Kinematic analysis of a new 2-DOF parallel wrist with a large singularity-free rotational workspace

Abstract

This paper introduces a novel dexterous overconstrained 2-DOF parallel wrist with a large singularity-free range of motion. This mechanism produces a 2-DOF sphere on sphere pure rolling motion. The mechanism is compact, lightweight, stiff and fast. These properties make this robot a good candidate for different types of applications, namely, arm wrist, tracking , gimbals, pointing mechanisms and others.Using a geometrical approach, the compact parametric closed-form inverse and forward kinematic models of the mechanism and the Jacobian matrices are derived and it is shown that the mechanism is singularity-free throughout the whole range of motion. It is shown that, with a proper choice of design parameters, a large rotational and translational workspace can be obtained. The correctness of the derived inverse and forward kinematics models is verified by comparing with the results that are obtained using MSC Adams software. Finally, A contact interference analysis is performed in the CAD software and the practical workspace of the proposed mechanism is extracted and compared to that of the Omni-Wrist III with the same dimensions.