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arXiv 1801.09780cs.ROcs.AI
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安全可达POMDPs的有界策略综合

Bounded Policy Synthesis for POMDPs with Safe-Reachability Objectives

Rice University(莱斯大学)

Yue Wang, Swarat Chaudhuri, Lydia E. Kavraki

摘要:

在不确定性下规划鲁棒执行是构建自主机器人的基本挑战。部分可观测马尔可夫决策过程(POMDP)为许多应用中的不确定性建模提供了一个标准框架。在这项工作中,我们研究POMDPs的安全可达性的目标,这需要一个概率高于一定的阈值,最终达到一个目标状态,同时保持访问不安全状态的概率低于一定的阈值。这POMDP制定是不同于传统的POMDP模型的最优性目标,我们表明,在某些情况下,安全可达性目标的POMDP可以提供更好的保证安全性和可达性比现有的POMDP模型通过一个例子。POMDP的一个关键算法问题是策略综合,这需要在一个巨大的信念空间(概率分布)上进行推理。为了解决这一挑战,我们引入了一个目标约束的信念空间的概念,其中只包含信念可达到的初始信念下所需的执行,可以实现给定的安全可达性目标。我们的方法competently表示这个空间在一个有界的地平线上使用符号约束,并采用增量可满足性模理论(SMT)求解器,有效地搜索一个有效的policy.We评估我们的方法使用的案例研究,涉及部分可观察的机器人领域与不确定的障碍。结果表明,我们的方法可以合成政策在大的信念空间与少量的SMT求解器调用集中在目标约束的信念空间。

英文摘要:

Planning robust executions under uncertainty is a fundamental challenge for building autonomous robots. Partially Observable Markov Decision Processes (POMDPs) provide a standard framework for modeling uncertainty in many applications. In this work, we study POMDPs with safe-reachability objectives, which require that with a probability above some threshold, a goal state is eventually reached while keeping the probability of visiting unsafe states below some threshold. This POMDP formulation is different from the traditional POMDP models with optimality objectives and we show that in some cases, POMDPs with safe-reachability objectives can provide a better guarantee of both safety and reachability than the existing POMDP models through an example. A key algorithmic problem for POMDPs is policy synthesis, which requires reasoning over a vast space of beliefs (probability distributions). To address this challenge, we introduce the notion of a goal-constrained belief space, which only contains beliefs reachable from the initial belief under desired executions that can achieve the given safe-reachability objective. Our method compactly represents this space over a bounded horizon using symbolic constraints, and employs an incremental Satisfiability Modulo Theories (SMT) solver to efficiently search for a valid policy over it. We evaluate our method using a case study involving a partially observable robotic domain with uncertain obstacles. The results show that our method can synthesize policies over large belief spaces with a small number of SMT solver calls by focusing on the goal-constrained belief space.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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