Parallel robots (PRs) have singular configurations where the robot gains at least one degree-of-freedom and loses control. Theoretically, such singularity occurs when the Forward Jacobian-Matrix determinant becomes zero (Type II). However, actual PRs could lose control owing to Type II singularities for determinant values near zero, but not zero, because manufacturing tolerances introduce errors that are complex to model due to their low repeatability. Thus, using an actual 3UPS+RPU PR, this paper presents three contributions: i) a proximity detection index for Type II singularities based on the angle between two Output Twist Screws. The index can identify which kinematic chains contribute to the singularity. ii) an experimental benchmark to study Type II singularities. iii) PR configurations where the proposed index is zero and the Forward Jacobian determinant is not. In this last configuration, the findings show that the actual robot is unable to handle external actions applied to the PR.

并行机器人（PR）具有奇异的配置，其中，机器人获得了至少一个自由度并失去了控制。从理论上讲，这种奇异性发生在前向雅可比矩阵行列式变为零（类型II）时。但是，实际的PR可能由于行列式值接近零（但不是零）的类型II奇异而失去控制，因为制造公差由于其低重复性而引入了复杂的模型误差。因此，使用实际的3U P S + R PU PR，本文提出了三点贡献：i）基于两个输出拧紧螺钉之间的角度，用于II型奇点的接近度检测指标。该指数可以确定哪些运动链有助于奇异性。ii）研究II型奇点的实验基准。iii）建议的索引为零而前向Jacobian行列式不是的PR配置。在最后的配置中，调查结果表明实际的机器人无法处理应用于PR的外部动作。