Diana Chin, a graduate student at the university, uses five high-speed cameras to film small birds called parrotlets as they attempt to land on perches made of varying materials, including the non-stick coating Teflon, foam and sandpaper.
“Modern aerial robots usually need either a runway or a flat surface for easy takeoff and landing. For a bird, almost everywhere is a potential landing spot, even in cities," says Chin, who is part of the lab of David Lentink, assistant professor of mechanical engineering. “We really wanted to understand how they accomplish that and the dynamics and forces that are involved.”
Even advanced robots are nowhere near as good at grasping objects as most animals, particularly when dealing with uncertainty in the form of varying shapes, sizes and textures.
Lentink, a senior author on a recent paper published in the journal eLife, likens the task of landing on a Teflon-coated perch to an asking an Olympic gymnast to land on non-stick high bars without chalking their hands. But the birds made it seem effortless.
"When we look at a person running, a squirrel jumping or a bird flying, it is clear that we have a long way to go before our technology can reach the complex potential of these animals, both in terms of efficiency and controlled athleticism," says William Roderick, a graduate student in mechanical engineering in the Lentink lab. “Through studying natural systems that have evolved over millions of years, we can make tremendous strides toward constructing systems with unprecedented capabilities.”
Each perch was fitted with a six-axis force and torque sensor, to capture the forces exerted by the birds when they landed. “When we first processed all of our data on approach speed and the forces when the bird was landing, we didn't see any obvious differences," Chin says. "But then we started to look into kinematics of the feet and claws - the details of how they moved those - and discovered they adapt them to stick the landing.”
The extent to which the birds wrapped their toes and curled their claws varied depending on what they encountered upon landing. On rough or squishy surfaces - such as the medium-size foam, sandpaper and rough wood perches - their feet could generate high squeeze forces with little help from their claws. On perches that were hardest to grasp - the floss-silk wood, Teflon and large birch - the birds curled their claws more, dragging them along the perch surface until they had secure footing.
It’s hoped that the work could lead to robots that can land better on a variety of different surfaces. “If we can apply all that we learn, we can develop bimodal robots that can transition to and from the air in a wide range of different environments and increase the versatility of aerial robots that we have today,” says Chin.
On that front, Roderick is working on mechanisms that would mimic the way the birds grip. "One application of this work that I'm interested in is having perching robots that can act as a team of tiny little scientists that make recordings, autonomously, for field research in forests or jungles," he says. "I really enjoy drawing from the fundamentals of engineering and applying them to new fields to push the limits of what has been previously achieved and what is known."