Design, modeling, and optimization of a Frustrated Total Internal Reflection (FTIR)-based tactile force sensor

The design, modeling, and experimental evaluation of a tactile force sensor utilizing the principle of Frustrated Total Internal Reflection (FTIR) is presented. The sensor device consists of a waveguide, a silicone probe, a light detector, and an LED source. The study begins with a comprehensive material selection process aimed at identifying optimal optical and mechanical properties to ensure efficient light transmission under applied pressure. Hertzian contact theory and a linear-isotropic finite element model are employed to simulate the mechanical interaction between the probe and the waveguide. Finite element method (FEM) simulations are then conducted to compare the numerical and analytical results and to analyze the sensor's static and dynamic responses under various conditions. An optimized configuration featuring three detectors and multiple probe geometries is proposed to achieve a consistent correlation between applied force and optical output. The FEM results are compared with experimental measurements. Additional experimental investigations, including static calibration, hysteresis, repeatability, drift, and dynamic tests, are performed to assess the sensor's stability and reliability under cyclic loading. The findings confirm that the developed FTIR-based tactile sensor exhibits adequate sensitivity, strong repeatability, and stable performance, demonstrating its potential for practical tactile sensing applications.