Sense and avoid for unmanned aerial vehicles using ADS-B

Sense-and-avoid is an indispensible ability for Unmanned Aerial Vehicles (UAVs) to be integrated into the civil airspace. This paper presents the design and implementation of a real-time path planning algorithm for the UAVs to avoid moving obstacles. Automatic Dependent Surveillance- Broadcast (ADS-B) is used for obstacle detection. The moving obstacles are assumed to be indifferent to the UAV. The UAV needs to fly through pre-assigned waypoint sequence. If a collision with an obstacle is predicted, an avoidance path is generated by a method based on Closed-Loop Rapidly Exploring Random Tree (CL-RRT) [1]. After that, a collision check is performed on the generated path when the states of the UAV and the obstacles are updated. The path will be re-planned if it leads to a collision. Linear extrapolation and reachability set are used to predict the obstacles' motion. The algorithm was validated in Software In the Loop Simulation (SITL). Logged ADS-B aircraft trajectory were used as the moving obstacles.