KR20220168863A - Apparatus and method for structural health monitoring using distributed sensing technique based on random-accessibility and multi-spatial Resolution - Google Patents

Abstract

Disclosed are an apparatus and method for monitoring structural health utilizing a distributed sensing technique capable of random position measurement and multi-spatial resolution measurement. The method for monitoring structural health includes: a step of generating a reference value by obtaining a measurement value in an initial state of a structure to be monitored, which has measured with a pre-set low-fidelity reference and a pre-set high-fidelity reference; a step of obtaining a measurement value by first measurement point measured with the low-fidelity reference and performing monitoring for the structure to be monitored with the low-fidelity reference by using the obtained measurement value by first measurement point and the reference value; a step of obtaining a measurement value by second measurement point measured with the high-fidelity reference in a section where an abnormal value is found when the abnormal value is found in the obtained measurement value by first measurement point as a monitoring result; and a step of calculating a damaged position by detecting an abnormal value in the obtained measurement value by second measurement point. Accordingly, the present invention may detect damage to a structure in an accurate manner.

Description

Apparatus and method for structural health monitoring using distributed sensing technique based on random-accessibility and multi-spatial resolution}

The present invention relates to an apparatus and method for monitoring structural integrity using a distributed sensing technique capable of measuring arbitrary positions and measuring multi-spatial resolution.

Deterioration of social infrastructure in public use is an increasingly important global issue, and many studies are underway. Korea, as in the case of the United States and Japan, recognizes that the aging of SOC facilities will become a problem rapidly in the future, and is conducting research and development on efficient and reliable maintenance technology for this purpose. Structural integrity monitoring is a system that measures facilities using sensors installed in social infrastructure, detects damage early based on this, and promptly gives an alarm to the management body to support decision-making such as maintenance.

In general, a measurement system using a strain sensitive to damage is widely used, and a lot of research has been conducted using an optical fiber sensor that can be used permanently because it is highly durable and not affected by electromagnetic interference. A typical fiber optic sensor is a fiber Bragg grating sensor.

1 is a diagram illustrating a sensing concept of a point sensor and a distributed sensor.

Referring to FIG. 1 , an optical fiber grating sensor is a system that measures strain and temperature using light reflected from a grating engraved at a specific position of an optical fiber, like the sensing concept of the point sensor shown in FIG. 1 . That is, the fiber optic grating sensor is a point sensor that measures the response of a specific position of an optical fiber.

In large-scale social infrastructure, the limitations of structural integrity monitoring using point sensors are as follows.

First, there is the possibility of missing a defect (damage) detection. Since only the response of the location where the point sensor is located is measured, it is possible to detect only the damage that occurred in the vicinity of the point sensor. Therefore, when damage occurs at a location other than the vicinity of the point sensor, it is difficult to detect it. Furthermore, undetected damage can greatly affect the performance and durability of a structure, and in the worst case, cause an accident.

Second, economic and technical challenges exist when constructing and operating a maintenance management system. When applied to a large social infrastructure such as a dam, installing a large number of point sensors in a vast area excessively increases the initial system construction cost. Also, since defect (damage) information cannot be known in advance, the sensor system must be designed and built within an available budget. This, in turn, means that there is still the possibility of missing a corruption detection.

Again, referring to FIG. 1, as a method of overcoming the limitations of point sensors, like the distributed sensor shown in FIG. 1, a distributed sensor capable of continuous measurement in the length direction of an optical fiber cable due to scattering in an optical fiber. Research using it is in progress. Advantages and disadvantages of such a distributed sensor are as follows.

The first advantage is that a general optical fiber cable can be used as a sensing unit. The distributed fiber optic sensing technique can be performed using a general communication fiber optic cable. So, it can be used to measure strain and temperature by attaching an optical fiber cable for general communication to a large social infrastructure. In general, an optical fiber grating sensor incurs cost for grid generation, but a general communication fiber optic cable does not incur additional production and purchase costs.

The second advantage is that continuous sensing is possible in the length direction of the optical fiber. When an optical fiber cable is attached to the entire structure, it is possible to measure the strain throughout the structure, and through this, it is easy to determine whether or not damage has occurred.

