Rehabilitation patients could walk or run using the same therapeutic exoskeleton, thanks to design advancements and a sophisticated algorithm that detects the patient’s gait.
Researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) and the University of Nebraska Omaha have developed the lightweight exosuit made of textile components worn at the waist and thighs and a mobile actuation system attached to the lower back.
“Our study demonstrates that it’s possible to have a portable wearable robot assist more than just a single activity, helping to pave the way for these systems to become ubiquitous in our lives,” says Conor Walsh, Ph.D., who led the study.
The hip exosuit was developed as part of the Defense Advanced Research Projects Agency (DARPA)’s former Warrior Web program and is the culmination of years of the team’s research and optimization of the soft exosuit technology.
The team’s most recent hip-assisting exosuit is simpler and lighter, and assists the wearer via a cable actuation system. The actuation cables apply a tensile force between the waist belt and thigh wraps to generate an external extension torque at the hip joint that works in concert with the gluteal muscles. The device weighs 5kg with more than 90% of its weight located close to the body’s center of mass.
A major challenge facing the team was that the exosuit needed to distinguish between walking and running gaits and change its actuation profiles accordingly to provide the right amount of assistance at the right time in the gait cycle.
Biomechanists often compare walking to the motions of an inverted pendulum and running to the motions of a spring-mass system. When walking, the body’s center of mass moves upward after heel-strike, then reaches maximum height at the middle of the stance phase to descend toward the end of the stance phase. While running, the movement of the center of mass is opposite. It descends toward a minimum height at the middle of the stance phase and then moves upward toward push-off.
In ongoing work, the team is focused on optimizing all aspects of the technology, including further reducing weight, individualizing assistance, and improving ease of use.
Harvard Wyss Institute for Biologically Inspired Engineering
John A. Paulson School of Engineering and Applied Sciences (SEAS)
University of Nebraska Omaha