Wearable Haptic Device Research Articles

Wearable Haptic Device as Mobility Aid for Blind People: Electronic Cane - Wearable Device for Mobility of Blind People

The conventional long cane, largely used for mobility of visually impaired people, presents some limitations, such as the short-range detection of obstacles and the inability to protect against head-level obstacles. The purpose of this study was to develop and test a wearable haptic interface system attachable to a long cane in order to detect obstacles and provide notification to the user.

Design, Control, and Psychophysics of Tasbi: A Force-Controlled Multimodal Haptic Bracelet

Haptic feedback is known to enhance the realism of an individual’s interactions with objects in virtual environments. Wearable haptic devices, such as vibrotactile sleeves or armbands, can provide haptic feedback in a smaller and more lightweight form factor than haptic gloves that can be bulky and cumbersome to the wearer. In this article, we present tactile and squeeze bracelet interface (Tasbi), a multimodal haptic wristband that can provide radial squeeze forces around the wrist along with vibrotactile feedback at six discrete locations around the band. Tasbi implements a squeezing mechanism that minimizes tangential forces between the band’s points of contact with the skin, instead of focusing the motor actuation to predominantly normal forces. Force sensing capacitors enable closed-loop control of the squeeze force, while vibration is achieved with linear resonant actuators. A detailed description of the design and experimental results demonstrating closed-loop control of squeeze cues provided by Tasbi is presented. Additionally, we present the results of psychophysical experiments that quantify user perception of the vibration and squeeze cues, including vibrotactile identification accuracy in the presence of varying squeeze forces, discrimination thresholds for the squeeze force, and an analysis of user preferences for squeeze actuation magnitudes.

Scalp-Targeted Haptic Proprioception for Upper-Limb Prosthetics.

In this paper, a head-worn wearable haptic feedback device (WHFD) is developed to communicate sensory information from an upper-limb prosthesis. A 14-week, 6-stage, between-subjects study was created to investigate the learning trajectory as participants were stimulated with haptic patterns conveying joint proprioception. Healthy participants were divided into three groups, with each group using a different haptic stimulation methods. 18 participants completed the study within 7-14 weekly sessions, demonstrating that participants were, in fact, learning to interpret the haptic information. Participants in the spatiotemporal stimulation group had some advantages in interpreting the haptic information over the others; however, each stimulation method has advantages that can be exploited and hybridized for future models of the WHFD. Overall, the proposed WHFD is an effective non-invasive device that can promote greater sensory awareness for wearers of prostheses.

A Wearable Textile-Embedded Dielectric Elastomer Actuator Haptic Display.

With advances in mobile computing and virtual/augmented reality technologies, communicating through touch using wearable haptic devices is poised to enrich and augment current information delivery channels that typically rely on sight and hearing. To realize a wearable haptic device capable of effective data communication, both ergonomics and haptic performance (i.e., array size, bandwidth, and perception accuracy) are essential considerations. However, these goals often involve challenging and conflicting requirements. We present an integrated approach to address these conflicts, which includes incorporating multilayered dielectric elastomer actuators, a lumped-parameter model of the skin, and a wearable frame in the design loop. An antagonistic arrangement-consisting of an actuator deforming the skin-was used to achieve effective force transmission while maintaining a low profile, and the effect of the wearable frame and structure was investigated through lumped-model analysis and human perception studies.

Virtual Reality Based Tactile Sensing Enhancements for Bilateral Teleoperation System With In-Hand Manipulation

Tactile sensing is important for contact-rich tasks especially in where an in-hand manipulation is involved. In teleoperation, such feedback can provide information of when and where the contacts happen, and is essential for a human operator to make appropriate actions. To improve the experience in human-robot interaction in teleoperation without vision feedback, in this letter, a model-based sensing enhancement system is proposed. This system allows a human operator to remotely control a dexterous robotics hand with a contact feedback in the form of haptics. Under this framework, we introduce a calibration method to map the hand joint movements of the master and the slave. Given noisy robot sensory data, a learning based approach is adopted to estimate the object pose online. The estimated pose is sent to Unity, of which is leveraged to calculate the hand-object contact force. Finally, this force is rendered to the master, a wearable haptic device, worn by the operator. Our experiments have shown that with this contact information, the performance surpassed those conducted on a bilateral teleoperation system without sense of contact. Additionally, the user can safely manipulate the object with the robot’s hand.

