Adaptive Shielding under Uncertainty

TL;DR

This paper introduces an adaptive shielding method for control systems operating under uncertainty, capable of adjusting to evolving environments to ensure safety and performance in complex tasks.

Contribution

It presents a novel approach to compute adaptive shields based on abstract MDP representations, suitable for dynamic environments and compatible with various controllers.

Findings

Effective in urban traffic control scenarios

Adapts to changing environment dynamics

Ensures safety without hindering controller performance

Abstract

This paper targets control problems that exhibit specific safety and performance requirements. In particular, the aim is to ensure that an agent, operating under uncertainty, will at runtime strictly adhere to such requirements. Previous works create so-called shields that correct an existing controller for the agent if it is about to take unbearable safety risks. However, so far, shields do not consider that an environment may not be fully known in advance and may evolve for complex control and learning tasks. We propose a new method for the efficient computation of a shield that is adaptive to a changing environment. In particular, we base our method on problems that are sufficiently captured by potentially infinite Markov decision processes (MDP) and quantitative specifications such as mean payoff objectives. The shield is independent of the controller, which may, for instance, take the form of a high-performing reinforcement learning agent. At runtime, our method builds an internal abstract representation of the MDP and constantly adapts this abstraction and the shield based on observations from the environment. We showcase the applicability of our method via an urban traffic control problem.