With an eye toward building better running robots, researchers analysed some of nature's most energy efficient animals - running birds.
In the study, they outlined how running birds have achieved an impressive ability to run while minimising energy cost, avoiding falls or injury, and maintaining speed and direction.
"Birds appear to be the best of bipedal terrestrial runners, with a speed and agility that trace back 230 million years to their dinosaur ancestors," said Jonathan Hurst, associate professor and robotics expert at Oregon State University's (OSU) College of Engineering in the US.
In collaboration with Monica Daley at the Royal Veterinary College in London, researchers studied five species of birds and developed a computer model in OSU's Dynamic Robotics Laboratory.
The researchers began the study with a hypothesis that body stability would be a priority, since it might help avoid falls and leg injuries.
That was not what they found though.
"Running birds have a different definition of stability - they do avoid falls, but also allow their upper bodies to bounce around some, just so long as they do not fall," Daley said.
Like a scrambling football runner, their leg motion may sometimes speed up or slow down, in the interest of staying upright, dealing with obstacles and generally staying on course to where they are going.
The process is not always pretty but it is functional.
"What robots could learn from running birds is that it is okay to deviate from normal steady motions because it does not necessarily mean you are going to fall or break something," Hurst added.
Robotic control approaches "must embrace a more relaxed notion of stability, optimising dynamics based on key task-level priorities without encoding an explicit preference for a steady gait," the researchers concluded.
The paper was published in the Journal of Experimental Biology.
