Abstract-Most tactile displays currently built rely on pin-based arrays. However, this kind of tactile device is not always appropriate when we need to give the illusion of finely textured surfaces. In this paper, we describe the squeeze film effect between a plate and a finger, and we use this effect to design an ultrasonic tactile plate. The plate is actuated by piezoelectric ceramics. Ultrasonic vibrations are thus produced and are capable of generating the squeeze film effect. This enables us to simulate variable friction on the surface of the plate. In order to identify the squeeze film phenomenon, this study considers the case where a finger, with a planar bottom surface and with epidermal ridges, is placed on a rapidly vibrating plate. The overpressure is calculated and the result enables us to assess the relative coefficient of friction as a function of the vibration amplitude of the plate. Based on this principle, and using both analytic and FE method studies, and given ergonomic and stimulation (squeeze film) requirements, we show that it is possible to design a tactile plate which is capable of giving programmable tactile sensations. We conclude by comparing the results obtained from our simulations with experimental results.

In this paper, we investigate the use of friction based tactile displays for the simulation of finely textured surfaces, as such displays offer a promising way for the development of devices with co-located vision and tactile feedback. The resolution of the textures rendered with such devices and their matching to real textures have never been investigated. The paper first contributes to the evaluation of the texture resolution of friction based tactile displays. In a controlled experiment, we investigate the differential thresholds for square gratings simulated with a friction based tactile device by dynamic touch. Then we compare them to the differential thresholds of real square wave gratings. We found that the Weber fraction remains constant across the different spatial period at 9%, which is close to the Weber fraction found for corresponding real square gratings. This study inclines us to conclude that friction based tactile displays offers a realistic alternative to pin based arrays and can be used for co-located vision and tactile rendering. From the results of the experiment, we also give the design guidelines to improve the perception of textures on friction based tactile displays.

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