Science

Me And My Exoskeleton: The Trick To Super Strength

When I first see the Human Universal Load Carrier (HULC), it is hanging limply from the ceiling by a strap attached to its neck, dangling over a treadmill. I can’t wait to try it on.

It has got two spindly black legs attached to a backpack with long rectangular batteries on the shoulder blades and an armoured computer in the small of its back. Amusingly, it has radiator fins instead of buttocks. The whole machine looks sort of like a human skeleton, because the legs and hips have joints that mimic the movement of human limbs.

In fact, when you strap your legs into its legs, you can walk, run, kneel, squat, dance or whatever — the exoskeleton has a range of motion equal to that of a human being. You move and it moves with you. But once on, it allows a regular geek to haul a 90kg backpack as if it weighed as much as a couple of physics textbooks.

Now we’re talking.

Let me explain how I got here. In late 2007, a production company called me and asked if I’d like to host a television show for the History Channel. My job, they said, would be to “explain, uh, how things work”. During my cable TV stint, I raced lawn mowers in Florida, was shot at with a rifle while inside an armoured car in Texas, and — best of all — I piloted an honest-to-God lower-body exoskeleton with the researchers at Berkeley Bionics in California.

And so, on an otherwise perfectly normal summer day, I dropped by a nondescript brick building where a group of former graduate students from the University of California at Berkeley were busy making last-minute tweaks to a dead-black titanium exoskeleton, and they invite me to try it on.

My first impression: The straps are too big. The HULC was built with military money and it is designed to fit army guys. And soldiers have big thighs, apparently. I yank the Velcro straps as tight as possible, then strap my shoes into its open-toed boots. I shrug on the backpack and clasp the chest strap. I am now wearing an exoskeleton. Turned off, the device is heavy; it’s like wearing a scuba tank on dry land. But once the researchers switch it on, HULC stands up on its own — with me inside.

At this point, I’m still hanging from the ceiling, so I can’t fall down. I can’t feel any extra weight because the exoskeleton frame supports itself (about 14kg), as well as any attached backpacks. We turn on the treadmill and I cautiously bend my knee. Nothing happens. A half-second later, force sensors detect my leg pushing against the exoskeleton and the machine jerkily bends its knee. The delay is disconcerting — I can barely walk.

A couple of minutes later, the treadmill is rolling and I’m humping along like Forrest Gump in his special shoes. Like a video game that breaks the human face down into just a few polygons, my new exo-walk consists of just a few gross movements. Knee lift, foot out, foot down. Repeat. It lacks the fluidity of my normal walk, but I don’t fall. And oh yeah, every movement is accompanied by the loud whine of electric motors. Each step sounds like reeee (that’s the motor) followed by ker-thump as my foot touches down.

Reeee-ker-thump. Reeee-ker-thump. “Drop the gun,” I say. “You are under arrest.” (Yes, that’s a Robocop joke, and it is hilariously funny.)

After the practice run, it’s time to hit the hallway. I immediately notice that my gait is becoming more fluid. I can even balance on one leg. This is because the machine is learning to anticipate my every move. The HULC is no dumb brute. It is constantly sensing the force of my movements and forming a model of how I walk. It’s getting to know me, exoskeleton-style.

The HULC is a finished product, along with a slew of other exoskeletons, such as the full-body Sarcos and the medically oriented Hal-5. But make no mistake, scientists have been trying to build robotically augmented limbs since well before Sigourney Weaver used a power lifter to kick alien butt.

Designs for wearable mechanical skeletons have been evolving since the 1960s when General Electric foresaw using the Hardiman for heavy loading in factories. Sadly, the original designs were infeasibly power-hungry, requiring heavy batteries that pulverised the payload-to-system weight ratio. Even worse, the old designs didn’t degrade gracefully, which is a nice way of saying that when the power failed, they would fall to the ground and rip your limbs off. Ouch.

But today, exoskeletons have become a reality and, according to the researchers, they don’t suffer from the limb-ripping drawbacks of yesteryear.

Once my gait cycles a few times, HULC has formed a complete model. A researcher informs me that from this point onward, the exoskeleton can cycle through my walk all by itself. Yes, by itself. This means that I could fall asleep and it would keep walking, dragging my legs through the motions. Suddenly, I imagine a platoon of snoozing soldiers fast marching non-stop through dark jungles at an average speed of 10km/h, a fast jog.

That’s creepy. Plus, I’m sweaty and exhausted; it’s time to take off the exoskeleton.

A couple of yanks on the Velcro straps and I’m out. But my legs feel dead, like I just spent an hour jumping on a trampoline. My helpful researcher lets me know that the goal of the exoskeleton is to minimise metabolic cost. Using your muscles costs oxygen, and the brain is stingy — it uses just enough oxygen to get the job done. Once your brain figures out that it needs less oxygen to move (thanks to the exoskeleton), it sends less oxygen. Without the exoskeleton, my brain isn’t giving me enough juice to use my limbs normally, hence the weak legs. Luckily, it only takes a few minutes to go back to normal. Thank you, brain.

Despite the amazingness of it all, I have to say it felt clumsy and weird to lock my limbs into the machine’s cold, robotic embrace. You won’t catch me walking down any staircases in an exoskeleton. At least, not without a lot more practice.

Daniel H. Wilson is the author of several books, including How to Survive a Robot Uprising, Where’s My Jetpack?, and Bro-Jitsu: The Martial Art of Sibling Smackdown. Wilson earned his PhD in Robotics from Carnegie Mellon University in Pittsburgh. His first novel, Robopocalypse, is forthcoming from Doubleday.

Video courtesy of The History Channel