A Moisture-Resistant Soft Actuator with Low Driving Voltages for Haptic Stimulations in Virtual Games.

Strong and robust stimulations to human skins with low driving voltages under high moisture working conditions are desirable for wearable haptic feedback applications. Here, a soft actuator based on the "air bubble" electret structure is developed to work in high-moisture environments and produce haptic sensations to human skin with low driving voltages. Experimentally, the water soaking and drying process has been conducted repeatedly for the first time and the 20th time to test the antimoisture ability of the actuator as it recovers its output force up 90 and 65% of the initial value, respectively. The threshold voltages for sensible haptic sensations for the fingertip and palm of volunteers have been characterized as 7 and 10 V, respectively. Furthermore, a demonstration example has been designed and conducted in a virtual boxing game to generate the designated haptic sensations according to the gaming conditions with an accuracy of 98% for more than 100 tests. As such, the design principle, performance characteristic, and demonstration example in this work could inspire various applications with improved reliability for wearable haptic devices.

Hand Tracking with Vibrotactile Feedback Enhanced Presence, Engagement, Usability, and Performance in a Virtual Reality Rhythm Game

Recent hand tracking systems and wearable haptic devices have contributed to enhancing user experience in virtual environments. However, controllers are still prevalent in virtual reality (VR) games as a main interaction device. Also, haptic devices are rare and not widely accepted by users. In this article, we examined the effects of interaction methods and vibrotactile feedback on users’ sense of presence, engagement, usability, and task performance in a VR game. In our experiment, 36 participants wearing VR goggle played a rhythm game under three conditions: (1) VR controllers, (2) hand tracking without vibrotactile feedback, and (3) hand tracking with vibrotactile feedback at fingertips through the gloves we developed. Results showed that hand tracking improved presence, engagement, usability, and performance, compared to the VR controller. Furthermore, vibrotactile feedback enhanced presence and engagement even more clearly. Results are discussed with the components of VR user experience and practical design guidelines.

Discrete Cutaneous Feedback for Reducing Dimensions of Wearable Haptic Devices

In this article, we explore alternative cutaneous haptic feedback for rendering modulation of the grasping force. The aim of the study was to reduce power requirements and in turn dimensions of the actuators, in wearable devices applied to virtual or teleoperated manipulation. This is critical in certain rehabilitation or training scenarios where haptics should not interfere with dexterity of the user. In the study, we experimented discrete, pulsed cutaneous force feedback and compared it with conventional continuous proportional feedback, in a virtual pick and place task. We made use of wearable thimbles based on voice coil actuators in order to provide high-quality, low-noise haptic feedback to the participants. The evaluation was performed on the basis of both objective measurements of task performance (measured virtual forces and correct ratio) and a questionnaire evaluating participants’ preferences for the different feedback conditions. On the basis of the obtained results, in the article, we discuss the possibility of providing high-frequency, discretized cutaneous feedback only, driven by modulation of the grasping force. The opportunity is to reduce volume and mass of the actuators and also to consider alternative design solutions, due to the different requirements in terms of static and high-frequency components of the output force.

A parallel-elastic actuation approach for wide bandwidth fingertip haptic devices

Wearable haptic devices are used to render sense of touch in different virtual reality, simulated or teleoperated environments. Design of these devices has to comply with dimensional constraints imposed by ergonomics and usability, introducing compromises between size of the actuators and features of the rendered haptic stimuli, such as peak forces and bandwidth. We propose a new design approach for wearable haptic devices resembling the micro-macro actuation concept: it is based on two distinct actuators with different mechanical reduction, coupled by an elastic element. We show this better matches the output range of the actuators to features of the signals used in typical haptic rendering. We investigated the approach through an analytical model, a numerical model, and physical experiments conducted after design and development of a working prototype. The theoretical and simulated models allow to better understand dynamic interaction of the system parts, and to define design guidelines for the development of the real device. The adopted design solutions were implemented and evaluated in the prototype of a highly wearable fingertip device. Final experimental results show how the implementation of the proposed method is capable of an effective haptic rendering, that better matches the desired frequency response.

