Autonomously recharging UAVs from existing infrastructure has enormous potential for various applications, such as infrastructure inspection, surveillance, and search and rescue. While it is an active area of research, most related work focuses on alternating current (AC) infrastructure while very little work has been done on investigating the potential of recharging UAVs from direct current (DC) infrastructure. This work proposes a UAV system designed to autonomously recharge from existing DC infrastructure. Two onboard powerline grippers and a motorized cable drum enable the UAV to perform a two-stage landing on railway DC lines where a wire is connected between them through the UAV for recharging. Light-weight electronics designed to be carried by the UAV are developed to harvest energy from up to 3kV DC railway lines. The recharge mission is autonomously executed using fully onboard and real-time perception and trajectory planning and tracking algorithms. The potential of the system is shown in lab setting validation, with hardware-in-the-loop simulation, and partly in a real overhead powerline environment, verifying the functionality of the sub-components.

This paper examines an inductive power transfer (IPT) system with a rotary transformer as an alternative solution to slip ring systems for a contactless energy transfer to rotating equipment. A prototype system is set up, consisting of a rotating ball bearing shaft and an exemplary sensor circuit mounted on the shaft. Three possible transformer configurations are analyzed theoretically and experimentally regarding the self-inductance, the coupling factor and the losses in the litz wire. To utilize the intrinsic stray inductances of the rotary transformer, a series compensated resonant converter is implemented for the prototype system.