1. Learning Objectives Today we will Learn:
What is meant by a Control System
Examples of Control systems
How control systems work

2. Control systems
A control system is any device that has a processor or microchip embedded within the equipment.

3. Control systems
A control system manages the behaviour of a device. Examples:

4. Control systems At home Washing machines Dishwashers
Burglar Alarm system

5. Control systems Outside the home Car park barriers Lifts
Computer controlled lighting systems at discos and concerts

6. Control systems At work Air conditioning systems Lifts Automatic doors
Factory robots

7. Parts of a control system
Dial
Touch screen
Sensors
Microprocessor
Actuator (a device that sends a signal to activate an output device)

8. Pre-set Values
STEP 1: The microprocessor stores a pre-set value input by the user via a touch screen, dial or knob

9. Sensors Sensors play a major part in control systems
STEP 2: Sensors collect data from the environment
An example might be a Temperature sensor that measures the temperature in a room

10. Sensors
STEP 3: Once sensors have taken a reading or measurement, they send that reading straight back to the micro-processor

11. Sensors
But the micro-processor cannot understand the signal sent from the sensor
WHY??

12. Sensors
STEP 4: Sensors send measured data (in analogue format) to a convertor.
STEP 5: ADC (Analogue to Digital Convertor) converts data from analogue to digital.
STEP 6: Convertor sends the digital data to the Microprocessor.

13. Processing
STEP 7: Once the input data from the sensors has been received by the computer, the micro-processor can compare it with the pre-set value and decide what it needs to do. For example switch something on or off.

14. Output
STEP 8: Once the processing has taken place and a decision has been made, the computer will send the correct signal to the actuator or output device.
For a central heating system, this might be to turn the heating on or off. For a greenhouse watering system this might be to turn the sprinklers on or off.

15. Learning Objectives Today we will Learn:
What is meant by process control
The differences between batch, discrete and continuous process control

16. Discrete vs Continuous Process Control
Discrete Process control is used when specific items are produced. It is an on/off or start/stop process, for example fitting the wheels on cars by robots. Robots stops and when the next car comes the process is repeated.

17. Discrete vs Continuous Process Control
Continuous process control is used in processes which appear to be unending. For example, maintaining the temperature in a room

18. Discrete vs Continuous Process Control
3. Batch process control
Used in processes where specific amounts of raw materials are combined together and mixed for a certain length of time. E.g. food manufacturing
The amount of each ingredient added is controlled by the computer, length of time for each stage and the temperature.

19. PLC
A programmable logic controller is a digital computer that accepts analogue and digital inputs and compares inputs with the pre-set values.
Depending on the results, it activates the output devices.
A PLC is used only for a single purpose such as operating a machine.

20. PID Controller A PID is used for programming a PLC
A proportional–integral–derivative controller
A PID is used for programming a PLC
It does the comparison and calculates the difference between the input value and the pre-set value and makes the PLC to activate an output.

21. PID Controller
A proportional–integral–derivative controller
“we want the heating and cooling process in our house to achieve a steady temperature of as close to 22°C as possible”
The Setpoint (SP) is the value that we want the process to be. The PID controller looks at the setpoint and compares it with the actual value of the Process Variable (PV).
The PID controller in our Heating and Cooling system looks at the value of the temperature sensor in the room and sees how close it is to 22°C.

22. PID Controller
If the SP and the PV are the same – then the controller doesn’t have to do anything, it will set its output to zero.
However, if there is a disparity between the SP and the PV then the action will either be cooling or heating depending on whether the PV is higher or lower than the SP

23. PID Controller
Let’s imagine the temperature PV in our house is higher than the SP. It is too hot. The air-con is switched on and the temperature drops.
The sensor picks up the lower temperature, feeds that back to the controller, the controller sees that the “temperature error” is not as great because the PV (temperature) has dropped and the air con is turned down a little.
This process is repeated until the house has cooled down to 22°C and there is no error.

24. Air Conditioning System
Touch screen is used to input the required temperature
Temperature sensor collects data about the room temperature
The temperature sensor sends data to the analogue to digital convertor
The convertor converts the analogue data into digital format
The convertor sends the data to the micro-processor
The microprocessor compares the temperature of the room to the preset value
If temperature of the room is above the pre-set value the fans remain on/are switched on by the microprocessor or microprocessor increases their speed
If temperature of the room is below the pre-set value the fans remain/switched off by the microprocessor

25. Central Heating System
A number pad is used to input the required temperature.
Temperature sensor monitors temperature of room
Data from the sensors is converted to digital (using an ADC)
The convertor sends the digital signal to the micro-processor
Microprocessor compares temperature data from the sensor with the pre-set value
If the temperature is higher/lower than preset value a signal is sent to the actuator
if lower microprocessor/actuator switches the heater on
if higher microprocessor/actuator switches the heater off

26. Refrigeration A knob allows users to set the desired temperature
Temperature sensor monitors temperature of the fridge
The temperature sensor sends data to the analogue to digital convertor
The convertor converts the analogue data into digital format
The convertor sends the data to the micro-processor
Microprocessor compares temperature data from the sensor with the pre-set value
If the temperature is higher/lower than preset value a signal is sent to the actuator
if lower microprocessor/actuator switches the cooler on
if higher microprocessor/actuator switches the cooler off

27. Intensive Care
Sensors monitor the patients heart rate, pulse rate, body temperature, blood pressure
The computer is pre-set with normal range of values which is compared with the ones fed back by the sensors
CONVERSION
3. Microprocessor compares the data from the sensors with the pre-set values
4. If the data received is higher/lower than the pre-set value then the computer sounds an alarm

28. Process Control
Process control is the use of microprocessors or computers to control a process. It is used in:
Chemical processing
Car manufacture
Temperature control
Food and drink industries

29. Computer Controlled ROBOTS in car manufacturing

30. Computer Controlled ROBOTS in car manufacturing
A robot arm consists of 7 metallic sections with six joints, each joint being controlled by a separate stepper.

31. Computer Controlled ROBOTS in car manufacturing
Robots can perform the following jobs on a car production line:
Painting car bodies
Putting on car wheels
Drilling the holes in car bodies
Tightening bolts
Assembling the electric circuits
Inserting car engines

32. Computer Controlled ROBOTS in car manufacturing
Advantages of using robots:
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
The whole process can be continuous , without having to stop at shift change overs

33. ROBOTS 1)What are robots?
2) Give examples of areas in which robots are used
3) Give examples of robots
4) Advantages and disadvantages of using robots
5) Ethical issues related to robots
6) Components that make robots

34. Advantages of Computer Control
Can operate 24 hours a day without taking a break.
Can work without holidays or sick days
Will work without any wages.
Will accurately repeat actions over and over again
Can process data from sensors very quickly
Can take account of hundreds of inputs at the same time
Can make reliable and accurate decisions
Can be used in dangerous or awkward environments

35. Disadvantages of Computer Control
The software for the control system is specialist and may cost a lot of money to develop
If the computer malfunctions the system will not work
If there is a power cut the system will not work
The computer cannot react to unexpected events as perhaps a person could. It can only respond in the way it has been programmed.

36. Robots

37. Robots

38. Robots

39. Robots