DeviceD: Audience-dancer interaction via social media posts and wearable for haptic feedback.

The performative installation DeviceD utilizes a network of systems toward facilitating interaction between dancer, digital media, and audience. Central to the work is a wearable haptic feedback system able to wirelessly deliver vibrotactile stimuli, with the latter initiated by the audience through posting on Twitter social media platform; the system in use searches for specific mentions, hashtags, and keywords, with positive results causing the system to trigger patterns of haptic biofeedback across the wearable's four actuator motors. The system acts as the intermediator between the audience's online actions and the dancer receiving physical stimuli; the dancer interprets these biofeedback signals according to Laban's Effort movement qualities, with the interpretation informing different states of habitual and conscious choreographic performance. In this article, the authors reflect on their collaborative process while developing DeviceD alongside a multidisciplinary team of technologists, detailing their experience of refining the technology and methodology behind the work while presenting it in three different settings. A literature review is used to situate the work among contemporary research on interaction over internet and haptics in performance practice; haptic feedback devices have been widely used within artistic work for the past 25years, with more recent practice and research outputs suggesting an increased interest for haptics in the field of dance research. The authors detail both technological and performative elements making up the work, and provide a transparent evaluation of the system, as means of providing a foundation for further research on wearable haptic devices.

HaPouch: A Miniaturized, Soft, and Wearable Haptic Display Device Using a Liquid-to-Gas Phase Change Actuator

Wearable haptic displays can provide haptic information while allowing for free body movement. Among these haptic displays, pneumatic haptic displays have the advantages of flexibility and lightweight; however, they require bulky air tubes and a heavy air compressor. To solve this problem, we propose a wearable haptic display that uses a liquid-to-gas phase change actuator and a Peltier device as a way to reduce the size of the entire system. A low-boiling-point liquid is encapsulated in the flexible bladder of the actuator, and the vaporization of the liquid, which induces the inflation of the actuator, is controlled by the external Peltier device. In this study, we implemented a pressure sensor to monitor pressure inside the liquid-to-gas phase change actuator. The pressure measurement will contribute to controlling the generated normal force. First, we characterized the pressure response concerning the design of the liquid-to-gas phase change actuator. Next, we evaluated the output normal force of the haptic display and confirmed that the maximum output force reached a few newtons, which is a similar level to the off-the-shelf wearable haptic display devices. Finally, a sensory evaluation revealed that the experimental participants perceived the haptic stimulus to their fingertips provided by the proposed haptic display in a few seconds. According to the obtained results, the proposed haptic display can be applied to applications such as human interfaces to provide force, allowing for a response time of a few seconds.

Wearable Haptic Device Presenting Sensations of Fingertips to the Forearm.

Several existing haptic displays used in virtual reality (VR) environments present haptic sensations generated by the fingertips in the VR to actual fingertips. However, these devices face certain challenges, such as physical interference between the devices, particularly when multi-degree-of-freedom (DOF) force needs to be presented to multiple fingers. To address this issue, we propose a haptic presentation method that transmits haptic sensations generated by the fingertips in the VR, including the direction of the force, to the forearm. We previously proposed a method to present both magnitude and direction of the force applied to the index finger using a five-bar linkage mechanism, which transmits the force sensation with two DOF to the forearm. In this study, the forces in the downward and left-right directions were obtained from the kinematics of a five-bar linkage mechanism for accurate force presentation. Additionally, we conducted a user study evaluating user grasping an object in the VR and performing task. The results verified the haptic sensation of the force transmitted by the proposed prototype to the user's forearm provides a sufficient comfort level. Furthermore, the task execution time and comfort level were comparable to those of a vibrotactile presentation presented directly to the fingertips.

Effect of Tactile Masking on Multi-Sensory Haptic Perception.

