The creators of the Roboy robot wanted it to move as much like a human as possible, using a skeleton of 3D-printed bones and joints, tendons -- and coiled springs in muscles.
The springs are there to give Roboy's movements fluidity. One reason most humanoid robots still move, well, robotically is that their movements are too stiff.
Human muscles are springy, so if we are nudged or bumped out of the way, we gently bounce back, and if we jump or fall, we can absorb the shock, said Rafael Hostettler, manager of the Roboy project at the Swiss Federal Institute of Technology Zurich.
It's possible to model that springiness in software, so a robot can use sensors to detect when there is resistance to its movements, and modify the force applied -- but there's inevitably a lag in the processing of such inputs, so the movement will not be as natural as ours, Hostettler said at the Cebit trade show in Hanover, Germany.
The springiness of our muscles also allows us to put more energy into movements such as throwing, building up the tension in one muscle by pulling against another, and then suddenly letting go. That's harder to model in software, and so in their robot's muscles the Zurich researchers decided to use real springs -- thick, coiled ones of the kind seen in a car's suspension, only smaller.
Roboy's musculature is much like our own, with paired actuators operating in opposition at each joint and wires in place of ligaments. Other robots might use a single motor able to pull in either direction. The resistance offered by the 12 motors in each of Roboy's arms feels almost human when shaking hands -- although the grip of the hand, with only one motor, is less natural.
The work is part of a wider European research project called Myorobotics, which aims to create robots that are cheaper to build and safer to be around -- the idea is that being struck by a springy robot will be less dangerous than a hit from a solid one.
If Roboy could stand, it would be 1.42 meters tall, but its leg and foot muscles are not strong enough to balance its 30-kilogram weight, so it can only sit.
The most striking thing about Roboy is its enormous head, with glowing eyes that, in a cartoon touch, turn red when the robot is simulating anger. A projector inside the head also animates the lips and can give the impression the robot is blushing.
Roboy took around nine months to build. Beyond its role as a proving ground for robotics technologies, the researchers have other applications in mind. "We see it as a training tool for doctors to learn standard tests for stroke diagnosis," said Hostettler. That's something difficult to learn from videos or books, he said, as it requires doctors to get a feeling for the way patients react to physical stimuli.
The robot's ability to show different facial expressions will be useful for that project, but its main purpose is as a means to communicate about robot research, he said. The crowds stopping to stare and shake hands with Roboy at Cebit prove his point.
Peter Sayer covers open source software, European intellectual property legislation and general technology breaking news for IDG News Service. Send comments and news tips to Peter at email@example.com.