中文摘要：

基于并联机构奇异位形产生的运动学原理，推导出3／6-SPS型Stewart机构奇异轨迹的解析表达式，并基于此原理提出了分析并联机构奇异位形的等效机构法，利用此方法推导出了3／6-SPS型Stewart机构处于一般姿态时在θ-平面上的奇异轨迹方程，并对其轨迹的性质进行了识别。研究结果表明，3／6-SPS型Stewart机构在相互平行的θ-平面上的奇异轨迹总是一二次多项式，包括四对相交直线、一条抛物线及双曲线束。在分析的基础上，对该并联机构处于各种姿态时的奇异轨迹的性质进行了总结。

英文摘要：

Based on the new singularity kinematics principles, a cubic polynomial expression that represented the singularity loci of 3/6--SPS Stewart manipulator was obtained and a singularity-e- quivalent- mechanism was proposed as well. Using this singularity-equivalent-mechanism, the singularities of the manipulator in θ-planes for general orientations were addressed and their properties were identified in detail. It shows that singularity loci of the 3/6-SPS Stewart manipulator in parallel θ--planes are all quadratic expressions, which contain infinite hyperbolas, four pairs of intersecting lines and a parabola. At the end, we explicitly generalize all possibilities of the singularity loci for all possible orientations of the 3/6-SPS Stewart manipulator.