IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 9, NO. 1, FEBRUARY 2013 403 Network-Induced Constraints in Networked Control Systems—A Survey Lixian Zhang, Member, IEEE, Huijun Gao, Senior Member, IEEE, and Okyay Kaynak, Fellow, IEEE Abstract—Networked control systems (NCSs) have, in recent years, brought many innovative impacts to control systems. How- ever, great challenges are also met due to the network-induced imperfections. Such network-induced imperfections are handled as various constraints, which should appropriately be consid- ered in the analysis and design of NCSs. In this paper, the main methodologies suggested in the literature to cope with typical network-induced constraints, namely time delays, packet losses and disorder, time-varying transmission intervals, competition of multiple nodes accessing networks, and data quantization are sur- veyed; the constraints suggested in the literature on the first two types of constraints are updated in different categorizing ways; and those on the latter three types of constraints are extended. Index Terms—Analysis and design of networked control systems, network-induced constraints, networked control systems. I. INTRODUCTION N ETWORKED control systems (NCSs) are control systems in which the components, i.e., controllers, sensors and actu- ators are spatially distributed and connected via a certain digital communication network The networks can be either the con- trol networks that have been around for a considerable amount of time for specialized real-time purposes such as control area network (CAN), BACnet, Fieldbus, or, more recently, the wire- line or wireless Ethernet, even Internet, for general-purpose data communication tasks. As commented in almost all the literature on NCSs, the motivations to construct such a control system via networks are the low installation and maintenance costs, high reliability, increased system flexibility, and decreased wiring. Such benefits have given a great impetus to extensive applica- tions of NCSs in many fields, such as the few that are briefly discussed hereafter. Vehicle industry: In a typical modern automobile, for in- stance, the technology of CAN-based data communication among almost all the electromechanical modules eliminates the problem of extensive wiring in a limited space. The interactions of the subsystems, e.g., engine control, transmission control, Manuscript received July 30, 2011; revised December 09, 2011; accepted June 22, 2012. Date of publication September 18, 2012; date of current ver- sion December 19, 2012. The work was supported in part by National Nat- ural Science Foundation of China (60904001), Outstanding Youth Science Fund of China (60825303) and 973 Project (2009CB320600) in China. Paper no. TII-11-357. L. Zhang and H. Gao are with the Space Control and Inertial Technology Research Center, Harbin Institute of Technology, Harbin 150080, China (e-mail: lixianzhango@hit.edu.cn; hjgao@hit.edu.cn). O. Kaynak is with the Department of Electrical and Electronic En- gineering, Bogazici University, Bebek, Istanbul 80815, Turkey (e-mail: okyay.kaynak@boun.edu.tr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TII.2012.2219540 Fig. 1. The CAN-based networked control systems in a typical automobile (from [2], reproduced with permission). anti-locked braking system (ABS), and acceleration slip regu- lation (ASR) system, are networked [1]. An illustration on the use of CAN in an automobile is given in Fig. 1 [2]. Network-Based Process Control Engineering: Nowadays, the Fieldbus, industrial Ethernet, etc., have been widely and successfully applied in many process control engineering sys- tems, such as the wastewater treatment process, as illustrated in Fig. 2 [3]. In this application, information on various process variables, e.g., water level, pH factor, temperature, chemical oxygen demand (COD), are collected by the control devices (PLCs) located at separated stations, and then transmitted via industrial Ethernet to central control rooms for processing and integrated analysis. Teleoperation: Generally, teleoperation is the execution of a task by a pair of master–slave manipulators in which the latter may be located a long distance away on Earth or even in space [4]. An illustrative scheme of Internet-based teleopera- tion can be seen in Fig. 3. Other applications of NCSs can be found in power systems [5], transportation systems [6], and control systems [7], etc. In recent years, to ease the practical application of NCSs, con- siderable efforts have been spent and some progress has been made in topics such as the following: 1) modeling of NCSs; 2) stability and performance analysis; 3) networked control and estimation; 4) network-based fault detection and tolerance; 5) identification via networks; Among the vast literature on NCSs that is available to date, we refer the readers especially to the books [8]–[10], survey papers [11]–[14], special issues [15]–[19], Ph.D. dissertations [20]–[22], and the numerous references therein to enable them to see the state of the art in NCSs. 1551-3203/$31.00 © 2012 IEEE