In tactile interaction, a phantom sensation refers to an illusion felt on the skin between two distant points at which vibrations are applied. It can improve the perceptual spatial resolution of tactile stimulation with a few tactors. All phantom sensations reported in the literature act on the skin or out of the body, but no such reports exist for those eliciting sensations penetrating the body. This paper addresses tactile phantom sensations in which two vibration actuators on the dorsal and palmar sides of the hand present an illusion of vibration passing through the hand. We also demonstrate similar tactile illusions for the torso. For optimal design, we conducted user studies while varying vibration frequency, envelope function, stimulus duration, and penetrating direction. Based on the results, we present design guidelines on penetrating phantom sensations for its use in immersive virtual reality applications.
Natural navigation in VR is challenging due to spatial limitations. While Teleportation enables navigation within very small physical spaces and without causing motion sickness symptoms, it may reduce the feeling of presence and spacial awareness. Redirected walking (RDW), in contrast, allows users to naturally walk while staying inside a finite, but still very large, physical space. We present Telewalk, a novel locomotion approach that combines curvature and translation gains known from RDW research in a perceivable way. This combination enables Telewalk to be applied even within a physical space of 3m x 3m. Utilizing the head rotation as input device enables directional changes without any physical turns to keep the user always on an optimal circular path inside the real world while freely walking inside the virtual one. In a user study we found that even though motion sickness susceptible participants reported respective symptoms, Telewalk did result in stronger feelings of presence and immersion and was seen as more natural then Teleportation.
Humans rely on categories to mentally organize and understand sets of complex objects. One such set, haptic devices, has myriad technical attributes that affect user experience in complex ways. Seeking an effective navigation structure for a large online collection, we elicited expert mental categories for grounded force-feedback haptic devices: 18 experts (9 device creators, 9 interaction designers) reviewed, grouped, and described 75 devices according to their similarity in a custom card-sorting study. From the resulting quantitative and qualitative data, we identify prominent patterns of tagging versus binning, and we report 6 uber-attributes that the experts used to group the devices, favoring affordances over device specifications. Finally, we derive 7 device categories and 9 subcategories that reflect the imperfect yet semantic nature of the expert mental models. We visualize these device categories and similarities in the online haptic collection, and we offer insights for studying expert understanding of other human-centered technology.
We propose generating two-dimensional skin stretch feedback on the user's legs. Skin stretch is useful cutaneous feedback to induce the perception of virtual textures and illusory forces and to deliver directional cues. This feedback has been applied to the head, body, and upper limbs to simulate rich physical properties in virtual reality (VR). However, how to expand the benefit of skin stretch feedback and apply it to the lower limbs, remains to be explored. Our first two psychophysical studies examined the minimum changes in skin stretch distance and stretch angle that are perceivable by participants. We then designed and implemented Gaiters, a pair of ungrounded, leg-worn devices, each of which is able to generate multiple two-dimensional skin stretches on the skin of the user's leg. With Gaiters, we conducted an exploratory study to understand participants' experiences when coupling skin stretch patterns with various lower limb actions. The results indicate that rich haptic experiences can be created by our prototype. Finally, a user evaluation indicates that participants enjoyed the experiences when using Gaiters and considered skin stretch as compelling haptic feedback on the legs.
Force feedback from damped oscillation is a common effect in our daily lives, especially when shaking an elastic object, an object hanging or containing other stuff, or a container with liquid, e.g., casting with a fishing pole or wine-swirling. Such a force, affected by complex physical variations and collisions, is difficult to properly simulate using current force feedback methods. Therefore, we propose ElastOscillation on a virtual reality (VR) controller to provide 3D multilevel force feedback for damped oscillation to enhance VR experiences. ElastOscillation consists of a proxy, six elastic bands and DC motors. It leverages the motors to control the bands' elasticity to restrain the movement of the proxy, which is connected with the bands. Therefore, when users shake the ElastOscillation device, the proxy shakes or moves in corresponding ranges of movement. The users then perceive the force from oscillation at different levels. In addition, elastic force from the bands further reinforces the oscillation force feedback. We conducted a force perception study to understand users' distinguishability for perceiving oscillation forces in 1D and 2D movement, respectively. Based on the results, we performed a VR experience study to show that the force feedback provided by ElastOscillation enhances VR realism.