Speed Limit Exists For Birds And Aerial Vehicles, MIT Study Of Goshawks Shows

01/23/2012 12:59 pm ET | Updated Jan 23, 2012

The Northern Goshawk is nature's little speed-demon. It zooms through forests in search of prey, while constantly dodging tree-tops and underbrush. How does the bird keep from crashing?

Robotics scientists at MIT say there's a theoretical speed limit the bird must heed if it wants to avoid crashing. Any faster, and the bird is sure to crash, according to their research, which was recently accepted for the IEEE Conference on Robotics and Automation.

But the scientists--working with Harvard biologists--are convinced that knowing birds' speed limit can help engineers program unmanned aerial vehicles (UAVs) to speed safely through cluttered environments ranging from forests and urban canyons.

(Click to see some of the newest UAVs. Story continues below.)

Drones: The Future Of Flight

Today's UAV's typically fly at slow speeds, so they have enough time to avoid collisions with objects on the ground.

“If I can only see up to five meters, I can only go up to a speed that allows me to stop within five meters,” Emilio Frazzoli, an associate professor of aeronautics and astronautics at MIT, said in a written statement. “Which is not very fast.”

If the Northern Goshawk had to limit its flying speed in a similar fashion, it would be much slower. Instead, the scientists think the hawk bases its speed on the density of foliage--knowing it will be able to find an opening wide enough to make it through.

It's a bit like downhill skiing.

“When you go skiing off the path, you don’t ski in a way that you can always stop before the first tree you see,” Frazzoli said. “You ski and you see an opening, and then you trust that once you go there, you’ll be able to see another opening and keep going.”

In the same way, the scientists say, a UAV could be programmed to avoid collisions. Plug in general information about the density of obstacles its environment, and the drone can determine its maximum speed for collision-free flying.

To this end, Frazzoli and PhD student Sertac Karaman developed mathematical models of different kinds of forests, calculating the spee limit for each. Their work suggests that regardless of how good UAV's are at sensing and reacting to their immediate environment, there will always be a speed limit above which crashes are inevitable.

Only a real birdbrain would want to go faster than that.


Drones: The Future Of Flight