Sharp tactile sensation using superposition of vibrotactile stimuli in different phases

The overlapping of vibrations that are in different phases and in close proximity to each other produces a tactile image that is more localized than one produced by pin vibrators. The mechanism behind the former is still unclear; it may be attributed to the fact that the resultant vibration is highly localized and of a high frequency, making the tactile sensations more perceptible by the human hand. In this study, a finite element (FE) model of a human finger is analyzed to investigate the reason for the difference in the sizes of tactile images produced under different mechanical conditions. In the dynamic analysis, we observed the spatial distribution of the strain energy density (SED) in the model and estimated the perceptual area of the mechanical stimuli. To determine the perceptual area, the threshold SED for perceiving the vibratory stimuli was determined by analyzing the FE finger model on a flat vibratory surface. In the deformation analysis results, we observed that the spatial distribution of SED was more localized by the overlapped vibrations than in a pin vibrator. Moreover, spectral analysis revealed that a higher-frequency vibration was generated locally between the two vibrations. A psychophysical experiment was conducted to determine the effect of the high frequency component on detection thresholds.