A Cascade of Systems and the Product of Their $θ$-Symmetric Scaled Relative Graphs

Fuente: arXiv
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Autori principali: Yang, Xiaokan, Zhang, Ding, Chen, Wei, Qiu, Li
Natura: Preprint
Pubblicazione: 2025
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author Yang, Xiaokan
Zhang, Ding
Chen, Wei
Qiu, Li
author_facet Yang, Xiaokan
Zhang, Ding
Chen, Wei
Qiu, Li
contents In this paper, we utilize a variant of the scaled relative graph (SRG), referred to as the $θ$-symmetric SRG, to develop a graphical stability criterion for the feedback interconnection of a cascade of systems. A crucial submultiplicative property of $θ$-symmetric SRG is established, enabling it to handle cyclic interconnections for which conventional graph separation methods are not applicable. By integrating both gain and refined phase information, the $θ$-symmetric SRG provides a unified graphical characterization of the system, which better captures system properties and yields less conservative results. In the scalar case, the $θ$-symmetric SRG can be reduced exactly to the scalar itself, whereas the standard SRG appears to be a conjugate pair. Consequently, the frequency-wise $θ$-symmetric SRG is more suitable than the standard SRG as a multi-input multi-output extension of the classical Nyquist plot. Illustrative examples are included to demonstrate the effectiveness of the $θ$-symmetric SRG.
format Preprint
id arxiv_https___arxiv_org_abs_2510_06583
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Cascade of Systems and the Product of Their $θ$-Symmetric Scaled Relative Graphs
Yang, Xiaokan
Zhang, Ding
Chen, Wei
Qiu, Li
Systems and Control
In this paper, we utilize a variant of the scaled relative graph (SRG), referred to as the $θ$-symmetric SRG, to develop a graphical stability criterion for the feedback interconnection of a cascade of systems. A crucial submultiplicative property of $θ$-symmetric SRG is established, enabling it to handle cyclic interconnections for which conventional graph separation methods are not applicable. By integrating both gain and refined phase information, the $θ$-symmetric SRG provides a unified graphical characterization of the system, which better captures system properties and yields less conservative results. In the scalar case, the $θ$-symmetric SRG can be reduced exactly to the scalar itself, whereas the standard SRG appears to be a conjugate pair. Consequently, the frequency-wise $θ$-symmetric SRG is more suitable than the standard SRG as a multi-input multi-output extension of the classical Nyquist plot. Illustrative examples are included to demonstrate the effectiveness of the $θ$-symmetric SRG.
title A Cascade of Systems and the Product of Their $θ$-Symmetric Scaled Relative Graphs
topic Systems and Control
url https://arxiv.org/abs/2510.06583