Optimization of Perching Maneuvers Through Vehicle Morphing

This paper discusses the development and optimization of trajectories designed to bring a long endurance unmanned aerial vehicle from a loitering state to a planted landing referred to as a perching maneuver. These trajectories are developed for attached, partially stalled, and fully stalled flow regimes. The effects of nonlinear aerodynamics and vehicle shape reconfiguration are shown to lessen the initial distance from the landing site required to initiate the maneuver, reduce the spatial bounds on the trajectory, and decrease the required thrust for the maneuver. The aerodynamics are modeled using empirical and analytical methods in both attached and separated flow regimes. Optimal solutions of varying thrust-to-weight ratio and center-of-gravity location are compared. Additionally, perching trajectories that compare morphing versus fixed configuration and stalled versus unstalled aircraft are presented to demonstrate the effects of relaxed constraints on vehicle geometry and flight envelope. Control effort is also evaluated in these simulations; specifically, the available control for disturbance rejection is compared for morphing versus fixed-configuration aircraft. The results of these comparisons show that morphing increases the controllability of the aircraft throughout the maneuver as well as decreases the cost of the optimal perching trajectory.