Type synthesis of 4-DOF parallel manipulators

The number of 4-DOF (degrees of freedom) parallel manipulators with full-cycle mobility has been small for a long time. In this paper, the type synthesis of 4-DOF parallel manipulators is performed systematically by the constraint-synthesis method. Novel 4-DOF symmetrical and asymmetrical parallel manipulators with full-cycle mobility are identified and enumerated. Moreover, structural characteristics of the 4-DOF parallel manipulators are revealed.