Real Time Estimation of Glenohumeral Joint Rotation Center With Cable Driven Arm Exoskeleton (CAREX)—A Cable Based Arm Exoskeleton

Abstract

In the past few years, the authors have proposed several prototypes of a Cabledriven upper ARm EXoskeleton (CAREX) for arm rehabilitation. One of the assumptions of CAREX was that the glenohumeral joint rotation center (GHc) remains stationary in the inertial frame during motion, which leads to inaccuracy in the kinematic model and may hamper training performance. In this paper, we propose a novel approach to estimate GHc using measurements of shoulder joint angles and cable lengths. This helps in locating the GHc center appropriately within the kinematic model. As a result, more accurate kinematic model can be used to improve the training of human users. An estimation algorithm is presented to compute the GHc in realtime. The algorithm was implemented on the latest prototype of CAREX. Simulations and preliminary experimental results are presented to validate the proposed GHc estimation method.