基于POC法的多环耦合并联机构拓扑特征分析

POC Method Based Topology Characteristic Analysis of Multi-loop Coupled Mechanisms

应用基于POC集和SOC单元的并联机构拓扑结构设计方法(简称POC法),对2个典型的多环耦合机构进行了拓扑特性分析,分析表明,需要在相应的自由度公式和约束度公式中,减去相应的'耦合次数',才能计算出正确的机构自由度和耦合度,拓扑特征的总体计算过程、步骤和一般并联机构的拓扑特征分析相同;同时表明,POC法能有效分析多环耦合并联机构,且物理、几何意义明确,操作简便易懂;多环耦合机构的结构看似复杂,但其耦合度相对较低,其运动学、动力学分析并不很复杂,因此,也具有一定的应用推广价值,当然,其应用的背景本身有待探索。

Multi-loop coupled mechanism is a new kind of complicated mechanism which has been used in bio-robot, aviation, refuge and other areas. However, it is deficient in theoretical study. The most basic understanding for a new mechanism is to realize its mobility. Multi-loop coupled mechanism, i. e. , serial-parallel hybrid mechanism, is different from the general parallel mechanism, and the former is coupled with each other among the branch chains. Therefore, the analysis of topology structure characteristic of multi-loop coupled mechanism is much more complex. Using the topological structure synthesis theory for parallel mechanism based on POC set and SOC unit （ POC method, for short） , the two classic multi-loop coupled mechanisms, symmetrical and asymmetrical ones, were analyzed. The correct degree of freedom and coupling degree could be calculated only if ＂ coupling-number＂ was subtracted correspondingly by number of degree of freedom （DOF） and constrain degree when using the corresponding DOF formula and constrain formula. The coupling-number meant the coinciding number for over three branch chains, which was similar to the multiple-kinematic joint in the planar linkages. The result demonstrated that POC method can effectively analyze the multi-loop coupled mechanisms, and its physical and geometrical meanings were clear and the operation was simple and easy to understand. The structure of the multi-loop coupled mechanisms was seemingly complex, but its coupling degree was relatively low compared with 6-SPS Stewart-Gough platform with coupling degree of 3, and the kinematics and dynamic analyses were not complex. Therefore, the multi-loop coupled mechanisms have potential application value, and the application background still needs to be explored.