DEM-MBD Coupled Simulation of a Burrowing Robot in Dry Sand

This study demonstrates the application of a coupled discrete element method (DEM)–multi-body dynamics (MBD) framework in simulating the self-burrowing behavior of a robot in dry sand. In robotics, a robot can be modeled using MBD, in which each component of the robot is modeled as interconnected rigid or flexible bodies whose motions obey the laws of motion and are limited by kinematic constraints. In this study, DEM is coupled to MBD using Chrono—an open-source physics engine—to model the self-burrowing behavior of a two-auger robot in dry sand. The robot consists of a pair of horizontally aligned, auger-shaped bodies, which are connected with two rotational motors in MBD; and the sand is simulated as packing of monodispersed, frictional spheres in DEM. A typical co-simulation loop starts with the DEM module that solves the inter-particle and particle-structure forces and displacements; the particle-structure forces are then transferred to the MBD module to solve the dynamics of the robot; with the updated robot position and velocity, information is then transferred back to the DEM module. The rotation of the augers was set to different directions and speeds. It was found that the rotation of the two augers in the same direction enables horizontal translational movement of the robot, while rotation in the opposite directions hinders such movement: higher rotational speeds lead to higher translational velocities.