Next-generation collision avoidance system for unmanned aerial vehicles

Abstract

This paper tackles with a next-generation collision avoidance algorithm for Unmanned Aerial Vehicles (UAVs) based on Traffic alert and Collision Avoidance System - II (TCAS-II) as well as Automatic Dependent Surveillance - Broadcast (ADS-B) information. TCAS-Il plays an important role in the thesis as a main collision avoidance algorithm. Using a TCAS-Il algorithm which is implemented as a computer program on the basis of TCAS-II Minimum Operational Performance Standard, collision avoidance maneuver of typical UAVs in various encounter scenarios is simulated after all TCAS-II commands are converted into an autopilot input. Since the TCAS-II algorithm provides an onboard pilot with vertical avoidance command, the UAVs maneuver vertically according to the altitude command generated to achieve vertical advisories from TCAS-II. In addition, the paper discusses a TCAS-II limitation on some UAVs whose climb or descend rate is relatively low and an alternative method as a complementary algorithm for these vehicles. A new collision avoidance algorithm based on ADS-B information similar to that of TCAS-II is proposed and complements the avoidance logic which is supported by TCAS-II. While an onboard ADS-B system uses other aircraft information from a ground based transceiver, the proposed algorithm is limited to consideration of air-to-air communication between own UAV and intruders. By using the proposed algorithm on the basis of a modified logic, the low-performance UAVs equipped with TCAS-II and the ADS-B system, whose maximum vertical rate is less than the nominal command of TCAS-Il can start avoidance maneuver earlier than TCAS-II equipped vehicles. Therefore, these low-performance vehicles can get a similar vertical separation like high-performance UAVs whose maximum climb rate is higher than 1500 fpm. In the thesis, the UAVs equipped with not only TCAS-II but the ADS-B system also can cope with several types of the intruders including the intruders with a transpo...