Energy-based long-range path planning for soaring-capable unmanned aerial vehicles

To enable long-distance, long-duration flights by small soaring-capable uninhabited aircraft, a graph-based method for planning energy-efficient trajectories over a set of waypoints is presented. It introduces the energy map, which is an upper bound on the minimum energy required to reach a goal from anywhere in the environment while accounting for arbitrary three-dimensional wind fields. The energymap provides the path to the goal as a sequence of waypoints, the optimal speeds to fly for each segment between waypoints and the heading required to fly along a segment. Trajectories computed using the energy map are compared with trajectories planned using an A* -based approach. Results are presented for simple wind fields representative of orographic lift. Finally a high-fidelity numerical simulation of a realistic wind field (ridge lift and wave over complex terrain) is used as a test case. The energy-map approach is shown to perform very well without the need for the heuristics associated with A*.