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Summary: Representing tangential motion between objects and the skin using tactile displays enables humans to manipulate virtual objects and recognize their surface properties. To design effective tactile stimuli that accurately represent motion, it is important to understand how humans perceive tactile motion based on spatiotemporal features, an area that remains relatively unexplored. This study elucidates the spatiotemporal features that influence the perceived speed of tactile motion represented by a tactile display with discrete stimulation points. The findings show that the average spatial spacing between stimulation points affects the perceived speed, even though the average spatial spacing does not vary with the speed itself, but rather varies with the stimulation point layout of the tactile display. No significant effects from other features were observed on the perceived speed. The results suggest that perceived speed can be controlled by considering the average spatial spacing during tactile stimulus design.

Previously, tactile displays focused on the tactile presentation of the surface of a virtual object. In contrast, this study attempts to provide a tactile feeling on the space inside a virtual object when fingers penetrate it. Our previous study developed a finger-mounted pin-array display with the smallest pin pitch, representing the highest spatial resolution. Using the display, we attempt to present the tactile impression of “Rough,” “Grainy,” and “Sparse” which correspond to Japanese onomatopoeia of “Zara-Zara,” “Tsubu-Tsubu,” or “Chiri-Chiri” with simple patterned stimuli arranged in 3D space. A series of experiments were conducted in this study to determine the following: (1) the stimuli that can provide users with different tactile impressions inside objects and (2) the effect of tactile display spatial resolution on the recognition of tactile impressions inside objects. The results clarified that we could provide three different tactile impressions in space with certain stimuli configurations. Besides, the results demonstrated that participants recognized the tactile impression better with a larger spatial resolution configuration of the device. This study reveals a new field of tactile presentation, that is, tactile presentation inside an object.

Many activities can be carried out in virtual reality environments, and at present, reproducing the activity of eating or drinking is one developing field. Virtual eating or drinking can be divided into two types: those with food in the mouth and those without placing food in the mouth. Many studies have focused on changing the taste, size, and texture of food when eating or drinking, but few studies have focused on recreating the sensation of eating or drinking without actually placing food in the mouth. One of the challenges in virtually reproducing eating or drinking without the use of food or drink is how the sensation of swallowing is recreated in the esophagus. Herein we show Grutio, a device for recreating the sensation of swallowing by causing skin deformations that are the same as those during actual swallowing. When participants were asked to compare the sensation of drinking water with the recreated sensation, 66% of the participants had a stable pattern of swallowing sensations over the three-day experiment. participants who did not have a stable pattern also felt swallowing at least three times, and all participants were able to feel swallowing. The hardness and viscosity of the virtual swallowed food could be changed by adjusting the rate of skin deformation. The system allowed most users to virtually feel the sensation of swallowing through calibration. Although there were individual differences, the results of this study suggest that applying skin deformations externally to the neck can reproduce swallowing sensations internally.

The design productivity of fine-tuning for vibrotactile stimuli becomes important as consumer devices equipped with vibrotactile actuators will become wide-spread. The fine-tuned vibrotactile stimuli output by vibrotactile actuators allows the end-users to feel the surface of the virtual material. However, there is no suitable tool for fine-tuning while there are existing tools suitable for initial designing. In this paper, we test whether we can use GAN (Generative Adversarial Network)-based vibrotactile signal generator at the tuning phase. The generator provides a material-level interface to designers. Designers can define any intermediate materials among pre-defined 108 materials and obtain corresponding intermediate signals that the generator generates. We showed the applicability of the generator to the fine-tuning of vibrotactile signals from the viewpoints of principal component analysis and a user test.

The presentation of virtual object shapes using a finger-mounted pin-array haptic display is one of the major topics of research in haptics. If this can be realized, the operability of objects and immersive feeling in the virtual space will be improved. For now, previous studies showed that shape recognition performance using such a pin-array display was far inferior from the performance in the real world using a real object. We considered that both the density of contact points and coverage areas are essential to improve the recognition performance. However, the size of the actuator that pushes each pin was a constraint, and the previously developed display could not have a large contact density and coverage area. This study proposes a novel design of a finger-mounted pin-array display that works around the constraint. We adopted a pneumatic drive because the pneumatic actuator, or air cylinder, can be a simple structure and can be arranged in a dense array. Our developed finger-mounted display has a higher contact point density and a larger coverage area than any other previously developed devices. It covered more than 4 times larger area on fingerpad with denser pin arrangements. An experiment to evaluate the recognition performance with the device was conducted. Participants discriminated 10 kinds of 2D patterned alphabet shapes with only haptic information. The result showed participants could recognize the ten kinds of 2D patterned shape with 93.8% accuracy. Though our participants' task in the experiment was more difficult, the accuracy was better than previous studies. It suggests the effect of the higher density and the larger size of the coverage.

This article reports the first psychological evidence that the combination of oscillating optic flow and synchronous foot vibration evokes a walking sensation. In this study, we first captured a walker’s first-person-view scenes with footstep timings. Participants observed the naturally oscillating scenes on a head-mounted display with vibrations on their feet and rated walking-related sensations using a Visual Analogue Scale. They perceived stronger sensations of self-motion, walking, leg action, and telepresence from the oscillating visual flow with foot vibrations than with randomized-timing vibrations or without vibrations. The artificial delay of foot vibrations with respect to the scenes diminished the walking-related sensations. These results suggest that the oscillating visual scenes and synchronous foot vibrations are effective for creating virtual walking sensations.

The sports industry and researchers work on improving spectators’ enjoyment to influence their consumption behavior. Many studies evaluated the variables impacting on enjoyment, but they did not consider the recent new technologies popularization. This study aims to update these considerations and reevaluate enjoyment parameters’ impact, considering display technologies use. Most of the previous research works identified identification to the players and teams as the most powerful enjoyment variable, but considering our survey results, participants cared more about the game understanding parameter, and manifested the wish to improve it via a display.