Adaptive quantized control based on output feedback for nonlinear systems with sensor faults under intermittent DoS attacks

Quantized signal control has been widely recognized as an effective means for conserving communication resources. However, ensuring stability of quantization-driven nonlinear systems becomes particularly challenging in the presence of intermittent denial-of-service (DoS) attacks and sensor failures. This article explores the stable control problem of quantized nonlinear systems subject to DoS attacks. When an attack exists, all signals are unmeasurable. During the dormant phase of a DoS attack, only the quantized output signal is measurable, while there is a deviation between the received signal and the ideal signal due to sensor failure. To address these challenges, a switch-type quantized observer is designed in this article to estimate unmeasurable state signals. In addition, we integrate the first-order dynamic filter into the back-stepping design process, which not only avoid the obstacles arisen from non-differentiable output signals, but also simplifies the design process. Furthermore, this article adopts a more flexible sector quantizer and derives a set of adaptive laws to compensate for unknown quantization parameters. It is shown that, by utilizing the estimated signal, the proposed quantized adaptive control is able to effectively fight against DoS attacks and also is fault-tolerant to sensor failures, guaranteeing semi-globally uniformly ultimately bounded for all closed-loop signals. Finally, simulation results validate the effectiveness of the proposed theory.