中文摘要：

根据基于方位特征集和序单开链单元的并联机构拓扑结构设计理论,提出了一种基于基本回路过约束特性的无过约束并联机构设计方法。首先,分析动平台方位特征集、支链方位特征集以及基本回路独立位移方程数三者之间的关系,确定了少自由度无过约束并联机构构型的存在条件,给出了无过约束并联机构构型综合的方法和步骤。然后,按照支链类型及其对动平台提供的约束不同,将无过约束并联机构构型分为3类,表明通过不同类型的支链组合可得到不同性能的无过约束并联机构新构型。最后,通过典型实例总结无过约束并联构型的支链组成及其装配规律。

英文摘要：

Based on the theory of POC and ordered single-opened-chain,a design method for structural synthesis of lower-mobility non-overconstrained parallel mechanisms（ PMs） was proposed according to the over-constraint characteristics of independent loops. Firstly,the relationships between POC of mobile platform,POC of kinematic limbs and the number of independent displacement equations of independent loops were analyzed. The existence condition of lower-mobility non-overconstrained PMs was obtained,and the universal method and step for structural synthesis were further proposed. Secondly,the nonoverconstrained PMs can be classified into three types of configurations according to different combinations of kinematic limbs and their corresponding constraints on the platform,which showed that the nonoverconstrained PMs composed with different types of kinematic limbs had different performances.Finally,the rules of possible kinematic limbs and their assembly modes were illustrated by comparative analysis with a few examples. The research results enriched the analysis theory and methods of nonoverconstrained PMs,and laied the foundation for type selection and applications of lower-mobility nonoverconstrained PMs.