Next, the first disadvantage is that repeated measurements are required due to a low signal to noise ratio (SNR) in the scattered wave. Since measurement is performed through scattering in the optical fiber, it has a low signal-to-noise ratio. Therefore, it is necessary to reduce noise by performing multiple sensing for the same location and averaging them. Therefore, when measurement of a large number of measurement points (tens of thousands to tens of thousands of points) is required for a large infrastructure (sensing section of 1 km length), it takes a lot of time to measure and it is difficult to quickly detect damage.

The second disadvantage is that there is a presence or absence of precise damage position detection according to spatial resolution. Distributed sensing techniques have the concept of spatial resolution. The spatial resolution is expressed in units of length, and the measured value according to the spatial resolution may mean an average value of strain or temperature measured per unit length. The high spatial resolution of several centimeters (cm) can create dense measurement points in units of several centimeters in the length direction of the optical fiber. On the other hand, a low spatial resolution of several meters (m) can create measurement points in units of several meters in the fiber length direction.

For example, in order to precisely detect damage, if an optical fiber of 1 km is measured in the length direction in 2 cm units, which is a high spatial resolution, 50,000 points are generated. In the case of repeated measurement N times to improve the SNR in the actual field, the measurement time can increase linearly by the number of repetitions (50,000 points * N times). On the other hand, if a 1 km optical fiber is measured with a low spatial resolution of 10 m, 100 points are generated. When repeated measurement is performed N times to improve SNR, the measurement time can increase linearly by the number of repetitions (100 points * N times).

Scattered waves measured per unit length along the length direction of the optical fiber may be converted into a physical quantity (eg, Brillouin frequency) related to strain or temperature through signal processing. For example, if the number of points that can be processed per second is 10 points, the time required to process 50,000 points generated in high spatial resolution is 5,000 seconds (50,000/10). On the other hand, the time required to process 100 points generated at low spatial resolution is 10 seconds (100/10), which greatly reduces the required time.

Therefore, when the distributed sensor is used for health monitoring of large structures such as dams and super-long span bridges, the following trade-off occurs. That is, when a high spatial resolution is used, the measurement point becomes dense and the damage location can be accurately detected, but the measurement time is excessively increased and the effectiveness may be reduced. On the other hand, when a low spatial resolution is used, measurement points become rare and measurement time is consumed at a usable level, but it may be difficult to accurately detect the damage location.

Republic of Korea Patent Registration No. 10-0879601 (2009.01.13)

The present invention provides an apparatus and method for monitoring structural health by using a distributed optical fiber sensor system capable of measuring arbitrary position and multi-spatial resolution, while monitoring structures, and accurately detecting structural damage by adaptively adjusting spatial resolution. It is for

According to one aspect of the present invention, structure health monitoring performed by a structure health monitoring device that obtains the measured value from a distributed optical fiber sensor device that calculates the measured value through an optical fiber cable for measurement installed along the monitoring section of the structure to be monitored. A method is disclosed.

In the structure integrity monitoring method according to an embodiment of the present invention, measured values of the initial state of the structure to be monitored are measured with a preset low-fidelity reference and a preset high spatial resolution (high-fidelity reference). Acquiring and generating a reference value, acquiring a measurement value for each first measurement point measured with the low spatial resolution, and using the obtained measurement value for each first measurement point and the reference value to monitor the target with the low spatial resolution Monitoring the structure, when an outlier is found among the obtained measurement values for each first measurement point as a result of the monitoring, measurement for each second measurement point measured with the high spatial resolution in a section in which the outlier is found The method includes obtaining a value and calculating a damage location by detecting an outlier among the obtained measurement values for each second measurement point.

In the generating of the reference value, a low spatial resolution reference value and a high spatial resolution reference value measured for each of the low spatial resolution and the high spatial resolution are generated.

The monitoring may include, after controlling the distributed optical fiber sensor device to measure with the low spatial resolution, periodically acquiring measurement values for each of the first measurement points from the distributed optical fiber sensor device, and A difference value between the measured value for each first measurement point and the low spatial resolution reference value is calculated, and an outlier is detected by checking whether the calculated difference value exceeds a preset threshold value.

The obtaining of the measurement value for each second measurement point may include controlling the distributed optical fiber sensor device to measure a section in which the outlier is found with the high spatial resolution, and then the second measurement from the distributed optical fiber sensor device. Obtain measurement values for each point.

The calculating of the damage location may include calculating a difference between the measured value for each second measurement point and the high spatial resolution reference value, and detecting an outlier by checking whether the calculated difference value exceeds a preset threshold value. And, the measurement point determined to be the outlier is calculated as the damage location.

