arXiv Machine Learning

Demystifying Linear Operator Learning for Control Systems

The paper introduces a structured method for learning linear operators in control systems using data. It leverages the framework of (semi)groups for evolution equations to establish structural assumptions and applies inverse‑problems theory to analyze learning algorithms, revealing error decompositions, convergence guarantees, and optimal regularization. Focusing on bounded operators on Hilbert spaces, the authors derive a convergent estimator for time‑varying systems, illustrating the practical power of their approach.

arXiv Machine Learning
Aug 26

Sequential operator learning under dependent data

The paper presents time‑uniform self‑normalized concentration bounds for stochastic processes in Hilbert spaces with vector‑valued noise, enabling regression‑error guarantees for both linear and nonlinear parametric operators. These results apply to possibly infinite‑dimensional inputs and outputs without requiring independence or mixing assumptions, and are derived in the context of sequentially collected, dependent data such as adaptive experimental design and dynamical‑system modelling.

By Rafael Oliveira
arXiv Machine Learning
Jul 7

Nonparametric Control Koopman Operators

arXiv:2405. 07312v5 Announce Type: replace-cross Abstract: This paper presents a novel Koopman composition operator representation framework for control systems in reproducing kernel Hilbert spaces (RKHSs) that is free of explicit dictionary or input parametrizations.

By Petar Bevanda, Bas Driessen, Lucian Cristian Iacob, Stefan Sosnowski, Roland T\'oth, Sandra Hirche
arXiv Machine Learning
Sep 15

Learning to Solve Stochastic Controls with Unknown Drifts and Running Rewards: Theory, Algorithms and Convergence

The paper investigates continuous‑time stochastic control problems with unknown drift and running reward functions, using an exploratory reinforcement learning framework that incorporates relaxed controls and entropy regularization. It develops policy‑iteration algorithms based on probabilistic representations of the optimal value function and its gradient, proving convergence and demonstrating performance through numerical examples. The study also extends to a special case with control‑dependent diffusion, requiring a Hessian representation.

By Jin Ma, Gaozhan Wang, Jianfeng Zhang, Xunyu Zhou
arXiv Machine Learning
Sep 17

Learning Lyapunov Operators for Nonlinear Systems

The paper investigates the Lyapunov solution operator, which maps a vector field to its corresponding Lyapunov function via a dissipation-based PDE. It proves that this operator is well-defined, unique, and continuous on compact subsets of the domain of attraction under exponential stability, enabling uniform approximation across families of nonlinear systems. Using Fourier Neural Operators, the authors demonstrate that a single trained operator can accurately approximate Lyapunov functions for parameterized dynamics, showcasing the potential of neural operators in stability analysis.

By Amartya Mukherjee, Maxwell Fitzsimmons, David C. Del Rey Fern\'andez, Jun Liu