KR100379746B1 - Structure Deformation Measurement Device And Structure Deformation Measurement Method - Google Patents

Abstract

The present invention relates to a structure deformation measuring apparatus and a structure deformation measuring method using a Bragg grating engraved optical fiber as a sensor for measuring and monitoring the deformation of simple and composite structures, and attaching a portion of the fiber engraved Bragg grating to the measurement structure After transmitting multi-wavelength light, it detects the deformation of the measuring structure and simultaneously transmits the light of Bragg wavelength band, and the light of the transmitted Bragg wavelength band is transmitted to the wavelength follower to measure and monitor the deformation degree of the measuring structure in real time. do.

Description

Structure Deformation Measurement Device And Structure Deformation Measurement Method

The present invention relates to a device for measuring the deformation degree of the structure used in the production site, and more particularly, to a structure deformation measurement device and structure deformation measurement method that can quickly and accurately measure and monitor the deformation degree of the structure It is about.

Recently, efforts to reduce production costs by shortening the production time at the production processing site are actively discussed in academia and industry.

Accordingly, in order to reduce the production time in the field, it is necessary to increase the processing speed and the driving speed, and for this, efforts have been made to reduce the weight of mechanical structures such as production machines.

Here, the weight reduction of the mechanical structure is confronted with problems such as deformation of the structure due to external load, deformation due to inertia during rapid acceleration and deceleration, deformation due to heat due to temperature rise, and the like.

Therefore, various strain prediction systems and strain measuring devices have been developed to measure and monitor the deformation of mechanical structures, such as strain measuring devices using strain gauges, strain prediction systems using laser interferometers, and optical spectruma analyzers. Optical wavelength detection system;

On the other hand, since the deformation prediction system or the strain measuring device has a complicated structure, it is difficult to install the complex mechanical structure to measure the deformation, and there is a problem that the installation takes a long time.

In addition, since the deformation prediction system and the strain measuring device are sensitive to the electronic and magnetic signals of the production site when applied to the field, accurate deformation measurement and monitoring are not easy.

In addition, the deformation prediction system and the deformation measuring device may not detect deformation or vibration of the structure due to external load.

Accordingly, the present invention has been made in view of the above problems, and a first object of the present invention is to provide a structure deformation measuring apparatus and a structure deformation measuring method capable of measuring and monitoring the deformation degree of a structure in real time. .

A second object of the present invention is to provide a structure deformation measuring apparatus and a structure deformation measuring method capable of precisely measuring the deformation degree of a structure.

The object of the present invention is a light source for emitting a multi-wavelength light;

A first optical fiber having one side connected to the light source to transmit the light;

Cross-connecting means connected to the other side of the first optical fiber to receive the light;

A second optical fiber connected to the cross connection means for transmitting the light;

A sensor grid for forming a plurality of Bragg gratings at predetermined intervals on the other side of the second optical fiber, attached to a measurement structure, and conveying light in the Bragg wavelength band to detect a degree of deformation;

A third optical fiber having one side connected to the cross connecting means for transmitting light in the Bragg wavelength band;

A plurality of Bragg gratings are formed at predetermined intervals on the other side of the third optical fiber to filter light in the Bragg wavelength band, and light sensing means for sensing current from the light in the Bragg wavelength band. Wavelength tracking consisting of a first piezoelectric element for applying a tensile force in the longitudinal direction to the filter grid, a second piezoelectric element for vibrating perpendicular to the longitudinal direction of the filter grid, and a displacement sensor attached to the filter grid to measure displacement. group;

A high frequency filter connected to the wavelength follower to filter vibration of the filter grid;

A gain controller connected to the high frequency filter to maintain a constant phase difference of the filter grid vibration;

A vibration frequency calculator connected to the gain controller to calculate a vibration frequency; And

Comprising a computer for calculating the strain on the basis of the vibration frequency; is achieved by a structure deformation measuring apparatus consisting of.

Here, the light source is preferably a light emitting diode.

In addition, the sensor grid is preferably bonded to the measuring structure with an epoxy resin.

In addition, the cross connection means is preferably an optical circulator.

