Frequency domain tracking of time-varying modes

Abstract

Many engineering applications involve systems whose dynamics vary with time. Consider, for example, the dynamics of the wings of a plane that is airborne. The resonance modes of the wings, and the associated damping and stiffness are functions of the flight speed and height. Therefore, the dynamics vary as the plane accelerates and/or its altitude increases. This paper provides a methodology for tracking the evolving dynamics of linear, slowly time-varying systems. The responses of the systems to multisine excitations are explained and shown to provide an insight into the time-varying behavior of the system. The acquired knowledge of the responses is used to estimate non-parametrically the instantaneous frequency response function from one single experiment. A simplified case, where the variations are linear with time, is discussed in this paper. A glance of a generalization procedure to a polynomial variation is given. Results are illustrated on simulations of a lumped time-varying system. ©2010 Society for Experimental Mechanics Inc.