Resource Schedules for Persistent UAV Systems with Logistics Replenishment Platforms: Petri Net Models and LP Formulation

Many unmanned aerial vehicles (UAVs) suffer from limited flight duration and thus long-term operations are prohibited. With replenishment of essential consumables, such as fuel and packages, by automated logistics service stations (LSS), persistent operations are enabled. However, persistent UAV operations require more than just LSS. Overall system resource requirements enabling the desired coverage as well as detailed schedules for the orchestration of the UAVs and LSS resources are essential. In this paper, we focus on a system of UAVs that are served by battery charging platforms seeking to provide a persistent UAV presence. We refine prior work that calculates the required resources for persistence. To generate detailed resource schedules, we first impose a sequential resource selection rule. This enables an extended Petri net model of the system behavior in the periodic regime that explicitly models resource pairing. A linear program (LP) to determine the firing times of events in the Petri net is developed. From this LP, detailed resource schedules are obtained. Further insights that can be deduced from the models are considered.