Influence of Motion Restrictions in an Ankle Exoskeleton on Gait Kinematics and Stability in Straight Walking

TL;DR

This study examines how varying the degrees of freedom in an ankle exoskeleton influence gait kinematics and stability, revealing that more complex designs improve performance and stability closer to natural walking.

Contribution

It introduces a comparative analysis of ankle exoskeletons with different DoF levels, highlighting the impact of mechanical complexity on gait and stability.

Findings

Increasing DoF improves gait parameters.

3 DoF exoskeleton yields the best stability results.

Transition from 1 to 2 DoF has a larger impact than from 2 to 3.

Abstract

Exoskeleton devices impose kinematic constraints on a user's motion and affect their stability due to added mass but also due to the simplified mechanical design. This paper investigates how these constraints resulting from simplified mechanical designs impact the gait kinematics and stability of users by wearing an ankle exoskeleton with changeable degree of freedom (DoF). The exoskeleton used in this paper allows one, two, or three DoF at the ankle, simulating different levels of mechanical complexity. This effect was evaluated in a pilot study consisting of six participants walking on a straight path. The results show that increasing the exoskeleton DoF results in an improvement of several metrics, including kinematics and gait parameters. The transition from 1 DoF to 2 DoF is shown to have a larger effect than the transition from 2 DoF to 3 DoF for an ankle exoskeleton. However, an exoskeleton with 3 DoF at the ankle featured the best results. Increasing the number of DoF resulted in stability values closer the values when walking without the exoskeleton, despite the added weight of the exoskeleton.