Detection of Friction-Modulated Textures is Limited by Vibrotactile Sensitivity

Abstract

Modulation of the frictional force of a fingertip sliding over a surface-haptic device can produce compelling sensations of texture and relief. The virtual sensation is particularly apparent and feel as fixed in space if the stimulus is rigorously correlated with the displacement of the finger. While frictional textures tactually resemble their real counterparts, some exploratory conditions under which the sharpness of the texture declines exist. We postulate that this decline in sharpness is caused by the perceptual limitation of the attempt to interpret the variation in friction as an out-of-plane sinusoidal topography. To investigate these questions, we measured the detection thresholds of sinusoidal friction-modulated gratings for a wide range of spatial periods explored at two different speeds. We compared the results with the detection thresholds, reported in the literature, of real gratings and vibrotactile stimuli. We found that the detection of spatial friction-modulated textures does not follow the same trend as that of real textures but is more similar to the vibrotactile rendering, which is strongly influenced by the exploratory speed. This study provides a better understanding of the perception of friction-modulated textures and provides insight into how to design impactful stimuli on surface-haptic devices.

The Biomechanics of the Tactile Perception of Friction

“…The evolution of the normal and tangential forces was measured with a custom-built tribometer. The tribometer relied on a rigid elastic structure, which nanometre-scale deformation was measured via a Fabry-Perot interferometer, see [18] for construction details. This high-precision sensor can resolve forces with amplitudes lower than 1 mN.…”

Estimating Friction Modulation From the Ultrasonic Mechanical Impedance

“…The input voltage into the piezoelectric actuators and plate vibrations were measured with an acquisition card (NI USB-6211 National Instruments) at a 100 kHz sampling rate, providing approximately 3 points per cycle. Lateral and normal forces imposed by the user on the plate were measured with the custom force sensor described in [36] and shown in Fig. 10 at a 10 kHz sampling rate.…”

Phononic Crystals Applied to Localised Surface Haptics

“…Biotribometers are designed to record artifact-free frictional forces. Instead, most suffer from normal modes between 300 Hz and 600 Hz [24]- [26], although reconstruction filters can, in some cases, further extend the usable bandwidth up to 1.3 kHz [26]. [10].…”