Surface Tilt Perception with a Biomimetic Tactile Sensor

Humans are known to be good at manipulating tools. To cope with disturbances and uncertainties from the external environment during such tasks, they must be able to perceive small changes in orientation or tilt of the tool using mechanoreceptors in the glabrous skin of the fingertips. We hypothesize that the most sensitive part of human fingers, a flat surface on the distal phalanx (called apical tuft) would be preferred for perceiving very fine tilts. In this paper, we used an experimental apparatus to quantify discrimination threshold of a biomimetic tactile sensor (BioTac (R)) that incorporates a similar, sensorized flat surface. We found the thresholds to be as small as 0.11 degrees for tilts in the roll direction and 0.19 degrees for tilts in the pitch direction. The flat surface was superior in detecting tilts when compared to other, curved locations on the BioTac.