Attack-Resilient Supervisory Control of Discrete Event Systems Under Dynamic-Event-Protection Mechanisms

We investigate the problem of synthesizing safe supervisors for discrete-event systems under actuator attacks, where an adversary can partially override control commands at vulnerable states. We introduce a novel dynamic-event-protection mechanism, where the system can defend itself from attacks by taking defense actions when it meets certain required safety levels. The system employs two policies: a safety-enhancement policy that dynamically manipulates protecting events to increase the safety level, and a state-defense policy that determines whether to defend against attacks when sufficient safety levels are accumulated. Our goal is to synthesize a attack-resilient supervisor, along with compatible safety-enhancement and state-defense policies, to ensure the closed-loop system remains safe under any possible attacks on vulnerable states. We provide a sound and complete approach for synthesizing the supervisor and policies by formulating the problem as a safety game played on a multilayered duplication structure of the original system. We illustrate the proposed approach by running examples.