TWI856807B - Fiber Optic Grating Linearity Meter - Google Patents

Abstract

The present invention is an optical fiber grating pendulum instrument, which includes: a pendulum, a suspension, a plurality of optical fiber carriers, and a plurality of sensing optical fibers. One end of the pendulum is fixed to a structure. The suspension is arranged on the pendulum, the pendulum passes through the center of gravity of the suspension, and the suspension has at least one inclined surface. A plurality of optical fiber carriers are arranged on the structure and radially with the pendulum as the center, and each optical fiber carrier has an upper surface, a lower surface, and a suspended end. Each sensing optical fiber is formed with an optical fiber grating. The optical fiber grating is respectively provided on the upper surface and the lower surface of each optical fiber carrier. The suspended end of the optical fiber carrier is against the inclined surface of the suspension body. When the structure is tilted, the suspended end of the optical fiber carrier is further against the inclined surface of the suspension body and deformed, so that the optical fiber gratings arranged on the upper surface and the lower surface of the optical fiber carrier are deformed.

Description

Fiber Optic Grating Linearity Meter

The present invention relates to a pendulum, in particular to a pendulum using an optical fiber grating.

A pendulum is a device for measuring displacement, and is often used to measure the horizontal displacement of a reservoir dam or other tall buildings or structures. As shown in Figure 1, taking the dam D installed in the reservoir as an example, the water pressure generated by the water stored in the reservoir will cause the dam D to have a tendency to tilt and shift, so a pendulum needs to be installed inside the dam D for monitoring.

The pendulum of the pendulum instrument has two settings: hanging type (positive pendulum instrument) and inverted type (reverse pendulum instrument). The pendulum W1 of the positive pendulum instrument passes through the pipe P1. The upper end of the pendulum W1 is fixed to a position above each monitoring position in the dam body D, and a heavy hammer (not shown) is hung at the lower end of the pendulum W1 to make the pendulum W1 in a straight state. The heavy hammer is immersed in a liquid tank T1 (such as an oil tank or a water tank), and the liquid in the liquid tank T1 can be used as a vibration damper for the pendulum W1. When the pendulum W1 is shaken by vibration, the vibration damper can make the pendulum W1 return to a static state faster. The inverse pendulum instrument can be used to measure the horizontal displacement of the bottom of the dam D. The pendulum W2 of the inverse pendulum instrument passes through the pipe P2. The lower end of the pendulum W2 is fixed at the depth of the foundation under the dam D, and the upper end of the pendulum W2 is connected to a buoyancy member (not shown). The buoyancy member floats in the liquid tank T2 at the bottom of the dam D. The buoyancy pulls the pendulum W2, causing it to generate tension and present a straight state. In some cases, such as for dams with a height of hundreds of meters, the length of the pendulum may be limited by the curvature of the dam, so it is necessary to set up multiple sets of pendulums in sections along the elevation direction for monitoring. The same section of the pendulum can also be monitored at different elevations.

According to the principle of the reading and measuring instrument R, the pendulum can be divided into mechanical pendulum and optical pendulum. For the mechanical pendulum, the staff must regularly go to the monitoring room installed in the ballast body to check through the collimator to see if the relative position of the pendulum and the scale in the monitoring room has changed, so as to grasp the displacement and tilt of the ballast body. The reading and measuring instrument R of the optical pendulum uses a laser diode as a light source and a charge coupled device (CCD) array as a light detector. Since the position of the pendulum will block the light emitted by the light source, when the position of the pendulum changes relative to the optical detection array, the signal detected by the optical detection array will change. The signal read by the optical pendulum can be transmitted, so it can be monitored remotely.

However, for mechanical pendulums, it is necessary to regularly dispatch manpower to the observation rooms at different elevations of the dam to read and record data, which is rather troublesome. For optical pendulums, although they use automatic reading devices, since the signals generated by the optical detection array are electronic signals, the equipment components used for signal detection and transmission are easily affected by water vapor in the dam body and objects dropped after rusting of the pipes where the pendulums are installed, which is also not very satisfactory.

Therefore, in order to solve the problems existing in the previous technology, the inventor of this invention has painstakingly studied and thought for many years and invented a fiber optic grating oscillator in order to improve the deficiencies of the prior art and enhance its industrial applicability.

