Using a Small Hexapod Robot to Pick up Large Cylinders for Munitions Response

Abstract

In shallow water environments, traditional technologies face challenges in retrieving unexploded ordnance (UXO). We present an innovative and safe alternative robotic platform to replace traditional divers in this dangerous task. A waterproof 18-DOF legged robot MR. Crab has been developed specifically for the purpose of locating and recovering UXO. Utilizing walking legs for both locomotion and manipulation, the robot demonstrates the capability to pick up inert UXO weighing at 2.78 kg (half of the robot's mass) with one pair of walking legs and 10.5 kg (184% of robot's mass) when utilizing all three pairs of legs. To enhance our understanding of gripping capacity, static analysis was conducted to predict the maximum weight of graspable UXO with respect to UXO radii, revealing that the weight of graspable UXO increases with its radius. A modified wave gait was developed to enable the robot to move while carrying a UXO with its middle pair of legs. For easier control, a user-friendly GUI had been built for remote teleoperation, which also integrated two current sensors to assist human operators in determining the tightness of the UXO grip. Additionally, an automatic gripping algorithm was developed to efficiently place the robot in the optimal gripping position and grab the inert UXO. To validate its performance in real-world environments, MR. Crab was tested at Lake Erie, demonstrating its ability to traverse the wave zone and retrieve a UXO.