The next-gen exoskeletons promising paraplegics will walk again


The latest robotic technology tackles the surprisingly difficult task of mimicking human gait, writes Cathal O’Connell.


Illustration by Anthony Calvert

The opening kick of the 2014 FIFA World Cup was not taken by a professional footballer; it was taken by a paraplegic. Juliano Pinto, paralysed from the waist down, took the kick using a robotic ‘exoskeleton’ to power his legs. The suit was experimental, but commercial exoskeltons are beginning to enter the marketplace, giving paraplegic patients who can afford the price tag the power to walk again.

Though we rarely give it a conscious thought, walking is deceptively complex movement; a kind of continual falling forward involving tens of muscles operating in smooth synchronicity to ‘catch’ the body at each step. Walking has been incredibly difficult to reproduce in machines. Most robots, and robotic exoskeletons, still ‘shuffle’ slowly and steadily from one foot to the other.

The A$130,000 ReWalk Personal 6.0, from German firm ReWalk Robotics, is one of a new generation of exoskeletons that more naturally mimics human gait. When the user tilts forward, ReWalk’s gyroscope senses the motion and takes a step. Keep repeating the movement and ReWalk can reach about 2.5 km/h, the fastest on the market. Even patients with complete paralysis of the legs can stand up, walk, turn, and climb stairs, though with the help of crutches for balance.

The Phoenix Exoskeleton, by SuitX, a new spin-out from the University of California at Berkeley, is more of a budget model. At about half the cost of ReWalk, the Phoenix lacks the auto-step function. Instead the user controls it by tapping buttons on a pair of crutches. Top speed depends on the user, but can reach up to 1.7 km/h.

It’s been a long and tortuous path to reach this milestone in exoskeleton development. As long ago as the 1960s, General Electric teamed up with the US armed forces to build the Hardiman, a bulky metal suit designed to amplify a soldier’s strength 25-fold. But the technological limitations of the age made the device so erratic and dangerous, it was never tested with a person inside.

More recent efforts at building supersuits have fared only a little better. Lockheed Martin spent more than a decade developing their Human Universal Load Carrier (HULC) for the US military. HULC was supposed to allow US soldiers carry 91kg backpacks for hours without tiring. But the project was shelved in 2012 as the strap-on metal frame forced wearers into a sightly unnatural gait that actually increased fatigue on some muscles.

But the latest exoskeletons are finally managing to work in lockstep with natural biomechanics of walking. Harvard’s Biodesign lab threw out the clunky metal components and are building soft exoskeletons instead, using regular clothing fabric. Their device, funded by the Defense Advanced Research Projects Agency (DARPA), looks a bit like a pair of spandex pants strapped to a climbing harness. Cables snake from a motorised belt down the user’s legs, following the curve of the user’s muscles. Take a step, and the machine works in harmony with the wearer’s calf muscles to drive the body forward. Counterintuitive as it sounds, the soft exosuit reduces the energy expended through walking by about 23%.

While soft exosuits might enhance the natural muscle motion of able bodied users, paraplegic patients require support simply to stand. But the latest hard exoskeletons are also making headway. For these users, a 100 kilometre route march isn’t the target, a simple stroll to the local shops would be life-changing. At the current price it could be a while before exoskeletons become a common sight on our footpaths, given that motorised wheelchairs are available for a few thousand dollars, around one fiftieth the price of a ReWalk. Costs need to come down, and more evidence shown for their effectiveness, says Andrew McDaid, a biomedical engineer at the University of Auckland. “Then there will be a huge rush in adoption of this technology.”

Supersuits for heavy industry

Strap on a Dual Arm Power Amplification Robot, made by a Panasonic subsidiary, and you’ll soon be lifting 100kg loads without breaking a sweat. Other exosuits for industrial tasks are being developed by Hyundai in South Korea, and Cyberdyne in Japan. But none have seen widespread adoption as yet. It might not have the cool factor of an exoskeleton, but we already have human enhancement devices for hoisting heavy loads – the tried and tested forklift. In the end, the uptake of a technology comes down to economics, says McDaid. “What value does the exoskeleton add? And does that value exceed the cost of the device?” Not yet, it seems.

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Cathal O'Connell is a science writer based in Melbourne.
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