NCS are distributed real-time control systems consisting of the plant, sensors, controllers, actuators
and a shared data network that is used for communication between the components of the system
[60]. A general NCS layout is depicted in Figure 1. The use of data networks in closed-loop
control systems is mainly motivated by reduced system wiring, price, flexibility and modularity o
implementation, and the possibility of having plug and play devices [6], [60]. For example, in th
car industry, the CAN bus (Controller Area Network) has become very popular, because th
measurements from numerous sensors can be transmitted over a single bus instead of wiring each
sensor with its own cable. Nowadays, a car can have three CAN buses with different speeds; one fo
electronic stability control and the anti-lock braking system (high-speed), another for the driver’
information management (navigation system, radio; medium speed) and a third one for the centra
locking system and other low-speed functions. Whereas cars are small in size, industrial processe
are large and the savings in cabling can be dramatic when using a fieldbus instead of traditiona
cables and wires. Besides fieldbuses, Ethernet is being used in industrial environments fo
automation and production machine control. Ethernet provides a high-speed network and it can
be implemented with standard devices such as access points, routers and hubs that are commercia
off-the-shelf (COTS) equipment and thus inexpensive.
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