efficient -- which will save batteries in the long run. "For a robot to ever be practical it has to be able to run for a while," Ruina told a news conference sponsored by the American Association for the Advancement of Science. The concept is simple, said Ruina -- the legs act like sticks attached to hinges, and swing back and forth with a pendulum motion. The concept has been used for more than 100 years to design toys that will "walk" down a slope with no propulsion. "Mainstream" robots, on the other hand, have every movement carefully controlled and powered. Steven Collins of Cornell, who is now at the University of Michigan, added a tiny bit of motorized propulsion at the robot's ankles. "At each step it pushes off with its back foot," Collins said. "This is similar to how we think people walk." --More 0102 Local Time 2202 GMT
