FBG Sensor for Rotation Speed Measurement With Large Sensing Distance Based on Terfenol-D

The rotation speed of revolved mechanisms is one of the critical parameters for characterizing mechanical health conditions, fault diagnosis, and maintenance strategy. This article studies a fiber Bragg grating (FBG) sensor for rotation speed measurement based on Terfenol-D, which generates a rotating magnetic field through a magnet fixed on a rotating structure. Terfenol-D material undergoes magnetostriction with the rotating magnetic field. The FBG sensor fixed on Terfenol-D monitors the rotation speed of the rotating mechanism by inducing the strain of Terfenol-D. The sensor principle is theoretically analyzed in this article, and finite-element simulations are performed on the space magnetic field distribution of the sensor. According to the results, the variation law of the central wavelength of the sensor grating is qualitatively derived. Then, the orthogonal tests are performed with the sensing distance from 2 to 10 cm and the rotation speed from 1 to 50 r/s. The experimental results are compatible with the theoretical analysis. The results show that the sensor can accurately measure the rotation speed at a sensing distance of 10 cm, which makes the sensor have a more flexible installation position. The sensor has good operation performance within experimental conditions.