It's never been completely clear how human beings accomplish the taken-for-granted phenomenon we call walking, but findings published in the Journal of Experimental Biology outline a specific interaction between the ankle, knee, muscles and tendons.
Those interactions improve the understanding of a leg moving forward in a way that maximizes motion while using minimal amounts of energy, researchers in the College of Engineering at Oregon State University said.
"Human walking is extraordinarily complex and we still don't understand completely how it works," said mechanical engineering Professor Jonathan Hurst, and expert in legged locomotion in robots. "There's a real efficiency to it -- walking is almost like passive falling. The robots existing today don't walk at all like humans, they lack that efficiency of motion and agility."
In human walking, he said, the first motion is a combination of an "alleviation" phase in which the trailing leg is relieved of the burden of supporting the body mass, then a "launching" phase in which the knee buckles, allowing the rapid release of stored elastic energy in the ankle tendons, like the triggering of a catapult.
Walking robots don't do this, Hurst said, instead using force to "swing" the leg forward from something resembling a hip joint. While functional, it's neither energy-efficient nor agile, and nothing like the human process, seen as a goal for robots.
"We still have a long way to go before walking robots can move with as little energy as animals use," he said. "But this type of research will bring us closer to that."