A Comparative Study of Physical and Haptic Exhibits in an Informal Learning Environment.

Virtual exhibits with haptic feedback offer greater flexibility in diversifying content and providing digital affordance, even at a lower cost, than physical exhibits. However, few studies addressed the value of such haptics-enabled educational systems in informal learning environments. In this study, we investigated the feasibility of a haptic exhibit as an alternative or supplement for a traditional physical exhibit in a science museum. We developed a two-degree-of-freedom cable-driven haptic device to simulate physical interactions on a large visual display. Choosing a seesaw-like physical exhibit available in a local museum, we designed and implemented a virtual lever simulation closely embodying the physics principles that the physical exhibit showcased. Then, we conducted an observational user study with children to compare the exhibit-visitor interaction behaviors, learning effects, and self-reported motivation and enjoyment between the physical and virtual exhibits. The results revealed that the visitors well-received and engaged with the haptic exhibit, instantiating its potential application in diverse learning settings. We hope that our research encourages further exploration of innovative haptic exhibits that enhance users' learning experiences across various environments.

Effects of Contact Force on Vibrotactile Perceived Intensity Across the Upper Body.

Full-body haptic suits, which can provide tactile sensations across the entire body, have been gaining popularity recently. The tightness of a suit to the user's body determines the contact force between the tactile actuators and the body. The contact force is likely to alter the intended perceptual effects, but relatively little is known about the extent of the alteration. Under this context, we present the effects of contact force on vibrotactile perceived intensity on three body parts: dorsal hand, upper arm, and lower back. To this end, we conducted three perceptual magnitude estimation experiments while controlling vibration amplitude, frequency, and contact force. The results show that increasing the contact force generally made the vibration stimuli feel stronger, while the specific behaviors were dependent on the body part and the experimental variables. Finally, we summarize the major findings and provide guidelines regarding contact force adjustment for effective full-body haptic rendering.

Multimodal Haptic Feedback for Virtual Collisions Combining Vibrotactile and Electrical Muscle Stimulation.

In this paper, we explore the effects of multimodal haptic feedback combining vibrotactile and electrical muscle stimulation (EMS) on expressing virtual collisions. We first present a wearable multimodal haptic device capable of generating both mechanical vibration and EMS stimuli. The two types of haptic stimulus are combined into a haptic rendering method that conveys improved virtual collision sensations. This multimodal rendering method highlights the strengths of each modality while compensating for mutual weaknesses. The multimodal rendering method is compared in subjective quality with two unimodal methods (vibration only and EMS only) by a user study. Experimental results demonstrate that our multimodal feedback method can elicit more realistic, enjoyable, expressive, and preferable user experiences.

Telemetry-Based Haptic Rendering for Racing Game Experience Improvement.

Many recent games, such as racing and flight games, open their game telemetry data to users by storing them in the local memory. Such telemetry data can provide useful information for haptic rendering, and this advantage has been exploited by the industry. This approach applies to any applications that export telemetry data in run time. The haptic rendering module operates as a separate process that accesses the telemetry data in parallel with the application. It is simple, efficient, and modular while retaining the application intact. We examine the approach's viability for user experience improvement by developing three telemetry-based haptic rendering algorithms for car racing games. They express the car engine response, collisions with external objects, and the road surface texture, respectively. Building a haptics-enabled driving platform, we conducted a user study comparing gaming experiences between our telemetry-based algorithms and conventional sound-to-tactile conversion algorithms. The results showed that the telemetry-based effects elicited better experiences than the sound-based effects.

Sound-to-Touch Crossmodal Pitch Matching for Short Sounds.

This article explores how to relate sound and touch in terms of their spectral characteristics based on crossmodal congruence. The context is the audio-to-tactile conversion of short sounds frequently used for user experience improvement across various applications. For each short sound, a single-frequency amplitude-modulated vibration is synthesized so that their intensive and temporal characteristics are very similar. It leaves the vibration frequency, which determines the tactile pitch, as the only variable. Each sound is paired with many vibrations of different frequencies. The congruence between sound and vibration is evaluated for 175 pairs (25 sounds × 7 vibration frequencies). This dataset is employed to estimate a functional relationship from the sound loudness spectrum of sound to the most harmonious vibration frequency. Finally, this sound-to-touch crossmodal pitch mapping function is evaluated using cross-validation. To our knowledge, this is the first attempt to find general rules for spectral matching between sound and touch.

