Analogous to the null space map, this work proposes a “unit space map” to identify the generalized transmission wrench screw, which plays an important role in the general method determining the multi-parameter instantaneous screw of lower-mobility parallel mechanism which can be expressed as the linear combination of several proper basis screws of a twist screw system. Based on the fundamental equation, the screw rolling between moving and fixed axodes is decomposed into the linear superposition of several coupling screw rollings associated with several pairs of moving and fixed envelope axodes of proper basis screw, respectively. Moreover, several numerical examples of SP+SPR+SPU and 3-UPU parallel mechanisms are presented to verify the linear superposition, unit space map, and the method determining the multi-parameter instantaneous screw. Finally, the graph of the velocity-ratio parameter is employed to analyze the influence of input velocities on the axode shape of the 3-UPU PM when it undergoes two motion patterns: constant velocity-ratio and variable velocity-ratio.

类似于零空间图，这项工作提出了一个“单位空间图”来识别广义的变速扳手螺钉，这在确定可表达为下流动性并联机构的多参数瞬时螺钉的通用方法中起着重要的作用。作为拧紧螺钉系统的几个适当基础螺钉的线性组合。基于基本方程式，动和固定轴之间的螺杆滚动被分解为分别与适当的基础螺钉的几对动和固定包络双轴相关联的多个耦合螺杆滚动的线性叠加。此外，给出了几个SP + SPR + SPU和3-UPU并联机构的数值示例，以验证线性叠加，单位空间图以及确定多参数瞬时螺杆的方法。