Improved FRF Measurements of Lightly Damped Systems Using Local Rational Models

Lightly damped systems exhibit strong resonances which should be accurately characterized to prevent potential harmful damage in real-world applications. Characterizing these resonances using frequency response function (FRF) measurements is challenging due to long transient behavior and spectral leakage. Local modeling techniques exist which remedy these difficulties, but they introduce a bias or do not use an appropriate model structure. In this paper, we solve these problems by developing two local rational modeling techniques that remove the bias on the FRF measurement. The proposed techniques involve the use of the bootstrapped total least squares estimator on the one hand and the incorporation of prior knowledge of the pole locations on the other hand. Furthermore, the performance of both techniques is demonstrated by measuring the flexural vibrations of a steel beam.