Soft Exosuit Can Automatically Adapt to Walking Needs
Our gait is constantly changing. We change our speed and adjust to slopes without even thinking about it. Because of this variability, it is hard to replicate walking with exoskeletons. However, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed an approach that automatically adjusts a soft exoskeleton based on how a person walks.
Typically, tuning exoskeletons to a person's gait requires several hours of manual or automatic adjustment. This process can be difficult for a healthy person, and sometimes nearly impossible for older adults or clinical patients.
SEAS researchers take a unique approach to designing their exoskeleton. Instead of focusing on the dynamic movements of the user's limbs, they created a muscle-based assistance strategy.
"We recorded the dynamics of people's soleus muscles using ultrasound at various walking speeds and inclines. Based on these pre-recorded images, we estimated the force generated by the soleus muscle through inefficient concentric contraction, and developed an exosuit assistance profile proportional to this estimated force. We evaluated this approach using a bilateral ankle exosuit during each measured walking task," the researchers said.
Using this strategy, a portable ultrasound system performs ultrasound measurements of the calf muscles. These measurements make it possible to estimate the force generated by these muscles. Using the measurements, the researchers develop an individualized assistance profile. The exosuit then automatically prescribes the amount of assistance needed for different walking speeds and inclines. The exosuit provides less assistive force to help someone walk.
“We used ultrasound to look beneath the skin and directly measured what the user's muscles do during several walking tasks. Our muscles and tendons are compliant, which means there is not necessarily a direct correspondence between limb movement and the movement of the underlying muscles that control it”
What sets this method apart from previous ones is the exoskeleton's ability to automatically determine the assistance a person needs when walking at different speeds and inclines. The exosuit needs only a few seconds of walking to capture the muscle profile.
According to the researchers, this exosuit can quickly adapt to real-world conditions. When the scientists measured the metabolic energy used with and without the suit, they found that the suit significantly reduces the amount of metabolic energy used.
SEAS graduate student and co-author Sangjun Lee said: "By measuring muscles directly, we can work more intuitively with the person using the exosuit. With this approach, the exosuit does not overpower its wearer, but works together with them."
This research is the result of collaboration between the Harvard Biorobotics Lab and the Harvard Biodesign Lab, led by Conor J. Walsh, professor of engineering and applied sciences at SEAS. SEAS researchers plan to move forward by testing how the system works with continuous real-time adjustments.
"Variation in human gait depends on individual physiology, the environment and the walking task. Therefore, in the field of wearable robotics there is a clear need to tailor assistance to the user and the task. Here we developed a muscle-based assistance strategy in which exosuit assistance was derived from direct measurements of human muscle dynamics during specific tasks," the study says.
In real-world testing, the exosuit was able to quickly adapt to changes in walking speed and incline.
“This approach could help advance wearable robots in real dynamic situations, providing comfortable, tailored assistance”
The Harvard John A. Paulson School of Engineering and Applied Sciences serves as the hub and integrator of Harvard's teaching and research in engineering, applied sciences and technology. Through collaboration with researchers across Harvard, other universities, and corporate and foundation partners, scientists make discoveries and innovations directly to improve people's lives and society.
The Wyss Institute for Biologically Inspired Engineering at Harvard University uses nature's design principles to develop biochemistry-based materials and devices that will transform medicine and create a more sustainable world.
Wyss researchers develop new innovative engineering solutions for healthcare, energy, architecture, robotics and manufacturing, which are translated into commercial products and treatments through collaboration with clinical researchers, corporate alliances and the creation of new startups.
The Institute creates revolutionary technological breakthroughs by engaging in high-risk research and overcoming disciplinary and institutional barriers, working as an alliance that includes Harvard's schools of medicine, engineering, arts and sciences, and design, as well as in partnership with many medical institutions and other universities.
