Adaptive Control for Uncertain Nonlinear Systems Against DoS Attacks Using Quantized Output Only and Application to a Single-Link Robot

This paper investigates the problem of adaptive output feedback control for uncertain nonlinear systems with input/output quantization subject to intermittent denial-of-service (DoS) attacks. When a DoS attack becomes active, the system is unable to obtain output signal. In order to address this challenge, we compensate the output signal by introducing an attack compensator. At the same time, a novel quantization compensator-based (QC) state observer is designed, which uses only the quantized compensated signal to reconstruct the system states. In addition, the problem of over-parameterisation is avoided by using parameter projection technique to design the parameter estimator. By combining Lyapunov stability theory and a modified average dwell time (ADT) approach, the stability of the closed-loop system is ensured. Furthermore, the proposed controller ensures that all closed-loop signals are bounded, and the control performance of mean-square error can be adjusted by appropriately selecting certain design parameters. Finally, the effectiveness of the proposed control strategy is validated through a single-link robot simulation results.Note to Practitioners—Considering that resources are limited, the DoS attacks mentioned in this paper are aperiodic, which means that attackers engage in frequent attacks within a relatively short time frame. This aligns more closely with real-world scenarios of network attacks. When the attack is active, the output signal is not available for the system. In this paper, a new QC state observer is designed, which in turn enables the estimation of the system state signals. Furthermore, this paper considers both input and output quantization, which reduces duplicate transmission of samples and improves the use of communication resources. This makes the work in this paper more relevant to the practical engineering context.

I. Introduction

In recent years, with the rapid advancement of the network, there has been extensive scholarly attention directed towards the exploration of how to use the network for remote control of the system more conveniently and accurately. The network control system is a real-time feedback control system in which each control component is interconnected through the network, ultimately forming a closed-loop control system. All control devices within the system are regarded as network nodes, and data exchange among all nodes occurs through the network. Nowadays, the practical network control systems face various malicious cyber-attacks, such as denial-of-service (DoS) attacks [1], [2], and false data injection attacks [3], [4]. When DoS attacks occur, the network communication channels may be interrupted or blocked, which can result in data not being transmitted through the channels properly [5]. False data injection attacks are achieved by maliciously altering the communication signals, causing the system to be unable to obtain accurate data [6]. It is worth noting that DoS attacks are the most representative form of cyber-attacks, which can cause extremely detrimental effects on the performance and stability of the systems. Therefore, the security control problems of network control systems subject to DoS attacks have attracted the attention of scholars. The robust control problems of linear systems under DoS attacks were investigated in [7]. A new resilient triggering control strategy under DoS attacks was proposed in [8]. For wireless network control systems, a resilient sampling control scheme against DoS attacks was designed in [9]. For linear Cyber-Physical Systems under DoS attacks, an output feedback strategy was proposed to achieve the control objective of cooperative tracking [10]. It should be noted that the above literatures are primarily based on studies involving linear systems. However, when dealing with real industrial systems, various nonlinear factors are often present. This urges us to conduct more in-depth and more precise research on nonlinear systems. Under DoS attacks [11], a fault-tolerant cooperative control framework was constructed based on a switching-type observer. For nonlinear network control systems subjected to DoS attacks, a resilient control strategy was proposed [12]. In [13], a class of multiagent systems were considered, and an event-triggered security control scheme was proposed to address DoS attacks. A novel adaptive memory mechanism was introduced in [14] to further improve the observer accuracy for nonlinear multiagent systems under DoS attacks.