3T1R并联机构结构降耦设计与运动学分析

根据基于方位特征(POC)的并联机构设计理论与方法,提出了一种结构简单、能实现三平移一转动的并联机构,拓扑结构分析后发现其耦合度k较大(k=2),其位置正解及动力学计算较复杂;为此,设计了结构降耦后的新机型,证明其耦合度k=1,其位置正解易用一维搜索法求出,并给出了基于序单开链法的该机构位置正解求解的一维搜索法及其数值解;同时,基于导出的机构位置反解公式,分析了动平台的工作空间及其转动能力,探讨了该机构发生3种奇异位形的条件。

Structure Coupling-reducing Design and Kinematics Analysis of 3T1R Parallel Mechanism

There is a wide range of industrial applications for the 4-DOF parallel mechanism which can achieve SCARA type output motion (i.e., three translations and one rotation). However, due to the complex topological structures, the research and development of its new model are still relatively few. Firstly, according to the parallel mechanism design theory and method based on the orientation characteristic (POC), a SCARA type parallel mechanism whose structure was simple was proposed. Because the coupling degree was 2, positive solution of position and dynamics calculation of the parallel mechanism were very complex. So the new model after structure coupling-reducing (k=1) was given, its positive solutions can be easily solved by one-dimensional search method. Then the three main topological characteristics of POC set, degree of freedom and the coupling degree were respectively analyzed. The kinematics analysis of the new model whose coupling degree was one after structure coupling-reducing was given, and the solution algorithm for the forward position of this parallel mechanism was established. This method can obtain all the numerical solutions of the forward position by using one-dimensional searching method, and can verify the correctness of the forward position by the derived calculation formula of the inverse position. Finally, based on the inverse position of the mechanism, the working space of this parallel mechanism was obtained and the singularity of the mechanism was discussed, which provided a theoretical foundation for the prototype design and application of this mechanism.