A Low-Profile Passive Ankle Exoskeleton System Capable of Enhancing Human Walking

Abstract

Walking is an important skill that we perform in our lives. Engineers and researchers have attempted to enhance this skill by building exoskeletons that work alongside our bodies. These exoskeletons usually fall into one of these three categories: Active, passive, and quasi-passive. This project involves designing a purely passive ankle exoskeleton that reduces the metabolic cost of human locomotion. Unlike powered exoskeletons, designing a passive exoskeleton is challenging due to fact that no external power source is applied. A research gap exists in passive exoskeleton timing mechanisms, this could be due to the fact that passive exoskeletons only work on a constant speed and the designs are not practical to be worn in normal day activities. The design in this project will approximately weigh 350g and will be using a linear spring that functions in parallel with the calf muscle and Achilles tendon to store and release the energy that has been accumulated by the user. A clutch will be placed under the forefoot and will be used to time the system by locking during flat foot event in gait cycle and unlocking during toe off to control the assisting spring. The clutch is designed to adapt to the walking speed by using the weight of the body to lock the clutch, therefore, when the speed of the user increases the gait timing will accordingly adjust. Kinematic and structural analyses was performed on this clutch design to ensure its functionality and reliability; this was done using SolidWorks and Abaqus software packages.