KR20100130300A - The clinometer/accelerometer using optical fiber sensor - Google Patents

Abstract

PURPOSE: An inclinometer/accelerometer using an optical-fiber sensor is provided so that an electric signal is generated from a piezoelectric sensor and the signal is transferred to a measuring instrument and the force and the acceleration can be calculated from the signal. CONSTITUTION: An inclinometer/accelerometer using an optical-fiber sensor comprises a cantilever(110) and FBG sensors(120a, 120b). One end of the cantilever is fixed to a structure. The other end of the cantilever is connected to an inertia mass(100) and can be bent. The FBG sensors are parallelly arranged to be spaced from the cantilever. The FBG sensors are arranged on symmetric locations around the cantilever and are bent according to the bending degree of the cantilever. Both ends of the FBG sensor are fixed to the inertia mass and to the structure in a direction parallel to the cantilever.

Description

Inclinometer / accelerometer using optical fiber sensor {The clinometer / accelerometer using Optical fiber sensor}

The present invention relates to an inclinometer / accelerometer using an optical fiber sensor, and more particularly, to an inclinometer / accelerometer using an optical fiber that enables more stable and accurate measurement of the inclination and acceleration of a structure caused by an external force applied to the structure. .

Piezoelectric sensors are used as sensors to measure the degree of inclination and acceleration of the structure by mounting it on the structure.

1 is a diagram conceptually showing a piezoelectric accelerometer according to the prior art.

The piezoelectric inclinometer includes an inertial mass and a piezoelectric sensor as shown in FIG. The piezoelectric sensor 15 is composed of a piezoelectric body and metal electrodes at both ends of the piezoelectric body, and is attached to the object to be measured and disposed between the inertial mass 10 and the object to be measured.

The inertial mass 10 is placed on the upper surface of the object under test, and maintains a neutral position when the inclination of the object under test is zero. When the measured object is inclined to one side by an external force, the inertial mass 10 interferes with the movement of the measured object due to its own inertia and exerts an additional force on the piezoelectric sensor 15. The piezoelectric sensor 15 generates an electrical signal by the force, and the generated signal is transmitted to the measuring instrument 20 to calculate the force and the slope applied from the transmitted signal.

In addition, since the inertial mass 10 lies on the upper surface of the object to be measured, the neutral position is maintained while the object to be measured moves at a constant speed. When the speed of movement of the accelerometer changes, the inertial mass 10 mounted on the object under test impedes the movement of the accelerometer due to its own inertia and an additional force is applied to the piezoelectric sensor 15. The electric signal is generated in the piezoelectric sensor 15 by this force, and the generated signal is transmitted to the measuring instrument 20 to calculate the force and acceleration applied from the signal.

However, the piezoelectric inclinometer according to the related art, which is constructed and operated as described above, has insufficient durability of the piezoelectric sensor 15 itself. It can affect the structure itself.

In addition, there is a possibility that the interference of the electrical signal remains, and it is difficult to accurately measure the slope due to the influence of noise.

An object of the present invention is to provide an inclinometer / accelerometer using an optical fiber sensor that can significantly increase the accuracy and accuracy of the degree of inclination and acceleration measurement and has excellent durability.

An inclinometer / accelerometer using an optical fiber sensor according to an embodiment of the present invention includes a cantilever having one end fixed to a structure and the other end connected to an inertial mass and capable of bending deformation; And at least two FBG sensors spaced apart from the cantilever by a predetermined distance, disposed at symmetrical positions about the cantilever, and deformed according to the degree of deflection of the cantilever, wherein the length (l) of the cantilever and the The separation distance Δx between the cantilever and the FBG sensor satisfies the following equation.

The inclinometer / accelerometer using the optical fiber sensor according to the embodiment of the present invention configured as described above has the effect of measuring the precise deformation of a structure with excellent resolution without being affected by the external environment.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a schematic diagram showing the configuration of the inclinometer / accelerometer using an optical fiber sensor according to an embodiment of the present invention.

As shown in FIG. 2, the inclinometer / accelerometer using the optical fiber sensor according to an embodiment of the present invention uses the inertial mass 100, the cantilever 110, the optical fiber sensors 120a and 120b, and the optical measuring means 150. It is configured to include.

