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Introductory unit on systems

Introductory unit on systems

Published in: Technology, Business

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  • 1. Systems Approach Universal System
    • We use a systems diagram to analyse technology.
    • All systems can be analysed and simplified in terms of their inputs , process and outputs
    • The UNIVERSAL SYSTEMS DIAGRAM consists of these three basic elements.
    • This process is known as the “BLACK BOX” approach to technology
  • 2. Systems Diagrams
    • To analyse a system more fully, we can list the inputs and outputs from the system.
    • As an example, consider an electric kettle,
    OUTPUTS: KETTLE Water and Electricity Hot water, Noise and Steam Water and Electricity. Hot water, noise, steam. INPUTS:
  • 3. Pupil Problems Here are some problems for you to try,
    • Battery powered torch
    Torch Chemical energy Light energy Heat energy
    • Vacuum cleaner
    Vacuum Electrical energy Dirt Noise, Heat, Clean carpets
  • 4. Pupil Problems
    • Washing machine
    Washing M/C Water, Dirty clothes, Electrical energy Hot water, Noise, Steam, Clean clothes
    • Television
    TV Electrical energy, Digital signal Picture, Sound, Heat
  • 5. Sub-Systems Sometimes it is necessary to break the PROCESS down into smaller pieces.
    • To enable this we consider the system’s
    Example: A battery powered torch Switch Bulb Chemical energy Light and Heat energy System Boundary
  • 6. Pupil Problems 1) A microwave oven Timer Magnetron Electrical energy Heat, Light, Hot food On/Off Turntable Food 1 st Inputs 2 nd Subsystems 3 rd Boundary 4 th Flow of information arrows 5 th outputs Set time
  • 7. Pupil Problems 2) Washing machine Heater Motor Electrical energy Clean Clothes Control Dirty clothes Pump Drum Water Hot water,etc. Set Cycle
  • 8. Control Systems
    • All types of system need some form of control to operate
    • There are 2 main types of control,
    • In an OPEN LOOP system the input causes the output
    • The output operates independently of the input
    • Open loop system are cheap but not very accurate
    Light switch Bulb Action Light
  • 9. Control Systems
    • In a CLOSED LOOP system, the output is compared with a reference value
    • Closed loop systems are more accurate, but also more expensive
    • The self monitoring action of closed loop is achieved through a FEEDBACK loop
    On/Off Motor Fan Heater Thermostat Set temp Elect Heat
  • 10. Control Systems Tap Handle Valve Water level Water Person Flood Manual Open Loop
  • 11. Control Systems Tap Handle Valve Water level Water Eyes / Brain Hand Correct level Manual Closed Loop
  • 12. Control Systems Automatic Closed Loop Start Switch Valve Water level Water Level Sensor Control Unit Correct level Press
  • 13. Pupil Problems
    • State three examples of manual open-loop control. Draw a system diagram for each one and show the system boundary.
    • State three examples of manual closed-loop control. Draw a system diagram and show the system boundary.
    • State three examples of automatic closed-loop control. Draw a system diagram and show the system boundary.
  • 14. Control Diagrams Example: Temperature control in a gas oven We could draw a systems diagram for the gas oven, but it is sometimes necessary to draw a more accurate control diagram Temperature sensor Oven Burner Gas Valve - + Set value Correct temperature Actual value
  • 15. Error Detector Symbol - + Set value Actual value Error How the error detector works: If SET VALUE (+) is bigger than the ACTUAL VALUE (-) the ERROR SIGNAL is ON (Raising the oven temperature) If the SET VALUE (+) is less than the ACTUAL VALUE (-) the ERROR SIGNAL is OFF (Cooling the oven temperature)
  • 16. Pupil Problems
    • Explain the following terms when applied to control systems:
    • Open loop
    • Closed loop
    • Negative feedback
    • Positive feedback
    • Error detector
  • 17. Pupil Problems
        • Draw a control diagram showing the manual closed-loop control system for a cyclist steering a bicycle.
        • Draw a control diagram showing the automatic closed-loop control system for the cruise-control in a car.