The technical means adopted by the present invention is to provide an optical fiber grating pendulum instrument, which includes: a pendulum, one end of which is fixed to a structure and the other end is not fixed; a suspension body, which is arranged on the pendulum, the pendulum passes through the center of gravity of the suspension body, and the suspension body has at least one inclined surface; a plurality of optical fiber carriers, which are arranged on the structure and radially arranged with the pendulum as the center, the optical fiber carrier having an upper surface and a lower surface, and the optical fiber carrier having a suspended end; a plurality of sensing optical fibers, each of which is shaped A fiber grating is formed, wherein the upper surface of each fiber carrier is provided with the fiber grating correspondingly, and the lower surface of each fiber carrier is provided with the fiber grating correspondingly; wherein the suspended end of the fiber carrier abuts against the inclined surface of the suspension body, and the fiber carrier is arranged so that when the structure is tilted, the suspended end of one or more fiber carriers further abuts against the inclined surface of the suspension body and deforms, so that the fiber gratings arranged on the upper surface and the lower surface of the one or more fiber carriers are deformed.

In one embodiment of the fiber grating pendulum of the present invention, the number of the fiber gratings is four, the distance between each fiber grating disposed on the upper surface of the fiber grating is equal to the distance between each fiber grating disposed on the upper surface of the adjacent fiber grating and the pendulum, the distance between each fiber grating disposed on the lower surface of the fiber grating is equal to the distance between each fiber grating disposed on the lower surface of the adjacent fiber grating and the pendulum.

In one embodiment of the optical fiber grating pendulum of the present invention, the suspended end of the optical fiber carrier is pressed against the inclined surface of the suspension body by a ball pulley.

In one embodiment of the fiber grating oscillator of the present invention, the inclined surface is a chamfered cone surface, and the oscillator line passes through the central axis of the chamfered cone surface.

In one embodiment of the optical fiber grating oscillator of the present invention, the optical fiber carrier is an elastic steel sheet.

In one embodiment of the fiber grating pendulum of the present invention, the fiber grating pendulum further includes a shielding body, the pendulum passes through the center of gravity of the shielding body, the shielding body is fixed to the pendulum and arranged above the fiber gratings, and the shielding body shields the fiber gratings when viewed from above.

In one embodiment of the optical fiber grating oscillator of the present invention, the shielding body is provided with an inclined surface, and the inclined surface is inclined from the center to the outer edge of the shielding body from top to bottom.

In one embodiment of the optical fiber grating oscillator of the present invention, the inclined surface of the shielding body is a conical surface, and the oscillator passes through the central axis of the conical surface.

The fiber grating pendulum meter of the present invention uses a fiber grating for sensing. The detection signal emitted by the light source is transmitted via the optical fiber, and is reflected by the fiber gratings set at different observation heights of the structure, and then interpreted by the fiber grating signal interpreter, and the horizontal displacement of the structure along the X and Y directions is deduced from the deformation of the fiber grating. In the fiber optic grating sway meter of the present invention, both the detection signal and the reflection signal are transmitted through optical fibers. Since optical fibers are passive components and are inherently safe (explosion-proof), compared to traditional electronic instruments, they have the advantages of small size, long transmission distance, high durability and stability, and are not affected by electromagnetic waves, lightning strikes, moisture, etc. Therefore, compared to traditional mechanical and optical sway meters, the fiber optic grating sway meter of the present invention has improved convenience, durability, and anti-interference.

100: Fiber optic grating line meter

1: Hanging line

2: Suspension body

21: Inclined surface

3: Fiber optic carrier

31: Upper surface

32: Lower surface

3C: suspended end

4: Sensing optical fiber

41: Fiber grating

42: Fiber grating

5: Shielding body

51: Slope

S: Detection signal

Sr: reflected signal

B:Structure

P:Pipeline

E: Seat

L: ball pulley

X: Direction

Y: Direction

D: Dam body

W1: Swing line

W2: swing line

T1: Liquid tank

T2: Liquid tank

R: Reading and measuring instruments

Figure 1 is a schematic diagram of the pendulum being used in a dam.

Figure 2A is a schematic diagram of an embodiment of the optical fiber grating oscillator of the present invention.