The optical fiber sensors 120a and 120b according to the embodiment of the present invention include an optical fiber grating (FBG), and the optical fiber grating has a wavelength having a predetermined width satisfying the Bragg condition with respect to the incident wavelength. It reflects only and transmits other wavelengths as they are.

The cantilever 110 is connected to the structure 50 and the inertial mass 100 to measure the inclination, respectively, to fix the inertial mass 100, and to warp deformation according to the inclination of the structure 50 and the movement of the inertial mass 100. And so on.

The cantilever 110 is preferably composed of a rigid material having elasticity, preferably a metal, and the thickness of the cantilever 110 affects the degree of deformation when an external force is applied, so that the strain of the material of the structure 50 to be measured It may be set to a suitable range in consideration of the slope range and the like.

In addition, the material that can be used as the inertial mass 100 is not particularly limited, and the weight thereof may be appropriately selected in consideration of mechanical characteristics such as inclination range to be measured or deformation characteristics of the cantilever 110.

In particular, the optical fiber sensors 120a and 120b according to the embodiment of the present invention are disposed to be spaced apart from the cantilever 110 at a predetermined interval.

In an inclinometer / accelerometer using an optical fiber sensor according to an embodiment of the present invention, the optical fiber sensors 120a and 120b are disposed between the structure 50 and the inertial mass 100 in a state where pre-strain is applied. It is connected to each other, the cantilever 110 is disposed at a predetermined interval away from the reflection wavelength in response to the bending deformation of the cantilever 110.

That is, the bending deformation of the cantilever 110 appears as the inclination occurs in the structure 50 connected to the cantilever 110, and the degree of bending deformation of the actual cantilever 110 is minute when the optical fiber sensor reacts to the bending deformation. Therefore, even if the optical fiber sensor is integrally attached to the cantilever 110, there is a considerable difficulty in determining the degree of inclination by accurately detecting the degree of bending deformation in the optical fiber sensor. However, as shown in FIG. 2, when the optical fiber sensors 120a and 120b are also connected to the structure 50 and the inertial mass 100 and spaced apart from the cantilever 110 at a predetermined distance, the bending deformation of the cantilever 110 may be reduced. As the degree is transmitted to the optical fiber sensors 120a and 120b spaced at a predetermined distance, the degree of inclination may be more accurately determined.

In more detail, when the inclination in the lower right direction with respect to the structure 50, the inclination occurs in the structure 50, but the inertia mass 100 is intact, so that bending deformation may occur to the right side of the cantilever 110. The length of the left side is longer than the right side depending on the degree of inclination. In this case, since the optical fiber sensors 120a and 120b are disposed on the left and right about the cantilever 110, the optical fiber sensor 120a disposed on the right side of the optical fiber sensor 120b disposed on the left side like the cantilever 110. The applied force is reduced, and thus the reflected wavelengths reflected from the left and right optical fiber gratings 120a and 120b are different from each other. The degree of inclination may vary depending on the distance between the optical fiber sensors 120a and 120b. As the optical fiber sensors 120a and 120b are disposed farther away from the cantilever 110, the distance between the optical fiber sensors increases and the degree of tilting downwards also increases. Therefore, even when the cantilever 110 is minutely deformed, the degree of deformation may be large between the optical fiber sensors 120a and 120b.

At this time, the optical fiber sensor (120a, 120b) is arranged in parallel so that at least two or more optical fibers are symmetrical about the cantilever 110, it may be made of a pair of two optical fibers symmetrical left and right. Of course, the pair of optical fibers in the present invention may be arranged face-symmetrical around the cantilever 110 and the number of optical fibers used as the optical fiber sensor in the present invention is not limited to two. For example, three or four optical fibers may be arranged in line symmetry or face symmetry about the cantilever 110.

On the other hand, the optical measuring means 150 may receive the reflected light from the left and right optical fibers and calculate the wavelength. When the reflected wavelengths at both sides have different values, it may be determined that the structure 50 is inclined. In addition, it is possible to calculate the magnitude of the tensile force applied to the left side or to the right side from the difference in the reflected wavelengths, and the degree of tilting from the calculated tensile force amount is already applied to the initial optical fiber grating since a certain amount of tensile force is applied to the prestrained state. Can be derived. In addition, it is possible to determine the inclination angle and the inclination direction of the structure from the distance between the optical fiber sensor and the derived degree of inclination, so that the resulting data can be displayed.

