  Tactile sensing in mobile robots remains under-explored, mainly due to
challenges related to sensor integration and the complexities of distributed
sensing. In this work, we present a tactile sensing architecture for mobile
robots based on wheel-mounted acoustic waveguides. Our sensor architecture
enables tactile sensing along the entire circumference of a wheel with a single
active component: an off-the-shelf acoustic rangefinder. We present findings
showing that our sensor, mounted on the wheel of a mobile robot, is capable of
discriminating between different terrains, detecting and classifying obstacles
with different geometries, and performing collision detection via contact
localization. We also present a comparison between our sensor and sensors
traditionally used in mobile robots, and point to the potential for sensor
fusion approaches that leverage the unique capabilities of our tactile sensing
architecture. Our findings demonstrate that autonomous mobile robots can
further leverage our sensor architecture for diverse mapping tasks requiring
knowledge of terrain material, surface topology, and underlying structure.
