iT-Knee: An exoskeleton with ideal torque transmission interface for ergonomic power augmentation

Abstract

This work presents the development of iT-Knee, a novel modular knee exoskeleton that makes use of a torque transmission interface to deliver pure assistive torque to the knee articulation, with the objective to act as rehabilitation tool, or a single joint add-on exoskeleton device for power augmentation. The specific kinematics features employed by iT-Knee can accommodate not only the translational of the knee instantaneous center of rotation in the sagittal plane and on its orthogonal direction, but also the knee varus/valgus angle as well as the internal/external rotation tibia movements delivering pure torque only around the flexion/extension movement. This functionality results in superior transparency and comfortability which allow prolonged period of use without generating significant discomfort. The iT-Knee kinematics, its mechanism, implementation, and actuation are introduced. The Self-aligning feature combined with a fast lock/release mounting system on the human leg shortens the setup time required to wear it, increasing its user-friendly perception. iT-Knee uses a torque controlled actuation unit to generate torque around the knee flexion extension enabling the implementation of several interaction control schemes that combine assistive functionality on demand with high back drivability and transparency during unloaded free motions of the human knee. Experimental results are presented and effectively demonstrate the functionality of the iT-Knee device.