抄録
Abstract An optical three-axis tactile sensor is comprised of a silicone-rubber sheet, an acrylic plate, a CCD camera and a light source. A silicone-rubber sheet has an array of 8×9 sensor cells consisting of a columnar feeler and conical feelers. Since the 2-by-2 conical feelers were detached from the acrylic board under too large horizontal force, the three-axis tactile sensor could detect friction coefficient of the object surface with limited range of shearing force only in the preceding authors' studies In the present paper, the authors proposed a new sensing element which has a columnar feeler and 8 conical feelers. The authors formulated a set of equations which could evaluate normal and shearing forces from integrated gray scale value and centroid displacement caused by conical feeler's contacts. To evaluate these sensing elements, we conducted a series of experiments using an x-z stage and a two-axis force sensor. It was found that relationship between centroid displacement and shearing force does not depend upon applied normal force, and that the present equations can estimate variations in normal force induced by increase of shearing force.
