Abstract: Identification of dynamic natural frequencies and viscosity damping coefficient for a large-scale structure in practical working condition is a very difficult problem. A new system identification method for the kind of engineering problems is presented, using nonlinear modeling and wavelet transform. The dynamic natural frequency and damping for the shaft system of a water turbine are successfully estimated from field measured signal using this method. Through comparing simulation results to theoretic results, the adaptability and validity of the method are here proved.

Key words: Dynamic natural frequencies, Large-scale structure, System identification, Viscosity damping coefficient, Water turbine