Saturday, February 10, 2007

Bug-brained chopper

Insects manage some pretty amazing aerial acrobatics for having a brain we humans can hardly see with the unaided eye. Yet even our best engineers and AI experts have trouble programming simple autonomous navigation. Just look at what it took to finish The Grand Challenge.

Now researcher Nicolas Franceschini, a neurophysiologist and engineer at France’s National Center for Scientific Research and at the University of the Mediterranean in France has decided to emulate those little bug brains in his newest project.

The simple principles that Franceschini and his colleagues think underlie insect flight have to do with visual cues. As insects fly, their ground view changes depending upon their height above the ground and their speed relative to the ground. Essentially, the higher the insect, the slower the ground will appear to sweep below it.

The changing view that insects have of the ground, known as "optic flow," thus encodes details on both an insect's height and velocity. Franceschini and his colleagues speculated that insects rely on simple relationships between their height and velocity to keep flying. Basically, the idea is that if they slow down, they will begin descent, and if they speed up, they will begin climbing. By the same token, if they are descending, they will slow down, and if they are climbing, they will speed up.

"They don't need a speedometer or altimeter. They just need to use their eyes," said Franceschini, whose latest work on this topic is detailed online in the Feb. 8 issue of the journal Current Biology.

That's pretty cool stuff. A simple feedback system controls both speed and altitude--ain't evolution grand? Of course, such a simple system can sometimes trip up.

Their findings also help illuminate the basis for a number of previously unexplained observations regarding insect flight. For instance, honeybees often drown when flying over very still water. "There are no contrasting features in their field of view then, so they have no visual cues to go by," Franceschini said.

Franceschini's helicopter is equiped with a 200 mg. electronic brain, is tethered to a maypole, and free to fly around. At least under these simple circumstances, it seems to behave just like a fly.

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