Tail-Based Anchoring on Granular Media for Transporting Heavy Payloads

Granular media, like sand, restricts vehicle traction and degrades the ability of mobile robots to pull loads. Solutions that are effective on hard or clean surfaces fail on sand. This work presents a mobile robot system that utilizes an active tail to greatly increase its ability to pull loads. The robot combines dynamic tail impacts, plowing, and leveraging of cable tension to achieve this improved performance. The key contributions of this letter are 1) illustrating how dynamic impacts can provide substantial anchoring force on two terrain types, 2) incorporating anchoring behavior into tail actuator design, 3) combining tail and wheel behaviors to create granular barriers, 4) leveraging geometry to utilize winch tension for enhanced performance, and 5) experimentally demonstrating the ability to transport loads 6x the robot mass on a deep sandy surface. The prototype 7.6 kg robot was able to pull a 45.5 kg load on a deep sand surface. This is a substantial improvement over the baseline robot which was only able to pull a 13.6 kg load.