Algorithms for Routing of Unmanned Aerial Vehicles with Mobile Recharging Stations and for Package Delivery

We study the problem of planning a tour for an energy-limited Unmanned Aerial Vehicle (UAV) to visit a set of sites in the least amount of time. We envision scenarios where the UAV can be recharged along the way either by landing on stationary recharging stations or on an Unmanned Ground Vehicles (UGV) acting as a mobile recharging station. This leads to a new variant of the Traveling Salesperson Problem (TSP) with mobile recharging stations. We present an algorithm to find the optimal tours to determine not only the order in which to visit the sites but also when and where to land on the charging stations to recharge. Our algorithm plans tours for the UGV as well as determines best locations to place stationary charging stations. While the problem we study is NP-Hard, we present a practical solution using Generalized TSP that finds the optimal solution (albeit in possibly exponential worst-case running time). Our simulation results show that the running time is acceptable for reasonably sized instances in practice. We also show how to modify our algorithms to plan for package delivery with UAVs using UGVs as mobile warehouses.