A preprint is published by Devdhar Patel, Joshua Russell, Francesca Walsh, Tauhidur Rahman, Terrance Sejnowski, and Hava Siegelmann in December 2022.

Abstract:

We present temporally layered architecture (TLA), a biologically inspired system for temporally adaptive distributed control. TLA layers a fast and a slow controller together to achieve temporal abstraction that allows each layer to focus on a different time-scale. Our design is biologically inspired and draws on the architecture of the human brain which executes actions at different timescales depending on the environment's demands. Such distributed control design is widespread across biological systems because it increases survivability and accuracy in certain and uncertain environments. We demonstrate that TLA can provide many advantages over existing approaches, including persistent exploration, adaptive control, explainable temporal behavior, compute efficiency and distributed control. We present two different algorithms for training TLA: (a) Closed-loop control, where the fast controller is trained over a pre-trained slow controller, allowing better exploration for the fast controller and closed-loop control where the fast controller decides whether to "act-or-not" at each timestep; and (b) Partially open loop control, where the slow controller is trained over a pre-trained fast controller, allowing for open loop-control where the slow controller picks a temporally extended action or defers the next n-actions to the fast controller. We evaluated our method on a suite of continuous control tasks and demonstrate the advantages of TLA over several strong baselines.

Conclusion:

In this work, we presented Temporally Layered Architecture (TLA), a framework for distributed, adaptive response time in reinforcement learning. The framework allows the RL agent to achieve smooth control in a real-time setting using a slow controller while a fast controller monitors and intervenes as required. Additionally, we demonstrated an alternative setting where the slow controller can gate the fast controller, activating it only when required for efficient control. We demonstrate faster convergence and more action repetition in the closed-loop approach and fewer decision and faster convergence in the partially-open loop approach. Additionally, we demonstrate in a real time setting, where processing and actuation delays are taken into account, and show that our approach outperforms the current approaches in the delayed setting while picking fewer actions. Our work demonstrates that a temporally adaptive approach has similar benefits for AI as has been demonstrated in biology and is an important direction for future research in artificially intelligent control.