Policy Evaluation in Distributional LQRShow others and affiliations
2023 (English)In: Proceedings of the 5th Annual Learning for Dynamics and Control Conference, L4DC 2023, ML Research Press , 2023, Vol. 211, p. 1245-1256Conference paper, Published paper (Refereed)
Abstract [en]
Distributional reinforcement learning (DRL) enhances the understanding of the effects of the randomness in the environment by letting agents learn the distribution of a random return, rather than its expected value as in standard RL. At the same time, a main challenge in DRL is that policy evaluation in DRL typically relies on the representation of the return distribution, which needs to be carefully designed. In this paper, we address this challenge for a special class of DRL problems that rely on discounted linear quadratic regulator (LQR) for control, advocating for a new distributional approach to LQR, which we call distributional LQR. Specifically, we provide a closed-form expression of the distribution of the random return which, remarkably, is applicable to all exogenous disturbances on the dynamics, as long as they are independent and identically distributed (i.i.d.). While the proposed exact return distribution consists of infinitely many random variables, we show that this distribution can be approximated by a finite number of random variables, and the associated approximation error can be analytically bounded under mild assumptions. Using the approximate return distribution, we propose a zeroth-order policy gradient algorithm for risk-averse LQR using the Conditional Value at Risk (CVaR) as a measure of risk. Numerical experiments are provided to illustrate our theoretical results.
Place, publisher, year, edition, pages
ML Research Press , 2023. Vol. 211, p. 1245-1256
Series
Proceedings of Machine Learning Research, ISSN 26403498
Keywords [en]
Distributional LQR, distributional RL, policy evaluation, risk-averse control
National Category
Computer Sciences
Identifiers
URN: urn:nbn:se:kth:diva-338027ISI: 001221742900095Scopus ID: 2-s2.0-85172892657OAI: oai:DiVA.org:kth-338027DiVA, id: diva2:1804640
Conference
5th Annual Conference on Learning for Dynamics and Control, L4DC 2023, Philadelphia, PA, United States of America, Jun 16 2023 - Jun 15 2023
Note
QC 20231013
2023-10-132023-10-132024-09-05Bibliographically approved