Between walking at a leisurely pace and running for your life, human gaits can cover a wide range of speeds. Typically, we choose the gait that allows us to consume the least amount of energy at a given speed. For example, at low speeds, the metabolic rate of walking is lower than that of running in a slow jog; vice versa at high speeds, the metabolic rate of running is lower than that of speed walking.
Researchers in academic and industry labs have previously developed robotic devices for rehabilitation and other areas of life that can either assist walking or running, but no untethered portable device could efficiently do both.
The light-weight versatile exosuit assists hip extension during uphill walking, and at different running speeds in natural terrain.
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Assisting walking and running with a single device is challenging because of the fundamentally different biomechanics of the two gaits. However, both gaits have in common an extension of the hip joint, which starts around the time when the foot comes in contact with the ground and requires considerable energy for propelling the body forward.
As reported today in Science, a team of 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 now has developed a portable exosuit that assists with gait-specific hip extension during both walking and running. Their lightweight exosuit is made of textile components worn at the waist and thighs, and a mobile actuation system attached to the lower back which is controlled by an algorithm that can robustly detect the transition from walking to running and vice versa.
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 research and optimization of the soft exosuit technology by the team. A previous multi-joint exosuit developed by the team could assist both the hip and ankle during walking, and a medical version of the exosuit aimed at improving gait rehabilitation for stroke survivors is now commercially available in the US and Europe, via a collaboration with ReWalk Robotics.
The hip-assisting exosuit is designed to be simple and light weight. 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 in total with more than 90 percent of its weight located close to the body's center of mass. "This approach to concentrating the weight, combined with the flexible apparel interface minimizes the energetic burden and movement restriction to the wearer," said co-first-author Jinsoo Kim, a SEAS graduate student in Walsh's group. "This is important for walking, but even more so for running as the limbs move back and forth much faster."
A major challenge the team had to solve was that the exosuit needed to be able to distinguish between walking and running gaits and change its actuation profiles accordingly with the right amount of assistance provided at the right time of the gait cycle.
"We developed our biologically inspired gait classification algorithm that can robustly and reliably detect a transition from one gait to the other by monitoring the acceleration of an individual's center of mass with sensors that are attached to the body," said co-corresponding author Philippe Malcolm, Ph.D., Assistant Professor at University of Nebraska Omaha. "Once a gait transition is detected, the exosuit automatically adjusts the timing of its actuation profile to assist the other gait, as we demonstrated by its ability to reduce metabolic oxygen consumption in wearers."
"This breakthrough study coming out of the Wyss Institute's Bioinspired Soft Robotics platform gives us a glimpse into a future where wearable robotic devices can improve the lives of the healthy, as well as serve those with injuries or in need of rehabilitation," said Wyss Institute Founding Director Donald Ingber.
MEDICA-tradefair.com; Source: Wyss Institute for Biologically Inspired Engineering at Harvard