I. Introduction
With the advancement of electronic, sensor and communication technologies, the performance of the unmanned aerial vehicles (UAVs) system has also made great progress. Due to UAVs’ agility, easy installation, versatility and operation simplicity, they are gradually being used in various tasks, such as search and rescue missions, border surveillance, disaster monitoring and remote sensing. Multiple UAVs systems have many advantages, such as low cost, low mission completion time, better survivability and better scalability [1].