Performance evaluation of parallel manipulators: Motion/force transmissibility and its index

Performance evaluation is one of most important issues in the analysis and design of parallel manipulators. As the counterparts of serial robots, parallel manipulators are mostly good at motion/force transmission but not dexterous manipulation. In this study, a generalized transmission index that can evaluate the motion/force transmissibility of fully parallel manipulators is proposed based on the virtual coefficient. The transmission index defined here is frame-free and is relative to singularity. By giving a specified and significant value, the index can be used to identify a good transmission workspace (GTW), where the parallel manipulator is not only good at motion/force transmission, but is also far away from its singularity. To introduce the analysis method and the frame-free index, the transmission performance analysis of two parallel manipulators is presented. The analysis method of motion/force transmissibility and the proposed index are expected to be applied to the analysis and kinematic optimal design of fully parallel manipulators.