Vibrotactile Patterns Research Articles

Comparing Static and Dynamic Vibration Cues in Wristband Haptic Feedback for Enhanced Driver Response in Automated Vehicles

Higher levels of driving automation make effective takeover requests critical. The wrist’s sensitivity to vibration makes wristband devices a potential carrier for sending these requests. However, the impacts of conveying takeover requests through directional vibrotactile patterns such as dynamic patterns (sequential stimuli occurring at different locations on the wrist) and static patterns (fixed stimuli at the same locations on the wrist) are unclear. Therefore, this study examined the effects of directional vibrotactile patterns on takeover performance among younger and older adults. Participants responded to four patterns (two dynamic, one static, and one baseline) in a simulated SAE Level 3 automated vehicle. Takeover performance was evaluated using reaction time and takeover time. The results show that the static and baseline patterns had shorter reaction and takeover times compared to the dynamic patterns. In addition, younger adults react faster to takeover requests compared to older adults. Findings provide important insights for the future design of human-machine interfaces via wristband devices for automated vehicles.

Listening to two-talker conversations in quiet settings: the role of listeners’ cognitive processing capabilities for memory and listening effort

Listening to conversing talkers in quiet environments and remembering the content is a common activity. However, research on the cognitive demands involved is limited. This study investigates the relevance of individuals’ cognitive functions for listeners’ memory of two-talker conversations and their listening effort in quiet listening settings. A dual-task paradigm was employed to explore memory of conversational content and listening effort while analyzing the role of participants’ (n = 29) working memory capacity (measured through the operation span task), attention (Frankfurt attention inventory 2), and information-processing speed (trail making test). In the primary task, participants listened to a conversation between a male and female talker and answered content-related questions. The two talkers’ audio signals were presented through headphones, either spatially separated (+ /– 60°) or co-located (0°). Participants concurrently performed a vibrotactile pattern recognition task as a secondary task to measure listening effort. Results indicated that attention and processing speed were related to memory of conversational content and that all three cognitive functions were related to listening effort. Memory performance and listening effort were similar for spatially separated and co-located talkers when considering the psychometric measures. This research offers valuable insights into cognitive processes during two-talker conversations in quiet settings.

DrivingVibe: Enhancing VR Driving Experience using Inertia-based Vibrotactile Feedback around the Head

We present DrivingVibe, which explores vibrotactile feedback designs around the head to enhance VR driving motion experiences. We propose two approaches that use a 360-degree vibrotactile headband: 1) mirroring and 2) 3D inertia-based. The mirroring approach extends the vibrotactile patterns of handheld controllers to actuate the entire headband uniformly. The 3D inertia-based approach uses the acceleration telemetry data that driving games/simulators export to motion platforms to generate directional vibration patterns, including: i) centrifugal forces, ii) horizontal acceleration/deceleration, and iii) vertical motion due to rough terrain. The two approaches are complementary as the mirroring approach supports all driving games because it does not require telemetry data, while the 3D inertia-based approach provides higher feedback fidelity for games that provide such data. We conducted a 24-person user experience evaluation in both passive passenger mode and active driving mode. Study results showed that both DrivingVibe designs significantly improved realism, immersion, and enjoyment (p<.01) with large effect sizes for the VR driving experiences. For overall preference, 88% (21/24) of participants preferred DrivingVibe, with a 2:1 preference for 3D inertia-based vs. mirroring designs (14 vs. 7 participants). For immersion and enjoyment, 96% (23/24) of participants preferred DrivingVibe, with nearly a 3:1 preference (17 vs. 6 participants) for the 3D inertia-based design.

To Inform or to Instruct? An Evaluation of Meaningful Vibrotactile Patterns to Support Automated Vehicle Takeover Performance

Automated vehicles may occasionally require drivers to take over. The complexity of the takeover process warrants the design of effective human–machine interfaces that assist drivers in regaining control, especially when the visual and auditory sensory modalities are occupied. Vibrotactile displays, which can represent information about the status, direction, and position of driving environment elements, have been suggested as one promising approach, but their effectiveness to aid in takeover transitions has not been fully evaluated. This study investigated the effects of meaningful tactile signal patterns, used as takeover requests, on automated vehicle takeover performance. Forty participants rode in a simulated SAE Level 3 automated vehicle and completed a series of takeover tasks with two tactile pattern formats, i.e., informative (which displayed status information of surrounding vehicles) and instructional (that displayed the appropriate takeover maneuver), and three in-vehicle locations (seat back, seat pan, and a seat back and seat pan combination). Takeover response options included lane changes only or brake applications followed by changing lanes, depending on the locations of surrounding vehicles. Results indicate that only meaningful instructional tactile signals, in either the seat back or seat pan, were associated with worse takeover response time and maximum resulting acceleration compared to signals without any patterns. Additionally, tactile information presented on the seat back was perceived as the most useful and satisfying. Findings from this study can inform the development of next-generation human–machine interfaces that utilize tactile stimulation in a wide range of environments with automation.

