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EETE JULAUG 2014

Visibly flat but feeling rough Researchers from the University of Electro-Communications (Japan) jointly with company EyePlusPlus Inc. demonstrated what they call a tactile vision substitution system, dubbed HamsaTouch. The electro-tactile display features tiny electrodes on the upper side (where you would put the palm of your hand) tied to as many optical sensors on the other side of the tablet. When fitted to the LCD screen of a smartphone which is used as the camera and image processor for extracting objects and landscape contour information, the optical sensing side translates the contrast information into tactile information onto the palm-facing side. Spaced about 3mm apart, the tiny electrodes send 300V at 5mA, modulated in frequency to create a tactile feel onto the skin. One could easily identify lines, moving contours, or swipe their fingers to “read” the contrasted image in a Braille-like fashion. A sponsor of the event, Finnish company Senseg offers a transparent coating The optical sensing side of the HamsaTouch electro-tactile display. they call the Senseg Tixel, together with a driver chip to manage electrical signals sent to the Tixel surface. By modulating the signal, the company’s Tixel delivers a sophisticated sensation of touch and texture using an electrostatic field (Coloumb’s force creating an attraction between bodies of different electrical charges). When dragging a finger across the surface, the so-called electrovibration Conceptual illustration of Senseg’s Tixel haptic surface through electro-vibration. can create varying degrees of friction, making the fingers slip more or less as if they encountered ridges or asperities which can complement the visual cues (sand paper background, rough stone, buttons etc... Senseg has recently secured $6 million in a Series B round of funding led by NXP Semiconductors NV, but it has yet to see its technology in a commercial product. Another interesting paper presented by researchers from the Korea Science Academy of KAIST illustrated a surface display enabling realistic 3D haptic rendering with both kinesthetic feedback (position, force, orientation) and tactile feedback (contact pressure, slip, vibration). Altering real-world textures for quick prototype perceptual changes. KAIST’s on-screen 3D haptic rendering uses both mechanical vibration and electro-vibration for 2D textures and 3D features respectively. In a fully transparent layered approach, the researchers combine electrovibration (the use of a frequency-modulated electrostatic force through a capacitive gap) with mechanical Eurohaptics 2014 vibration distributed uniformly on the screen’s surface. While 3D geometric features can be represented by adjusting the lateral friction forces using electrovibration, tactile patterns are generated through mechanical vibration to convey 2D texture information at the surface of the geometric features. Here, both the mechanical vibration and the electrovibration can be driven independently to simulate all touch-aspects of real objects, on a flat screen. For some, altering flat screen surfaces is not enough. In a paper titled “Diminished Haptics: Towards Digital Transformation of Real World Textures”, researchers from the University of Tokyo developed a method for altering real-world textures, for example, from paper-like to metal-like, from wood-like to paper-like. The researchers use a 28kHz transducer coupled to the object whose texture should be altered. By controlling the amplitude of the input signal, the researchers are able to determine the levitation height of the finger relative to the material’s surface, based on the squeeze effect. To approach the real thing, they use high resolution real world textures (collected using a three-axis accelerometer) instead of synthesized data. The idea is that various textures could be mapped to an existing manufactured prototype, to reflect CAD changes during the product elaboration. By tracking the finger position and with an image projection showing different textures across the surface, the researchers also envisage the simulation of multiple patches of different textures on the same surface. As a first pre-processing step, the researchers reduce the original real-world texture of the object. In a second pass, they aim to rewrite the texture by applying ultrasonic vibrations at adequate frequencies. Haptic screens bulging with information At this year’s EuroHaptics, several research labs were presenting their attempts to make mechanically re-configurable haptic interfaces, with pistons and actuators protruding from the screen’s surface. Because these implementations are typically bulkier and non-transparent, they would not qualify for integration into smartphones and tablets, but may be convincing as enhanced table top keyboards. 10 Electronic Engineering Times Europe July/August 2014 www.electronics-eetimes.com


EETE JULAUG 2014
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