Development of a 2-DOF Spherical Joint with Extended Range of Motion Achieves Continuous Rotation

Abstract

The development of an innovative two-degrees-of-freedom (2-DOF) active spherical joint (universal joint) that can provide an extended range of motion and perform continuous rotation in both DOFs is reported. The workspace of the 2-DOF joint in general arrangements is explored. To overcome the structural limitation of the general configurations of the joint, this work proposes a new design that incorporates rotatable C-shaped rails to avoid collision among components of the joint. The dynamic model of the 2-DOF joint is constructed, and its behaviors in the simulation are analyzed. The trajectories are generated in simulation to better understand the joint torque requirement. A prototype of the 2-DOF joint was fabricated, and its performance was experimentally evaluated. The experimental results confirm that the continuous rotation of the two DOFs in a wide range is feasible and that the RMSEs of positions were less than 2% within the motion range, and those of orientations were less than 0.6% along the entire rotations, with standard deviations under 0.4 mm and 0.6 degree.