Normalizing Flows are Capable Models for Bi-manual Visuomotor Policy

Fuente: arXiv
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Autores principales: Li, Jialong, Lind, Simon Kristoffersson, Xie, Wenrui, Stenmark, Maj, Krüger, Volker
Formato: Preprint
Publicado: 2025
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author Li, Jialong
Lind, Simon Kristoffersson
Xie, Wenrui
Stenmark, Maj
Krüger, Volker
author_facet Li, Jialong
Lind, Simon Kristoffersson
Xie, Wenrui
Stenmark, Maj
Krüger, Volker
contents The field of general-purpose robotics has recently embraced powerful probabilistic diffusion-based models to learn the complex embodiment behaviours. However, existing models often come with significant trade-offs, namely high computational costs for inference and a fundamental inability to quantify output uncertainty. We introduce Normalizing Flows Policy (NF-P), a conditional normalizing flow-based visuomotor policy for bi-manual manipulation. NF-P learns a conditional density over action sequences and enables single-pass generative sampling with tractable likelihood computation. Using this property, we propose two inference-time optimization strategies: Stochastic Batch Selection, which selects the highest-likelihood trajectory among sampled candidates, and Gradient Refinement, which directly ascends the log-likelihood to improve action quality. In both simulation and real robot experiments, NF-P achieves promising success rates compared to the baseline. In addition to improved task performance, NF-P demonstrates faster training and lower inference latency. These results establish normalizing flows as a competitive and computationally efficient visuomotor policy, particularly for real-time, uncertainty-aware robotic control.
format Preprint
id arxiv_https___arxiv_org_abs_2509_21073
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Normalizing Flows are Capable Models for Bi-manual Visuomotor Policy
Li, Jialong
Lind, Simon Kristoffersson
Xie, Wenrui
Stenmark, Maj
Krüger, Volker
Robotics
The field of general-purpose robotics has recently embraced powerful probabilistic diffusion-based models to learn the complex embodiment behaviours. However, existing models often come with significant trade-offs, namely high computational costs for inference and a fundamental inability to quantify output uncertainty. We introduce Normalizing Flows Policy (NF-P), a conditional normalizing flow-based visuomotor policy for bi-manual manipulation. NF-P learns a conditional density over action sequences and enables single-pass generative sampling with tractable likelihood computation. Using this property, we propose two inference-time optimization strategies: Stochastic Batch Selection, which selects the highest-likelihood trajectory among sampled candidates, and Gradient Refinement, which directly ascends the log-likelihood to improve action quality. In both simulation and real robot experiments, NF-P achieves promising success rates compared to the baseline. In addition to improved task performance, NF-P demonstrates faster training and lower inference latency. These results establish normalizing flows as a competitive and computationally efficient visuomotor policy, particularly for real-time, uncertainty-aware robotic control.
title Normalizing Flows are Capable Models for Bi-manual Visuomotor Policy
topic Robotics
url https://arxiv.org/abs/2509.21073