Subgradient Method for System Identification with Non-Smooth Objectives

Fuente: arXiv
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Main Authors: Yalcin, Baturalp, Kim, Jihun, Lavaei, Javad
Format: Preprint
Published: 2025
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author Yalcin, Baturalp
Kim, Jihun
Lavaei, Javad
author_facet Yalcin, Baturalp
Kim, Jihun
Lavaei, Javad
contents This paper investigates a subgradient-based algorithm to solve the system identification problem for linear time-invariant systems with non-smooth objectives. This is essential for robust system identification in safety-critical applications. While existing work provides theoretical exact recovery guarantees using optimization solvers, the design of fast learning algorithms with convergence guarantees for practical use remains unexplored. We analyze the subgradient method in this setting, where the optimization problems to be solved evolve over time as new measurements are collected, and we establish linear convergence to the ground-truth system for both the best and Polyak step sizes after a burn-in period. We further characterize sublinear convergence of the iterates under constant and diminishing step sizes, which require only minimal information and thus offer broad applicability. Finally, we compare the time complexity of standard solvers with the subgradient algorithm and support our findings with experimental results. This is the first work to analyze subgradient algorithms for system identification with non-smooth objectives.
format Preprint
id arxiv_https___arxiv_org_abs_2503_16673
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Subgradient Method for System Identification with Non-Smooth Objectives
Yalcin, Baturalp
Kim, Jihun
Lavaei, Javad
Optimization and Control
Computational Complexity
Machine Learning
Systems and Control
62, 90, 93
This paper investigates a subgradient-based algorithm to solve the system identification problem for linear time-invariant systems with non-smooth objectives. This is essential for robust system identification in safety-critical applications. While existing work provides theoretical exact recovery guarantees using optimization solvers, the design of fast learning algorithms with convergence guarantees for practical use remains unexplored. We analyze the subgradient method in this setting, where the optimization problems to be solved evolve over time as new measurements are collected, and we establish linear convergence to the ground-truth system for both the best and Polyak step sizes after a burn-in period. We further characterize sublinear convergence of the iterates under constant and diminishing step sizes, which require only minimal information and thus offer broad applicability. Finally, we compare the time complexity of standard solvers with the subgradient algorithm and support our findings with experimental results. This is the first work to analyze subgradient algorithms for system identification with non-smooth objectives.
title Subgradient Method for System Identification with Non-Smooth Objectives
topic Optimization and Control
Computational Complexity
Machine Learning
Systems and Control
62, 90, 93
url https://arxiv.org/abs/2503.16673