ReferenceAuthors and Affiliations:
Olivier Bau, Disney Research, Pittsburgh 4615 Forbes Avenue Pittsburgh, PA and In|Situ|, INRIA Saclay, Building 490, Université Paris-Sud, 91405 Orsay, France
Ivan Poupyrev,Disney Research, Pittsburgh 4615 Forbes Avenue Pittsburgh, PA
Ali Israr, Disney Research, Pittsburgh 4615 Forbes Avenue Pittsburgh, PA
Chris Harrison,Human-Computer Interaction Institute Carnegie Mellon University and Disney Research, Pittsburgh ,PA
Presentation:UIST’10, October 3–6, 2010, New York, New York, USA.
SummaryHypothesis
In this paper, authors hypothesize an alternative approach for creating tactile interfaces for touch surfaces that does not use any form of mechanical actuation. Instead, the proposed technique exploits the principle of electrovibration, which allows user to create a broad range of tactile sensations by controlling electrostatic friction between an instrumented touch surface and the user’s fingers. When combined with an input-capable interactive display, it enables a wide variety of interactions augmented with tactile feedback.
Contents
The paper 1)presents the principles and implementation of electrovibration-based tactile feedback for touch surfaces. 2) reports the results of three controlled psychophysical experiments and a subjective user evaluation, which describe and characterize users’ perception of this technology. 3) analyzes and compares the design to traditional mechanical vibrotactile displays and highlight their relative advantages and disadvantages. 4) explores the interaction design space.
Methods
A study was conducted with subjective evaluations to better understand how users interpret the tactile sensations produced by TeslaTouch.Ten participants felt four TeslaTouch textures produced by four frequency-amplitude combinations: 80 Hz and 400 Hz each at 80 and 115 Vpp. Then they were asked to fill 3 different set of questionnaires about the quality data and constraints of tactile feedback.
To determine the absolute detection threshold participants were provided with a divided screen with tactile feedback on one part and asked to determine which part provided tactile feedback. The screen was provided with a varied level of voltage for 12 reversals.
To determine the The frequency and amplitude discrimination threshold a study was done similar to the previous one.Three tactile stimuli were presented one after another. Participants were requested to identify test stimuli, which was different from the two identical reference stimuli.The session was terminated after 12 reversals at the smaller step size.They were requested to wear an electrostatic ground strap on their dominant forearm and slide the pad of their index finger on the interactive surface.
Results
Low frequency stimuli were perceived as rougher and sticky compared to high frequencies which were smoother and waxy. They were often likened to “wood” and “bumpy leather”, versus “paper” and “a painted wall” for higher frequency stimuli.An increase of amplitude increased perceived smoothness of tactile sensations.At low frequencies (e.g. 80 Hz), an increase in stimuli amplitude heightened the perception of stickiness,viscous fluid or rubber.There was a statistically significant effect of frequency on the threshold levels (F(4,36)=12.8;
p<0.001), indicating that the threshold levels depend on the stimulus frequency. The ANOVA analysis failed to show significant effect of frequency on the amplitude JND (F(4,24)=0.43; p=0.79), icdicating that the JND of 1.16 dB remains constant across all tested frequencies,The effect of frequency on JND was statistically significant (F(4,24)=6.46; p<0.01). Post-hoc comparison divided the frequency range in to two groups: 80 Hz, 120 Hz, 180 Hz and 270 Hz, 400 Hz. The average JNDs were 25% and 12% for lower and higher frequency groups, respectively.
Discussion
I was excited to read about this research because being a user of a touch based device, I always wished for a tactile feedback form the screen. This research provide a great deal of mathematical analysis for different design constraints and thresholds to design better systems. If designers want to create two distinct tactile sensations, they must make sure that the amplitude of voltages for each sensation are at least 1.16 dB apart for the user to be able to differentiate them. Similar considerations also apply for frequency of stimuli.The research has a very wide range of applications.It will be a widely acclaimed research if now it can be applied on touch based smartphones and tablets.
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