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Hauptverfasser: Eijnden, Sebastiaan van den, Chen, Chao, Scheres, Koen, Chaffey, Thomas, Lanzon, Alexander
Format: Preprint
Veröffentlicht: 2025
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Online-Zugang:https://arxiv.org/abs/2504.21448
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author Eijnden, Sebastiaan van den
Chen, Chao
Scheres, Koen
Chaffey, Thomas
Lanzon, Alexander
author_facet Eijnden, Sebastiaan van den
Chen, Chao
Scheres, Koen
Chaffey, Thomas
Lanzon, Alexander
contents The scaled graph has been introduced recently as a nonlinear extension of the classical Nyquist plot for linear time-invariant systems. In this paper, we introduce a modified definition for the scaled graph, termed the signed scaled graph (SSG), in which the phase component is characterized by making use of the Hilbert transform. Whereas the original definition of the scaled graph uses unsigned phase angles, the new definition has signed phase angles which ensures the possibility to differentiate between phase-lead and phase-lag properties in a system. Making such distinction is important from both an analysis and a synthesis perspective, and helps in providing tighter stability estimates of feedback interconnections. We show how the proposed SSG leads to intuitive characterizations of positive real and negative imaginary nonlinear systems, and present various interconnection results. We showcase the effectiveness of our results through several motivating examples.
format Preprint
id arxiv_https___arxiv_org_abs_2504_21448
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On phase in scaled graphs
Eijnden, Sebastiaan van den
Chen, Chao
Scheres, Koen
Chaffey, Thomas
Lanzon, Alexander
Systems and Control
The scaled graph has been introduced recently as a nonlinear extension of the classical Nyquist plot for linear time-invariant systems. In this paper, we introduce a modified definition for the scaled graph, termed the signed scaled graph (SSG), in which the phase component is characterized by making use of the Hilbert transform. Whereas the original definition of the scaled graph uses unsigned phase angles, the new definition has signed phase angles which ensures the possibility to differentiate between phase-lead and phase-lag properties in a system. Making such distinction is important from both an analysis and a synthesis perspective, and helps in providing tighter stability estimates of feedback interconnections. We show how the proposed SSG leads to intuitive characterizations of positive real and negative imaginary nonlinear systems, and present various interconnection results. We showcase the effectiveness of our results through several motivating examples.
title On phase in scaled graphs
topic Systems and Control
url https://arxiv.org/abs/2504.21448