Kinematic Analysis of a Novel 4-DOF 3T1R Parallel Manipulator

A novel four degree-of-freedom (DOF) Parallel Manipulator (PM) with a 2P Pa*PaR configuration is proposed to generate 3-DOF Translational and 1-DOF Rotational (3T1R) motions. This PM consists of a base, two identical limbs and a rigid moving platform, while each limb is driven by a prismatic joint and a revolute joint respectively through an orientation keeping mechanism and a parallelogram. The orientation keeping mechanism is made up of a link, two pulleys, and a belt. The advantages of the PM are symmetric geometry with fewer number of moving parts, simple kinematics with fewer singularity configurations, and infinite extension of translational workspace along its linear guide direction. Based on the 2P Pa*PaR PM, the mobility analysis is conducted by utilizing the screw theory, while a geometrical projection method is proposed to simplify the displacement analysis. A closed-loop vector approach together with variable elimination technique is employed for its velocity analysis, and the kinematic singularity issue is addressed by the rank analysis of Jacobian matrices. Finally, a numerical workspace generation algorithm is implemented for the workspace analysis.