According to another aspect of the present invention, a structure health monitoring device that obtains a measurement value from a distributed optical fiber sensor device that calculates a measurement value through an optical fiber cable for measurement installed along a monitoring section of a structure to be monitored is disclosed.

An apparatus for monitoring structural health according to an embodiment of the present invention includes a memory for storing instructions and a processor for executing the instructions, wherein the instructions have preset low-fidelity reference and preset high spatial resolution. generating a reference value by obtaining a measurement value of an initial state of the structure to be monitored, which is measured as a high-fidelity reference; obtaining a measurement value for each first measurement point measured with the low spatial resolution; 1 Performing monitoring of the structure to be monitored with the low spatial resolution using the measured value at each measurement point and the reference value, when an outlier is found among the obtained measurement values at each first measurement point as a result of the monitoring, Acquiring a measurement value for each second measurement point measured with the high spatial resolution in a section in which the outlier is found, and calculating a damage location by detecting an outlier among the acquired measurement values for each second measurement point. Perform structural integrity monitoring methods.

An apparatus and method for monitoring structural health according to an embodiment of the present invention monitors a structure using a distributed optical fiber sensor system capable of measuring arbitrary positions and multi-spatial resolutions, but prevents structural damage by adaptively adjusting the spatial resolution. can be accurately detected.

1 is a diagram illustrating a sensing concept of a point sensor and a distributed sensor;
2 is a flowchart illustrating a structure health monitoring method performed by a structure health monitoring apparatus according to an embodiment of the present invention.
3 to 8 are views for explaining a structure health monitoring method according to the embodiment of the present invention of FIG. 2;
9 is a view schematically illustrating the configuration of a structure health monitoring device according to an embodiment of the present invention.

Singular expressions used herein include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "consisting of" or "comprising" should not be construed as necessarily including all of the various components or steps described in the specification, and some of the components or some of the steps It should be construed that it may not be included, or may further include additional components or steps. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. .

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

2 is a flowchart illustrating a structure health monitoring method performed by a structure health monitoring device according to an embodiment of the present invention, and FIGS. 3 to 8 are for explaining the structure health monitoring method according to the embodiment of the present invention of FIG. 2 it is a drawing Hereinafter, a structure integrity monitoring method according to an embodiment of the present invention will be described with reference to FIG. 2, but reference will be made to FIGS. 3 to 8.

In step S210, the structure integrity monitoring device 100 measures the initial state of the structure to be monitored 10 measured with a preset low-fidelity reference and a preset high spatial resolution. Obtain a value to create a reference value.

3 is a diagram schematically illustrating a structure health monitoring system according to an embodiment of the present invention.

Referring to FIG. 3 , a structure health monitoring system according to an embodiment of the present invention may include a structure health monitoring device 100, a distributed fiber optic sensor device 200, and an optical fiber cable 210 for measurement.

The structure health monitoring device 100 according to the embodiment of the present invention may obtain continuous measurement values of the monitoring section of the structure to be monitored 10 from the distributed optical fiber sensor device 200 . Here, the distributed optical fiber sensor device 200 may calculate the measurement value through the optical fiber cable 210 for measurement installed along the monitoring section of the structure to be monitored 10 .

For example, the distributed optical fiber sensor device 200 may be a Brillouin Optical Correlation Domain Analysis (BOCDA) device, receives scattered waves at each measurement point of the optical fiber cable 210 for measurement according to a preset spatial resolution, and receives the received scattered waves. The measured value can be calculated by converting the scattered wave into a physical quantity related to strain or temperature through signal processing of . In addition, the optical fiber cable 210 for measurement may be a general optical fiber cable for communication to which a single-mode optical fiber core is applied.

The distributed optical fiber sensor device 200 may be implemented to operate with multiple spatial resolutions that vary according to measurement parameter settings. Here, the multi-spatial resolution may include low spatial resolution and high spatial resolution.

For example, a low spatial resolution may be set to a unit length of several centimeters (cm), and a high spatial resolution may be set to a unit length of several meters (m). At this time, the measurement point interval (Readout) may be set to several centimeters (cm) to several meters (m). The distributed optical fiber sensor device 200 may perform measurement through distributed sensing up to several kilometers (km).

In addition, the distributed optical fiber sensor device 200 may perform measurement at an arbitrary measurement point without sequentially measuring in the length direction of the optical fiber cable 210 for measurement.

