Modeling and Control of a Flexible-Wing UAV Performing Soaring

In this paper, we consider the control design for a flexible-wing UAV, encountering orographic and thermal updrafts. The flexible wings of the UAV are assumed to have a wing twist capability, and this wing twist is employed to modify the local angle of attack distribution over the wing, when it encounters the updrafts. This in turn leads to a modified lift distribution over the wings. It is assumed that this elastic wing twist is employed in conjunction with deflection of the conventional aileron, elevator and rudder control surfaces. The control system is designed using a dynamic inversion methodology. Simulations of the closed loop system, for scenarios when the UAV encounters an orographic and thermal updraft, respectively, are presented.