Analysis of Non-Square Nonlinear MIMO Systems using Scaled Relative Graphs

Fuente: arXiv
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Main Authors: Krebbekx, Julius P. J., Tóth, Roland, Das, Amritam
Format: Preprint
Published: 2025
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_version_ 1866914480859906048
author Krebbekx, Julius P. J.
Tóth, Roland
Das, Amritam
author_facet Krebbekx, Julius P. J.
Tóth, Roland
Das, Amritam
contents Scaled Relative Graphs (SRGs) provide a novel graphical frequency-domain method for the analysis of nonlinear systems. There have been recent efforts to generalize SRG analysis to Multiple-Input Multiple-Output (MIMO) systems. However, these attempts yielded only results for square systems, due to the inherent Hilbert space structure of the SRG. In this paper, we develop an SRG analysis method that accommodates non-square operators. The key element is the embedding of operators to a space of operators acting on a common Hilbert space, while restricting the input space to the original input dimension, to avoid conservatism. We generalize SRG interconnection rules to restricted input spaces and develop stability theorems to guarantee causality, well-posedness and (incremental) $L_2$-gain bounds for the overall interconnection. We show utilization of the proposed theoretical concepts on the analysis of nonlinear systems in a Linear Fractional Representation (LFR) form, which is a rather general class of systems, and the LFR is directly utilizable for control. Moreover, we provide formulas for the computation of MIMO SRGs of stable LTI operators and diagonal and non-square static nonlinear operators. Finally, we demonstrate the advantages of our embedding approach on several examples.
format Preprint
id arxiv_https___arxiv_org_abs_2507_16513
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analysis of Non-Square Nonlinear MIMO Systems using Scaled Relative Graphs
Krebbekx, Julius P. J.
Tóth, Roland
Das, Amritam
Systems and Control
Optimization and Control
93D25 (Primary), 93C10 (Secondary)
Scaled Relative Graphs (SRGs) provide a novel graphical frequency-domain method for the analysis of nonlinear systems. There have been recent efforts to generalize SRG analysis to Multiple-Input Multiple-Output (MIMO) systems. However, these attempts yielded only results for square systems, due to the inherent Hilbert space structure of the SRG. In this paper, we develop an SRG analysis method that accommodates non-square operators. The key element is the embedding of operators to a space of operators acting on a common Hilbert space, while restricting the input space to the original input dimension, to avoid conservatism. We generalize SRG interconnection rules to restricted input spaces and develop stability theorems to guarantee causality, well-posedness and (incremental) $L_2$-gain bounds for the overall interconnection. We show utilization of the proposed theoretical concepts on the analysis of nonlinear systems in a Linear Fractional Representation (LFR) form, which is a rather general class of systems, and the LFR is directly utilizable for control. Moreover, we provide formulas for the computation of MIMO SRGs of stable LTI operators and diagonal and non-square static nonlinear operators. Finally, we demonstrate the advantages of our embedding approach on several examples.
title Analysis of Non-Square Nonlinear MIMO Systems using Scaled Relative Graphs
topic Systems and Control
Optimization and Control
93D25 (Primary), 93C10 (Secondary)
url https://arxiv.org/abs/2507.16513