IEEE Transactions on Haptics最新文献

Thermal-vibration feedback has been reported to elicit the thermal referral phenomenon, offering new possibilities for enhancing user experience. Yet, little research has explored whether thermal referral occurs in the presence of texture-slip feedback. To address this, we developed a custom haptic device capable of delivering integrated thermal and slip feedback to the middle and distal phalanges of an index finger. We primarily estimated the thermal referral occurrence under passive and active touch conditions across two different perceptual experiments, while each further examined its impact on texture perceptions and user experiences (UX). In Perceptual Experiment 1 (passive), we observed the highest occurrence of thermal referral at 40°C (0.86 on a 0-1 scale), and found that referral increased the median of perceived roughness from 43.5 to 60 on a 0-100 scale. In Perceptual Experiment 2 (active), the kinesthetic cues significantly enhanced thermal referral, with the occurrence probability at 24°C increasing to 0.86 compared to 0.51 (0-1 scale) in the first study. In addition, high UX ratings demon strated the applicability of our device to temperature-integrated virtual texture interactions. Our findings expand the scope of thermal referral and highlight the potential for enabling VR users to interact with virtual surfaces that provide temperature cues.

Most commercial prostheses lack a function of natural and intuitive sensory feedback, which is one of the reasons for their high rate of abandonment. Transcutaneous Electrical Nerve Stimulation (TENS) has been proved as an effective approach to evoke sensations for limb amputees. This paper aims to explore the impact of TENS parameters on sensation evoking and evaluate its performance based on behavioral response and EEG data, involving three transradial amputees and seven able-bodied subjects. Experimental results show that the sensation thresholds were predominantly influenced by stimulus amplitude and width, and the sensation intensity increased with the increase of either amplitude or width. Variation of stimulus frequency caused transitions between sensation types, where stimulating at 10 and 100 Hz could achieve stable vibration and pressure sensations for all subjects, respectively. A stimulation encoding strategy was thereupon proposed, where a pressure sensation was to simulate grasp force and the sensation intensity to encode force amplitude. The amputees could achieve a high accuracy rate above 94.4 and 77.8% for sensation type discrimination and intensity grading, respectively, with slightly longer response time than the able-bodied. The obvious cortical activation and clear ERP components demonstrated the reliability of TENS-based sensory feedback, where the N1 component could distinguish different sensation types and intensities (p≤0.05), and the amputees had slower discriminatory responses and weaker activation in sensorimotor cortices than the able-bodied (p≤0.05). This study promisingly confirmed TENS for restoring sensory feedback in limb-amputees, providing a support for closed-loop interactions in amputee-prosthesis systems and even bionic robots.

Microneurography studies have shown that human mechanoreceptor (MR) activity is directionally sensitive to shear forces, enabling fine tactile perception and object manipulation. However, existing computational mechanotransduction models largely neglect this directional tuning, limiting their biological realism and effectiveness for tactile feedback systems such as prosthetic hands. This paper presents a Direction-Dependent Mechanotransduction Model (DDMM) that replicates the direction-specific encoding behavior observed in human tactile afferents. The model integrates multidirectional pressure and shear forces to modulate neural spiking according to the alignment between resultant shear vectors and neuron-specific attenuation profiles. Force inputs are first transformed into afferent-specific currents (SAI, RAI, RAII), which are then converted into spike trains using an Izhikevich neuron model. Simulated fingertip interactions produced directionally selective spiking frequencies ranging from 0 to 47.5 pulses per second, consistent with biological firing ranges. Directional tuning, quantified using the profile-resolved sensitivity index (PRSI), yielded values of 0.31-0.45 for selective and broad profiles, comparable with those experimentally measured directional sensitivity indices (DSI; 0.23 ± 0.18) as reported in the literature. Further experimental validation using triaxial force measurements from human fingertip press-push-lift actions confirm the model's directional sensitivity, with aligned neural attenuation profiles and shear force direction yielding a mean spiking frequency increase of approximately 350% relative to misaligned conditions. These findings establish the DDMM as a biologically inspired and computationally efficient framework for encoding tactile force direction, with potential applications in neuroprosthetics, robotic manipulation, and somatosensory modeling.

Tactile perception varies between individuals and the state of the grasp. To investigate the psychophysical effects on vibrotactile perceptions influenced by grasp type and strength of a handheld device, perceived intensities were tested against various grasp strengths and stimulus levels using 40 and 250 Hz vibrations under power grasp and precision grasp conditions. Grasp strength was measured with a pressure distribution sensor on the cylindrical device capable of presenting vibrations up to approximately 2.0 m/s$^{2}$. The analysis using a physical model supported the measured acceleration characteristics, indicating greater attenuation of low-frequency vibrations due to grasping. The psychophysical experiments indicated that the perceived intensity decreases with grasp strength at 40 Hz vibrations under power grasp, whereas the perceived intensity slightly increases with grasp strength at 250 Hz vibrations under precision grasp. On the other hand, small differences were observed for 40 Hz vibrations during precision grasp and 250 Hz vibrations during power grasp. This highlights the need for compensatory measures in low-frequency vibrations or the use of high-frequency vibrations to achieve consistent vibrotactile feedback in handheld devices across different grasping conditions.

