Solar-Powered Aircraft: Energy-Optimal Path Planning and Perpetual Endurance

摘要

This paper considers energy-optimal path planning and perpetual endurance for unmanned aerial vehiclesnequipped with solar cells on the wings, which collect energy used to drive a propeller. Perpetual endurance is thenability to collect more energy than is lost during a day. This paper considers two unmanned aerial vehicle missions:n1) to travel between given positions within an allowed duration while maximizing the final value of energy and 2) tonloiter perpetually from a given position, which requires perpetual endurance. For the first mission, the subsequentnproblem of energy-optimal path planning features the coupling of the aircraft kinematics and energetics modelsnthrough the bank angle. The problem is then formulated as an optimal control problem, with the bank angle andnspeed as inputs. Necessary conditions for optimality are formulated and used to study the optimal paths. The powernratio, a nondimensional number, is shown to predict the qualitative features of the optimal paths. This ratio alsonquantifies a design requirement for the second mission. Specifically, perpetual endurance is possible if and only if thenpower ratio exceeds a certain threshold. Comparisons are made of this threshold between Earth and Mars.nImplications of the power ratio for unmanned aerial vehicle design are also discussed. Several illustrations are given.