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Thesis

French

ID: <

10670/1.t6bvao

>

Where these data come from
Study of the reflection and absorption of ultrasonic waves by the finger : application to haptic surfaces

Abstract

Touchscreens have pervaded our lives and became the human/computer of choice. However, its utilization needs high visual attention contrary to the physical world that we experience. To address this lack, haptic surfaces propose to produce tactile stimuli directly onto the user’s fingertip.To generate these stimuli, a promising technique consists of modulating fingertip friction on the active surface. The variation of this force, opposed to the fingertip motion, generates an illusion of touching a textured surface. The method used here is based on the control of the amplitude modulation of ultrasonic waves in real-time to variate the fingertip friction.The effect of these ultrasonic waves on friction is a complex and variable phenomenon. This work proposes a method to measure and control in a closed loop this force that would overcome its variations. To understand the underlying phenomenon of wave/fingertip interaction a multi-scale contact model has been made. It includes the non-linear dynamics which links two-time scales: the one of the ultrasonic vibration (\approx20\mathrm{\mu s}) and its effect on friction (\approx1\mathrm{ms}). Interestingly, this model helps extract the contact state and so its frictional resistance simply with the measure of the plate vibration. This is done without using another sensor than the ultrasonic actuator already needed for the friction modulation. Consequently, this method is ready to be used in haptic interfaces. Also, with the possibility to assess friction even before sliding occurs, a new way to create tactile stimuli is brought to enhance the realism of tactile illusions on haptic surfaces.

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