Cable-Driven Haptic Interface With Movable Bases Achieving Maximum Workspace and Isotropic Force Exertion.

Haptic interactions play an essential role in education to enhance learning efficiency; however, haptic information for virtual educational content remains lacking. This article proposes a planar cable-driven haptic interface with movable bases that can display isotropic force feedback with maximum workspace extension on a commercial screen display. A generalized kinematic and static analysis of the cable-driven mechanism is derived by considering movable pulleys. Based on the analyses, a system including movable bases is designed and controlled to maximize the workspace subject to isotropic force exertion for the target screen area. The proposed system is evaluated experimentally as a haptic interface represented by the workspace, isotropic force-feedback range, bandwidth, Z-width, and user experiment. The results indicate that the proposed system can maximize workspace to the target rectangular area and exert isotropic force up to 94.0% of the theoretical computed one within the workspace.

Prediction of Specific Anxiety Symptoms and Virtual Reality Sickness Using In Situ Autonomic Physiological Signals During Virtual Reality Treatment in Patients With Social Anxiety Disorder: Mixed Methods Study.

BACKGROUND: Social anxiety disorder (SAD) is the fear of social situations where a person anticipates being evaluated negatively. Changes in autonomic response patterns are related to the expression of anxiety symptoms. Virtual reality (VR) sickness can inhibit VR experiences. OBJECTIVE: This study aimed to predict the severity of specific anxiety symptoms and VR sickness in patients with SAD, using machine learning based on in situ autonomic physiological signals (heart rate and galvanic skin response) during VR treatment sessions. METHODS: This study included 32 participants with SAD taking part in 6 VR sessions. During each VR session, the heart rate and galvanic skin response of all participants were measured in real time. We assessed specific anxiety symptoms using the Internalized Shame Scale (ISS) and the Post-Event Rumination Scale (PERS), and VR sickness using the Simulator Sickness Questionnaire (SSQ) during 4 VR sessions (#1, #2, #4, and #6). Logistic regression, random forest, and naïve Bayes classification classified and predicted the severity groups in the ISS, PERS, and SSQ subdomains based on in situ autonomic physiological signal data. RESULTS: The severity of SAD was predicted with 3 machine learning models. According to the F1 score, the highest prediction performance among each domain for severity was determined. The F1 score of the ISS mistake anxiety subdomain was 0.8421 using the logistic regression model, that of the PERS positive subdomain was 0.7619 using the naïve Bayes classifier, and that of total VR sickness was 0.7059 using the random forest model. CONCLUSIONS: This study could predict specific anxiety symptoms and VR sickness during VR intervention by autonomic physiological signals alone in real time. Machine learning models can predict the severe and nonsevere psychological states of individuals based on in situ physiological signal data during VR interventions for real-time interactive services. These models can support the diagnosis of specific anxiety symptoms and VR sickness with minimal participant bias. TRIAL REGISTRATION: Clinical Research Information Service KCT0003854; https://cris.nih.go.kr/cris/search/detailSearch.do/13508.

Motion Effects: Perceptual Space and Synthesis for Specific Perceptual Properties.

A motion effect, the vestibular stimulus generated by a moving chair, is crucial in improving user experiences in many virtual reality (VR) and entertainment applications. However, the perceptual characteristics of motion effects remain unexplored to a great extent. This paper constructs a perceptual space that accounts for many motion effects based on their perceptual distances and then demonstrates smooth-rough and irregular-regular as its two primary perceptual dimensions. An authoring space is constructed with these two pairs as the axes. We also present methods for synthesizing new motion effects with a specific property in the authoring space. The contributions of this work are with new insights into the perceptual characteristics of motion effects and the first design methods of motion effects achieving desired perceptual properties.

Data-Driven Rendering of Motion Effects for Walking Sensations in Different Gaits.

Motion effects are a vital component in 4D interactive applications, where special physical effects, such as motion, vibration, and wind, are provided with audiovisual stimuli. In 4D films and VR games, the scenes that show human locomotion appear frequently, and motion effects emphasizing such movements can enhance the viewers' immersive experiences. This paper proposes a data-driven framework for automatic generation of the motion effects that provide users with walking sensations. Measurements are made using the motion sensors attached to the human body during locomotion in different gaits, e.g., walking, running, and stumping. The captured data are processed and converted to multiple degree-of-freedom commands to a motion platform. We demonstrate that the data-driven motion commands can be represented in a greatly lower-dimensional space by principal component analysis. This finding leads to an algorithm for the synthesis of new motion commands that can elicit the target gait's walking sensations. The perceptual performance of our method is validated by two user studies. This work contributes to investigating the feasibility of mimicking walking sensations using a motion platform based on human locomotion data and developing an automatic generation algorithm of motion effects conveying the impressions of different gaits.

