Fiber Bragg Grating Sensor Technology Research Articles

FBG and BOTDA Based Monitoring of Mine Pressure Under Remaining Coal Pillars Using Physical Modeling.

Strong mine pressure often emerges when the working face of the lower coal seam in a closely spaced coal seam system passes through the remaining coal pillar in the overlying goaf. This study investigates the law of overburden movement and the manifestation of mine pressure during mining under the remaining coal pillar. A physical model measuring 2.5 × 0.2 × 1.503 m is constructed. Fiber Bragg grating sensing technology (FBG) and Brillouin optical time domain analysis technology (BOTDA) are employed in the physical model experiment to monitor the internal strain of the overlying rock as the working face advances. This study determines the laws of overlying rock fracture and working face pressure while mining coal seams beneath the remaining coal pillar. It analyzes the relationship between the pressure at the working face and the strain characteristics of the horizontally distributed optical fiber. A fiber grating characterization method is established for the stress evolution law of overlying rock while passing the remaining coal pillar. The experimental results indicated that the fracture angle of overlying rock gradually decreases during the mining stage through and after the coal pillar. In the mining stage through the coal pillar, the cycle pressure step distance of the working face is reduced by 33.3% compared to the stage after mining through the coal pillar. Initially, the strain pattern of the horizontal optical fiber is unimodal when pressure is first applied to the working face, and it transitions from unimodal to bimodal during periodic pressure. The peak value of fiber Bragg grating compressive strain and the range of influence of advanced support pressure are 3.6 times and 4.8 times, respectively, before passing through the remaining coal pillar. Finally, the accuracy of the FBG characterization method is verified by comparing it to the monitoring curve of the coal seam floor pressure sensor. The research results contribute to applying fiber optic sensing technology in mining physical model experiments.

Advanced data-driven FBG sensor-based pavement monitoring system using multi-sensor data fusion and an unsupervised learning approach

Pavement health monitoring and assessment using sensor technology provides valuable insights into the condition of roads and helps in effective maintenance and management. This paper presents an advanced fiber Bragg grating (FBG) sensor-based pavement monitoring system that leverages multi-sensor data fusion techniques and an unsupervised learning approach for enhanced structural health assessment. The study commences with the fusion of data from various FBG sensors based on specific considerations and employing a novel function to improve the accuracy of pavement condition assessment. A dedicated data management system is introduced to address the challenges associated with continuous monitoring. This system automates data organization, pre-processing, and storage, facilitating historical trend analysis and post-processing. Then, the research introduces a novel unsupervised learning approach utilizing the density-based spatial clustering of applications with noise (DBSCAN) algorithm. This algorithm identifies abnormal patterns in the FBG sensor data, which may indicate structural anomalies or unexpected events, aiding the operator by automatically flagging abnormal data. By incorporating principle component analysis (PCA)-based feature fusion, the system reduces the dimensionality of the data, which enhances the efficiency of the clustering process. Various anomalies were detected in the data collected for four months from the test track. The cause and relevance of these anomalies were assessed to facilitate informed decision-making. This approach enables the operator to achieve early detection of potential structural issues and distinguish abnormal damage data from other anomalous data, thereby contributing to the overall success of the pavement monitoring system. In conclusion, the integration of advanced FBG sensor technology with multi-sensor data fusion and unsupervised learning techniques results in a sophisticated and robust pavement monitoring system. The presented approach enhances accuracy by detecting anomalies at any strain level, computational time using multi-sensor data fusion, and reliability of structural health assessment through anomaly evaluation. It also provides a framework for proactive decision-making, ultimately improving the longevity and structural integrity of critical infrastructure.

Enhancing Consumer Electronics in Healthcare 4.0: Integrating Passive FBG Sensor and IoMT Technology for Remote HRV Monitoring

Enhancing Consumer Electronics in Healthcare 4.0: Integrating Passive FBG Sensor and IoMT Technology for Remote HRV Monitoring

Dynamic Feature Identification of Carbon-Fiber-Reinforced Polymer Laminates Based on Fiber Bragg Grating Sensing Technology

Carbon-fiber-reinforced polymer (CFRP) composites have many advantages, and have been widely used in aerospace structures, buildings, bridges, etc. The analysis of dynamic response characteristics of CFRP composite structures is of great significance for promoting the development of smart composite structures. For this reason, vibration experiments of CFRP laminates with surface-attached fiber Bragg grating (FBG) sensors under various dynamic loading conditions were carried out. Time- and frequency-domain analyses were conducted on the FBG testing signals to check the dynamic characteristics of the CFRP structure and the sensing performance of the installed sensors. The results show that the FBG sensors attached to the surface of the CFRP laminates can accurately measure the dynamic response and determine the excited position of the CFRP laminates, as well as invert the strain distribution of the CFRP laminates through the FBG sensors at different positions. By performing Fourier transform, short-time Fourier transform, and frequency domain decomposition (FDD) on the FBG sensing signals, the time–frequency information and the first eight modal frequencies of the excited CFRP structure can be obtained. The modal frequencies obtained by different excitation types are similar, which can be used for structural damage identification. The research in this paper clarifies the effectiveness and accuracy of FBG sensors in sensing the dynamic characteristics of CFRP structures, which can be used for performance evaluation of CFRP structures and will effectively promote the design and development of intelligent composite material structures.

