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TECHNOLOGY: Goshawks hold mathematical key to fast, safe UAV flight

Researchers at the Massachusetts Institute of Technology hope to give new meaning to the concept of a speed limit by using the mathematical model of bird in flight to find out how fast an unmanned aerial vehicle (UAV) can fly without hitting obstacles.

By studying the flight of the northern goshawk - which hunts birds and small mammals by speeding through tree canopies and underbrush - associate professor of aeronautics and astronautics Emilio Frazzoli is attempting to help engineers build fast, agile UAVs to survive cluttered environments such as forests or cities.

As Frazzoli noted, most UAVs today fly at relatively slow speeds, so as to be able to take evasive action within the limits of their sensors. However, he speculated that the goshawk manages much greater speed by gauging the density of a forest, speeding past obstacles knowing intuitively that - given a certain forest density - it can always find an opening through the trees.

Frazzoli believes that given some general information about the density of obstacles in a given environment, a robot could conceivably determine its maximum safe speed. His team has developed mathematical models of various forest densities, calculating the maximum speed possible in each obstacle-filled environment.

Adjusting the model to represent varying densities, the team was able to calculate the probability that a bird would collide with an obstacle while flying at a certain speed. The also discovered that for any given forest density, there exists a critical speed above which a collision is certain.

However, Frazzoli said: "If I fly slower than that critical speed, then there is a fair possibility that I will actually be able to fly forever."

Frazzoli is now comparing actual birds' behaviour with the model's predictions. So far, he said preliminary results with pigeons are "very encouraging".

Frazzoli also wants to see how close humans can come to such theoretical speed limits. He and his students are developing a first-person flying game to test how well people can navigate through a simulated forest at high speeds.

"What we want to do is have people play, and we'll just collect statistics," Frazzoli said. "The question is, how close to the theoretical limit can we get?"