A Generalized Framework for the Assessment of Various Configurations of Cable-Driven Mobile Lower Limb Rehabilitation Exoskeletons

Abstract

The overall increase in the number of stroke patients and the high cost and limited accessibility to rehabilitation services have motivated the design and development of mobile exoskeletons. However, the majority of existing lower limb exoskeletons continue to be heavy, inducing unnecessary inertia and inertial vibration on the limb. Cable-driven exoskeletons can overcome these challenges without the need for exact joint alignment. The routing and configuration of cables can be accomplished in various ways while designing the exoskeleton. In this work, we propose a generalized framework for assessing the viability of cable-driven exoskeletons designs based on various routing and configurations of cables. In the current proposed framework, the lower limb has been modeled as a two-link model, and the desired trajectory is tracked via impedance control. The passive elastic joint moment is considered as user voluntary input from the impaired leg. Four conceptual models with 2-, 3- and 4- cable configurations have been generated as case studies and the resulting model trajectories were compared. Our preliminary results revealed that a 4-cable configuration is a promising design option for lower limb rehabilitation based on tracking performances, cable tensions, and component forces.

Keywords: Stroke rehabilitation, Lower limb exoskeleton, Cable-driven exoskeleton, Mobile rehabilitation robots, Exoskeleton design framework