5 paths to the walking, talking, pie-baking humanoid robot

Path 2: Locomotion

After depositing my bag in a closet, Jeeves walks toward the basement, where Jack keeps an extra fridge for drinks. "Run along and fetch that beer,"
I yell after Jeeves, starting to enjoy this whole robo-servant thing. Jeeves interprets my command literally-stupid robot!-and accelerates to a jog. He turns the corner into the kitchen and hurries down the basement steps, grabs a bottle, and sprints back upstairs.

Today's best-known humanoid, the mini Storm Trooperâ€like Honda Asimo, can run, climb stairs, even do the hula. And because it's designed not to fall over, it's safe. But with motors in every joint controlling every motion of its limbs, Asimo devours energy. Its battery life can be as short as 30 minutes; it wouldn't last through a dinner party.

Recently, though, roboticists have started approaching biped locomotion from another angle. Last year, several groups working in concert introduced machines designed to walk in the loose, free-swinging fashion of humans. Instead of driving all the motions with motors and carefully calibrating each step, the leg action is more like that of a pendulum. The result is walking robots that are much more efficient. Unfortunately, they're also much less stable. Andy Ruina, the Cornell engineer who led one of the teams, is quick to criticize his group's robot: "It can only do one thing. It can just walk in a straight line. It can't even stand up."

For a humanoid to be able to race through a house without falling over and finish its chores on a single charge, researchers need to find the optimal point between stability and efficiency. While some roboticists point, as a future solution, to the development of artificial muscles-materials that contract or expand in response to an electric charge or laser pulse-new, improved actuators could provide a more immediate fix. If smaller, less power-hungry systems were driving Asimo's legs, it wouldn't need to run to the recharging station as often.