Performance verification of a kinematic prototype 5-DOF upper-limb exoskeleton with a tilted and vertically translating shoulder joint

In this paper, the performance of the 5-DOF upper-limb exoskeleton with a tilted and vertically translating shoulder joint, which was proposed in our previous work, is verified by simulations and experiments. In this design, one vertical prismatic joint was added for the vertical translation of the shoulder, and the shoulder joint was tilted to avoid the singularity problem. Based on the kinematic analysis in our previous work, the manipulability analysis was performed to determine the tilting angles and to check whether the singularity problem was appropriately addressed by the proposed design. The natural motion enabled by the added vertical translation was experimentally verified. For the experiments, an unactuated prototype of the proposed exoskeleton system was designed and manufactured. The experiment was focused on the decrease of the load on user's shoulder with a vertically translating shoulder joint. The three axis forces at the shoulder joint were compared with those of conventional upper-limb exoskeleton whose shoulder joint was fixed. The simulation and experimental results show that the proposed upper-limb exoskeleton design is suitable for supporting natural motions of the upper-limb.