Vibrotactile Displays Research Articles

A Vibrotactile Belt for Measuring Vibrotactile Acuities on the Human Torso Using Coin Motors

Accurate measurement of the vibrotactile acuities of the human torso is the key to designing effective torso-worn vibrotactile displays for healthcare applications such as navigation aids for visually impaired persons. Although efforts have been made to measure vibrotactile acuities, there remains a lack of systematic studies addressing the spatial, temporal, and intensity-related aspects of vibrotactile sensitivity on the human torso. In this work, a torso-worn vibrotactile belt consisting of two crossed coin motor arrays was designed and a psychophysical study was carried out to measure the spatial, temporal, and intensity-related vibrotactile acuities of a set of human subjects wearing the designed belt. The objective parameters of vibrational intensity and the timing latency of the coin motor were also determined before measuring the vibrotactile acuities. The experimental results indicated that the tested coin motor was able to generate a median number of five and six available just-noticeable differences in intensity and duration, respectively. Among the four parameters of vibrational intensity, the perceived intensity was the most relevant to vibrational displacement. The spatial acuities measured as the degree of two-point spatial thresholds (TPTs) showed less individual difference than the distance TPTs. The results from the current work provide valuable guidance for the design of a comfortable torso-worn vibrotactile display using coin motors.

The Impact of Meaningful Vibrotactile Displays on User Preferences Across Age Groups in Automated Driving

Automated vehicles may enhance the quality of life by empowering individuals and promoting independent mobility, especially for older adults. However, takeovers are still required occasionally. To ensure a safe transition during the takeover, meaningful tactile displays as takeover requests could be a good option to improve takeover efficiency. Previous studies have examined the effects of tactile takeover request more from an objective perspective, however, subjective evaluations that could reach larger and more diverse sample sizes have not been extensively conducted yet. Therefore, the goal of this study was to investigate drivers of different age groups (younger and older adults) on their preference of vibrotactile displays, varied in information formats (instructional and informative) and locations (seat back and seat pan), on a large population scale ( n = 353) through a national survey. The results indicated a preference for informative patterns over instructional patterns and displays on the seat back over the seat pan. Also, a higher level of perceived urgency was noted in older participants (age ≥ 65) compared with younger participants. These findings may inform the design of next-generation tactile interfaces in automated systems.

A Comparative Investigation of Cutaneous Rabbit and Funneling Tactile Illusions for Implementation in Vibrotactile Displays

A Comparative Investigation of Cutaneous Rabbit and Funneling Tactile Illusions for Implementation in Vibrotactile Displays

Supplemental Material for Examining the Efficacy of Vibrotactile Displays for Monitoring Patient Vital Signs: Six Laboratory Studies of Change Detection and State Identification

Supplemental Material for Examining the Efficacy of Vibrotactile Displays for Monitoring Patient Vital Signs: Six Laboratory Studies of Change Detection and State Identification

Vibrotactile display design: Quantifying the importance of age and various factors on reaction times.

Numerous factors affect reaction times to vibrotactile cues. Therefore, it is important to consider the relative magnitudes of these time delays when designing vibrotactile displays for real-time applications. The objectives of this study were to quantify reaction times to typical vibrotactile stimuli parameters through direct comparison within a single experimental setting, and to determine the relative importance of these factors on reaction times. Young (n = 10, 21.9 ± 1.3 yrs) and older adults (n = 13, 69.4 ± 5.0 yrs) performed simple reaction time tasks by responding to vibrotactile stimuli using a thumb trigger while frequency, location, auditory cues, number of tactors in the same location, and tactor type were varied. Participants also performed a secondary task in a subset of the trials. The factors investigated in this study affected reaction times by 20–300 ms (reaction time findings are noted in parentheses) depending on the specific stimuli condition. In general, auditory cues generated by the tactors (<20 ms), vibration frequency (<20 ms), number of tactors in the same location (<30 ms) and tactor type (<50 ms) had relatively small effects on reaction times, while stimulus location (20–120 ms) and secondary cognitive task (>130 ms) had relatively large effects. Factors affected young and older adults’ reaction times in a similar manner, but with different magnitudes. These findings can inform the development of vibrotactile displays by enabling designers to directly compare the relative effects of key factors on reaction times.

