Boxtel is wearing a new exoskeleton called eLEGS, which could soon help people with spinal injuries to walk with a natural gait. "Walking with eLEGs took some rewiring and relearning," says Boxtel, "but my body has the muscle memory. And I learned to walk really fast."

eLEGS is being readied for clinical trials by Berkeley Bionics, based in Berkeley, California. Unlike other exoskeletons, such as Raytheon's XOS-2, and Berkeley Bionics's HULC, eLEGS is not intended to augment soldiers with super-human strength, but is specifically designed as a rehabilitation device to help restore walking function to people with spinal cord injuries, as well as improving blood circulation and digestion.

Tether me not

The suit consists of a backpack-mounted controller connected to robotic legs. It is driven by four motors, one for each hip and knee. The ankle joint is controlled with passive springs that keep the foot angled so that it can be placed on the ground, heel to toe, as the leg steps. Sensors in the legs relay position information to the control unit, which determines how to bend the joints and, in turn, walk. Onboard lithium-cobalt batteries allow the suit to be operated without a tether to a power source.

While the device can support a wearer's weight, balance is left up to the person, via crutches, which also serve to control the system. To take a step, the wearer pushes down with the crutch opposite to the intended stepping leg. Similar gestures, such as pushing down on both crutches simultaneously, allow the wearer to transition from sitting to standing, or to make turns.

Berkeley Bionics claims eLEGS has the largest range of knee flexion of any exoskeleton, a feature they say offers a more natural gait than other exoskeletons.

Strut their stuff

eLEGS is not the only robotic exoskeleton aimed at restoring walking in paraplegics. ReWalk from Argo Medical Technologies in Haifa, Israel, uses a similar design, with a backpack connected to struts and electric motors that attach to the outside of a person's legs. It is currently being used in clinical trials in the US. AMT claims it will have the suit through the FDA approval process and on the market in 12 to 18 months.

Grant Elliot, an exoskeleton researcher at the Massachusetts Institute of Technology's Media Lab, says rehabilitation devices like eLEGS and ReWalk are promising. Still, he says that attention needs to be paid to such devices to ensure they remain compact enough for their users to move freely without bumping into objects. "Humans are used to moving through human-sized spaces, like narrow hallways," says Elliot.

In a demonstration for New Scientist last week, eLEGS wearers including Boxtel were able to negotiate tight spaces, such as walking between a table and a bin, without difficulty.

John Fogelin, director of engineering at Berkeley Bionics, says the company is working on ways to make the design sleeker by using smaller batteries and thinner struts, aiming for a day when it might be worn underneath one's clothes. The company plans to begin clinical trials in early 2011, and estimates the cost on the market to be in line with that of a high-end wheelchair, around $100,00

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www.newscientist.com/article/dn19555-exoskeleton-helps-the-paralysed-walk-again.html

Oct. 7, 2010