Covert attack detection and secure control based on signal generator

The problem addressed in this paper is the monitoring and secure control in cyber–physical-systems subject to covert attacks. To reveal the covert attacks, an attack detection scheme by constructing signal generators in both cyber-layer and physical-layer is proposed. Different from the watermarking scheme, the dynamics of proposed signal generators are linear time invariant; also different from the moving target-based method, the proposed scheme does not need to rapidly alter the system dynamics. Moreover, the design parameter of signal generators can be chosen appropriately to guarantee the output tracking performance after the occurrence of attacks and before their detection. After the attack has been detected, the nominal output feedback controller is switched into a secure controller based on adaptive observer to ensure an output tracking performance level. Finally, numerical simulations are provided to show the effectiveness of the proposed scheme.