In numerous reinforcement learning (RL) problems involving safety-critical systems, a key challenge lies in balancing multiple objectives while simultaneously meeting all stringent safety constraints. To tackle this issue, we propose a primal-based framework that orchestrates policy optimization between multi-objective learning and constraint adherence. Our method employs a novel natural policy gradient manipulation method to optimize multiple RL objectives and overcome conflicting gradients between different tasks, since the simple weighted average gradient direction may not be beneficial for specific tasks' performance due to misaligned gradients of different task objectives. When there is a violation of a hard constraint, our algorithm steps in to rectify the policy to minimize this violation. We establish theoretical convergence and constraint violation guarantees in a tabular setting. Empirically, our proposed method also outperforms prior state-of-the-art methods on challenging safe multi-objective reinforcement learning tasks.

在涉及安全关键系统的众多强化学习问题中，平衡多个目标并同时满足严格的安全约束是一个关键挑战。为解决这个问题，我们提出了一个基于原始的框架，通过多目标学习和约束遵从性之间的策略优化来协调。我们的方法采用了一种新颖的自然策略梯度操作方法，用于优化多个强化学习目标，并克服不同任务之间冲突梯度，因为简单的加权平均梯度方向可能不利于特定任务的性能，原因在于不同任务目标的梯度不对齐。当出现硬约束违规时，我们的算法介入纠正策略以最小化违规。我们在表格设置中建立了理论收敛和约束违规保证。在具有挑战性的安全多目标强化学习任务上，我们提出的方法在实证上也优于先前最先进的方法。

安全平衡：一种用于约束多目标强化学习的框架