Singularities in three-legged platform-type parallel mechanisms
Singularities in three-legged platform-type parallel mechanisms
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DOI：
10.1109/tra.2003.814518
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发表时间：
2003-08
期刊：
影响因子：
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通讯作者：
J. Wen;J. O’Brien
中科院分区：
文献类型：
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作者：
J. Wen;J. O’Brien
并联机构经常包含一种不稳定的奇点类型，而这种奇点在串行机构中是不存在的。当机构处于或接近这种奇点时，它就失去了在某些方向上抵消外力的能力。一般来说，确定并联机器人的不稳定奇异构型具有挑战性，通常通过使用精确的机构运动学解析模型对工作空间进行穷举搜索来解决。从几何角度研究平面和空间三足并联机构的奇异性确定问题。利用对被动关节速度的约束，导出了不稳定奇点存在的必要条件。使用这个条件，对于某些类型的平台可以找到某些奇异点。以一个六自由度加工中心为例，利用该方法发现了新的奇异位姿。
Parallel mechanisms frequently contain an unstable type of singularity that has no counterpart in serial mechanisms. When the mechanism is at or near this type of singularity, it loses the ability to counteract external forces in certain directions. The determination of unstable singular configurations in parallel robots is challenging in general, and is usually tackled via an exhaustive search of the workspace using an accurate analytical model of the mechanism kinematics. This paper considers the singularity determination problem from a geometric perspective for planar and spatial three-legged parallel mechanisms. By using the constraints on the passive joint velocities, we derive a necessary condition for the unstable singularities. Using this condition, certain singularities can be found for certain type of platforms. As an example, new singular poses are discovered using this approach for a six-degree-of-freedom machining center.