Structure synthesis and singularity analysis of a parallel manipulator based on selective actuation

A parallel manipulator (PM) based on 3-limb design termed a selectively actuated parallel manipulator (SA-PM) is proposed. The end-effector of the manipulator can produce 3-DOF spherical motion, 3-DOF translation, 3-DOF hybrid motion, or complete 6-DOF spatial motion depending on the types of the actuation (rotary or linear) chosen for the actuators. The manipulator architecture decouples translation and rotation of the end-effector for individual control. The structure synthesis of SA-PM is achieved using the line geometry. A Lego model of the SA-PM is built for the constructibility and preliminary study. Singularity analysis of the SA-PM based on geometry is presented for all actuation schemes to facilitate the kinematic design of the manipulator. Because of the decoupled motion, the SA-PM has a great potential for high precision motion alignment and assembly, especially in micro- or nano-motion stage design.