Kinematics of a 3RRR compliant micro-motion stage: Modelling accuracy improvement

Abstract

The paper focuses on the kinematics modelling of a 3RRR compliant micro-motion stage. This 3RRR micro-motion stage is a monolithic compliant mechanism and is designed using flexure hinges. This compliant micro-motion stage has a closed-loop parallel structure configuration which provides better stiffness and accuracycompared to serial structures. A kinematic model of this stage was derived previously by the authors using thepseudo-rigid-body model and the loop-closure theory accordingly. An analytical constant Jacobian matrix,which is derived using the kinematic model, is used to generate a workspace of the 3RRR micro-motion stage.This analytical workspace is much larger than a FEA (finite element analysis) workspace and an experimentalworkspace. This suggests that there is a loss of motion in the micro-motion stage not being modelled in theanalytical kinematic model. Therefore, FEA is carried out to investigate the rotational and the translationalmotions of the flexure hinges as well as the motions of the stage. The results of the FEA are used to improvethe accuracy of the analytical model. The improved model effectively predicts the workspace area of the stage.