Kinematic Analysis and Stiffness Characteristics of a Hybrid 2-DOF 7-Bar Linkage

Abstract

Parallel mechanisms have drawn interest due to many advantages such as large payload ratio, high structural stiffness, low inertias and high dynamic capacities. But there are also drawbacks such as limited workspace and more singularities. Therefore many research efforts have been given to hybrid mechanisms, especially to hybrid serial-parallel mechanisms. This paper presents a new hybrid 2-DoF 7-bar linkage and several related linkages. Such mechanisms allow much larger range of movement than parallel mechanisms, yet have larger stiffness than serial mechanisms, and are desirable for robot fingers and limbs. Kinematic properties of the hybrid 2-DoF 7-bar planar linkage are analyzed. Comparative analyses between it and several 2-DoF linkages are given based on conditioning mapping, stiffness mapping, global conditioning index and global stiffness index. The results demonstrate the applicability of such linkages.