An algorithm for identification of lightly damped structural modes

An algorithm for the estimation of the natural frequency and the damping factor of lightly damped structural modes is described. The core of the identification process is a subspace-based deterministic-stochastic realization algorithm (DSRA). Identification focuses on one resonant mode at a time; this allows for filtering out the noise and harmonic components present in the data before the identification is carried out. A test to determine the reliability of the estimates is carried out so that particularly noisy records are detected and discarded. The algorithm was applied to simulated data as well as to V-22 tiltrotor aircraft flight test data obtained from Bell Helicopter Textron, Inc. and the results were compared with those obtained using the standard Prony analysis. It was found that both the Prony method and the current algorithm performed well for most data records.