Analysis and Comparison of the Kinematic Performance of PPRRRP andRRRPU for Shoulder Rehabilitation Mechanisms

Based on the configuration synthesis and optimum principles of exoskeleton mechanism, PPRRRP and RRRPU exoskeleton configurations are proposed. In preferred configurations, the two human-machine closed chains which both consist of the exoskeleton mechanism and the human upper limb are translated into an 3-DOF (degree of freedom) exact kinematic constraints system by introducing passive joints at the connection position of the human and the exoskeleton, in order to realize kinematic compatibility. From the perspective of the whole human-machine closed chain, the kinematics models of the human-machine closed chains of PPRRRP and RRRPU are established. Through the reasonable decomposition and kinematic characteristics analysis of passive joints, the equations of kinematic constraint are deduced, and the velocity Jacobian matrices of the two human-machine closed chains are derived, and the complexities of the human-machine closed kinematic chains are reduced by this algorithm. Through the numerical simulation of velocity Jacobian matrices, reciprocal of condition number, manipulability ellipsoid and dexterous operating velocity of the two mechanisms mentioned above are analyzed and compared in the coronal plane, sagittal plane and horizontal plane. The results show that the dexterity, isotropy and dexterity of operating velocity of the PPRRRP mechanism are better than those of the RRRPU in the above three planes. On this basis, an upper limb rehabilitation exoskeleton of PPRRRP is designed.