Learning Changes the World and Then What Was Learned has Changed: Training and Deploying Neural Networks in the Control Loop

Vittorio Lippi

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arXiv · 2610.22084

Learning Changes the World and Then What Was Learned has Changed: Training and Deploying Neural Networks in the Control Loop

Vittorio Lippi

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Abstract

Neural networks offer critical adaptability for controlling complex systems where nominal modeling proves intractable. However, when offline-trained neural networks are deployed within closed-loop control systems, their actions fundamentally alter the state distribution upon which they were trained. This paper introduces a unified taxonomy to categorize these sequential failure modes: the initial Closed-Loop Identification Error, the deployment-induced Action Error, and the continuous Tracking Error. Through discrete-time sensitivity analysis, this work formalizes how offline-learned parameters locally guarantee a trajectory divergence upon deployment, degrading performance due to local loss geometry. To mitigate this distribution shift, we propose actionable design policies centered on time-scale separated online adaptation. These mechanisms are validated through ablation studies on a nonlinear Duffing oscillator, demonstrating that bounded continuous learning successfully mitigates trajectory divergence whereas static deployments fail, offering concrete guidelines for practitioners deploying machine learning components in safety-critical feedback systems.

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Vittorio Lippi. 2026-10-15. Learning Changes the World and Then What Was Learned has Changed: Training and Deploying Neural Networks in the Control Loop. https://arxiv.org/abs/2610.22084

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