Parrotlets flying through a field of lasers and microparticles helped test three popular models that predict the lift generated by flying animals. The work could help develop better flying robots.
The protective goggles are tight, the chin strap secure. Conditions are calm and the lasers are ready; the air is infused with tiny aerosol particles that are primed to scatter and track at the slightest disruption. Wait for the signal.
The researcher points. The bird flies!
It’s just another day at the office for a parrotlet named Obi.
As a graduate student working with Stanford mechanical engineer David Lentink, Eric Gutierrez trained this member of the second smallest parrot species in order to precisely measure the vortices it creates during flight. Their results, published in the Dec. 6 issue of Bioinspiration and Biomimetics, help explain the way animals generate enough lift to fly and could have implications for how flying robots and drones are designed.
“The goal of our study was to compare very commonly used models in the literature to figure out how much lift a bird, or other flying animal, generates based off its wake,” said Diana Chin, a graduate student in the Lentink lab and co-author of the study. “What we found was that all three models we tried out were very inaccurate because they make assumptions that aren’t necessarily true.”
Scientists rely on these models, developed to interpret the airflow generated by flying animals, to understand how animals support their weight during flight. The results are commonly referenced for work on flying robots and drones inspired by the biology of these animals. Bio-inspired robots are a specialty of Lentink – his students developed the first flapping robot that can take off and land vertically like an insect and a swift-like robot with wings that deform as it swoops and glides.
Birds wearing goggles
For this experiment, Gutierrez, the study’s lead author and former graduate student in the Lentink lab, made parrotlet-sized goggles using lenses from human laser safety goggles, 3D-printed sockets and veterinary tape. The goggles also had reflective markers on the side so the researchers could track the bird’s velocity. Then he trained Obi to wear the goggles and to fly from perch to perch.
Once trained, the bird flew through a laser sheet that illuminated nontoxic, micron-sized aerosol particles. As the bird flew through the seeded laser sheet, its wing motion disturbed the particles to generate a detailed record of the vortices created by the flight.