D2DC: Mid - Air Drone- to- Drone Charging to Enhance Flight Endurance

Last-mile delivery is shipping goods by ground from distribution centers to customers. It is the supply chain's most expensive, complex, and polluting phase. Companies seeking cheaper, faster, and greener logistics are looking to Unmanned Aerial Vehicles (UAVs/drones) for solutions. Several companies aspire to develop Urban Air Mobility (UAM) networks to provide on-demand mobility using an electrical Vertical Takeoff and Landing (eVTOL) aircraft. However, like ground electric vehicles (EVs), UAVs have limited flight endurance due to onboard power constraints. The conventional approach of charging a UAV requires it to halt the flight mission and remain grounded while charging at a slow rate. As a result, UAVs often need detours toward a charging station and add a time penalty on top of the time spent recharging at a station. Such challenges make drone technology less economical and impede its wide-scale adaptation. This paper proposes a novel mid-air Drone-to-Drone (D2D) energy-sharing paradigm, a scalable and cost-effective solution to increase the overall flight endurance of a UAV swarm. This framework allows the UAVs to share charge and sustain each other based on the instructions received from a centralized controller. We introduce innovative components such as multi-level battery architecture, a mid-air energy exchange mechanism, and a cloud-based control unit. We have also developed a drone traffic simulator to evaluate the efficacy of the proposed framework in package delivery tasks. After performing a numerical analysis using the developed simulator, we observed up to 28.24% improvement in the mission success rate and up to 10% increase in the overall flight range of a UAV swarm.