6-RSS型并联机构奇异性分析  

Singularity Analysis for 6-RSS Parallel Mechanism

作　　者：曹永刚[1] 张玉茹[1] 

机构地区：[1]北京航空航天大学虚拟现实技术与系统国家重点实验室,北京100083

出　　处：《机械工程学报》2008年第6期79-87,共9页Journal of Mechanical Engineering

基　　金：国家自然科学基金(50575011)

摘　　要：针对无法获得精确奇异位形空间分布的6-RSS型并联机构,寻找到一种间接表征奇异位形空间分布的方法。定义一个具有物理意义的能表征非奇异位形与奇异位形之间在静力学特性上接近程度的接近度函数,利用接近度阈值定义这种在静力学特性上接近奇异的位形为'拟奇异位形',定义所有拟奇异位形构成的空间实体集合为'拟奇异空间'。从奇异位形与拟奇异位形定义出发,论证出机构所有奇异位形必包含在拟奇异空间中,从而在无法获得精确奇异位形时利用拟奇异空间可间接地预知机构的奇异位形空间分布,避免机构进入拟奇异空间,达到避免机构处于奇异位形的目的。针对6-RSS型并联机构,利用简化后的接近度函数,获得该机构在定姿态下的拟奇异空间的多个截面图和三维实体图,为该机构在实际应用中避免奇异位形提供直观的参考依据。利用6-RSS机构的实例数据指出雅可比矩阵行列式值不能表征奇异接近程度,推证出与本文方法类似的Voglewede约束最优方程法的不足并加以修正。The exact singular configurations of 6-RSS mechanism cannot be solved because of its numeric kinematics. A method to illustrate its singular configurations indirectly is presented. According to the performance of statics, a measure function, which has a clear physical meaning, has been defined to measure the proximity to singularities. Those configurations with a tiny value of proximity are called pseudo-singular configuration, and a solid model, called pseudo-singular space, can be used to gather all those pseudo-singular configurations. It can be deduced that the pseudo-singular space must contain the entire singular locus based on their definitions. Obviously, this pseudo-singular space can be used to illustrate all of the singular configurations indirectly. If the mechanism doesn＇t move into this pseudo-singular space, it cannot arrive at the singular configuration ever. Based on the mechanism kinematics and the measure function, the pseudo-singular spaces of the 6-RSS parallel mechanism under some constant-orientations are illustrated, which can support the singular data for specific applications. It is proved from the data of 6-RSS mechanism that the determination of Jacobian matrix cannot measure the proximity to singularities, and it also points out from the range of function value that Voglewede＇s constrained optimization function, which is similar to the method of this research, has some deficiencies, and a correction of which is made.

关 键 词：并联机构 奇异性分析 奇异接近程度 6-RSS构型 

分 类 号：TP242[自动化与计算机技术—检测技术与自动化装置]