Beyond Quadratic Costs in LQR: Bregman Divergence Control

Fuente: arXiv
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Main Authors: Hassibi, Babak, Hajar, Joudi, Ghane, Reza
Format: Preprint
Published: 2025
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author Hassibi, Babak
Hajar, Joudi
Ghane, Reza
author_facet Hassibi, Babak
Hajar, Joudi
Ghane, Reza
contents In the past couple of decades, the use of ``non-quadratic" convex cost functions has revolutionized signal processing, machine learning, and statistics, allowing one to customize solutions to have desired structures and properties. However, the situation is not the same in control where the use of quadratic costs still dominates, ostensibly because determining the ``value function", i.e., the optimal expected cost-to-go, which is critical to the construction of the optimal controller, becomes computationally intractable as soon as one considers general convex costs. As a result, practitioners often resort to heuristics and approximations, such as model predictive control that only looks a few steps into the future. In the quadratic case, the value function is easily determined by solving Riccati equations. In this work, we consider a special class of convex cost functions constructed from Bregman divergence and show how, with appropriate choices, they can be used to fully extend the framework developed for the quadratic case. The resulting optimal controllers are infinite horizon, come with stability guarantees, and have state-feedback, or estimated state-feedback, laws. They exhibit a much wider range of behavior than their quadratic counterparts since the feedback laws are nonlinear. The approach can be applied to several cases of interest, including safety control, sparse control, and bang-bang control.
format Preprint
id arxiv_https___arxiv_org_abs_2505_00317
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond Quadratic Costs in LQR: Bregman Divergence Control
Hassibi, Babak
Hajar, Joudi
Ghane, Reza
Systems and Control
Optimization and Control
In the past couple of decades, the use of ``non-quadratic" convex cost functions has revolutionized signal processing, machine learning, and statistics, allowing one to customize solutions to have desired structures and properties. However, the situation is not the same in control where the use of quadratic costs still dominates, ostensibly because determining the ``value function", i.e., the optimal expected cost-to-go, which is critical to the construction of the optimal controller, becomes computationally intractable as soon as one considers general convex costs. As a result, practitioners often resort to heuristics and approximations, such as model predictive control that only looks a few steps into the future. In the quadratic case, the value function is easily determined by solving Riccati equations. In this work, we consider a special class of convex cost functions constructed from Bregman divergence and show how, with appropriate choices, they can be used to fully extend the framework developed for the quadratic case. The resulting optimal controllers are infinite horizon, come with stability guarantees, and have state-feedback, or estimated state-feedback, laws. They exhibit a much wider range of behavior than their quadratic counterparts since the feedback laws are nonlinear. The approach can be applied to several cases of interest, including safety control, sparse control, and bang-bang control.
title Beyond Quadratic Costs in LQR: Bregman Divergence Control
topic Systems and Control
Optimization and Control
url https://arxiv.org/abs/2505.00317