DAA Solution on UTM

Abstract

The hierarchical Unmanned Aircraft System (UAS) Traffic Management (UTM) in Taiwan is constructed for Regional (RUTM under 400 feet) and National (NUTM above 400 feet) operations. The proposed ADS-B Like on-board unit (OBU) broadcasts 90 Byte flight data from UAV to UTM cloud and displays for surveillance. When multiple UAVs are flying in a small airspace, detect and avoid (DAA) mechanism should be activated to ensure flight safety in UTM. The proposed UAV DAA is completed by software in UTM. The DAA is designed referring to traffic alert and collision avoidance system (TCAS) in manned aircraft system to detect the approaching UAVs in the RUTM and identify possible conflict for resolution. UAVs are detected by heading arrow extrapolation for approach to assess possible conflict. A DAA separation bubble is defined by Traffic Advisory (TA) and Resolution Advisory (RA) among multiple targets with estimated time to conflict (TTC). Once the approach proceeds from conflict to collision alert at RA, the UTM controller will use controller to pilot communication (CPC) to notify the less priority UAV pilot to make ways for conflict resolution. In the system implementation, CPC is established using cell phones by 4G or by Zello broadcast. The proposed DAA function has been implemented into Tainan RUTM system with software manipulation and performed passive avoidance for UAVs in real time operation. In RUTM, the surveillance data period is fixed at 8 seconds. The signal delay in ADS-B like system to UTM display is about 0.5~1 second and Zello CPC is measured about 1~2 second delay. The communication time delay is enough to perform RA for avoidance. The ADS-B Like surveillance has counted with 89% reliability to trace UAV flights based on TTC concept. In the verification, ADS-B Like surveillance has been paid attention on reliability to work with the DAA software. From the RUTM operation in Taiwan, the proposed DAA function is preliminarily tested to assure UTM surveillance into better flight safety. The UTM project in Taiwan is continuing to improve operational efficiency and quality.