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,onedimension 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.%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.
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