WJEC ICT – Unit 3

Evaluating Control Systems

Where found? - Recap• At home• Washing machines• Microwave cookers• Dishwashers• Electric kettles• Fridges• Video recorders• Remote control television• Central heating systems• Burglar Alarm system• External Security lights

At workAir conditioning systemsLiftsAutomatic doorsFactory robots

Outside the homeTraffic light systemsCar park barriersCars – engine management systemsLiftsRides at theme parksComputer controlled lighting systems at discos and concertsRemote controlled car

What I need to learn

• Refresh our knowledge of Control Systems.

• Understand the feedback loop system in control in context of different scenarios.

• Know the advantages and disadvantages of computer control and data logging.

The TWO Important Terms

• Data Logging: Using ICT to record or capture measurements or readings (e.g. temperature, wind direction, speed etc.).

• Control: Using ICT to control devices (e.g. traffic lights, automatic doors etc.).

Sensors Recap

Review: Data LoggingBenefits of Computerised Data Logging Drawbacks of Computerised Data

LoggingMore accurate readings Initial cost of logging equipment

Can read in intervals Logging too much may take up too much storage

Can keep going 24/7 Reliance upon equipment

Doesn’t make mistakes

Data can be analysed

Can be used in hazardous situations

Control: Feedback System: IPO• E.g. Central Heating You have set your

thermostat to 23 degrees.

• INPUT: The heat sensor would read the temperature of your home.

• PROCESS: Would check the recorded temperature against the temperature you have set (23 degrees).

• IF IT IS <23 THEN the OUTPUT would be a signal to switch the heating on.

• IF IT IS >=23 THEN the OUTPUT would be a signal to switch the heating off.

• IF the heating is switched on, the system would keep checking the temperature, by getting FEEDBACK. Once it reaches 23, the heating would then switch off.

Control: Good Vs. BadAdvantages of Control Disadvantages of Control

•Can operate 24 hours

•Can work without holidays or sick days

•Will work without any wages.

•Will repeat actions over and over

•Can process data from sensors very quickly

•Reliable and accurate

•Can be used in dangerous environments

• Expensive software costs

• Computer dependence

• Issues if power cut?

•The computer can’t react to unexpected events like a human could

•It can cause some concern if total control for a system and the decisions are handed over to a computer.

EXPERT Systems

What are they?

• Simply put it is “A system that takes the place of a human expert”

• A Database that can be searched and deductions made on the basis of the results

• An EXPERT system simulates the knowledge and skill of an expert

How does it work

• It has a large database of knowledge which can be interrogated

• It has an inference engine which allows the computer to make deductions based on the facts that have been input and the data in the database

Where is it used?Other Specific Uses• Medical Expert Systems:• Mycin - This expert system was

designed to identify bacteria causing severe infections, such as bacteria and meningitis, and to recommend antibiotics

• Medical screening for cancer and brain tumours

• Matching people to jobs Diagnosing faults in car engines,

• Legal advisory systems• Training on oil rigs• Mineral prospecting• Oil exploration

Advantages• The computer can store far more information than a human. It can draw

on a wide variety of sources such as stored knowledge from books case studies to help in diagnosis and advice• The computer does not 'forget' or make mistakes• Data can be kept up-to-date• The expert system is always available 24 hours a day and will never 'retire'• The system can be used at a distance over a network / rural areas or even poorer third world countries have access to experts• Provides accurate predictions with probabilities of all possible problems with more accurate advice• Some people prefer the privacy of talking to a computer• Gives the security of a second opinion

Disadvantages • Over reliance upon software• Initial expensive development costs• Some employees could be de-skilled by over dependence upon computer advice• Fewer staff could be needed• Lacks the 'human touch' – lack of personal contact/empathy/ No human available if do not know what to do• Lacks human senses e.g. see a rash, hear a cough, smell a wound in medical examples• GIGO/ dependent upon the correct information being given. If data

or rules wrong the wrong advice could be given / not 100% accurate/ lack of common sense.

Robotics

A robot is machine that can be programmed to perform a sequence of eventsMany robots are used in industry to do the following types of jobs:• Repetitive and boring jobs• Dangerous jobs• Heavy lifting

Specific Uses

• Car production• Spot welding• Assembling parts e.g. fitting windscreens• Paint spraying• Testing engine timing and emissions using sensors• Carrying parts around the factory• Telebots e.g. Deep sea exploration, Bomb disposal, • Bionics e.g. robotic legs and arms controlled by the human

brain• Space probes• Domestic robots such as vacuum cleaners, disability robots

Advantages

• Repetitive tedious jobs are done to the same consistent standard

• Can work 24 hours a day 365 days a year• Can work in dangerous places• Can work in unhealthy places• Can be quickly taught new skills by changing the program

or a human taking them through the motions of a new skill• Do not need to have a heated or lit environment saving on

utility costs• Saves on employment costs

Disadvantages

• Initial expensive development costs• Unemployment due to many assembly line jobs now being done

by robots / loss of human jobs• Possible need for extra space / new technology to accommodate robots• Cost of maintenance/running costs• Staff training to set up or use robots• Limited functionality• Lack of common sense. Robots do not react quickly to situations

they have not been programmed to deal with.