Statistical context learning in tactile search: Crossmodally redundant, visuo-tactile contexts fail to enhance contextual cueing

In search tasks, reaction times become faster when the target is repeatedly encountered at a fixed position within a consistent spatial arrangement of distractor items, compared to random arrangements. Such “contextual cueing” is also obtained when the predictive distractor context is provided by a non-target modality. Thus, in tactile search, finding a target defined by a deviant vibro-tactile pattern (delivered to one fingertip) from the patterns at other, distractor (fingertip) locations is facilitated not only when the configuration of tactile distractors is predictive of the target location, but also when a configuration of (collocated) visual distractors is predictive—where intramodal-tactile cueing is mediated by a somatotopic and crossmodal-visuotactile cueing by a spatiotopic reference frame. This raises the question of whether redundant multisensory, tactile-plus-visual contexts would enhance contextual cueing of tactile search over and above the level attained by unisensory contexts alone. To address this, we implemented a tactile search task in which, in 50% of the trials in a “multisensory” phase, the tactile target location was predicted by both the tactile and the visual distractor context; in the other 50%, as well as a “unisensory” phase, the target location was solely predicted by the tactile context. We observed no redundancy gains by multisensory-visuotactile contexts, compared to unisensory-tactile contexts. This argues that the reference frame for contextual learning is determined by the task-critical modality (somatotopic coordinates for tactile search). And whether redundant predictive contexts from another modality (vision) can enhance contextual cueing depends on the availability of the corresponding spatial (spatiotopic-visual to somatotopic-tactile) remapping routines.

Real-time vibrotactile pattern generation and identification using discrete event-driven feedback

This study assesses human identification of vibrotactile patterns by using real-time discrete event-driven feedback. Previously acquired force and bend sensor data from a robotic hand were used to predict movement-type (stationary, flexion, contact, extension, release) and object-type (no object, hard object, soft object) states by using decision tree (DT) algorithms implemented in a field-programmable gate array (FPGA). Six able-bodied humans performed a 2- and 3-step sequential pattern recognition task in which state transitions were signaled as vibrotactile feedback. The stimuli were generated according to predicted classes represented by two frequencies (F1: 80 Hz, F2: 180 Hz) and two magnitudes (M1: low, M2: high) calibrated psychophysically for each participant; and they were applied by two actuators (Haptuators) placed on upper arms. A soft/hard object was mapped to F1/F2; and manipulating it with low/high force was assigned to M1/M2 in the left actuator. On the other hand, flexion/extension movement was mapped to F1/F2 in the right actuator, with movement in air as M1 and during object manipulation as M2. DT algorithm performed better for the object-type (97%) than the movement-type (88%) classification in real time. Participants could recognize feedback associated with 14 discrete-event sequences with low-to-medium accuracy. The performance was higher (76 ± 9% recall, 76 ± 17% precision, 78 ± 4% accuracy) for recognizing any one event in the sequences. The results show that FPGA implementation of classification for discrete event-driven vibrotactile feedback can be feasible in haptic devices with additional cues in the physical context.

Spatiotemporal influences on the recognition of two-dimensional vibrotactile patterns on the abdomen.

Spatial and temporal factors are known to highly influence tactile perception, but their role has been largely unexplored in the case of two-dimensional (2D) pattern recognition. We investigated whether recognition is facilitated by the spatial and/or temporal separation of pattern elements, or by conditions known to favor perceptual integration, such as the ones eliciting apparent movement. 2D vibrotactile patterns were presented to the abdomen of novice participants. In Experiment 1, we manipulated the spatial (inter-tactor distance) and temporal (burst duration and inter-burst interval) parameters applied to the tracing mode (sequential activation of pattern elements). In Experiment 2, we compared display modes differing in their level of temporal overlap in the presentation of pattern elements: the static mode (simultaneous activation of pattern elements), the slit-scan mode (pattern revealed line by line), and the tracing mode. The results of both experiments reveal that (a) recognition performance increases with the isolation of pattern elements in space and/or in time, (b) spatial and temporal factors interact in pattern recognition, and (c) conditions leading to apparent movement tend to be associated with lower recognition accuracy. These results further our understanding of tactile perception and provide guidance for the design of future vibrotactile communication systems. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The Effects of Tactile Display on Automated Vehicle Takeover: A Literature Review

