Kinematic Modelling and Analysis of a Novel Bio-inspired and Cable-Driven Hybrid Shoulder Mechanism

The robotic shoulder rehabilitation exoskeletons that do not take into consideration all shoulder degrees-of-freedom (DOFs) lead to undesirable interaction forces and cause discomfort to the patient due to the joint axes misalignments between the exoskeleton and shoulder joints. In order to contribute to the solution of this human-robot compatibility issue, we present the kinematic modeling and analysis of a novel bio-inspired 5-DOFs hybrid human-robot mechanism (HRM). The human limbs are regarded as the inner passive restrained links in the proposed hybrid constrained anthropomorphic mechanism. The proposed hybrid mechanism combines serial and parallel manipulators with rigid and cable links enabling a match between human and exoskeleton joint axes. It is designed to cover the whole range of motion of the human shoulder with the workspace free of singularities. The numerical and simulation results from CAD model of the mechanism are presented to demonstrate the validity of the kinematic model, and the kinematic and singularity merits of the proposed mechanism. A 3D printed prototype of the hybrid mechanism was fabricated to further validate the kinematic model and its overall advantages.