A Novel Fiber Bragg Grating Vibration Sensor Based on Orthogonal Flexure Hinge Structure

A novel two-dimensional (2-D) fiber Bragg grating (FBG) vibration sensor based on an orthogonal flexure hinge structure has been proposed in this paper. The elastic element of this sensor which contains an inertial body, flexure hinge pair and base has been designed in small size and integrally fabricated by using wire cutting. Two FBGs are arranged in the vertical direction by two ends pasted setup to measure the vibration-induced structure displacement. The theoretical and simulation model of the FBG vibration sensor is established. The analysis shows that this structure with a 3 mm length hinge could achieve a high working frequency and low cross-interference. The dynamic characteristics of the sensor have been measured by excitation experiments. The results match the model well that the resonant frequency of the sensor in the X and Y-directions is around 1275 Hz and 1482 Hz, respectively. The third-order natural frequency of 4932 Hz, which indicates that the sensor has high torsional rigidity and strong torsional vibration resistance. The sensor has a broad flat frequency range from 20 to 800 Hz and a sensitivity 41.2/34.5 pm/g in the X/Y-direction. The cross-interference in two directions is less than 6%. The sensor has high frequency and low cross-sensitivity, which is suitable for structural health monitoring of mechanical equipment.