用离线策略和时间逻辑奖励,让PPO在延迟奖励任务中更快更稳地学习。
Accelerating Proximal Policy Optimization Learning Using Task Prediction for Solving Environments with Delayed Rewards
- 混合离线专家策略与在线PPO,保持理论保障
- 延迟奖励环境下学习速度提升,最终性能更高
- 时间逻辑将时序目标转为即时反馈,适合复杂任务
本文解决强化学习中延迟奖励的挑战。尽管近端策略优化(PPO)是主流策略梯度方法,但在延迟奖励场景下表现下降。我们提出两项改进:一是融合离线策略(基于专家示范训练)与在线PPO的混合架构,全程利用离线数据并保持理论保证;二是基于时间窗时序逻辑(TWTL)的奖励塑造机制,将时序目标转化为即时反馈信号。在TRPO单调改进框架基础上,证明该方法能保证相对于离线策略及前一轮迭代的性能提升,且性能差距有界为$(2ςγα^2)/(1-γ)^2$,其中$α$为混合参数,$γ$为折扣因子,$ς$为期望优势的上界。同时证明了TWTL奖励塑造可保留原问题最优策略。在倒立摆与月球着陆器环境中验证,相比标准PPO和纯离线方法,本方法显著加速学习并提升最终性能。
原文摘要 · Abstract (English)
In this paper, we tackle the challenging problem of delayed rewards in reinforcement learning (RL). While Proximal Policy Optimization (PPO) has emerged as a leading Policy Gradient method, its performance can degrade under delayed rewards. We introduce two key enhancements to PPO: a hybrid policy architecture that combines an offline policy (trained on expert demonstrations) with an online PPO policy, and a reward shaping mechanism using Time Window Temporal Logic (TWTL). The hybrid architecture leverages offline data throughout training while maintaining PPO's theoretical guarantees. Building on the monotonic improvement framework of Trust Region Policy Optimization (TRPO), we prove that our approach ensures improvement over both the offline policy and previous iterations, with a bounded performance gap of $(2ςγα^2)/(1-γ)^2$, where $α$ is the mixing parameter, $γ$ is the discount factor, and $ς$ bounds the expected advantage. Additionally, we prove that our TWTL-based reward shaping preserves the optimal policy of the original problem. TWTL enables formal translation of temporal objectives into immediate feedback signals that guide learning. We demonstrate the effectiveness of our approach through extensive experiments on an inverted pendulum and a lunar lander environments, showing improvements in both learning speed and final performance compared to standard PPO and offline-only approaches.
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