This paper investigates modeling, analysis and design of Networked control systems (NCSs), which are of great interest due to the advantages presented here but also are technically complex because of the challenges of this class of systems such as delay and packet-dropout. Firstly, NCSs with packet dropouts are studied. Markov chains are introduced to describe historical behaviors of packet dropouts. By this method which introduced, general models are derived under single packet transmission protocols. Further more, controllers are designed to stabilizing the resulting closed-loop systems. Secondly, by above method an inverted pendulum which was controlled in a network with delays, is controlled in a network through packet-dropouts. simulation results show the effectiveness of the above method.

Predictive control is one of the effective methods to reduce the effect of time delay and data dropout in Networked control systems. In the proposed predictive control method, the control data is predicted as long as it covers the time delay and data dropout in the network, and the estimation of state variables is performed using the Kalman filter. By sending a package containing the predicted control data to the actuator and selecting the appropriate control data, the desired control performance of the system can be achieved. In this paper, the Networked control system is considered as a switching system with an arbitrary switching signal. A criterion for evaluating the stability of the closed-loop system with time delay and data dropout is presented based on the theory of switching systems. Time delay and data dropout are selected as switching parameters and a subset of switching dynamic systems is created in the discrete state space. By providing the Lyapunov function for all subsets and solving matrix inequalities, the stability of the system can be investigated. The simulation results show the effect of data dropout on the stability of the system by considering the time delay in the forward and feedback channels.

The Networked control system in modern control widely uses to decrease the implementation cost and increasing the performance. NCS in addition to its advantages is inevitable. Nevertheless they suffer of some limitations and deficiencies. Packet loss is one of the main limitations which affect the control system in different conditions and finally may lead to system instability. For this reason, it is important to model the system properly. In this paper, a new model has been proposed that is very simple and independent from the main system. This model based on Robust Theory structure. Robust theory is a branch of control theory that explicitly deals with uncertainty in its approach to controller design. Robust control methods are designed to function properly so long as uncertain parameters or disturbances are within some (typically compact) set.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

Networked control systems (NCS) is a new field in control systems that has emerged by the use of communication networks in control systems. NCS refers to a control system in which sensors, actuators, and controllers are connected via a communication network and enable remote monitoring and control. The use of communication networks in control systems have many advantages, like reducing the cost of wiring, increasing flexibility, and improving scalability. However, the integration of communication networks in control systems will also carries new challenges such as data transmission delay, data packet loss, and network congestion, that require new methods for modeling and designing control systems. Research in the Networked control systems is focused on the development of new modeling, estimating, identifying, and designing methods, which the effects of communication networks on the system’s behavior will be taken into account. In general, the field of NCS is an important research area because it allows the control systems to be applied in a wide range of applications and develop it in more efficient and flexible way. NCS can be found in various applications such as industrial automation, smart energy grids, transportation systems, and house automation. This article describes the emergence of control systems from the field of continuous time to Networked control and compares it with traditional control systems. Furthermore, the most important challenges in NCS and related approaches will be discussed. Important applications of Networked control systems by reviewing some featured case studies in Iran and other countries are also discussed. In the end, possible future directions in the development of Networked control systems will be presented.

Non-cooperative intelligent control agents (ICAs) with dedicated cost functions, can lead the system to poor performance and in some cases, closed-loop instability. A robust solution to this challenge is to place the ICAs at the feedback Nash equilibrium point (FNEP) of the differential game between them. This paper introduces the designation of a robust decentralized infinite horizon LQR control system based on the FNEP for a linear time-invariant system. For this purpose, two control strategies are defined. The first one is a centralized infinite horizon LQR (CIHLQR) problem (i.e. a supervisory problem), and the second one is a decentralized control problem (i.e. an infinite horizon linear-quadratic differential game). Then, while examining the optimal solution of each of the above strategies on the performance of the other, the necessary and sufficient conditions for the equivalence of the two problems are presented. In the absence of the conditions, by using the least-squares error criterion, an approximated CIHLQR controller is presented. It is shown that the theorems could be extended from a two-agent control system to a multi-agent system. Finally, the results are evaluated using the simulation results of a Two-Area non-reheat power system.

In this paper, a new approach of modeling and fault-tolerant control is presented for multi-rate Networked control system (MRNCS) with considering long time delay. Firstly, the MRNCS is modeled as a switched system with linear subsystems and a random switching signal. By considering the switching signal (as the result of random induced delay) as a Markov chain, the model of MRNCS is obtained as a Markovian jump linear system. Then a mode-independent dynamic output feedback controller is designed to stabilize the closed-loop system. In continuation, with the purpose of system tolerance against the actuator fault (or load disturbance), a virtual actuator is used so that the reconfiguration is performed without needing for any changes in the main controller. Finally, the quadrupletank process is used to validate the proposed modeling and control approaches.

With the development of computer networks, packet-based data transmission has found its way to Cyber-Physical systems (CPS) and especially, Networked control systems (NCS). NCSs are distributed industrial processes in which sensors and actuators exchange information between the physical plant and the controller via a network. Any loss of data or packet in the network links affects the performance of the physical system and its stability. This loss could be due to natural congestions in network or a result of intentional Denial of Service (DoS) attacks. In this paper, we analytically study the stability of NCSs with the possibility of data loss in the feed-forward link by modelling the system as a switching one. When data are lost (or replaced with a jammed or bogus invalid signal/packet) in the forward link, the physical system will not receive the control input sent from the controller. In this study, NCS is regarded as a stochastic switching system by using a two-position Markov jump model. In State 1, the control signal/packet passes through and gets to the system, while in State 2, the signal or packet is lost. We analyze the stability of system in State 2 by considering the situation as an open-loop control scenario with zero input. The proposed stochastic switching system is studied in both continuous and discrete-time spaces to see under what conditions it satisfies Lyapunov stability. The stability conditions are obtained according to random dwell times of the system in each state. Finally, the model is simulated on a DC motor as the plant. The results confirm the correctness of the obtained stability conditions.

In this paper, stability of a group of Networked cascade control systems based on a new continuous-time model is investigated and H∞,state feedback controllers considering H∞,norm bounded constraint are designed in order to attenuate external disturbances. The main objective of this research is to simplify stability analysis and provide the possibility of considering different configurations based on a continuous-time state-space model for these systems. To this aim, here it is assumed that data transformation between the secondary controller and the actuator is performed through a communication network. Using communication networks would result in some imperfections such as communication delay and data packet loss which are considered in the modelling of the system. Then, the state-space equations of the systems are converted to an equivalent augmented state-space equation. Stability of the system is analyzed based on the Lyapunov-Krasovskii theorem and using free weighting matrix method and controller gains as well as maximum allowable delay bound are computed. Simulation results confirm the validity of the proposed method.