Virtual pebble: A haptic state display for pedestrians

We present a wearable haptic feedback device for the foot, which gives the sensation of a small pebble in a shoe when actuated and no sensation otherwise. Because it stimulates slowly-adapting as well as fast-adapting mechanoreceptors it is useful for displaying a condition that may persist over time, as well as the occurrence of an event. The feedback, which we call the “virtual pebble” due to its ability to appear on command, is intended as a complement to vibration feedback. We performed a user study to quantify perception accuracy during standing, walking, and jogging for haptic feedback combinations on the foot and knee from vibrotactors and the virtual pebble. We also quantified absolute perception thresholds for single vibration and virtual pebble actuations. Results show that subjects are able to correctly perceive a combination of the pebble and vibration much more accurately than a combination of two vibrations. In addition, subjects are most sensitive to vibration feedback while stationary but most sensitive to virtual pebble feedback while jogging. These findings suggest that the virtual pebble is useful as an additional channel of haptic feedback during ambulatory locomotion.