Abstract “Two rotational degrees of freedom” and “one translational degree of freedom” (2R1T) parallel mechanisms (PMs) have been successfully applied to develop five-axis hybrid robots for machining purposes. However, the number of passive joints contained in current 2R1T PMs has not still reached the minimum, which may impede these robots from having high stiffness. This study has put forward the concept of ultimate constraint wrenches acting on the PM's moving platform, and this concept was used to reduce the number of kinematic joints to a minimum. Based on the reciprocal screw theory, an ultimate constraint wrench system of the 2R1T PMs was found, and then a series of novel overconstrained 2R1T PMs with the fewest kinematic joints, containing three or four branches, were constructed. Furthermore, based on a developed overconstrained four-branch 2R1T PM R P U-2U P R-RPR, a type of five-axis hybrid robot with the fewest kinematic joints was constructed, which demonstrated good application prospects.

中文翻译：

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基于极限约束扳手的运动学关节最少的过约束2R1T并联机构的类型综合

摘要 “两个旋转自由度”和“一个平移自由度”（2R1T）并联机构（PM）已成功应用于开发用于加工目的的五轴混合机器人。然而，目前2R1T PM中包含的被动关节数量还没有达到最低限度，这可能会阻碍这些机器人具有高刚度。本研究提出了作用在PM移动平台上的极限约束扳手的概念，并利用该概念将运动关节的数量减少到最少。基于互易螺钉理论，找到了2R1T PMs的极限约束扳手系统，然后构建了一系列具有最少运动关节的新型过约束2R1T PM，包含三或四个分支。此外，