Instantaneous stiffness analysis and simulation for hexapod machines

This paper introduces a derivation and simulation technique of instantaneous stiffness for 6–6 Stewart platforms (hexapods) with the interest in increasing machining accuracy of the new type hexapod machines. It clearly expresses that high non-linearity of motions and driving forces of the parallel mechanisms results in the asymmetric stiffness matrix, and the change in geometry and the loading are the significant factors to the asymmetry. Also, based on the theoretical calculation the simulations for the hexapod machining cycles numerically and illustratively present the instantaneous stiffnesses and deflections of the end-effector (tool tip). Therefore, this work can provide a theoretical principle and an application tool for the anticipation and the evaluation for hexapod machining performance, design optimisation and machining accuracy control, etc.