Resilience PI controller design for mitigating weak denial-of-service attacks in cyber-physical systems

Abstract

Modern control systems integrate with information technologies through Networked Control Systems and Cyber-Physical Systems (CPS). Although these systems are beneficial, they raise security concerns for critical infrastructure. Cyberattacks on CPS communication channels, such as denial-of-service (DoS) attacks, can cause significant time delays and data loss, leading to poor system performance and instability. This article assumes weak DoS attack influences as an unknown delay. Then, system maximum resistance time against DoS attacks will be calculated according to the Lyapunov–Krasovskii theorem, and a conservative upper bound delay is included in the system model, which maintains system stability. With this assumption, Kharitonov's theorem-based robust Proportional-Integral (PI) controller is developed to mitigate DoS attacks. In addition, another Ziegler–Nichols tuned PI controller is presented to demonstrate that the proposed robust PI controller effectively reduces DoS attack impacts on CPSs. Finally, in a liquid-level networked control system, the efficacy of two PI controllers was evaluated. Results show that Kharitonov's theorem-based controller surpasses the Ziegler–Nichols method PI controller in mitigating the impact of DoS attacks on system behaviour, including maintaining system stability and keeping both transient response characteristics and setpoint tracking at desired values. Also, the proposed design strategy for reducing DoS attack effects is simple and less conservative than other robust control methods.