A Framework for Tactile‐Based Proximity Sensing of Buried Objects via Granular Media Jamming

Many hazardous tasks, such as those related to search and rescue scenarios, involve interactions with granular materials. In such examples, tactile sensing can be invaluable, since objects of interest are often not visible but may still be haptically salient. When a tool, such as a robot finger, approaches a buried object, the displaced granular material ahead of the tool begins to compact against the buried object. The resulting granular media jamming causes an increase in contact force felt on the robot finger without the finger making direct contact with the buried object. In this work, we present a framework for tactile‐based proximity sensing that leverages theoretical models of soil failure during soil‐tool interactions and empirical models of granular material failure zones to haptically detect the onset of granular media jamming and estimate the distance from a sensorized robot fingertip to an object buried in granular material. We investigated the effects of granular material type on proximity sensing accuracy by studying glass beads, poppy seeds, and playground sand. For various fingertip and object depths, we estimated the distance from a sensorized finger to a buried object during haptic exploration in granular materials on a real robot. We developed particle filters to estimate the force state on the robot fingertip in real‐time, and showed how occupancy maps can be continuously updated during haptic exploration within granular materials with a real robot. Our modeling framework can also be leveraged to simulate haptic interactions with granular materials prior to conducting real robot experiments.