Toward a Platform of Human-Like Fingertip Model in Haptic Environment for Studying Sliding Tactile Mechanism

Human fingertip and its derivatives in robotics possess an inhomogeneous structure with skin, tissue, bone, and nail; which causes troublesome for construction of a precise model that can represent almost mechanical characteristics, especially during sliding motion. Commonly, models in a virtual haptic environment are frictionless, thus attempts to display tactile sensations are still remained unsolved. We have proposed a Beam Bundle Model for modeling of a human fingertip during pushing and sliding action with friction, especially stickto-slip transition, to overcome mentioned issues. In order to construct its three-dimensional non-homogeneous structure, we took sequential series of magnetic resonant images, which bring consecutive cross-sectional layers of the human fingertip with distribution of skin, tissue, bone, and nail. Simulation results show a twofold aspect. Firstly, it can generate not only normal force distribution caused by pushing, but also response of friction force during sliding. Secondly, and more interestingly, the model dynamically produces localized displacement phenomenon on the contact area during stick-to-slip phase, which indicates how slippage erodes the contact area before the total slippage of the fingertip occurs. This research helps to assess the sliding process of the human fingertip, including how and when the slippage occurs on the contact surface. This model may also act as a platform for studying tactile perception of the fingertip, as well as being a virtual environment for haptic interfaces.