基于结构降耦的一类低耦合度新型3T1R并联机构的拓扑设计

Topological Design for a Class of Novel 3T1R Parallel Mechanisms with Low Coupling Degree Based on Coupling-Reducing

四自由度的可实现SCARA型(三平移一转动)输出运动的并联机构,与三自由度的Delta机构相比,因其本身的拓扑结构复杂,导致运动学正解以及动力学计算复杂,从而使其新机型的研究和开发应用相对困难;而降低这些机构的耦合度(简称结构降耦)可直接降低机构运动学、动力学求解的难度。根据笔者提出的机构结构降耦方法,对笔者最近提出的一类5个耦合度值κ为2且具有较好实用价值的SCARA型新型并联机构进行了结构降耦优化,得到了耦合度较低(降为κ=1)但自由度和动平台输出运动类型均保持不变的10个SCARA新机型,而这10个低耦合度(κ=1)机构的运动学正解及动力学正反解,可用一维搜索法方便求得数值解,或从易导出的1个一元高次代数方程求得封闭解,为其进一步构型拓扑优化、设计及应用研究奠定了基础。

Comparing to the 3-DOF Delta mechanism, the 4-DOF parallel mechanisms which might achieve selective compliance assembly robot arm（SCARA ） motion （i. e., three translations and one rotation） had their own complex topological structures？ which resulted in the complexity of solu-tions for forward kinematics and dynamics. Therefore,the researches and developments of novel SCARA parallel mechanisms were still open issues. Reducing coupling degrees of these mechanisms might directly reduce the difficulties of solutions for forward kinematics and dynamics of the mecha-nisms. Based on the methods for structure coupling-reducing proposed by the authors, the structure coupling-reducing optimization design for five novel practical SCARA mechanisms whose coupling de_ gree /c were 2 proposed by authors was performed. Ten novel SCARA mechanisms with coupling de_ gree/ c=l were obtained,both their degrees of freedom and the output motion type of the moving platform kept to be constant. Thus,the solutions for forward kinematics and dynamics of these ten novel mechanisms with coupling degree/c = l might be easily obtained by using one dimensional search method, or by solving a one-variable polynomial equation derived. This paper provides a theoretical basis for topological optimization, design and applications for these novel SCARA mechanisms.