A research team from the University of Zurich and the École polytechnique fédérale de Lausanne (EPFL) in Lausanne, Switzerland, has developed a new drone that can retract its propellers in flight, allowing the aircraft to fit through narrow spaces.
According to the researchers, this design feature would be particularly useful for searching for victims of natural disasters through a crack in the wall or a partially open window, for example. The concept is outlined in a paper entitled “The Foldable Drone: A Morphing Quadrotor that can Squeeze and Fly,” available here.
The researchers are from the Robotics and Perception Group at the University of Zurich and the Laboratory of Intelligent Systems at EPFL, which are part of the National Centre of Competence in Research (NCCR) Robotics, funded by the Swiss National Science Foundation.
Inspired by birds that fold their wings in midair to cross narrow passages, the new drone can squeeze itself to pass through gaps and then go back to its previous shape – all while continuing to fly stably. Notably, it can even transport objects along the way.
“Our solution is quite simple from a mechanical point of view, but it is very versatile and very autonomous, with onboard perception and control systems,” explains Davide Falanga, researcher at the University of Zurich and the paper’s first author.
Working in close collaboration, the Zurich and Lausanne teams designed a quadcopter mounted on mobile arms that can fold around the main frame, thanks to servomotors. The control system adapts in real time to any new position of the arms, adjusting the thrust of the propellers as the center of gravity shifts, the researchers explain.
“The morphing drone can adopt different configurations according to what is needed in the field,” adds Stefano Mintchev, co-author and researcher at the EPFL School of Engineering.
The standard configuration is X-shaped, with the four arms stretched out and the propellers at the widest possible distance from each other. When faced with a narrow passage, the drone can switch to an “H” shape, with all arms lined up along one axis, or to a “O” shape, with all arms folded as close as possible to the body. A “T” shape can be used to bring the onboard camera mounted on the central frame as close as possible to objects that the drone needs to inspect.
In the future, the researchers hope to further improve the drone structure so that it can fold in all three dimensions. Most importantly, they want to develop algorithms that will make the drone truly autonomous, allowing it to look for passages in a real disaster scenario and automatically choose the best way to pass through them.
“The final goal is to give the drone a high-level instruction such as ‘enter that building, inspect every room and come back’ and let it figure out by itself how to do it,” says Falanga.