Yongjae Yoo

Emotional responses of tactile icons: Effects of amplitude, frequency, duration, and envelope

This paper is concerned with emotional responses of tactile icons. Using three sets of tactile icons in which four physical parameters-amplitude, frequency, duration, and envelope-were systematically varied, we estimated their valence and arousal scores in a perceptual experiment with 24 participants. Results showed that the four parameters have clear relationships to the emotional responses of tactile icons. Our tactile icons spanned to a large region in the valence-arousal space, but they did not elicit very positive-relaxing or very negative-relaxing emotional responses. These findings provide the design guidelines of tactile icons that have desired emotional properties.

Consonance of Vibrotactile Chords

This paper is concerned with the perception of complex vibrotactile stimuli in which a few sinusoidal vibrations with different frequencies are superimposed. We begin with an observation that such vibrotactile signals are analogous to musical chords in which multiple notes are played simultaneously. A set of so-called “vibrotactile chords” are designed on the basis of musical chords, and their degrees of consonance (harmony) that participants perceive are evaluated through a perceptual experiment. Experimental results indicate that participants can reliably rate the degrees of consonance of vibrotactile chords and establish a well-defined function that relates the degree of consonance to the base and chordal frequency of a vibrotactile chord. These findings have direct implications for the design of complex vibrotactile signals that can be produced by current wideband actuators such as voice-coil, piezoelectric, and electroactive polymer actuators.

An Explorative Study on Crossmodal Congruence Between Visual and Tactile Icons Based on Emotional Responses

Tactile icons, brief tactile stimuli conveying abstract information, have found their use in various applications, and their use with visual elements is increasing on touchscreen user interfaces. However, effective design guidelines of tactile icons for crossmodal use have not been established. This paper addresses this problem by investigating the congruence between visual and tactile icons based on the hypothesis that emotional agreement between the icons improves congruence. The validity of this hypothesis was examined in three experiments. In Exp. I, we selected common visual icons and estimated their emotional responses using the circumplex model of affect. Tactile icons to be used as a pair were designed in Exp. II by varying their amplitude, frequency, and envelope (rhythm). Their emotional responses were also evaluated. In Exp. III, the congruence of 192 crossmodal icons made by combining the visual icons (8) and the tactile icons (24) was evaluated, and these congruence scores were compared with the valence and arousal scores of the two unimodal icons obtained in Exp. I and II. Experimental results suggested that the congruence of a crossmodal icon highly depends on the agreement in the emotional responses between its visual and tactile icons. This finding provides feasibility to the development of general design guidelines and heuristics for crossmodal icons that rely on the relationship between the emotional responses from the individual modalities. Our approach is expected to advance the current practice that associates the physical parameters between the different senses with better intuitiveness and simplicity.

An Initial Study on Pitch Correction Guidance for String Instruments Using Haptic Feedback

Learning to play a string instrument takes years of practice. Novice players even find it difficult to play correct pitches, and chromatic tuners that visualize the errors in the played pitches have long been used as an effective aid. However, chromatic tuners can detract users’ visual attention from more essential visual cues such as musical scores. As an alternative, we have been developing HapTune (Haptic Tuner), which conveys the pitch errors to the user using haptic feedback. In this paper, we present an initial design of HapTune that relies on spatiotemporal information coding using two vibrotactile actuators. We also verified that the vibrotactile stimuli provided by HapTune can be easily recognized by a user experiment.

Flexible and bendable vibrotactile actuator using electro-conductive polyurethane

The rapid development of nano technology and mobile devices has created high demand for shape changing mobile devices in order to provide users with more functions in less space and improved usability. However, the fundamental incompatibility between flexible displays and rigid actuator components has brought a huge barrier for commercialization of this technology. This paper presents a flexible and bendable vibrotactile actuator that can be easily applied to shape changing mobile devices. The proposed vibrotactile actuator is made with an electro-conductive membrane based on polyurethane, a base membrane, and an airgap. Actuation of the proposed actuator is controlled by a polarity of both charged membranes and the actuator performance can be modulated by increasing level of biased electric potential. A user experiment showed that the proposed actuator can provide vibrations with sufficient strength for perception.

A Soft Vibrotactile Actuator with Knitted PVC Gel Fabric

This paper proposes a soft vibrotactile actuator providing users with more functions in less space and improved usability in wearable and/or shape-changing devices. Previously, we have developed a soft vibrotactile actuator based on non-petroleum-based, eco-friendly, and electroactive plasticized poly-vinyl-chloride (PVC) gel formed as wave shape. One of the key differences between the electroactive PVC gel and the traditional electroactive polymers is that PVC gel does not need any stretchable electrodes. Although wave-shaped actuator improves the performance, it is possible that the ridges in PVC gel based actuators will be flayed from the body. In this paper, we introduce a new soft vibrotactile actuator using knitted PVC gel fabric. We measure the displacement of the actuator to quantitatively investigate the performance of the proposed actuator, and furthermore we performed a perceptual evaluation to compare the vibration strength of the proposed actuator and a rigid commercialized actuator. The results show that the proposed actuator can create vibration amplitude strong enough to stimulate human skin.

Objective quality prediction for haptic texture signal compression

Perceptual quality for media compression algorithms is traditionally evaluated through user studies. Such studies are time consuming, laborious and expensive, slowing down the development of new signal processing algorithms. To address this problem, a number of algorithmic quality prediction methodologies have been developed in the audio and video fields, something that is currently lacking in haptics research. In this paper, we present a novel method for predicting the perceptual quality degradation of compressed haptic texture signals. For this purpose, abstract perceptual features like Roughness, Brightness, etc. that capture the subjective experience of textures are exploited, in addition to low-level psychophysical models from the literature. As compared to the state-of-the-art, the presented prediction methodology shows an approximately 30% improvement in explaining the variance in the perceptual data.