Nonlinear aeroservoelastic control in the presence of uncertainty

Limit Cycle Oscillations (LCOs) are a typical behaviour of nonlinear aeroelastic systems. This work focuses on suppressing such nonlinear behaviour in a two degrees of freedom aeroservoelastic system with a structural nonlinearity in the plunge degree of freedom. Theodorsen’s unsteady aerodynamics is used to accurately describe the aerodynamic forces acting on the structure, whereas the action of the two control surface is described using a quasi-steady approximation. The model data is validated using an experimental test rig developed in the wind tunnel at the University of Liverpool. A feedback linearization controller is developed to suppress the exhibited LCO and the effectiveness of the technique is analyzed with both one and two control surfaces. Due to the limitations of this method in presence of inexact nonlinearity cancellations, a more robust control technique based on dissipativity is considered and a controller capable of stabilizing the nonlinear behaviour is developed with satisfactory results even in presence of uncertainty on the nonlinearity.