Abstract: Aiming at the inefficiency and inaccuracy of UAV's three-dimensional path planning in complex environments such as terrain, no-fly zone, meteorology, dangerous object and visual constraints, the paper proposes a fast three-dimensional path planning method for UAV considering complex environmental constraints by designing a multi-layer extended A* algorithm. This method analyses the typical complex environments on the UAV path, and constructs a three-dimensional path planning environment model. By combining with the UAV's own performance constraints, a multi-layer extended A* algorithm is designed for three-dimensional hierarchical expansion to search for the optimal reference path of UAV. Line simplification and line smoothing are used to simplify and optimize the reference path. Finally, the typical case area is selected to carry out the experimental analysis, which proves that the proposed method can quickly and accurately plan the optimal feasible path in complex environment.

Key words: unmanned aerial vehicle 3D path, complex environment constraints, multi-layer extended A* algorithms, fast planning, path optimization