Predicting freeplay-induced aeroelastic limit-cycle oscillations using pre-critical output data

This paper presents an output-based approach for predicting aeroelastic limit-cycle oscillations caused by freeplay, a common concentrated stiffness nonlinearity in actuated structures. The approach extends conventional output-based flutter boundary estimation by capturing freeplay-induced nonlinear effects, enabling the prediction of limit-cycle oscillations beyond the flutter onset. It also extends bifurcation forecasting through a new formulation that captures how freeplay nonlinearity affects the recovery rate to equilibrium. The approach is demonstrated using data from simulated time histories of an idealized tilting propeller in airplane mode, with freeplay in the tilting mechanism. Using as few as one or two pre-critical responses, the method estimates regions of the parameter-amplitude plane associated with limit-cycle oscillations, which define the bifurcation diagram. These results indicate promise for the analysis of freeplay-induced limit-cycle oscillations in higher-complexity models and for potential experimental studies.