This paper proposes a method for planning the three-dimensional path for low-flying unmanned aerial vehicle (UAV) in complex terrain based on interfered fluid dynamical system (IFDS) and the theory of obstacle avoidance by the flowing stream. With no requirement of solutions to fluid equations under complex boundary conditions, the proposed method is suitable for situations with complex terrain and different shapes of obstacles. Firstly, by transforming the mountains, radar and anti-aircraft fire in complex terrain into cylindrical, conical, spherical, parallelepiped obstacles and their combinations, the 3D low-flying path planning problem is turned into solving streamlines for obstacle avoidance by fluid flow. Secondly, on the basis of a unified mathematical expression of typical obstacle shapes including sphere, cylinder, cone and parallelepiped, the modulation matrix for interfered fluid dynamical system is constructed and 3D streamlines around a single obstacle are obtained. Solutions to streamlines with multiple obstacles are then derived using weighted average of the velocity field. Thirdly, extra control force method and virtual obstacle method are proposed to deal with the stagnation point and the case of obstacles' overlapping respectively. Finally, taking path length and flight height as sub-goals, genetic algorithm (GA) is used to obtain optimal 3D path under the maneuverability constraints of the UAV. Simulation results show that the environmental modeling is simple and the path is smooth and suitable for UAV. Theoretical proof is also presented to show that the proposed method has no effect on the characteristics of fluid avoiding obstacles. ª 2015 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.
This paper presents a geometrical path planning method, and it can help unmanned aerial vehicle to find a collision-free path in two-dimensional and three-dimensional (2D and 3D) complex environment quickly. First, a list of tree is designed to describe obstacles, and it is used to query the obstacles which block the line from starting point to finishing point (blocking obstacle). Specially, the list also stores the edge information of blocking obstacle. For the obstacles with short distance, a reasonable way to fly over is studied. Then, a shortest path planning method based on geometrical computation is proposed according to different shapes of obstacles. The obstacles are convex and divided into two cases of 2D and 3D. 2D environment includes rectangular obstacle, trapezoidal obstacle, triangular obstacle, circular obstacle and elliptic obstacle. In 3D, it includes cuboid, sphere and ellipsoid. To compare with other methods, the simulation is made in different environments. In 2D environment with circular obstacles, the method is similar to the artificial potential field. In 2D environment with rectangular obstacles, the performance of the proposed method is better than A-star. Compared with genetic algorithm, the proposed method gives a better result in 3D environment with cuboid obstacles. In 3D environment with hybrid obstacles, it is similar to interfered fluid dynamical system. Through comprehensive comparison and analysis, the conclusion is that the method has good adaptability and does not require grid modeling. It can find a shorter path in 2D/3D complex environment within a short time, so it has the ability of real-time path planning. Keywords Unmanned aerial vehicle (UAV) • Path planning • Geometrical shortest path • 2D/3D complex environment • Convex obstacles • Optimal and real-time planning B Xiao Liang
Using the characteristics of unmanned aerial vehicle/unmanned ground vehicle, heterogeneous systems can accomplish many complex tasks cooperatively. Moving target tracking is an important basis for the relative positioning and formation maintenance of heterogeneous cooperative systems. This paper first introduces the unmanned aerial vehicle/unmanned ground vehicle collaborative tracking task and heterogeneous system. In order to maintain the original stability of unmanned aerial vehicle, a control method based on SBUS protocol to simulate remote control is proposed. About unmanned ground vehicle with Mecanum wheel, a detailed description of control method is designed. For the problems of real-time performance and occlusion, a tracking scheme based on AprilTag identification is studied. The scheme tracks the Tag target in the case of no occlusion. When occlusion occurs, the scheme tracks the color feature around the Tag. The accuracy of the tracking algorithm and the problem of occlusion are greatly improved. Finally, the scheme is applied to the heterogeneous systems. Simulation and experimental results show that the proposed method is suitable for unmanned aerial vehicle/unmanned ground vehicle heterogeneous system to perform the collaborative tracking task.
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