JP2016217852A - Displacement measuring system and displacement measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement measuring system having high durability and reliability and also having a temperature compensation function whose production cost is low.SOLUTION: A displacement measuring system includes: a cantilevered strain body 12 whose one is fixed and other end is displaced by a measuring object O; two sensors FBG 13a, 13b; and a measuring device 14 which calculates a displacement amount of the strain body 12 based on a difference between change amounts of reflection wavelengths of FBG sensors 13a, 13b. FBG sensors 13a, 13b are annexed to positions different in a strain amount when the same temperature is recognized and the other end is displaced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a displacement measuring system including a fiber Bragg grating (hereinafter referred to as “FBG”) sensor and having a temperature compensation function.

  Conventionally, an FBG sensor is attached to a strain body formed in a cantilever shape in which one end is fixed and the other end is displaceable, and the amount of change in the reflected wavelength of the FBG when the strain body is distorted is measured. There is known a displacement measurement technique for calculating a strain amount of a strain generating body, and thus a displacement amount of a measurement object that is displaced in conjunction with a free end of the strain generating body (see, for example, Patent Documents 1 and 2).

  Here, the FBG sensor refers to an optical transmission component in which a core portion of an optical fiber is formed such that a refractive index periodically changes in the optical fiber axial direction. The FBG sensor has a function of reflecting light having a specific wavelength called a Bragg wavelength when a light wave propagates through an optical fiber. The Bragg wavelength of the FBG sensor has a property of changing according to a physical quantity such as a distortion amount or a temperature change amount of the FBG sensor. Therefore, the FBG sensor can be used as a strain detection element or a temperature detection element.

  The techniques described in Patent Documents 1 and 2 convert a change in reflection wavelength due to strain generated by tension acting on the FBG sensor into a physical quantity, and cancel the reflected wavelength change due to temperature in the conversion. Temperature compensation.

  Moreover, the technique described in Patent Document 2 realizes a temperature compensation function by holding both ends of the FBG sensor with a pair of bimetal members whose bending changes according to a temperature change.

JP 2005-147802 A JP 2003-287435 A

  However, since the conventional displacement measurement methods disclosed in Patent Documents 1 and 2 are a type in which tension is directly applied to the FBG sensor element wire, when the measurement object is displaced, or when the measurement apparatus is adjusted or installed Sometimes an excessive force is easily applied to the FBG sensor. For this reason, the FBG sensor using the optical fiber is damaged, making measurement impossible or detecting accuracy being lowered, resulting in poor reliability.

  In the technique disclosed in Patent Document 2, the tension applied to the FBG sensor via the bimetal member must be suppressed from changing the reflection wavelength of the FBG sensor due to the temperature change. In addition, it takes a lot of time for adjustment, and there is a problem that the production cost becomes high.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a displacement measuring system having a temperature compensation function that has high durability and reliability, is relatively easy to produce, and has low production costs. .

  The displacement measuring system according to the present invention is a strained body formed in a cantilever shape in which one end is fixed and the other end is displaceable, and the strain when the other end is displaced while the temperature is recognized as the same in the strained body. A plurality of FBG sensors attached to a plurality of positions having different amounts, and a measuring device that calculates a displacement amount of the other end based on a difference in a change amount of a reflection wavelength of the plurality of FBG sensors when the other end is displaced; It is characterized by having.

  According to the present invention, the FBG sensors are arranged at a plurality of positions where the temperature is recognized to be the same and the strain amounts are different in the strain generating body, and the displacement of the other end of the strain generating body that can be displaced based on the reflection wavelength of each FBG sensor. Since only the amount is calculated, the calculated displacement amount does not depend on the temperature change. Therefore, the displacement measurement system has a temperature compensation function that can avoid the influence of temperature changes. In addition, the case where the temperatures are recognized to be the same includes not only the case where the temperatures are completely the same but also the case where the temperature difference is small enough to be ignored.