In addition, the light sensing means is preferably a photodiode.

In addition, the above object of the present invention includes a first transmission step of transmitting the light of the multi-wavelength emitted from the light source to the sensor grid attached to the measurement structure through the optical circulator;

A deformation detection step of sensing the deformation of the measurement structure by the sensor grid receiving the light carrying light in the Bragg wavelength band;

A second progress step of transmitting the light of the Bragg wavelength band which is conveyed back to the filter lattice through the optical circulator;

Forming the same wavelength by the first piezoelectric element applying a tensile force in the longitudinal direction to the filter lattice such that the sensor lattice and the filter lattice undergo the same Bragg wavelength change;

A current resonance step of causing the second piezoelectric element to vibrate perpendicularly to the longitudinal direction of the filter grid such that the filter grid resonates;

A vibration filtration step of measuring displacement of the filter lattice in which a displacement sensor resonates, and filtering a vibration of the filter lattice by a high frequency filter;

A piezoelectric element control step of controlling, by the gain controller, the second piezoelectric element so as to keep the amplitude and phase of the filter grid constant;

The vibration frequency calculator calculates the vibration frequency of the filter lattice, and the computer calculates and measures the strain based on the vibration frequency; is achieved by the structure deformation measuring method comprising a.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings.

1 is a block diagram of a structure deformation measuring apparatus according to the present invention,

2 is a configuration diagram of a wavelength follower according to the present invention;

3 is a flowchart of a method for measuring structure deformation according to the present invention.

<Description of the code according to the main part of the drawing>

10: light source 20a: first optical fiber

20b: second optical fiber 20c: third optical fiber

30: optical circulator 40: measuring structure

50: sensor lattice 60: wavelength follower

60a: filter grid 60b: photodiode

60c: first piezoelectric element 60d: second piezoelectric element

60e: displacement sensor 70: high frequency filter

80: gain controller 90: vibration frequency calculator

95: computer 100: structure deformation measuring device

S100: first transmission step S200: deformation detection step

S300: second progress step S400: forming the same wavelength

S500: current resonance step S600: vibration filtration step

S700: piezoelectric element control step S800: strain calculation step

Prior to the detailed description of the structure of the structure deformation measuring apparatus and the structure deformation measuring method according to the present invention, the optical fiber Bragg grating sensor is used consistently in the present invention " This is a sensor using the characteristic that the wavelength of light reflected from each grating varies depending on the ambient temperature and the degree of tension. It reflects only the wavelengths satisfying the Bragg condition and transmits other wavelengths as it is. When is changed or tension is applied to the grating, the refractive index or length of the optical fiber is changed, thereby changing the wavelength of the reflected light.

Therefore, by measuring the wavelength of the light reflected from the optical fiber Bragg grating, it is possible to detect the temperature, tension, pressure, bending.

The largest application of the Bragg grating sensor is to install an optical fiber grid array in the concrete in the production of bridges, dams, buildings, etc., and to diagnose the safety state of the structure to detect the tensile distribution and bending degree in the structure, and the aircraft It is also applied to the diagnosis of wing conditions, such as helicopters.

Next, a detailed description will be given of the structure of the structure deformation measuring apparatus and the structure deformation measuring method according to the present invention.

1 is a block diagram of a structure deformation measuring apparatus according to the present invention, Figure 2 is a block diagram of a wavelength follower according to the present invention.

As shown in FIG. 1 and FIG. 2, the structure deformation measuring apparatus 100 receives a light source 10 that emits light having a large wavelength and the measurement structure 40 receives light from the light source 10. Sensor grid 50 for conveying light in the Bragg wavelength band by detecting the degree of deformation of the waveguide and connected to the wavelength follower 60 and the wavelength follower 60 for measuring the strain by receiving the light in the Bragg wavelength band It consists of a high frequency filter 70, a gain controller 80 connected to the high frequency filter 70, a vibration frequency calculator 90 connected to the gain controller 80 and a computer 95.

