Safe reinforcement learning (RL) aims to learn policies that satisfy certain constraints before deploying to safety-critical applications. Primal-dual as a prevalent constrained optimization framework suffers from instability issues and lacks optimality guarantees. This paper overcomes the issues from a novel probabilistic inference perspective and proposes an Expectation-Maximization style approach to learn safe policy. We show that the safe RL problem can be decomposed to 1) a convex optimization phase with a non-parametric variational distribution and 2) a supervised learning phase. We show the unique advantages of constrained variational policy optimization by proving its optimality and policy improvement stability. A wide range of experiments on continuous robotic tasks show that the proposed method achieves significantly better performance in terms of constraint satisfaction and sample efficiency than primal-dual baselines.

该研究通过引入新的期望最大化方法，并从概率推理的角度解决问题，将安全增强学习问题分解为凸优化和监督学习两个阶段，实现了更稳定和更高效的学习表现，并在连续机器人任务的广泛实验中取得了显著的约束满足性能和样本效率提升。

安全强化学习的约束变分策略优化