Multi-sensory wearable haptic devices are able to encode a variety of information using multiple haptic cues. However, simultaneous cues can be misperceived due to tactile masking effects. In this paper, we investigate the effect of masking on the perception of skin stretch and squeeze. We performed three experiments measuring the just-noticeable difference (JND) and the absolute threshold of skin stretch and squeeze alone and in the presence of simultaneous haptic cues. Additionally, we investigate the relative perceptual amplitudes of these haptic cues. Results indicate that the JND for a skin stretch cue increases with a masking squeeze cue, while the JND for a squeeze cue does not change with a masking stretch cue. Also, masking has a significant effect on the absolute threshold of both skin stretch and squeeze. These results suggest that the effect of masking diminishes as haptic cues become larger in amplitude. The results from the subjective equality experiment suggest a potential nonlinear relationship between perceptual magnitudes. Further testing should be carried out to investigate this relationship. Future multi-sensory devices can use these perceptual experiment findings to ensure the delivery of salient cues to users.

A Survey on Haptic Technologies for Mobile Augmented Reality

Augmented reality (AR) applications have gained much research and industry attention. Moreover, the mobile counterpart—mobile augmented reality (MAR) is one of the most explosive growth areas for AR applications in the mobile environment (e.g., smartphones). The technical improvements in the hardware of smartphones, tablets, and smart-glasses provide an advantage for the wide use of mobile AR in the real world and experience these AR applications anywhere. However, the mobile nature of MAR applications can limit users’ interaction capabilities, such as input and haptic feedback. In this survey, we analyze current research issues in the area of human-computer interaction for haptic technologies in MAR scenarios. The survey first presents human sensing capabilities and their applicability in AR applications. We classify haptic devices into two groups according to the triggered sense: cutaneous/tactile : touch, active surfaces, and mid-air; kinesthetic : manipulandum, grasp, and exoskeleton. Due to MAR applications’ mobile capabilities, we mainly focus our study on wearable haptic devices for each category and their AR possibilities. To conclude, we discuss the future paths that haptic feedback should follow for MAR applications and their challenges.

A Twisted String, Flexure Hinges Approach for Design of a Wearable Haptic Thimble

Wearable haptic devices in the shape of actuated thimbles are used to render the sense of touch in teleoperation and virtual reality scenarios. The design of similar devices has to comply with concurring requirements and constraints: lightweight and compactness, intensity and bandwidth of the rendered signals. Micro-sized motors require a mechanical reduction to increase the output force, at the cost of noise and vibrations introduced by conventional gear reducers. Here we propose a different actuation method, based on a miniaturized twisted string actuator and a flexure hinge transmission mechanism. The latter is required to transmit and transform the pulling force of the twist actuator to a pushing force of the plate in contact with the fingerpad. It achieves a lightweight and noiseless actuation in a compact mechanism. In this work, we present design guidelines of the proposed approach, optimization, and FEM analysis of the flexure hinge mechanism, implementation of the prototype, and experimental characterization of the twist actuator measuring frequency response and output force capabilities.

Wearable Haptic Device for Stiffness Rendering of Virtual Objects in Augmented Reality

We propose a novel wearable haptic device that can provide kinesthetic haptic feedback for stiffness rendering of virtual objects in augmented reality (AR). Rendering stiffness of objects using haptic feedback is crucial for realistic finger-based object manipulation, yet challenging particularly in AR due to the co-presence of a real hand, haptic device, and rendered AR objects in the scenes. By adopting passive actuation with a tendon-based transmission mechanism, the proposed haptic device can generate kinesthetic feedback strong enough for immersive manipulation and prevention of inter-penetration in a small-form-factor, while maximizing the wearability and minimizing the occlusion in AR usage. A selective locking module is adopted in the device to allow for the rendering of the elasticity of objects. We perform an experimental study of two-finger grasping to verify the efficacy of the proposed haptic device for finger-based manipulation in AR. We also quantitatively compare/articulate the effects of different types of feedbacks across haptic and visual sense (i.e., kinesthetic haptic feedback, vibrotactile haptic feedback, and visuo-haptic feedback) for stiffness rendering of virtual objects in AR for the first time.

