The Effects of Shape Reconfiguration on Morphing Aircraft in Perching Maneuvers

This paper focuses on a novel morphing aircraft capability called perching: the ability of an aircraft to make a planted landing using primarily aerodynamic forces in lieu of high thrust. Specifically, the modeling of the perching aircraft’s aerodynamics and the problem of computing and optimizing a perching trajectory using this model are presented. The aerodynamic model discussed herein is designed using empirical and analytical methods in both separated and attached flow regimes, including nonlinear and time-varying effects such as flow separation and dynamic stall. This vehicle model is used to optimize the landing trajectory with respect to its spatial boundaries; these include the maximum undershoot — or dip below the landing point — and the required starting distance from the landing site. Optimal solutions of varying thrust-to-weight ratio and center of gravity location are compared. Additionally, perching trajectories that compare stalled versus un-stalled and morphing versus fixed-configuration aircraft are presented in order to demonstrate the effects of relaxed constraints on flight envelope and shape reconfiguration, respectively. The available control for disturbance rejection is distinguished between morphing and fixed-configuration aircraft. These results show that vehicle morphing increases the controllability of the aircraft throughout the maneuver as well as decreases the spatial requirements of the optimal perching trajectory.