Handling and grasp control with additional grasping point for dexterous manipulation of cylindrical tool

This study aims to construct a handling and grasp control method by multi-fingered robot hand with soft skin for the precision operation of cylindrical tools. We believe that the key to the improvement of the accuracy of the tool operation is to use an additional grasping point to reduce the tool´s posture fluctuation derived from the external force exerted at the tool nib. We focus two factors that cause the tool´s posture fluctuation. One is the rotation movement of the tool around the axis between two contacts by finger-tips. The other one is the deflection of the soft skin. We propose the effective allocation of the addition grasping point from the view point of the reduction of the tool´s posture fluctuation. Our control architecture is a customized combination of resolved motion rate control and hybrid control which maintains stable grasping and handles the tool along with the desired trajectory of the tool nib. It is validated through the physical tests using the actual multi-fingered robot hand that the accuracy of the tool nib trajectory is improved by proposed control method.