Here, the light source 10 is a kind of light emitting diode is emitted as a multi-wavelength light is transmitted to the cross-connecting means through the first optical fiber 20a, the cross-connecting means for adjusting the movement direction of the transmitted light It is a kind of optical circulator 30.

Then, the light transmitted to the optical circulator 30 is transmitted to the sensor grid 50 through the second optical fiber 20b, the sensor grid 50 to detect the degree of deformation of the measurement structure 40 In order to adhere to the measuring structure 40 with an epoxy resin, a plurality of Bragg gratings are carved at predetermined intervals, and are a predetermined portion of the second optical fiber 20b operated as a sensor.

Here, when the light of the multi-wavelength is transmitted to the sensor grid 50 and the sensor grid 50 detects the degree of deformation of the measurement structure 40, the light of the Bragg wavelength band is directed to the optical circulator 30 The light of the Bragg wavelength band is transmitted from the optical circulator 30 toward the wavelength follower 60.

At this time, the light of the Bragg wavelength band through the optical circulator 30 is transmitted to the wavelength follower 60 through the third optical fiber 20c of a predetermined length, the predetermined on one side of the third optical fiber 20c. The portion is formed with a plurality of Bragg gratings at regular intervals to form a filter grid (60a) provided in the wavelength follower (60).

In addition, the wavelength follower 60 is the filter grating 60a, light sensing means for detecting light in the Bragg wavelength band and generating a current proportional to its intensity, and the filter grating 60a in the longitudinal direction. A first piezoelectric element 60c for tensioning by applying a tensile force, a second piezoelectric element 60d for vibrating perpendicular to the longitudinal direction of the filter lattice 60a, and attached to the filter lattice 60a. It consists of a displacement sensor 60e for measuring the displacement of the filter grid 60a.

Here, the light sensing means is a kind of photodiode (60b), for detecting the intensity of the light transmitted to the filter grid (60a) to generate a current proportional to the intensity of the light, and the sensor grid (50) If the same Bragg wavelength change is made in the filter grid 60a, the current value generated by minimizing the intensity of light detected by the photodiode 60b is also minimized.

To this end, the first piezoelectric element 60c applies a physical tensile force to the filter grid 60a to induce a change in the same Bragg wavelength experienced by the sensor grid 50, so that the sensor grid also in the filter grid 60a. It can be subjected to the same strain change as in (50).

This is based on the Bragg wavelength change tracking principle that the Bragg wavelength change is proportional to the change of the strain. When the sensor grid 50 and the filter grid 60a undergo the same wavelength change, the current of the current in the photodiode 60b is changed. By minimizing the intensity, it can be seen whether the same wavelength change of the filter grid 60a is experienced.

In addition, the filter grid 60a receives the vibration applied by the second piezoelectric element 60d and resonates at a constant vibration frequency. The following mathematical equation representing the relationship between the resonance frequency of the filter grid 60a and the absolute strain is shown. The absolute strain of the measurement structure 40 can be measured by Equation 1.

Where f is the resonance frequency of the filter grid 60a, E is the Young's modulus, ε is the absolute strain, L ₀ is the length of the chord, and ρ is the density of the filter grid 60a.

On the other hand, the high frequency filter 70 is connected to the wavelength follower 60 to filter the vibration of the filter grid (60a) to identify and filter out only the vibration of the pure filter grid (60a).

In addition, the gain controller 80 is connected to the high frequency filter 70 so that the filter grid 60a keeps the phase difference of the vibration applied by the first piezoelectric element 60c constant.

In addition, the vibration frequency calculator 90 is connected to the gain controller 80 to calculate the vibration frequency of the filter grating 60a, and the computer 95 calculates and measures the strain based on the vibration frequency in real time. The degree of deformation of the measurement structure 40 can be monitored.

3 is a flowchart of a method for measuring structure deformation according to the present invention.

As shown in Figure 3, the measuring method is largely composed of seven steps to measure the degree of deformation of the measurement structure, as follows.

