Drones get a lot of attention in warfare, but their impact goes way beyond that. The rapid advancement of drone technology has transformed various industries, from filmmaking to agriculture. However, one significant limitation has always been battery life, which restricts the duration and range of drone operations.

This is about to change with the introduction of an innovative self-recharging drone system that utilizes overhead power lines for uninterrupted, long-duration flights. Developed by a team of researchers at the University of Southern Denmark, this technology promises to revolutionize the way drones are used in infrastructure inspection and monitoring.

Long-lasting drones

Drones are revolutionizing surveying across a spectrum of fields. In agriculture, drones equipped with multispectral cameras provide farmers with detailed data. Farmers can monitor crop health, irrigation needs, and pest pressure, facilitating precision agriculture practices that enhance productivity and sustainability. For infrastructure, drones offer a bird’s-eye view for the inspection of hard-to-reach structures like bridges, towers, and rooftops, reducing the need for risky human inspections. Environmental scientists also utilize drones for ecosystem monitoring, tracking changes in habitats, and mapping remote areas without disturbing the natural environment.

But every 30 minutes or so, most drones need to come back for a battery change. This not only wastes a lot of time, but also reduces the scope and distances over which drones can be used.

The new system changes that. It features a robust navigation system, enabling the drone to sense and locate power lines autonomously and land on them. Upon landing on the power lines, the drone grips on to the cable. This not only secures it but also harnesses the magnetic field created by the current in the power line to recharge the drone’s battery.

“The magnetic gripper is made of a current transformer that works as a gripper and an energy harvester,” the researchers write in the paper.

“Once the gripper is closed, the magnetic control circuit is responsible for maintaining a sufficient holding force while
simultaneously charging the drone’s battery by manipulating the magnetic field inside the split core”.

The system is controlled via an algorithm that adjusts the magnetic field within the gripper to maintain the necessary holding force and optimize the charging process based on the power line’s current level and the battery’s state. This ensures efficient energy transfer and secure attachment during charging sessions, which are crucial for the safety and reliability of the system.

A design for future work

The researchers tested the drone in multiple environments, and the drone performed several cycles of flying, landing, recharging, and taking off, without any human intervention. Overall, the drone was able to operate autonomously for several hours, significantly extending its mission capability.

This breakthrough extends the possible mission duration indefinitely (as long as power lines are nearby), opening up new possibilities for continuous monitoring and detailed inspections of critical infrastructure like power lines, bridges, and railways. For now, researchers want to use it specifically to monitor power lines — one of the most common drone survey applications.

There are still limitations, the researchers concede. The system is not ready to enter the market just yet and the drone can only charge when it’s above 45% battery. So, there’s still plenty of work to be done. Nevertheless, the team is optimistic that the approach will soon be put to use. This technology could pave the way for more frequent and thorough inspections, leading to improved maintenance and safety of essential infrastructure.

“We demonstrated a fully autonomous drone system able to operate indefinitely by charging from powerlines on demand, enabling sustained inspection missions,” the team concludes. “The integrated system was demonstrated to operate for more than two hours with five inspection/charging cycles, proving its feasibility.”

For now, the study has been published in arXiv, a pre-print server.