Personalized Exoskeletons Are Making Strides Toward a Man-Machine Interface

By designing adaptable machines that learn on the fly, researchers hope to create exoskeleton systems that will help us move faster and farther.

Proponents of the technological singularity theory insist that it's only a matter of time before mankind finally merges with machines, creating a new order of being on planet Earth. While much of this discussion focuses on artificial intelligence, our cyborg future will surely include a physical component as well.

For those of us who are prone to this sort of speculation, that's where the powered exoskeleton comes in. No longer a science fiction concept, exoskeletons are steadily moving out of the research labs and into the real world. Medical and military applications are already well established, and recent workplace systems are being deployed to help laborers manage heavy loads and repetitive stress.

Now comes word that researchers are developing a new kind of personalized exoskeleton system that customizes itself on the fly. Designed to react and adapt to each individual wearer, the system can significantly reduce energy expenditure on everyday activities such as walking, effectively improving human stamina like a fast-forward evolution button.

At the moment, the new system has just a single module, an ankle unit that gradually changes its pattern of assistance as a person walks. By actively monitoring the wearer's overall energy expenditure, the ankle unit can make small adjustments in torque that optimize efficiency of standard locomotion.

Those little tweaks add up. According to a new research paper that was just published in the journal Science, test subjects wearing the unit experienced a 24 percent reduction in energy expenditure while walking.

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“One thing to note is just how large the reductions in metabolic cost were in this study,” co-author Rachel Jackson, research associate in mechanical engineering at Carnegie Mellon University, told Seeker. “The reductions we observed were huge — 24 percent, which is the largest to date — and this was using just an ankle exoskeleton worn on one leg.”

To assist the subjects in the study, the researchers used an ankle emulator that employs electromechanical springs and cables that interact with the foot and shank — a generic term for the part of the leg between the knee and ankle. The emulator essentially acts as an exterior ankle, taking weight and stress off of the actual ankle.

To monitor energy expenditure, test subjects wore a respiration mask that measured oxygen and carbon dioxide levels.

“Knowing these measurements and how gas is exchanged in the body, we can estimate the metabolic rate of an individual in watts per unit body mass,” Jackson said.

The experiments showed that the exoskeleton assistance reaches its peak optimization after about an hour, with some volunteers reducing energy expenditure more than 30 percent. With each step, the mechanical unit and the test subject basically respond and adapt to one another.

“Throughout the optimization, the user’s performance is measured and the device adjusts its behavior accordingly,” Jackson said. “Therefore, the device is learning what is optimal for the user, as the user learns how to best walk with assistance.”

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With the ankle emulator showing such promising results, one wonders whether this exoskeleton system could be modified to work with other parts of the human body. Jackson thinks it can.

“Our lab is currently developing a full lower-limb exoskeleton that assists at the ankle, knee, and hip joints,” she said. “We’re planning on using the same approach to discover an optimal assistance strategy for this multi-joint exoskeleton.”

To be clear, the research team isn’t aiming to improve the human species in a kind of comic book, superhero kind of way. The goals are short-term and practical.

“We expect such devices to enhance performance in able-bodied individuals, to walk or run faster or farther, and to aid in load carriage for soldiers,” Jackson said. “We also think such devices will be able to assist those with gait impairments, such as amputees, post-stroke individuals, and those with other neurological injuries.”

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