空间单环RPSC机构的运动和奇异分析

单环机构又称单闭链机构,这类机构运动巧妙,在诸多领域有着广泛应用。另外,在工程实际中还常常在开链机构中加入局部闭链以改善动力学性能,增加结构刚度等。介绍一种能够实现垂直Darboux运动(Vertical Darboux motion,VDM)的空间单环RPSC机构,运用螺旋理论对其约束及运动性质进行分析。通过对锁住其驱动关节后的等价机构进行约束分析,确定了该机构的一类特殊驱动奇异,并借助相对直观的几何方法对RPSC机构中存在的这种奇异位形做进一步解释与说明。对机构中RPS分支的主要特点进行概括,并由特殊到一般地提出了一类具有相似特性的单环机构。

Motion and Singularity Analysis of a Spatial Single-loop RPSC Mechanism

Single-loop mechanisms can realize various kinds of motion and have wide applications. Closed chains are often put in the open-chain mechanisms as partial structure to improve the dynamic performance and increase the structure stiffness, which are widely used in engineering practice. A spatial single-loop RPSC mechanism which can realize vertical Darboux motion is introduced and its constraint and motion properties are analyzed based on screw theory. A special class of actuation singularity can be found by analyzing the constraints of this RPSC mechanism after the actuated joint is locked. A more intuitionistic geometric interpretation of this kind of singular configuration is given with the comparison of a similar planar mechanism. The key characteristics of the RPS limb in the mechanism are summarized, on the basis of which a class of more general single-loop mechanisms with similar properties are proposed.