Multimodal Behavior Tree Generation: A Small Vision-Language Model for Robot Task Planning

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Hauptverfasser: Battistini, Cristiano, Izzo, Riccardo Andrea, Bardaro, Gianluca, Matteucci, Matteo
Format: Preprint
Veröffentlicht: 2026
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author Battistini, Cristiano
Izzo, Riccardo Andrea
Bardaro, Gianluca
Matteucci, Matteo
author_facet Battistini, Cristiano
Izzo, Riccardo Andrea
Bardaro, Gianluca
Matteucci, Matteo
contents Large and small language models have been widely used for robotic task planning. At the same time, vision-language models (VLMs) have successfully tackled problems such as image captioning, scene understanding, and visual question answering. In this work, we combine these two approaches by deploying a compact, open-source multimodal model to generate behavior trees for robotic task planning. The main obstacle to achieving this goal is the lack of an existing dataset that links visual observations and instructions to executable behavior trees. We propose a method to construct such a dataset starting from existing robotic episodes (i.e., Open X-Embodiment), in which a large model serves as a teacher in a multi-stage generation pipeline. We use this dataset to fine-tune VLMs ranging from 500M to 4B parameters via parameter-efficient fine-tuning (PEFT). The generated behavior trees, compatible with the BehaviorTree.CPP library, are evaluated both offline, using structural and lexical metrics, and online through the execution of household tasks in a state-of-the-art embodied simulator. Our results demonstrate that our fine-tuned 4B-parameter VLM approaches the performance of state-of-the-art closed-source models, achieving an 87\% success rate while requiring only a fraction of the computational resources.
format Preprint
id arxiv_https___arxiv_org_abs_2603_06084
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Multimodal Behavior Tree Generation: A Small Vision-Language Model for Robot Task Planning
Battistini, Cristiano
Izzo, Riccardo Andrea
Bardaro, Gianluca
Matteucci, Matteo
Robotics
Large and small language models have been widely used for robotic task planning. At the same time, vision-language models (VLMs) have successfully tackled problems such as image captioning, scene understanding, and visual question answering. In this work, we combine these two approaches by deploying a compact, open-source multimodal model to generate behavior trees for robotic task planning. The main obstacle to achieving this goal is the lack of an existing dataset that links visual observations and instructions to executable behavior trees. We propose a method to construct such a dataset starting from existing robotic episodes (i.e., Open X-Embodiment), in which a large model serves as a teacher in a multi-stage generation pipeline. We use this dataset to fine-tune VLMs ranging from 500M to 4B parameters via parameter-efficient fine-tuning (PEFT). The generated behavior trees, compatible with the BehaviorTree.CPP library, are evaluated both offline, using structural and lexical metrics, and online through the execution of household tasks in a state-of-the-art embodied simulator. Our results demonstrate that our fine-tuned 4B-parameter VLM approaches the performance of state-of-the-art closed-source models, achieving an 87\% success rate while requiring only a fraction of the computational resources.
title Multimodal Behavior Tree Generation: A Small Vision-Language Model for Robot Task Planning
topic Robotics
url https://arxiv.org/abs/2603.06084