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Cross-cutting Challenges - Theme 2: Interactive Discussions
Cross-cutting Challenges
California East
Capturing and Reproducing Tactile Texture at the Fingertip
Michael Wiertlewski
(Aix-Marseille University, France)
Abstract: The micrometer-scale features at the surface of an object accounts for an important part of the tactile perception of the material properties and in particular of what is defined as the texture. Running our fingers on the surface asperities creates a unique vibratory signal which can be interpreted by the somatosensory system as leather, fine grain wood or a sanded coating. Tactile texture accounts for an important part of the realism of simulated surfaces, and it has been a long-time goal of the haptic community to produce accurate virtual analogs. This interactive discussion will introduce some of the work that has been done to capture, process and reproduce realistic textures. Recording the interaction of a finger sliding onto a surface can be done by observing the minute fluctuations of the friction force that are produced during the tactile exploration. With the help of a custom-built force sensor, able to resolve micro-Newton variation, we observed that the relationship between the micro-geometry and the force fluctuations is not trivial and can vary as a function of space and time. A simple sinusoidal grating produces vibrations that vary from trial to trial and contains energy not only at the fundamental frequency but also on all observable harmonics. In addition to a complex signal, a rich background noise which amplitudes decays with the inverse of the frequency. The amplitude and the decay of the background noise is influenced by the nature of the surface and relates to the pleasantness of a particular texture. More complex structured textures exhibit frequency-spectra that are modulated as a function of the user’s position, leading to formant-like structures that seems to inform about the finish of the surface. This highly detailed force profiles can be reproduced using high-fidelity rendering devices by modulating the lateral deformation of the finger pad according to the speed of exploration of the user. Slow movement will produce low frequency oscillation while rapid stroke will increase the pitch of the same pattern. The production of a sensation congruent with the user exploration, creates a sensation similar to touching the original texture. Psychophysical experiments show that participants are able to use the spatially distributed force profile to discriminate and identify virtual texture with their real counterpart. This discussion will go over the intricacy of the development of high fidelity apparatuses to capture the finger-surface interaction and use the signals to produces realistic sensations.

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Time stamp: 2019-03-22T00:49:06+01:00