Two-legged robot can take a walk in the grass

A two-legged robot that can keep its balance and walk in an outdoor field, full of lumps, bumps and uneven terrain, is three times more energy-efficient than any other human-sized bipedal robot, scientists say.
Researchers at Oregon State University last week successfully field-tested for the first time the locomotion abilities of the two-legged robot with technology that they believe heralds the running robots of the future.
The test demonstrated that their 'ATRIAS' robot can move quite nicely, keep its balance and withstand mild blows from a bouncing rubber ball, while taking a walk in the grass, up and down hill, and over varying terrain at a normal walking speed of a little more than three miles per hour.

As a bipedal robot that was biologically inspired to mimic the spring-legged action of animals, the researchers said this is the closest a machine has yet come to resembling human locomotion.
The human-sized robot had six electric motors powered by a lithium polymer battery about the size of a half-gallon of milk, which is substantially smaller than the power packs of some other mobile robots.
This is made possible by the energy efficiency of its elastic leg design and the energy retention that's natural to animal movement.

"Animals with legs sort of flow in the energy used, in which retained kinetic energy is just nudged by very efficient muscles and tendons to continue the movement once it has begun," said Jonathan Hurst, an Oregon State associate professor of mechanical engineering, and director of the Dynamic Robotics Laboratory in the OSU College of Engineering.

"That's part of what's unique about ATRIAS - not just that it can walk, and will eventually run - but that it's doing so with animal-inspired fluidity of motion that is so efficient," Hurst said.
"This will ultimately allow a much wider range of robotic uses and potential than something which requires larger amounts of energy," he said.
In the tests, the robot was tethered to a safety harness on a supporting frame that rolled along with it - not to supply energy or aid in walking, but just to help catch it if it fell, which it did a couple times due to sensor glitches.

"It already appears that ATRIAS is three times more energy-efficient than any other human-sized bipedal robot," said Christian Hubicki, an OSU postdoctoral scholar working with Hurst.
"And this was the first time we've been able to show its abilities outside, in a far more challenging environment than anything in a laboratory," Hubicki said.