It was just a few steps, clunky and deliberate, like a toddler's waddle. But to a far-flung group of engineers, soldiers, and science fiction fans, these strides, on a treadmill inside a University of California, Berkeley laboratory, couldn't have been more profound. Here was a man, walking naturally, more or less, with the help of a set of mechanical muscles wrapped around his legs – a real-life exoskeleton.
The ur-geek author Robert Heinlein first dreamed up the idea of soldiers stepping into suits of powered armor, to make them stronger and faster, in his 1959 classic Starship Troopers. Sigourney Weaver cemented the exoskeleton in the collective consciousness in 1986, when she donned a metallic over-suit in Aliens, and kicked some slimy, interstellar ass.
In the real world, though, researchers struggled to replicate Sigourney's heroics. The exoskeletons they built were too stiff, too unnatural in their gait. Engineers would try to have them move as much like a human as possible. It never seemed to work.
The problem was that researchers were trying too hard, Berkeley engineering professor Homayoon Kazerooni finally realized. When people walk, they make an endless series of unconscious calculations and corrections to keep their stride. It's way too complicated a task for machines to handle. So instead of pre-programming the exoskeleton's every step, Kazerooni decided to let go. He set his exoskeleton up with a set of 40 sensors, and let it follow wherever the person inside wanted to wander.
The result, called BLEEX (short for "Berkeley Lower Extremity Exoskeleton") is a set of modified combat boots, attached to what look like metal braces that snake up the sides of the legs. Those connect with a tough plastic vest and backpack, where the exoskeleton's brain – a Pentium-5 equivalent processor -- sits.
About 70 pounds of stuff can be crammed into the pack. But that load only feels like five pounds or so, once the exoskeleton is turned on; the mechanical legs pick up the rest. (BLEEX 2, slated for June, should be able to carry 150 pounds, and amble at a four mile-per-hour clip.) The Pentagon – which has been funding much of Kazerooni's research – wants the machine to ease the burden on G.I.s, who routinely haul more that a hundred pounds of gear into battle.
But Kazerooni sees his exoskeleton as more than just a "war machine." The mechanical legs might someday help the elderly get around, he hopes. Replacing grandma's walker is a long way from Aliens. But at least it's real.
I've got an itty-bitty article in tomorrow's New York Times Magazine, on real-life exoskeletons. You can read it 
