Abstract
This paper presents a fiber Bragg grating (FBG) displacement sensor with high abrasion resistance for displacement monitoring of a steel spring floating slab damping track. A wedge-shaped sliding block and an equal-strength beam form a conversion mechanism to transfer displacement to the deflection of the beam, and the deflection-induced strain is exerted on two FBGs. A special linear guide rail-slider and a precision rolling bearing have been adopted onto the conversion mechanism, which turned sliding friction into rolling friction and thus significantly reduced the friction during frequent alternating displacement measuring. Sensing principle and the corresponding theoretical derivation have been demonstrated. Experiment results show that the sensor has a sensitivity of 34.32 pm/mm and a high resolution of 0.0029 mm within a measurement range of 0~90 mm. Besides, the sensor has also a good measurement capability for micro-displacement within a range of 0~3 mm. The repeatability error and hysteresis error are 1.416% and 0.323%, respectively. Good creep resistance and high abrasion resistance for alternating displacement measurement have also been presented by a performance test. These excellent performances satisfy the requirements of high precision and long-term stability in structural health monitoring for machinery equipment and civil engineering, especially in the displacement monitoring of a floating slab damping track.
Highlights
Displacement measurement is a basic and important subject in structural health monitoring (SHM)
As far as we know, the research of displacement monitoring of floating slab damping track based on fiber Bragg grating (FBG) sensors has not been reported yet
There is the defect that a photo-detector is needed for compensating the optical power fluctuation and inconvenient in multiplexing due to the utilize of the power demodulation method. To solve these issues and limitations, various structure designs and demodulation methods have been proposed by researchers to improve the performance of FBG sensors to meet the needs of practical engineering
Summary
Displacement measurement is a basic and important subject in structural health monitoring (SHM). There is the defect that a photo-detector is needed for compensating the optical power fluctuation and inconvenient in multiplexing due to the utilize of the power demodulation method To solve these issues and limitations, various structure designs and demodulation methods have been proposed by researchers to improve the performance of FBG sensors to meet the needs of practical engineering. An improved FBG displacement sensor is proposed to improve the accuracy and abrasion resistance of the displacement measurement in the application of long-term monitoring of floating slab damping track This improved structure design overcomes the defects such as the changeability of the elasticity coefficient of force-transmitting medium, and directional movement of sliding block which could bring negative influences on the measuring accuracy in the exiting design of FBG displacement sensors. The sensing principle of the designed mechanical structure have been derived, and the sensor prototype has been manufactured, installed and fully tested
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