Investigating workspace and positional accuracy in 3 Degrees of Freedom planar manipulator under the link tolerances

Parallel manipulators are playing a significant role in robotic applications for the last few decades due to their merits over the serial manipulators. In this paper, kinematic analysis for the 3-RPR planar parallel manipulator having three degrees of freedom through a simple geometric approach is presented. The aim of the study presented here consist of two parts: improving the reachable workspace and investigating the positional error at platform due to link tolerance. The reachable workspace is estimated at various magnification ratios of manipulator at different position and orientation of tool point. The geometric approach is applied to calculate the workspace. The validation of kinematic results is carried out through the Computer-Aided Drafting (CAD) model. The positional error at platform and deviation in workspace due to tolerance on the link length are studied. The link tolerance results due to manufacturing and assembly constraints. The positional error for variation in link tolerance is presented. The proposed method is capable of quantification of maximum reachable workspace as well as worst error for the given tolerance value. The manipulator with highest possible accuracy over largest workspace area can be obtained applying proposed method as an optimized design.