Figure 2B is a top view of the fiber grating oscillator in Figure 1A.

Figure 3 is a schematic diagram of the fiber grating oscillator of the present invention when it senses the tilt of a structure.

The detailed description and technical content of the present invention are described below with accompanying drawings. The attached drawings are only examples for reference and illustration to help understand the present invention and are not intended to limit the scope of the present invention.

Figures 2A and 2B disclose an embodiment of the fiber grating pendulum meter of the present invention. The fiber grating pendulum meter 100 can be used to detect the horizontal displacement of a structure B (such as the dam and dam foundation of a reservoir, bridge piers, and high-rise buildings). The fiber grating pendulum meter 100 includes: a pendulum 1, a suspension body 2, a plurality of optical fiber carriers 3, and a plurality of sensing optical fibers 4. The fiber grating pendulum meter 100 can be set at multiple elevation positions in the structure B.

One end of the pendulum 1 is fixed to the structure B, while the other end is not fixed and is in a freely movable state. The pendulum 1 can be set in the pipe P set in the structure B. The pendulum 1 can be set in a hanging manner, that is, the upper end of the pendulum 1 is fixed to a position above each monitoring position in the structure B, and the lower end adopts the setting method of the pendulum W1 mentioned above and in Figure 1 or other setting methods based on similar principles. The pendulum 1 can also be set in an inverted manner, that is, the lower end of the pendulum 1 is fixed to the depth of the foundation under the structure B, and the upper end adopts the setting method of the pendulum W2 mentioned above and in Figure 1 or other setting methods based on similar principles. The pendulum 1 can be a steel wire.

The suspension body 2 is arranged on the pendulum line 1, and the pendulum line 1 passes through the center of gravity of the suspension body 2. The suspension body 2 has at least one inclined surface 21. In this embodiment, the inclined surface 21 is a chamfered cone surface, and the pendulum line 1 passes through the central axis of the chamfered cone surface.

A plurality of optical fiber carriers 3 are disposed on the structure B and are radially arranged with the pendulum 1 as the center. Each optical fiber carrier 3 has an upper surface 31 and a lower surface 32, and has a suspended end 3C. The suspended end 3C of each optical fiber carrier 3 abuts against the inclined surface 21 of the suspension body 2. In this embodiment, the optical fiber carriers 3 are disposed on the structure B through the seat E (as shown in FIG. 2A).

Each sensing optical fiber 4 is formed with an optical fiber grating 41, 42. The upper surface 31 and the lower surface 32 of each optical fiber carrier 3 are each provided with a sensing optical fiber 4. The sensing optical fiber 4 provided on the upper surface 31 of each optical fiber carrier 3 is formed with an optical fiber grating 41, and the sensing optical fiber 4 provided on the lower surface 32 of each optical fiber carrier 3 is formed with an optical fiber grating 42. The upper surface 31 of each optical fiber carrier 3 is each provided with an optical fiber grating 41, and the lower surface 32 of each optical fiber carrier 3 is each provided with an optical fiber grating 42. In this embodiment, the number of the optical fiber carriers 3 is four, and the distance between each optical fiber grating 41 disposed on the upper surface 31 of the optical fiber carrier 3 and the optical fiber grating 41 disposed on the upper surface 31 of the adjacent optical fiber carrier 3 is equal, and the distance between each optical fiber grating 41 disposed on the upper surface 31 of the optical fiber carrier 3 and the pendulum 1 is equal. The distance between each optical fiber grating 42 disposed on the lower surface 32 of the optical fiber carrier 3 and the optical fiber grating 42 disposed on the lower surface 32 of the adjacent optical fiber carrier 3 is equal, and the distance between each optical fiber grating 42 disposed on the lower surface 32 of the optical fiber carrier 3 and the pendulum 1 is equal. The purpose of this configuration is to measure the horizontal offset of structure B in the mutually perpendicular directions X and Y.

