Posts Tagged ankle exoskeleton
- A powered ankle exoskeleton with only 348 g of added distal mass.
- The exoskeleton reduced the activity of the gastrocnemius muscle by 44%.%
- The exoskeleton reduced the activity of the soleus muscle by 37%.%
Most of powered ankle exoskeletons add considerable distal mass to the user which limit their capacity in reducing the metabolic energy of walking. The objective of the work presented in this paper is to develop an ankle exoskeleton with a minimum added distal mass compared to existing autonomous powered ankle exoskeletons while it can provide at least 30 Nm of assistive plantarflexion torque. The proposed exoskeleton uses Bowden cables to transmit the mechanical force from the actuation unit attached to the waist to the carbon fiber struts fixed on the boot. As the struts are pulled, they create an assistive ankle plantarflexion torque. A 3d-printed brace was attached to the shin to adjust the direction of the cables. A design optimization study was performed to minimize the mass of the struts, thereby limiting the total added distal mass, attached to the shin and foot, to only 348 g. The main result obtained from walking tests was the reduction of the soleus and gastrocnemius muscles activity by a maximum of 37% and 44% respectively when walking with the exoskeleton compared to normal walking. This result shows the potential of the proposed exoskeleton to reduce the metabolic cost of walking and emphasizes the importance of minimizing the distal mass of ankle exoskeletons. Tests with more subjects will be carried in the future to confirm this result.
Mechanical engineers at Vanderbilt University have developed a lightweight, low-profile ankle exoskeleton that they suggest could be worn under clothes without restricting motion, and does not require additional components such as batteries or actuators carried on the back or waist.
It could be widely used among elderly people, those with impaired lower-leg muscle strength, and workers whose jobs require substantial walking or running, they note, in a study published recently in IEEE Transactions on Neural Systems & Rehabilitation Engineering.
The study builds on a successful and widely cited ankle exoskeleton concept from other researchers in 2015, according to a media release from Vanderbilt University.
“We’ve shown how an unpowered ankle exoskeleton could be redesigned to fit under clothing and inside/under shoes so it more seamlessly integrates into daily life,” says Matt Yandell, a mechanical engineering PhD student and lead author of the study, in the release.
The team invented an unpowered friction clutch mechanism that fits under the foot or shoe and is no thicker than a typical shoe insole. The complete device, which includes a soft shank sleeve and assistive spring, weighs just over 1 pound.
“Our design is lightweight, low profile, quiet, uses no motor or batteries, it is low cost to manufacture, and naturally adapts to different walking speeds to assist the ankle muscles,” states Karl Zelik, assistant professor of mechanical engineering and senior author on the study.
“It could also help reduce fatigue in occupations that involve lots of walking, such as postal and warehouse workers, and soldiers in the field,” he adds.
[Source(s): Vanderbilt University, Science Daily]