Geometry constraint and branch motion evolution of 3-pup parallel mechanisms with bifurcated motion
Geometry constraint and branch motion evolution of 3-pup parallel mechanisms with bifurcated motion
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DOI：
10.1016/j.mechmachtheory.2012.09.011
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发表时间：
2013-03
影响因子：
5.2
通讯作者：
D. Gan;J. Dai
中科院分区：
文献类型：
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作者：
D. Gan;J. Dai
本文研究了一类3-PUP并联机构的有趣的分叉运动特性，这类机构按平台上两个转动关节之间的夹角分类，称为平台角。基于回路闭合方程中嵌入的基本几何约束，系统地揭示了机构在两个垂直方向上的分叉转动，用螺旋理论研究了具有原点位置的两个分支机构的全运动。当平台转角小于或大于π时，所有3-PUP并联机构的一个分支均为纯转动，另一个分支为变节距±h的螺旋运动。一种特殊情况是平台角度等于π，分支螺杆运动变为螺距为0的纯旋转。此外，平台在包括具有约束奇异性的原点位置在内的所有配置下都具有解耦的公共平移。确定了用于分支运动操作和约束奇异性避免的驱动方案，并解析地获得了正运动学和逆运动学。
This paper investigates the interesting bifurcated motion property of a class of 3-PUP parallel mechanisms which are classified by the angle between two prismatic joints on the platform called platform angle. Based on the basic geometric constraint embedded in the loop closure equation, bifurcated rotations in two orthogonal directions are revealed systematically, indicating the full mobility of the mechanisms in two branches with a home position which is investigated using screw theory. While all the 3-PUP parallel mechanisms have a pure rotation in one branch, the other branch is a screw motion with inconstant pitch±h when the platform angle is less or larger than π. A special case is that the platform angle equals to π and the branch screw motion becomes a pure rotation with pitch 0. Furthermore, the platforms possess a decoupled common translation at all configurations including the home position with constraint singularity. Actuation scheme is identified for the branch motion operation and constraint singularity avoidance with both forward and inverse kinematics obtained analytically.