連続環境における視覚言語ナビゲーションの閉ループ強化学習のためのマクロ行動に基づくトポロジカルグラフの再考
Revisiting Topological Graphs for Macro Action based Closed-loop Reinforcement Learning of Vision Language Navigation in Continuous Environment
VLN-CEタスクを階層的MDPとして再構成し、トポロジカルグラフ上のマクロ行動空間で強化学習を行うことで、サンプル効率と性能を向上させた。
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著者: Shuhao Ye, Sitong Mao, Yuxiang Cui, Yufei Wei, Xuan Yu, Shichao Zhai, Wen Chen, Shunbo Zhou, Rong Xiong, Yue Wang
分類: cs.RO
原文アブストラクト
Vision-Language Navigation in Continuous Environments (VLN-CE) requires an agent to follow natural language instructions through unseen environments. Existing imitation learning (IL) pipelines struggle in this closed-loop setting: behavior cloning suffers from distribution shift, and DAgger's expert actions become ambiguous upon trajectory deviation. While Reinforcement Learning (RL) offers a natural paradigm to address this, directly applying RL to micro action spaces is sample-inefficient due to reward sparsity. To overcome this bottleneck, we reformulate VLN-CE as a Hierarchical Markov Decision Process (MDP), explicitly decoupling high-level planning from low-level control. By abstracting the environment into a topological graph, our high-level policy operates on a macro action space of frontier nodes, with a training-free low-level controller acting as its state transition, which significantly compresses the decision horizon and makes closed-loop RL tractable. To support RL optimization on the macro MDP, we propose an action-aware value head to effectively evaluate state values under the dynamic frontier action space, powering a graph-based PPO. Extensive experiments demonstrate the effectiveness of our architecture. Finally, our model achieves state-of-the-art performance on the R2R-CE and RxR-CE benchmarks.