  Further, since the FBG sensor is attached to the strain generating body and integrated with the strain generating body, even when the measurement object is displaced, only the FBG sensor is not distorted (that is, FBG). Since no tension is directly applied to the sensor), an excessive force is not easily applied to the FBG sensor, and damage is unlikely to occur.

  Therefore, it is possible to obtain a displacement measuring system having a temperature compensation function with high durability and reliability and low production cost.

  In the displacement measurement system of the present invention, the strain amount of the strain generating body at the position where the predetermined FBG sensor is attached when the other end is displaced and the strain amount of the strain body at the position where another FBG sensor is attached. The ratio is preferably determined in advance.

  Thus, if the ratio of the amount of strain detected by each of the plurality of FBGs is determined in advance by changing the shape, material, etc. of the strain generating body, the calculation process will not be complicated and simpler and more reliable. It can be set as a highly reliable system.

  In the displacement measurement system of the present invention, the plurality of FBG sensors are attached to the strain body along a direction from one end to the other end, and the strain body is at least a plurality when the other end is displaced. It is preferable to bend so that the curvature in the direction from one end to the other end is constant at the position where each of the FBG sensors is attached.

  Thus, if the strain generating body is configured to bend with a constant curvature in the direction of the FBG, a system with high accuracy and reliability can be obtained without impairing the sharpness of the reflected wavelength of the FBG.

  Moreover, in the displacement measuring system of this invention, it is preferable that the strain body has the groove part provided so that the FBG sensor could be accommodated.

  If such a groove portion is provided, the arrangement position of the FBG can be easily determined, and since the adhesion area can be increased, the manufacturing becomes easy, and thus the production cost is reduced. The FBG can be firmly attached to the strain generating body.

  Further, in the displacement measurement system of the present invention, the plurality of FBG sensors are opposed to each other with the strain body interposed therebetween when viewed from the direction intersecting the direction in which the other end is displaced (for example, plate-shaped strain body). May be attached to the opposite positions of the front and back surfaces.

The schematic diagram which shows the structure of the displacement measuring system which concerns on embodiment of this invention. 2A and 2B are schematic views showing shapes of the strain generating body and the FBG sensor in FIG. 1, FIG. 2A is a plan view, FIG. 2B is a side view in a state where the free end of the strain generating body is not displaced, and FIG. FIG. 2D is a sectional view taken along the line II of FIG. 2A of the strain generating body. FIG. 3A is a schematic view showing a shape of a strain generating body according to a first modification, FIG. 3A is a plan view, and FIG. 3B is a side view in a state where a free end of the strain generating body is not displaced. FIG. 4A is a schematic view showing a shape of a strain generating body according to a second modified example, FIG. 4A is a plan view, and FIG. 4B is a side view in a state where a free end of the strain generating body is not displaced. The graph which shows the relationship between the change of the reflective wavelength of the FBG sensor in the modification shown in FIG. 3, and temperature.

  Hereinafter, a displacement measurement system 1 according to an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of the displacement measurement system 1 will be described.

  As shown in FIG. 1, the displacement measuring system 1 includes a base 11, a cantilever-like strain generating body 12 fixed to the base 11, and a first FBG sensor 13 a and a second FBG attached to the strain generating body 12. A sensor 13b, a measuring device 14 for measuring the reflection wavelength of the first FBG sensor 13a and the second FBG sensor 13b, an optical fiber 15 for connecting the first FBG sensor 13a, the second FBG sensor 13b and the measuring device 14, and an optical fiber 15 A refractive index matching gel 16 connected to the end opposite to the end of the measuring device 14 is provided.

  The initial reflection wavelength of the first FBG sensor 13a is different from the initial reflection wavelength of the second FBG sensor 13b.

