Mode-shape compensator for improving robustness of manipulator mounted on flexible base

In this paper, the concept of the "robust arm configuration" is expanded by using a mode-shape compensator. This compensator improves the robustness of the arm configuration where the robustness is not high enough. The compensator consists of a constant gain matrix and acceleration of each joint. The structure is simple and easy to use. The design method for this mode-shaping matrix is presented, based on the previously proposed mode-shaping algorithm. Effect upon the manipulability is also examined. It suggests that inclining of the dynamic manipulability ellipsoid\´s principal axes by the compensator, resulting in changing the coupling rigid body dynamics, leads to the improvement of the robustness. The validity is confirmed by a numerical example and experiments. The experiments are performed with an experimental system consisting of a two-degree-of-freedom (DOF) planar manipulator and a 1-DOF flexible base. A high bandwidth positioning is realized with the obtained compensator.