Distributionally Robust LQG with Kullback-Leibler Ambiguity Sets¶

Authors: Marta Fochesato, Lucia Falconi, Mattia Zorzi, Augusto Ferrante, John Lygeros

Published: 2025 (Preprint)

Source: arXiv

Algorithm: DR-LQG

arXiv: 2505.08370

Summary¶

Extends finite-horizon LQG control to distributional model uncertainty using time-local Kullback-Leibler ambiguity sets for process and measurement noise. The paper proves that optimal policies remain linear, gives a convergent iterative best-response computation, and sketches a dynamic-programming approximation for decision-dependent ambiguity sets.

Abstract¶

The Linear Quadratic Gaussian (LQG) controller is known to be inherently fragile to model misspecifications common in real-world situations. We consider discrete-time partially observable stochastic linear systems and provide a robustification of the standard LQG against distributional uncertainties on the process and measurement noise. Our distributionally robust formulation specifies the admissible perturbations by defining a relative entropy based ambiguity set individually for each time step along a finite-horizon trajectory, and minimizes the worst-case cost across all admissible distributions. We prove that the optimal control policy is still linear, as in standard LQG, and derive a computational scheme grounded on iterative best response that provably converges to the set of saddle points. Finally, we consider the case of endogenous uncertainty captured via decision-dependent ambiguity sets and we propose an approximation scheme based on dynamic programming.

Links¶

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Paper arxiv.org

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