Evaluation of Vibrotactile Warning Systems for Supporting Hazard Awareness and Safety of Distracted Pedestrians

OCCUPATIONAL APPLICATIONS We evaluated prototype vibrotactile warning systems for supporting pedestrian awareness of approaching hazards. Mobile devices are used by people on the move for leisure and essential task activities in many work domains. While they can be a source of distraction, they also offer sensing capabilities and computing power that can detect and direct attention to approaching hazards. By presenting vibrations from devices distributed around the body, as if embedded in personal protective equipment, these systems can quickly and intuitively convey the risk of collision with a hazard and its approach direction to guide avoidance maneuvers. Results of a simulator study suggest these vibratory warnings improve response time to and avoidance of true hazards, especially when conducting distracting secondary tasks. Future developments of such systems offer promise for increasing safety for distracted pedestrians, as well as for workers in domains that impose high demand on visual and/or auditory senses.TECHNICAL ABSTRACT Background: Mobile devices can be considered essential tools for many daily activities, though there are potential safety risks associated with distraction when hazards are present (e.g., pedestrians near heavily-trafficked roads or workers in industrial settings). Yet, these devices offer onboard sensor and computing capabilities that can be leveraged to improve safety by capturing and guiding attention to approaching hazards. In domains that heavily load vision and audition, vibrotactile cues can reliably support hazard awareness and provide guidance for hazard avoidance. Purpose: We evaluated the effectiveness of prototype vibrotactile warning systems in enhancing recognition of hazards and appropriate avoidance maneuvers. Methods: Participants (n = 27) walked on a treadmill, following a virtual pedestrian path, under varied distracting task conditions. Vehicles, pedestrians, and bicyclists approached from multiple directions, representing “true” (would result in a collision if not avoided) and “false” hazards. Performance was compared with and without each of two experimental displays that presented directional vibrations via devices affixed to suspenders and to an industrial helmet. Signal detection theory and response time analyses were used to determine how well each display supported detection and avoidance of true hazards under each task condition. Results: Each vibrotactile display (suspenders- or helmet-mounted) significantly improved hazard detection in terms of hit rates and response times. Task conditions that included texting and (to a lesser extent) music negatively impacted performance, but decrements were smaller when vibrotactile displays were used. Although conditions involving the vibrotactile displays did not differ significantly in response times or signal detection theory measures, subjective ratings suggested the suspenders display was more comfortable and preferred overall. Conclusions: Vibrotactile displays improved hazard detection and avoidance; however, sensitivity in distinguishing true and false hazards could be improved. Advanced versions of these warning systems offer potential to improve hazard awareness and safety for distracted pedestrians and workers.

Vibrotactile Displays: A Survey With a View on Highly Automated Driving

The task of car driving is automated to an ever greater extent. In the foreseeable future, drivers will no longer be required to touch the steering wheel and pedals and could engage in non-driving tasks such as working or resting. Vibrotactile displays have the potential to grab the attention of the driver when the automation reaches its functional limits and the driver has to take over control. The aim of the present literature survey is to outline the key physiological and psychophysical aspects of vibrotactile sensation and to provide recommendations and relevant research questions regarding the use of vibrotactile displays for taking over control from an automated vehicle. Results showed that a distinction can be made between four dimensions for coding vibrotactile information (amplitude, frequency, timing, and location), each of which can be static or dynamic. There is a consensus that frequency and amplitude are less suitable for coding information than location and timing. Vibrotactile stimuli have been shown to be effective as simple warnings. However, vibrations can evoke annoyance, and providing vibrations in close spatial–temporal proximity might cause a lack of comprehension of the signal. We describe the sequential stages of a take-over process and argue that vibrotactile displays are a promising candidate for redirecting the attention of a distracted driver. Furthermore, vibrotactile displays hold potential for supporting cognitive processing and action selection while resuming control of an automated vehicle. Finally, we argue that multimodal feedback should be used to assist the driver in the take-over process.