  The measurement device 14 includes a wide band light source 14a that emits light of a predetermined band to the first FBG sensor 13a and the second FBG sensor 13b, and light reflected from the first FBG sensor 13a and the second FBG sensor 13b via the optical fiber 15. And a calculation unit 14c for calculating the strain amount of the strain generating body 12 from the wavelength of the light measured by the optical spectrum meter 14b.

  As shown in FIGS. 2A to 2C, the strain body 12 is a plate-like elastic member formed of a material having high thermal conductivity (for example, beryllium copper). One end portion 12 a of the strain body 12 is a fixed end fixed to the base 11. The other end 12b of the strain body 12 is a free end that is displaced when a load is applied to the action point P from the measurement object O.

  Further, as shown in FIG. 2A, the strain body 12 includes a first region A1 on the side of one end 12a to which the first FBG sensor 13a is attached and a second side on the side of the other end 12b to which the second FBG sensor 13b is attached. It is divided into area A2.

  Both side edges of the first region A1 have a base length of b in the planar shape and coincide with the base side of an isosceles triangle having the action point P as a vertex. The two side edges of the second region A2 have a planar shape with a base length of 2b and coincide with the apex side of an isosceles triangle having the action point P as the apex. That is, the planar shape of the strain body 12 is a shape in which both side edges on the base side of an isosceles triangle having a base length of 2b are cut off.

  The direction of the first FBG sensor 13a attached to the first area A1 and the direction of the second FBG sensor 13b attached to the second area A2 are directions along the direction from the one end portion 12a to the other end portion 12b.

  As shown in FIG. 2C, the first area A1 and the second area A2 are located at the positions where the first FBG sensor 13a and the second FBG sensor 13b are attached, respectively. In a direction toward the end portion 12b (that is, a direction coinciding with the directions of the first FBG sensor 13a and the second FBG sensor 13b), the curvature is made constant in each region.

  In the present embodiment, the ratio between the plate width of the first region A1 and the plate width of the second region A2 in the planar shape of the strain body 12 (see FIG. 2A) can be approximated to 1: 2.

Here, explaining the relationship between the curvature kappa ₂ in the plate width _{b 2} a curvature kappa ₁ and the second region A2 of the first region A1 of the plate width _{b 1} and the second region A2 of the first region A1 of the strain body 12 To do.

In general, the curvature κ is expressed by the following equation, where x is the distance from any point of interest to the point where the load is applied, M (x) is the bending moment, E is the Young's modulus, and I is the secondary moment of section. Can do.

The cross-sectional secondary moment I can be expressed by the following equation when the plate width of the strain body 12 is b (x) and the plate thickness is h.

Bending moment M (x), the Young's modulus E, since the thickness h is the same in the first region A1 and second region A2, a plate width _{b 2} of the plate width _{b 1} and the second region A2 of the first region A1 the relationship between the curvature kappa ₂ curvatures kappa ₁ and the second region A2 of the first region A1 may be expressed by the following equation.

  That is, since the plate width b (x) and the curvature κ in the first region A1 and the second region A2 of the strain body 12 are inversely proportional to each other, in the present embodiment, when the other end portion 12b is displaced. The ratio between the curvature of the first region A1 and the curvature of the second region A2 can be approximated to 2: 1.

The relationship between the elastic strain amount epsilon ^e and the curvature κ of the strain body surface can be expressed by the following equation.

That is, the elastic strain amount ε ^e is proportional to the curvature κ. Since the curvature κ is inversely proportional to the plate width b (x) as described above, the elastic strain amount ε ^e is also inversely proportional to the plate width b (x).

  Thus, the ratio between the amount of elastic strain generated in the first region A1 and the amount of elastic strain generated in the second region A2 when the other end portion 12b is displaced is predetermined so as to be a predetermined ratio. This ratio can be arbitrarily determined by changing the shape of the strain body 12.

