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arXiv 1607.00562cs.RO
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路径和通信不受限下的多机器人集成任务和运动规划

Integrated Task and Motion Planning for Multiple Robots under Path and Communication Uncertainties

University of Nebraska Omaha(内布拉斯加大学奥马哈分校)

Bradley Woosley, Prithviraj Dasgupta

摘要:

我们考虑一个问题,称为任务排序与路径不确定性(TOP-U),其中多个机器人提供了一组任务位置访问在一个有界的环境中,但一对任务位置之间的路径的长度最初只知道粗略的机器人。机器人的目标是找到任务的顺序,减少路径长度(或能量消耗),以访问任务位置在这种情况下。为了解决这个问题,我们提出了一个抽象的任务可达性图(TRG),集成了任务排序与机器人的路径规划。TRG是动态更新的基础上使用基于采样的运动规划器计算的任务间路径成本,和,一个隐马尔可夫模型(HMM)为基础的技术,计算在当前路径成本的基础上感知的机器人的传感器和任务完成信息从其他机器人的环境的信念。然后,我们描述了一个马尔可夫决策过程(MDP)为基础的算法,可以选择的路径,减少整体路径长度访问的任务位置和协调算法,解决机器人之间的路径冲突。我们已经分析表明,我们的任务选择算法发现的运动规划返回的最低成本路径,并且,我们提出的协调算法是无死锁的。我们还评估了我们的算法在不同环境中的模拟Corobot机器人,同时改变任务位置,障碍物的几何形状和机器人的数量,以及物理Corobot机器人。我们的研究结果表明,基于TRG的方法可以在规划和运动时间,以及重新计划的数量上表现得更好,而与最近的第一,没有不确定性(CFNU)任务选择算法相比,旅行的距离几乎相似。

英文摘要:

We consider a problem called task ordering with path uncertainty (TOP-U) where multiple robots are provided with a set of task locations to visit in a bounded environment, but the length of the path between a pair of task locations is initially known only coarsely by the robots. The objective of the robots is to find the order of tasks that reduces the path length (or, energy expended) to visit the task locations in such a scenario. To solve this problem, we propose an abstraction called a task reachability graph (TRG) that integrates the task ordering with the path planning by the robots. The TRG is updated dynamically based on inter-task path costs calculated using a sampling-based motion planner, and, a Hidden Markov Model (HMM)-based technique that calculates the belief in the current path costs based on the environment perceived by the robot's sensors and task completion information received from other robots. We then describe a Markov Decision Process (MDP)-based algorithm that can select the paths that reduce the overall path length to visit the task locations and a coordination algorithm that resolves path conflicts between robots. We have shown analytically that our task selection algorithm finds the lowest cost path returned by the motion planner, and, that our proposed coordination algorithm is deadlock free. We have also evaluated our algorithm on simulated Corobot robots within different environments while varying the number of task locations, obstacle geometries and number of robots, as well as on physical Corobot robots. Our results show that the TRG-based approach can perform considerably better in planning and locomotion times, and number of re-plans, while traveling almost-similar distances as compared to a closest first, no uncertainty (CFNU) task selection algorithm.

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