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2.1 cControl systems


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2.1 cControl systems

  1. 1. How organizations use ICT? Section - 1 In this chapter, we will learn about ICT systems and how organizations use them. In particular, we will learn about the use of ICT in a wide range of applications.
  2. 2. Topics to be covered • Control Systems • Working practices • Advertising • Teaching and learning • Publishing • Time management • Data management • Payroll applications • Technical and customer support • Art and design work
  3. 3. 2.1 Control Systems • A control system is one that uses microprocessors or computers to control certain physical conditions, either keeping them the same over a period of time or varying them according to pre-defined values and lengths of time. • Physical conditions or variables that are controlled by computer and microprocessors include – temperature, pressure, humidity, light and moisture. • Examples of control systems that have to maintain one or more of these variables are: – Air-conditioning systems – Refrigeration – Central-heating systems – Car manufacture – Medical applications – Process control
  4. 4. Air-conditioning Systems • An air conditioner is a closed system of copper tubes in the form of coils containing a chemical liquid (called the refrigerant) that can be easily converted to a gas and back to liquid again. • There are many sophisticated systems that have sensors built into the air- conditioning unit itself. • There are usually two temperature sensors that monitor the temperature of the refrigerant, allowing the system to control the amount of heat being let out of the system. • A temperature sensor may also be installed in each of the room the system operates. • A pressure sensor that monitors the pressure of the refrigerant so that the valve can be controlled to reduce or increase the flow of refrigerant. • These systems control the heat loss from individual rooms by altering the speed of the fans or merely by switching them on or off. • The person in the room uses a touch screen to input the temperature.
  5. 5. Air-conditioning Systems
  6. 6. Refrigeration • The refrigeration process works on much the same principle as air conditioning. • The condensing unit is at the rear of the refrigerator and the evaporating unit is inside the refrigerator. • Main inputs – – Temperature sensor to monitor the temperature inside the refrigerator. – Contact switch or pressure sensor for the door. – A number pad or similar device to input the required temperature. • The microprocessor compares the data from the sensor (after being digitized by an analogue-to-digital convertor [ADC]) with the pre-set value input by the user. • Outputs from the system may include: – Light-emitting diodes (LEDs) indicating the current temperature of the inside of the refrigerator. – Warning buzzers if the door is left open.
  7. 7. Refrigeration
  8. 8. Central-heating systems • Most central-heating systems use water as the medium to get heat from the central source (the boiler) to all the areas to be heated. • Main components – – A Boiler is used to heat the water in the system. – Hot water cylinder stores the water being heated in the boiler – A pump causes the heated water from the cylinder to flow round the system to the radiators. – Radiators are the metal panels that are fixed to the wall in the rooms that need heating. • In a microprocessor-controlled central-heating system, user press the touch screen to select the temperature they want. The microprocessor reads the data from a temperature sensor on the wall and compares it with the value the user has requested. • The microprocessor usually has the capacity to control the times at which the system switches itself on and off. • Outputs from the system may include: – Separate Actuators: one opens the gas valves in the boiler and the other switches the pump on. – Warning buzzers if the door is left open.
  9. 9. Central-heating systems
  10. 10. Car manufacture • Computer-controlled robots are used in various manufacturing industries, including the manufacture of cars. • Most robots are controlled by the use of actuators in the form of electric motors. • A stepper motor is a more popular type of motor for robotic use. • The industrial robots used in car manufacture are generally robot arms rather than a complete robot. The most common type of robot arm consists of seven (7) metallic sections with six (6) joints, each joint being controlled by a separate stepper motor. • An end effector is the device that is attached to the end of the robot arm to carry out various tasks. • A robot arm may use any particular type of end effector but it has to be programmed correctly to execute the task that it is supposed to in its controller. • Industrial robots are designed to perform exactly the same operation over and over again. • In order that the robot knows how to do its job, the programmer guides the arm through each step – – Either by physically holding the arm (and having sensors attached to their arm to allow data to be transmitted back to the computer) – Using a remote control to input the values. • The computer stores the exact sequence of movements as a program in its memory.
  11. 11. Types of end effectors The types of end effectors used in car manufacture are: • Cameras to inspect work • Welding guns to weld parts of the car body together • Grippers to pick up parts and place them somewhere else – grippers often have built-in pressure sensors that tell the computer how hard the robot is gripping a particular object, so that the robot does not drop or break whatever it is carrying. • Vacuum cups to pick up parts without obstructing the sides or bottom, for example windscreens or small complex car parts • Drills to make holes in the car body • Screwdrivers/spanners/riveters to place and tighten screws, nuts, bolts and rivets. • Spray guns to paint the car body • Sanders/polishers/finishers to produce a shiny finish after painting.