  Since the first region A1 and the second region A2 exist at positions sufficiently close to each other, the temperature does not change greatly between these regions. That is, the first FBG sensor 13a attached to the first area A1 and the second FBG sensor 13b attached to the second area A2 are attached at positions where the temperatures are recognized to be the same. In addition, the case where the temperatures are recognized to be the same includes not only the case where the temperatures are completely the same but also the case where the temperature difference is small enough to be ignored.

  2D, which is a cross-sectional view taken along the line I-I of FIG. 2A, a groove 12c that can accommodate the second FBG sensor 13b is provided at the position where the second FBG sensor 13b of the strain generating body 12 is attached. Is formed. The second FBG sensor 13b is fixed with the adhesive 17 after being disposed in the groove 12c. A similar groove 12c is also formed at the position where the first FBG sensor 13a of the strain generating body 12 is attached. Since such a groove 12c is provided in the strain body 12, the arrangement positions of the first FBG sensor 13a and the second FBG sensor 13b can be easily determined, and the bonding area can be increased. Thereby, manufacture becomes easy, and while reducing production cost, the 1st FBG sensor 13a and the 2nd FBG sensor 13b can be attached to the distortion body 12 firmly.

  Next, a method in which the measurement device 14 of the displacement amount measurement system 1 calculates the displacement amount of the measurement object O (that is, the displacement amount of the other end portion 12b) in the calculation unit 14c will be described.

When the other end portion 12b of the strain generating body 12 is displaced (that is, when the measuring object O is displaced), the elastic strain amount (strain amount of the first FBG sensor 13a) in the first region A1 is represented by ε ^e ₁ , second When the elastic strain amount in the region A2 (the strain amount of the second FBG sensor 13b) is ε ^e ₂ , the strain amount ratio fr can be expressed by the following equation (1).

Elastic strain amount epsilon ^{e 1} of the first area _A1, the ratio fr of elastic strain amount epsilon ^e ₂ and their amount of strain in the second region A2 may be arbitrarily determined by the shape of the strain body 12. For example, the strain body 12 of the present embodiment is made of beryllium copper and has the shape shown in FIG. 2 (specifically, the curvature of the first region A1 when the other end portion 12b is displaced and the second Therefore, the ratio fr of elastic strain amounts ε ^e ₁ and ε ^e ₂ proportional to the curvature is set as follows.

In addition, for example, when the first FBG sensor 13a and the second FBG sensor 13b are provided at positions facing each other with the strain generating body 12 therebetween as viewed from the side (direction intersecting the direction in which the other end 12b is displaced) (specifically, is the strain body 18 of the first modification shown in FIG. 3, or in the case of the strain body 19 of the second modification shown in FIG. 4), the ratio f _r can be set as follows.

Generally, when the other end portion 12b of the strain body 12 is displaced, the strain body 12 is bent. At this time, the first FBG sensor 13a and the second FBG sensor 13b attached to the strain body 12 together with the strain body 12 are also curved. Here, the amount of change in the reflected wavelength of the first FBG sensor 13a when the other end portion 12b is displaced under a constant temperature condition is Δλ _B1 (δ _s ), and the amount of change in the reflected wavelength of the second FBG sensor 13b is If Δλ _B2 (δ _s ), the displacement amount δ _s of the other end portion 12b can be expressed by the following equation (2).

Here, generally, the relationship represented by the following equation (3) is established between the elastic strain amount ε ^e and the change amount Δλ _B of the reflection wavelength of the FBG sensor.

^{K e} in Formula (3), in a predetermined wavelength range it can be regarded as almost constant (for example, when the wavelength is 1550nm vicinity ^k e = 1.2 pm per epsilon ^e = 1 [mu] strain).

Therefore, the strain amount ε ^e _{1 of} the first FBG sensor 13a, the strain amount ε ^e _{2 of} the second FBG sensor 13b, the change amount Δλ _B1 (δ _s ) of the reflection wavelength of the first FBG sensor 13a, and the change of the reflection wavelength of the second FBG sensor 13b. The relationship represented by the following equation (4) is established between the amount Δλ _B2 (δ _s ).

