Biomechanical Knee Joint for Exoskeleton

Author(s) Information

Gabriel Ireton Ahern, California Polytechnic State University, San Luis ObispoFollow
Calloway Miller, California Polytechnic State University, San Luis ObispoFollow
Christianna Altamura, California Polytechnic State University, San Luis ObispoFollow
Eric Mailes, California Polytechnic State University, San Luis ObispoFollow

College - Author 1

College of Engineering

Department - Author 1

Mechanical Engineering Department

Degree Name - Author 1

BS in Mechanical Engineering

College - Author 2

College of Engineering

Department - Author 2

Mechanical Engineering Department

Degree - Author 2

BS in Mechanical Engineering

College - Author 3

College of Engineering

Department - Author 3

Biomedical Engineering Department

Degree - Author 3

BS in Biomedical Engineering

College - Author 4

College of Engineering

Department - Author 4

Mechanical Engineering Department

Degree - Author 4

BS in Mechanical Engineering

Date

6-2023

Primary Advisor

Peter Schuster, College of Engineering, Mechanical Engineering Department

Abstract/Summary

Our senior design project consisted of designing and manufacturing a biomechanically accurate, actuated knee joint to be integrated into an exoskeleton being developed by the Lower Limb Exoskeleton Assist Project (LLEAP), a part of the EMPOWER student association at Cal Poly, San Luis Obispo. As the human knee flexes and extends throughout gait motion, the center of rotation changes. Currently marketed exoskeletons have one point of rotation, which over constrains the knee and causes misalignment between the user and the suit [1]. Our goal was to mimic natural knee joint motion by changing the center or rotation, thus reducing misalignment and limiting power loss. We designed this knee joint for our prospective exoskeleton user: Carlo Ruggiero, a 21-year-old Cal Poly student with a complete C8 injury to his spine which resulted in loss of function and sensation from his chest and below.

Our design consists of a linear actuator mounted along the outside of the user’s thigh, which drives a four-bar linkage in line with the user’s knee. After manufacturing and testing our design, it was found that the joint met the necessary power requirements and reached the required angles for human gait. However, the linear actuator that was purchased was too long to fit properly on the user’s leg and is unable to vary its speed.

This verification prototype proves that mimicking knee joint motion for exoskeleton applications is feasible but requires integration of a linear actuator with greater power density and the ability for speed control. We also recommend using biomedical imaging to accurately determine the center of rotation throughout actuation. This would allow for tuning of the lengths of the links in the four-bar linkage to match the user’s knee biomechanics more precisely.

URL: https://digitalcommons.calpoly.edu/mesp/703