Kinematic Analysis of a 4-DOF Parallel Mechanism with Large Translational and Orientational Workspace

This paper introduces a novel four-degree-of-freedom (4-DOF) parallel mechanism having 3 translational DOFs and 1 rotational DOF. The mechanism comprises 2 sets of parallelogram linkages, which constrain two of the rotational DOFs of the mechanism. An interesting feature of the mechanism is that it can be driven using 4 parallel sliders mounted on its base. As a result, one of the translational DOFs can be infinitely large. Also, the architecture of the mechanism provides a large rotational DOF in one direction. The kinematic equations of the mechanism are derived and the Jacobian matrices are obtained. The mathematical conditions that lead to singularities are also found. Moreover, a geometric description of the boundaries of the workspace is given, which can be expressed using simple equations. Finally, some design examples are proposed and a prototype is presented.