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Case Study: Powered Hip Exoskeleton Reduces Metabolic Cost of Walking in Individual with Hemiparesis

Year: 2023

Presenter Name: Kai Pruyn

Every year about 795,000 Americans suffer a stroke. Though the mortality rate has decreased, stroke commonly results in physical disability due to hemiparesis, muscle weakness in one side of the body. Hemiparesis causes stroke survivors to struggle with mobility as it results in poor balance, reduced range of motion, and early onset of fatigue. Powered exoskeletons have been proposed as a potential solution to this problem. Powered exoskeletons are wearable devices that support the movements of the user by providing assistance from electric motors. Exoskeletons have been successful in assisting healthy subjects who have a consistent and symmetric gait. However, the ability of a powered exoskeleton to assist the wearer depends on the capability of the exoskeleton controller to synchronize with the biological movements of the user. Hemiparetic subjects have asymmetric gait patterns that make it challenging for the exoskeleton controller to synchronize with the user. Therefore, developing assistive controllers based on the hemiparetic gait is necessary for powered exoskeletons to effectively assist stroke subjects. The goal of my undergraduate research is to address the problem of human-robot coordination in the context of assistive powered exoskeletons for individuals with hemiparesis. To this end, I have developed a controller that provides flexion and extension assistance to one or both of the user's hip joints. The assistive torque profile and timing is adjusted based on each subject's gait cycle and where they need the most support. The controller tracks the wearer's previous steps to predict their next ones, providing consistent and reliable exoskeleton assistance. Each side can be controlled independently to deliver different amounts of assistance with different timing to a subject's hemiparetic side and unaffected side. To preliminarily verify the viability of this assistive control approach, I conducted a case study with one individual with hemiparesis walking with and without a powered hip exoskeleton while we measured metabolic cost. The participant walked on a treadmill at 0.9 ms-1 for a series of 6-minute-walk-tests (6MWT): one without the exoskeleton and three with the exoskeleton. The exoskeleton provided bilateral flexion and extension assistive torque to both hip joints. Our results show that the powered hip exoskeleton reduced the metabolic cost of walking by 34%. This reduction is equivalent to removing a 58-lbs backpack for a healthy individual. The results of this study will inform future metabolic and clinical study designs, focusing on assisting stroke survivor ambulation with the powered hip exoskeleton.
University / Institution: University of Utah
Type: Oral
Format: In Person
SESSION C (1:45-3:15PM)
Area of Research: Engineering
Faculty Mentor: Tommaso Lenzi
Location: Union Building, DEN (2:45pm)