Touch localisation accuracy of OptoSkin optical tactile sensors fabricated from different light-guide materials

Providing feedback information on touch is crucial in human–robot collaboration tasks. Within the framework of the HE SestoSenso project, a novel approach to touch sensing was developed by exploiting the properties of laser beam propagation in light-guide materials, and three different prototype sensory surfaces were fabricated. For the proposed OptoSkin robot-body optical sensor surface, which employs a time-of-flight (ToF) sensor combined with a light-guide material, a performance evaluation was conducted. Using a controlled test robot cell, two experiments were carried out: a field-of-view (FoV) assessment and a localisation accuracy evaluation. Three different prototypes made from optically transparent but distinct materials were examined: acrylic glass, a 3D-printed material, and soft silicone rubber. The localisation evaluation was performed by applying controlled forces with a robot on a rectangular grid, with a raster spacing of 10 mm between individual touch locations. The evaluation results confirm accurate touch localisation, with an error of less than 5 mm and a variability of less than 2 mm in the sensor FoV. The comparison of the OptoSkin prototypes shows the best performance for the soft silicone rubber material and the worst for the 3D-printed material.