Implementation of tactile feedback by modifying the perceived friction

This paper describes implementation and initial evaluation of variable friction displays. We first analyse a device that comprises a stator of an ultrasonic motor supplied by only one channel. In this way, the stator does not induce any rotative movement but creates a slippery feeling on the stator's surface. Considering the range of frequency and amplitude needed to obtain this phenomenon, we interpret it as the squeeze film effect, which may be the dominant factor causing an impression of lubrication. This effect is thus able to decrease the friction coeffcient between the fingertip and the stator as a function of the vibration amplitude. Moreover, if we add a position sensor, we can create a textured surface by generating alternatively sliding and braking sensations by tuning the vibration amplitude of the wave. Then, based on the principle of the first device, another device is proposed in order to enable a free exploration of the surface, according to ergonomic requirements.