Output Feedback Secure Control for Fully Quantized Nonlinear Systems Under Irregular Input/Output DoS Attacks

This article investigates the stability of fully quantized nonlinear systems under irregular denial-of-service (IDoS) attacks with unpredictable targets and frequencies. Unlike most existing works that focus only on DoS attacks in fixed or single-type channels, this work considers a more general attack mode, where attacks can occur in the input, output, or both simultaneously. During an attack, the signal in the affected channel is interrupted, rendering it inaccessible. Even if the system is safe, only quantized output signal is available. To address this, a novel state estimator is designed that switches different observer gains depending on the attacked channel. On this basis, we develop an output-feedback adaptive control algorithm that utilizes the estimated signals and incorporates a dynamic filtering technique. The control strategy effectively resists IDoS attacks, ensuring that all closed-loop signals remain semiglobally uniformly ultimately bounded (SUUB), and the stability error converges to a small residual set near the origin. Numerical simulation further confirmed the advantages and effectiveness of the proposed scheme.