Design and Spectral Properties of a New Displacement Senor based on an FBG Sensor and SMA Actuators

Abstract

As an important factor in-service Structure health monitoring (SHM), predictions of displacement become the basis for determining the decrease of modern aircraft and aerospace structural performance. Optical fiber Bragg grating (FBG) sensors are considered an important tool for SHM , however, FBG sensors are rarely directly applied to monitor the displacement because of the intrinsic fragility. To overcome such a problem, we propose a novel method for design and curving an FBG sensor using auxiliary flexible driving function of the shape memory alloy (SMA) to monitor the displacement. The FBG sensor is curved slowly to an S shape along with SMA wire. Strain gradient of SMA which is applied by displacement loading is obtained by finite element analysis. By analyzing the spectral simulations, bandwidth of spectrum is increased and the central wavelength is changed. Spectral properties of curved FBG sensor are analyzed by stretch experiments, the results shown that its bandwidth, light intensity of peak and central wavelength are increased and the central wavelength change is linear with displacement. A new sensor based on an FBG sensor and SMA Actuators can be used to monitor displacement with displacement sensitivity of 141pm/mm.