Ruiya Li

A Diaphragm Type Fiber Bragg Grating Vibration Sensor Based on Transverse Property of Optical Fiber With Temperature Compensation

This paper has presented a novel diaphragm-type fiber Bragg grating (FBG) vibration sensor with a small mass and an excellent sensitivity through the use of the transverse property of a tightly suspended optical fiber with two fixed ends. Two suspended optical fibers that were embedded with an FBG element each, have been arranged symmetrically along the both sides of the diaphragm in a parallel manner, and their middle points were connected with the two surfaces of the mass by rigid thin rods to sense vibration. The theoretical model of the presented sensor has been derived, and its sensing characteristics have been analyzed by numerical simulation to determine the physical parameters. Experiments have been conducted to show that its sensitivity is 31.25 pm/g within a working bandwidth range of 10~150 Hz. The linearity and relative sensitivity errors are 2.21% and ±10%, respectively. The experimental resonant frequency of 300 Hz is consistent with the theoretical value, which has verified the effectiveness of the proposed theoretical model. The temperature response of this sensor has decreased to 1.32 pm/°C in the range of 30~90°C after implementing the temperature compensation. Compared with the existing diaphragm-enabled FBG vibration sensors, the proposed sensor enables to support the easy implementation of distributed measurement, and the small mass allows for detection on mass-sensitive structures.

A temperature-independent force transducer using one optical fiber with multiple Bragg gratings

Typical electrical or piezoelectric force sensors may fail in the industrial applications with strong electromagnetic interference (EMI). To address this issue, this paper develops a new temperature-independent force transducer based on theories of elastic cantilever beam and Bragg wavelength shift in fiber Bragg gratings. The detailed design of the structure and theoretical analysis are given to introduce the measurement principle of the transducer and temperature compensation of fiber Bragg gratings (FBG). Extensive experiments have been conducted to evaluate the performance of the developed force transducer. Experimental results demonstrate that the developed FBG force transducer has a force sensitivity 84.43 pm/kN within a measured range from 0 to 50 kN, which is consistent with the theoretical sensitivity 87.77 pm/kN. Moreover, experimentally the transducer also achieves good linearity, repeatability and temperature independency. The developed force transducer can assist in monitoring the states of heavy-duty machines in the harsh industrial environment.

Application of Embedded Fiber Bragg Grating (FBG) Sensors in Monitoring Health to 3D Printing Structures

The 3D printing technology is known as a core technology in the third industrial revolution. The 3D printing structures are more popular and used as key components of products, so that monitoring health of 3D printing structures is particularly important. Moreover, the fiber Bragg grating (FBG) sensing technology is a new type of sensing technology, and FBG sensors have its unique advantages so that they have great application prospects in monitoring health of structures. FBG sensors were embedded inside a 3D printing structure, which strain variation is monitored by the FBG sensors during the loading process in this paper. Comparison was carried out between the measured and theoretical results to investigate thoroughly validity and reliability of the embedded FBG sensors for monitoring health of the 3D printing structure. Test results show that the embedded FBG sensors may be utilized to effectively monitor the strain variation of the 3D printing structure during the loading process; the measured and theoretical results show a good agreement and the straightness may be up to above 0.9998, so that the reliability is very good. Our results can also be guidance for monitoring health of 3D print structures.

Sensitivity Enhancement of FBG-Based Strain Sensor

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments.

A Diaphragm-Type Highly Sensitive Fiber Bragg Grating Force Transducer With Temperature Compensation

This paper presents a novel diaphragm-type fiber Bragg grating (FBG) force transducer with a high sensitivity through combining the axial property of the optical fiber and the transverse property of a circular diaphragm. The theoretical model of the presented sensor was derived, and its sensing characteristics were analyzed by numerical simulation and finite element analysis. A specimen of this type of sensor was manufactured with a 0.6mm-thickness diaphragm and a 0.1-ratio of the radius of the hard core and the outer radius of the diaphragm. Experiments were conducted to show that its experimental force sensitivity 441.84 pm/N was consistent with the theoretical value 422.4 pm/N within a working range of 0~4.9 N, which verified the effectiveness of the proposed theoretical model. Moreover, experimentally the designed transducer provided a broad flat frequency range from 0 to 200 Hz and a dynamic resolution of 0.15 mN

A Fiber Bragg Grating Based Torsional Vibration Sensor for Rotating Machinery

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Research on the Multiple Factors Influencing Human Identification Based on Pyroelectric Infrared Sensors

(Hz−0.5). The temperature cross-sensitivity of this sensor was suppressed effectively in the range of 16.7 °C~53.6 °C after implementing the temperature compensation. Compared with the existing FBG force sensors, the proposed sensor provided higher and more easily adjustable sensitivity.

Study on embedding fiber Bragg grating sensor into the 3D printing structure for health monitoring

This paper proposes a new type of torsional vibration sensor based on fiber Bragg grating (FBG). The sensor has two mass ball optical fiber systems. The optical fiber is directly treated as an elastomer and a mass ball is fixed in the middle of the fiber in each mass ball fiber system, which is advantageously small, lightweight, and has anti-electromagnetic interference properties. The torsional vibration signal can be calculated by the four FBGs’ wavelength shifts, which are caused by mass balls. The difference in the two sets of mass ball optical fiber systems achieves anti-horizontal vibration and anti-temperature interference. The principle and model of the sensor, as well as numerical analysis and structural parameter design, are introduced. The experimental conclusions show that the minimum torsional natural frequency of the sensor is 27.35 Hz and the torsional vibration measurement sensitivity is 0.3603 pm/(rad/s2).

Distributed deformation measurement of large space deployable mechanism based on FBG sensors

Analysis of the multiple factors affecting human identification ability based on pyroelectric infrared technology is a complex problem. First, we examine various sensed pyroelectric waveforms of the human body thermal infrared signal and reveal a mechanism for affecting human identification. Then, we find that the mechanism is decided by the distance, human target, pyroelectric infrared (PIR) sensor, the body type, human moving velocity, signal modulation mask, and Fresnel lens. The mapping relationship between the sensed waveform and multiple influencing factors is established, and a group of mathematical models are deduced which fuse the macro factors and micro factors. Finally, the experimental results show the macro-factors indirectly affect the recognition ability of human based on the pyroelectric technology. At the same time, the correctness and effectiveness of the mathematical models is also verified, which make it easier to obtain more pyroelectric infrared information about the human body for discriminating human targets.

An FBG-Based 2-D Vibration Sensor With Adjustable Sensitivity

3D printing technology is a rapidly developing manufacturing technology, which is known as a core technology in the third industrial revolution. With the continuous improvement of the application of 3D printing products, the health monitoring of the 3D printing structure is particularly important. Fiber Bragg grating (FBG) sensing technology is a new type of optical sensing technology with unique advantages comparing to traditional sensing technology, and it has great application prospects in structural health monitoring. In this paper, the FBG sensors embedded in the internal structure of the 3D printing were used to monitor the static and dynamic strain variation of 3D printing structure during loading process. The theoretical result and experimental result has good consistency and the characteristic frequency detected by FBG sensor is consistent with the testing results of traditional accelerator in the dynamic experiment. The results of this paper preliminary validate that FBG embedded in the 3D printing structure can effectively detecting the static and dynamic stain change of the 3D printing structure, which provide some guidance for the health monitoring of 3D printing structure.