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The problem of robust fault estimation of discrete-time nonlinear plant is investigated from the view of reducing its conservatism and restraining its on-line computational burden simultaneously. Firstly, an enhanced maximum-priority-based switching law is developed for subdividing the distribution types of normalized fuzzy weighting functions in a more flexible way. Then, a new fuzzy fault estimation observer is proposed with different switching modes in accordance with the updated value of the above switching law. More importantly, the proposed designing criterion is further optimized by considering the balance between reducing the conservatism and restraining the on-line computational burden. Finally, a set of simulation comparisons over the previous ones are provided to illustrate the advantages of our method developed in this paper. [ABSTRACT FROM AUTHOR]

This paper investigates the composite anti-disturbance control problem for the interconnected Semi-Markovian systems with multiple disturbances and actuator faults, where the state signal of each subsystem is quantized by logarithmic quantizer before being transmitted into controller. Two representative types of external disturbances are considered simultaneously, one is norm-bounded and the other is formulated by an exogenous system. To attenuate the modelling disturbance and diagnose the actuator faults, a distributed disturbance observer with fault diagnosis observer is constructed. Then, the composite quantized control methodology is proposed to compensate disturbances and faults, and stabilize the overall system. On the basis of proper Semi-Markovian Lyapunov-Krasovskii functional, some sufficient criterions are derived to ensure the stochastic stability with a prescribed performance. Moreover, the desired observer and controller gain matrices can be attained via linear matrix inequalities (LMIs) technique. Finally, a simulation example is given to demonstrate the feasibility and effectiveness of theoretical results. [ABSTRACT FROM AUTHOR]

Integrating wireless networks in control systems allow users to take benefit from modular and flexible system design, but the analysis and design of such systems pose new challenges such as more serious packet loss. This study develops a new multi-instant switching controller of nonlinear networked systems under unreliable wireless digital channels. The proposed controller can be viewed as an improvement of previous results concerned with the homogenous polynomials approach, since it presents a denser subdivision of the joint space of multi-instant normalized membership functions and therefore essentially yields an efficient multi-instant switching mechanism for the first time. As a result, more efficient results can be obtained in the study. Finally, an illustrative example is provided to demonstrate the effectiveness of the multi-instant switching controller. [ABSTRACT FROM AUTHOR]

This paper is concerned with the security consensus control issue for discrete-time multiagent systems (MASs) on the basis of a reinforcement learning (RL) approach. Considering the effects of denial-of-service (DoS) attacks, a novel control protocol is proposed to deal with the H ∞ consensus problem. Firstly, a Q -learning algorithm is put forward under the directed graph, which can obtain the target gain matrices without any system dynamics information. In addition, the obtained gain matrices and Lyapunov function are employed to demonstrate that the MASs can reach security consensus. Moreover, the proof of H ∞ consensus under undirected graphs is derived using the designed Q -learning algorithm. In the end, the simulation experiments are given to verify the correctness of the designed control strategy. [ABSTRACT FROM AUTHOR]

• In this paper, double closed-loop framework is proposed with the functions of faults and cyber-attacks detection. • The models of cyber-attacks, denial-of-service, information disclosure (privacy attack), stealthy attack and replay attacks, are formulated to be typical NCS models with parameter uncertainties from control theory perspective. • Information technique (IT) is synthesized together with control theory, and a novel framework is designed based on typical CPS structure, effective attack defense scenarios is devised and applied on this framework to detect and identify the cyber-attacks. In this paper, the issue of CPS security is investigated. By analyzing the process of multi-sources cyber-attacks of denial-of-service (DoS), information disclosure, stealthy attack and replay attack, a unified system model with uncertainties is formulated. Under this system model framework, robust control theory is applied to design the control scenarios for cyber-attack prevention. Furthermore, a double closed-loop NCS framework combined with information integration technology is proposed, necessary conditions for security guarantee are derived. Finally, a DC motor speed moderating example is given to demonstrate the problem. [ABSTRACT FROM AUTHOR]

