Dexterity and stiffness analysis of a three-degree-of-freedom planar parallel manipulator with actuation redundancy

The current paper deals with the dexterity and stiffness of a three-degree of freedom (DOF) planar parallel manipulator with actuation redundancy, which is a subpart of a four-DOF-hybrid machine tool. Based on the kinematics, the dexterity is analysed. The stiffness indices, which are the maximum deflection of the moving platform under the action of a unit force and the minimum eigenvalue of the stiffness matrix of the manipulator, are presented for investigating the stiffness. According to the minimum eigenvalue index, it is proved that actuation redundancy can improve the stiffness of the parallel manipulator. Moreover, the relationship between the singular configuration and the stiffness of the parallel manipulator is discussed. Compared with the corresponding non-redundant parallel manipulator without the redundant link, the redundantly actuated parallel manipulator has better dexterity and higher stiffness.