Contribution
Longitudinal Ultrasonic Waves for Haptic Perception
* Presenting author
Abstract:
The development of haptic feedback in mobile devices such as smartphones and tablets as well as in virtual environments has been rapidly growing in the recent years. Amongst other haptic technologies, ultrasonic friction haptics offers the advantage of a noiseless system and is suitable for large touch sensitive surfaces. It is based on the effect, that ultrasonic vibrations reduce friction while a finger is moving over the surface. Current approaches use ultrasonic bending waves to generate tactile effects on flat surfaces. The feeling of a surface structure is thereby created by switching a standing bending wave on and off. An adverse side effect of using bending waves is the radiation of ultrasound. The resulting high airborne sound pressure levels can cause interference effects in other acoustic systems and pose a potential health risk to users. As an alternative, the use of longitudinal waves for ultrasonic friction haptics will be considered. Comparable wavelengths are to be generated, which leads to significantly higher operating frequencies. The feasibility of using longitudinal waves has been proven experimentally and the main factors influencing friction reduction are highlighted. The results of a subject study showed that haptic perception directly depends on the relative change in friction.