FBG Sensing Technology for an Enhanced Microgrid Performance

Energy provided by microgrids should be considered, especially because their purpose is to supply loads from the available power source of the combined sources of energy, including the grid, optimally and efficiently to satisfy the load demand securely and economically. Sensing the accuracy of the different physical parameters of the combined power sources and energy storage plays a crucial part in the efficiency and resilience of microgrids. The present microgrids mostly use conventional sensors, which are greatly impacted by ambient conditions such as high-voltage (HV) and electromagnetic interference (EMI). So, this paper presents an enhanced microgrid based on replacing the conventional sensors with fiber Bragg grating (FBG) sensors renowned for their immunity to EMI and HV, in addition to the virtue of distributing sensing capability. The enhanced microgrid based on FBG sensing was tested experimentally at different potential points predefined on the microgrid and validated with a microgrid simulation model. Real-time measurements of FBG and conventional sensors were recorded at the potential points and applied to the Simulink model to compare the performance for both cases. The unit and integration tests showed an obvious improvement in the accuracy and resiliency of the microgrid by using FBG sensors.

Research on Three-Dimensional Stress Monitoring Method of Surrounding Rock Based on FBG Sensing Technology.

Research on the stress state of rock mass is essential for revealing the distribution characteristics and evolution law of the surrounding rock stress field in the roadway, studying the coal–rock dynamic disaster and the design of roadway support. This thesis proposes a three-dimensional stress monitoring method for surrounding rocks based on fiber Bragg grating (FBG) sensing technology and a cube-shaped three-dimensional stress fiber grating sensor is developed based on the principle of this monitoring method. According to the fiber grating strain obtained by numerical simulation, the calculated three-dimensional stress value is basically consistent with the theoretical value. The margin of error was plus or minus one percentage point. The sensing performance of the sensor was tested using a uniaxial compression experiment instead of a triaxial compression experiment. The experimental results show that in the range of 0~50 Mpa, the sensor’s sensitivity to X, Y and Z axis stress is 25.51, 25.97 and 24.86 pm/Mpa, respectively. The relative error of measured stress is less than 4%. Meanwhile, the sensor has good linearity and repeatability, and has broad application prospects in the field of underground engineering safety monitoring such as in coal mines and tunnels.

Load Transfer Law of Anti-Floating Anchor With GFRP Bars Based on Fiber Bragg Grating Sensing Technology

The glass fiber-reinforced polymer (GFRP) anchor, a new type of composite material anchor, has been widely used in foundation engineering of coastal areas. This study investigated the feasibility of applying the fiber Bragg grating (FBG) sensing technology to monitor the strain of the GFRP anchor during the pull test. Based on an advanced method, the FBG strain sensors were installed in GFRP anchors during the anchor manufacturing process. Then, GFRP anchors were installed into the pre-created borehole with an M30 cement mortar. Meanwhile, the FBG temperature sensors were installed next to the GFRP anchors to monitor the temperature change during the test. The axial force and average shear stress of GFRP anchors along depth during the pull test were analyzed, and the influence of temperature change on strain measurement was studied. The test results showed that the FBG sensing technology and the installation method of FBG strain sensors used in the test were feasible to monitor the mechanical properties of the GFRP anchor during the pull test. Moreover, the effect of temperature change on strain monitoring of FBG strain sensors was negligible.

Monitoring rock bolt safety based on FBG sensors

A good bolt support structure effectively enhances the strength of the surrounding rock. Bolt support monitoring provides a basis for modifying and improving the design of this structure and enables safety hazards to be identified so that safe production can continue. A bolt fiber Bragg grating (FBG) stress sensor is developed based on FBG sensor technology, providing a data-driven analysis tool for monitoring the bolt stress in the working face. Continuous dynamic monitoring of the internal force distribution in a high-precision roadway bolt support structure is achieved through strict laboratory calibration, thus enabling comprehensive safety monitoring. Furthermore, the anchor FBG stress sensor is used to analyze the real-time stress variations in a bolt support structure during excavation. The results reveal the security evolution characteristics of bolts buried in shallow bedrocks and show that the security state varies with location (i.e., the roof, roadside, apex between roof and roadside, and apex between roadside and floor) and depth.

