Tangent-Based Method for Collision Detection and Avoidance System for UAVs using ADS-B Transponder and ADS-B Like Solution

This paper discusses a target-based collision avoidance method to avoid velocity-dependent ellipsoid geometry for high-density ADS-B traffic areas. A velocity-dependent energy function constrains the possible altitudes based on a predetermined post-maneuver velocity. This method allows the aircraft maneuvers to be constrained to the physical limits of the ownship, optimizing aircraft energy retention. Using velocity-based extrapolation of the ownship and intruder aircraft positions obtained from ADS-B or custom ADS-B solution data, a future collision may be predicted. In a predetermined period before the estimated collision, the positions of the two aircraft are considered to be static, and a corrective trajectory is generated. The corrective trajectory is calculated through a tangent plane on the velocity-dependent ellipsoid region surrounding the intruder. The tangent plane's surface contains the current location of the ownship, as well as the location of the target maneuver position. Then, the closest of the two avoidance waypoints is selected, the angles relative to the aircraft's current heading are calculated, and commands are issued to reach the new specified attitude. The developed algorithm was tested in simulation prior to flight testing. Simulation and flight test results are shown.