Drones that change shape in flight.

Why fold in flight

A drone’s width is set by its propellers. Open, it is stable and efficient; narrow, it fits through a door left ajar or between pieces of furniture. Folding in flight gives a robot both: wide where there is room, narrow where there is not.

How it works

Each arm turns on a hinge, driven by a small motor, while the flight controller keeps the drone level. As the arms move, the controller has to know where each propeller now is, because the lever arms that keep the drone balanced change with the shape. Research groups showed this in flight several years ago, for example the foldable drone from the University of Zurich.

What makes it hard

• Propellers must not meet, in any shape and in any moment between two shapes.
• Control changes with shape: a narrow drone tips more easily in one direction.
• Weight: every hinge and motor costs grams that the battery has to carry.
• Knowing when to fold: fold too early and the robot is clumsy; too late and it touches the frame.

In Alkyon Concept

Alkyon’s four arms each turn on their own, so it can take several shapes. It is designed to fold each side only as far as that side needs, to keep its arms folded until a gap is fully behind it, and to keep its propellers apart in every shape. How that works out in our simulation, numbers included: through a narrow door.