Application of Fiber Bragg Grating Sensing Technology in the Health Monitoring of Special-Shaped Structures

Application of Fiber Bragg Grating Sensing Technology in the Health Monitoring of Special-Shaped Structures

Determination of the calibration equation for FBG temperature sensors

This paper presents a brief introduction to FBG sensor technology and its applications. Then the procedure for determining the sensor calibration equations is presented. These equations are determined for each individual sensor and are necessary to perform the trans-oceanographic measurement of the FBG sensor's wavelength variation in the measured parameter

Application of Fiber Bragg Grating Sensor Technology to Leak Detection and Monitoring in Diaphragm Wall Joints: A Field Study.

Joints between diaphragm wall panels are weak spots in wall construction. It is essential that potential leak sites are detected prior to excavation. In this study, a novel leak detection and monitoring system is presented that is based on fiber Bragg grating (FBG) sensing technology. A field study was performed in a deep excavation supported by diaphragm walls (in Hohhot, China) to validate the feasibility and effectiveness of the proposed method. Two schemes were trialed; one using pipes made of stainless steel, and one used a pipeless method. The results of the field study are presented and discussed. They show that potential leak sites in the wall joints could be determined prior to excavation using the proposed detection method. Stainless steel is a good material to use to make the detection tube because it can protect the FBG sensors and heating belts from damage and is more sensitive to water leakage. The field study provides good evidence for the feasibility of the new detection system. It also provides valuable experience for the field application of the system and has generated useful data to use in follow-up work.

Experimental and numerical simulation investigation on vortex-induced vibration test system based on bare fiber Bragg grating sensor technology for vertical riser

Abstract The Vortex-Induced Vibration (VIV) test system on deepwater riser based on Bare Fiber Bragg Grating (BFBG) sensor technology was designed. Meanwhile, a riser VIV response numerical model was established based on the work-energy principle. The results show that the first-order vibration frequency dominates the vibration of the riser, and as the velocity increases, the dominant frequency of the riser gradually increases under the effect of different top tensions. At the same velocity, as the top tension increases step by step, the dominant frequency and fatigue damage at the same position along the axial length of the riser both gradually decreases. The model test and numerical simulation show a relatively consistent change, maintaining a high degree of agreement. The process control system based on BFBG of model test has excellent performance, and FBG sensors have great advantages in VIV test of a vertical riser in water.

Permanent Deformation and Temperature Monitoring of Subgrades Using Fiber Bragg Grating Sensing Technology

The hidden nature of subgrades makes the effective monitoring of their deformation very difficult. This paper addresses this issue by proposing the use of fiber Bragg grating (FBG) sensing technology. Here, an FBG is encapsulated within a monitoring tube formed from a polyvinyl chloride tube, and one end of the monitoring tube is fixed perpendicular to a concrete column, forming a cantilever beam monitoring system. The deformation is assessed according to the theoretical relationship between the horizontal strain on the FBG embedded in the monitoring tube and the vertical displacement of the cantilever beam. Then, the relationship between the variation in the wavelength of light reflected by the encapsulated FBG and the temperature and horizontal strain is obtained on this basis by calibration experiments. The monitoring tubes are buried at a proscribed depth below the top surface of the subgrade, which facilitates the monitoring of the deformation and temperature of the subgrade at different stages of construction through the collection of FBG wavelength data during different periods, such as after embedding the monitoring tubes, the completion of the test road surface, and during the period of operation. The proposed technology is verified by employing the system to monitor the instantaneous maximum deformation and permanent deformation of a subgrade under dynamic loads. The monitoring results demonstrate that the instantaneous maximum deformation values of the subgrade at 0.25 m and 0.5 m below the surface are 695.40 μm and 574.02 μm, respectively, and the corresponding permanent deformation values are 53.00 μm and 41.54 μm, respectively. The FBG sensor system is thereby verified to provide a reliable method for conducting long‐term continuous, accurate, and efficient subgrade deformation and temperature monitoring.

Test and Study of Pipe Pile Penetration in Cohesive Soil Using FBG Sensing Technology.

In order to examine the applicability of Fiber Bragg Grating (FBG) sensing technology in the static penetration of pipe piles, static penetration tests in clay were conducted using double-wall open and closed model pipe piles. The strain was measured using FBG sensors, and the plug height was measured using a cable displacement sensor. Using one open pile and two closed piles, the difference in pipe pile penetration was compared and analyzed. Based on FBG sensing technology and the strain data, the penetration characteristics of the pipe pile, such as axial force, lateral friction, and driving resistance were examined. Results showed that FBG sensing technology has superior testing performance for the pipe pile penetration process, can accurately reflect the strain time history of pipe piles, and can clearly reflect the penetration process of pipe piles with increasing penetration depth. In addition, the variation law of the characteristics of the jacked pile pile–soil interface was obtained. This test has significance for model tests and the engineering design of pipe piles.

