Towards Practical World Model-based Reinforcement Learning for Vision-Language-Action Models

TL;DR

This paper introduces VLA-MBPO, a practical framework for fine-tuning vision-language-action models in robotics using world models, enhancing efficiency, robustness, and scalability for real-world applications.

Contribution

It proposes a novel approach combining multimodal models, multi-view consistency, and chunk-level rollouts to improve VLA model training in interactive environments.

Findings

Significant improvement in policy performance.

Enhanced sample efficiency in training.

Robustness demonstrated in real-world robotic tasks.

Abstract

Vision-Language-Action (VLA) models show strong generalization for robotic control, but finetuning them with reinforcement learning (RL) is constrained by the high cost and safety risks of real-world interaction. Training VLA models in interactive world models avoids these issues but introduces several challenges, including pixel-level world modeling, multi-view consistency, and compounding errors under sparse rewards. Building on recent advances across large multimodal models and model-based RL, we propose VLA-MBPO, a practical framework to tackle these problems in VLA finetuning. Our approach has three key design choices: (i) adapting unified multimodal models (UMMs) for data-efficient world modeling; (ii) an interleaved view decoding mechanism to enforce multi-view consistency; and (iii) chunk-level branched rollout to mitigate error compounding. Theoretical analysis and experiments across simulation and real-world tasks demonstrate that VLA-MBPO significantly improves policy performance and sample efficiency, underscoring its robustness and scalability for real-world robotic deployment.