Current autonomous vehicles are still semi-autonomous and require drivers to take over control of the vehicle under various conditions (e.g., encountering erased lane markings). This presents an issue in human-machine interaction, as there is a need for reliable methods to guide drivers through the sudden and complex takeover process. A tactile display that can present multi-dimensional information (e.g., status, direction, and position) may be a good option, especially when the information presented in their visual and auditory channels is overloading. However, limited work has attempted to summarize this topic. Therefore, the goal of this study is to synthesize literature that examined the effects of tactile display on takeover performance in automated vehicles. Findings indicated that tactile displays can be placed in multiple in-vehicle locations to present various vibrotactile patterns helping to improve drivers’ performance during the automated vehicle takeover, which could inform the design of human-machine interfaces for autonomous vehicles.

VIREO: Web-based Graphical Authoring of Vibrotactile Feedback for Interactions with Mobile and Wearable Devices

We introduce VIREO, a web-based software tool for graphical authoring of vibrotactile feedback for mobile and wearable applications. VIREO enables flexible specification of vibrotactile patterns with model-based and free-draw input, and is compatible with devices that run JavaScript, either natively or in a web browser. We demonstrate VIREO with applications developed for smartphones, smartwatches, armbands, and smartglasses, and we present the results of a usability evaluation study with sixteen participants represented by coders with various programming experience. We discuss our contributions in the context of the results of a Systematic Literature Review conducted on the topic of software tools, editors, and platforms developed in the scientific community for authoring vibrotactile feedback. Given that one finding of our review is the little availability of such contributions, we release VIREO as a free resource on the web for researchers and practitioners to author and integrate vibrotactile feedback in mobile and wearable applications.

Examining the efficacy of vibrotactile displays for monitoring patient vital signs: Six laboratory studies of change detection and state identification.

Healthcare workers often monitor patients while moving between different locations and tasks, and away from conventional monitoring displays. Vibrotactile displays can provide patient information in vibrotactile patterns that are felt regardless of the worker's location. We examined how effectively participants could identify changes in vibrotactile representations of patient heart rate (HR) and oxygen saturation (SpO₂). In Experiment 1, participants identified changes in HR and SpO₂ with greater than 90% accuracy while using vibrotactile displays configured in either an integrated or a separated format. In Experiment 2, incidental auditory and visual cues were removed and performance was still greater than 90% for the integrated display. In Experiments 3 and 4, ongoing tasks with low or high task load were introduced; high load worsened participants' response accuracy and speed at identifying vital signs. In Experiments 5 and 6, alternative designs were tested, including a design with a seemingly more natural mapping of HR to vibrotactile stimulation. However, no design supported more accurate performance than the integrated display. Results are interpreted with respect to multiple resource theory, and constraints on conforming to design guidelines are noted. Vibrotactile displays appear to be viable and therefore potentially suitable for use in healthcare and other contexts. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Visualisation Driven Training for Vibrotactile Skin Reading.

Vibrotactile skin-reading effectively conveys rich information via vibrotactile patterns, which has gained attention due to recent advancements. However, training to recognize and associate vibrotactile patterns with their meaning is time-consuming and tedious. The conventional training methods use repetitive exposure of the vibrotactile stimuli along with visual and auditory cues of the corresponding symbol. This work proposes a novel visual-based training method to teach users the associations between semantic information and vibrotactile patterns. Our proposed visual explanation training is compared with the conventional training method in a study with 18 participants. Results show that participants achieve a better performance using the new visual explanation training when identifying single English alphabet characters. Moreover, the proposed training also incurred a significantly lower workload (NASA TLX) and was preferred by study participants. The proposed method is thus effective and offers a less stressful form of training users for skin reading.

Feel and touch: a haptic mobile game to assess tactile processing

Haptic interfaces have great potential for assessing the tactile processing of children with Autism Spectrum Disorder (ASD), an area that has been under-explored due to the lack of tools to assess it. Until now, haptic interfaces for children have mostly been used as a teaching or therapeutic tool, so there are still open questions about how they could be used to assess tactile processing of children with ASD. This article presents the design process that led to the development of Feel and Touch, a mobile game augmented with vibrotactile stimuli to assess tactile processing. Our feasibility evaluation, with 5 children from 3 to 6 years old, shows that children accept vibrations and are able to use the proposed vibrotactile patterns. However, it is still necessary to work on the instructions to make the game dynamic clearer and rewards to keep the attention of children. We close this article by discussing future work and conclusions.

