I. Introduction
With the rapid development of UAV technology and Internet of things technology, UAVs are widely used in military and civil fields [1]. Compared with the manned aerial vehicles, the UAVs have a great advantage in the complex and dangerous environment. However, due to the limitations of UAVs' own energy consumption, flight performance, load capacity and other factors [2], it is necessary to plan a safe and low-cost flight path for the UAV.