Comparison of experimental identification techniques for a nonlinear SDOF system

Several experimental nonlinear identification techniques have been presented in the literature. In this paper, several of these techniques are applied to a single degree of freedom system and the results are compared. We apply a time-domain technique and two frequency-domain techniques to the second mode of a cantilevered beam. The frequency-domain techniques include a backbone curve-fitting technique based on the describing function method and an amplitude and frequency sweep technique based on the method of multiple-scales. The equation of motion is derived from a Lagrangian using the assumed-modes method. Based on the form of the equation of motion, we note that the restoring-force-surface method cannot be used to determine the equation of motion. Differences in the parameter estimates are discussed. We conclude by discussing the limitations we encountered for each technique. These include the inability to separate nonlinear curvature and inertia effects and problems with estimating the coefficients of small terms with the time-domain technique.