Aerial Dockable Multirotor UAVs: Design, Control and Flight Time Extension through In-flight Battery Replacement

This paper presents the development and evaluation of the AirDock system, a novel aerial docking and in-flight battery exchange solution designed to extend the operational flight time of multirotor unmanned aerial vehicles (mUAVs). The proposed system enables seamless mid-flight battery replacement through an aerial docking mechanism and a rail-Car-based battery transfer and retrieval system. The AirDock platform utilizes a fully actuated multirotor design, allowing independent control of six degrees of freedom (DoF) motion to maintain a constant attitude during battery exchange operations, facilitating easy docking. In this research, a generalized control allocation algorithm is introduced to manage dynamic shifts in the center of mass (CoM) during inter-modular battery transportation, ensuring safe flight control and mitigating thruster overloading: a critical factor in avoiding flight failure. Both simulations and real-world experiments validate the system’s effectiveness, demonstrating stable aerial docking, reliable in-flight battery exchange performance, and extended flight durations for mission modules. These findings highlight the AirDock system’s potential to overcome the energy limitations of battery-powered UAVs, extending missions across various applications.