Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Fir...Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Firstly,structural design of the tilt sensor was conducted based on static mechanics principles.By positioning the FBG away from the beam’s neutral axis,linear strain enhancement in the FBG was achieved,thereby improving sensor sensitivity.The relationship between FBG strain,applied force,and the offset distance from the neutral axis was established,determining the optimal distance corresponding to maximum strain.Based on this optimization scheme,a prototype of the tilt sensor was designed,fabricated,and experimentally tested.Experimental results show that the FBG offset distance yielding maximum sensitivity is 4.4 mm.Within a tilt angle range of−30°to 30°,the sensor achieved a sensitivity of 129.95 pm/°and a linearity of 0.9997.Compared to conventional FBG-based tilt sensors,both sensitivity and linearity were significantly improved.Furthermore,the sensor demonstrated excellent repeatability(error<0.94%),creep resistance(error<0.30%),and temperature stability(error<0.90%).These results demonstrate the sensor’s excellent potential for SHM applications.The sensor has been successfully deployed in an underground pipeline project,conducting long-term monitoring of tilt and deformation in the steel support structures,further proving its value for engineering safety monitoring.展开更多
In this paper,a high-sensitivity fiber Bragg grating(FBG)tilt sensor using a cantilever-based structure is introduced.Two FBGs are fixed on a specially designed elastomer.One end of the elastomer is connected to the m...In this paper,a high-sensitivity fiber Bragg grating(FBG)tilt sensor using a cantilever-based structure is introduced.Two FBGs are fixed on a specially designed elastomer.One end of the elastomer is connected to the mass block,and the other end is connected to the shell.The principle of the tilt sensor is introduced in detail,and the mathematical model is established.The performance of the sensor is studied.The results show that there is a good linear relationship between the central wavelength difference of the two FBGs and the tilt angle in the range of-5°to 5°.The repeatability of the sensor is good,and the tilt sensitivity can reach 231.7 pm/°.The influence of the silicone oil on the damping capacity of the sensor is studied.The results show that the damping capacity of the sensor has been improved by sealing the silicone oil inside the shell of the sensor.The field test is carried out on a pier of an elevated bridge,and the result is good,which verifies the practicability of the sensor.展开更多
A tilt sensor based on an intermodal photonic crystal fiber （PCF） interferometer is demonstrated. The sensor consists of a tubular filled with NaC1 aqueous solutions and an intermodal PCF interferometer, which is fo...A tilt sensor based on an intermodal photonic crystal fiber （PCF） interferometer is demonstrated. The sensor consists of a tubular filled with NaC1 aqueous solutions and an intermodal PCF interferometer, which is formed by using a short PCF with two single-mode fibers （SMFs） spliced at both ends, and the air-holes in the splice regions are fully collapsed. The intermodal PCF interferometer is fixed in a rigid glass tubular with a slant orientation, and a half of the PCF is immersed in the NaC1 aqueous solutions, while the other half is exposed in air. When tilting the tubular, the length of the PCF immersed changes so that the transmission spectrum moves. Therefore, by monitoring the wavelength shift, the tilt angle can be achieved. In the experiment, a 0.8-cm-length intermodal PCF interferometer was adopted. The sensitivity of the proposed sensor was obtained from - 1.5461 nm/° to -30.1244 nm/° when measuring from -35.1 ° to 37.05°.展开更多
Although there are some multi-sensor methods for measuring the straightness and tilt errors of a linear slideway, they need to be further improved in some aspects, such as suppressing measurement noise and reducing pr...Although there are some multi-sensor methods for measuring the straightness and tilt errors of a linear slideway, they need to be further improved in some aspects, such as suppressing measurement noise and reducing precondition.In this paper, a new four-sensor method with an improved measurement system is proposed to on-machine separate the straightness and tilt errors of a linear slideway from the sensor outputs, considering the influences of the reference surface profile and the zero-adjustment values. The improved system is achieved by adjusting a single sensor to di erent positions. Based on the system, a system of linear equations is built by fusing the sensor outputs to cancel out the e ects of the straightness and tilt errors. Three constraints are then derived and supplemented into the linear system to make the coe cient matrix full rank. To restrain the sensitivity of the solution of the linear system to the measurement noise in the sensor outputs, the Tikhonov regularization method is utilized. After the surface profile is obtained from the solution, the straightness and tilt errors are identified from the sensor outputs. To analyze the e ects of the measurement noise and the positioning errors of the sensor and the linear slideway, a series of computer simulations are carried out. An experiment is conducted for validation, showing good consistency. The new four-sensor method with the improved measurement system provides a new way to measure the straightness and tilt errors of a linear slideway, which can guarantee favorable propagations of the residuals induced by the noise and the positioning errors.展开更多
The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive...The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive single-mode telecommunication grade fibre. The fibre section with TFBG is then coupled to the evaluation fibre circuit with the cladding-core mode conversion element that provides the core re-coupling of the optical power injected by TFBG to the fibre cladding. The cladding-core mode conversion efficiency is sensitive to the acceleration generated fibre bending. It is shown that the sensitivity of the device depends on the rate of the main core reflection versus cladding ghost reflection induced by the grating. The analysis of the core reflection power coupling on the angle of the grating tilt and the analysis of the cladding ghost reflection power coupling on the angle of the grating tilt is presented and the optimal parameters of the tilt and refractive index modulation are derived. The presentation gives the experimental results of the TFBG sensor prepared according to the optimization process.展开更多
a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respe...a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.展开更多
文摘Aiming at the requirement for high-precision tilt monitoring in the field of structural health monitoring(SHM),this paper proposes a sensitivity-enhanced tilt sensor based on a femtosecond fiber Bragg grating(FBG).Firstly,structural design of the tilt sensor was conducted based on static mechanics principles.By positioning the FBG away from the beam’s neutral axis,linear strain enhancement in the FBG was achieved,thereby improving sensor sensitivity.The relationship between FBG strain,applied force,and the offset distance from the neutral axis was established,determining the optimal distance corresponding to maximum strain.Based on this optimization scheme,a prototype of the tilt sensor was designed,fabricated,and experimentally tested.Experimental results show that the FBG offset distance yielding maximum sensitivity is 4.4 mm.Within a tilt angle range of−30°to 30°,the sensor achieved a sensitivity of 129.95 pm/°and a linearity of 0.9997.Compared to conventional FBG-based tilt sensors,both sensitivity and linearity were significantly improved.Furthermore,the sensor demonstrated excellent repeatability(error<0.94%),creep resistance(error<0.30%),and temperature stability(error<0.90%).These results demonstrate the sensor’s excellent potential for SHM applications.The sensor has been successfully deployed in an underground pipeline project,conducting long-term monitoring of tilt and deformation in the steel support structures,further proving its value for engineering safety monitoring.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2019 Ⅲ 158CG)the National Natural Science Foundation of China(Grant No.61875155).
