INDUSTRIAL CONTROL

SYSTEMS &

COMPUTER PROCESS CONTROLCOMPUTER PROCESS CONTROL

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INDUSTRIAL CONTROL - DEFINED

The automatic regulation of unit operations and theirassociated equipment as well as the integration andcoordination of the unit operations into the largerproduction system� Usually refers to a manufacturing operation� Usually refers to a manufacturing operation

� Can also apply to material handling or other equipment

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INDUSTRIAL CONTROL SYSTEMS

� Process Industries vs. Discrete Manufacturing Industries

� Continuous vs. Discrete Control

Computer Process Control� Computer Process Control

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CONTINUOUS AND DISCRETE

VARIABLES AND PARAMETERS

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DISCRETE VARIABLES AND PARAMETERS

Categories:

� Binary - they can take on either of two possible values, ON or OFF, 1 or 0, etc.

� Discrete other than binary - they can take on more than � Discrete other than binary - they can take on more than two possible values but less than an infinite number of possible values

� Pulse data - a train of pulses that can be counted

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CONTINUOUS CONTROL

� Usual objective is to maintain the value of an outputvariable at a desired level

� Parameters and variables are usually continuous

� Similar to operation of a feedback control system

� Most continuous industrial processes have multiplefeedback loopsfeedback loops

� Examples of continuous processes:

� Control of the output of a chemical reaction thatdepends on temperature, pressure, etc.

� Control of the position of a cutting tool relative toworkpart in a CNC machine tool

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TYPES OF CONTINUOUS PROCESS CONTROL

� Regulatory control

� Feed forward control

� Steady-State optimization

� Adaptive control� Adaptive control

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REGULATORY CONTROL

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FEEDFORWARD CONTROL

COMBINED WITH FEEDBACK CONTROL

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STEADY STATE (OPEN-LOOP)

OPTIMAL CONTROL

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ADAPTIVE CONTROL OPERATES IN A

TIME-VARYING ENVIRONMENT

� The environment changes over time and the changes havea potential effect on system performance

� Example: Supersonic aircraft operates differently insubsonic flight than in supersonic flight

� If the control algorithm is fixed, the system may perform� If the control algorithm is fixed, the system may performquite differently in one environment than in another

� An adaptive control system is designed to compensate forits changing environment by altering some aspect of itscontrol algorithm to achieve optimal performance

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ADAPTIVE CONTROL SYSTEM

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TWO BASIC REQUIREMENTS FOR

REAL-TIME PROCESS CONTROL

1. Process-initiated interrupts

� Controller must respond to incoming signals from the process (event-driven changes)

� Depending on relative priority, controller may have to interrupt current program to respondto interrupt current program to respond

2. Timer-initiated actions

� Controller must be able to execute certain actions at specified points in time (time-driven changes)

� Examples: (1) scanning sensor values, (2) turning switches on and off, (3) re-computing optimal parameter values

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OTHER COMPUTER CONTROL

REQUIREMENTS

3. Computer commands to process

� To drive process actuators

� System initiated events - communications between computer and peripherals

� Program initiated events - non-process-related actions, such as printing reports

4. System- and program-initiated events

5. Operator-initiated events – to accept input from personnel

� Example: emergency stop14

FORMS OF COMPUTER PROCESS CONTROL

1. Computer process monitoring

2. Direct digital control (DDC)

3. Distributed control systems

4. Numerical control and robotics4. Numerical control and robotics

5. Programmable logic control

6. Supervisory control

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APPLICATION

� Continuous or semi-continuous production operationsinvolving materials such as chemicals, petroleum, foods,and certain basic metals.

� In these operations the products are typically processed ingas, liquid, or powder form to facilitate flow of thegas, liquid, or powder form to facilitate flow of thematerial through the various steps of the production cycle.

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� Measurement of important process variables such as temperature, flow rate, and pressure,

� Execution of optimizing strategy.

� Actuation of devices as valves, switches, and furnaces that enable the process to implement the optimal strategyenable the process to implement the optimal strategy

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COMPUTER PROCESS MONITORING

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Batch Furnace commissioned by Bickley Inc., USA

Nominal temperature: up to 900’C

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(A) PROCESS MONITORING, (B) OPEN-LOOP

CONTROL, AND (C) CLOSED-LOOP CONTROL

(a)

(b)(b)

(c)

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COMPONENTS OF A

DIRECT DIGITAL CONTROL SYSTEM

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DISTRIBUTED CONTROL SYSTEMS (DCS)

� Multiple microcomputers connected together toshare and distribute the process control workload

� Features:

� Multiple process control stations to control individualloops and devicesloops and devices

� Central control room where supervisory control isaccomplished

� Local operator stations for redundancy

� Communications network (data highway)

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DISTRIBUTED CONTROL SYSTEM

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DCS ADVANTAGES

� Can be installed in a very basic configuration, thenexpanded and enhanced as needed in the future

� Multiple computers facilitate parallel multitasking

� Redundancy due to multiple computers

� Control cabling is reduced compared to central controller� Control cabling is reduced compared to central controllerconfiguration

� Networking provides process information throughout theenterprise for more efficient plant and process management

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Computerized Process Control

improves improves

Sugar Refinery Production

NUMERICAL CONTROL AND ROBOTICS

� Computer numerical control (CNC) – computer directsa machine tool through a sequence of processing stepsdefined by a program of instructions

� Distinctive feature of NC – control of the position of a tool

relative to the object being processedrelative to the object being processed

� Computations required to determine tool trajectory

� Industrial robotics – manipulator joints are controlledto move and orient end-of-arm through a sequence ofpositions in the work cycle

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PLASTIC INJECTION MOLDING MACHINE BLD 280

CNC USE FOR…

A) MULTIPLE HYDRAULIC CORE PULLING

B) CYLINDER TRANSDUCER CONTROL

C) MULTIPLE OPTIONS OF ...

