Adaptive Control and Intersections with Reinforcement Learning

This article provides an exposition of the field of adaptive control and its intersections with reinforcement learning. Adaptive control and reinforcement learning are two different methods that are both commonly employed for the control of uncertain systems. Historically, adaptive control has excelled at real-time control of systems with specific model structures through adaptive rules that learn the underlying parameters while providing strict guarantees on stability, asymptotic performance, and learning. Reinforcement learning methods are applicable to a broad class of systems and are able to produce near-optimal policies for highly complex control tasks. This is often enabled by significant offline training via simulation or the collection of large input-state datasets. This article attempts to compare adaptive control and reinforcement learning using a common framework. The problem statement in each field and highlights of their results are outlined. Two specific examples of dynamic systems are used to illustrate the details of the two methods, their advantages, and their deficiencies. The need for real-time control methods that leverage tools from both approaches is motivated through the lens of this common framework. Expected final online publication date for the Annual Review of Control, Robotics, and Autonomous Systems, Volume 14 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.