Kinematic Analysis and Optimal Design of a New 3T1R Parallel Mechanism

Decoupled motions in low mobility parallel manipulators, which maintains some translation movement or orientation in space by contrast to Stewart platform that can translate and rotate in any direction, lead to more straightforward mechanical structure, larger workspace, lower cost, higher accuracy, and more natural control. A four-degree-of-freedom (DOF) 3T1R parallel manipulator is presented in this paper. This manipulator generates the family of so-called SCARA motions, Schönflies motions, or 3T1R motions, in which the moving platform can translate in all directions and rotate around an axis of a fixed direction whose rotational motion is a roll motion. The position analysis and kinematic modeling for the mechanism are performed, and its workspace size and kinematic characteristic are examined. This manipulator can be used in robotic applications involving the positioning and orientation of a rigid body with high stiffness or accuracy.