Fast-in-Slow: A Dual-System Foundation Model Unifying Fast Manipulation within Slow Reasoning

Fuente: arXiv
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Main Authors: Chen, Hao, Liu, Jiaming, Gu, Chenyang, Liu, Zhuoyang, Zhang, Renrui, Li, Xiaoqi, He, Xiao, Guo, Yandong, Fu, Chi-Wing, Zhang, Shanghang, Heng, Pheng-Ann
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Published: 2025
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author Chen, Hao
Liu, Jiaming
Gu, Chenyang
Liu, Zhuoyang
Zhang, Renrui
Li, Xiaoqi
He, Xiao
Guo, Yandong
Fu, Chi-Wing
Zhang, Shanghang
Heng, Pheng-Ann
author_facet Chen, Hao
Liu, Jiaming
Gu, Chenyang
Liu, Zhuoyang
Zhang, Renrui
Li, Xiaoqi
He, Xiao
Guo, Yandong
Fu, Chi-Wing
Zhang, Shanghang
Heng, Pheng-Ann
contents Generalized policy and execution efficiency constitute the two critical challenges in robotic manipulation. While recent foundation policies benefit from the common-sense reasoning capabilities of internet-scale pretrained vision-language models (VLMs), they often suffer from low execution frequency. To mitigate this dilemma, dual-system approaches, inspired by Kahneman's theory, have been proposed to leverage a VLM-based System 2 model handling high-level reasoning and a separate System 1 action model ensuring real-time control. However, existing designs maintain both systems as separate models, limiting System 1 from fully leveraging the rich pretrained knowledge from the VLM-based System 2. In this work, we propose Fast-in-Slow (FiS), a unified dual-system vision-language-action (VLA) model that embeds the System 1 execution module within the VLM-based System 2 by partially sharing parameters. This innovative paradigm not only enables high-frequency execution in System 1 but also facilitates coordination between the reasoning and execution components within a single foundation model of System 2. Given their fundamentally distinct roles within FiS-VLA, we design the two systems to incorporate heterogeneous modality inputs alongside asynchronous operating frequencies, enabling both fast and precise manipulation. To enable coordination between the two systems, a dual-aware co-training strategy is proposed that equips System 1 with action generation capabilities while preserving System 2's contextual reasoning representation. For evaluation, FiS-VLA outperforms previous state-of-the-art methods by 8% in simulation and 11% in real-world tasks in terms of average success rate, while achieving a 117.7 Hz control frequency with action chunk set to eight. Project web page: fast-in-slow.github.io.
format Preprint
id arxiv_https___arxiv_org_abs_2506_01953
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Fast-in-Slow: A Dual-System Foundation Model Unifying Fast Manipulation within Slow Reasoning
Chen, Hao
Liu, Jiaming
Gu, Chenyang
Liu, Zhuoyang
Zhang, Renrui
Li, Xiaoqi
He, Xiao
Guo, Yandong
Fu, Chi-Wing
Zhang, Shanghang
Heng, Pheng-Ann
Robotics
Generalized policy and execution efficiency constitute the two critical challenges in robotic manipulation. While recent foundation policies benefit from the common-sense reasoning capabilities of internet-scale pretrained vision-language models (VLMs), they often suffer from low execution frequency. To mitigate this dilemma, dual-system approaches, inspired by Kahneman's theory, have been proposed to leverage a VLM-based System 2 model handling high-level reasoning and a separate System 1 action model ensuring real-time control. However, existing designs maintain both systems as separate models, limiting System 1 from fully leveraging the rich pretrained knowledge from the VLM-based System 2. In this work, we propose Fast-in-Slow (FiS), a unified dual-system vision-language-action (VLA) model that embeds the System 1 execution module within the VLM-based System 2 by partially sharing parameters. This innovative paradigm not only enables high-frequency execution in System 1 but also facilitates coordination between the reasoning and execution components within a single foundation model of System 2. Given their fundamentally distinct roles within FiS-VLA, we design the two systems to incorporate heterogeneous modality inputs alongside asynchronous operating frequencies, enabling both fast and precise manipulation. To enable coordination between the two systems, a dual-aware co-training strategy is proposed that equips System 1 with action generation capabilities while preserving System 2's contextual reasoning representation. For evaluation, FiS-VLA outperforms previous state-of-the-art methods by 8% in simulation and 11% in real-world tasks in terms of average success rate, while achieving a 117.7 Hz control frequency with action chunk set to eight. Project web page: fast-in-slow.github.io.
title Fast-in-Slow: A Dual-System Foundation Model Unifying Fast Manipulation within Slow Reasoning
topic Robotics
url https://arxiv.org/abs/2506.01953