Commercial, Law Enforcement, Military

Folding, Morphable Quadrotor May Prove Useful in SAR Missions

By Frank Wolfe | December 14, 2018
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Swiss researchers have designed this quadrotor which can change its shape to pass through tight spaces.

Swiss researchers have come up with a design for a quadrotor drone that can morph and fold to pass through tight spaces--an attribute that the researchers believe may prove beneficial for search and rescue teams in disaster response.

"Quadrotors are disrupting industries ranging from agriculture to transport, security, infrastructure, entertainment,
and search and rescue," according to a new paper by three researchers in the Robotics and Perception Group of the University of Zurich's Department of Informatics and two researchers with the Laboratory of Intelligent Systems at the Ecole Polytechnique Federale de Lausanne.


The quadrotors' "maneuverability and hovering capabilities allow them to navigate through complex structures, inspect damaged buildings, and even explore underground tunnels and caves," the paper said. "Yet, current quadrotors still lack the ability to adapt to different flight conditions and tasks, which is commonly observed in birds. This would provide useful in complex scenarios, such as rescue and rescue missions or inspection of complex structures. For example, pigeons and swifts adapt their wing surface by folding in order to optimize gliding efficiency over a broad range of speeds. Pigeons have also been shown to choose different morphologies of their wings to negotiate gaps of different sizes: they fold the wings upward to negotiate relatively large vertical gaps, and fold them tight and close to their body in order to traverse narrower gaps."

While previous quadrotor drone designs have been able to fold to fit through tight spaces, the Swiss researchers said that their design does so without compromising stable flight, flight time, or payload.

"Our quadrotor is able to guarantee stable flight independently of the morphology," according to the research paper. "The key challenge to do so is the need for an adaptive control scheme able to cope in real-time with the dynamic morphology of the vehicle. Any time a new morphology is adopted, our adaptive control strategy is updated in real-time to take into account the new geometry of the robot."

The four propellers, mounted on mobile arms that can fold around the main frame due to servo-motors, rotate independently. The quadrotor's control system is designed to adapt in real time to any new position of the arms by adjusting the thrust of the propellers as the center of gravity shifts.

The design has four main shapes: X-shaped, with the four arms stretched out and the propellers at the widest possible distance from each other; H-shaped with all the arms aligned on one axis to pass through narrow spaces; O-shaped with all arms folded close together; and T-shaped to allow the on-board camera to inspect objects closely.

If proven out, such a quadrotor could inspect a damaged building after an earthquake or during a fire, search for people trapped inside a building and guide rescuers there, the researchers said.

The researchers want to develop algorithms that will make the drone fully autonomous so that it can, for example, search for survivors in a disaster scenario independently, including choosing the best course to reach the survivors through narrow passages.

Davide Falanga, a University of Zurich researcher and one of the report authors, said in a statement that "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."

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