A partial contact frictional force model for finger-surface interactions

Touching an object with our fingers yields frictional forces that allow us to perceive and explore its texture, shape, and other features. While the relevance of these frictional forces to sensory and motor function in the hand is well established, the way that they reflect the shape and texture of touched objects is not well understood. This lack of knowledge currently constraints the development of haptic rendering algorithms that rely on reproducing frictional forces to mimic the sensation of touching real surfaces. To address this, we created a low order contact mechanics inspired model that accounted for: disconnection between the finger and high relief features of the surfaces, and differences of pressure applied in the contact regions. The output of our model was compared to experimental frictional force measurements of bare-fingers sliding on structured surfaces. The results show high similarity between the measurements and the model output. The model presented can be used to predict frictional forces if the geometry of a touched surface is known together with the coefficient of friction of the untextured surface.