Human-Exoskeleton Misalignment Reduction on Knee Joint via an RPR Mechanism-Based Device

Lower-limb exoskeleton plays an increasingly significant role in robot-assisted rehabilitation, and the humanexoskeleton knee joint misalignment is one of the common safety concerns that obstruct the wearer's natural movement and even causes injuries. Most exoskeletons utilize a single revolute knee joint, which cannot sufficiently realize the human knee motion. Hence, the leading challenge to reduce misalignment is to precisely measure and reconstruct the wearer's knee joint motion in the sagittal plane. Towards this research goal, a wearable device with a revolute-prismatic-revolute (RPR) mechanism has been designed to measure the wearer's natural knee-joint movement and determine the exoskeleton's knee-joint trajectoi7 for better matched human-robot interaction. The RPR device features flexible adjustments to different wearer sizes. The measuring precision was validated via an optical motion capture system, and the non-interfering of natural walking was also verified. The efficacy of misalignment reduction was evaluated utilizing a simulation study based on kinematic calculations, demonstrating a reduced misalignment by 51% compared to conventional single revolute joints.