Emotional Response to Vibrothermal Stimuli

Emotional response to haptic stimuli is a widely researched topic, but the combination of vibrotactile and thermal stimuli requires more attention. The purpose of this study is to investigate emotional response to vibrothermal stimulation by combining spatiotemporal vibrotactile stimulus with dynamic thermal stimulus (hot or cold). The vibrotactile and thermal stimuli were produced using the Haptic Chair and the Embr wave thermal bracelet, respectively. The results show that spatiotemporal vibrotactile patterns and their duration, and dynamic thermal stimulation, have an independent effect on the emotional response. Increasing duration generally increases the valence and arousal of emotional response. Shifting the dynamic temperature from cold to hot generally decreases the valence of emotional response but has no significant effect on arousal. Nevertheless, certain spatiotemporal patterns do exhibit unique responses to changes in dynamic temperature, although no interaction effects were found. The results show the potential of designing affective haptic interfaces using multimodal vibrothermal feedback.

Estimation of Torso Vibrotactile Thresholds Using Eccentric Rotating Mass Motors.

The characterization of vibrotactile perception is crucial to accurately configure haptic devices and create appropriate stimuli for improving user performance in human-machine interaction systems. This article presents a study aiming to determine the absolute and differential vibrotactile thresholds in different areas of the torso to develop reliable haptic patterns to be displayed using a haptic vest. In the 'absolute threshold' experiment, we measure the minimum detectable vibration using a forced-choice task. Furthermore, in the 'differential threshold' experiment, we measure the minimum frequency change needed for users to discriminate two successive vibrotactile stimuli using a vibration matching task. The first experiment does not show differences between absolute thresholds, opening up the possibility of setting a unique minimal vibration for creating haptic patterns. Similarly, the second experiment does not show differences between differential thresholds. Moreover, as these thresholds follow Weber's law, it is viable to estimate any upper or lower differential threshold for any reference stimulus using a K-value. These results are a first step for creating vibrotactile patterns over the torso with the employed eccentric rotating mass motors. Moreover, the whole study provides a method to obtain these psychophysical values since the usage of different motors can change these results.

Wearable multichannel haptic device for encoding proprioception in the upper limb

Objective. We present the design, implementation, and evaluation of a wearable multichannel haptic system. The device is a wireless closed-loop armband driven by surface electromyography (EMG) and provides sensory feedback encoding proprioception. The study is motivated by restoring proprioception information in upper limb prostheses. Approach. The armband comprises eight vibrotactile actuators that generate distributed patterns of mechanical waves around the limb to stimulate perception and to transfer proportional information on the arm motion. An experimental study was conducted to assess: the sensory threshold in eight locations around the forearm, the user adaptation to the sensation provided by the device, the user performance in discriminating multiple stimulation levels, and the device performance in coding proprioception using four spatial patterns of stimulation. Eight able-bodied individuals performed reaching tasks by controlling a cursor with an EMG interface in a virtual environment. Vibrotactile patterns were tested with and without visual information on the cursor position with the addition of a random rotation of the reference control system to disturb the natural control and proprioception. Main results. The sensation threshold depended on the actuator position and increased over time. The maximum resolution for stimuli discrimination was four. Using this resolution, four patterns of vibrotactile activation with different spatial and magnitude properties were generated to evaluate their performance in enhancing proprioception. The optimal vibration pattern varied among the participants. When the feedback was used in closed-loop control with the EMG interface, the task success rate, completion time, execution efficiency, and average target-cursor distance improved for the optimal stimulation pattern compared to the condition without visual or haptic information on the cursor position. Significance. The results indicate that the vibrotactile device enhanced the participants’ perceptual ability, suggesting that the proposed closed-loop system has the potential to code proprioception and enhance user performance in the presence of perceptual perturbation.

VibroSleeve: A wearable vibro-tactile feedback device for arm guidance.

Vibro-tactile feedback offers a complementary augmentation cue for motor guidance and training. Motivated by the needs of prosthetic vision rehabilitation, we explore the use of the cylindrical forearm surface to deliver arm guidance cues via vibro-tactile stimulation. We present 'VibroSleeve', a novel wearable arm motion guidance aid made up of 4x4 arrangement of vibration coin motors embedded within an elastic sleeve for delivering vibro-tactile patterns to the forearm. In this paper, we present the concept and design of VibroSleeve, along with results of preliminary evaluation. We outline key insights gained into the perceptual aspects of calibration and usable intensity bandwidth critical for reliable interpretation of encoded information. Our results demonstrate feasibility of the approach, and provide foundations for future work on developing the sleeve as a rehabilitation aid for guiding the arm towards visually perceived targets.

