Research On On-line Cooperative Path Planning For Multi-UVA Formation

With the flourish development of modern high science and technology and the increasing requirement for military affairs and politics, it has been one of the hot spots in recent years, that multi-agent path planning algorithms are used to carry out the research on path planning for unmanned aerial vehicle(UAV). At present, facing sudden threat, it is necessary for UAV to have the ability of dynamic path planning in order to improve the battlefield adaptability and viability. As a common multi-agent path planning algorithm, the artificial potential field method has the characteristics of good real-time performance and fast planning speed. However, when it is applied to the Multi-UAV path planning, some problems still need to be solved, such as goals unreachable, falling easily into local minimum, unable to maintain formation, no evaluation mechanism of path planning, etc. In this paper, the traditional artificial potential field method is improved to deal with the above problems and a hierarchical potential field method of path planning for UAV is proposed. This method is applied to dynamic path planning for Multi-UAV formation and the numerical simulation experiment of path planning for Multi-UAV formation in naval battlefield is carried out. The main contributions of this paper can be summarized as follows:1. The modeling method of threat factors and environmental factors in battlefield is studied. According to the defense system of enemy aircraft carrier formation, the threat factors in the process of on-line cooperative path planning for Multi-UAV formation are divided into two major categories: detection threat and the fire threat. In addition, the environmental factors in the battlefield space are considered. In order to verity the proposed path planning algorithm easily, the models are simplified and it lays the foundation for the simulation research of Multi-UAV path planning in naval battlefield.2. Based on the analysis of the traditional artificial potential field model, an improved potential field method applied to path planning of UAV is proposed. Traditional potential function is modified with segmentation principle to solve the problem of goals unreachable. Rotational force is introduced in the calculation of the resultant force to solve the problem of falling easily into local minimum. Forces between UAVs are introduced in the calculation of the resultant force to solve the problem of collision between each other in the process of formation flying and the problem of unable to maintain formation. Through the simulation, the improved artificial potential field method has been proved to have good effect.3. Based on the above improved potential field method, introducing evaluation mechanism of path planning, a hierarchical potential field method applied to path planning of UAV is proposed. With the improved potential field method as the core, the multilevel and multidirectional path lattice are established combined with hierarchical thinking. With the shortest path and the minimum threat as the target, the path planning problem is transformed into a multi objective optimization problem. In order to facilitate the solution, further the multi objective optimization problem is transformed into a single objective optimization problem through weighting method. The best path point is selected from the path lattice by choosing the weight eclectically and finally the path is generated in order to make up the defect, that advantages or disadvantages of path can’t be identified by using traditional artificial potential field method. Through numerical simulations by choosing different objectives’ weights, the effectiveness and feasibility of this method is verified. In addition, the traditional potential field method, the improved potential field method and the hierarchical potential field method are compared by simulations. Simulation results show that the proposed hierarchical field method owns obvious advantages. This method not only has universal applicability, but also can be applied to other fields.4. The numerical simulation experiment of path planning for Multi-UAV formation in naval battlefield is carried out. Considering the threat factors and environmental factors in the battlefield, the proposed hierarchical field method is applied to Multi-UAV formation to carry out the research about the static cooperative path planning and the on-line cooperative path planning in naval battlefield. Simulation results show that the hierarchical potential field method can be applied preferably to the dynamic path planning of Multi-UAV formation. Meanwhile various threats are avoided and the formation is kept better. The effectiveness and feasibility of this algorithm is verified further.