Perceived Intensity Model of Dual-Frequency Superimposed Vibration: Pythagorean Sum.

This paper presents a model for estimating the perceived intensity of a superimposed dual-frequency vibration from the perceived intensities of its two component vibrations. Based on the previous findings in the literature, we hypothesize that the three variables follow the Pythagorean relationship. Two psychophysical experiments were performed for verification with a wide range of single-frequency and superimposed vibrations applied to the fingertip. In Experiment I, we measured the perceived intensities of a large number of single-frequency vibrations and found a psychophysical magnitude function. Experiment II was designed based on the results of Experiment I in order to test the research hypothesis. For the 108 dual-frequency vibrations tested, the Pythagorean model showed 4.0% of average error in estimating the perceived intensity of a dual-frequency vibration from those of its two components. This model is robust and practical, and can be useful for any tactile interaction applications that make use of superimposed vibrations.

Length Perception Model for Handheld Controllers: The Effects of Diameter and Inertia.

Typical handheld controllers for interaction in virtual reality (VR) have fixed shapes and sizes, regardless of what visual objects they represent. Resolving this crossmodal incongruence with a shape-changing interface is our long-term goal. In this paper, we seek to find a length perception model that considers the moment of inertia (MOI) and diameter of a handheld object based on the concept of dynamic touch. Such models serve as a basis for computational algorithms for shape changing. We carried out two perceptual experiments. In Experiment 1, we measured the perceived lengths of 24 physical objects with different MOIs and diameters. Then we obtained a length perception model to reproduce the desired perceived length with a handheld controller. In Experiment 2, we validated our model in a crossmodal matching scenario, where a visual rod was matched to a haptic rod in terms of the perceived length. Our results contribute to understanding the relationship between the perceived length and physical properties of a handheld object and designing shape-changing algorithms to render equivalent visual and haptic sensory cues for length perception in VR.

Virtual Reality-Based Psychotherapy in Social Anxiety Disorder: fMRI Study Using a Self-Referential Task.

BACKGROUND: Although it has been well demonstrated that the efficacy of virtual reality therapy for social anxiety disorder is comparable to that of traditional cognitive behavioral therapy, little is known about the effect of virtual reality on pathological self-referential processes in individuals with social anxiety disorder. OBJECTIVE: We aimed to determine changes in self-referential processing and their neural mechanisms following virtual reality treatment. METHODS: We recruited participants with and without a primary diagnosis of social anxiety disorder to undergo clinical assessments (Social Phobia Scale and Post-Event Rumination Scale) and functional magnetic resonance imaging (fMRI) scans. Participants with social anxiety disorder received virtual reality-based exposure treatment for 6 sessions starting immediately after baseline testing. After the sixth session, participants with social anxiety disorder completed follow-up scans during which they were asked to judge whether a series of words (positive, negative, neutral) was relevant to them. RESULTS: Of 25 individuals with social anxiety disorder who participated in the study, 21 completed the sessions and follow-up; 22 control individuals also participated. There were no significant differences in age (P=.36), sex (P=.71), or handedness (P=.51) between the groups. Whole-brain analysis revealed that participants in the social anxiety disorder group had increased neural responses during positive self-referential processing in the medial temporal and frontal cortexes compared with those in the control group. Participants in the social anxiety disorder group also showed increased left insular activation and decreased right middle frontal gyrus activation during negative self-referential processing. After undergoing virtual reality-based therapy, overall symptoms of the participants with social anxiety disorder were reduced, and these participants exhibited greater activity in a brain regions responsible for self-referential and autobiographical memory processes while viewing positive words during postintervention fMRI scans. Interestingly, the greater the blood oxygen level dependent changes related to positive self-referential processing, the lower the tendency to ruminate on the negative events and the lower the social anxiety following the virtual reality session. Compared with that at baseline, higher activation was also found within broad somatosensory areas in individuals with social anxiety disorder during negative self-referential processing following virtual reality therapy. CONCLUSIONS: These fMRI findings might reflect the enhanced physiological and cognitive processing in individuals with social anxiety disorder in response to self-referential information. They also provide neural evidence of the effect of virtual reality exposure therapy on social anxiety and self-derogation.