First, in the first transmission step (S100), the light of the multi-wavelength emitted from the light source 10 is transmitted to the sensor grid 50 attached to the measurement structure 40 through the optical circulator 30. The light having multiple wavelengths is transmitted by the first optical fiber 20a connecting the light source 10 and the optical circulator 30, and the light transmitted to the optical circulator 30 is the second optical fiber 20b. ) Is transmitted to the sensor grid 50 in which a Bragg grating is formed at one side of the second optical fiber 20b.

In the second step, the deformation detection step (S200), the sensor grid 50 receiving the light conveys light in the Bragg wavelength band, thereby detecting the deformation of the measurement structure 40. Since the degree of deformation, such as tension or bending, directly leads to a change in the Bragg wavelength band of the sensor grid 50, an immediate response to the degree of deformation of the measurement structure 40 can be made.

In the third step S300, the light of the Bragg wavelength band is transmitted back to the filter grid 60a through the optical circulator 30, and is connected to the optical circulator 30. Light in the Bragg wavelength band is transmitted through the three optical fibers 20c to reach the filter grid 60a in which a plurality of Bragg gratings are formed at one side of the third optical fiber 20c.

In the fourth step of forming the same wavelength (S400), the first piezoelectric element 60c extends longitudinally to the filter grid 60a such that the sensor grid 50 and the filter grid 60a undergo the same Bragg wavelength change. Apply tensile force.

This uses the Bragg wavelength principle that reflects only wavelengths satisfying the Bragg condition by using the characteristic that the wavelength of light reflected from the filter grid 60a changes according to the change in tensile strength, and transmits other wavelengths as it is. It is for the same to be expressed in the filter grid (60a) Bragg wavelength change that the sensor grid 50 undergoes according to the degree of deformation of the measurement structure (40).

In the fifth resonant step S500, the second piezoelectric element 60d vibrates perpendicularly to the length of the filter lattice 60a so that the filter lattice 60a resonates. This is measured by the vibration frequency of the filter grating 60a undergoing the same Bragg wavelength change as the sensor grating 50 in the same wavelength forming step (S400) by using Equation 1, that is, the relationship between the vibration frequency and the absolute strain. This is to measure the absolute strain of the measurement structure 40 by.

Where f is the resonance frequency of the filter grid 60a, E is the Young's modulus, ε is the absolute strain, L ₀ is the length of the chord, and ρ is the density of the filter grid 60a.

The sixth step, the vibration filtration step (S600) measures the displacement of the filter grid 60a in which the displacement sensor 60e resonates, and the high frequency filter 70 filters the vibration of the filter grid 60a so that the pure Only vibration of the filter grid 60a can be obtained.

In the seventh step, the piezoelectric element control step S700, the gain controller 80 controls the second piezoelectric element 60d to maintain the amplitude and phase of the filter grid 60a constant.

Finally, in the eighth step, the strain calculation step (S800), the vibration frequency calculator 90 calculates the vibration frequency of the filter grid 60a, and the computer 95 calculates the strain based on the vibration frequency in real time. In order to measure and monitor the deformation of the measurement structure 40.

Here, the degree of deformation of each element of the measuring structure 40 is calculated by the following Equation 2, as follows.

Where u and v are displacements of each element, θ is the deformation angle of the end of the element, l is the length of each element, h is the thickness of each element, and ε ^H and ε ^L are the strains on both sides of the element. This is the theory of deformation calculation through distributed strain based on the Transfer Matrix Method (TMM), which can take into account the limitation of the number of measurement points, thermal deformation, deformation by static load, and deformation by inertia.

In the present invention as described above, the light source 10 may be arbitrarily selected from a light emitting device such as a laser diode (LD), an organic EL device, an inorganic EL device, a multi-wavelength lamp in addition to the light emitting diode. In addition to the photodiode 60b, the light sensing means may be arbitrarily selected from a light receiving element such as an avalanche photo diode (APD). In addition, an optical coupler may be used in addition to the optical circulator 30 as the cross connecting means for adjusting the transmission direction of light.

