Flying Like a Bird


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Swifts were selected for the flight study because they can control their glide performance with morphing wings.

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Mechanical engineering doctoral students interested in designing small flying robots at Stanford University are getting an unusual combination of training: Their aerospace classes are supplemented with a heavy dose of biology in a lab focused on the study of birds.

The students spend many hours in the bird-inspired design lab, some designing the robots and others studying and training birds to better understand the mechanics of birds in flight. The reason? Birds can maneuver much better through clutter, around buildings, or through trees and in turbulence than any small robots made today. Engineers believe that, much like the Wright Brothers learned from observing birds in flight, they can find solutions from nature by studying fluid dynamics.

Learning from Nature

The laboratory is under the direction of David Lentink, assistant professor of mechanical engineering, who set up the unusual testing ground a year ago when he joined Stanford from Wageningen University in his native Netherlands.

“What’s so exciting about this is that there are very few engineering labs around the world where vertebrates are studied and it’s going to allow these new engineers to learn from nature and integrate this knowledge into their design process,” said Dr. Lentink, who holds bachelor and masters degrees in aerospace and a doctorate in experimental zoology.

The only biological training that most engineers get is bioengineering, which is focused on cells and molecules, he said, noting that in his lab, students are looking at the whole organism and how it mechanically functions. “That is a topic that resonates because engineers are interested in whole systems, how they run and how to design them.”

David Lentink presenting the RoboSwift at TEDx Amsterdam. Image: Lentinklab.Stanford.edu

Having all activities conducted in the same lab encourages close collaboration among the students studying the birds and those designing the next generation of small flying robots, which Dr. Lentink expects will include the first small flying robot that can both flap and morph its wings so that it can fly like birds do. Previous robots could do one or the other but not both and do not have the grace and ease of a bird in flight particularly in strong turbulence. The benefit of a flapping wing is that it facilitates maneuvering through turbulence and clutter, but if the wings don’t also fold, a bird (or flying robot) could not go through small spaces, such as heavy foliage or narrow spaces between buildings.

The bird research involves training and observing birds in flight in the lab as well as taking video of birds in flight outside with an ultra high-speed camera. The students learn different types of flight mechanics from different species of birds and apply the most useful natural mechanisms to their robotic designs. For example, hummingbirds are excellent at hovering, and swifts are excellent at soaring. In the lab, one grad student is training parrotlets to fly from one perch to another and through narrow channels at the command of a hand signal, which gives them insight into aerodynamic force measurement. “By looking at such specialization, you can learn about efficiency,” Dr. Lentink said.

Growing Interest

The lab continues to expand its equipment and tools for additional research opportunities that Dr. Lentink hopes will soon be ready to present to some of the major manufacturers of micro air vehicles, such as Aerovironment, Honeywell, Lockheed Martin, Prox Dynamics, and others. To enable even more insight, the lab recently added an advanced flow measurement system that helps show how birds’ wings manipulate airflow with their wings to fly slower, and in the works is a high quality wind tunnel for the lab birds that will give them more exercise and allow them to fly for longer times.

 

Much of the work that has been done on micro air vehicles has been driven by military spending, but there is growing interest for use in other ways. “The market is growing and growing,” Dr. Lentink said. His own motivation is to help humans in need to aid in search and rescue, for example, to help firefighters pinpoint exactly where a fire is or to aid in rescue operations in natural disasters particularly in urban areas that are difficult to survey, whether because of continuing bad weather or otherwise.

“We have mastered how to build really big aircraft, and we can fly to the moon but we aren’t capable of flying through a tree,” Dr. Lentink said. “I’m really excited as an engineer by what we have been able to engineer. But it’s still amazing to see that there are things that we can’t do that a bird can.”

Nancy S. Giges is an independent writer.

What’s so exciting about this is that there are very few engineering labs around the world where vertebrates are studied.

Prof. Dr. David Lentink, Stanford University

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August 2013

by Nancy S. Giges, ASME.org