  This paper introduces a method for effectively controlling the movement of an
Unmanned Aerial Vehicle (UAV) within a tunnel. The primary challenge of this
problem lies in the UAV's exposure to nonlinear distance-dependent torques and
forces generated by the tunnel walls, along with the need to operate safely
within a defined region while in close proximity to these walls. To address
this problem, the paper proposes the implementation of a Model Predictive
Control (MPC) framework with constraints based on Control Barrier Function
(CBF). The paper approaches the issue in two distinct ways; first, by
maintaining a safe distance from the tunnel walls to avoid the effects of both
the walls and ceiling, and second, by minimizing the distance from the walls to
effectively manage the nonlinear forces associated with close proximity tasks.
Finally, the paper demonstrates the effectiveness of its approach through
testing on simulation for various close proximity trajectories with the
realistic model of aerodynamic disturbances due to the proximity of the ceiling
and boundary walls.
