Identification of stiffness,dissipation and input parameters of randomly excited non-linear systems: Capability of restricted potential models (RPM)

A dynamic identification technique in the time domain for time invariant systems under random external forces is presented. This techniqueis based on the use of the class of restricted potential models (RPM), which are characterized by a non-linear stiffness and a special formof damping, that is a product of the input power spectral density (PSD) matrix and the velocity gradient of a non-linear function of thetotal mechanical energy. By applying Itˆo stochastic differential calculus and by specific analytical manipulations, some algebraic equations,depending on the response statistics and on the mechanic parameters that characterize RPM, are obtained. These equations can be used for thedynamic identification of the above mechanic parameters once the response statistics of the system to be identified are evaluated. The proposedtechnique allows one to identify single-degree-of-freedom or multi-degrees-of-freedom systems in the case of unmeasurable input. Further, theprobabilistic characteristics of the external forces can be completely estimated in terms of PSD matrix.