On the Scheduling of Systems of Heterogeneous UAVs and Fuel Service Stations for Long-Term Mission Fulfillment

2 The duration of missions that can be accomplished by unmanned aerial vehicles (UAVs) is limited by the battery or fuel capacity of its constituent UAVs. However, a system of UAVs that is supported by automated refueling bases may support long term or even indefinite duration missions in a near autonomous mode. The UAVs can return to a base, replenish their resources and resume their duties. We develop a mixed integer linear program model to formalize the problem of scheduling such a system that includes multiple bases in disparate geographic locations that are shared between the UAVs. The system consists of a heterogeneous fleet of UAVs (each with different travel speed and distance capabilities), refuel stations and mission trajectories that must be followed by at least one UAV. A UAV may hand off the mission to another in order to return to base for a fuel recharge. For two example problems, a state of-the-art MILP solver such as CPLEX is sufficient to create a schedule for the model. This is the first time that a generic scheduling model has been developed that allows mobile agents to return to service after refueling across multiple bases. In practice, the approach allows for a long-term mission to receive uninterrupted UAV service by successively handing off the task to replacement UAVs served by geographically distributed shared bases.