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.

翻译：外骨骼设备不仅因其附加质量，也因其简化的机械设计，对使用者的运动施加运动学约束并影响其稳定性。本文通过佩戴具有可变自由度（DoF）的踝关节外骨骼，研究由简化机械设计产生的这些约束如何影响使用者的步态运动学与稳定性。本文所采用的外骨骼允许踝关节处具有一、二或三个自由度，以模拟不同水平的机械复杂度。该效应在一项包含六名参与者在直线路径上行走的初步研究中进行了评估。结果表明，增加外骨骼的自由度可改善包括运动学和步态参数在内的多项指标。对于踝关节外骨骼，从1自由度过渡到2自由度所产生的影响大于从2自由度过渡到3自由度。然而，具有3自由度的踝关节外骨骼表现出最佳结果。尽管外骨骼增加了重量，但增加自由度数使得稳定性数值更接近未佩戴外骨骼时的行走数值。