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.

Today, many inspection domains utilize the benefits of drones to monitor and inspect infrastructure in an efficient manner. The energy grid is challenged by frequent and thorough inspection to stay operational. So far, drones have already been introduced to solve this challenge. However, the inspection drone still requires manual control and subsequent human examination of the captured photos and videos. This inspection process comes with a high inspection cost and is susceptible to human errors in fault finding. The proposed system builds on top of the authors’ previous research to develop and verify an integrated drone system for autonomous power line inspection, enabling functioning mechanics through pneumatics, extension of operation time through energy harvesting, Artificial Intelligent (AI) fault detection, and system autonomy using navigational algorithms. An advanced drone system has been designed and manufactured for the mission, with the results demonstrating the capability to perform an autonomous inspection mission in conditions up to 30 kts wind speeds, being additionally able to detect faults in real-time at a high rate during drone motion. Furthermore, we demonstrate the ability to recharge the drone battery within 2.4 hours.

In recent years drones have proven their ability to solve complex tasks autonomously and effectively. Drones have not been present as a ubiquitous technology for solving these tasks yet. The reason is mainly due to their limited flying time. The technology has great market potential in many areas if flight time could be increased. However, only a few solutions for recharging are available, but none for recharging on power lines. This remains a research topic for now. Through this paper a novel energy harvesting design is presented based on inductive coupling, allowing a drone to grasp and perch onto an overhead power line to recharge its batteries. The overall electronic design was based on analyzing and simulating different current transformers in simulation before testing in the laboratory. The split-core including windings was integrated into a gripping mechanism, verified by analytical and numerical analysis as well as non-destructive and destructive testing. The results indicate that enough power can be harvested from the powerline to recharge the drone batteries. The theoretically achievable power was also found to be within the expected range. With this design, drones can solve time-consuming and complex tasks in the future.