Transmission Index of Lower-Mobility Parallel Mechanism: Case Study on 3-PRS Mechanism

An extended definition of the transmission index based on the pressure angle was proposed. In order to enable evaluation of motion/force transmissibility and constrainability of parallel mechanism including lower-mobility/hybrid parallel mechanisms, pressure angle of a kinematic structure obtained by blocking all the actuated joints of the original mechanism was defined. In addition to this, an equivalent kinematic model of the original mechanism was introduced, in which the output link is supported by pure forces with the directions determined by the kinematic configuration of the mechanism. With these new ideas, a novel transmission index was proposed, and an illustrative example of 3-PRS mechanism was shown.Copyright © 2017 by ASME