Engineers looking for inspiration for better drone camera design might want to set their gaze toward lovebirds.
Lovebirds are famous for their ability to quickly maneuver through densely cluttered airspace, and Stanford engineers now show that this is probably made possible by the birds' ability to turn their heads at a speed that is tops in the animal world.
"During rapid flight through densely cluttered forests every split second counts. Having more time to see and react to your environment gives you an edge in making the right decision," said David Lentink, an assistant professor of mechanical engineering at Stanford. "Clearly, there are evolutionary benefits for behaviors that help avoid crashing in complex environments."
Lentink and his colleagues used stereo high-speed cameras to film the birds as they took off and performed a rapid turning maneuver before landing on the initial perch. Analysis of the stereo videos showed that the birds could turn their heads at speeds reaching 2,700 degrees per second, as fast as insects, and orient to a new target with incredible accuracy.
High-speed video reveals how lovebirds keep a clear line of sight during acrobatic flight. Stanford's David Lentink says this strategy could be applied to drone cameras to improve visual systems. (Video: Courtesy Lentink Lab)
"They are almost four times faster than humans at solving a similar visual task," said Daniel Kress, a postdoctoral fellow in Lentink's lab and first author on the research paper. "Basically, if lovebirds could spin their head a full 360 degrees, they could do it so fast that it would go unnoted by a blinking human."
The findings are published in the online journal PLOS: ONE.
The whole movement occurs so quickly that there's no chance for the birds to get dizzy; similar to a blinking human, the birds are effectively blind during the turn. Lentink and Kress speculate that smaller birds with lighter heads might turn their heads even faster but that lovebirds' ability pushes the speed limit of what is physically possible.
The work could inform the design of drone vision systems in a couple of ways. The researchers noticed that the birds only began turning their heads during the end of the wing downstroke, maximizing the length of time that their line of sight would be unobscured. The research suggests that rotating the camera gimbal on a drone faster during a turn could improve visual quality.
"If drone gimbals would be as fast as the neck of a lovebird, making a saccade of 60 degrees in about 40 milliseconds, they would be able to reorient the camera in a single frame, since typical drone cameras operate at about 30 frames per second," Lentink said. "With only one frame blurred, the videos would essentially be free from blur due to camera movement, even during dramatic maneuvers."