  The sense of touch is essential for reliable mapping between the environment
and a robot which interacts physically with objects. Presumably, an artificial
tactile skin would facilitate safe interaction of the robots with the
environment. In this work, we present our color-coded tactile sensor,
incorporating plastic optical fibers (POF), transparent silicone rubber and an
off-the-shelf color camera. Processing electronics are placed away from the
sensing surface to make the sensor robust to harsh environments. Contact
localization is possible thanks to the lower number of light sources compared
to the number of camera POFs. Classical machine learning techniques and a
hierarchical classification scheme were used for contact localization.
Specifically, we generated the mapping from stimulation to sensation of a
robotic perception system using our sensor. We achieved a force sensing range
up to 18 N with the force resolution of around 3.6~N and the spatial resolution
of 8~mm. The color-coded tactile sensor is suitable for tactile exploration and
might enable further innovations in robust tactile sensing.
