Two-legged robot that walks like an animated character

In an interesting development, Disney researchers have found a way for a robot to mimic an animated character's walk.

Beginning with an animation of a diminutive, peanut-shaped character that walks with a rolling, somewhat bow-legged gait, Katsu Yamane and his team at Disney Research Pittsburgh analysed the character's motion to design a robotic frame that could duplicate the walking motion using 3D-printed links and servo motors, while also fitting inside the character's skin.

They then created control software that could keep the robot balanced while duplicating the character's gait as closely as possible.

"The biggest challenge is that designers don't necessarily consider physics when they create an animated character," said Yamane, senior research scientist.

Roboticists, however, wrestle with physical constraints throughout the process of creating a real-life version of the character.

"It's important that, despite physical limitations, we do not sacrifice style or the quality of motion," Yamane added.

The robots will need to not only look like the characters, but move in the way people are accustomed to seeing those characters move.

Yamane and Joohyung Kim of Disney Research Pittsburgh and Seungmoon Song, a Ph.D. student at Carnegie Mellon University's Robotics Institute, focused first on developing the lower half of such a robot.

"Walking is where physics matter the most. If we can find a way to make the lower half work, we can use the exact same procedure for the upper body," Yamane said.

By studying the dynamics of the walking motion in simulation, the researchers realised they could mimic the motion by building a leg with a hip joint that has three degrees of freedom, a knee joint with a single degree of freedom and an ankle with two degrees of freedom.

Because the joints of the robot differ from what the analysis showed that the animated character had, the researchers couldn't duplicate the character's joint movements, but identified the position trajectories of the character's pelvis, hips, knees, ankle and toes that the robot would need to duplicate.

To keep the robot from falling, the researchers altered the motion, such as by keeping the character's stance foot flat on the ground. They then optimised the trajectories to minimise any deviation from the target motions, while ensuring that the robot was stable.

The researchers are scheduled to describe the techniques and technologies they used to create the bipedal robot at the IEEE International Conference on Robotics and Automation, ICRA 2015, from May 26 to 30 in Seattle.