Self-Identification of the Joint Centre of a Cable-Driven Shoulder Rehabilitator

This paper presents the joint centre self-identification of a novel cable-driven anthropocentric shoulder rehabilitator. For such a wearable rehabilitator, identification of joint centre is critical for kinematic modeling, path planning and motion control. However, the shoulder joint centre location is unknown when a user wears this rehabilitator and it differs among users. These complicate the initial patient preparatory. A joint centre self-identification model is formulated based on the differential change in the cable end-point distance. A computationally effective algorithm is employed to identify the shoulder joint centre. It does not require any external measurement devices because of the redundant actuation scheme in the cable-driven shoulder rehabilitator. In order to verify the effectiveness and robustness of the proposed algorithm, we conducted computer simulation studies. In the simulation example, although large errors (up to plusmn50mm) had been injected into the initial estimates, the joint centre was always accurately identified within four to five iterations.