Soft, round, high resolution tactile fingertip sensors for dexterous robotic manipulation

Abstract

In this work we introduce a non-planar soft high-resolution tactile sensor. An iteration of the GelSight sensors, it enables future GelSights to have more complicated form factors, such as a humanoid fingertip. To do this we introduce a novel method for achieving directional lighting along the entirety of a curved sensor using light piping. Light piping uses total internal reflection and a semi-specular membrane to constrain the path of the light inside the sensor until the sensing membrane is deformed. By using this new membrane and changing the geometry, we introduce a new bidirectional reflectance distribution function and new optics. This require new calibration procedures in the form of developing a fisheye projection model, and developing a neighborhood and location based continuous look-up table to map the relationship between RGB value and surface normal orientation of the membrane at a point. Finally we perform two dexterous manipulation task with feedback from the sensors in the form of controlled rolling of an object on a support surface, and lid removal off a jar. We also give instructions on how to manufacture the sensor as well as increasing the durability of the membrane for all GelSight sensors.