A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> There is a growing interest in design and implementation of cyber-physical control systems over wireless sensor and actuator networks (WSANs). Thanks to the use of wireless communications and distributed architectures, these systems encompass many advantages as compared to traditional networked control systems using hard wirelines. While WSANs are enabling a new generation of control systems, they also introduce considerable challenges to quality-of-service (QoS) provisioning. In this chapter, we examine some of the major QoS challenges raised by WSANs, including resource constraints, platform heterogeneity, dynamic network topology, and mixed traffic. These challenges make it difficult to fulfill the requirements of cyber-physical control in terms of reliability and real time. The focus of this chapter is on addressing the problem of network reliability. Specifically, we analyze the behavior of wireless channels via simulations based on a realistic link-layer model. Packet loss rate (PLR) is taken as a major metric for the analysis. The results confirm the unreliability of wireless communications and the uncertainty of packet loss over WSANs. To tackle packet loss, we present a simple solution that can take advantage of existing prediction algorithms. Simulations are conducted to evaluate the performance of several classical prediction algorithms used for loss compensation. The results give some insights into how to deal with packet loss in cyber-physical control systems over unreliable WSANs. <s> BIB001 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> The article deals with integrating the inertial navigation unit implemented into the system of controlling the robot. It analyses the dynamic properties of the sensors of the inertial unit, for example, gyroscopes and accelerometers. The implementation of the original system of controlling the mobile robot on the basis of autonomous navigation systems is a dominant part of the article. The integration of navigational information represents the actual issue of reaching higher accuracy of required navigational parameters using more or less accurate navigation systems. The inertial navigation is the navigation based on uninterrupted evaluation of the position of a navigated object by utilizing the sensors that are sensitive to motion, that is, gyroscopes and accelerometers, which are regarded as primary inertial sensors or other sensors located on the navigated object. <s> BIB002 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> A self-triggered sampling scheme (STS) is proposed for a networked control system with consideration of data losses and communication delays. By making use of this scheme, the next sampling instant does not depend on online estimation of an event-triggered condition and the successive measurement of the state, and can be dynamically determined with respect to the transmitted packet, the desired control performance, and the allowable number of consecutive data losses and communication delays. Consequently, the sampling interval can be adaptively adjusted. Therefore, the communication burden can be greatly reduced and the energy efficiency can be much improved while preserving the desired ${H_\infty}$ performance. An inverted pendulum and a one-area power system controlled over a wireless sensor network are given to illustrate the effectiveness of the proposed STS. <s> BIB003 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> Cyberphysical systems (CPSs) are perceived as the pivotal enabler for a new era of real-time Internetbased communication and collaboration among value-chain participants, e.g., devices, systems, organizations, and humans. The CPS utilization in industrial settings is expected to revolutionize the way enterprises conduct their business from a holistic viewpoint, i.e., from shop-floor to business interactions, from suppliers to customers, and from design to support across the whole product and service lifecycle. Industrial CPS (ICPSs) blur the fabric of cyber (including business) and physical worlds and kickstart an era of systemwide collaboration and information-driven interactions among all stakeholders of the value chain. Therefore, ICPSs are expected to empower the transformation of industry and business at large to a digital, adaptive, networked, and knowledge-based industry with significant long-term impact on the economy, society, environment, and citizens. <s> BIB004 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> Oil spill at the Gulf of Mexico a few years ago sets great hazardous to environments. The runtime monitoring and tracking of plume pose challenges to research community. Robot-based approaches have been proposed in previous work to solve this problem in environments with known physical parameters and measurable currents. However, practical implementation of this type of control laws may require additional sensors and the sensing error may significantly impact the convergence. This paper extends previous work by overcoming the challenge to establish a new control law by integrating interactive estimation and control in a unified loop. With a deliberate design, the parameters can be estimated online and the control can be achieved at the same time with provable convergence of the overall system, despite of the interplay of the two parts. An auxiliary system is constructed for efficient estimation of unknown parameters and set projection is incorporated to further improve the transient performance, making the system work well in both slow and fast time-varying environments. Theories of convergence, stability, and transient state are presented to guarantee the performance of plume front tracking. Validation experiments verify the theoretical results and substantiate the efficacy of the proposed scheme for plume tracking in unknown environments. <s> BIB005 </s> A Survey on Model-Based Distributed Control and Filtering for Industrial Cyber-Physical Systems <s> I. INDUSTRIAL CYBER-PHYSICAL SYSTEMS <s> The neural-network (NN)-based output-feedback control is considered for a class of stochastic nonlinear systems under