On the Existence of Quadratic Control Lyapunov Functions for Koopman-Operator based Bilinear Systems

Fuente: arXiv
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Autores principales: Hanna, Sami Leon Noel Aziz, Hoischen, Nicolas, Hirche, Sandra, Lederer, Armin
Formato: Preprint
Publicado: 2026
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author Hanna, Sami Leon Noel Aziz
Hoischen, Nicolas
Hirche, Sandra
Lederer, Armin
author_facet Hanna, Sami Leon Noel Aziz
Hoischen, Nicolas
Hirche, Sandra
Lederer, Armin
contents Koopman operator-based methods enable data-driven bilinear representations of unknown nonlinear control systems. Accurate representations often demand significantly higher dimensions than the original system, making control design challenging. Control Lyapunov Functions (CLFs) are widely used for controller synthesis, with quadratic CLF candidates being the most common due to their simplicity. Yet, we show that this class is highly restrictive, especially when the state dimension is large: under mild conditions, their existence implies stabilizability of the bilinear system by a constant input -- that is, the control remains fixed over time. We establish this result by formulating a quadratically constrained quadratic program (QCQP) that exactly characterizes valid CLFs. Since QCQPs are NP-hard, we propose a convex semidefinite relaxation that offers a sufficient validity condition. For single-input systems, we prove that a quadratic CLF requires constant control stabilizability, and empirically demonstrate that this extends to high-dimensional multi-input systems in many cases.
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id arxiv_https___arxiv_org_abs_2604_09267
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the Existence of Quadratic Control Lyapunov Functions for Koopman-Operator based Bilinear Systems
Hanna, Sami Leon Noel Aziz
Hoischen, Nicolas
Hirche, Sandra
Lederer, Armin
Systems and Control
Koopman operator-based methods enable data-driven bilinear representations of unknown nonlinear control systems. Accurate representations often demand significantly higher dimensions than the original system, making control design challenging. Control Lyapunov Functions (CLFs) are widely used for controller synthesis, with quadratic CLF candidates being the most common due to their simplicity. Yet, we show that this class is highly restrictive, especially when the state dimension is large: under mild conditions, their existence implies stabilizability of the bilinear system by a constant input -- that is, the control remains fixed over time. We establish this result by formulating a quadratically constrained quadratic program (QCQP) that exactly characterizes valid CLFs. Since QCQPs are NP-hard, we propose a convex semidefinite relaxation that offers a sufficient validity condition. For single-input systems, we prove that a quadratic CLF requires constant control stabilizability, and empirically demonstrate that this extends to high-dimensional multi-input systems in many cases.
title On the Existence of Quadratic Control Lyapunov Functions for Koopman-Operator based Bilinear Systems
topic Systems and Control
url https://arxiv.org/abs/2604.09267