Comparison of wide-band vibrotactile and friction modulation surface gratings

TL;DR

This study compares vibrotactile and friction modulation surface gratings, developing two devices to analyze perceptual similarities and physical origins, revealing that out-of-plane velocity predicts intensity and that perception is largely indifferent to actuation mode at high frequencies.

Contribution

The paper introduces two novel single-axis devices for precise comparison of vibrotactile and friction-based gratings, highlighting the role of out-of-plane velocity in perception.

Findings

Out-of-plane velocity predicts vibrotactile intensity.

High perceptual similarity between friction and vibrotactile gratings at high frequencies.

Perception tends to be indifferent to actuation mode in the upper frequency range.

Abstract

This study seeks to understand conditions under which virtual gratings produced via vibrotaction and friction modulation are perceived as similar and to find physical origins in the results. To accomplish this, we developed two single-axis devices, one based on electroadhesion and one based on out-of-plane vibration. The two devices had identical touch surfaces, and the vibrotactile device used a novel closed-loop controller to achieve precise control of out-of-plane plate displacement under varying load conditions across a wide range of frequencies. A first study measured the perceptual intensity equivalence curve of gratings generated under electroadhesion and vibrotaction across the 20-400Hz frequency range. A second study assessed the perceptual similarity between two forms of skin excitation given the same driving frequency and same perceived intensity. Our results indicate that it is largely the out-of-plane velocity that predicts vibrotactile intensity relative to shear forces generated by friction modulation. A high degree of perceptual similarity between gratings generated through friction modulation and through vibrotaction is apparent and tends to scale with actuation frequency suggesting perceptual indifference to the manner of fingerpad actuation in the upper frequency range.