Real-time modal parameter estimation using subspace methods and fiber Bragg-gratings

In this article, a recently developed on-line subspace modal parameter estimation algorithm is applied to response measurements from optical fiber Bragg grating strain sensors bonded to struts in a 4 meter laboratory truss structure. Experimental evaluation of this algorithm demonstrates that the technique accomplishes the objective of tracking multiple modes of a complex dynamical system using multiple sensors. The time-varying behavior is captured in real-time via a graphical display of the frequencies and damping ratios of the system. It is shown that the recursive algorithm provides results similar to the batch algorithm for a time-invariant system. Details of the digital signal processor implementation and the Bragg-grating strain measurement system are also presented.