A Frequency-Domain Analysis of Haptic Gratings

Abstract

The detectability and discriminability of virtual haptic gratings were analyzed in the frequency domain. Detection (Exp. 1) and discrimination (Exp. 2) thresholds for virtual haptic gratings were estimated using a force-feedback device that simulated sinusoidal and square-wave gratings with spatial periods from 0.2 to 38.4 mm. The detection threshold results indicated that for spatial periods up to 6.4 mm (i.e., spatial frequencies >0.156 cycle/mm), the detectability of square-wave gratings could be predicted quantitatively from the detection thresholds of their corresponding fundamental components. The discrimination experiment confirmed that at higher spatial frequencies, the square-wave gratings were initially indistinguishable from the corresponding fundamental components until the third harmonics were detectable. At lower spatial frequencies, the third harmonic components of square-wave gratings had lower detection thresholds than the corresponding fundamental components. Therefore, the square-wave gratings were detectable as soon as the third harmonic components were detectable. Results from a third experiment where gratings consisting of two superimposed sinusoidal components were compared (Exp. 3) showed that people were insensitive to the relative phase between the two components. Our results have important implications for engineering applications, where complex haptic signals are transmitted at high update rates over networks with limited bandwidths.

Distinguishability of periodic haptic stimuli in the frequency domain

“…Nevertheless, our results and analysis of %PD do not contradict the observation in literature that frequency components (and subsequently their power contributions) affect haptic stimuli recognition and differentiation using force feedback in a kinesthetic sense [8], and tactile feedback in a cutaneous sense [6]. Using Fourier series approximations of signals, it was shown that signal interpolations can be done in the frequency domain.…”

“…Frequency domain analysis strongly indicated that frequency spectrum components affect detectability and distinguishability of spatial textures. This evidence also suggests that the human somatosensory (touch) system may be capable of performing spectral analysis on spatial haptic stimuli [8]. Applying this investigation to periodic haptic stimuli in the time domain may reveal similar results.…”

Application of Psychophysical Techniques to Haptic Research

“…The three-interval experiment is particularly advisable in an experiment in which it is difficult to label the stimulus alternatives. For example, it might be difficult for a participant to recognize a surface grating as following a sinusoidal or a square-wave profile [66]. It is, however, possible to use the three-interval design in a discrimination experiment in which the participant has to identify only the interval during which the surface grating felt different from the gratings presented during the other two intervals.…”

The Physical Basis of Perceived Roughness in Virtual Sinusoidal Textures

“…That is, does the higher-frequency power contribute at all, or might it even introduce noise and reduce the correlation between power and roughness? Cholewiak et al [34] have shown that higher-frequency components can enhance threshold detection.…”