Magnetorheological Fluid Haptic Shoes for Walking in VR.

In this article, present RealWalk, a pair of haptic shoes for HMD-based VR, designed to create realistic sensations of ground surface deformation, and texture using Magnetorheological fluid (MR fluid). RealWalk offers a novel interaction scheme through the physical interaction between the shoes, and the ground surfaces while walking in VR. Each shoe consists of two MR fluid actuators, an insole pressure sensor, and a foot position tracker. The MR fluid actuators are designed in the form of multi-stacked disc structure with a long flow path to maximize the flow resistance. With changing the magnetic field intensity in MR fluid actuators based on the ground material in the virtual scene, the viscosity of MR fluid is changed accordingly. When a user steps on the ground with the shoes, the two MR fluid actuators are pressed down, creating a variety of ground material deformation such as snow, mud, and dry sand. We built an interactive VR application, and compared RealWalk with vibrotactile-based haptic shoes in four different VR scenes: grass, sand, mud, and snow. We report that, compared to vibrotactile-haptic shoes, RealWalk provides higher ratings in all scenes for discrimination, realism, and satisfaction. We also report qualitative user feedback for their experiences.

Effectiveness of a Participatory and Interactive Virtual Reality Intervention in Patients With Social Anxiety Disorder: Longitudinal Questionnaire Study.

BACKGROUND: Social anxiety disorder (SAD) is characterized by excessive fear of negative evaluation and humiliation in social interactions and situations. Virtual reality (VR) treatment is a promising intervention option for SAD. OBJECTIVE: The purpose of this study was to create a participatory and interactive VR intervention for SAD. Treatment progress, including the severity of symptoms and the cognitive and emotional aspects of SAD, was analyzed to evaluate the effectiveness of the intervention. METHODS: In total, 32 individuals with SAD and 34 healthy control participants were enrolled in the study through advertisements for online bulletin boards at universities. A VR intervention was designed consisting of three stages (introduction, core, and finishing) and three difficulty levels (easy, medium, and hard) that could be selected by the participants. The core stage was the exposure intervention in which participants engaged in social situations. The effectiveness of treatment was assessed through Beck Anxiety inventory (BAI), State-Trait Anxiety Inventory (STAI), Internalized Shame Scale (ISS), Post-Event Rumination Scale (PERS), Social Phobia Scale (SPS), Social Interaction Anxiety Scale (SIAS), Brief-Fear of Negative Evaluation Scale (BFNE), and Liebowitz Social Anxiety Scale (LSAS). RESULTS: In the SAD group, scores on the BAI (F=4.616, P=.009), STAI-Trait (F=4.670, P=.004), ISS (F=6.924, P=.001), PERS-negative (F=1.008, P<.001), SPS (F=8.456, P<.001), BFNE (F=6.117, P=.004), KSAD (F=13.259, P<.001), and LSAS (F=4.103, P=.009) significantly improved over the treatment process. Compared with the healthy control group before treatment, the SAD group showed significantly higher scores on all scales (P<.001), and these significant differences persisted even after treatment (P<.001). In the comparison between the VR treatment responder and nonresponder subgroups, there was no significant difference across the course of the VR session. CONCLUSIONS: These findings indicated that a participatory and interactive VR intervention had a significant effect on alleviation of the clinical symptoms of SAD, confirming the usefulness of VR for the treatment of SAD. VR treatment is expected to be one of various beneficial therapeutic approaches in the future. TRIAL REGISTRATION: Clinical Research Information Service (CRIS) KCT0003854; https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=13508.

A Review of Surface Haptics: Enabling Tactile Effects on Touch Surfaces.

In this article, we review the current technology underlying surface haptics that converts passive touch surfaces to active ones (machine haptics), our perception of tactile stimuli displayed through active touch surfaces (human haptics), their potential applications (human-machine interaction), and finally, the challenges ahead of us in making them available through commercial systems. This article primarily covers the tactile interactions of human fingers or hands with surface-haptics displays by focusing on the three most popular actuation methods: vibrotactile, electrostatic, and ultrasonic.

Data-Driven Texture Modeling and Rendering on Electrovibration Display.

