Passive exoskeleton to lighten the load for soldiers

The Australian military's weight-diverting prototype exoskeleton(Credit: Defence Science and Technology Group)

Imagine if you were to carry over 100 lb (45 kg) of gear in a backpack, for several hours at a time. Well, that’s just what some soldiers have to do, and it can cause great stress to their torso and legs. That’s why engineers at the Australia’s Department of Defence have developed a new exoskeleton, that diverts two thirds of pack weight directly to the ground.

While we’ve heard about load-lightening exoskeletons before, they’ve tended to be complex, electrically-powered contraptions that require microprocessors and heavy batteries. By contrast, the Australian model is inexpensive to build, weighs under 3 kg (6.6 lb) and utilizes two simple Bowden cables (steel cables that slide within a separate housing). These run from a rigid-frame backpack along either side of the wearer, via leg braces to the base of the boots.

"Bowden cables are typically used to transfer a pulling force (e.g. clutch on a motorbike)," a representative from the Department of Defence tells us. "However, the outer covering of these cables prevents them from buckling, thus enabling them to also transfer a push force (e.g. steering controls for a boat). It is this property that is used in our exoskeleton to transfer force from the mass of the backpack to the ground."

Additionally, because the cables are flexible, they’re able to bend with the wearer and thus don’t impede their range of motion. What’s more, when they’re not needed, they can simply be detached and carried in the backpack.

While the exoskeleton is still in the proof-of-concept phase, early test results have reportedly proved promising. It is hoped that once it’s developed, the technology could be used not only for the military, but also civilian applications such as firefighting and hiking.

"The person provides the strength, control and balance to raise and move the load whilst the very light exoskeleton transfers much of the burden of keeping a load off the ground away from the shoulders, spine and legs of the wearer," says the DoD. "The wearer needs to continue to bear a proportion of the load so that they can judge changes to their loaded centre-of-mass and maintain dynamic balance when walking."

Scientists at Carnegie Mellon and North Carolina State universities are working on a somewhat similar system, designed to improve walking efficiency.

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