Experimental Mode Shape Identification for a Cantilever Beam Using Optical Fiber Bragg Gratings

Parameter estimation of a cantilever beam model typically involves estimating the effective parameters of the system for an assumed mode shape. This shape assumption, which is difficult to verify with traditional single-point sensors, can be validated through the distributed strain measurements available from optical Fiber Bragg Grating sensors. In this paper, the experimental mode shapes of a cantilever beam acquired from Fiber Bragg Grating sensors are compared with the analytical predictions of classical beam theory for the first two bending modes. A single degree of freedom model is also analyzed for the first bending mode and compared to the distributed parameter model and experimental data. It is shown that the distributed parameter model provides a good estimate of the strain profile at the first two natural frequencies, and that the single degree of freedom and distributed parameter models are in close agreement at the first natural frequency.