CPU Control unit ALU Registers Ports Other auxiliary units Output devices Monitor Printer Other devices Input devices Keyboard Mouse Other devices Memory RAM (SRAM, DRAM) ROM (PROM, EPROM, EEPROM) Floppy disk Hard disk CD ROM input output Data outData in “A computer is an electronic device for the fast and accurate processing of data/information under the control of a stored logical sequence of instructions called a software program.” All computers, regardless of their size, have the similar general design which essentially consist of CPU, memory, I/O devices, communication slots and ports, electronic circuits and a clock.

Application Software System Hardware (Processor, Memory, Cards, etc. etc..) Drivers Operating System IPC Multi-tasking Multi-threading External devices and Units “An operating system is a system program that control the hardware and other software of the computer and when it is opened it brings the computer system into a mode from where it is easier to run other applications. OS provides an ‘abstraction layer’ between the application software and the low level hardware by freeing the programmer from any concern about the details of the underlying hardware of the computer. In summary, the OS manages the resources. The resources are application software, data, files, information and peripheral hardware such as floppy drive, hard drive, CD drive, printer, scanner, etc.”

DOS RESOURCES DOS RESOURCE-1 DOS RESOURCE-2 DOS RESOURCE-n DOS Network (a) (b) The need for Distributed Operating System (DOS) arises only when the computer resources are apart from each other i.e., when they are found to be geographically distributed.

Preprocessor Compiler Assembler Link editor Source code in High-level language Target language (Could be Hexadecimal code) Object code Libraries MACHINE LANGUAGE (Executable code) To write a program a high- level programming language is necessary. Compiler is a program that reads a program written in one high-level computer language, called the source language, and translates it into an equivalent program in another language, called the target language. The target language is then converted to object code by the assembler.

The ‘MATLAB Command Window MATLAB is a software tool that stands for Matrix Laboratory. It provides facilities like system analysis, matrix computation, signal processing and graphics.

MATLAB Editor/Debugger

MATLAB window used for saving the m-file in the directory.

A sign wave of 50 Hz generated by using MATLAB simulation software.

A signal containing fundamental frequency of 50 Hz and superimposed by a third harmonic component of 10% that of fundamental. Generated by using MATLAB simulation software.

A plot of the following function. The plot was obtained by using MATLAB program.

(a)The signal at hand; (b)Its DFT MATLAB provides powerful interactive plotting capabilities that allows to visualize data, equations and results.

SERVER (Central database) Client-1 Client-3Client-2 Operating System Client-server (CS) architecture is an extension of the centralised configuration. Data is mostly processed in clients. Client-server conformant application software can give greater viability to distributed processing.

APPLICATION LAYER PRESENTATION LAYER SESSION LAYER TRANSPORT LAYER NETWORK LAYER DATALINK LAYER PHYSICAL LAYER APPLICATION LAYER PRESENTATION LAYER SESSION LAYER TRANSPORT LAYER NETWORK LAYER DATALINK LAYER PHYSICAL LAYER MEDIUM OSI MODEL Data path Device-1Device-2 AB Computer network is a network of computers. The network is also called data network. Traditionally, any kind of data communication between the computers is governed by a reference model called the ISO/OSI RM (International Standards Organization/Open System Interconnection Reference Model). The ISO/OSI RM is a specification guidelines based upon which the computer communication systems have been developed and designed. The guideline defines the essential services that are required for achieving reliable and faithful data communications. The specification constitute a collection of services, which have been partitioned into seven layers.

4-20mA signal S=sensor A=actuator CONSOLE CENTRAL CONTROLLER Junction Box (Analogue (Multiplexer) S A S A Other I/O devices As far as communication between the controller and the I/O devices are concerned, all control implementations are broadly comes under three categories. Centralised control Distributed control Hybrid control Centralized control scheme, a conventional one, has a central processing unit, called central controller. The central controller communicates with a number of field devices through parallel link

A DCS system is simply a network of controllers. The network thus formed is referred to as control network. The entire task which was residing in a central controller is by far divided among many controllers, resulting in a smooth execution of the whole control process.

The heart of a DCS is node. A node consists of a microprocessor to execute task, RAM/PROM/EEPROM for storage of data/code/protocol etc., Ports for interfacing with the field devices (e.g., sensors, actuators, etc.), and transceiver to interface with other nodes to form the control network. A node can be called a smart device as it is capable of executing the task processing signal, data, information and message at the field-level or the device level.

Real-time systems are usually reactive systems that are in continual interaction with their environments. Control systems for real-time applications are characterised by their ability to support strong time constraints. Control loops can be formed locally for reducing the network traffic.

Star-ring (token passing) peer-to-peer (linear) = NODE Tree (hierarchical) Star (master-slave) Messages are transmitted from one node to the other through the network that complies with specific topology.

The design and implementation of DCS systems consider three major elements; Target application platform such as process/plant/syste m. Electronics such as processor, transceiver, communication media, I/O interfaces, etc. Development tools such as host computer with OS and application software

A typical fieldbus-based Distributed Control System scenario

The fieldbus protocol does not include all the services of all the layers of ISO/OSI model. This is an essential requirement of almost all control networking systems. The reduced version of the ISO/OSI layers aid strong real-time requirements.

In order to realize fieldbus- based reliable DCS drawn upon representative target platforms the design methodology involves problem identification or specification, segmentation or decentralisation, development and testing. Regardless of the system complexity, in the DCS the stages involved in the design and development process are shown in the figure.

A typical integration of data and control network for monitoring and control of target applications