A tuned mass amplifier for enhanced haptic feedback

Vibro-tactile feedback is, by far the most common haptic interface in wearable or touchable devices. This feedback can be amplified by controlling the wave propagation characteristics in devices, by utilizing phenomena such as structural resonance. However, much of the work in vibro-tactile haptics has focused on amplifying local displacements in a structure by increasing local compliance. In this paper, we show that engineering the resonance mode shape of a structure with embedded localized mass amplifies the displacements without compromising on the stiffness or resonance frequency. The resulting structure, i.e., a tuned mass amplifier, produces higher tactile forces (7.7 times) compared to its counterpart without a mass, while maintaining a low frequency. We optimize the proposed design using a combination of a neural network and sensitivity analysis, and validate the results with experiments on 3-D printed structures. We also study the performance of the device on contact with a soft material, to evaluate the interaction with skin. Potential avenues for future work are also presented, including small form factor wearable haptic devices and remote haptics.

Douleur

The imitation of pain sensation in Virtual Reality is considered valuable for safety education and training but has been seldom studied. This paper presents Douleur, a wearable haptic device that renders intensity-adjustable pain sensations with chemical stimulants. Different from mechanical, thermal, or electric stimulation, chemical-induced pain is more close to burning sensations and long-lasting. Douleur consists of a microfluidic platform that precisely emits capsaicin onto the skin and a microneedling component to help the stimulant penetrate the epidermis layer to activate the trigeminal nerve efficiently. Moreover, it embeds a Peltier module to apply the heating or cooling stimulus to the affected area to adjust the level of pain on the skin. To better understand how people would react to the chemical stimulant, we conducted a first study to quantify the enhancement of the sensation by changing the capsaicin concentration, skin temperature, and time and to determine suitable capsaicin concentration levels. In the second study, we demonstrated that Douleur could render a variety of pain sensations in corresponding virtual reality applications. In sum, Douleur is the first wearable prototype that leverages a combination of capsaicin and Peltier to induce rich pain sensations and opens up a wide range of applications for safety education and more.

Sensitivity to Haptic Sound-Localization Cues at Different Body Locations.

Cochlear implants (CIs) recover hearing in severely to profoundly hearing-impaired people by electrically stimulating the cochlea. While they are extremely effective, spatial hearing is typically severely limited. Recent studies have shown that haptic stimulation can supplement the electrical CI signal (electro-haptic stimulation) and substantially improve sound localization. In haptic sound-localization studies, the signal is extracted from the audio received by behind-the-ear devices and delivered to each wrist. Localization is achieved using tactile intensity differences (TIDs) across the wrists, which match sound intensity differences across the ears (a key sound localization cue). The current study established sensitivity to across-limb TIDs at three candidate locations for a wearable haptic device, namely: the lower tricep and the palmar and dorsal wrist. At all locations, TID sensitivity was similar to the sensitivity to across-ear intensity differences for normal-hearing listeners. This suggests that greater haptic sound-localization accuracy than previously shown can be achieved. The dynamic range was also measured and far exceeded that available through electrical CI stimulation for all of the locations, suggesting that haptic stimulation could provide additional sound-intensity information. These results indicate that an effective haptic aid could be deployed for any of the candidate locations, and could offer a low-cost, non-invasive means of improving outcomes for hearing-impaired listeners.

A Protactile-Inspired Wearable Haptic Device for Capturing the Core Functions of Communication.

In this article, a novel wearable haptic device, to be worn on the hand and forearm, is introduced. Using the modalities of vibration, pressure, and heat application, the device attempts to replicate four core components of communication. The four components - co-presence, phatic communication, back-channeling, and direction giving - are simulated through haptic profiles individually unique to a section or combined as an encompassing system of the device. This paper evaluates the performance of the device through three testing phases with sighted-hearing and DeafBlind individuals. Results indicate that a strong majority of the tested haptic profiles show statistical significance in replication between individuals. This article is unique in its collaboration with the protactile DeafBlind community, individuals who communicate solely through touch, by furthering understanding on how to generate intuitive tactile profiles in wearable haptic devices.