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摘要:
平流层浮空器是开展临近空间应用的重要平台,其在不确定风场中的路径规划是开展应用的关键。研究对象是具有一定水平驱动能力的平流层浮空器,针对其低动态、大尺寸及易受风场影响等特点,基于马尔可夫决策过程(MDP)提出一种浮空器在不确定风场作用下的二维全局路径规划方法,寻找由当前位置快速部署到目标区域所需时间最短的最优路径。由于风场中可能存在误差,将风场不确定性引入MDP模型中,设计相关模型参数,建立确定风场和不确定风场2种环境模型。通过仿真,分析具有不同驱动能力的浮空器在2种风场模型下的区域可达性、最优路径和最优动作序列的选择,结果表明:最优路径和最优动作会根据起始点/目标点位置、浮空器水平驱动能力及风场模型的不同发生比较大的变化;浮空器的水平驱动能力越强,区域可达性越高,2种风场模型对浮空器的二维全局路径规划影响的差异也随之减弱。
Abstract:The path planning in an unknown wind field is the main application challenge for stratospheric aerostats, which are a crucial platform for exploring the region of near space. The research object of this paper is stratospheric aerostat with certain horizontal actuation which are encountered with low dynamic, huge structural scale and the flight performance significantly affected by environmental wind field. An approach of two-dimensional global path planning based on the Markov decision process (MDP) in the wind field is presented, in which the problem of path planning is regarded as looking for the optimal path with the shortest time required for rapid deployment from the current location to the target. The actual wind vector field is not known exactly and may deviate significantly from the wind velocities estimated by the model. Since the exact wind vector field is unknown, it is possible that it will differ greatly from the model's predicted wind velocities. To address this issue, our technique explicitly incorporates wind uncertainty into the path planning algorithm, and designs the related parameters of approach in order to establish the determined wind field model and the uncertain wind field model . To solve this problem, we developed a method that explicitly accounts for wind uncertainty in the path planning algorithm and designs the relevant approach parameters to create both a determined wind field model and an uncertain wind field model. The reachability of aerostat with horizontal actuation in a given region relative to the target under different wind field models is compared, in addition, the shortest flight time path and the optimal action sequences are planned. The numerical simulations show that the optional path and actions sequence change with difference of the positions of start/target, the horizontal actuations and wind field models. The numerical simulations also show that the regional accessibility enlarges and the difference of the influence between two wind field models on the two-dimensional global path planning of the aerostat decreases with increase of the horizontal actuation of the aerostat.
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