A networked control system (NCS), which integrates various physical components by utilising communication networks, is a complex intelligent control system with high flexibility and reliability. It has been widely applied in various areas, such as power grids, intelligent transportation, and smart manufacturing. However, compared with traditional control systems, NCSs expose more extra vulnerabilities with the openness of communication networks, leading to long-term concerns for the security of NCSs against cyber attacks. This paper gives a survey in detail on recent developments on the security of NCSs subject to deception attacks from the two domains of information technology (IT) and system control, respectively. First, several security incidents reported in recent years are reviewed and a couple of prevailing cyber attacks are analysed. Besides, the results on IT security with respect to the protection-detection-reaction model are summarised. Then, from the domain of system control, the security issues on attack design, attack detection, secure state estimation and resilient control are surveyed in depth. Furthermore, several novel security topics from the combination of IT and system control are also discussed. Finally, several future research directions are presented on this topic.

This article reviews the concept, analysis, development, and applications of the equivalent-input-disturbance (EID) approach. First, the definition and existence of the EID are given, and the configuration of the EID estimator is provided. Next, estimation errors in the conventional EID approach are explained, and error-suppression methods are exhibited, which improve the disturbance-rejection performance. Then, this article describes how to apply the EID approach and associate challenges in dealing with nonlinearities, time delays, and uncertainties. Moreover, this article reviews some additional meaningful studies that cannot be categorized into the above-mentioned classes. Finally, some conclusions and future directions are given. The EID approach has been successfully used to suppress the influences of exogenous disturbances, nonlinearities, time delays, and uncertainties in many control systems to improve control performance and robustness. Studies can further rich the theory of the EID approach in the future, such as designing evaluation index, improving disturbance-rejection performance, developing new applications, and combining with other control theory.

Dear Editor, In this letter, in order to deal with random network delays and packet losses in a class of networked nonlinear systems, three data-driven networked predictive control methods are designed. Their closed-loop systems and control increments are derived, respectively. Although the expressions of their control increments are obviously different, they are similar in form and composition, which are helpful to evaluate the effects of control actions. A comparison of the control performance of the three methods is carried out by a simulation example so as to show their advantages and disadvantages.

This paper proposes a novel interval prediction method for effluent water quality indicators (including biochemical oxygen demand (BOD) and ammonia nitrogen (NH3-N)), which are key performance indices in the water quality monitoring and control of a wastewater treatment plant. Firstly, the effluent data regarding BOD/NH3-N and their necessary auxiliary variables are collected. After some basic data pre-processing techniques, the key indicators with high correlation degrees of BOD and NH3-N are analyzed and selected based on a gray correlation analysis algorithm. Next, an improved IBES-LSSVM algorithm is designed to predict the BOD/NH3-N effluent data of a wastewater treatment plant. This algorithm relies on an improved bald eagle search (IBES) optimization algorithm that is used to find the optimal parameters of least squares support vector machine (LSSVM). Then, an interval estimation method is used to analyze the uncertainty of the optimized LSSVM model. Finally, the experimental results demonstrate that the proposed approach can obtain high prediction accuracy, with reduced computational time and an easy calculation process, in predicting effluent water quality parameters compared with other existing algorithms.

This article breaks the limits of applying an equivalent-input-disturbance (EID) approach to nonlinear systems. These limits are caused by the design requirement for the highest angular frequency of disturbances and unknown nonlinearities. We present an improved EID approach that removes this requirement. Thus, its application range is extended and the ability to reject nonlinearities is enhanced. The presented method has many additional merits. It improves the nonlinearity-compensation and disturbance-rejection performances while maintaining the level of configuration complexity and the number of parameters. Furthermore, its system configuration and design are simple. An analysis of the system configuration explains why the nonlinearity-compensation and disturbance-rejection performances are improved. Finally, simulation and experimental results show the validity and superiority of the presented method.

Grid-forming (GFM) inverters with inductor–capacitor (LC) filters are used to interface distributed generation with the grid. However, the GFM inverter systems are prone to incipient multiplicative faults due to the inherent parameter drift phenomenon of the LC filter. Motivated by this scenario, this article presents a primary active fault-tolerant control (PAFTC) strategy based on the robust-residual-observer-based-digital-twin model (RRODTM) to achieve the fault-tolerant control for the incipient multiplicative faults. The RRODTM is composed of a robust residual observer and a residual-driven compensation controller. Specially, the residual-driven compensation controller is designed by the data-driven method based on the multiplicative uncertainty caused by the incipient multiplicative faults. At the same time, this article constructs a data-driven-event-trigger mechanism based on stability margin to achieve the plug-and-play (PnP) function of the residual-driven compensation controller. Based on these, the PAFTC strategy improves the control performance online according to the degree of the incipient multiplicative fault. Comprehensive experiments show that compared to well-known control schemes in the literature, the PAFTC strategy improves the power distribution accuracy and transient response speed as well as enhances the robustness of the system.