Whole-process monitoring of sinkhole collapse based on distributed optical fiber strain-vibration joint system and its case study in railway subgrade

Brillouin frequency shift (BFS) of distributed optical fiber sensor is extracted from the Brillouin gain spectrum (BGS), which is often characterized by Lorenz type. However, in the case of complex stress and optical fiber self damage, the BGS will deviate from Lorenz type and be asymmetric, which leads to the extraction error of BFS. In order to enhance the extraction accuracy of BFS, the Lorenz local single peak fitting algorithm was developed to fit the Brillouin gain spectrum curve, which can make the BSG symmetrical with respect to the Brillouin center frequency shift. One temperature test of a fiber-reinforced polymer (FRP) packaged sensor whose BSG curve is asymmetric was conducted to verify the idea. The results show that the local region curve of BSG processed by the developed algorithm has good symmetry, and the temperature measurement accuracy obtained by the developed algorithm is higher than that directly measured by demodulation equipment. Comparison with the reference temperature, the relative measurement error measured by the developed algorithm and BOTDA are within 4% and 8%, respectively.

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Path Planning for Autonomous Ships: A Hybrid Approach Based on Improved APF and Modified VO Methods

Journal of Marine Science and Engineering ◽

10.3390/jmse9070761 ◽

2021 ◽

Vol 9 (7) ◽

pp. 761

Author(s):

Liang Zhang ◽

Junmin Mou ◽

Pengfei Chen ◽

Mengxia Li

Keyword(s):

Path Planning ◽

Local Minimum ◽

Hybrid Approach ◽

Artificial Potential Field ◽

Whole Process ◽

International Regulations ◽

Local Path ◽

Velocity Obstacle ◽

Global And Local

In this research, a hybrid approach for path planning of autonomous ships that generates both global and local paths, respectively, is proposed. The global path is obtained via an improved artificial potential field (APF) method, which makes up for the shortcoming that the typical APF method easily falls into a local minimum. A modified velocity obstacle (VO) method that incorporates the closest point of approach (CPA) model and the International Regulations for Preventing Collisions at Sea (COLREGS), based on the typical VO method, can be used to get the local path. The contribution of this research is two-fold: (1) improvement of the typical APF and VO methods, making up for previous shortcomings, and integrated COLREGS rules and good seamanship, making the paths obtained more in line with navigation practice; (2) the research included global and local path planning, considering both the safety and maneuverability of the ship in the process of avoiding collision, and studied the whole process of avoiding collision in a relatively entirely way. A case study was then conducted to test the proposed approach in different situations. The results indicate that the proposed approach can find both global and local paths to avoid the target ship.

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Research on the Layout and Data Processing Method of Distributed Optical Fiber in Shield Tunnel Monitoring

Journal of Physics Conference Series ◽

10.1088/1742-6596/1626/1/012012 ◽

2020 ◽

Vol 1626 ◽

pp. 012012

Author(s):

Yujie Li ◽

Qiang Li ◽

Wenyong Shen ◽

Lei Meng

Keyword(s):

Optical Fiber ◽

Data Processing ◽

Processing Method ◽

Shield Tunnel ◽

Data Processing Method ◽

Tunnel Monitoring ◽

Distributed Optical Fiber

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The test effect evaluation of distributed optical fiber sensing technology applied to stress test of bored pile

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/643/1/012021 ◽

2021 ◽

Vol 643 ◽

pp. 012021

Author(s):

Long Zhang ◽

Zhenghong Liu ◽

Yongtang Yu ◽

Jianguo Zheng ◽

Xiaowei Huang ◽

...

Keyword(s):

Optical Fiber ◽

Stress Test ◽

Effect Evaluation ◽

Fiber Sensing ◽

Bored Pile ◽

Sensing Technology ◽

Optical Fiber Sensing ◽

Distributed Optical Fiber

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A Review of Recent Distributed Optical Fiber Sensors Applications for Civil Engineering Structural Health Monitoring

Sensors ◽

10.3390/s21051818 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1818

Author(s):

Mattia Francesco Bado ◽

Joan R. Casas

Keyword(s):

Structural Health Monitoring ◽

Optical Fiber ◽

Health Monitoring ◽

Optical Fiber Sensors ◽

Vibration Monitoring ◽

Fiber Sensors ◽

Structural Health ◽

Comprehensive Collection ◽

Monitoring Tools ◽

Distributed Optical Fiber

The present work is a comprehensive collection of recently published research articles on Structural Health Monitoring (SHM) campaigns performed by means of Distributed Optical Fiber Sensors (DOFS). The latter are cutting-edge strain, temperature and vibration monitoring tools with a large potential pool, namely their minimal intrusiveness, accuracy, ease of deployment and more. Its most state-of-the-art feature, though, is the ability to perform measurements with very small spatial resolutions (as small as 0.63 mm). This review article intends to introduce, inform and advise the readers on various DOFS deployment methodologies for the assessment of the residual ability of a structure to continue serving its intended purpose. By collecting in a single place these recent efforts, advancements and findings, the authors intend to contribute to the goal of collective growth towards an efficient SHM. The current work is structured in a manner that allows for the single consultation of any specific DOFS application field, i.e., laboratory experimentation, the built environment (bridges, buildings, roads, etc.), geotechnical constructions, tunnels, pipelines and wind turbines. Beforehand, a brief section was constructed around the recent progress on the study of the strain transfer mechanisms occurring in the multi-layered sensing system inherent to any DOFS deployment (different kinds of fiber claddings, coatings and bonding adhesives). Finally, a section is also dedicated to ideas and concepts for those novel DOFS applications which may very well represent the future of SHM.

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