That is, the inclinometer using the optical fiber according to the present invention transmits the inclination degree to the optical fiber sensors 120a and 120b even when the structure 50 is finely inclined so that the optical fiber sensors 120a and 120b can detect the inclination degree. It can be measured more precisely according to the separation distance.

In addition, when the acceleration motion occurs in the structure, the inertial mass 100 interferes with the acceleration motion, and thus the inertial mass 100 causes the cantilever 110 to bend in the opposite direction of the acceleration direction. Accordingly, both side surfaces of the cantilever 110 may undergo compression and tensile deformation, and corresponding compression and tensile deformation may also occur in the spaced optical fiber sensors 120a and 120b.

For example, when the structure 50 moves at a constant speed in the left direction and the acceleration motion occurs in the same direction, the inertial mass 100 appears to move in the right direction, and accordingly, the right side of the cantilever 110 is compressed. , Left side is tensioned. Since the optical fiber sensors 120a and 120b are also connected to the inertial mass 100, they exhibit a similar motion to the cantilever 110. Accordingly, pressure is applied to the optical fiber grating 120a disposed on the right side of the cantilever 110. Tensile force is applied to the optical fiber grating 120b disposed on the left side of the 110.

The deformation occurring in the optical fiber sensors 120a and 120b changes the spacing of the optical fiber gratings, and thus the wavelength of the reflected light changes. The optical measuring means 150 may calculate the wavelength of the reflected light and calculate the acceleration therefrom, which may be derived from the change in the strain of the optical fiber sensor per unit time, and the acceleration values corresponding to the change in the strain per unit time are mapped to each other. It is desirable to calculate the acceleration from the prestored data.

Therefore, the inclinometer / accelerometer using the optical fiber according to the present invention can detect the degree when the structure 50 is tilted or accelerated by the optical fiber sensors 120a and 120b through the cantilever 110, and not only the acceleration degree but also the vibration It can also be applied to measure accuracy.

Figure 4 (a) is a schematic diagram illustrating the configuration of the inclinometer / accelerometer using the optical fiber sensor according to an embodiment of the present invention shown in FIG.

An inclinometer / accelerometer according to an embodiment of the present invention shown in FIG. 2 may be represented as shown in FIG. 4 (a), but the separation distance is transmitted to the optical fiber sensors 120a and 120b without modification of the cantilever 110. It may be spaced apart from the cantilever 110, and if it is disposed too far from the cantilever 110, it may be judged as an inclination by reacting easily to the change of the environment around the optical fiber as well as the inclination of the structure to a distance less than the length of the cantilever 110. It is preferable to arrange. This can be expressed as a simple expression:

Where Δx is the distance from the cantilever to the optical fiber sensor and l is the length of the cantilever.

As shown in Equation 1, an inclinometer / accelerometer using an optical fiber according to an embodiment of the present invention has a ratio of the length 1 and the separation distance Δx of the cantilever is 1/40 or more and has a value of 1 or less. When the cantilever 110 is 4 cm, 1/40 is a separation distance Δx of 1 mm. As the length of the cantilever is shorter, the cantilever 110 and the optical fiber sensors 120a and 120b are almost spaced apart. Since the distance Δx becomes short, it is preferably 1/20 or more, more preferably 1/10 or more.

Meanwhile, fixing members 130a and 130b for applying pre-strain to the optical fiber grating are disposed on the structure 50 and the inertial mass 100, respectively, and the optical fiber grating is between the fixing members 130a and 130b. The fixing members 130a and 130b and the optical fibers 120a and 120b may be fixed by bonding or the like in a state in which the optical fiber is disposed to be positioned and a tensile force of a predetermined size is applied to a portion where the optical fiber grating is formed.

The optical fiber sensors 120a and 120b are connected to the optical measuring means 150 through an optical fiber. The light measuring means 150 may include a light source, a light detector, and a controller, and a light emitting diode (LED or SLD) may be used as the light source. Therefore, when power is supplied to the light emitting diode, light having a constant wavelength distribution is emitted and the emitted light travels along the optical fiber to the optical fiber grating through a coupler.

