Personalising Vibrotactile Displays through Perceptual Sensitivity Adjustment

Haptic displays are commonly limited to transmitting a discrete set of tactile motives. In this paper, we explore the transmission of real-valued information through vibrotactile displays. We simulate spatial continuity with three perceptual models commonly used to create phantom sensations: the linear, logarithmic and power model. We show that these generic models lead to limited decoding precision, and propose a method for model personalization adjusting to idiosyncratic and spatial variations in perceptual sensitivity. We evaluate this approach using two haptic display layouts: circular, worn around the wrist and the upper arm, and straight, worn along the forearm. Results of a user study measuring continuous value decoding precision show that users were able to decode continuous values with relatively high accuracy (4.4% mean error), circular layouts performed particularly well, and personalisation through sensitivity adjustment increased decoding precision

Touching is believing: creating illusions and feeling of embodiment with mid-air haptic technology

Over the last two decades, the sense of touch has received new attention from the scientific community.Several haptic devices have been developed to address the complexity of the sense of touch, the latest addition being mid-air (contactless) haptic technology. An interesting series of previous research has suggested an easier way to tackle the complexity of designing convincing tactile sensations by exploiting tactile illusions. Tactile illusions rely on perceptual shortcuts based on the psychophysics of the tactile receptors. Currently, studies exploring the perceptual space of mid-air haptics and its applicability in the tactile illusions field are still limited in number. This thesis aims to contribute to the field of Human-Computer Interaction (HCI) by investigating the perceptual design space of ultrasonic mid-air haptics technology. Specifically, in a first set of three studies, we investigate the absolute thresholds (minimal amount of a property of astimulus that a user can detect) for control points (CP) at different frequencies on the hand and arm (Study 1). Then we investigate the optimal sampling rate needed to drive the device in an optimal fashion and its relationship with shape size (Study 2). Next, we apply a new technique to increase users’ performance in a shape discrimination task (Study 3). In Study 4, we start the exploration of a tactile illusion of movement using contact touch and later, we apply a similar procedure to investigate the feasibility of creating a tactile illusion of movement between the two non-interconnected hands by using mid-air touch (Study 5). Finally, in Study 6, we explore our sense of touch in VR, while providing an illusion of rain drops through mid-air haptics, to recreate a virtual hand illusion (VHI) to explore the boundaries of our sense of embodiment. Therefore, the contribution of this work is threefold: a) we contribute by adding new knowledge on the psychophysical space for mid-air haptics, b) we test the potential to create realistic tactile sensations by exploiting tactile illusions with mid-air haptic technology, and c) we demonstrate how tactile illusions mediated by mid-air haptics can convey a sense of embodiment in VR environments

The snake effect: Investigation of a novel haptic illusion

This study was based on tactual illusions produced by vibrotactile units. A novel haptic effect based on amplitude modulation was developed, called here the ”snake effect”, which consists on a continuous motion that is smooth, wavy and creepy. Two studies were conducted in order to parameterize this novel haptic effect aiming to: (1) find the fundamental parameters that allow the snake effect to happen in a straight line, (2) assess if the parameters can be implemented for curved trajectories after being combined with funneling, as seen for apparent motion in literature. Study 1 used a 2x6 haptic display in the dorsal part of the forearm, consisted of a pilot and a main study. Participants were asked to rate how the effect was being perceived in an adaptive method. It was found that the effect has a lower and an upper SOA (stimulus onset asynchrony) boundaries and that lower stimulus durations cause a decrease in smoothness and creepiness. It was also found that not every amplitude modulation works to produce the snake effect, and that the best options among the ones investigated are Sine, Sine-Squared and Gaussian modulation types. Study 2 used a 4x4 haptic display in the left forearm and asked participants to draw the motion and direction of movement they perceived in a sheet of paper. In this study, it was found that the direction of movement is easier to tell than the trajectory itself. Also, that the beginning and ending of the motion are harder to feel than the middle of the movement. These findings provide relevant parameters to apply this new haptic effect based on vibrotactile actuators in current and future haptic displays

Creating an illusion of movement between the hands using mid-air touch

Apparent tactile motion (ATM) has been shown to occur across many contiguous parts of the body, such as fingers, forearms and the back. More recently, the illusion has also been elicited on non-contiguous part of the body, such as from one hand to the other when interconnected or not interconnected by an object in between the hands. Here we explore the reproducibility of the intermanual tactile illusion of movement between two free hands by employing mid-air tactile stimulation. We investigate the optimal parameters to generate a continuous and smooth motion using two arrays of ultrasound speakers, and two stimulation techniques (i.e. static vs. dynamic focal point). In the first experiment, we investigate the occurrence of the illusion when using a static focal point, and we define a perceptive model. In the second experiment, we examine the illusion using a dynamic focal point, defining a second perceptive model. Finally, we discuss the differences between the two techniques

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Representing Interpersonal Touch Directions by Tactile Apparent Motion Using Smart Bracelets

We present a novel haptic interaction to vibro-tactually connect an interpersonal touch using bracelet devices. A pair of bracelet devices identifies the user who is actively touching and the other who is passively touched, defining the direction as being from the former to the latter. By controlling the vibrational feedback, the pair induces a tactile apparent motion representing the direction between two hands. The bracelets are comprised of our developed interpersonal body area network module, an acceleration sensor, and a vibrator. The devices communicate with each other through electrical current flowing along the hands to identify the direction by sharing accelerations just before a touch and to synchronize the feedback in less than ten milliseconds. Experiment 1 demonstrates that the vibration propagated from a bracelet device to the wearer\u27s hand is perceivable by another. Experiment 2 determines sets of optimal actuation parameters, stimulus onset asynchrony, and duration of vibration to induce the tactile apparent motion based on a psychophysical approach. In addition, vibration propagation between hands is observed. Experiment 3 demonstrates the capability of the developed device to present the haptic interaction

The role of the right temporoparietal junction in perceptual conflict: detection or resolution?

The right temporoparietal junction (rTPJ) is a polysensory cortical area that plays a key role in perception and awareness. Neuroimaging evidence shows activation of rTPJ in intersensory and sensorimotor conflict situations, but it remains unclear whether this activity reflects detection or resolution of such conflicts. To address this question, we manipulated the relationship between touch and vision using the so-called mirror-box illusion. Participants' hands lay on either side of a mirror, which occluded their left hand and reflected their right hand, but created the illusion that they were looking directly at their left hand. The experimenter simultaneously touched either the middle (D3) or the ring finger (D4) of each hand. Participants judged, which finger was touched on their occluded left hand. The visual stimulus corresponding to the touch on the right hand was therefore either congruent (same finger as touch) or incongruent (different finger from touch) with the task-relevant touch on the left hand. Single-pulse transcranial magnetic stimulation (TMS) was delivered to the rTPJ immediately after touch. Accuracy in localizing the left touch was worse for D4 than for D3, particularly when visual stimulation was incongruent. However, following TMS, accuracy improved selectively for D4 in incongruent trials, suggesting that the effects of the conflicting visual information were reduced. These findings suggest a role of rTPJ in detecting, rather than resolving, intersensory conflict