Control Surface Freeplay Nonlinearity: Modeling and Experimental Validation

Abstract

The variety of response behaviors that may be encountered in aeroelastic systems with discontinuous nonlinearities motivates investigations that may support future applications in controls design, utter prediction, instability characterization and energy harvesting exploration. In this paper, a three degree-of-freedom airfoil with control surface freeplay is modeled using an alternative continuous approximation for the discontinuous nonlinearity based on hyperbolic tangent representation. The unsteady aerodynamic loads are computed using the modi ed unsteady Theodorsen approximation for arbitrary motions. Assessment of the validity of the freeplay representation are performed through comparison with experimental data. Nonlinear time series analysis is used to investigate the type of nonlinear behavior and bifurcations. The results validate the continuous approximation for the freeplay nonlinearity for the considered experimental setup conditions.