Secure Estimation, Attack Isolation, and Reconstruction Based on Zonotopic Unknown Input Observer

In this article, the issues of secure estimation, attack reconstruction, and isolation are addressed for cyber-physical systems in the presence of malicious attacks. It is assumed that disturbances and noises are unknown-but-bounded. Based on different rank constraints, both zonotopic completely unknown input observer and zonotopic partially unknown input observer are designed to estimate system states. Then, malicious attacks are reconstructed and isolated based on the proposed zonotopic observers. By utilizing switching technique, the corresponding feedback controllers are designed, which can guarantee that the closed-loop system is stable. Finally, numerical simulations are provided to illustrate the validity of the presented approach.