The parasitic motion has been widely recognized as the major drawback of the parallel mechanism. Therefore a class of 2R1T PMs (parallel mechanism) without parasitic motion has been synthesized. However, these PMs can only rotate around two axes in sequential order. It decreases the performance of the balancing adjustment of the end-effector. In this paper, a family of 2R1T PMs without parasitic motion was reconstructed by using a novel method based on the remarkable properties of rotational bifurcation mechanisms, which can rotate in sequential order. Furthermore, some PMs rotating around two continuous axes in an arbitrary order are established by adding single joints. Taking the practicability of these structures into consideration, the workspace of 3-PRPS PM was analyzed as an example. Moreover, this study explores the practical application of the PMs without parasitic motion in developing balance mechanisms in rough-terrain fire-fighting robots. During the climbing process, the tank is adjusted to be parallel to the horizontal plane in real-time. It is proved that this kind of structure realizes continuous rotation around two rotation axes on the premise of no parasitic motion.

寄生运动已被广泛认为是并联机构的主要缺点。因此合成了一类无寄生运动的2R1T PM（并联机构）。但是，这些 PM 只能按顺序围绕两个轴旋转。它降低了末端执行器平衡调整的性能。在本文中，基于旋转分叉机制的显着特性，可以按顺序旋转，使用一种新方法重建了一个没有寄生运动的 2R1T PMs 系列。此外，通过添加单个关节来建立一些以任意顺序围绕两个连续轴旋转的 PM。考虑到这些结构的实用性，3 -PR P的工作空间以 S PM 为例进行分析。此外，本研究探讨了无寄生运动的 PM 在开发崎岖地形消防机器人平衡机构中的实际应用。在爬升过程中，实时调整水箱与水平面平行。实践证明，这种结构在无寄生运动的前提下，实现了围绕两个旋转轴的连续旋转。