• Journal of the Ergonomics Society of Korea
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• v.18 no.3
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• pp.1-12
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• 1999

This study investigated human operator's perceptual and psychophysical responses to vibrotactile stimulation on various parts of the hand. Using a small vibrotactile display, the effects of three mechanical parameters consisting vibrotactile stimulations, i.e., vibration frequency, pulse-width modulation duty cycle, and number of contactors, on differential thresholds were examined at five different loci of the hand. It was observed that differential threshold varies with vibration frequency and number of active contactors. Differential sensitivity was the greatest at the vibration frequency of 120 Hz. The differential sensitivity was not found to be affected by loci on the hand. The area of stimulation on the hand was also found to be significant in that the sensitivity increased with the number of active contactors. It should be noted that the conclusions from this study generally correspond to those from the previous study on the absolute sensitivity. which means that tactile sensitivity to vibrotactile stimulations can be controlled with a systematic and consistent passion for emulating normal everyday contact on human hands in teleoperation and virtual reality applications.

• Journal of the Ergonomics Society of Korea
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• v.17 no.2
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• pp.1-10
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• 1998

The objective of this study is to investigate hwnan operator's perceptual and psychophysical responses to vibrotactile stimulation on various parts of the hand. Using a small vibrotactile display, five different loci of the hand along with two other mechanical parameters consisting vibrotactile stimulations, which are vibration frequency and number of active contactors, were examined for the effects on absolute thresholds. All test variables were found to have significant effects on thresholds. It was observed that absolute threshold is a function of vibration frequency and number of active contactors. Tactile sensitivity was the greatest at the vibration frequency of 240 Hz, and the fingertip was found to be the most sensitive locus on the hand. The area of stimulation on the hand was also found to be significant in that the sensitivity increased with the number of active contactors. The results of the study generally supported those of other previous studies. It should also be noted, however, that the conclusions from the study should be limited to the absolute sensitivity, not to the suprathreshold intensities of normal everyday contact with the hands.

• Journal of the Ergonomics Society of Korea
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• v.32 no.4
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• pp.355-361
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• 2013

Objective: The aim of this study is to investigate the gender-differences in vibrotactile responses(sensitivity and displeasure) of residual forearm simulated by vibration stimulation in upper limb(trans-radial) amputees. Background: Several studies have reported that vibration stimulation using the haptic vibrator is one the most effective methods for delivering sensation to an amputees. However, few studies have reported the perception to haptic vibratory stimulus, particularly sensitivity and displeasure. Method: We set up a custom-made vibration stimulation system that included 6 actuators(3 medial parts and 3 lateral parts) and a graphical user interface(GUI)-based acquisition system to investigate changes in residual somatosensory sensibility and displeasure in the forearm of upper limb(trans-radial) amputees. Vibration actuators were attached at the 25%-point on the proximal forearm. Stimulation with 32Hz, 64Hz, or 149Hz of frequency was used for the sensitivity tests and with 32~257Hz of frequency was used for the discomfort experiments. The subjective responses were evaluated on a 10 point scale. Results: The results showed that vibrotactile sensory perception in male amputees were higher than that in female amputees. In male amputees, the response at lateral area of forearm was the most sensitive than medial area; but, female amputees showed similar sensitive areas. Subjects did not experience any discomfort during vibrotactile stimuli. Conclusion: Vibrotactile response in the amputees was dependent on gender as well as area stimulated by vibration. Application: The results might contribute to develop the vibrotactile feedback system for the amputees.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.8
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• pp.795-800
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• 2014

In this paper, a vibrotactile pad system, T-mobile, is developed to provide vibrotactile cues for hand-held devices. A grooved and slim design is adapted to the back-side plane of the T-mobile, and the contact part consists of 12 vibrotactile panels which can operate independently and separately. To be isolated among vibrotactile actuators, the surface of the cover is divided into several pieces. Each vibrating module consists of a linear resonant actuator, a section of covering surface, and a vibration isolator. In order to provide spatial and directional information, sensory saltation and phantom sensation are applied to the T-mobile. To evaluate the developed device, two experiments were conducted to test whether directional information and spatial information can be successfully displayed by the device. Additionally, in order to find optimal stimulation by sensory saltation, an empirical test was conducted. As a result, spatial and directional information would be useful for displaying intuitive information for hand-held devices with vibrotactile feedback and reasonable near-optimal value for sensory saltation was obtained.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.7
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• pp.705-710
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• 2012

