A note on input signal generators: A relaxation of Willems' fundamental lemma in the SISO case

Fuente: arXiv
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Autores principales: Yang, Yun Jeong, Lee, Jin Gyu
Formato: Preprint
Publicado: 2026
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author Yang, Yun Jeong
Lee, Jin Gyu
author_facet Yang, Yun Jeong
Lee, Jin Gyu
contents We provide a practical relaxation of Willems' fundamental lemma for discrete-time linear time-invariant (single-input-single-output) systems. Instead of maintaining conventional Willems' persistency of excitation condition in the behavioral theory, we reformulate the problem in terms of signal generators, hence going back to the dynamical systems theory. We discuss the relationship between the persistency of excitation order and the dimension of the signal generator. Furthermore, we identify a necessary and sufficient condition on the signal generator that can generate informative input--output data for almost all systems and initial conditions. This even includes inputs outside the class originally suggested by Willems' fundamental lemma, for example, sinusoidal sequences with fewer frequencies. Finally, the signal generator perspective allows a natural extension to continuous-time systems.
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id arxiv_https___arxiv_org_abs_2604_05964
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A note on input signal generators: A relaxation of Willems' fundamental lemma in the SISO case
Yang, Yun Jeong
Lee, Jin Gyu
Systems and Control
We provide a practical relaxation of Willems' fundamental lemma for discrete-time linear time-invariant (single-input-single-output) systems. Instead of maintaining conventional Willems' persistency of excitation condition in the behavioral theory, we reformulate the problem in terms of signal generators, hence going back to the dynamical systems theory. We discuss the relationship between the persistency of excitation order and the dimension of the signal generator. Furthermore, we identify a necessary and sufficient condition on the signal generator that can generate informative input--output data for almost all systems and initial conditions. This even includes inputs outside the class originally suggested by Willems' fundamental lemma, for example, sinusoidal sequences with fewer frequencies. Finally, the signal generator perspective allows a natural extension to continuous-time systems.
title A note on input signal generators: A relaxation of Willems' fundamental lemma in the SISO case
topic Systems and Control
url https://arxiv.org/abs/2604.05964