The actuating cables assist with the ankle motion at the back of the lower legs, and additional straps transfer energy produced at the ankle to the front of the hip to also assist with the hip motion during gait.
Photograph courtesy of the Wyss Institute at Harvard.
Last year, a team of researchers at Harvard University’s Wyss Institute for Biologically Inspired Engineering provided first proof-of-concept results showing that its wearable soft exosuit could lower energy expenditure in healthy people walking with a load on their backs. Made of functional textiles, cable-based actuation, and a biologically-inspired control system, the exosuit targets specific leg joints instead of the full leg- and delivers assistance that is synchronized with the wearer’s walking mechanics. It can help individuals who carry heavy loads to people who have gait deviations due to stoke or other health complications. Now, in a new study, published in Science Robotics, the multidisciplinary team of roboticists, engineers, biomechanics experts, and apparel designers have isolated the beneficial effects of the exosuit.
The team is led by Conor Walsh, PhD, a Wyss Institute core faculty member, the John L. Loeb Associate Professor of Engineering and Applied Sciences at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and the founder of the Harvard Biodesign Lab. By removing the actuation, electronics, and battery units, leaving only the exosuit’s light, wearable textiles and pulling cables, Conor and his colleagues were able to calculate the impact on the wearers’ joints.
“In a test group of seven healthy wearers, we clearly saw that the more assistance provided to the ankle joints, the more energy the wearers could save, with a maximum reduction of almost 23 percent compared to walking with the exosuit powered off,” said Walsh. “To our knowledge, this is the highest relative reduction in energy expenditure observed to date with a tethered exoskeleton or exosuit.”
The team found that wearers significantly adapted their gait with increasing levels of assistance. The changes were most significant at the ankle joint but also at the hip, as the exosuit included straps coupling the assistance from the back of the lower legs to the front of the hip in a beneficial manner.
“Other studies had reported that there can be an energy transfer between the ankle and other joints. However, by having a textile couple the ankle and hip with our soft exosuit, may have amplified this effect, contributing to the considerable energy savings we found,” said Brendan Quinlivan, a graduate student working with Walsh and one of the two first-authors on the study.
The authors acknowledge that future studies are now required to compare the effects of fully body-worn versions of the exosuit, with the weight of the actuation and battery carried by the wearer, to walking with normal clothes to better quantify the true impact of the technology.
“This study represents another major step forward along a path that will bring this new type of wearable robot into the marketplace where it will help soldiers and workers, as well as patients with disabilities,” said Wyss Institute Founding Director Donald Ingber, MD, PhD, who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School, and professor of bioengineering at Harvard SEAS.
Editor’s note: This story was adapted from materials provided by the Wyss Institute at Harvard.