For example, the measurement performance of the distributed optical fiber sensor device 200 required in a large-scale social infrastructure can be defined as shown in FIG. 4 .

That is, as shown in FIG. 5 , the structure health monitoring device 100 uses the distributed optical fiber sensor device 200 to determine the initial state of the structure to be monitored 10 for each preset high spatial resolution and preset low spatial resolution. It is possible to generate a low spatial resolution reference value and a high spatial resolution reference value by measuring .

For example, when damage occurs in the structure to be monitored 10 near the optical fiber cable 210 for measurement, the measured value at the point where the damage occurs may show a large difference from the measured value before the damage (ie, the reference value). .

In step S220, the structure integrity monitoring device 100 obtains measurement values for each measurement point measured with low spatial resolution, and monitors the structure to be monitored 10 with low spatial resolution.

That is, referring to FIG. 6 , the structure health monitoring device 100 controls the distributed optical fiber sensor device 200 to measure with low spatial resolution, and then measures the measured with low spatial resolution from the distributed optical fiber sensor device 200. A measurement value for each measurement point may be periodically acquired, and a difference value between the obtained measurement value for each measurement point and a low spatial resolution reference value may be calculated. In addition, the structure health monitoring apparatus 100 may detect an outlier by checking whether the calculated difference value exceeds a preset threshold value.

For example, the apparatus 100 for monitoring structure integrity may perform anomaly detection using a median absolute deviation (MAD) algorithm with respect to the calculated difference value for each measurement point. Here, the MAD algorithm is a method of detecting outliers using the median absolute deviation.

In step S230, the apparatus 100 for monitoring structural integrity determines whether an outlier is found in the measurement values for each measurement point measured with low spatial resolution.

The structure integrity monitoring apparatus 100 may determine an outlier discovery section including a measurement point where the calculated difference value exceeds a preset threshold value as a rough damage section.

In step S240 , when an outlier is found, the structure integrity monitoring apparatus 100 obtains a measurement value for each measurement point measured with high spatial resolution in a monitoring section where the outlier is found.

That is, the structure health monitoring device 100 controls the distributed fiber optic sensor device 200 to measure the outlier discovery section with high spatial resolution, and then discovers the anomaly measured with high spatial resolution from the distributed fiber optic sensor device 200. It is possible to obtain measurement values for each measurement point of the section.

For example, as shown in FIG. 7 , the distributed optical fiber sensor device 200 can perform measurement with high spatial resolution using a random-accessibility function that measures at an arbitrary measurement point. .

In step S250, the structure integrity monitoring apparatus 100 detects an outlier among measurement values for each measurement point measured with high spatial resolution and calculates a damage location.

That is, referring to FIG. 8 , the structure integrity monitoring apparatus 100 calculates a difference value between the obtained measurement value for each measurement point of the outlier discovery section and the high spatial resolution reference value, and the calculated difference value exceeds a preset threshold value. It is possible to detect an outlier by checking whether or not the difference value is an outlier, and the measurement point where the difference value is determined to be an outlier can be calculated as the final damage location.

For example, the apparatus 100 for monitoring structure integrity may perform anomaly detection using a median absolute deviation (MAD) algorithm with respect to the calculated difference value for each measurement point.

In addition, the structure health monitoring device 100 may notify the manager of the structure to be monitored 10 of the calculated damage location.

For example, the apparatus 100 for monitoring structure integrity may include a wired/wireless communication means, and may transmit a monitoring message including a calculated damage location to a manager's terminal through the provided communication means.

In this way, the structure health monitoring device 100 can minimize the time required for measurement and the required computational resources by measuring the entire monitoring section of the structure to be monitored 10 with low spatial resolution, Accurate damage location can be calculated by measuring the damage expected section at any location with high spatial resolution. Through this, the structure integrity monitoring device 100 performs efficient and highly accurate monitoring within limited resources and can be effectively applied to objective and various unknown damage types, and in addition to detecting damage to structures, leakage of pipelines or dams It can also be expanded to capture temperature changes due to temperature changes, and it can be possible to make decisions about efficient maintenance plans, repair and reinforcement periods and methods during the life cycle of infrastructure.

9 is a diagram schematically illustrating the configuration of a structure health monitoring device according to an embodiment of the present invention.

Referring to FIG. 9 , a structure health monitoring apparatus 100 according to an embodiment of the present invention includes a processor 110, a memory 120, a communication unit 130, and an interface unit 140.

