Characterization of Ultrasound Tactile Display

Traditional haptic interfaces require physical contact between the haptic device and the user. An elegant and novel solution is to provide contactless tactile stimulation via airborne acoustic radiation pressure. However, the characteristics of contactles

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Abstract. Traditional haptic interfaces require physical contact between the haptic device and the user. An elegant and novel solution is to provide contactless tactile stimulation via airborne acoustic radiation pressure. However, the characteristics of contactless tactile displays are not well studied in the literature. In this paper, we study the characteristics of the ultrasonic tactile display as a haptic interface. In particular, we examine the effects of increasing the number of ultrasound transducers on four characteristics, namely the maximum producible force, the workspace, the workspace resolution, and the robustness of the simulation. Three rectangular-shaped 2D array configurations are considered: single-tile (10 × 10 transducers), two-tiles (10 × 20 transducers), and four-tiles (20 × 20 transducers). Results show that the maximum producible force remains almost constant as the number of tiles increases, whereas the elevation at which these maxima are generated increases. The workspace increases along the xy-plane as the number of tiles increase almost linearly, however, the elevation of the workspace remains almost the same. Finally, we found that the robustness of tactile display decreases as the number of tiles increases.

Keywords: Haptic interfaces display

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Ultrasound transducer array

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Tactile

Introduction

Haptic-based ultrasonic stimulation relies on an airborne acoustic phased array for giving tactile sensation at the human skin [5]. Dalecki et al. demonstrated that tactile sensations could be evoked from the ultrasound radiated on the skin in water [4]. Subsequent research by Shinoda and colleagues expanded further on this concept, using 2D array of ultrasonic transducers, to produce one focal point on the submerged hand [14]. The study suggested using ultrasound at 40 kHz; higher frequency resulted in higher energy attenuation and degradation in spatial resolution of focusing. Shinoda and colleagues studied airborne ultrasound tactile stimulation to enhance the quality of the tactile stimulation and integrate it with visual display. A feasibility study with 91 transducers was conducted to generate a fixed focal point [16]. To animate the focal point and produce higher tactile forces c Springer International Publishing Switzerland 2016  F. Bello et al. (Eds.): EuroHaptics 2016, Part I, LNCS 9774, pp. 78–89, 2016. DOI: 10.1007/978-3-319-42321-0 8

Characterization of Ultrasound Tactile Display

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of around 16 mN (20 mm spatial resolution and 1 kHz vibrations), a subsequent work extended the tactile display to 324 transducers [12]. Experiments showed that users were able to discriminate tactile stimulation movement direction. A further development with 2,241 transducers offered a much larger workspace of 1 m3 and an improved temporal resolution of 0.5 ms [8]. The system was then integrated with a touch screen to enable noncontact blind touch interaction by adding tactile feedback for notifying the finger location [23,24]. A recent study by Inoue et al. produced a spatially stationary ha