UAV sense and avoidance: concepts, technologies, and systems

Unmanned aerial vehicle (UAV) sense and avoidance is one of the core technologies for integrating UAV into airspace, and it is a significant symbol of UAV autonomy and intelligence. Critical technologies and systems have been gradually developed over the past few years. We review studies related to the concept, techniques, and systems on UAV sense and avoidance, which is based on policies, regulations, and techniques. Moreover, we review the environment sensing technology related to collision avoidance path planning and maneuver control. We also propose two different systematic levels of sense-and-avoid (SAA) considering the differences in platform properties, application scenarios, and operational manners of the large/middle-sized and small/micro-sized UAVs. Furthermore, two different system paradigms, i.e., the hierarchical paradigm and reactive paradigm, are proposed to guide the system design of SAA. Finally, our study provides the prospect of sense and avoidance based on policies and regulations, technologies, and system design.