T-PaD: Tactile Pattern Display through Variable Friction Reduction

In this paper we discuss the theory, design and construction of a haptic display for creating texture sensations through variations in surface friction. Ultrasonic frequency, low amplitude vibrations between two flat plates have been shown to create a squeeze film of air between the two plate surfaces thereby reducing the friction (Salbu, 1964; Weisendanger, 2001). We show that a reduction of friction will also occur between a human finger and a vibrating plate. Thus, a vibrating plate can serve as a haptic interface. The amplitude of vibration can also be correlated to the amount of friction reduction between the plate and the finger. Varying the surface friction between the finger and the haptic interface is a way of indirectly controlling shear forces on the finger during active exploration. Using finger position and velocity feedback on the display allows for the creation of spatial texture sensations