Equation (2), between the two coefficients _{K f1} and _{K f2} and the ratio _{f r} obtained from (4), the relationship is established as indicated by the following equation (5).

From the equation (5), the change amount Δλ _B1 (δ _s ) of the reflection wavelength of the first FBG sensor 13a and the change amount Δλ _B2 (δ _s ) of the reflection wavelength of the second FBG sensor 13b when the other end 12b is displaced, as an expression indicating the relationship between the ratio of these f _r, the following equation (6) is obtained.

By the way, the reflection wavelengths of the first FBG sensor 13a and the second FBG sensor 13b are affected by a change in temperature. Therefore, if the amount of change in the reflected wavelength of the first FBG sensor 13a when the temperature changes by ΔT is Δλ _B1 (ΔT) and the amount of change in the reflected wavelength of the second FBG sensor 13b is Δλ _B2 (ΔT), the strain generating body The change amounts Δλ ^T _B1 and Δλ ^T _B2 of the reflection wavelengths of the first FBG sensor 13a and the second FBG sensor 13b when the other end 12b of the twelve 12 is displaced and the temperature changes are expressed by the following equations (7) and (8). Can be represented.

Here, the 1st FBG sensor 13a and the 2nd FBG sensor 13b which were attached to the strain body 12 of this embodiment are attached to the position where temperature is recognized as the same. Therefore, the change amount Δλ _B1 (ΔT) of the reflection wavelength of the first FBG sensor 13a and the change amount Δλ _B2 (ΔT) of the reflection wavelength of the second FBG sensor 13b when the temperature changes are the same change amount Δλ (ΔT). Can be considered. Therefore, the equations (7) and (8) become the following equations (9) and (10).

From the equations (6), (9) and (10), the following equation (11) can be obtained.

In the strain body 18 shown in FIG. 3, the relationship between the change amounts Δλ ^T _B1 and Δλ ^T _B2 of the reflected wavelengths of the first FBG sensor 13a and the second FBG sensor 13b when the temperature changes and the change amount of the temperature are as follows: For example, it is shown in the graph of FIG. In this graph, the reference point is a state where δ = 0 and T = 20 ° C., and each line in the graph indicates a state where the P point is pushed down by about 1 mm (a state where δ _s = 1 mm). Δλ ^T = 1 nm corresponds to ε = 833 μ strain.

As is clear from this graph, the difference in the amount of change in the reflection wavelength of the first FBG sensor 13a and the second FBG sensor 13b (Δλ ^T _B1 −Δλ ^T _B2 ) when the temperature changes is constant regardless of the temperature. .

From the equations (2) and (11), the following equation (12) can be obtained as an equation representing the displacement δ _s of the other end 12b of the strain generating body 12.

In Expression (12), the elastic strain amount ratio f _r and the coefficient K _f1 are known values, and the reflection wavelength variations Δλ ^T _B1 and Δλ ^T _B2 are values obtained by measurement. Further, in the equation (12), there is a change amount Δλ _B1 (ΔT) of the reflection wavelength of the first FBG sensor 13a and a change amount Δλ _B2 (ΔT) of the reflection wavelength of the second FBG sensor 13b when the temperature changes. Absent.

That is, since Expression (12) is an expression that is not affected by the amount of change in the reflection wavelength of the first FBG sensor 13a and the second FBG sensor 13b when the temperature changes, the amount of change in the reflection wavelength Δλ ^T _B1 , Δλ ^T By measuring _B2 , it is possible to obtain the displacement amount δ _s (that is, the displacement amount of the measuring object O) of the other end 12b of the strain generating body 12 while performing temperature compensation.

