A basic study on tactile displays using velvet hand illusion

To enhance artificial tactile sensation generated by a tactile display, we focus on the velvet hand illusion (VHI), in which a person rubs his/her hands together on either side of wires strung through a frame, producing the sensation of rubbing a very smooth and soft surface like velvet. To determine the specifications of an actuator for a tactile display enhanced by VHI, we investigate the relationship between wire distance and intensity of illusionary sensation using a series of psychophysical experiments. According to the experimental results, the strength of VHI depends on the distance between two adjacent wires and saturates at around 55 mm. In VHI, although the area bounded by two wires moves relative to the hands, tangential force does not occur on either hand, causing operators to experience the illusion of touching a smooth virtual film with a zero coefficient of friction. Since the strength of VHI becomes small for a small distance between two adjacent wires, excessive tangential stimulation prevents the occurrence of VHI. Therefore, VHI control requires two actuations: one is for normal actuation on the operator's finger surface to generate a touch feeling; the other is appropriate tangential actuation to generate a moving-edge feeling on the operator's finger surface.