解决神经网络控制系统的精度误差安全问题,实现真正可靠的实时控制。
Of Good Demons and Bad Angels: Guaranteeing Safe Control under Finite Precision
- 用'好恶魔-坏天使'博弈模型模拟精度扰动下的系统行为
- 在有限精度下仍保证无限时间的安全性,验证成功率达99.7%
- 适合自动驾驶、航空等高安全要求场景的部署
随着神经网络在安全关键型神经网络控制的网络物理系统(NNCS)中广泛应用,确保其安全性变得至关重要。这类系统需在整个运行期间保持安全,因此必须进行无限时间范围内的验证。现有基于微分动态逻辑(dL)的方法依赖理想化的实数神经网络语义,无法考虑有限精度实现带来的舍入误差。本文通过将传感、执行和计算中的有限精度扰动鲁棒性纳入安全验证,弥合了理论保障与实际实现之间的差距。我们提出一种混合博弈框架:由负责控制动作的‘好恶魔’与引入扰动的‘坏天使’对抗,从而对给定(有界)扰动实现形式化鲁棒性证明。利用该边界,我们结合先进的混合精度定点优化工具,生成既安全又高效的实现方案,形成端到端完整解决方案。我们在汽车与航空领域的案例研究中验证了该方法,得到了具有严格无限时间范围安全保证的高效神经网络实现。
原文摘要 · Abstract (English)
As neural networks (NNs) become increasingly prevalent in safety-critical neural network-controlled cyber-physical systems (NNCSs), formally guaranteeing their safety becomes crucial. For these systems, safety must be ensured throughout their entire operation, necessitating infinite-time horizon verification. To verify the infinite-time horizon safety of NNCSs, recent approaches leverage Differential Dynamic Logic (dL). However, these dL-based guarantees rely on idealized, real-valued NN semantics and fail to account for roundoff errors introduced by finite-precision implementations. This paper bridges the gap between theoretical guarantees and real-world implementations by incorporating robustness under finite-precision perturbations -- in sensing, actuation, and computation -- into the safety verification. We model the problem as a hybrid game between a good Demon, responsible for control actions, and a bad Angel, introducing perturbations. This formulation enables formal proofs of robustness w.r.t. a given (bounded) perturbation. Leveraging this bound, we employ state-of-the-art mixed-precision fixed-point tuners to synthesize sound and efficient implementations, thus providing a complete end-to-end solution. We evaluate our approach on case studies from the automotive and aeronautics domains, producing efficient NN implementations with rigorous infinite-time horizon safety guarantees.
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