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Numerical and experimental study of a three-axis optical tactile sensing system

In this study, we investigated a promising method for measuring three-axis force based on an optical tactile sensing system. Such system consists of a waveguide, an array of tactile cell, a light source and an image sensor (a CCD camera). When the tactile cells are subjected to external forces, the condition for total internal reflection of the attached waveguide is spoiled. The original symmetrical planar waveguide then changes to an asymmetrical one, leading to light leakage in the transverse direction, which is used as the sensing mechanism for the applied forces. A numerical study involving three-dimensional finite element analysis was carried out to study the deformation of tactile cells due to contact forces. A linear relationship between the applied three-axis force and the spot sizes of the image of the leaked light was obtained and validated by experiments.