Topological Structural Synthesis and Classification of 2T2R Parallel Mechanism Based on POC Equations

Abstract:

The process of two translation and two rotation (2T2R) parallel mechanism (PM) type synthesis was systematically discussed according to the method of topological structural synthesis of parallel mechanism based on position ad orientation characteristic (POC) equations. The structure synthesis of complex branches, the method of judging geometric assembly condition of parallel mechanism and the judgment of drive unit of the parallel mechanism were all illustrated with examples. The type synthesis of hybrid single open chain (HSOC) branch chains was the foundation of the type synthesis of parallel mechanism, five new HSOC branches were proposed based on the complex branch synthesis method by the idea of equivalent substitution of topology structure. Totally 15 kinds of 2T2R parallel mechanisms were synthesized and classified according to branch structure and number of moving platform. Totally 10 kinds of them were new structures. Furthermore, the topological characteristics of them were analyzed, including the Assure kinematic chain (AKC), number of independent displacement equations for parallel mechanisms, degree of coupling, type of degree of freedom (DOF) and motion decoupling. In addition, according to the characteristics of topological structure, the 2T2R mechanism was classified and analyzed. These structures were simple and easy to be assembled and manufactured. All these new structures had practical value.