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Data conversion capability of optical tactile sensor featuring an array of pyramidal projections

In order to enhance robotic tactile sensation, we developed a tactile sensor comprising a flat rubber sheet and an acrylic plate (optical waveguide) featuring an array of pyramidal projections. The back surface of the rubber sheet was checkered with square concave and convex portions. Since each single concave or convex portion was arranged to press the pyramidal projections of 2-by-2 array, the three-dimensional force applied to the back side of the concave and the convex portions could be calculated from the distribution of the four contact areas of the projections. The object's hardness was measured from the difference between the contact areas of concave and convex portions. The three-dimensional coordinates of the object's surface were able to be derived from the contact areas of the entire projected array. Experimental results confirmed that the sensor was capable of perceiving the degree of three-dimensional force applied to the sensor surface as well as the hardness and the radius of the objects being sensed.