In the present embodiment, the ratio fr between the amount of elastic strain in the first region A1 and the amount of elastic strain in the second region A2 is predetermined. The value of the ratio fr can be roughly determined by the design of the strain generating body 12, but an accurate value cannot be obtained unless it is based on an actual test. However, if the relationship between the displacement amount δ _s of the other end portion 12b of the strain body 12 and the reflection wavelength changes Δλ ^T _B1 and Δλ ^T _B2 is actually obtained (specifically, in the equation (12)) If K _f1 / (1-fr) is obtained), it is not always necessary in practice to know the exact value of the ratio fr.

In the displacement measurement system 1 of the present embodiment, the amount of change Δλ ^T _B1 , Δλ in the reflection wavelength of the first FBG sensor 13a and the second FBG sensor 13b when the temperature changes with the displacement of the other end 12b of the strain body 12. by measuring ^T _B2, it is possible to determine the amount of change in the reflection wavelength of the 1FBG sensor 13a and the 2FBG sensor 13b due to temperature [Delta] [lambda] ([Delta] T). That is, temperature measurement can be performed.

For example, when the first FBG sensor 13a and the second FBG sensor 13b are attached so as not to face each other with the strain generating body 12 sandwiched when viewed from the side surface (when f _r ≠ −1), the ratio f _r and the formula ( From 9) and (10), the following equation (13) can be obtained.

When the equation (13) is transformed, the following equation (14) can be obtained.

In the equation (14), the elastic strain amount ratio _fr is a known value, and the reflection wavelength changes Δλ ^T _B1 and Δλ ^T _B2 are values obtained by measurement. Further, Expression (14) does not depend on the displacement amount δ _s of the other end portion 12b. Therefore, by measuring the change amounts Δλ ^T _B1 and Δλ ^T _B2 of the reflection wavelength, the change amount Δλ (ΔT) of the reflection wavelength can be obtained. That is, temperature measurement can be performed.

Further, the following equation (15) is established between the temperature change amount ΔT and the reflection wavelength change amount Δλ (ΔT) of the FBG sensor.

Here, the coefficient k ^T, is a value determined by the material of the optical fiber and the strain body 12 to be used in the FBG sensor. Therefore, by previously obtained the coefficient k ^T, the measurement of the temperature change amount ΔT from the reference temperature may also be performed.

Further, when the first FBG sensor 13a and the second FBG sensor 13b are attached so as to be opposed to each other with the strain generating body viewed from the side (when f _r = −1, the first modification shown in FIG. 3). The following formula (16) can be obtained from the formulas (9) and (10).

Since f _r = −1, Expression (16) becomes the following Expression (17).

  When the equation (17) is transformed, the following equation (18) can be obtained.

In Expression (18), the reflection wavelength changes Δλ ^T _B1 and Δλ ^T _B2 are values obtained by measurement. Further, Expression (18) does not depend on the displacement amount δ _s of the other end portion 12b. Therefore, by measuring the change amounts Δλ ^T _B1 and Δλ ^T _B2 of the reflection wavelength, the change amount Δλ (ΔT) of the reflection wavelength can be obtained. Furthermore, the temperature change amount ΔT from the reference temperature can also be measured by using the equation (15).

  Although the illustrated embodiment has been described above, the present invention is not limited to such a form.

  For example, in the above embodiment, the first FBG sensor 13a is attached to the first region A1 on the one end 12a side of the strain body 12, and the second FBG sensor 13b is the second region on the other end 12b side of the strain body 12. It is attached to A2. However, three or more FBG sensors may be attached to the strain generating body. Further, the position where the FBG sensor is arranged may be a position where the detected distortion amount is different. For example, FBG sensors may be arranged one by one on the front and back of the strain body.

  Moreover, in the said embodiment, as shown to FIG. 2A, the planar shape of the strain body 12 is comprised so that it may become an isosceles triangle by which the outer edge of the area | region of the base side was notched, and one side of the strain body Two FBG sensors are arranged on the surface. However, the strain body is not limited to such a shape.

