Networked Control System: Fundamentals and Applications

By Fouad Sabry

What Is Networked Control System

A control system that closes its control loops through the use of a communication network is referred to as a networked control system, or NCS for short. The fact that control and feedback signals are passed between the various components of an NCS in the form of information packages and transmitted over a network is the defining characteristic of this type of control system.

How You Will Benefit

(I) Insights, and validations about the following topics:

Chapter 1: Networked control system

Chapter 2: Distributed control system

Chapter 3: Model predictive control

Chapter 4: Process automation system

Chapter 5: Building automation

Chapter 6: Profinet

Chapter 7: EtherCAT

Chapter 8: Control reconfiguration

Chapter 9: Hardware-in-the-loop simulation

Chapter 10: Internet of things

(II) Answering the public top questions about networked control system.

(III) Real world examples for the usage of networked control system in many fields.

(IV) 17 appendices to explain, briefly, 266 emerging technologies in each industry to have 360-degree full understanding of networked control system' technologies.

Who This Book Is For

Professionals, undergraduate and graduate students, enthusiasts, hobbyists, and those who want to go beyond basic knowledge or information for any kind of networked control system.

• Language: English
• Publisher: One Billion Knowledgeable
• Release date: Jun 24, 2023

Book preview

Chapter 1: Networked control system

A control system that uses a communication network to close control loops is known as a networked control system (NCS). The exchange of control and feedback signals in the form of information packages between the system's components through a network is what distinguishes an NCS from other systems.

{End Chapter 1}

Chapter 2: Distributed control system

A distributed control system (DCS) is a computerized control system for a process or plant that often has numerous control loops. Autonomous controllers are spread throughout the system, but there is no supervisory control from a central operator. Contrast this with systems that employ centralized controllers, either separate controllers housed within a central computer or controllers situated at a central control room. By locating control functions close to the processing plant and using remote monitoring and supervision, the DCS concept improves reliability and lowers installation costs.

The appeal of distributed control systems was that the manufacturer would provide both the local control level and central supervisory equipment as an integrated package, thereby lowering the risk associated with design integration. Distributed control systems first appeared in large, high value, safety-critical process industries. Although the functionality of today's supervisory control and data acquisition (SCADA) and distributed control systems (DCS) systems is very similar, DCS is typically used in large continuous processing facilities where high reliability and security are crucial and the control room is not located far from the production area.

The main quality of a DCS is reliability, which results from the distribution of control processing among system nodes. This lessens the impact of one CPU failing. In contrast to a central computer failure, which would disrupt the entire process, a processor failure will just impact one part of the plant's process. By eliminating potential network and central processing delays, the deployment of computing power close to the field Input/Output (I/O) connection racks also guarantees quick controller processing times.

Using computerized control, the accompanying diagram illustrates functioning manufacturing stages.

Using the diagram as a guide; Field devices like flow and temperature sensors, as well as finishing control components like control valves, are found in Level 0.

The industrialized Input/Output (I/O) modules and related distributed electronic processors are found in Level 1.

The supervisory computers at Level 2 provide the operator control screens and gather data from the system's processor nodes.

Level 3 is the production control level, which is concerned with monitoring production and monitoring targets but does not actively control the process.

The production schedule level is level 4.

The functional levels of a conventional DCS are levels 1 and 2, when all equipment is a part of an integrated system from a single manufacturer.

Levels 3 and 4 are more like production control and scheduling than strictly tight process control in the conventional sense.

The operator graphical displays and processing nodes are connected by proprietary or industry-standard networks, and dual redundancy cabling via various routes improves network dependability. By positioning the I/O modules and their associated processors close to the processing facility, this distributed design also decreases the quantity of field cabling.

The processors decide which control actions should be signaled by the output modules after processing the information they receive from the input modules. The field inputs and outputs can be two-state signals, such as relay contacts or a semiconductor switch, or analog signals, such as a 4-20 mA DC current loop.

The material flow through the plant is managed by DCSs using setpoint control, which is coupled to sensors and actuators. A PID controller that is supplied by a flow meter and uses a control valve as the final control element is a common application. The controller is instructed to open a valve by the controller after the DCS delivers the setpoint that the process needs in order to attain and maintain the intended setpoint. (For a schematic, see the 4-20 mA diagram.).

Several thousand I/O points and very massive DCS are used in major chemical and oil refineries. Processes can encompass a variety of things besides fluidic flow through pipes, such as paper mills and the quality controls that go along with them, variable speed drives and motor control centers, cement kilns, mining operations, ore processing facilities, and many more.

To increase the reliability of the control system, dual redundant processors with hot switch over on fault are an option for DCSs in very high reliability applications.

The primary field signaling standard has historically been 4-20 mA, however contemporary DCS systems can also support fieldbus digital protocols including Foundation Fieldbus, profibus, HART, modbus, PC Link, etc.

Applications for neural networks and fuzzy logic are also supported by modern DCSs. Recent research focuses on the creation of distributed controllers that are optimized for a certain H-infinity or H 2 criterion.

Distributed control systems (DCS) are specialized systems used in batch- or continuous-oriented industrial processes.

Processes that could make advantage of a DCS include:

Chemical plants

Refineries and petrochemicals

Paper and pulp factories (see also: quality control system QCS)

systems for power plants and boilers

Nuclear power plants

Environmental control systems

Water management systems

Water treatment plants

Sewage treatment plants

consuming and preparing food

Agrochemical and fertilizer

Metal and mines

Automobile manufacturing

Metallurgical process plants

Pharmaceutical manufacturing

Sugar refining plants

Agriculture applications

Large industrial plants' process control has gone through a number of stages of development. Control would initially come from panels close to the processing plant. There was no overall perspective of the process, and it took a lot of effort to manage these scattered panels. The logical next step was to send all plant measurements to a central control room that was constantly manned. In actuality, this was the centralization of every localized panel, with the benefits of lower staffing levels and simpler process oversight. The controllers were frequently hidden behind the panels in the control room, and all automatic and human control outputs were sent back to the plant. Although this structure offered a central control focus, it was rigid since each control loop had its own controller hardware and needed constant operator mobility within the control room to see various aspects of the operation.

These discrete controllers could be replaced with computer-based algorithms hosted on a network of input/output racks with their own control processors thanks to the development of electronic processors and visual displays. The visual display in the control room or rooms might be connected to these, which could be dispersed throughout the facility. the emergence of the distributed control system.

With the advent of DCSs, plant controls like cascaded loops and interlocks could be easily connected,