The tactile sensation of towel fabrics, which originates from their pile structure, is strongly affected by the mechanical response under the low loads applied at the instant of contact. The pile structures formed from spun yarns create a graded surface with extremely low elasticity at the outermost layer, complicating the quantitative assessment of tactile properties. This study proposed a quantitative framework for evaluating the tactile performance of ultra-soft textiles using low-load indentation testing and finite element analysis (FEA). Mechanical responses of towel samples were measured through controlled indentation and incorporated into an FEA model simulating skin contact. Stress-based indices-including pressure, principal stresses, Tresca stress, and von Mises stress-were calculated to characterize mechanical stimuli applied to the skin. Correlations between these indices and the initial elastic modulus of the pile structure were examined to identify parameters reliably representing tactile performance. The results show that Tresca and von Mises stresses exhibit strong linear relationships with the structural modulus even under low-stress conditions, highlighting their potential as objective design metrics for developing textiles with targeted tactile qualities. This framework provides a systematic approach for quantitatively linking fabric microstructure to perceived tactile behavior, facilitating design optimization of ultra-soft materials.

Wearable haptic devices face a trade-off between providing rich feedback and preserving natural fingertip sensation. Current multi-DOF systems encumber the fingerpad, interfering with fingerpad sensory capabilities, while lightweight devices offer limited 1-DOF feedback. To address this, we present a 5.24 g, three-degree-of-freedom (3-DOF) haptic device that stimulates mechanoreceptors around the fingernail, leaving the fingerpad unobstructed. It uses two string-pulling motors for distal-proximal feedback and an arc-shaped pin motor for radial-ulnar stimulation to generate directional force vectors. This approach is grounded in the physiology of directionally-sensitive slowly adapting type 2 (SA2) mechanoreceptors. Experimental results demonstrate that the proposed 3-DOF approach improves weight and friction discrimination over single-DOF pressure feedback. Moreover, it delivers directional cues during static contact, a capability absent in vibrotactile systems, and achieves higher overall user satisfaction. By preserving fingertip sensation, the proposed device enables simultaneous interaction with virtual and physical objects, making it suitable for mixed reality applications.

Training for complex motor tasks, such as those encountered in minimally invasive surgery, benefits from effective performance feedback mechanisms to accelerate skill acquisition and ensure retention. Prior work has demonstrated that haptic feedback based on movement smoothness quantified by the metric spectral arc length (SPARC), when provided in real-time as trainees perform complex motor tasks, can cause beneficial changes in task completion strategies resulting in faster completion times without loss of accuracy. The concept of movement smoothness is abstract, however, and more intuitive measures of movement smoothness like idle time and average velocity can be good alternatives to SPARC. Here, we demonstrate the effect of real-time objective performance feedback of movement smoothness, conveyed through a vibrotactile cue encoding alternative measures of movement smoothness, compared to feedback based on SPARC. Subjects receiving smoothness-based feedback based on average velocity performed the task fastest, but their accuracy was lower than the other two groups. We evaluated the effect of removing feedback for additional trials, and showed that performance improvements ceased. After training, the three groups were indistinguishable from each other.

This paper investigates egocentric directional perception of azimuth and elevation in response to torso-based vibrotactile stimuli for both stimulus identification and direction association under a common experimental framework. We conducted four perceptual experiments that examined the two tasks for azimuth and elevation, using real vibrations and illusory stimuli generated by the funneling illusion. The results demonstrated that adding illusory stimuli effectively conveyed directional information with fewer tactors than using only real stimuli. Azimuth perception revealed a lateral bias, whereas elevation perception exhibited a downward bias on the dorsal torso, particularly in the upper back. However, both azimuth and elevation cues were generally consistent across vertical and horizontal torso locations. Additionally, we estimated regression models for both egocentric angles and showed that perceived directions could be estimated from actual stimulus positions. Correlation analysis revealed a weak relationship between azimuth and elevation perceptual errors, suggesting that these dimensions are processed with near-independence. Across all findings, azimuth cues proved to be more effective than elevation cues in conveying directional information. This study provides a comprehensive understanding of egocentric directions and offers practical insights for the design of torso-based vibrotactile displays.

Humans possess an innate ability to seamlessly coordinate movement across multiple limbs, whether driving a motor vehicle, playing a musical instrument, or performing other daily tasks. Here, supplemental sensory information, such as haptic feedback, can enhance this coordination in applications ranging from controlling teleoperated robots to prosthetic limbs and collaborative robotics. Yet, a critical gap remains in our understanding of how visual and haptic information are integrated within sensorimotor feedback systems, as well as the extent to which these sensory channels may serve as substitutes for one another. To address this gap, we conducted an experiment investigating how sensory feedback can be incorporated in a multi-limb coordination task. To determine the degree to which visual or haptic feedback dominates in multi-limb coordination, 25 participants performed a virtual cursor-to-target task using both upper limbs (via a joystick controller) and one lower limb (via a foot pedal controller). Throughout the task, we systematically manipulated visual and haptic feedback, using a vibrotactile haptic feedback algorithm that delivered task-relevant information to all three limbs. We assessed participants' task performance measures relating to trial success rates, completion times, ability to move their limbs in coordination, and overall movement efficiency. Additionally, participants completed a cognitive workload questionnaire to evaluate their perceived task difficulty level and cognitive demands. Our findings indicate that haptic feedback can effectively substitute for one degree of visual information (cursor movement along one axis). We found no significant difference between conditions where all visual cues were presented in the task and the condition where one aspect of visual feedback was replaced by haptic feedback. These results suggest that haptic feedback can, to an extent, serve as a viable alternative to visual feedback in multi-limb coordination tasks.