Type synthesis of novel three-translation redundant actuated parallel mechanisms with closed-loop units

Abstract Three-translation (3T) redundant actuated Delta/Par4-like manipulators with closed-loop units (CLU) are widely used in logistics sorting, industrial packaging, and other applications due to their superior load-carrying capacity and dynamic performance. However, compared to conventional 3T parallel mechanisms (PMs), there are fewer configurations of 3T redundant actuated PMs with CLU, and the existing CLU are of a single configuration. This paper introduces a method for synthesizing a 3T redundant actuated PM with CLU based on the atlas method. First, the degrees of freedom (DOF) line diagrams and constraint line diagrams of the moving platform are determined sequentially. By applying the dual rule, the constraint diagrams are decomposed, yielding six dual DOF spaces. The equivalent DOF line diagrams are expanded using the principle of line equivalence, which synthesizes a variety of novel 4- and 5-DOF branched chains with CLU. Second, considering the geometrically symmetric distribution criterion of the branched chains, two assembly schemes for redundant actuated 3T PMs with CLU are proposed, yielding at least 432 and 324 novel configurations, respectively. Finally, two representative novel mechanisms are selected, and their DOF properties are verified using screw theory, which demonstrates the feasibility and applicability of the synthesized method. This method systematically synthesizes novel redundant actuated 3T PMs with CLU, laying the foundation for further research into innovative CLU configurations.