Periodic Energy-Optimal Path Planning for Solar-Powered Aircraft

[Abstract] This paper considers energy-optimal path planning in a loitering mission for solar-powered unmanned aerial vehicles (UAVs) which collect solar energy from the sun to power their flight. We consider ascending and descending flight maneuvers in a periodic mission constrained to the surface of a vertical cylinder. The coupling of the aircraft kinematic and energetic models is treated in a novel scheme that implements both the periodic and cylindrical constraints. Optimum trajectories are identified by specifying the heading angle and altitude by periodic splines. Given the periodic splines, we are able to solve for the other aircraft parameters, including the aerodynamic, propulsive, and energetic properties of the aircraft. In an example problem, trajectories are obtained that generate better energy properties than those given by constant altitude circular flight. Numerical simulation results are presented that help demonstrate the properties of the optimum trajectories.