Purely Mechanical Exoskeleton On Legs: Walking Easy To The Future


Finding it hard to walk due to an injury — or just aging legs?

Scientists have invented an unpowered and wearable "exoskeleton" that helps you walk efficiently and reduces by 7 percent the energy required for each step — that's like taking nine pounds off your body.

This low-cost mechanical device works without any computers or batteries and, according to its inventors, the exoskeleton can boost the performance of calf muscles and the Achilles tendon, absorbing small amounts of energy when the foot hits the ground and releasing it again when the foot lifts off the ground.

The exoskeleton is attached to the lower leg and foot and is hinged at the ankle. A clutch and spring act in parallel with the calf muscles and Achilles tendon. The clutch mechanism functions with a ratchet and pawl, which mechanically engage the spring when the foot is on the ground and disengage it when the foot is in the air.

Gregory Sawicki, a biomechanical engineer at North Carolina State University and co-author of the study, said the unpowered exoskeleton works "like a catapult" to reduce the load placed on the calf muscles and Achilles tendons.

Steven Collins, a mechanical engineer at Carnegie Mellon University and author of the paper, said the inexpensive, lightweight device could have important uses for people who find it difficult to walk for long periods after illness, and might one day help long-distance walkers and runners.

"Previous research led to the development of powered devices to improve walking efficiency but these are expensive and involve complicated motors and battery packs," Collins explained. "This device is lightweight and simple, with no batteries or motor. Instead of costing between $40,000 and $80,000, it could cost just a few hundred dollars."

"Someday soon, we may have simple, lightweight and relatively inexpensive exoskeletons to help us get around, especially if we've been slowed down by injury or aging," he added.

Collins is researching ways to put the leg boosters to practical use, initially for people whose disabilities make routine walking difficult. But it's clear the invention could serve other purposes as well. Asked if he was talking to the military, Collins paused before answering, "I'm not sure if I'm supposed to say... Those conversations are ongoing, I guess."

At present, the invention has only passed tests on a treadmill at 2.8 mph. To make it work for running in the "real world," Collins concedes he would have to go electric, using a tiny processor that could adjust to how fast a person is moving.

The advancements in exoskeletons could make mountain hiking, military marching or even mall strolling an ageless task for everyone in the not-so-distant future.

This study was published in the journal Nature.

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