以基本运动链为单元的并联机构拓扑结构设计

研究了以基本运动链(BKC)为单元的并联机构组成原理及其拓扑结构设计方法。首先,提出基于BKC的并联机构组成原理表达式;其次,基于BKC的组成原理及其耦合度k的计算公式,设计给出理论上满足k=0~3且基本回路v=1~5的53种BKC基本类型及其解析表达式;其中,最常用的6种BKC基本类型能解析表示出40种BKC拓扑结构,而这些BKC拓扑结构成为常用并联机构的基本组成单元;最后,提出一种直接以BKC为设计单元,同时满足方位特征集(POC)设计目标的并联机构拓扑结构设计的一般性实用方法,并以实例说明。该方法无需综合支链及其在动、静平台之间的拓扑布置,仅含3个步骤,操作简单,具有很好的实用性;与已有的主要型综合理论方法相比,操作简单、方便,具有很好的实用性和普适性。

Topology Structure Design of Parallel Mechanisms Based on Basic Kinematic Chains

The parallel mechanism composition theory and the design method for topology structure of the parallel mechanisms were studied based on the basic kinematic chain (BKC) units. Firstly, a new expression for the parallel mechanism composition theory based on BKC was proposed, which had clear physical meaning. Secondly, according to the composition theory and the formula for calculating the value of the coupling degree k , 53 kinds of BKC with coupling degree k =0~3, the basic loop v =1~5, as well as their analytical expressions were presented. It was found that there were six mostly common types of basic BKCs and these basic BKCs can constitute 40 kinds of BKC topology structure which are the basic unit of parallel mechanism. A concept of virtual POC set of BKC topology structure was proposed and 40 kinds of BKC topology structures were classified according to 13 kinds of virtual POC sets with the coupling degree k , which provided the composition unit, i.e., building block of a parallel mechanism, for designing the topology structure of parallel mechanisms. Finally, a general and practical method for topology structure design of parallel mechanism was presented with BKC as the composition units, and meeting the position and orientation characteristics (POC) set as the design goal. Three examples were illustrated. The method had only three steps and no need to synthesize the branch chains and their topology structures between the base and the moving platform. Compared with the existing four main methods for type synthesis, this new method has better usability and universality.