解决强化学习中状态约束下的训练震荡问题,提升安全性和稳定性。
Augmented Lagrangian Multiplier Network for State-wise Safety in Reinforcement Learning
- 引入二次惩罚项和双目标监督回归,稳定状态依赖的乘子网络训练。
- 在多个环境中实现更优的安全性与回报,且乘子学习更准确。
- 适合需要高安全性的强化学习应用,如机器人控制、自动驾驶。
安全是现实世界强化学习的核心挑战。将安全约束建模为状态相关约束已成为主流方法。然而,使用拉格朗日方法处理状态约束需为每个状态配置独立乘子,通常需用神经网络近似,形成乘子网络。标准对偶梯度上升在此类网络上会引发严重训练震荡——因对偶上升固有不稳定性被网络泛化放大:局部过冲与延迟更新传播至邻近状态,进一步加剧策略波动。现有稳定化技术针对标量乘子设计,难以适用于状态依赖乘子网络。为此,本文提出增强拉格朗日乘子网络(ALaM)框架,实现状态乘子的稳定学习。ALaM包含两个关键组件:第一,将二次惩罚加入增强拉格朗日函数,补偿延迟更新并保证最优解附近局部凸性,缓解策略震荡;第二,通过监督回归训练乘子网络逼近一个双目标,提升训练稳定性与收敛性。理论上,我们证明ALaM能保证乘子收敛,从而恢复约束问题的最优策略。基于此框架,我们将软演员-评论家(SAC)与ALaM结合,构建SAC-ALaM算法。实验表明,SAC-ALaM在安全性与回报方面均优于现有最先进安全强化学习基线,同时稳定训练动态,并学习出能有效识别风险的校准乘子。
原文摘要 · Abstract (English)
Safety is a primary challenge in real-world reinforcement learning (RL). Formulating safety requirements as state-wise constraints has become a prominent paradigm. Handling state-wise constraints with the Lagrangian method requires a distinct multiplier for every state, necessitating neural networks to approximate them as a multiplier network. However, applying standard dual gradient ascent to multiplier networks induces severe training oscillations. This is because the inherent instability of dual ascent is exacerbated by network generalization -- local overshoots and delayed updates propagate to adjacent states, further amplifying policy fluctuations. Existing stabilization techniques are designed for scalar multipliers, which are inadequate for state-dependent multiplier networks. To address this challenge, we propose an augmented Lagrangian multiplier network (ALaM) framework for stable learning of state-wise multipliers. ALaM consists of two key components. First, a quadratic penalty is introduced into the augmented Lagrangian to compensate for delayed multiplier updates and establish the local convexity near the optimum, thereby mitigating policy oscillations. Second, the multiplier network is trained via supervised regression toward a dual target, which stabilizes training and promotes convergence. Theoretically, we show that ALaM guarantees multiplier convergence and thus recovers the optimal policy of the constrained problem. Building on this framework, we integrate soft actor-critic (SAC) with ALaM to develop the SAC-ALaM algorithm. Experiments demonstrate that SAC-ALaM outperforms state-of-the-art safe RL baselines in both safety and return, while also stabilizing training dynamics and learning well-calibrated multipliers for risk identification.
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