Design and Analysis of a Cable Driven Articulated Rehabilitation System for Gait Training

Abstract

Assisted motor therapies play a critical role in enhancing functional musculoskeletal recovery and neurological rehabilitation. Our longterm goal is to assist and automate the performance of repetitive motortherapy of the human lower limbs. Hence, in this paper, we examine the viability of a lightweight and reconfigurable hybrid (articulatedmultibody and cable) robotic system for assisting lowerextremity rehabilitation and analyze its performance. A hybrid cableactuated articulatedmultibody system is formed when multiple cables are attached from a groundframe to various locations on an articulatedlinkagebased orthosis. Our efforts initially focus on developing an analysis and simulation framework for the kinematics and dynamics of the cabledriven lower limb orthosis. A Monte Carlo approach is employed to select configuration parameters including cuff sizes, cuff locations, and the position of fixed winches. The desired motions for the rehabilitative exercises are prescribed based upon motion patterns from a normative subject cohort. We examine the viability of using two controllers—a jointspace feedbacklinearized PD controller and a taskspace forcecontrol strategy—to realize trajectoryand pathtracking of the desired motions within a simulation environment. In particular, we examine performance in terms of (i) coordinated control of the redundant system; (ii) reducing internal stresses within the lowerextremity joints; and (iii) continued satisfaction of the unilateral cabletension constraints throughout the workspace.