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Main Authors: Ru, Xi, Peng, Xiaoyu, Chen, Xinghua, Wang, Zhaojian, Yang, Peng, Liu, Feng
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2601.04796
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author Ru, Xi
Peng, Xiaoyu
Chen, Xinghua
Wang, Zhaojian
Yang, Peng
Liu, Feng
author_facet Ru, Xi
Peng, Xiaoyu
Chen, Xinghua
Wang, Zhaojian
Yang, Peng
Liu, Feng
contents The passivity index, a quantitative measure of a system's passivity deficiency or excess, has been widely used in stability analysis and control. Existing studies mostly rely on scalar forms of indices, which are restrictive for multi-input, multi-output (MIMO) systems. This paper extends the classical scalar indices to a systematic matrix-valued framework, referred to as passivity matrices. A broad range of classical results in passivity theory can be naturally generalized in this framework. We first show that, under the matrix representation, passivity indices essentially correspond to the curvature of the dissipativity functional under a second-variation interpretation. This result reveals that the intrinsic geometric structure of passivity consists of its directions and intensities, which a scalar index cannot fully capture. For linear time-invariant (LTI) systems, we examine the structural properties of passivity matrices with respect to the Loewner partial order and propose two principled criteria for selecting representative matrices. Compared with conventional scalar indices, the matrix-valued indices capture the passivity coupling among different input-output channels in MIMO systems and provide a more comprehensive description of system passivity. This richer information leads to lower passivation effort and less conservative stability assessment.
format Preprint
id arxiv_https___arxiv_org_abs_2601_04796
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Matrix-Valued Passivity Indices: Foundations, Properties, and Stability Implications
Ru, Xi
Peng, Xiaoyu
Chen, Xinghua
Wang, Zhaojian
Yang, Peng
Liu, Feng
Systems and Control
The passivity index, a quantitative measure of a system's passivity deficiency or excess, has been widely used in stability analysis and control. Existing studies mostly rely on scalar forms of indices, which are restrictive for multi-input, multi-output (MIMO) systems. This paper extends the classical scalar indices to a systematic matrix-valued framework, referred to as passivity matrices. A broad range of classical results in passivity theory can be naturally generalized in this framework. We first show that, under the matrix representation, passivity indices essentially correspond to the curvature of the dissipativity functional under a second-variation interpretation. This result reveals that the intrinsic geometric structure of passivity consists of its directions and intensities, which a scalar index cannot fully capture. For linear time-invariant (LTI) systems, we examine the structural properties of passivity matrices with respect to the Loewner partial order and propose two principled criteria for selecting representative matrices. Compared with conventional scalar indices, the matrix-valued indices capture the passivity coupling among different input-output channels in MIMO systems and provide a more comprehensive description of system passivity. This richer information leads to lower passivation effort and less conservative stability assessment.
title Matrix-Valued Passivity Indices: Foundations, Properties, and Stability Implications
topic Systems and Control
url https://arxiv.org/abs/2601.04796