Tactile Roughness Perception of Virtual Gratings by Electrovibration

Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with 10 participants to investigate the effect of spatial period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants' finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with spatial period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force ($dF_t/dt$) as a function of spatial period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.Comment: Manuscript received June 25, 2019; revised November 15, 2019; accepted December 11, 201

Active-Proprioceptive-Vibrotactile and Passive-Vibrotactile Haptics for Navigation

Navigation is a complex activity and an enabling skill that humans take for granted. It is vital for humans as it fosters spatial awareness, enables exploration, facilitates efficient travel, ensures safety, supports daily activities, promotes cognitive development, and provides a sense of independence. Humans have created tools for diverse activities, including navigation. Usually, these tools for navigation are vision-based, but for situations where visual channels are obstructed, unavailable, or are to be complemented for immersion or multi-tasking, touch-based tools exist. These touch-based tools or devices are called haptic displays. Many different types of haptic displays are employed by a range of fields from telesurgery to education and navigation. In the context of navigation, certain classes of haptic displays are more popular than others, for example, passive multi-element vibrotactile haptic displays, such as haptic belts. However, certain other classes of haptic displays, such as active proprioceptive vibrotactile and passive single-element vibrotactile, may be better suited for certain practical situations and may prove to be more effective and intuitive for navigational tasks than a popular option, such as a haptic belt. However, these other classes have not been evaluated and cross-compared in the context of navigation. This research project aims to contribute towards the understanding and, consequently, the improvement of designs and user experience of navigational haptic displays by thoroughly evaluating and cross-comparing the effectiveness and intuitiveness of three classes of haptic display (passive single-element vibrotactile; passive multi-element vibrotactile; and various active proprioceptive vibrotactile) for navigation. Evaluation and cross-comparisons take into account quantitative measures, for example, accuracy, response time, number of repeats taken, experienced mental workload, and perceived usability, as well as qualitative feedback collected through informal interviews during the testing of the prototypes. Results show that the passive single-element vibrotactile and active proprioceptive vibrotactile classes can be used as effective and intuitive navigational displays. Furthermore, results shed light on the multifaceted nature of haptic displays and their impact on user performance, preferences, and experiences. Quantitative findings related to performance combined with qualitative findings emphasise that one size does not fit all, and a tailored approach is necessary to address the varying needs and preferences of users