Biorobotics researchers at the Institut des Sciences du Mouvement – Etienne-Jules Marey (CNRS/Aix-Marseille Universite) have developed an aerial robot stabilized visually without an accelerometer and capable of flying over uneven terrain.
Called BeeRotor, it adjusts its speed and avoids obstacles, thanks to optic flow sensors inspired by an insect’s vision. It can fly along a tunnel with uneven, moving walls without measuring either speed or altitude.
CNRS says the following comes from a recently published study in the journal “Bioinspiration and Biomimetics”:
“All aircraft, from drones to the Ariane launcher, are currently equipped with an inertial measurement unit, including accelerometers. This allows these aircraft to stabilize their roll and pitch with respect to the horizon or rather with respect to its perpendicular: the
direction of the center of the Earth … However, this essential tool has no equivalent in insects, which fly quite happily without this information.
Researchers Fabien Expert and Franck Ruffier therefore took inspiration from winged insects to create BeeRotor, a tethered flying robot able for the first time to adjust its speed and follow terrain with no accelerometer and without measuring speed or altitude.
With a weight of 80 grams and a length of 47 centimeters, it can, all by itself, avoid vertical obstacles in a tunnel with moving walls. To achieve this, the researchers mimicked the ability of insects to use the passing landscape as they fly.
This is known as optic flow, the principle of which can readily be observed when driving along a motor way: the view in front is fairly stable, but looking out to either side, the landscape passes by faster and faster, reaching a maximum at an angle of 90 degrees to the path of the vehicle.
To measure optic flow, BeeRotor is equipped with a mere 24 photodiodes (or pixels) distributed at the top and the bottom of its eye. This enables it to detect contrasts in the environment as well as their motion. As in insects, the speed at which a feature in the scenery moves from one pixel to another provides the angular velocity of the flow. When the flow increases, this means that the robot's speed is also increasing or that the distance relative to obstacles is decreasing.”
A video of the drone in flight can be seen here.
Photo courtesy of Expert & Ruffier (ISM, CNRS/AMU)