DURUS displays the heel strike and toe push-off that is a key feature of human walking. Photograph by Christian Hubicki, courtesy of Georgia Tech.
Georgia Institute of Technology (Georgia Tech) researchers, in collaboration with the robotics division of SRI International, a nonprofit research institute headquartered in Menlo Park, California, have designed what they say is the most efficient-walking robot ever created. DURUS strolls like a person. Its legs and chest are elongated and upright. It lands on the heel of its foot, rolls through the step, and pushes off its toe. It’s outfitted with a pair of size 13 shoes as it walks under its own power on a treadmill in the team’s AMBER (Advanced Mechanical Bipedal Experimental Robotics) Lab. These advances have the potential to usher in the next generation of robotic assistive devices like lower-limb prostheses and exoskeletons that can enable people with mobility impairments to walk with ease.
“Our robot is able to take much longer, faster steps than its flat-footed counterparts because it’s replicating human locomotion,” said Aaron Ames, PhD, director of the Georgia Tech lab and an associate professor in the George W. Woodruff School of Mechanical Engineering and School of Electrical and Computer Engineering. “Multicontact foot behavior also allows it to be more dynamic, pushing us closer to our goal of allowing the robot to walk outside in the real world.”
The traditional approach to creating a robotic walker is similar to an upside-down pendulum. Researchers typically use comparatively simple algorithms to move the top of the machine forward while keeping its feet flat and grounded. As it shuffles along, the waist stays at a constant height, creating a hunched look. This prevents these robots from moving with the dynamic grace present in human walking and prevents them from efficiently propelling themselves forward.
The Georgia Tech robot has a pair of metal feet with arched soles and is powered by fundamentally different algorithms than most robots. The robot is equipped with springs between its ankles and feet, similar to elastic tendons in people, which allows for a walking gait that stores mechanical energy from a heel strike to be later reclaimed as the foot lifts off the ground.
This natural gait makes DURUS efficient. Robot locomotion efficiency is universally measured by a cost of transport, or the amount of power it uses divided by the machine’s weight and walking speed. Ames said the best humanoids have a cost of transport of about 3. DURUS’ cost of transport is 1.4, all while being self-powered: It’s not tethered by a power cord from an external source.
“Flat-footed robots demonstrated that walking was possible,” said Ames. “But they’re a starting point, like a propeller-powered airplane. It gets the job done, but it’s not a jet engine. We want to build something better, something that can walk up and down stairs or run across a field.”
Editor’s note: This story was adapted from materials provided by Jason Maderer and Georgia Tech.