  For example, as in the strain body 18 of the first modification shown in FIG. 3, the planar shape in the vicinity of the one end 18a fixed to the base 11 is the shape on the base side of the isosceles triangle with the action point P as the apex. The planar shape in the vicinity of the other end portion 18b that is displaced when a load is applied to the action point P from the measuring object O is a shape in which the end portion is semicircular and extends from the base side of the isosceles triangle to the apex side, and FBG You may make it arrange | position the sensors 13a and 13b on the front and back of the strain body 18 one by one.

  Further, for example, like the strain body of the second modification shown in FIG. 4, the planar shape in the vicinity of the one end portion 19 a fixed to the base 11 is the shape on the base side of the isosceles triangle having the action point P as the apex. And the FBG sensors 13a and 13b are arranged on the front and back surfaces of the strain body 19 one by one, with the planar shape in the vicinity of the other end 19b that is displaced when a load is applied from the measuring object O to the action point P. You may make it do.

  Moreover, in the said embodiment, the groove part 12c is provided in the strain body 12, and the 1st FBG sensor 13a and the 2nd FBG sensor 13b are attached to the groove part 12c. However, the groove 12c may be omitted.

  Moreover, in the said embodiment, the planar shape of the strain body 12 is made into the shape which notched the outer edge of the base vicinity of an isosceles triangle. However, the shape of the strain body of the present invention is not limited to such a shape. For example, when it can be considered that the grating length of the FBG sensor is sufficiently small with respect to the length of the strain generating body, the planar shape may be a rectangle or a triangle without a notch.

  In the above embodiment, the direction of the first FBG sensor 13a and the second FBG sensor 13b and the direction in which the curvature of the strain generating body 12 changes are matched, and in that direction, the strain is generated when the other end 12b is displaced. The curvature of the body 12 is configured to be constant at the positions where the first FBG sensor 13a and the second FBG sensor 13b are arranged (in the above embodiment, the first region A1 and the second region A2). However, the orientation of the FBG sensor and the curvature at the time of bending of the strain body may be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 ... Displacement measuring system, 11 ... Base, 12, 18, 19 ... Strain body, 12a, 18a, 19a ... One end part, 12b, 18b, 19b ... Other end part, 12c ... Groove part, 13a ... 1st FBG sensor, 13b ... 2nd FBG sensor, 14 ... Measuring device, 14a ... Wide band light source, 14b ... Optical spectrum meter, 14c ... Calculation part 15 ... Optical fiber, 16 ... Refractive index matching gel, 17 ... Adhesive, A1 ... 1st area | region, A2 ... second region, O ... measurement object, P ... action point.

Claims (5)

A strain body formed in a cantilever shape in which one end is fixed and the other end is displaceable;
A plurality of FBG sensors attached to a plurality of positions having different strain amounts when the temperature is recognized to be the same in the strain generating body and the other end is displaced;
A displacement amount measuring system comprising: a measuring device that calculates a displacement amount of the other end based on a difference in a change amount of a reflection wavelength of the plurality of FBG sensors when the other end is displaced. . The displacement measurement system according to claim 1,
A ratio between a strain amount of the strain generating body at a position where the predetermined FBG sensor is attached when the other end is displaced and a strain amount of the strain generating body at a position where the other FBG sensor is attached is predetermined. Displacement measuring system characterized by being characterized. The displacement measurement system according to claim 1 or 2,
The plurality of FBG sensors are attached to the strain body along a direction from the one end to the other end,
When the other end is displaced, the strain body is curved so that a curvature in a direction from the one end to the other end is constant at a position where each of the plurality of FBG sensors is attached. A featured displacement measurement system. It is a displacement measuring system of any one of Claims 1-3,
The displacement body has a groove part provided so that the FBG sensor can be accommodated. It is a displacement measuring system of any one of Claims 1-4,
The displacement measuring system, wherein the plurality of FBG sensors are attached so as to face each other with the strain body as viewed from a direction crossing a direction in which the other end is displaced.