arXiv:2411.14165cs.RO2024-11被引 5

形式化了带状态的行动树,可验证机器人任务规划的安全性。

Formalizing Stateful Behavior Trees

  • 引入带共享内存的有状态行为树,支持持久变量与动态环境。
  • 当变量为无界整数时,计算能力等同于图灵机;有限类型时等同于有限自动机。
  • 开发专用语言和工具链,支持模型检查与代码生成,验证效率提升100倍。

行为树(BTs)是广泛用于各类规划任务的高层控制器,正逐渐应用于机器人任务规划。随着其在安全关键领域的重要性上升,对行为树的语法、语义进行形式化并验证其性质变得至关重要。本文形式化了一类称为有状态行为树(SBTs)的树结构,它们拥有辅助变量,并能在随时间变化的环境中运行。SBTs通过共享内存(常称黑板)存储这些辅助变量。我们证明,当黑板可存储数学意义上的无界整数时,SBTs的计算能力等同于图灵机。此外,在辅助变量为有限类型的情况下,其计算能力等同于有限状态自动机。本文提出一种针对SBTs的领域特定语言(DSL),并适配工具BehaVerify以支持该语言。新工具链支持与Python中流行的BT库对接,还能生成Haskell代码和nuXmv模型,后者用于对SBTs进行时序逻辑的模型检查。文中提供了实例与可扩展性测试,结果显示BehaVerify的验证速度比另一工具快100倍。

原文摘要 · Abstract (English)

Behavior Trees (BTs) are high-level controllers that are useful in a variety of planning tasks and are gaining traction in robotic mission planning. As they gain popularity in safety-critical domains, it is important to formalize their syntax and semantics, as well as verify properties for them. In this paper, we formalize a class of BTs we call Stateful Behavior Trees (SBTs) that have auxiliary variables and operate in an environment that can change over time. SBTs have access to persistent shared memory (often known as a blackboard) that keeps track of these auxiliary variables. We demonstrate that SBTs are equivalent in computational power to Turing Machines when the blackboard can store mathematical (i.e., unbounded) integers. We further identify syntactic assumptions where SBTs have computational power equivalent to finite state automata, specifically where the auxiliary variables are of finitary types. We present a domain specific language (DSL) for writing SBTs and adapt the tool BehaVerify for use with this DSL. This new DSL in BehaVerify supports interfacing with popular BT libraries in Python, and also provides generation of Haskell code and nuXmv models, the latter of which is used for model checking temporal logic specifications for the SBTs. We include examples and scalability results where BehaVerify outperforms another verification tool by a factor of 100.

行为树形式化验证机器人规划

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