Analysis of Nonlinear Aeroelastic Signals

A signal processing technique is presented to analyze nonlinear aeroelastic time series where limit-cycleos cillations and chaotic motions may occur. A powerful method to study nonlinear aeroelastic behavior of aircraft structuresisthe phase-space reconstruction technique. In the reconstruction process, the mutualinformationfunction and the percentage of false neighbors methods are used to estimate the time delay and the dimension of the attractor, respectively. The dynamics of the system are then determined from the Lyapunov exponents. A method of estimating frequency and damping values of the aeroelastic system from the reconstructed phase space is also presented. Examples are given for a two-dimensional airfoil oscillating in pitch and plunge with either a bilinear or acubic spring nonlinearity in one of the degrees of freedom