SPECTRAL IDENTIFICATION OF NONLINEAR STRUCTURAL SYSTEMS

The paper discusses a spectral method for identification of nonlinear systems encountered in structural applications. The nonlinearity is ac counted for by a combination of linear subsystems and known zero-memor y nonlinear transformations; an equivalent linear multi-input-single-o utput (MISO) system is developed for the identification problem. The u nknown transfer functions of the MISO system are identified by assembl ing a system of linear equations in the frequency domain. This system is solved by performing the Cholesky decomposition of a related matrix . It is shown that the proposed identification method can be interpret ed as a ''Gram-Schmidt'' type of orthogonal decomposition of the input -output quantities of the equivalent MISO system. A numerical example involving the identification of unknown parameters of a Duffing oscill ator with nonlinear damping elucidates the applicability of the propos ed method.