As described above, according to the structure deformation measuring apparatus and the structure deformation measuring method according to the present invention, since the optical fiber which is relatively less affected by the surrounding electronic and magnetic signals as a sensor, an accurate and accurate structure with extremely low error It is effective to measure the degree of deformation. In addition, since the optical fiber used as the sensor responds sensitively to the degree of deformation of the structure, there is an effect of measuring and monitoring the degree of deformation of the structure in real time. In addition, since the deformation of the optical fiber used as a sensor can be inserted into the structure, the dispersion measurement can be performed in various directions without being concerned with the shape of the structure.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, various other modifications and variations may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the appended claims cover such modifications and variations as fall within the true scope of the invention.

Claims (7)

A light source 10 for emitting light of multiple wavelengths; A first optical fiber 20a connected to one side of the light source 10 to transmit the light; Cross-connecting means connected to the other side of the first optical fiber 20a to receive the light; A second optical fiber 20b connected to the cross connection means for transmitting the light; A plurality of Bragg gratings formed at predetermined intervals on the other predetermined portion of the second optical fiber 20b and attached to the measurement structure 40 to detect the degree of deformation by conveying light in the Bragg wavelength band; A third optical fiber 20c connected to one side of the cross connection means to transmit light in the Bragg wavelength band; A plurality of Bragg gratings are formed at predetermined intervals on the other side of the third optical fiber 20c to generate a current by receiving the filter grid 60a for detecting light in the Bragg wavelength band and the light of the Bragg wavelength band. An optical sensing means, a first piezoelectric element 60c for applying a tensile force in the longitudinal direction to the filter grid 60a, and a second piezoelectric element 60d for vibrating perpendicular to the longitudinal direction of the filter grid 60a. And a wavelength follower 60 attached to the filter grid 60a and configured with a displacement sensor 60e for measuring displacement. A high frequency filter (70) connected to the wavelength follower (60) to filter vibrations of the filter grid (60a); A gain controller (80) connected to the high frequency filter (70) to maintain a constant phase difference of vibration of the filter grid (60a); A vibration frequency calculator (90) connected to the gain controller (80) to calculate a vibration frequency; And And a computer (95) for calculating strain based on the vibration frequency. The method of claim 1, The light source 10 is a structure deformation measuring apparatus, characterized in that the light emitting diode. The method of claim 1, The sensor grid (50) is structure deformation measuring device, characterized in that the adhesive structure is bonded to the epoxy resin. The method of claim 1, The cross connection means is a structural deformation measuring apparatus, characterized in that the optical circulator (30). The method of claim 1, The optical sensing means is a structure deformation measuring apparatus, characterized in that the photodiode (60b) A first transmission step (S100) in which light of multiple wavelengths emitted from the light source 10 is transmitted to the sensor grid 50 attached to the measurement structure 40 through the optical circulator 30; A deformation detection step (S200) of detecting the deformation of the measurement structure 40 by transmitting the light of the sensor grid 50 receiving the Bragg wavelength band; A second progress step (S300) of transmitting the light of the Bragg wavelength band to be transmitted to the filter grid (60a) through the optical circulator (30); Forming the same wavelength (S400) in which the first piezoelectric element (60c) applies a tensile force in the longitudinal direction to the filter grid (60a) so that the sensor grid (50) and the filter grid (60a) undergo the same Bragg wavelength change; A current resonance step (S500) of causing the second piezoelectric element (60d) to vibrate perpendicularly to the length direction of the filter grid (60a) so that the filter grid (60a) resonates; A vibration filtration step (S600) of measuring displacement of the filter grid (60a) in which the displacement sensor (60e) resonates, and filtering the vibration of the filter grid (60a) by a high frequency filter (70); A piezoelectric element control step (S700) of controlling the second piezoelectric element (60d) by the gain controller (80) so as to keep the amplitude and phase of the filter grid (60a) constant; The vibration frequency calculator 90 calculates the vibration frequency of the filter grid 60a, and the computer 95 calculates and calculates the strain based on the vibration frequency (S800). Structure deformation measurement method. The method of claim 6, The degree of deformation of each element of the measuring structure 40 Calculated by Where u and v are displacements of each element; θ is the deformation angle of the end of the element; l is the length of each element; h is the thickness of each element; ε ^H , ε ^L is the strain on each side of the element; structure deformation measurement method characterized in that.