用可逆变换重塑策略分布,让机器人在环境变化时表现更优。
Warp RL: Reshaping Base Policy Distributions for Dynamics Adaptation
- 用状态相关的可逆变换替代加性修正,改变动作分布形状。
- 在动态变化任务中,性能优于传统残差强化学习,最快提速30%。
- 适合需要精准适应新环境的机器人操控场景,如真实机器人抓取。
残差强化学习通过学习对预训练机器人策略动作的加性修正来实现适应。然而当系统动态变化时,若基础策略的动作分布几何不匹配,仅靠加性修正无法调整分布形状、尺度或状态依赖结构,导致性能下降甚至低于未适配策略。本文提出Warp RL,用可逆的、状态条件化的动作分布变换替代加性残差。基于单调有理二次样条流(monotonic rational-quadratic spline flows),该方法保持初始化为恒等映射,严格泛化残差修正,并提供适合梯度和无梯度优化的结构化适应空间。在多种带受控动态偏移的ManiSkill3操作任务中,当仅需平移时,Warp RL性能与残差相当;当需重塑分布时则显著超越。进一步在离线策略的仿真到现实迁移中,替换加性修正后,在真实机器人插销任务上达到相近成功率,但任务完成速度提升30%。
原文摘要 · Abstract (English)
Residual reinforcement learning adapts a pretrained robot policy by learning an additive correction to its actions. While effective when adaptation amounts to shifting the base policy's action distribution, additive corrections cannot change the distribution's shape, scale, or state-dependent geometry -- limitations we formalize as wrong variance, miscalibrated confidence, and non-uniform correction. We show that these matter under dynamics shift: when the base distribution is geometrically mismatched to the shifted system, residual correction can underperform even the unadapted policy. We propose Warp RL, a policy adaptation method that replaces additive residuals with an invertible, state-conditioned transformation of the base policy's action distribution. Instantiated with monotonic rational-quadratic spline flows (arXiv:1906.04032), Warp RL preserves identity initialization, strictly generalizes additive residual correction, and exposes a structured adaptation space suitable for both policy-gradient and gradient-free optimization. Across a variety of ManiSkill3 manipulation tasks with controlled dynamics shifts, Warp RL matches residual correction when translation is sufficient and substantially outperforms it when adaptation requires distributional reshaping. We further demonstrate that warping can replace additive correction in an off-policy sim-to-real pipeline, achieving comparable success rate with 30% faster task completion on a real-robot peg-insertion task.
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