This letter presents the dynamic modeling, the gait sequence design, and the control architecture of the BADGER autonomous underground robot. BADGER is a modular and articulated robotic mechanism which employs inchworm biomimetic motion to drill and propel within the soil. It is used to drill and manoeuvre in the subsurface for building curved tunnels of small diameter in underground spaces, without the need for open-cut excavation. In order to design efficient motion control strategies, a model-based approach is followed. To this end, the kinematic and the lagrangian dynamic models are derived, which take into account the physical interaction of the robot drill-head with the environment, and are used for designing the inchworm gait sequence and for calculating the actuation torques and forces required to realise the trajectory profiles of the gait sequence.