Agile Hawk Inspires UAV Design

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Goshawks can fly at top speed through dense forest, and researchers at the Massachusetts Institute of Technology are studying the birds to help design unmanned aerial vehicles that will fly at high speeds through city streets and other crowded environments. Emilio Frazzoli, an associate professor of aeronautics and astronautics at MIT, said today's drones fly just fast enough to be able to stop within the field of view of their sensors. "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," Frazzoli says. "Which is not very fast." The trick the goshawk employs is to gauge the density of the forest, and speed past obstacles, knowing intuitively that, given a certain density, it can always find an opening through the trees.

Frazzoli's research team, which includes mathematicians and biologists, created a model to represent varying densities of trees, and calculated the probability that a bird would collide with a tree while flying at a certain speed. The team found that, for any given forest density, there exists a critical speed above which there is no "infinite collision-free trajectory." In other words, the bird is sure to crash. Below this speed, a bird has a good chance of flying without incident. "If I fly slower than that critical speed, then there is a fair possibility that I will actually be able to fly forever, always avoiding the trees," Frazzoli says.