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Everyone walks differently — so this exoskeleton adjusts on the fly

Everyone walks differently — so this exoskeleton adjusts on the fly


A boot-like, robotic exoskeleton helped people walk faster while using less energy

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An image of someone’s legs from the knee down with a robotic exoskeleton attached at the feet and below the knee. The exoskeleton is exposed, colorful wires and circuit boards.
A close-up view of a portable ankle exoskeleton that helps someone walk
Image: Stanford University

A new robotic, boot-like exoskeleton uses wearable sensors to adjust to each person who wears it, marking a significant step forward for robotics. The device, described in a study published today, helps solve one of the big challenges in developing systems that help people walk: that everyone walks differently.

“This exoskeleton personalizes assistance as people walk normally through the real world,” said Steve Collins, associate professor of mechanical engineering and head of the Stanford Biomechatronics Laboratory.

Exoskeletons as a concept aren’t new — researchers think they could help people with mobility issues or remove some of the strain from walking for people in jobs that require constant movement. But so far, devices that work in the lab haven’t translated as well to real-world settings. They’re often unwieldy and hard to use, and the process of personalizing them to each new person is expensive and difficult.

The team at the Stanford Biomechatronics Laboratory tried to address those problems. First, the device is self-contained. It straps to the wearer’s ankle and up the lower leg and is controlled by a battery pack at the waist, so people are able to move freely outside and through the normal daily environment. Right now, the prototype is a tangle of wires that attaches to a shoe and below the knee. The device nudges the calf muscle at each step, applying force that gives the user a boost.

The team also developed a new method to simplify the process of adjusting the exoskeleton to each person. Normally, exoskeletons are fitted by having people walk on a treadmill in a lab while things like their oxygen consumption and energy expenditures are closely monitored. That way, the device can be tweaked until it’s firing at just the right moment to help to reduce the amount of energy used by an individual person.

The new approach, published Wednesday in the journal Nature, leaned on data collected in a previous experiment that tracked people walking with an exoskeleton in the lab under hundreds of different conditions. They used that data to build a model that could figure out the energy people used to walk based on information from cheap sensors embedded in the exoskeleton.

That model lets the exoskeleton learn in real time and in real-world conditions how best to help someone walk. The study tested the system on 10 people and found that it was able to optimize movements in around an hour. During that process, they walked around outside while hearing various prompts — like “walk as if you were walking to catch a bus” — so that the device could adjust to the walking speeds used in day-to-day situations.

After it was optimized, the exoskeleton let the participants move faster while using less energy than they would have wearing normal shoes. In real-world tests where participants walked outside, it was the equivalent of taking off a 20-pound backpack, the study found.

This study only tested the exoskeleton on healthy adults in their mid-20s, so there’s still a long way to go to confirm if it can help people who need additional assistance, like older adults who walk slowly or people who work in physically demanding jobs like warehouse workers. And the device is a prototype — there’s still a long way to go before it’d be available. It’s not clear how much an exoskeleton like this might cost as a medical or consumer product. Still, showing that an exoskeleton can improve movement in a real-world environment is a first for robotics, the research team said.

“I believe that over the next decade we’ll see these ideas of personalizing assistance and effective portable exoskeletons help many people overcome mobility challenges or maintain their ability to live active, independent, and meaningful lives,” study author and bioengineering researcher Patrick Slade said in a statement.