Local Minimum of Elastic Potential Energy on Hemispherical Soft Fingertip

This paper proposes a new contact deformation model between a hemispherical soft fingertip and an object. First, we develop our proposed contact model, in which an elastic potential energy is formulated. Second, we show that the elastic potential energy due to the deformation of the soft fingertip is proportional to the cube of the maximum displacement of that fingertip. Also, it is firstly shown that the elastic force and the potential energy are functions of two variables: the maximum displacement and the orientation angle of the contact object. The most important point is that the potential energy of the fingertip have a local minimum when the object contacts with the soft fingertip keeping a vertical direction. Finally, we show that the local minimum of the elastic potential energy also appears in experiments.