A proof-of-concept study suggests the community-use ankle exosuit could help stroke survivors improve their walking propulsion and boost their overall walking confidence and ability while ambulating around their own homes, workplaces, and neighborhoods. The work, led by Conor Walsh’s team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), is published online in Annals of the New York Academy of Sciences.
Recent studies have proven that post-stroke study participants can improve their walking speed, distance, propulsion, and gait symmetry with the help of an assistive robotic exosuit, but those studies have all occurred in labs or clinical settings.
“We saw an opportunity to leverage wearable technology to rethink how we approach physical therapy and rehabilitation” says Walsh, senior author on the paper and the Paul A. Maeder Professor of Engineering and Applied Sciences at SEAS. “If we can shift some of these clinical services from the clinic to the home and community, we can improve access, reduce costs and deliver better care. It is exciting to see the fields of engineering and physical therapy come together to make this happen.”
For over a decade, Walsh’s Biodesign Lab at Harvard has been developing assistive and rehabilitative exosuit technologies for various applications. Some of that technology has already been licensed and commercialized by ReWalk Robotics and been given breakthrough status by the U.S. Food and Drug Administration. To design an ankle exosuit meant for use in the community, Walsh’s team need to simplify the exosuit’s mechanical components and make it easy for wearers to control.
“In the past, our ankle exosuits had two active actuators – one that helped with dorsiflexion to keep the wearer’s toes up, and another to help with plantarflexion, propelling the foot and body away from the ground,” says Richard Nuckols, a former postdoctoral fellow in Walsh’s lab at SEAS, and co-first author of the paper.
Instead of an active dorsiflexion actuator, the new exosuit contains a passive material that flexes and performs like a spring, helping the toes stay up during the foot’s swing phase and preventing the wearer from catching their toes on the ground. “By replacing an active actuator with a passive actuator, the exosuit is inherently safer; in the case of an unexpected power loss or controller failure, the default state will keep the users toes up and reduce risk of a trip and fall,” Nuckols says.
“We also developed a mobile app to enable wearers to easily interact with the device and remotely check in with our team,” says Chih-Kang Chang, a Ph.D. candidate in Walsh’s lab and a co-first author on the paper. “The app allows wearers to turn the device on themselves and tell the exosuit when they want to start walking.”
In addition, the team incorporated sensors to allow for remote monitoring of the wearer’s progress over time. “We are collecting data while people are walking in the exosuit, and measuring how they improve their gait over time,” Chang says. “Going forward, this information could be a really powerful aspect of using this exosuit for long-term rehabilitation in partnership with a physical therapist.”
“These sensors – located on the foot, shank, and pelvis – are converted using a machine-learning algorithm into estimates of propulsion, helping us understand how well people are generating proper ankle mechanics and how effectively they are walking,” Nuckols says.
“Collecting the amount of data needed to train a typical machine learning model from individual wearers is extremely challenging, given the limited ability to walk for extended periods of time post-stroke,” says Daekyum Kim, a postdoctoral fellow in Walsh’s lab, and co-first author of the paper. “The key advantage of our approach is that it leverages walking data gathered from multiple individuals to better tune a machine learning model to each user.”
MEDICA-tradefair.com; Source: Harvard School of Engineering and Applied Sciences
