  Micro Aerial Vehicles (MAVs) navigation in subterranean environments is
gaining attention in the field of aerial robotics, however there are still
multiple challenges for collision free navigation in such harsh environments.
This article proposes a novel baseline solution for collision free navigation
with Nonlinear Model Predictive Control (NMPC). In the proposed method, the MAV
is considered as a floating object, where the velocities on the $x$, $y$ axes
and the position on altitude are the references for the NMPC to navigate along
the tunnel, while the NMPC avoids the collision by considering kinematics of
the obstacles based on measurements from a 2D lidar. Moreover, a novel approach
for correcting the heading of the MAV towards the center of the mine tunnel is
proposed, while the efficacy of the suggested framework has been evaluated in
multiple field trials in an underground mine in Sweden.
