Overall Objectives
Scientific Foundations
Application Domains
New Results
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Section: New Results

Improvement of a tactile stimulator, and its connectivity

Participants : Frédéric Giraud, Betty Lemaire-Semail, Romuald Vanbelleghem, Michel Amberg.

The tactile stimulator which is born in the framework of Alcove's project has shown good performances for gratings simulation. To reach such level of performance, an accurate position sensor is used to locate a user's fingertip on the device. Other improvements have been added in order to reduce bulk size of the power electronics which supply power to the tactile stimulator. A specific design was achieved. At the end, a complete stimulator was built and fits in a demo-suitcase. This work allowed to easily carry the stimulator for presentation to a large audience, and was part of the demo session of the 2009 Haptic Symposium in Salt Lake City.

We designed then a program running on a host computer to control the tactile stimulator. This software converts a picture into tactile stimuli. We paid attention to build a software which helps to create new experiences easily. The solution found was to store a catalogue of pictures inside the target DSP and in the host computer. To create an experience, the user just has to choose a of set of pictures arranged in sequence.

Further work was carried out in order to shrink stimulator's size (figure 5 . The final goal is to build a stand-alone tactile stimulator, which could be used as a touchpad. To achieve that, we reduced the size of the position sensor. We used optical force sensor to deduce fingertip's position when a user touch the device. Best result were found if a specific algorithm were used to remove sensor's non linearity. In spite of the large amount of software resources, a poor resolution could be achieved only. But this solution os outstanding in terms of final size of the position sensor. We also tried to increase the device's efficiency. To do so, we optimized the substrate thickness, the piezo ceramic used and the vibration wavelength. Finally, we could build a prototype which power consumption is below 2 watts, which is consistent with power consumption of items plugged into an USB port of a computer.

Figure 5. a) Fingertip's position with an optical force sensor before (green) and after (blue) linearization. b) The optimize tactile stimulator . c) Power consumption (W) as a function of the tactile stimuli (W) for the original tactile plate (black) and the optimized one (red). Other results are presented.


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