How organizations use ICT:

Technological advancements in  process monitoring,  control  and industrial automation in recent years have improved the productivity of virtually all manufacturing industries throughout the world.  Almost all the controls installed in new plants or plant expansions are Digital Control Systems (DCS) connected by digital networks.

 Process control is extensively used in industry.  It is the use of computers or microprocessors to control a process.  Process control enables automation.  This means that a small staff of operating personnel can operate a complex process from a central control room.

 Enables mass production of continuous processes eg oil refining, paper manufacturing, chemical processing, temperature control etc  It is also used in the food and beverage industries

 Chilling the temperature in an industrial refrigeration plant is a process that has a specific, desired outcome to reach:  To maintain a defined temperature (e.g. 2°C) temperature  And keep it constant over time.

 A variable is a piece of data that can change.  The temperature is the controlled variable.  It is also the input variable since it is measured by a thermometer and used to decide whether to heat or not to heat.

 The desired temperature (2°C) is the setpoint.  The state of the chiller (e.g. the activation of the actuator to switch the compressor on or off) is called the manipulated variable since it is subject to control actions.

 Using the example on the previous slide, the plant temperature would be an input to the PLC.  The logical statements would compare the setpoint to the input temperature and determine whether more or less compression was necessary to keep the temperature constant.  A PLC output would then either activate the actuator to switch the compressor on, an incremental amount, depending on whether more or less chilling was needed.

 Most process control is overseen by PLCs rather than by computers.  A PLC is a type of microprocessor that is used for a single purpose.

A programmable logic controller, or a PLC, is used to: 1. read a set of digital and analog inputs 2. apply a set of logic statements 3. generate a set of analog and digital outputs.

 A PLC is able to accept analogue and digital inputs  It makes extensive use of analogue to digital conversion (as well as digital-to-analogue conversion!)  A set of logic statements is used to compare the input with a pre-set value.

 Depending on the results of that comparison, it activates the output devices.  PLCs are not really used in home central heating systems (where the pre-set value might change to suit seasonal conditions)  They are used in situations where the pre-set value is a constant, ie industrial refrigeration systems

 Proportional-Integral- Derivative (PID) algorithm  These are used with closed-loop systems

 A physical variable (ie temperature) is continuously monitored by a sensor connected to the PLC  The outputs from the controller affect the input (ie the temperature) A Closed Loop System

 These control continuous processes  The purpose of the PLC is to make the input value equal to the pre-set one and maintain it there.  PID is the best means of doing this

 The PID calculates the difference between the input value and the pre-set value.  It causes the PLC to make proportional changes to the output  so that the pre-set temperature is eventually reached.

 If the temperature in an industrial heating system is lower than the required temperature, the PID calculates the difference  Instead of switching the heater on until the pre-set value is reached, the PLC switches it on for a short time  Then checks the difference again

 If there is still a difference, it switches the heater on again for another small burst  This is repeated until the required temperature is reached.

There are three types of process control:  Batch Process Control  Continuous Process Control  Discrete Process Control

 Some applications require that specific quantities of raw materials be combined in specific ways for particular durations to produce an intermediate or end result.  One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product.

 Other important examples are the production of food, beverages and medicine.  Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds).

 The amount of each ingredient that is added is controlled by the computer  So is the length of time for each stage  So is the temperature

 Found in many manufacturing and packaging applications.  Robotic assembly, such as that found in car manufacture, can be characterized as discrete process control.  Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.

 Specific items are produced.  It is like an on/off or stop/start process.  Fitting car wheels:  A robot fits a wheel to a car  The car moves on to the next stage  The robot stops  The next car comes along  The robot fits the wheel to the car…  And so on.  In between waiting for each car to arrive, the robot stops

 Continuous process control refers to processes that appear unending.  A good example is the maintaining of temperature in confined surroundings – eg industrial refrigeration  Other examples include oil/petroleum refining, the production of plastics or paper production.

 Some important continuous processes are the production of fuels, chemicals and plastics.  Continuous processes in manufacturing are used to produce very large quantities of product per year (millions to billions of pounds).

 Applications having elements of discrete, batch and continuous process control are often called hybrid applications.