Investigation of parasitic motion in 3-RRS parallel manipulator

Abstract

This paper investigates the Parasitic Motion (PaMo) in a 3-Degree of Freedom (DoF) 3-RRS Spatial Parallel Manipulator (SPM) for its different link proportions. The position kinematic analysis of the manipulator is addressed initially. The PaMo is investigated and quantified as the percentage of Reachable Workspace (RW) for each link proportion at the tip of an End-Effector (EE), which is attached at the centroid of the moving platform. The PaMo which happens in the constrained DoF is an unwanted motion, and this entire process allows to know the total occupancy of PaMo in comparison to RW for each link proportion. The results are depicted with the aid of 3D plots of the reachable work-volume and the volume of PaMo for each link proportion. In order to evaluate the performance measure, a performance index called as the parasitic motion index ( PaMoI) is proposed. The PaMoI variation pattern is also discussed based on the obtained results. The conclusions are drawn at the end based on this investigation that also identify the provisions to minimize the PaMo.