“…Recently, with the advances of dynamics [1,2], navigation [3,4], and sensors [5,6], more civilian applications have been realized for UAVs, such as surveillance [7,8], aerial photography [9,10], search and rescue [11,12], and others. For all of these applications with multiple UAVs, one critical technical problem is that the UAVs may collide with each other in the increasingly dense airspace.…”