The photodetector includes a photodiode (PD) to transmit the reflected light of a specific wavelength reflected from the optical fiber grating and transmit the photodiode to the photodiode. The photodiode measures and outputs the amount of incident reflected light. When the differentiator and the comparator are provided together, the photodiode and the peak point of the reflected light and the amount of light at this point can be calculated and transmitted to the controller.

The control unit may calculate the wavelength of the reflected light from the peak point and the light quantity data of the reflected light transmitted from the photodetector, and calculate the amount of strain change generated in the optical fiber grating from the calculated wavelength value and thereby connect the structure to the optical fiber sensors 120a and 120b. The degree of inclination of (50) can be calculated.

Accordingly, the inclinometer / accelerometer according to the embodiment of the present invention has a different reflection wavelength even with a small change in the lattice spacing, so that in addition to the advantages of the optical fiber sensor having excellent resolution, the fine bending deformation of the cantilever 110 connected to the structure 50 is reduced to the optical fiber sensor. Accuracy and precision can be greatly improved by being transmitted to (120a, 120b), and when applied to subway tunnels, etc., since it is not influenced at all by electromagnetic waves generated during subway operation, reliability can be greatly improved.

In particular, the inclinometer / accelerometer using the optical fiber sensor according to the present invention can measure the acceleration or inclination without the influence of the external temperature by compensating for the deformation caused by the temperature change can greatly increase the accuracy and reliability of the measurement.

In the optical fiber grating, the reflection wavelength is changed not only by physical force but also by temperature change. In the inclinometer / accelerometer according to the present invention, since two or more optical fiber sensors 120a and 120b are connected, the two optical fiber sensors are the same even if the temperature rises or falls. It shows the strain and thus the temperature compensation function is achieved because the fiber grating spacing increases or decreases together.

When the inclinometer / accelerometer using the optical fiber sensor according to the present invention is applied to a structure such as a bridge, the inclinometer / accelerometer may be arranged at a predetermined distance, and the degree of inclination calculated through the display unit provided in the optical measuring means may appear. When the optical measuring means are connected to each other to form a sensor network, a management server may be provided to receive the wavelength data of the reflected light calculated by each optical measuring means and calculate the inclination of each spot.

On the other hand, the inclinometer / accelerometer using the optical fiber sensor according to the present invention is that the cantilever and the optical fiber sensor is disposed at a predetermined distance, a specific embodiment for this can be applied without being limited to FIG.

Figure 3 is a block diagram showing the configuration of the inclinometer / accelerometer using an optical fiber sensor according to another embodiment of the present invention.

As shown in FIG. 3, the inclinometer using the optical fiber according to another embodiment of the present invention cantilever when the optical fibers 120'a and 120'b are not directly connected to the structure 50 and the inertial mass 100. As a means for forming and maintaining the separation distance with the (110) includes a predetermined connecting member (140a, 140b).

That is, the connecting members 140a and 140b are means for fixing the optical fiber to the cantilever 110 connected to the structure 50 and the inertial mass 100. When the bending deformation occurs in the cantilever 110, the degree of deformation of each optical fiber In order to be transmitted to the optical fiber grating between the connecting members (140a, 140b) is changed so that the reflected wavelength is changed accordingly.

Referring to the example with reference to Figure 2 applied to the embodiment shown in Figure 4, when the inclination occurs in the lower right direction of the structure 50, the bending deformation occurs to the right side of the cantilever 110. The two connecting members 140a connected to the right side of the cantilever 110 are disposed at a predetermined distance. As the bending deformation occurs, the distance between the connecting members 140a may be reduced. At this time, each connecting member 140a is fixedly connected to both ends of the optical fiber, and when the distance between the connecting members 140a is reduced, both ends of the connected optical fiber are also reduced. As a result, the tensile force applied to the optical fiber grating may be reduced, and the gap between the gratings may be reduced to reflect light having a wavelength different from that of the reflected light before the structure is tilted. Accordingly, the optical measuring means 150 detects the reflected light of different wavelengths and calculates a difference from the previous one, and calculates the inclination of the structure therefrom.