Research involving discomfort or pain related to haptic vibratory stimulation the for prosthesis users of myoelectrical hand is very lacking. Our objective of this study was to evaluate the displeasure and sensitivity of areas in forearm using vibration stimulation system between upper limb amputees and non-amputees. Twenty transradial amputees and forty non-amputees (20 youth, 20 elderly) were involved. We set up custom-made vibration stimulation system including eight actuators (4 medial parts and 4 lateral parts) and GUI-based acquisition system, to investigate changes of residual somatosensory sensibility and displeasure at proximal 25% of forearm. Eight vibration actuators were attached to the circumference of proximal 25% point of forearm at regular intervals. Sensitivity tests were used to stimulate the 120Hz and discomfort experiment was used to 37 ~ 223Hz. The subjective responses were evaluated by 10 point scale. The results showed that both groups were similar in sensitive areas. Response at around of radius was most sensitive than other areas in all subjects. Elderly group do not appear discomfort of vibrotactile; however, youth group and amputee presented discomfort of vibrotactile. Prosthesis with a vibrotactile feedback system should be developed considering the sensitivity. Furthermore, Future studies should investigate the scope of application of that principle.

• Progress in Medical Physics
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• v.15 no.3
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• pp.128-133
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• 2004

The fMRI response of the somatosensory cortex was investigated with vibrotactile stimulation. Three different frequencies of 8, 15, or 25 Hz were applied in order to mainly focus on the hemodynamic response of Meissner corpuscles sensitive to frequencies of 5-40 Hz. A closed-system, pneumatically-driven, rubber diaphragm was fabricated that overcame many of the limitations of existing vibrotactile devices and produced robust sensory cortex activation in an fMRI experiment. Increasing frequency vs. activation area was analyzed in terms of signal percent change and number of pixels. Our preliminary results indicated that the distribution of the signal percentage change widened and more activated pixels were obtained with higher frequencies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1619-1620
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• 2013

• Progress in Medical Physics
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• v.17 no.3
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• pp.159-166
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• 2006

The nonlinearity of hemodynamic response in the somatosensory cortex was investigated with vibrotactile stimulation. The stimuli consisted of a train of 25 Hz, each tasting five different duration periods, 2 s, 4 s, 8 s 12 s, or 16 s with 20 sec periods of no vibration in a pseudo-random order. In order to understand the linearity on the change of stimulus duration for somatosensory cortex, two different tests- checking the linearity of system and finding the impulse response function from gamma-variate function were applied to analyze the hemodynamic response functions. They have produced nearly same results. The BOLD response in the somatosensory cortex Is nonlinear for stimuli of less than 8 seconds, but nearly linear for stimuli greater than 8 seconds. The amplitude, area, TTP, and FWHM as functions of the stimulus duration were calculated and showed a significant downward trend with Increasing stimulus duration for the amplitude and the area. It supports the ranges of nonlinearity are less than 8 seconds.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.881-886
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• 2007

This study was to develope a vibrotactile display system using windows media player from digital audio signal. WMPlayer10SDK system which was plug-in tool by microsoft windows media player provided its video and audio signal information. The audio signal was tried to be change into vibrotactile display. Audio signal had 4 sections such as 8bit, 16bit, 24bit, and 32bit. Each section was computed its frequency and vibrato scale. And data was transferred to 38400bps network port(COM1) for vibration. Using this system was able to develop the music suit which presented tactile feeling of music beyond sound. Therefore, it may provide cross modal technology for fusion technology of human senses.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.11
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• pp.3064-3082
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• 2023

During the last decade, several Electronic Orientation Aids devices have been proposed to solve the autonomy problems of visually impaired people. When hearing is considered the primary sense for Visually Impaired people (VI) and it is generally loaded with the environment, the use of tactile sense can be considered a solution to transmit directional information. This paper presents a new wearable haptic system based on four motors implemented in shoes, while six directions can be played. This study aims to introduce an interface design and investigate an appropriate means of spatial information delivery through haptic sense. The first experiment of the proposed system was performed with 15 users in an indoor environment. The results showed that the users were able to recognize, with high accuracy, the directions displayed on their feet. The second experiment was conducted in an outdoor environment with five blindfolded users who were guided along 120 meters. The users, guided only by the haptic system, successfully reached their destinations. The potential of tactile-foot stimulation to help VI understand Electronic Orientation Aids (EOA) instructions was discussed, and future challenges were defined.