Type synthesis of overconstrained dual parallel mechanisms with three and four degrees of freedom

Dual parallel mechanism as a novel accurate positioning device with large workspace is promising in the field of macro/micro manipulator. To construct spatial dual parallel mechanisms for given tasks, a mechanics definition and a systematic procedure for the synthesis of the overconstrained dual parallel mechanisms based on the screw theory are presented. As examples, the synthesis procedures of 3-DOF dual parallel mechanisms with three translational motions and 4-DOF dual parallel mechanisms with three translational motions and one rotational motion are given, and several novel dual parallel mechanisms of structural symmetry are developed.