“…A number of performance indices, such as workspace, dexterity indices, condition number, transmission angle, motion/force transmission indices, et al, have been proposed and applied to the performance evaluation of parallel manipulators [19,[21][22][23][24][25]. As we know, the traditional transmission/pressure angle, which was originally introduced for evaluating the force transmission quality of single-loop linkages, is generally no longer applicable to evaluate the motion/force transmissibility of spatial parallel mechanisms, but for the parallel mechanism proposed in this paper, the two identical RPU limbs are in the same plane and axes of the two revolute joints are parallel to each other, and the axis of revolute joint of the SPR limb is parallel to u axis.…”