The processor 110 may be a CPU or a semiconductor device that executes processing instructions stored in the memory 120 .

Memory 120 may include various types of volatile or non-volatile storage media. For example, memory 120 may include ROM, RAM, and the like.

For example, the memory 120 may store instructions for performing a structure health monitoring method according to an embodiment of the present invention.

The communication unit 130 is a means for transmitting and receiving data with other devices through a communication network.

The interface unit 140 may include a network interface and a user interface for accessing a network.

On the other hand, the components of the above-described embodiment can be easily grasped from a process point of view. That is, each component can be identified as each process. In addition, the process of the above-described embodiment can be easily grasped from the viewpoint of components of the device.

In addition, the technical contents described above may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program commands recorded on the medium may be specially designed and configured for the embodiments or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. - includes hardware devices specially configured to store and execute program instructions, such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter, as well as machine language codes such as those produced by a compiler. A hardware device may be configured to act as one or more software modules to perform the operations of the embodiments and vice versa.

The embodiments of the present invention described above have been disclosed for illustrative purposes, and those skilled in the art having ordinary knowledge of the present invention will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions will be considered to fall within the scope of the following claims.

10: Structures to be monitored
100: structure health monitoring device
110: processor
120: memory
130: communication department
140: interface unit
200: Distributed optical fiber sensor device
210: optical fiber cable for measurement

Claims (6)

In the structure health monitoring method performed by a structure health monitoring device that obtains the measured value from a distributed optical fiber sensor device that calculates the measured value through an optical fiber cable for measurement installed along the monitoring section of the structure to be monitored,
generating a reference value by obtaining measurement values of an initial state of the structure to be monitored, measured with a preset low-fidelity reference and a preset high-fidelity reference;
Obtaining a measurement value for each first measurement point measured with the low spatial resolution, and monitoring the structure to be monitored with the low spatial resolution using the obtained measurement value for each first measurement point and the reference value. ;
obtaining a second measurement value measured with the high spatial resolution in a section in which the outlier is found, when an outlier is found among the obtained measurement values for each first measurement point as a result of the monitoring; and
and calculating a damage location by detecting an outlier among the obtained measurement values for each second measurement point.
According to claim 1,
The step of generating the reference value,
The structure integrity monitoring method, characterized in that for generating a low spatial resolution reference value and a high spatial resolution reference value measured for each of the low spatial resolution and the high spatial resolution.
According to claim 2,
The step of performing the monitoring is,
After the distributed optical fiber sensor device is controlled to measure with the low spatial resolution, a measurement value for each first measurement point is periodically obtained from the distributed optical fiber sensor device, and the obtained measurement value for each first measurement point The structure integrity monitoring method, characterized in that for detecting an outlier by calculating a difference value between the low spatial resolution reference value and checking whether the calculated difference value exceeds a preset threshold value.
According to claim 3,
The step of obtaining the measured value for each second measurement point,
After controlling the distributed optical fiber sensor device to measure the section in which the outlier is found with the high spatial resolution, the structure integrity monitoring characterized in that the measurement value for each second measurement point is obtained from the distributed optical fiber sensor device. method.
According to claim 4,
The step of calculating the damage location,
A difference value between the measured value for each second measurement point and the high spatial resolution reference value is calculated, and an outlier is detected by checking whether the calculated difference value exceeds a preset threshold value, and a measurement point determined as the outlier value is determined. Structure integrity monitoring method, characterized in that for calculating as the damage location.
In the structure health monitoring device for obtaining the measured value from a distributed optical fiber sensor device that calculates the measured value through an optical fiber cable for measurement installed along the monitoring section of the structure to be monitored,
memory for storing instructions; and
Including a processor that executes the instructions,
The command is
generating a reference value by obtaining measurement values of an initial state of the structure to be monitored, measured with a preset low-fidelity reference and a preset high-fidelity reference;
Obtaining a measurement value for each first measurement point measured with the low spatial resolution, and monitoring the structure to be monitored with the low spatial resolution using the obtained measurement value for each first measurement point and the reference value. ;
obtaining a second measurement value measured with the high spatial resolution in a section in which the outlier is found, when an outlier is found among the obtained measurement values for each first measurement point as a result of the monitoring; and
A structure integrity monitoring device characterized in that performing a structure integrity monitoring method comprising the step of calculating a damage location by detecting an outlier among the obtained measurement values for each second measurement point.

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