MIT Scientists Suggest Birds Follow Speed Limit


A goshawk, the "master of maneuverability" inspired research into a bird's speed limit. Photo: Terry Spivey, USDA Forest Service

Ever wonder how birds fly through a cluttered forest? New research out of MIT has offered up a solution: Birds obey the speed limit.

Whether trying to beat crowds on a city street or avoid trees while skiing off-piste, how fast you move is a function of what’s in your way. MIT’s Emilio Frazzoli, an aeronautics and astronautics professor at MIT, and PhD student Sertac Karaman have been working on fast-flying pilotless robots and turned to the birds to work out how they manage mid-flight maneuvering.

Karaman explains on his website that the idea was inspired in part by BBC footage of a goshawk nimbly ducking and dodging trees on his flight through dense forest.

In a paper submitted to the IEEE Conference on Robotics and Automation, Karaman and Frazzoli lay out their mathematical model for a bird speed limit. The idea is that a given forest space will have a certain amount of random obstacles, so a bird needs to observe a critical speed limit, flying as fast as possible without being so fast that a crash is inevitable.

The "limit" is based on a formula, in which maximum speed depends on the density of obstacles present, the flyer’s maneuverability, and the size of the obstacles ahead.

To test how their theoretical limit applies to real birds, Frazzoli and Karaman are now teaming up with a Harvard biologist to try the formula out on pigeons.

It's not just for the birds, either. Their model can apply to other movement from the flight of a bumblebee to downhill skiing. To see what happens with a human in the driver seat, Frazzoli and Karaman are also developing a videogame simulation. Ultimately, the knowledge could create faster drones that can maneuver obstacle-rich environments "as in a search-and-rescue situation," Frazzoli says.

For more on amazing bird flight, don’t miss Susan Cosier’s post on starling murmurations or Richard Barnes’ piece for the March-April 2009 issue of the magazine, “Flight Plan.”

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