Better Running Robots May Stem from Research on Birds

Researchers from Oregon State University and the University of London are studying birds to gain insight into how to make better running robots.

Researchers observe the motions used by this turkey hopping over an obstacle in order to model its behavior.

Running robots of the future may get its leading edge from birds, according to a new study by researchers at Oregon State University and the University of London’s Royal Veterinary College, among other collaborators.

The study outlines how running birds have achieved “an impressive ability to run while minimizing energy cost, avoiding falls or injury, and maintaining speed and direction.” Studying these qualities, according to the researchers, could help design better running robots.

“Birds appear to be the best bipedal terrestrial runners, with a speed and agility that may trace back 230 million years to their dinosaur ancestors,” said Jonathan Hurst, an associate professor in the OSU College of Engineering.

Running birds range in size, from tiny quails to an ostrich that has 500 times as much body mass. Most, but not all, can fly, but spend most of their lives on the ground, and they don’t always look the most graceful when they run, the researchers noted. Still, the birds are able to maximize results, like saving energy and not breaking a leg.

“These animals don’t care that they appear a little unstable or have a waver in their gait,” Hurst said. “Their goal is to limit peak forces, avoid falling, be safe and be as efficient as possible. If their upper body seems to lurch around a little as a result, that’s OK. What they are accomplishing is really quite elegant.”

The researchers found that a wide variety of ground-running bird species with very different body sizes use essentially the same strategy to accomplish these sometimes conflicting tasks. In order to hop over obstacles on uneven ground, they use a motion that’s about 70 percent a “vaulting” movement as they approach the obstacle, and 30 percent a more-crouched posture while on top of the obstacle.

The researchers studies five species of birds, including turkeys, and developed a computer model in Oregon State University’s Dynamic Robotics Laboratory that closely matches that behavior.

“We should ultimately be able to encode this understanding into legged robots so the robots can run with more speed and agility in rugged terrain,” said Christian Hubicki, a doctoral student at Oregon State who co-authored the study. “These insights may also help us understand the walking and running behaviors of all the common ancestors involved, including theropod dinosaurs such as the velociraptor.”

The researchers began the study with a hypothesis that body stability would be a priority, since it might help avoid falls and leg injuries, according to Oregon State University. However, that’s not what they found.

Instead, running birds have a different definition of stability, the university noted. They do avoid falls, but also allow their upper bodies to bounce around a little.

So how can this build a better robot? Current robots are usually built with an emphasis on total stability, which often includes maintaining a steady gait. This can be energy-intensive and sometimes limits their mobility, according to the researchers. The study shows that robots can deviate from normal steady motions. Robotic control approaches “must embrace a more relaxed notion of stability, optimizing dynamics based on key task-level priorities without encoding an explicit preference for a steady gait,” the researchers said in their conclusion.

Courtesy Oregon State University 

This model outlines the forces at work as a turkey hops over an obstacle.

“The running robots of the future are going to look a lot less robotic,” Hurst said. “They will be more fluid, like the biological systems in nature. We’re not necessarily trying to copy animals, but we do want to match their capabilities.”

The study was published in late October in the Journal of Experimental Biology.

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