一种非全对称低耦合度三平移一转动并联机构的设计及其运动学

提出一种非全对称的三平移一转动（3T1R）的并联机构，并对其进行拓扑特性分析，发现其耦合度κ较大(κ=2)，这表明其位置正解求解复杂。为此，对该机构进行拓扑结构降耦设计，得到一种低耦合度（κ=1）但基本功能(动平台输出方位特征和自由度)不变的降耦机构；然后，根据基于序单开链的机构运动学建模原理，给出了该降耦机构位置正解的一维搜索求解算法及其数值解；通过导出的位置反解公式，对该降耦机构的工作空间、转动能力和奇异性进行了分析。该降耦机构结构简单、制造容易、工作空间大、转动能力强。

Design and Kinematics for a Not-fully Symmetric 3T1R Parallel Mechanism with Low Coupling-degrees

A not-fully symmetric parallel mechanism with 3T1R motion outputs was designed. Coupling degree of the parallel mechanism was found bigger（κ=2）after its topological characteristic analysis was performed, for which solutions for its direct kinematics were more complicated. Therefore, a novel coupling-reducing parallel mechanism were proposed whose position and orientation characteristics and degree of freedom were unchanged with low coupling degree (κ=1). Further, one-dimension search algorithm was applied to solve its direct kinematics according to kinematics modeling principle based on ordered single opened chains. In addition, the workspace, rotation capability and singularity of this coupling-reducing parallel mechanism  were also analyzed according to the inverse kinematics. From the above analyses, the conclusions are drawn that the structures of this coupling-reduced mechanism are simple, and workspace and rotation capability of this parallel mechanism  are larger.