Tactile Displays of Pulse Oximetry

Prior investigations of vibrotactile displays suggest they have promise for use in the healthcare domain. This exploratory study forms part of a series exploring the use of an upper arm, continuously informing, vibrotactile display of pulse oximetry for clinicians. The study focused on the effect of vigilance on participants’ accuracy and latency for detecting and identifying changes in vital sign levels. Twenty-one participants were tested in a within-subjects design in four blocks of approximately 18 minutes duration each. Two blocks were a low workload condition and the other two blocks a high workload condition. Data were analysed against thresholds of 90% for accuracy and 10 seconds for response latency and workload conditions were also compared for accuracy and latency. Participants’ accuracy was not better than 90% and response latency was not shorter than 10 seconds, even in the low workload conditions. Participants were slower to detect changes in the high workload condition, and detection time worsened as the experiment progressed. Taken together, the results suggest that detecting rare events places a high strain on cognition and negatively affects performance. These findings have implications for the use of vibrotactile displays and will guide further investigations into the use of vibrotactile technology in healthcare.

Vibrotactile Display: Perception, Technology, and Applications

This paper reviews the technology and applications of vibrotactile display, an effective information transfer modality for the emerging area of haptic media. Our emphasis is on summarizing foundational knowledge in this area and providing implementation guidelines for application designers who do not yet have a background in haptics. Specifically, we explain the relevant human vibrotactile perceptual capabilities, detail the main types of commercial vibrotactile actuators, and describe how to build both monolithic and localized vibrotactile displays. We then identify exemplary vibrotactile display systems in application areas ranging from the presentation of physical object properties to broadcasting vibrotactile media content.

Supporting Speeded Navigational Communication via Gesture-Controlled Vibrotactile Displays

Recent research has shown that haptic displays are particularly well-suited to communicating navigation information, but these displays are rarely evaluated in situations that require time-critical communications. The present study serves as the first proof of concept for “CHIAD”: a new haptic interaction system that allows fast and efficient communication of navigation information by supporting gesture-based encoding of navigational instructions and intuitive decoding of the instructions by mapping them to vibration presentations at different body locations. Participant pairs completed a speeded target-selection navigation task by utilizing three different interfaces: verbal instructions via two-way radio, vibrotactile signals activated by a laptop-based interface, and the CHIAD system. The results show the fastest and most accurate performance with the CHIAD system, suggesting two conclusions: vibrotactile signals are more effective than verbal interactions in supporting speeded communication of simple navigation instructions; and natural gesture methods support faster encoding of instructions.

The Effect of Vibrotactile Stimulation on the Emotional Response to Horror Films

Over the last decade consumers have witnessed a dramatic increase in the use of low fidelity, discrete vibrotactile feedback to enhance or replace audio stimuli in entertainment systems. However, use of high-resolution continuous vibrotactile displays remains quite uncommon. The Emoti-Chair is a high-resolution continuous vibrotactile display that may be driven by any type of audio signal, and is purported to convey the emotional properties of sound through organized vibrotactile stimulation. In the current study, we examined the ability of the Emoti-Chair to convey the emotional content of the soundtrack in a horror film. Increases in skin conductance levels were observed when vibrotactile stimuli were added to audio/visual film content. These results provide evidence that users can augment the communication of emotion in film through use of a high-resolution continuous vibrotactile display.

