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What is a control system?

It uses microprocessors to control physical conditions. This is done by :

1. Keeping them the same over a period of time 2. Vary them according to the preset values + lengths

of time.

Physical conditions can include: Temperature Pressure Humidity Light Moisture.

Process Control

Medical Applications

Central-heating systems

Car Manufacture

Air-conditioning systems

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Refrigeration

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Air-Conditioning Systems

How does an Air-Conditioning System work?

Keep in mind that the ‘gas’ that is being used is called refrigerant. There is a reason why refrigerant is used and that reason is that it has the ability to be easily converted to a gas and back to a liquid again.

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How does an Air-conditioning System work?

The room cools down

As liquid changes to gas, it absorbs heat from the inside of the building.

Fan blows air across metal fins (which have chilled as a result of heat being absorbed)

Liquid flows through the expansion valve

It evaporates into a cool low-pressure gasGas moves through the condenser outside the building

Gas cools down into a liquid

Compressor

Cool low-pressure gas into hot high-pressure gas

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Refrigeration

• The principle of how refrigeration works is the same as that of the Air conditioning system.

• Main inputs are:1. Temperature sensor: Monitors the

temperature inside the refrigerator2. Contact switch/ pressure sensor: for the door3. Number pad: input required temperature

So what happens now?

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Refrigeration

The microprocessor compares the data from the sensor to the preset values. Then?

If the temperature is higher than the preset value, the microprocessor will activate an actuator which will then turn on the compressor.

If the temperature is lower than the preset values, the microprocessor will turn the switch to the compressor off.

Are there any other outputs from the fridge?

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Refrigeration

1. Light –emitting diodes (LED): this allows the user to know what the current temperature is inside fridge.

2. Warning Buzzer: this sounds when the door is left open, in order to alert someone to close it.

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Central Heating Systems

What are the main parts of a central heating system?

1. Boiler2. Hot-water cylinder3. A pump4. Radiator

So how does it all work?

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Central Heating Systems

Boiler used to heat the water

Water from the boiler flows into

hot-water cylinder

Pump causes heated water

from the cylinder to flow round the

system to the radiators

What happens in a micro-processed controlled central-heating system?

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Central Heating System

• An ADC (Analogue to Digital Converter) is used.

• The microprocessor controls separate actuators:

1. Opens the valves2. Switches the pump

on

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Car Manufacture

• The robots used in the manufacture of cars use actuators in the form of electric motors.

• A DC motor spins quickly when an electric current is applied to it. It spins the opposite way when the current flowing through it is reversed.

What is a stepper motor? More popular type of motor for robotics. As the name suggests; it does its actions in

steps. This is then easier for a computer to control.

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What do they use in industries and why?∞ They use robot arms∞ It consists of seven metallic sections with six

joints.∞ Each joint is controlled by a separate stepper

motor.How does the computer control the movement

of the arm?It uses different ‘end effectors’. This allows for a

variety of jobs to be done. The ‘end effectors’ are attached at the end of a robot arm.

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What types of end effectors are used in car manufacture?

1. Cameras in order to inspect work2. Welding guns3. Grippers which allow for parts to be picked up

easily. They have built-in pressure sensors.4. Vacuum cups i.e. electrical parts5. Drills6. Screwdrivers7. Spray guns8. Sanders

NOTE: the end effector can have any of the mentioned attachments BUT if the end effector is changed you also need to change the programming.

For example: you can’t have the robot that was spray painting then to be used as a screwdriver head without changing the programming.

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What are industrial robots?

• Their purpose is to perform the same task again and again.

What does a robot do on a car production line?1. Painting car bodies2. Putting on car wheels3. Drilling holes in car bodies4. Fixing rivets to car bodies5. Tightening the bolts6. Assembling electric circuits in cars7. Inserting car engines.

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How does a robot know what to do?

• Initially the programmer guides the arm step by step. This is usually done be actually physically holding the arm.

• These arms contain sensors which allow them to transmit data back to the computer.

• The computer then stores the exact order of movements as a program in its memory.

• You could also move the robotic arm by using a remote control.

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Why are robots used rather than humans?

• A robot arm is much more accurate than a human

• The running costs are comparatively lower• Robotic arms do not get tired• Robots can be used continuously

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Medical Applications

There are two major medical applications of ICT:

1- Intensive care2- Surgery

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Intensive Care

The patient is monitored by sensors. These sensors measure:

1. Blood pressure2. Pulse rate3. Body temperature

The computer it pre-set with values. So the sensors take in the above mentioned variables and compare them to the pre-set values, if the

measured value is outside the pre-set value range, an alarm is set off by the computer.

The computer allows the doctor to monitor several patients at the same time.

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Surgery• It involves robotic arms + cameras inside the

patient’s body.• These robot arms and cameras are much

smaller than normal. • Usually the end effector is a scalpel.• The surgeon wears a type of goggles which

allow him to see inside the patients body. The surgeon then controls their hand by putting their hands into a console. Their hand movement is then imitated by the robotic arms.

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What are the benefits of robots in surgery?

• The work is done more accurately• The patients recover more quickly because

large scale operations are not necessary.• The patient does not occupy the hospital bed

for long.

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Process Control

• This is when computers/microprocessors are used to control a process.

Few examples:× Oil refining× Chemical processing× Car manufacture× Temperature control

Types of Process Control

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1. Batch Control Process

2. Continuous Process Control

3. Discrete Process Control

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Batch Control Process

• This is used when a specific amount of raw materials are combined together + mixed for a certain length of time

For example:- In pre-packed meals: the amount of each

ingredient that is added is controlled by a computer. The length of time it cooks for and the temperature is also computer controlled.

- It is used to produce relatively small amounts of product per year.

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Continuous Process Control

• This is a process that never appears to end.For example:Maintaining the temperature of a confined

environment.Paper machines with continuous paper output

onto rolls.

It is used to produce very large quantities of product per year.

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Discrete Process Control

• This is only used when a specific item is produced. It is like an on/off process.

For example:Manufacturing of cars; computer control used

when fitting the wheel.The wheel is fitted, next car comes and the

same robot fits the wheel in the same position.

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What are most process controls overseen by?

• By a Programmable Logic Controller (PLC)• It is the type of computer that is only used for

one purpose.• It can accept both analogue and digital Inputs.• Then a set of logic statements are used to

compare the input with the input pre-set value. Dependent on the result the output device is activated.

• It is usually found in industrial processes.• Once it has been programmed; there is no

further input from the user.

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How can you program a PLC?

• By using a Proportional-Integral-Derivative (PID) algorithm.

• They are used with closed-loop systems.What is a close-loop system?• It is a system in which a physical variable is

continuously being monitored.• The purpose of the PLC is to make the input

value equal to the pre-set one.• PID is the BEST way to do this. It is found in

many versions of control systems. For example washing machines.

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What does PID do?

• It calculates the difference between the input value and the pre-set value.

• It then causes the PLC to make the appropriate changes to the output so that the pre-set value is eventually reached.

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EWT: Embedded Web Technology

• This technology combines the Internet, the worldwide web and the real time systems into one technology for controlling embedded systems.

What is an embedded system?It is an integration of microprocessors, input

sensors, output actuators and the software needed to control them.

The embedded software enables the user to adjust and control oven temperatures using a mobile phone or PDA or laptop computer.