球面并联机构自由度的终端约束分析方法研究

Research on the Analytical Terminal Constraints for the Degrees of Freedom of Spherical Parallel Mechanisms

旋量法以其几何概念清楚,物理意义明确,表达形式简单等优势,常被用于分析机构的终端约束和自由度,然而该方法针对多支链并联机构的分析过程繁琐、耗时长。为解决上述问题,文章以2自由度Omni-Wrist V球面并联机构为研究对象,采用基于几何约束理论的图谱法,通过特定的规则绘制出机构的自由度线和约束线,确定机构的终端约束,进而推导出机构的运动模式。对比用旋量法分析该球面并联机构的终端约束,两种方法虽然殊途同归,然而图谱法简单直观,容易理解,且更为快捷有效。

Screw method is often used to analyze the terminal constraints and DOF of mechanisms for its advantages of legible geometry concept, explicit physical meaning and simple expression form, etc. However, this method is cumbersome and time consuming for analyzing the parallel mechanisms with multiple branches. In order to solve the above problem, ,the visual graphic approach based on constraint theory is used and a 2- DOF spherical parallel manipulator Omni-Wrist V is studied in this paper. Draw out the freedom line and the constraint line of the mechanisms by specific rules, to determine its terminal constraint,and then derive the motion patterns of the mechanisms. By comparing the screw method and graphic approach, although two methods can achieve the same end, the latter is more concise and more intuitive, easier to understand, and more efficient and effective.