  This paper is concerned with identifying the instantaneous modal parameters
of forced oscillatory systems with response-dependent generalized inertia
(mass, inductance, or equivalent) based on their measured dynamics. An
identification method is proposed, which is a variation of the "FORCEVIB"
method. The method utilizes analytic signal representation and the properties
of the Hilbert transform to obtain an analytic relationship between a system's
natural frequency and damping coefficient to its response and excitation
signals. The proposed method is validated by comparing the identification
results to the asymptotic solution of a simple system with response-dependent
inertia and is then demonstrated, numerically and experimentally, for other
more complicated nonlinear systems.