Fiber Bragg Grating is a stripe area with a change in refractive index formed by partial exposure of a fiber. When a broadband incident light signal passes through a fiber grating, only a specific wavelength that meets the Bragg condition (called fiber grating wavelength, reflection wavelength or Bragg wavelength) will be reflected to produce a narrowband reflection signal, while the remaining wavelengths of light will pass through the fiber grating and continue to move forward. The fiber grating wavelength is related to the fiber grating period (the spacing between the stripes, also known as the pitch) and the effective refractive index. When the fiber grating is deformed by force or temperature, its period or refractive index will change, causing the incident light signal to generate another reflection signal of a different wavelength. By analyzing and comparing the reflection signal of the deformed fiber grating with the reflection signal of the undeformed fiber grating, the strain of the fiber grating can be deduced, and the horizontal displacement, tilt and subsidence of the structure can be further deduced from the strain of the fiber grating. Therefore, the fiber grating can be used to monitor the tilt of the structure, or monitor the subsidence of petrochemical pipelines and fixed frame foundations, ground surfaces, bridges, and railroads.

The optical fiber gratings 41 and 42 formed on the sensing optical fiber 4 can receive the detection signal S from the light source (not shown) and generate a reflection signal Sr. The reflection signal Sr will be sent back to the signal interpretation instrument (not shown) for staff to analyze and interpret. The detection light source can be a semiconductor laser, a gas laser or a solid laser.

As shown in FIG. 3 , when the structure B tilts (the tilt angle in the figure is exaggerated to make the concept of the invention easier to understand), the suspended end 3C of the optical fiber carrier 3 is close to the inclined surface 21 of the suspension body 2, causing the optical fiber carrier 3 to deform, and then the optical fiber gratings 41 and 42 disposed on the upper surface 31 and the lower surface 32 of the optical fiber carrier 3 to deform, causing the reflected signal Sr to change and causing the instrument to detect that the structure B is tilted and horizontally displaced. In this arrangement, when the optical fiber carrier 3 is deformed, the optical fiber grating 41 disposed on the upper surface 31 will stretch or shorten, and the optical fiber grating 42 disposed on the lower surface 32 will shorten or stretch. This arrangement has a temperature compensation effect, which can eliminate the deformation amount caused by the temperature increase of the optical fiber carrier 3 in the sensing data. The optical fiber carrier 3 can be an elastic steel sheet or other material with appropriate elasticity. The suspended end 3C of the optical fiber carrier 3 can be pressed against the inclined surface 21 of the suspension body 2 by a ball pulley L or other suitable methods. Because when the structure B is tilted, the horizontal displacement generated may not be in a single direction (that is, there is displacement in the direction X and the direction Y at the same time). Since the rotation of the ball pulley L is not restricted by direction, it can move in both directions on the inclined surface 21 of the suspension body 2 in coordination with the inclination of the structure B, so that the optical fiber carrier 3 can be deformed without restriction as the ball pulley L rolls. Therefore, the deformation of the optical fiber carrier 3 and the optical fiber gratings 41 and 42 can more accurately reflect the actual inclination of the structure B. In contrast, if a one-way rolling pulley is used, since there is a large friction between the pulley and the inclined surface 21 of the suspension body 2 in the non-pulley rolling direction, the pulley is limited in its movement direction relative to the inclined surface 21 of the suspension body 2. In this case, the deformation of the optical fiber carrier 3 and the optical fiber gratings 41 and 42 cannot accurately reflect the degree of inclination and horizontal displacement of the structure B.

Please refer to Figures 2A and 3, where each of the optical fiber carriers 3 can be installed in a pre-bent downward manner. When the structure B tilts, the suspended end 3C of the optical fiber carrier 3 is further squeezed by the suspension body 2 due to the tilt of the structure B, causing the suspended end 3C of the optical fiber carrier 3 to bend further than the pre-bent state, so that the optical fiber grating 41 disposed on the upper surface 31 will be stretched and the optical fiber grating 41 disposed on the lower surface 31 will be stretched. 2 will be shortened; on the contrary, due to the inclination of the structure B, the suspended end 3C of the optical fiber carrier 3 away from the suspension body 2 can rebound from the pre-bent state to the unbent state, so that the optical fiber grating 41 arranged on the upper surface 31 will be shortened, and the optical fiber grating 42 arranged on the lower surface 32 will be extended.

