Cooperative Path Following Control of Fixed-wing Unmanned Aerial Vehicles with Collision Avoidance

In this paper, we propose a novel curved path following scheme for multiple fixed-wing unmanned aerial vehicles (UAVs) that can achieve coordinated curved path following and handle collision avoidance simultaneously. The proposed solution is a hybrid system that combines a path following strategy and a collision avoidance method to ensure collision-free maneuvering of a group of UAVs cooperative flight. A strategy based on a virtual structure and a kinematic model is proposed to derive the cooperative curved path following. Meanwhile, a possible collision will occur when multi-UAVs flight in the form of dense formations, or there are path intersections when the formation is changed. However, all fixed-wing vehicles need to maintain a minimum airspeed and cannot stop before the collision. Therefore, there is a need for a fast and efficient method that can be implemented online, taking into account the physical limitations of the vehicle (minimum speed, turning rate, etc.) to avoid possible collision. We employ a modified vector field histogram (VFH) method to provide real-time collision avoidance, and evasive maneuvers work only if the distance is within the conflict zone. In order to verify the proposed control scheme, dense formation flight tests of small fixed-wing UAVs were implemented.