round-Robin (RR) scheduling protocols. For the purpose of effectively mitigating data congestions and saving energies, the RR protocols are implemented and the resulting nonlinear systems become the so-called protocol-induced periodic ones. Taking such a periodic characteristic into account, an NN-based observer is first proposed to reconstruct the system states where a novel adaptive tuning law on NN weights is adopted to cater to the requirement of performance analysis. In addition, with the established boundedness of the periodic systems in the mean-square sense, the desired observer gain is obtained by solving a set of matrix inequalities. Then, an actor–critic NN scheme with a time-varying step length in adaptive law is developed to handle the considered control problem with terminal constraints over finite-horizon. Some sufficient conditions are derived to guarantee the boundedness of estimation errors of critic and actor NN weights. In view of these conditions, some key parameters in adaptive tuning laws are easily determined via elementary algebraic operations. Furthermore, the stability in the mean-square sense is investigated for the discussed issue in infinite horizon. Finally, a simulation example is utilized to illustrate the applicability of the proposed control scheme. <s> BIB006
A CYBER-physical system (CPS), a fast growing research area, is a highly integrated system of physical components involving sensors, actuators, and various equipments, as well as cyber, possessing ubiquitous computation and efficient communication. From the engineering point of view, CPSs are considered as the most promising industrial systems including transportation networks, energy systems, water/gas distribution networks, and unmanned factories. For example, multiple industrial robots with an inertial navigation device or various sensors are programmed for the movement along a programmed trajectory to cooperatively complete production tasks BIB002 ,  . The main advantage of these systems is that the tight coordination of cyber and physical elements provides greater autonomy, efficiency, functionality, reliability, and adaptability. Furthermore, industrial CPSs are regarded as a core ingredient in the so-called fourth industrial revolution BIB004 ,  , and lots of efforts are made to establish their important position, such as Industry 4.0 in Germany and Industrial Internet in the USA. Industrial CPSs are large-scale, geographically dispersed, federated, cooperative, and life-critical systems, in which lots of sensors and actuators are embedded and networked together to facilitate real-time monitoring and closed-loop control. In addition, the implementation of industrial CPSs largely depends on sensor networks and distributed control networks. In other words, these two networks are usually indispensable in a largely deployed CPS architecture BIB001 . Specifically, sensor networks are usually deployed in the interior or neighboring of plants to gather various critical information with the purpose of making correct perception of the physical plants. With the help of these information, actuators can have the opportunity to do real-time reaction to some changes of physical plants. As such, a closed loop is formed when integrating cyber and physical worlds through both communicating between sensors and actuators and operating plants via actuators BIB005 . In the past few years, many of commercial sensors and actuators equipped with some communication and data processing capabilities are made available benefiting from the hard work of research institutions and companies from around the world. As is done for almost all of real-world engineering systems, the model-based performance analysis of an industrial CPS plays an important role in understanding and adjusting its dynamic behavior. Because of the limitation of geographic space and various resources in energy and communication aspects, there is an ever-increasing need to execute: distributed control for satisfying reliability and scalability requirements while maintaining stability performance; and distributed filtering for achieving scalability and disturbance attenuation capability while ensuring expected filtering accuracy. However, traditional tools developed in the central paradigm are not feasible to meet the demands of industrial CPSs mainly due to their inherent dynamic nature. Specifically, on the one hand, the complexity of industrial CPSs, in terms of its degree or intensity, could be great enhanced due to various network-induced phenomena and employed communication protocols BIB006 , BIB003 . On the other hand, the varying topology, coming from connection failures or cyber-attacks  , gives rise to an obstacle of the application of developed analysis approaches. As such, it is of both theoretical significance and practical importance to develop an effective framework of performance analysis and synthesis under the distributed paradigm. It is thus desirable to survey what results have been developed in the field of industrial CPSs modeled by differential dynamics equations and further identify what challenges need to be dealt with. For this purpose, this paper intends to provide a review of the state-of-the-art of distributed control and filtering of industrial CPSs on sensor networks, manipulators, and power systems (see Fig. 1 for the organization). Specifically, for realtime monitoring, we identify key techniques of Kalman-based filtering algorithms, review typical filter structures utilized in a non-Kalman framework, and provide a systematic performance analysis from three aspects: calculation burden, communication burden, and scalability. For distributed closed-loop control, we first survey the latest advances on distributed control of manipulators in industrial automation systems and then summarize typical distributed control strategies in microgrids via droop characteristics with the requirements of power sharing and voltage and frequency regulation. Furthermore, we summarize recent developments on distributed security control of industrial CPSs when a cyber-attack is a concern. Finally, we raise some challenging issues to guide the future research.