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ROBOTS

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PROGRAMMABLE LOGIC CONTROLLER (PLC)

Microprocessor-based controller that executes a program ofinstructions to implement logic, sequencing, counting, andarithmetic functions to control industrial machines andprocesses

� Introduced around 1970 to replace electromechanical relay� Introduced around 1970 to replace electromechanical relaycontrollers in discrete product manufacturing

� Today’s PLCs perform both discrete and continuous controlin both process industries and discrete product industries

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PLC

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BLOWMOLDINGMACHINE

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PONGRASS MODEL 32H

32MM CAPACITY MANDREL TUBE BENDING MACHINE

PLC CONTROL USE FOR RISING CLAMP & LENGTH STOP BAR

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SUPERVISORY CONTROL

In the process industries, supervisory control denotes a control system that manages the activities of a number of integrated unit operations to achieve certain economic objectives

In discrete manufacturing, supervisory control is the In discrete manufacturing, supervisory control is the control system that directs and coordinates the activities of several interacting pieces of equipment in a manufacturing system

� Functions: efficient scheduling of production, tracking tool lives, optimize operating parameters

� Most closely associated with the process industries

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SUPERVISORY CONTROL SUPERIMPOSED

ON PROCESS LEVEL CONTROL SYSTEM

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Introduction to SCADA

� A subset of PCS systems that manage systems over very large geographic areas are typically referred to as Supervisory Control and Data Acquisition systems or SCADA systems. SCADA systems make up the critical infrastructure associated with electric utilities, water and

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associated with electric utilities, water and sewage treatment plants, and large-scale transportation systems like interstate rail.

� Supervisory Control and Data Acquisition systems are basically Process Control Systems (PCS), specifically designed to automate systems such as traffic control, power grid management, waste processing etc.

Aspects of SCADA

�Most often, a SCADA system will monitor

and make slight changes to function

optimally

�SCADA systems are considered closed

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loop systems and run with relatively little

human intervention

�One of key processes of SCADA is the

ability to monitor an entire system in real

time

SCADA systems in INDIA

� SCADA systems are still to come into widespread

infrastructural use in India

� Now, they are being used primarily for

automation in industrial production, and to some

extent for specialized process control

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extent for specialized process control

� Ranbaxy Labs and Voltas are two of the

companies in India using SCADA systems for

controlling a variety of processes

� Other examples of pseudo-SCADA usage also

observed

Components of SCADA

� The basic structure of PCS systems is made up of a wide range of components and several different communication protocols. The operation of such a large and diverse infrastructure requires an extensive network of electronic devices, communications, and control and monitoring

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communications, and control and monitoring systems, such as:

� Field Devices

– Remote Terminal Units (RTU)

– Programmable Logic Controllers (PLC)

– Intelligent Electronic Devices (IED)

– Programmable Automation Controller (PAC)

Components of SCADA� Management systems to monitor and control field equipment

– Human Machine Interface (HMI)

– SCADA Controller or Real Time Processor

– Historian

Communications

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� Communications

– Ethernet, Wireless, Serial

– Modbus, DNP3

– ICCP, OCP

Construction of SCADA

� SCADA systems are primarily control systems. A

typical control system consists of one or more

remote terminal units (RTU) connected to a

variety of sensors and actuators, and relaying

information to a master station.

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information to a master station.

A typical 3-tiered approach to SCADA

systems

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�Sensors perform measurement, and actuators perform control.

�Sensors get the data (supervision and data acquisition)

Actuators perform actions dependent on

Sensors & Actuators

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�Actuators perform actions dependent on this data (control).

�The processing and determination of what action to take, is done by the master control system (i.e. SCADA).

RTU/ PLC

�Remote Terminal Units (RTUs) connect to sensors

�Convert sensor signals to digital data and sending digital data to the supervisory system

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system

�Operate actuators as per control signals received/ generated

�Provide local processing capability

�Applications that had previously been programmed at the central master station can now be programmed at the RTU.

Master Station

Master stations have two main functions:

• Periodically obtain data from RTUs/PLCs (and other master or sub-master stations)

• Control remote devices through the operator station

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• Control remote devices through the operator station

Other duties include trending, alarm handling, logging and archiving, report generation, and facilitation of automation. These duties may be distributed across multiple PCs, either standalone or networked.

Segregation of functions of a SCADA system

into a functional representation

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Data Flow

� Data acquisition begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required

� Data is then compiled and formatted in such a way that a control room operator using the HMI

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way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls

� Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing.

SCADA of Cooling System

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Applications of SCADA

� Electric power generation, transmission &

distribution (USA)

� Water supply, sewage & drainage (UK &

Netherlands)

� Buildings, facilities & environment

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� Buildings, facilities & environment

� Manufacturing (Robots-Toyota, Porsche, VW)

� Traffic Signals (USA)

� Mass transit (Rail crossing gates, USA)

� Suburban Railway system (Mumbai, Western

Railway)

Bibliography

� SCADA-IBM whitepaper

� Whitepaper on SCADA systems security-Arjun

Venkatraman

� SACAD-A. Daneels-CERN, Geneva

www.wikipedia.org

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� www.wikipedia.org

Thank You

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Thank You