Multi-Rung Ladder Wireless Power Transfer System for Stackable Unmanned Aerial Vehicle Swarm Charging Applications

This letter proposes a magnetic-circuit co-design for a wireless power transfer system to facilitate autonomous charging of vertically stacked unmanned aerial vehicle (UAV) clusters. To address the challenges of position-dependent coupling and unstable power distribution in multi-load scenarios, a multi-rung axial magnetic coupler is designed, ensuring stable coupling with lightweight receivers regardless of their vertical stacking position, thereby effectively mitigating issues related to position-dependent power transfer. By integrating this coupler with an LCL-S compensation network, the system achieves load-independent constant-current excitation. In this configuration, the total output power scales linearly with the number of active UAVs, while individual power delivery remains invariant to vertical positions. A 250-W experimental prototype validated the design, achieving stable concurrent charging for multiple units with a DC–DC efficiency of 86.3%, thus offering a robust and scalable solution for high-density UAV swarm operations.