In addition, when the structure 50 is subjected to the acceleration movement in the left direction, as the inertial mass 100 moves in the right direction, bending deformation occurs to the right side of the cantilever 110, and deformation of the cantilever 110 is connected to the connecting member ( Different deformations are generated in the optical fiber gratings connected to the left and right of the cantilever 110 while being transmitted to the optical fiber sensors 120'a and 120'b through the 140a and 140b. Accordingly, the wavelengths of the reflected light may be different from each other, and the optical measuring means 150 may detect this and calculate the acceleration of the structure 50 from the difference.

The connecting members 140a and 140b may make a prestrained state by applying a fixed amount of tensile force at both ends of the optical fiber grating and the optical fiber grating is formed, and the length of the connecting members 140a and 140b becomes the separation distance between the optical fiber sensor and the cantilever. . As the connecting members 140a and 140b are longer, the spacing at both ends of the connected optical fiber may be greatly reduced even with a slight inclination, and thus, more detailed measurement of the bending deformation of the cantilever 110 may be possible.

Therefore, as shown in FIG. 4 (b) of the inclinometer / accelerometer shown in FIG. 3, the relationship between the length Δx of the connection member and the length l of the cantilever may be applied to Equation 1 as it is. As described above, the ratio between the length Δx of the connecting member and the length l of the cantilever should be 1/40 or more, but more preferably 1/20 or more and more preferably designed in a range of 1/10 or more.

On the other hand, the object to measure the acceleration or vibration through the inclinometer / accelerometer using the optical fiber sensor according to the present invention may correspond to the vertically arranged structures as well as the horizontally arranged structures. This is possible because the cantilever and the optical fiber sensor are fixedly connected to the inertial mass and the structure.In the case of the accelerometer, the inertial deformation is used when the acceleration occurs with respect to the movement of the object. Since the bending deformation of the cantilever occurs and the wavelength of reflected light reflected from the optical fiber grating is changed, the optical measuring means detects this and calculates the change in the tensile force according to the wavelength change, and calculates the acceleration of the structure therefrom.

As described above, the inclinometer / accelerometer using the optical fiber sensor according to the present invention has been described with reference to the illustrated drawings, but the present invention is not limited to the embodiments and drawings disclosed herein, and the optical fiber gratings are spaced apart from each other at regular intervals. It is apparent that the technical idea of the present invention, which includes a sensor and a cantilever to greatly improve the accuracy in measuring tilt or acceleration of a structure, can be easily applied by those skilled in the art within a protected range.

1 conceptually illustrates a piezoelectric accelerometer according to the prior art;

Figure 2 is a diagram showing the configuration of the inclinometer / accelerometer using an optical fiber sensor according to an embodiment of the present invention,

3 is a view showing the configuration of the inclinometer / accelerometer using an optical fiber sensor according to another embodiment of the present invention, and

4 is a schematic diagram illustrating an inclinometer / accelerometer using an optical fiber sensor according to an exemplary embodiment of the present invention.

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

10, 100: inertial mass 50: structure

110: cantilever 130a, 130b: fixing member

120a, 120b, 120'a, 120'b: optical fiber sensor 140a, 140b: connection member

150: light measuring means

Claims (5)

One end is fixed to the structure, the other end is connected to the inertial mass cantilever deformation is possible; And At least two FBG sensors spaced apart from the cantilever in parallel by a predetermined distance and disposed at symmetrical positions about the cantilever to be deformed according to the degree of deflection of the cantilever It includes, and the length (l) of the cantilever and the separation distance (Δx) between the cantilever and the FBG sensor is an inclinometer / accelerometer using an optical fiber sensor satisfying the following equation.

The method of claim 1, The FBG sensor is fixed member characterized in that both ends are fixed to the inertial mass and the structure in a direction parallel to the cantilever Inclinometer / accelerometer using an optical fiber sensor comprising a. The method of claim 1, Connecting members fixed to both ends of the FBG sensor and fixed to the cantilever, respectively. Inclinometer / accelerometer using an optical fiber sensor comprising a. The method of claim 1, The separation distance is inclinometer / accelerometer using an optical fiber sensor satisfying the following equation.

The method of claim 1, The separation distance is inclinometer / accelerometer using an optical fiber sensor satisfying the following equation.

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