Patrick Shawanee', Anil Kumar Namita, Hur Pilwon
Department of Mechanical Engineering, Texas A&M University, College Station, TX, United States.
Department of Mechanical Engineering, Gwangju Institute of Science and Technology, Gwangju, South Korea.
Front Neurorobot. 2022 May 30;16:790070. doi: 10.3389/fnbot.2022.790070. eCollection 2022.
State-of-the-art knee braces use a polycentric mechanism with a predefined locus of the instantaneous center of rotation (centrode) and most exoskeleton devices use a knee mechanism with a single axis of rotation. However, human knees do not share a common centrode nor do they have a single axis. This leads to misalignment between the assistive device's joint axis and the user's knee axis, resulting in device migration and interaction forces, which can lead to sores, pain, and abandonment of the device over time. There has been some research into self-aligning knee mechanisms; however, there is a lack of consensus on the benefit of these mechanisms. There is no research that looked purely at the impact of the knee mechanisms, either. In this article, we compare three different knee brace mechanisms: single axis (SA), polycentric with predefined centrode (PPC), and polycentric with a self-aligning center of rotation (PSC). We designed and conducted an experiment to evaluate different joint mechanisms on device migration and interaction forces. Brace material, weight, size, cuff design, fitment location, and tightness were consistent across trials, making the knee joint mechanism the sole variable. The brace mechanisms had no significant effect on walking kinematics or kinetics. However, the PPC brace had greater interaction forces on the top brace strap than the SA and PSC. The PSC and SA had significantly lower interaction forces on the bottom strap compared to the PPC brace. The PSC had significantly less migration than both the SA and PPC braces. These results show that a PPC mechanism may not be beneficial for a wide range of users. This also shows that the PSC mechanisms may improve mechanism alignment and lessen device migration.
最先进的膝关节支具采用多中心机制，具有预定义的瞬时旋转中心轨迹（中心曲线），而大多数外骨骼设备采用单旋转轴的膝关节机制。然而，人类的膝盖既没有共同的中心曲线，也没有单一的轴。这导致辅助设备的关节轴与使用者的膝盖轴不对齐，从而产生设备移位和相互作用力，随着时间的推移，可能会导致疼痛、皮肤溃疡以及使用者放弃使用该设备。已经有一些关于自对准膝关节机制的研究；然而，对于这些机制的益处尚未达成共识。也没有研究单纯关注膝关节机制的影响。在本文中，我们比较了三种不同的膝关节支具机制：单轴（SA）、具有预定义中心曲线的多中心（PPC）和具有自对准旋转中心的多中心（PSC）。我们设计并进行了一项实验，以评估不同关节机制对设备移位和相互作用力的影响。在所有试验中，支具材料、重量、尺寸、袖带设计、佩戴位置和松紧度都是一致的，使得膝关节机制成为唯一的变量。支具机制对步行运动学或动力学没有显著影响。然而，与SA和PSC相比，PPC支具在上部支具带上的相互作用力更大。与PPC支具相比，PSC和SA在下部支带上的相互作用力显著更低。PSC的移位比SA和PPC支具都要少得多。这些结果表明，PPC机制可能对广泛的用户没有益处。这也表明，PSC机制可能会改善机制对准并减少设备移位。
