Assessing Design Trade-Offs in an Orthosis with Enhanced Functionality and Customizability

PROJECT SUMMARY
Ankle-foot orthoses (AFOs) commonly prescribed for balance disorders, weakness, and neurological deficits
have limited functionality due to their static nature. They restrict the joint’s range of motion and hamper energy
transfer, despite their success in mitigating foot drop. Foot drop is a condition that increases the risk of gait
abnormalities and falls. To address the limitations of AFOs, this project seeks to improve the upon a Variable
Stiffness Orthosis (VSO) design by incorporating a unique cam-based transmission that allows for decoupled
energy storage and return. The Decoupled Energy Storage and Return Variable Stiffness Orthosis (DESR-VSO)
transmission has two cams which can be engaged during different phases of walking to provide both variable
stiffness and energy recycling. Energy recycling is the phenomenon where energy is captured upon heel strike
and returned during the push-off phase of gait. This proposal includes designing multiple versions of the cam-
based transmission to optimize the balance between foot drop prevention (dorsiflexion assistance) and energy
recycling. The transmission designs will be tested on the bench top and evaluated on patients with foot drop
from peroneal nerve damage. The testing and evaluation stage will guide the selection of the most promising
transmission design for a future clinical trial. This project aligns with the Neurobionics Lab’s goal to enhance
mobility for individuals with disabilities through device design and evaluation. Led by candidate Emily Bywater
and Prof. Elliott Rouse at the University of Michigan, the research will benefit from the expertise of additional
assistive device specialists and clinical advisors who have volunteered to collaborate. The outcomes will offer
insights into the impact of design decisions on energy recycling and foot drop mechanics, facilitating the selection
of an optimal cam-based transmission. Feedback from clinicians and patients will contribute to future design
improvements, while subsequent clinical trials will assess the effects of dorsiflexion assistance on patient gait
and explore metrics for assessing how the device can be individualized. Emily’s training plan includes training in
design, control theory, software engineering, biomechanics, professional development, diversity, equity, and
inclusion, and scientific communication. The project will be conducted in the state-of-the-art Rehabilitation Lab
in the Ford Motor Company Robotics Building at the University of Michigan, where all of the necessary equipment
for human subject studies, benchtop testing, and device fabrication is already established.

Grant Number: 5F31HD115309-02
NIH Institute/Center: NIH
Principal Investigator: Emily Bywater