  In this paper, an algorithm for Unmanned Aircraft Systems Traffic Management
(UTM) for a finite number of unmanned aerial vehicles (UAVs) is proposed. This
algorithm is developed by combining the Rapidly-Exploring Random Trees (RRT)
and Velocity Obstacle (VO) algorithms and is referred to as the RRT-VO UTM
algorithm. Here, the RRT algorithm works offline to generate obstacle-free
waypoints in a given environment with known static obstacles. The VO algorithm,
on the other hand, operates online to avoid collisions with other UAVS and
known static obstacles. The boundary of the static obstacles are approximated
by small circles to facilitate the formulation of VO algorithm. The proposed
algorithm's performance is evaluated using numerical simulation and then
compared to the well-known artificial potential field (APF) algorithm for
collision avoidance. The advantages of the proposed method are clearly shown in
terms of lower path length and collision avoidance capabilities for a
challenging scenario.
