Antagonistic Stiffness Optimization of Redundantly Actuated Parallel Manipulators in a Predefined Workspace

An optimization procedure regarding shape of usable workspace and antagonistic stiffness is developed for a redundantly actuated parallel manipulator. The kinematic parameters such as configuration of the mechanism and length of linkages are optimized to maximize and equal out antagonistic stiffness of the redundantly actuated manipulator when the shape of usable workspace is given as a rectangle. The proposed procedure is verified by simulation and experiment with a 2-DOF planar manipulator. In the experiment, the principal axes of displacements of ellipses are measured when the corresponding external forces are imposed on the end-effector. The simulation and experimental results show that the proposed procedure is valid for designing the redundantly actuated parallel manipulator with maximum antagonistic stiffness.