With the introduction of variable friction displays, either based on ultrasonic or electrovibration technology, new possibilities have emerged in haptic texture rendering on flat surfaces. In this work, we propose a data-driven method for realistic texture rendering on an electrovibration display. We first describe a motorized linear tribometer designed to collect lateral frictional forces from textured surfaces under various scanning velocities and normal forces. We then propose an inverse dynamics model of the display to describe its output-input relationship using nonlinear autoregressive neural networks with external input. Forces resulting from applying a pseudo-random binary signal to the display are used to train each network under the given experimental condition. In addition, we propose a two-step interpolation scheme to estimate actuation signals for arbitrary conditions under which no prior data have been collected. A comparison between real and virtual forces in the frequency domain shows promising results for recreating virtual textures similar to the real ones, also revealing the capabilities and limitations of the proposed method. We also conducted a human user study to compare the performance of our neural-network-based method with that of a record-and-playback method. The results showed that the similarity between the real and virtual textures generated by our approach was significantly higher.

Effects of Contact Force and Vibration Frequency on Vibrotactile Sensitivity During Active Touch.

Humans require precise force control to execute fine manual tasks, which is generally facilitated to a great extent by providing adequate feedback. Currently, such dexterous manual tasks can be an input source of computing. To design appropriate vibrotactile stimuli for manual tasks, it is essential to quantify human vibrotactile sensitivity over a large range of contact forces. In this paper, we report the psychophysical detection thresholds for vibrotactile stimuli measured for five pressing forces that cover the range of forces encountered during ordinary manual tasks. The experimental results showed stark contrasts between stimulus frequencies, depending on actively exerted pressing force. The detection thresholds for 40 Hz stimuli first increased and then decreased as the pressing force increased, but the detection threshold for 250 Hz stimuli generally decreased as the force increased. These results have immediate consequences on the design of vibrotactile feedback for manual tasks in many applications of tangible interaction, tele-operation, and VR.

Visuo-Haptic-Based Multimodal Feedback Virtual Reality Solution to Improve Anxiety Symptoms: A Proof-of-Concept Study.

With proper guidance, virtual reality (VR) can provide psychiatric therapeutic strategies within a simulated environment. The visuo-haptic-based multimodal feedback VR solution has been developed to improve anxiety symptoms through immersive experience and feedback. A proof-of-concept study was performed to investigate this VR solution. Nine subjects recently diagnosed with panic disorder were recruited, and seven of them eventually completed the trial. Two VR sessions were provided to each subject. Depression, anxiety, and VR sickness were evaluated before and after each session. Although there was no significant effect of the VR sessions on psychiatric symptoms, we could observe a trend of improvement in depression, anxiety, and VR sickness. The VR solution was effective in relieving subjective anxiety, especially in panic disorder without comorbidity. VR sickness decreased over time. This study is a new proof-of-concept trial to evaluate the therapeutic effect of VR solutions on anxiety symptoms using visuo-haptic-based multimodal feedback simultaneously.

Haptic Enchanters: Attachable and Detachable Vibrotactile Modules and Their Advantages.

This paper showcases attachable/detachable haptic modules, nicknamed haptic enchanters, by presenting their conceptual prototypes and quantifying their information transmission capacity. Haptic enchanters can be attached to ordinary devices and wearables to endow them with the ability of creating programmable haptic stimuli, thereby transforming them to effective haptic communication devices. In particular, our prototype enchanters are designed to localize vibrotactile stimulation to the neighborhood of attachment site, and this spatial isolation allows for effective spatiotemporal information delivery using multiple enchanters. We demonstrate that haptic enchanters enable very high capacity of information transfer (4.55-7.06 bits) for spatiotemporal vibration sequences rendered with two, three, and four enchanters. We also assert that haptic enchanters provide better user experiences by using location-enabled feedback in a game application than the whole-device feedback. These results instantiate the performance of haptic enchanters as effective and convenient communication accessories and their potential for applications.

Correction to "Pysics-based vibrotactile feedback library for collision events".

The authors of "A Physics-Based Vibrotactile Feedback Library for Collision Events" which appeared in the July-September 2017 issue of this journal [ibid., vol. 10, no. 3, pp. 325-337, Jul.-Sep. 2017] would like to update their Acknowledgments section to say: The authors thank Jong-Rak Park for his discussion on the physics of multi-body collision and vibration. This work was supported by an MSIP/IITP grant (No. 16ZC1300), an IITP grant (No. 2017-0-00179), and an NRF grant (No. NRF-2017R1A2B4008144), all funded by the Korean government. Seungmoon Choi is the corresponding author.