【作者】 韩先国；

【导师】 陈五一； 陈鼎昌；

【作者基本信息】 北京航空航天大学 ， 机械制造及其自动化， 2002， 博士

【摘要】 并联机床是90 年代中期问世的新型数控加工设备,同传统结构形式的数控机床相比具有许多优点,但是由于并联机床的出现才不过几年的时间,还有许多理论和技术问题有待攻克。本文紧密围绕并联机床的设计,对并联机床的相关理论和设计方法进行了深入的研究。由于少自由度机构有着与6 自由度Stewart 机构不同的运动学性质,需要首先确定其运动特性。本文首先采用螺旋和反螺旋理论分析了3-PSS 并联机构的运动特性,得出其动平台受到三个线性无关反螺旋力偶的约束,限制了其三个转动自由度,只能具有三个平动自由度。在此基础上,结合其位置方程,将3-PSS 并联机构简化为一简单的等效机构,从而得到其位置正解的解析解。对于6-SPS 位置正解,本文基于路径跟踪原理,提出了预估-校正法。采用该方法针对一组杆长,通过选择不同初值,可找出3-6 式Stewart 并联机构的所有16 组位置正解。本文还将并联机构的每一正解定义为一个构型,机构只能在一构型空间中运动。对于奇异性,本文提出并联机构产生奇异的原因为位置存在多解性,奇异应分布在不同构型空间交界上的新观点。为此,在位置正解的基础上,验证了所有中外已发现的著名Stewart 平台机构奇异,结果均是不同构型空间的交界。随后分析了Stewart 的奇异曲面,并给出了其姿态奇异曲面的分布特征。通过对6-PSS 并联机构的奇异进行分析,得出奇异复杂性与位置正、反解复杂性是一致的结论。最后还分析了结构参数对奇异性的影响关系。并联机构的设计需要满足多项性能指标要求:如工作空间,灵活度等。本文采用快速极坐标搜索法确定6-PSS 并联机构工作空间边界,并总结了工作空间边界的特征。并联机构的灵活度是反映并联机构速度和承载力的综合传动性能,也是并联机床结构参数设计所需考虑的重要因素,可以用雅可比矩阵条件数来衡量。本文分析了6-PSS 并联机更多还原

【Abstract】 Parallel Kinematics Machines (PKMs) are a new type of CNC machines, and it has many advantages over the conventional serial machines. But PKMs also have lots of theoretical and practical problems to be solved because it was just several years away from the 90s metaphase of last centuries when it was published first. Focused on the development of new PKMs, relative theory and design method were studied in the dissertation. The 3-degree of freedom (DOF) mechanism has difference kinematics characteristics from the 6-DOF Stewart platforms, and its kinematics characteristics must be determined first. The screw theory and anti-screw theory were applied to analyze the 3-PSS mechanism kinematics characteristics, and a constraint from three linearly independent anti-screw moments was shown to act on the moveable platform of the 3-PSS mechanism, which then could move only in three-translation direction. Based on the 3-PSS kinematics equation, the 3-PSS mechanisms was simplified to such a simple mechanism that its forward kinematics could be solved easily by analytical approach. As for 6-SPS parallel manipulators, a predictor-corrector method to get the forward solution was proposed based on the principle of position tracking, and all the 16 forward solutions of 3-6 Stewart platform were obtained through difference initial values when the lengths of six legs were specified. In this dissertation every forward solution was defined as an assembly configuration, and the parallel manipulator could move only in one configuration space. A new viewpoint concerning parallel manipulator’s singularity was put forward. The reason for the singularities was its multiple kinematics’s solutions and the singularities existed on the borders of different configuration space. All the famous singularities of Stewart platform found before were studied based on the forward solutions. It was demonstrated that all the singularities did exist on the borders of different configuration space. The singular更多还原