Design Proposal for Resolving Misalignment in a Powered Knee Exoskeleton Without a Hard Cuff

Abstract

For proper assistance, a powered knee exoskeleton requires accurate alignment between the exoskeleton joint and the knee joint. When misalignment occurs, the load applied to the knee joint increases, thereby elevating the risk of injury. Such misalignment is often attributed to factors such as cuff design and inaccurate positioning of the exoskeleton. In particular, when a hard cuff is used, user body-shape variations may cause unintended cuff positioning or twisting that leads to misalignment. To address these issues, this study proposes a design that mitigates misalignment between the powered knee exoskeleton and the knee joint without relying on a hard cuff. Specifically, the anatomical structure of the calf, a position-fixing design using pads, and a brace donning guide employing magnetic components are introduced to resolve these issues. Based on these considerations, the final design of the knee exoskeleton is presented. To evaluate the effectiveness of the proposed methods in mitigating misalignment, comparative experiments were conducted using a conventional ACL knee brace-based exoskeleton equipped with hard cuffs. The experimental results demonstrated that the proposed knee exoskeleton effectively mitigated several types of misalignment. Furthermore, the results revealed interrelationships among some of the misalignment categories.