Furthermore, the optical fiber grating pendulum 100 further includes a shielding body 5, and the pendulum 1 passes through the center of gravity of the shielding body 5. The shielding body 5 is fixed to the pendulum 1 and is arranged above the optical fiber gratings 41 and 42. As shown in FIG. 2B, the shielding body 5 shields the optical fiber gratings 41 and 42 when viewed from above. The shielding body 5 is provided with an inclined surface 51, and the inclined surface 51 is inclined from the center to the outer edge of the shielding body 5 from top to bottom. In order to make water droplets falling on the shielding body 5 and debris (such as iron filings) peeled off by pipeline embroidery slide off. In this embodiment, the inclined surface 51 of the shielding body 5 is a conical surface, and the pendulum line 1 passes through the central axis of the conical surface.

The fiber grating line meter of the present invention uses a fiber grating for sensing, and both the detection signal and the reflection signal are transmitted by the optical fiber. Since the optical fiber is a passive component and is inherently safe (explosion-proof), compared with traditional electronic instruments, it has the advantages of small size, long signal transmission distance, high durability and stability, and is not easily affected by electromagnetic waves, lightning strikes, moisture, etc. Compared with traditional mechanical and optical line meters, the fiber grating line meter of the present invention has improved convenience, durability and anti-interference.

The above is only the preferred feasible embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the description and drawings of the present invention are also included in the scope of the present invention.

100: Fiber optic grating line meter

1: Hanging line

2: Suspension body

21: Inclined surface

3: Fiber optic carrier

31: Upper surface

32: Lower surface

3C: suspended end

4: Optical fiber

41: Fiber grating

42: Fiber grating

5: Shielding body

51: Slope

B:Structure

P:Pipeline

E: Seat

L: ball pulley

Claims (8)

A fiber grating pendulum instrument includes: a pendulum, one end of which is fixed to a structure and the other end is not fixed; a suspension body, which is arranged on the pendulum, the pendulum passes through the center of gravity of the suspension body, and the suspension body has at least one inclined surface; a plurality of optical fiber carriers, which are arranged on the structure and radially arranged with the pendulum as the center, each of which has an upper surface and a lower surface, and the optical fiber carrier has a suspended end; A plurality of sensing optical fibers, each of which is formed with an optical fiber grating, wherein the upper surface of each optical fiber carrier is provided with the optical fiber grating correspondingly, and the lower surface of each optical fiber carrier is provided with the optical fiber grating correspondingly; wherein the suspended end of the optical fiber carrier abuts against the inclined surface of the suspension body, and the optical fiber carrier is arranged so that when the structure is tilted, the suspended end of one or more optical fiber carriers further abuts against the inclined surface of the suspension body and deforms, so that the optical fiber gratings arranged on the upper surface and the lower surface of the one or more optical fiber carriers are deformed. The fiber grating pendulum as described in claim 1, wherein the number of the fiber gratings is four, the distance between each fiber grating disposed on the upper surface of the fiber grating is equal to the distance between each fiber grating disposed on the upper surface of the adjacent fiber grating and the pendulum, the distance between each fiber grating disposed on the lower surface of the fiber grating is equal to the distance between each fiber grating disposed on the lower surface of the adjacent fiber grating and the pendulum. An optical fiber grating pendulum as described in claim 1, wherein the suspended end of the optical fiber carrier is pressed against the inclined surface of the suspension body by a ball pulley. A fiber grating pendulum as described in any one of claims 1 to 3, wherein the inclined surface of the suspension body is a chamfered cone surface, and the pendulum passes through the central axis of the chamfered cone surface. An optical fiber grating oscillator as described in claim 4, wherein the optical fiber carrier is an elastic steel sheet. The fiber grating pendulum as described in any one of claims 1 to 3 further includes a shielding body, the pendulum line passes through the center of gravity of the shielding body, the shielding body is fixed to the pendulum line and arranged above the fiber gratings, and the shielding body shields the fiber gratings when viewed from above. The optical fiber grating oscillator as described in claim 6, wherein the shielding body is provided with an inclined surface, and the inclined surface is inclined from top to bottom from the center to the outer edge of the shielding body. The optical fiber grating oscillator as described in claim 7, wherein the inclined surface of the shielding body is a cone surface, and the oscillator line passes through the central axis of the cone surface.

Images