Coordination Control of Artificial Five Fingers With Multiple Degrees of Freedom and a Concept of Three Dimensional Stable Grasping

The flexible functions of a human five finger hand with a palm were studied from the viewpoint of force sensory manipulation, unlike the conventional viewpoint of position based manipulation. It was clear that more than half of human hand work is related to force sensory information. Based on this examination, the degree of freedom of an articulated finger hand is determined to realize such a flexible manipulation as a human hand, so that twenty five degrees of freedom are necessary for a hand with consideration of joints inside the palm which have not been taken into account previously. An artificial finger hand with twenty five degrees of freedom was built for experiments by employing a wire and spring mechanism. Finally, an evaluation concept of three dimensional grasping is presented as a crosssection method by calculating applied forces and moments in a plane virtually cut at arbitrary inclined angles around the center of a grasped object.