用自适应校准提升安全控制滤波器的可靠性,防止误判风险。
Safe Control using Learned Safety Filters and Adaptive Conformal Inference

- 基于哈密顿-雅可比可达性学习安全滤波器,动态调整切换阈值
- 错误率被用户设定参数约束,保证不确定性量化不出错的概率上限
- 适合高维状态空间中的安全控制,尤其在分布外场景表现更优
安全滤波器已被证明是确保具有不安全默认策略的控制系统安全的有效工具。为应对传统合成方法在高维状态与控制空间中的可扩展性挑战,基于学习的方法被提出用于设计安全滤波器。然而,这些模型决策中不可避免的误差引发了对其可靠性和安全保证的担忧。本文提出自适应校准滤波(ACoFi),将基于学习的哈密顿-雅可比可达性安全滤波器与自适应校准推断相结合。在ACoFi下,滤波器根据对动作安全性预测的观测误差动态调整其切换标准。通过默认策略输出的安全值范围来量化安全性评估的不确定性,当该范围表明可能不安全时,滤波器从默认策略切换至学习的安全策略。我们证明,ACoFi保证了错误量化默认策略预测安全性不确定性的频率在渐近意义上被用户定义的参数所上界限定。这提供了一种软性安全保证而非硬性保证。我们在杜宾斯小车模拟和Safety Gymnasium环境中评估了ACoFi,实证表明其显著优于使用固定切换阈值的基线方法,在实现更高学习安全值的同时减少安全违规,尤其是在分布外场景中表现更佳。
原文摘要 · Abstract (English)
Safety filters have been shown to be effective tools to ensure the safety of control systems with unsafe nominal policies. To address scalability challenges in traditional synthesis methods, learning-based approaches have been proposed for designing safety filters for systems with high-dimensional state and control spaces. However, the inevitable errors in the decisions of these models raise concerns about their reliability and the safety guarantees they offer. This paper presents Adaptive Conformal Filtering (ACoFi), a method that combines learned Hamilton-Jacobi reachability-based safety filters with adaptive conformal inference. Under ACoFi, the filter dynamically adjusts its switching criteria based on the observed errors in its predictions of the safety of actions. The range of possible safety values of the nominal policy's output is used to quantify uncertainty in safety assessment. The filter switches from the nominal policy to the learned safe one when that range suggests it might be unsafe. We show that ACoFi guarantees that the rate of incorrectly quantifying uncertainty in the predicted safety of the nominal policy is asymptotically upper bounded by a user-defined parameter. This gives a soft safety guarantee rather than a hard safety guarantee. We evaluate ACoFi in a Dubins car simulation and a Safety Gymnasium environment, empirically demonstrating that it significantly outperforms the baseline method that uses a fixed switching threshold by achieving higher learned safety values and fewer safety violations, especially in out-of-distribution scenarios.
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