  12. 12. Tasks carried out by Robots A robot arm carries out the following tasks on a car production line: • Painting car bodies. • Putting on car wheels. • Drilling the holes in car bodies. • Fixing rivets to car bodies. • Tightening bolts. • Assembling the electric circuits in cars. • Inserting car engines. In order that the robot knows how to do its job, the programmer guides the arm through each step, either by • physically holding the arm (and having sensors attached to their arm to allow data to be transmitted back to the computer). • By using a remote control.
  13. 13. Recent developments in robots Methods are being developed whereby a programmer can program the robotic arm offline, although they still have to refine the instructions by using one of the two methods stated above. • Robots are used rather than human beings because: – A robotic arm has greater accuracy than a human. – The running costs are lower compared with paying a person. – Robotic arms don’t get tired, so work is of a consistent standard. – Easy to re-program, whereas humans need time to make them adept in the new skills. – The whole process can be continuous, without having to stop at shift changeovers.
  14. 14. Medical applications Computer control is used in two major medical applications – intensive care and surgery – but both still require human intervention. • Intensive care Patients in intensive care are monitored through the use of sensors. The sensors feed back a variety of body functions to the computer such as:  Blood pressure  Pulse rate  Body temperature. The use of sensors and computers make the process more accurate and the monitor the health of several patients simultaneously, thus enabling nurses to carry out other tasks.
  15. 15. • Surgery Robotic surgery is an extension of keyhole surgery that involves using robotic arms and cameras inside the patients’ body. The robotic arms and cameras are a lot smaller than normal. The end effector is usually a scalpel. The surgeon wears goggles connected to a computer and is able to see inside a patient. They control the robotic arms and cameras by putting their hands in a console. When they move their hands, the robot arms and cameras respond exactly to the movements they make. The benefits are that the work is more accurate, but the surgeon is in complete control. The procedures replace large- scale, invasive surgery, meaning that patients recover more quickly and do not occupy hospital beds for as long.
  16. 16. Process Control • Definition: Process control is the use of computers or microprocessor to control a process. • Uses of process control: – Oil refining – Chemical processing – Car manufacture – Temperature control – Food and beverage industries.
  17. 17. Types of process control •Used in processes where specific amount of raw materials are combined together and mixed for a certain length of time. •Example – manufacturing of food products such as pre-packed meals. •Generally used to produce relatively small amounts of a product per year. •Refers to processes that appear to be unending. •Example(s) – maintaining temperature in confined surroundings, refining process for petroleum and a paper machine with continuous output of paper onto rolls. •Generally used to produce very large quantities of product per year. •Used when specific items are produced. •Likened to an on/off or stop/start process. •Example – manufacture of cars. •Computer control involved in fitting the wheels, for example, is discrete in so far as a wheel is fitted, then the next car comes along, and the same robot fits a wheel to the car in the same position. In between waiting for cars to arrive the robot stops.
  18. 18. • Most process control is not overseen by a computer as such but by a programmable logic controller (PLC). • PLC is a type of computer or microcomputer that is used for a single purpose. It is able to accept analogue and digital inputs, and a set of logic statements is used to compare the input with a pre-set value. Depending on the result, it activates the output devices. • Often found in industrial processes and is normally programmed to operate a machine or system using just one program. • Rarely any input to it from the user once it has been programmed. • Not really used in systems such as domestic central heating, as here the pre-set temperature might change to suit the conditions. • Used in situations where the pre-set value is a constant such as in a large industrial refrigeration system.
  19. 19. • One system for programming a PLC is a proportional-integral- derivative(PID) algorithm. • These are used with closed-loop systems. A closed-loop system is one in which a physical variable, such as temperature, is being continuously monitored using a sensor connected to the PLC and the outputs from the controller affect the input, i.e. the temperature. • It is a continuous process, the purpose of PLC being to make the input value equal to the pre-set one. • PID is the best way of accomplishing this and is found in many control software. • PID calculates the difference between the input value and the pre-set value. It then causes the PLC to make proportional changes to the output so that the pre-set temperature is eventually reached. • Instead of just switching heater on until the pre-set value is reached the PLC switches it on for a short time and checks the difference again. This process is continued till the required temperature is reached.
  20. 20. EWT (Embedded Web Technology) • Embedded web technology (EWT) is a technology developed by NASA so that experiments in outer space could be conducted by authorized personnel anywhere in the world, providing they had access to a computer and the Internet. • The technology combines the Internet, the worldwide web and real-time systems into one technology for controlling embedded systems. • An embedded system is an integration of microprocessors, input sensors, output actuators and the software needed to control them. They can be build into any real-time control system. • For example, ovens have been developed that allow users to control them remotely. The embedded software enables the user to adjust and control oven temperatures using a mobile phone, PDA, laptop computer – basically, any device that can connect to the worldwide web.