I. INTRODUCTION
Unmanned vehicles have become widely popular among researchers in the last decade. Teams consisting of unmanned aerial vehicles (UAVs) and ground vehicles (UGVs) can compliment each other in applications such as fire fighting, border security, and infrastructure inspection ([1], [2], [3]). A common theme is persistent monitoring, where vehicles must move periodically around areas of a map over a period of time. A challenge with using UAVs is limited energy supply, i.e., the vehicle must be replenished with energy frequently as needed. To support this effort, static and mobile charging stations are often used.