PIV

We describe the design and evaluation of PIV, a personalizable and inconspicuous vibrotactile breathing pacer. Given the prevalence and adverse impact of anxiety and anxiety disorders, our goal is to develop a technology that helps people regulate their anxiety through paced breathing. We examined two previously unstudied questions: What is an effective vibrotactile pattern for paced breathing, and where should the tactors be placed on the body to make the pacer most effective? We designed a series of personalized vibrotactile pacing patterns, and evaluated them on three body sites, in terms of self-reported and psychophysiological measures including skin conductance and breath wave parameters. The results show that personalization plays an important role in PIV’s pattern and placement design choices. We concluded that the choice of frequency based, strong-exhale-phased patterns and abdomen placement are appropriate for future studies.

Evaluation of Optimal Vibrotactile Feedback for Force-Controlled Upper Limb Myoelectric Prostheses.

The main goal of this study is to evaluate how to optimally select the best vibrotactile pattern to be used in a closed loop control of upper limb myoelectric prostheses as a feedback of the exerted force. To that end, we assessed both the selection of actuation patterns and the effects of the selection of frequency and amplitude parameters to discriminate between different feedback levels. A single vibrotactile actuator has been used to deliver the vibrations to subjects participating in the experiments. The results show no difference between pattern shapes in terms of feedback perception. Similarly, changes in amplitude level do not reflect significant improvement compared to changes in frequency. However, decreasing the number of feedback levels increases the accuracy of feedback perception and subject-specific variations are high for particular participants, showing that a fine-tuning of the parameters is necessary in a real-time application to upper limb prosthetics. In future works, the effects of training, location, and number of actuators will be assessed. This optimized selection will be tested in a real-time proportional myocontrol of a prosthetic hand.

The Syncopated Energy Algorithm for Rendering Real-Time Tactile Interactions

In this paper, we present a novel vibrotactile rendering algorithm for producing real-time tactile interactions suitable for virtual reality applications. The algorithm uses an energy model to produce smooth tactile sensations by continuously recalculating the location of a phantom actuator that represents a virtual touch point. It also employs syncopations in its rendered amplitude to produce artificial perceptual anchors that make the rendered vibrotactile patterns more recognizable. We conducted two studies to compare this Syncopated Energy algorithm to a standard real-time Grid Region algorithm for rendering touch patterns at different vibration amplitudes and frequencies. We found that the Grid Region algorithm afforded better recognition, but that the Syncopated Energy algorithm was perceived to produce smoother patterns at higher amplitudes. Additionally, we found that higher amplitudes afforded better recognition while a moderate amplitude yielded more perceived continuity. We also found that a higher frequency resulted in better recognition for fine-grained tactile sensations and that frequency can affect perceived continuity.

Evaluating In-Car Movements in the Design of Mindful Commute Interventions: Exploratory Study.

BackgroundThe daily commute could be a right moment to teach drivers to use movement or breath towards improving their mental health. Long commutes, the relevance of transitioning from home to work, and vice versa and the privacy of commuting by car make the commute an ideal scenario and time to perform mindful exercises safely. Whereas driving safety is paramount, mindful exercises might help commuters decrease their daily stress while staying alert. Increasing vehicle automation may present new opportunities but also new challenges.ObjectiveThis study aimed to explore the design space for movement-based mindful interventions for commuters. We used qualitative analysis of simulated driving experiences in combination with simple movements to obtain key design insights.MethodsWe performed a semistructured viability assessment in 2 parts. First, a think-aloud technique was used to obtain information about a driving task. Drivers (N=12) were given simple instructions to complete movements (configural or breath-based) while engaged in either simple (highway) or complex (city) simulated urban driving tasks using autonomous and manual driving modes. Then, we performed a matching exercise where participants could experience vibrotactile patterns from the back of the car seat and map them to the prior movements.ResultsWe report a summary of individual perceptions concerning different movements and vibrotactile patterns. Beside describing situations within a drive when it may be more likely to perform movement-based interventions, we also describe movements that may interfere with driving and those that may complement it well. Furthermore, we identify movements that could be conducive to a more relaxing commute and describe vibrotactile patterns that could guide such movements and exercises. We discuss implications for design such as the influence of driving modality on the adoption of movement, need for personal customization, the influence that social perception has on participants, and the potential role of prior awareness of mindful techniques in the adoption of new movement-based interventions.ConclusionsThis exploratory study provides insights into which types of movements could be better suited to design mindful interventions to reduce stress for commuters, when to encourage such movements, and how best to guide them using noninvasive haptic stimuli embedded in the car seat.