Fiber Bragg Grating Sensing-Based Online Torque Detection on Coupled Bending and Torsional Vibration of Rotating Shaft

This paper has presented a novel approach based on fiber Bragg grating (FBG) sensing to analyze and decouple the coupled bending and torsional vibration of a rotating shaft. The theoretical FBG-based strain detection models under pure torsional vibration and coupled bending and torsional vibration have been derived. Two FBG sensors have been attached on the opposite sides of a rotating shaft with an angle of 45° with respect to the axial direction to support the use of the proposed decoupling method and determine the decoupled bending and torsion signals. A new supporting device has been designed to protect the fiber optical rotary joint from damage under large load impact, and ensure the stable signal transmit. The calibrated sensitivity of the pasted FBGs for measuring torque is 7.02 pm/N·m. Dynamic experiments on a rotor platform under different rotating speeds have been performed to effectively decouple the bending strain and torsional strain in real time. The decoupled torque measurements have shown a close agreement with the data detected from a commercial tacho-torquemeter, which demonstrated the effectiveness of the proposed decoupling method.