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arXiv · 2506.21030

STEP Planner: Constructing cross-hierarchical subgoal tree as an embodied long-horizon task planner

Tianxing Zhou·Zhirui Wang·Haojia Ao·Guangyan Chen·Boyang Xing·Jingwen Cheng·Yi Yang·Yufeng Yue
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Abstract

The ability to perform reliable long-horizon task planning is crucial for deploying robots in real-world environments. However, directly employing Large Language Models (LLMs) as action sequence generators often results in low success rates due to their limited reasoning ability for long-horizon embodied tasks. In the STEP framework, we construct a subgoal tree through a pair of closed-loop models: a subgoal decomposition model and a leaf node termination model. Within this framework, we develop a hierarchical tree structure that spans from coarse to fine resolutions. The subgoal decomposition model leverages a foundation LLM to break down complex goals into manageable subgoals, thereby spanning the subgoal tree. The leaf node termination model provides real-time feedback based on environmental states, determining when to terminate the tree spanning and ensuring each leaf node can be directly converted into a primitive action. Experiments conducted in both the VirtualHome WAH-NL benchmark and on real robots demonstrate that STEP achieves long-horizon embodied task completion with success rates up to 34% (WAH-NL) and 25% (real robot) outperforming SOTA methods.

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Tianxing Zhou, Zhirui Wang, Haojia Ao, Guangyan Chen, Boyang Xing, Jingwen Cheng, Yi Yang, Yufeng Yue. 2025-07-16. STEP Planner: Constructing cross-hierarchical subgoal tree as an embodied long-horizon task planner. https://arxiv.org/abs/2506.21030

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