This paper focuses on the optimal coordination control problem for continuous-time nonlinear multi-agent systems with completely unknown dynamics via a data-based distributed adaptive dynamic programming method. As for most real-world applications, accurate system models are complicated to obtain, which restricts the application of the conventional methods. Moreover, it is challenging to design optimal coordination control of multi-agent systems especially for the time-varying communication topology. To deal with the difficulties, we investigate a distributed adaptive dynamic programming method with identifier-critic architecture under the switching communication topology. First, using the available system data, an online adaptive identifier is developed to approximate the unknown model dynamics, and simultaneously a critic neural network is employed for approximation of the optimal cost function, which yields approximated optimal coordination control in real time. Then, we analyze the stability of our proposed scheme. Eventually, the simulation illustrates the effectiveness of the developed method. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of distributed event-triggered controller design for networked control systems (NCSs) with stochastic cyber-attacks. A decentralized event-triggered scheme is introduced to save the energy consumption and alleviate the transmission load of the network. Each sensor can make its own decision to determine whether the sampled data is delivered to the network or not. By taking two kinds of random cyber-attacks into consideration, a novel mathematical model is constructed for distributed event-triggered NCSs. Sufficient conditions which can guarantee the stability of the control system are obtained by applying Lyapunov stability theory, and the design method of the controller gain is presented in an exact expression. Finally, an example is given to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract The power sharing of AC/DC micro-grids is researched in this paper. The proposed strategy mainly include two parts: the primary power event triggering control with secondary control and an adaptive quasi sliding mode voltage control in inner-loop. Firstly, a event triggering power sharing control (ETPSC) based on P − F droop curve is developed to regulate the voltage and frequency of AC and voltage of DC with the aim of the proportional power sharing between AC and DC micro-grids. The triggered threshold of ETPSC can be chosen to decide the transmitted power between AC and DC micro-grids. When the difference power between AC and DC micro-grids is less than the triggered threshold of power flow, there is no power sharing between AC and DC micro-grids, which can less the number of switching the power flow direction and the transmitted line power loss. The ETPSC has a great robust for the disturbances of load and improve the stability of the system. An adaptive quasi-sliding-mode control,which is implemented easily and flexibly with small computational burden and only based on input/output (I/O) measurement data but not the model any more, is used to control voltage in inner-loop. The effectiveness of the proposed control schemes is demonstrated by some numerical simulations and experimental results. [ABSTRACT FROM AUTHOR]

The issue of H ∞ state estimation is addressed for complex networks (CNs) with inner coupling disturbance (ICD) while utilizing adaptive-frequency event-triggered mechanism (AFETM) and multi-channel random access protocol (MRAP). To maintain transmission frequency as much as possible while reducing data transmission, the proposed AFETM dynamically modifies the threshold based on the historical number of transmissions within a defined time interval. Data transmission after AFETM is scheduled by the MRAP, which enables the random selection and transmission of multiple signals, thereby avoiding network conflicts and congestion. The primary objective is to devise a estimator that guarantees the estimation errors meet the prescribed H ∞ performance. The attainment of sufficient conditions to achieve this objective involves the utilization of stochastic analysis. On this basis, the expected estimator gain is determined through the solution of the backward coupled difference equations. Ultimately, the performance of the devised estimator is validated by simulation. [ABSTRACT FROM AUTHOR]

This paper focuses on the design of H ∞ filter for a class of discrete-time networked systems. Given that the network communication resources are becoming limited with the ever-increasing network traffic, an adaptive event-triggered mechanism (AETM) is adopted for the systems to mitigate the pressure of network bandwidth. The considered discrete-time networked systems are envisioned to suffer from both Deception attacks and denial-of-service (DoS) attacks, thereby a novel hybrid cyber attacks model is firstly constructed to integrate the two kinds of attacks. Then, a filtering error system model is established for the discrete-time networked systems under AETM and hybrid cyber attacks. Based on the constructed model, the sufficient conditions that guaranteeing the asymptotic stability and H ∞ performance of the concerned filtering error system are analyzed based on Lyapunov–Krasovskii stability theory. Furthermore, the corresponding parameters of the designed filter are derived by solving a set of linear matrix inequalities (LMIs). The effectiveness of the designed filter is finally demonstrated by conducting a numerical example. [ABSTRACT FROM AUTHOR]

In this paper, the design problem of full-order fault estimation observer is investigated for a class of delta operator switched systems. Based on the definition of D − stability for delta operator switched systems, the full-order fault estimation observer and the mode-dependent average dwell time (MDADT) are designed to guarantee the D − stability and the H ∞ performance for the augmented system. For this, the regulating factor is introduced in the full-order fault estimation observer and it is the key factor to realize the D − stability. A flight switched system is finally employed to validate the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of multi-sensors-based security control for Takagi-Sugeno (T-S) fuzzy system over resource-constrained networks. To decrease the effects of resource-constrained networks, a distributed event-triggered scheme and a quantization mechanism are applied to lighten the burden of network transmission. By taking the influences of actuator saturation and denial-of-service (DoS) attacks into consideration, a novel mathematical model for T-S fuzzy system is constructed. Then, sufficient conditions ensuring the exponential stability of T-S fuzzy system are derived by using the Lyapunov stability theory. Moreover, the security controller gains for T-S fuzzy system are obtained by solving a set of linear matrix inequalities (LMIs). Finally, the feasibility of the proposed approach is demonstrated through simulation examples. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the problem of event-triggered fault detection filter design for nonlinear networked control systems with both sensor faults and process faults. First, Takagi–Sugeno (T–S) fuzzy model is utilized to represent the nonlinear systems with faults and disturbances. Second, a discrete event-triggered communication scheme is proposed to reduce the utilization of limited network bandwidth between filter and original system. At the same time, considering network-induced delays and event-triggered scheme, a novel T–S fuzzy fault detection filter is constructed to generate a residual signal, which has nonsynchronous premise variables with the original T–S fuzzy system. Then, the fuzzy Lyapunov functional based approach and the reciprocally convex approach are developed such that the obtained sufficient conditions ensure that the fuzzy fault detection system is asymptotically stable with H ∞ performance and is less conservative. All the conditions are given in terms of linear matrix inequalities (LMIs), which can be solved by LMI tools in MATLAB environment. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]