This paper provides a survey on modeling and theories of networked control systems ( NCS ). In the first part, modeling of the different types of imperfections that affect NCS is discussed. These imperfections are quantization errors, packet dropouts, variable sampling / transmission intervals, variable transmission delays, and communication constraints. Then follows in the second part a presentation of several theories that have been applied for controlling networked systems. These theories include: input delay system approach, Markovian system approach, switched system approach, stochastic system approach, impulsive system approach, and predictive control approach. In the last part, some advanced issues in NCS including decentralized and distributed NCS, cloud control system, and co-design of NCS are reviewed.

Cyber-Physical Systems (CPS) are defined as integrations of computation, communication, and control in order to achieve the desired performance of physical processes. Security threats have a high possibility of affecting CPS by several cyber attacks without providing any indication about failure. One important problem, especially in power systems, is the control problem of systems under cyber attacks. In this paper, a secure observer-based controller for discrete-time CPS subject to both cyber (denial of service (DoS) and deception) and physical attacks will be presented. The occurrences of the cyber and physical attacks will be considered as Bernoulli distributed white sequences with variable conditional probabilities. A sufficient condition is first derived under which the observer-based controller is guaranteed to have the desired security level using the stochastic analysis techniques. Then, the observer and controller gains will be designed by solving a linear matrix inequality using YALMIP and MATLAB. Finally, an illustrative example is provided to demonstrate the feasibility of the proposed system.

A wireless networked control system (WNCS) consists of a dynamic system to be controlled, sensors, actuators, and a remote controller. A WNCS has two types of wireless transmissions, i.e., the sensor's measurement transmission to the controller and the controller's command transmission to the actuator. In this paper, we are surveying the literature on the communication networks in WNCSs and the challenges related to them, such as the communication standards, delay, Packet dropout, and delay jitter. Then, the control approaches in the design of a WNCS are presented, including the interactive design approaches and the joint design approaches. Also, several applications of WNCSs have been discussed in terms of their structure, functionality, and control design. These applications include Intra-Vehicle Wireless networks, Wireless Avionics Intra-Communication, Building Automation, and Water pumping. After that, security issues in WNCSs from a control engineering point of view are detailed while focusing on the major kinds of cyber attacks affecting WNCSs. Finally, future directions and conclusions are summarized at the end of the paper.