Design of Large Motion Range and Heavy Duty 2-DOF Spherical Parallel Wrist Mechanism

Wrist mechanisms are important elements of robotic arms because they significantly affect the arm’s handling ability. Although various wrist mechanisms have been developed to date, a mechanism with a compact structure, a wide range of motion and a large load capacity has not yet been realized. Thus, in this paper, we propose 2-DOF Spherical Parallel (2DSP) mechanism, a heavy-duty wrist mechanism with a large motion range, and clarify its features both analytically and experimentally. The 2DSP mechanism is driven by a 2-DOF spherical parallel mechanism and is supported by a universal joint located at its center. This structure allows the 2DSP mechanism to realize a large motion range and load capacity and simplifies its kinematic analysis. Based on this analysis, we clarify the design process to maximize the motion range and propose a preferable structure of passive joints from the viewpoint of load capacity and production cost. We also describe the detailed design of a 2DSP mechanism for a rescue robot we developed previously and verify the feasibility of the proposed mechanism.