Application Research on the Fiber Bragg Grating Sensing Technology in Arch Dam Model Test

Fiber Bragg Grating (FBG) has the advantages of high sensitivity, high resolution, low cost and small volume. Therefore, FBG sensing technology is widely used in the monitoring of structural engineering. In this research, FBG sensing technology was applied in the geo-mechanical model test of arch dam for the first time. The geomechanical model of Lizhou arch dam was built, and the FBG sensors were arranged on the upstream dam surface, while the resistance strain gauges were arranged on the downstream dam surface. The model failure test was carried out to get the stress-strain state and its changing process of the dam body. The test results show that the monitoring results of the FBG sensors and the resistance strain gauges are basically consistent, and it is found that the initial cracking overloading safety coefficient is K 1 = 1.4 ∼ 2.2, the nonlinear deformation overloading safety coefficient is K 2 = 3.4 ∼ 4.3, the ultimate overloading safety coefficient is K 3 = 6.0 ∼ 6.6. The application of FBG technology provides a method to solve the problem that the strain of the upstream surface of the arch dam model cannot be directly monitored due to the insufficient space caused by the installation and loading system, and also provides a new idea for the measurement technology in the geo-mechanical model test.

Application of FBG Sensing Technology to Internal Deformation Monitoring of Landslide

Limited by geological survey methods, processes, and cost, it has long been a difficult thing to accurately detect the position of landslide slip surface and monitor the landslide internal deformation. Fiber Bragg grating (FBG) sensing technology has been widely used in geological engineering and geotechnical engineering due to its high‐precision property. In this research, FBG sensing technology was applied to the monitoring of landslide internal deformation in Toudu, Chongqing, China. The in situ monitoring by FBG accurately determined the position of the landslide slip surface. Based on the relationship between fiber grating strain and deflection, the formula between landslide internal deformation and fiber grating strain was obtained, and the rationality of the formula was verified by the monitoring data of surface displacement. Finally, the internal deformation at the monitoring point of the Toudu landslide was calculated and the mechanism of the landslide was analyzed.

基于光纤布拉格光栅传感技术的开口管桩贯入特性实验研究

基于光纤布拉格光栅传感技术的开口管桩贯入特性实验研究

基于光纤布拉格光栅传感技术的不同桩径静压桩贯入特性研究

基于光纤布拉格光栅传感技术的不同桩径静压桩贯入特性研究

Strain Monitoring of a Composite Drag Strut in Aircraft Landing Gear by Fiber Bragg Grating Sensors.

This work reports on the use of Fiber Bragg Grating (FBG) sensors integrated with innovative composite items of aircraft landing gear for strain/stress monitoring. Recently, the introduction of innovative structures in aeronautical applications is appealing with two main goals: (i) to decrease the weight and cost of current items; and (ii) to increase the mechanical resistance, if possible. However, the introduction of novel structures in the aeronautical field demands experimentation and certification regarding their mechanical resistance. In this work, we successfully investigate the possibility to use Fiber Bragg Grating sensors for the structural health monitoring of innovative composite items for the landing gear. Several FBG strain sensors have been integrated in different locations of the composite item including region with high bending radius. To optimize the localization of the FBG sensors, load condition was studied by Finite Element Method (FEM) numerical analysis. Several experimental tests have been done in range 0–70 kN by means of a hydraulic press. Obtained results are in very good agreement with the numerical ones and demonstrate the great potentialities of FBG sensor technology to be employed for remote and real-time load measurements on aircraft landing gears and to act as early warning systems.

Impact Localization of CFRP Structure Based on FBG Sensor Network

Low energy impact can induce invisible damage of carbon fiber reinforced polymer (CFRP). The damage can seriously affect the safety of the CFRP structure. Therefore, damage detection is crucial to the CFRP structure. Impact location information is the premise of damage detection. Hence, impact localization is the primary issue. In this paper, an impact localization system, based on the fiber Bragg grating (FBG) sensor network, is proposed for impact detection and localization. For the completed impact signal, the FBG sensor and narrow-band laser demodulation technology are applied. Wavelet packet decomposition is introduced to extract available frequency band signals and attenuate noise. According to the energy of the available frequency band signal, an impact localization model, based on the extreme learning machine (ELM), is established with the faster training speed and less parameters. The above system is verified on the 500 mm × 500 mm × 2 mm CFRP plate. The maximum localization error and the minimum localization error are 30.4 mm and 6.7 mm, respectively. The average localization error is 14.7 mm, and training time is 0.7 s. Compared with the other machine learning methods, the localization system, proposed in this paper, has higher accuracy and faster training speed. This paper provides a practical system for impact localization of the CFRP structure.