 Bridge girder 51 Bridge pier 61 Falling prevention device 100 Displacement measurement system

Claims (2)

An optical fiber displacement meter that detects a displacement of a measurement object,
A plate-shaped member that receives a displacement following the displacement of the measurement target,
At least when the measurement object is not displaced, a cylinder placed on the plate-shaped member,
A displacement direction conversion unit that converts the displacement received by the plate-shaped member into a displacement in a direction orthogonal to the displacement, and moves the cylinder according to the converted displacement,
When the object to be measured is not displaced, while being substantially parallel to the surface of the plate-shaped member, when the object to be measured is displaced, it is pressed from the annular side surface of the cylinder by the movement of the cylinder in accordance with the displacement, and the bending is performed. An optical fiber type displacement meter comprising an optical fiber to be added. The displacement direction conversion unit,
A substantially triangular prism-shaped inclined portion that contacts the annular side surface portion of the cylinder and separates the cylinder from the plate-like member,
The inclined portion has a notch which can enter the interior with the displacement of the plate-shaped member while accommodating the cylinder inside, and the moving direction of the cylinder is orthogonal to the displacement direction of the plate-shaped member. 2. The optical fiber displacement meter according to claim 1, further comprising a guide portion that can be restrained in a direction.

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