文摘In this paper,a high-sensitivity fiber Bragg grating(FBG)tilt sensor using a cantilever-based structure is introduced.Two FBGs are fixed on a specially designed elastomer.One end of the elastomer is connected to the mass block,and the other end is connected to the shell.The principle of the tilt sensor is introduced in detail,and the mathematical model is established.The performance of the sensor is studied.The results show that there is a good linear relationship between the central wavelength difference of the two FBGs and the tilt angle in the range of-5°to 5°.The repeatability of the sensor is good,and the tilt sensitivity can reach 231.7 pm/°.The influence of the silicone oil on the damping capacity of the sensor is studied.The results show that the damping capacity of the sensor has been improved by sealing the silicone oil inside the shell of the sensor.The field test is carried out on a pier of an elevated bridge,and the result is good,which verifies the practicability of the sensor.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 61108058, the National Basic Research Program of China （973 Program） under Grant No. 2010CB327804, the Zhejing Province Intemational Science and Technoloty Cooperation Special Programme under Grant No. 2013C24018, the National Key Technology R＆D Program 2011BAF06B02 and the Science and Technology Commission of Shanghai Municipality of China under Grant No. 10595812300. Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, medium, provided the original credited. and reproduction in any author（s） and source are
文摘A tilt sensor based on an intermodal photonic crystal fiber （PCF） interferometer is demonstrated. The sensor consists of a tubular filled with NaC1 aqueous solutions and an intermodal PCF interferometer, which is formed by using a short PCF with two single-mode fibers （SMFs） spliced at both ends, and the air-holes in the splice regions are fully collapsed. The intermodal PCF interferometer is fixed in a rigid glass tubular with a slant orientation, and a half of the PCF is immersed in the NaC1 aqueous solutions, while the other half is exposed in air. When tilting the tubular, the length of the PCF immersed changes so that the transmission spectrum moves. Therefore, by monitoring the wavelength shift, the tilt angle can be achieved. In the experiment, a 0.8-cm-length intermodal PCF interferometer was adopted. The sensitivity of the proposed sensor was obtained from - 1.5461 nm/° to -30.1244 nm/° when measuring from -35.1 ° to 37.05°.
基金Supported by National Natural Science Foundation of China(Grant No.51435006)
文摘Although there are some multi-sensor methods for measuring the straightness and tilt errors of a linear slideway, they need to be further improved in some aspects, such as suppressing measurement noise and reducing precondition.In this paper, a new four-sensor method with an improved measurement system is proposed to on-machine separate the straightness and tilt errors of a linear slideway from the sensor outputs, considering the influences of the reference surface profile and the zero-adjustment values. The improved system is achieved by adjusting a single sensor to di erent positions. Based on the system, a system of linear equations is built by fusing the sensor outputs to cancel out the e ects of the straightness and tilt errors. Three constraints are then derived and supplemented into the linear system to make the coe cient matrix full rank. To restrain the sensitivity of the solution of the linear system to the measurement noise in the sensor outputs, the Tikhonov regularization method is utilized. After the surface profile is obtained from the solution, the straightness and tilt errors are identified from the sensor outputs. To analyze the e ects of the measurement noise and the positioning errors of the sensor and the linear slideway, a series of computer simulations are carried out. An experiment is conducted for validation, showing good consistency. The new four-sensor method with the improved measurement system provides a new way to measure the straightness and tilt errors of a linear slideway, which can guarantee favorable propagations of the residuals induced by the noise and the positioning errors.
文摘The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive single-mode telecommunication grade fibre. The fibre section with TFBG is then coupled to the evaluation fibre circuit with the cladding-core mode conversion element that provides the core re-coupling of the optical power injected by TFBG to the fibre cladding. The cladding-core mode conversion efficiency is sensitive to the acceleration generated fibre bending. It is shown that the sensitivity of the device depends on the rate of the main core reflection versus cladding ghost reflection induced by the grating. The analysis of the core reflection power coupling on the angle of the grating tilt and the analysis of the cladding ghost reflection power coupling on the angle of the grating tilt is presented and the optimal parameters of the tilt and refractive index modulation are derived. The presentation gives the experimental results of the TFBG sensor prepared according to the optimization process.
基金supported by the National 863 Program under Grant No. 2006AA01Z217the National Natural Science Foundation of China under Grant No. 60736039 and 60572018the Technological Tackle Key Problem Project of Tianjin under Grant No. 07ZCKFGX00200.
文摘a novel structure of the pure macro- bending sensor based on the tilted fiber Bragg grating （TFBG） is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.