A Vibro-Tactile Display for Clinical Monitoring

Vibro-tactile displays use human skin to convey information from physiological monitors to anesthesiologists, providing cues about changes in the status of the patient. In this investigation, we evaluated, in a real-time clinical environment, the usability and wearability of a novel vibro-tactile display belt recently developed by our group, and determined its accuracy in identifying events when used by anesthesiologists. A prospective observational study design was used. During routine anesthesia, a standard physiological monitor was connected to a software tool that used algorithms to automatically identify changing trends in mean noninvasive arterial blood pressure, expired minute ventilation, peak airway pressure, and end-tidal carbon dioxide partial pressure. The software was wirelessly interfaced to a vibro-tactile belt worn by the anesthesiologist. Each physiological variable was mapped to 1 of 4 tactor locations within the belt. The direction (increase/decrease) and 2 levels of change (small/large) were encoded in the stimulation patterns. A training session was completed by each anesthesiologist. The system was activated in real-time during anesthesia alongside routine physiological monitors. When the algorithms detected changes in the patient, the belt vibrated at the appropriate location with the pattern corresponding to the level and direction of change. Using a touch screen monitor the anesthesiologist was to enter the vibro-tactile message by first identifying the variable, then identifying the level and direction of change. Usability and wearability questionnaires were to be completed. The percentage of correct identification of the physiological trend, the direction of change, and the level of change were primary outcome variables. The mean usability score and wearability results were secondary outcome variables. We hypothesized that anesthesiologists would correctly identify the events communicated to them through the vibro-tactile belt 90% of the time, and that anesthesiologists would find the vibro-tactile belt usable and wearable. Seventeen anesthesiologists evaluated the display during 57 cases. The belt was operational for a mean (SD) duration of 75 (41) minutes per case. Seven cases were excluded from analysis because of technical failures. Eighty-one percent (confidence interval [CI], 77% to 84%) of all stimuli were decoded. The physiological trend, the direction of change, and the level of change were correctly identified for 97.7% (CI 96%-99%), 94.9% (CI 92%-97%), and 93.5% of these stimuli (CI, 91%-96%), respectively. Fourteen anesthesiologists completed the usability and wearability questionnaires. The mean usability score was 4.8 of a maximum usability score of 7. Anesthesiologists found a vibro-tactile belt to be wearable and usable and could accurately decode vibro-tactile messages in a real-time clinical environment.

Continuously Informing Vibrotactile Displays in Support of Attention Management and Multitasking in Anesthesiology

A novel vibrotactile display type was investigated to determine the potential benefits for supporting the attention and task management of anesthesiologists. Recent research has shown physiological monitoring and multitasking performance can benefit from displaying patient data via alarm-like tactile notifications and via continuously informing auditory displays (e.g., sonifications). The current study investigated a novel combination of these two approaches: continuously informing tactile displays. A tactile alarm and two continuously informing tactile display designs were evaluated in an anesthesia induction simulation with anesthesiologists as participants. Several performance measures were collected for two tasks: physiological monitoring and anesthesia induction. A multitask performance score equivalently weighted components from each task, normalized across experimental scenarios. Subjective rankings of the displays were also collected. Compared to the baseline (visual and auditory only) display configuration, each tactile display significantly improved performance in several objective measures, including multitask performance score. The continuously informing display that encoded the severity of patient health into the salience of its signals supported significantly better performance than the other two tactile displays. Contrasting the objective results, participants subjectively ranked the tactile alarm display highest. Continuously informing tactile displays with alarm-like properties (e.g., salience mapping) can better support anesthesiologists' physiological monitoring and multitasking performance under the high task demands of anesthesia induction. Adaptive display mechanisms may improve user acceptance. This study can inform display design to support multitasking performance of anesthesiologists in the clinical setting and other supervisory control operators in work domains characterized by high demands for visual and auditory resources.

Evaluation of Multiparameter Vibrotactile Display Designs to Support Physiological Monitoring Performance in Anesthesiology

The task set of anesthesiologists, like those of operators in many data-rich work domains, is characterized by heavy demand for visual and auditory resources. Employing tactile displays can offload some of this demand, potentially improving performance in tasks related to patient care during surgery, such as monitoring and managing multiple physiological systems. The current study compared anesthesiologists’ performance in an immersive patient simulator under four different physiological data display configurations: standard visual and auditory displays alone, and with the addition of three different vibrotactile display designs. Findings show that physiological management performance improved with the vibrotactile displays, compared to with standard displays alone. The best performance was found with “continuously-informing” vibrotactile displays which increased signal salience as represented parameters approached unsafe levels. The findings from this study have implications for tactile display design, a...

Characterization of Tactors Used in Vibrotactile Displays

A series of experiments was conducted to evaluate the operating characteristics of small DC motors that are often in tactile displays. The results indicated that these motors are reliable in terms of their frequency and amplitude of oscillation, but that the frequency varies across motors. A simulated skin material was developed to provide a substrate for evaluating the performance of the motors. There was a marked attenuation in frequency when the tactors were on this material and the surface waves could be detected 60 mm from the site of activation. These findings suggest that the spacing between tactors should be at least 60–80 mm if tactile cues are used to locate events in the environment.