SIMULATION
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Chapter 3.7
VCN 9691 Computing Notes
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REAL-TIME PROCESSING
REAL –TIME SYSTEMS
A real-time system is one that can react quickly
enough to data input to affect the real world.
 The system should process and output data
without a significant delay.
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APPLICATION OF REAL-TIME
SYSTEMS
The real-time systems are needed in situations
where there is a need to make a decision quickly.
 For example
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A nuclear reactor may start to react too violently.
The sensors will pick up the readings and send input
to the controlling program.
The control program takes the decision to insert
graphite rods to slow the reaction down.
The readings from the sensors (input) must be processed
immediately. This is a real-time processing system. It is
not important how quick the output (insertion of
graphite rods) should be. The decision making time is
important.
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APPLICATION OF REAL –TIME SYSTEMS
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APPLICATION OF REAL-TIME SYSTEMS
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Real time systems can be used in:
 temperature control systems
 security alarm systems
 Biometric objects
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ADVANTAGES OF REAL-TIME
SYSTEMS
The system will make decision immediately
which can be vital in making critical decisions.
 Real-time systems can eliminate the need of
human supervision in certain situations.
 Real-time systems can help save human lives,
equipment and environment catastrophes by
providing timely feedback.
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DISADVANTAGES OF REAL-TIME
SYSTEMS
Real-time systems are almost always dedicated
systems and can not do anything else in order to
keep the decision time short.
 Real-time systems need expensive hardware and
software in order to provide the best response
time.
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THE FEEDBACK LOOP; INPUT & OUTPUT;
SENSORS & ACTUATORS
A sensor is a device that measures physical
quantities such as length, time, temperature,
light, flow, pressure, etc
 Sensors can be analogue or digital.
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For analogue sensors the computer will require
the signals to be passed through an
analogue/digital converter (ADC) because the
computers can only use digital signals as input.
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SENSORS ARE FOR INPUT
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ACTUATORS
An actuator is the device that can accept a signal
from the computer and turn it into a physical
movement.
 Actuators are commonly used in devices that are
needed to be controlled by a computer system.
 Example:
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Turning a robot in a different direction.
 Opening and closing an automatic door.
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ROBOTS
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THE USE OF ROBOTS
A robot is a mechanical device which is under the
control of a processor.
 Robots are used because:- (advantages)
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VCN 9691 Computing Notes
A single robot can do work that can equally be done
by, say, 100 employees, thus helping cut costs on
salary.
 A robot is consistent and does not get tired, as
opposed to humans
 Robots can be used to do work in places that are
hazardous to humans, e.g. inside of a nuclear reactor
 In places where the environment does not have
essential components for humans like air, light etc,
robots can be used. E.g. on mars exploration.
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THE USE OF ROBOTS
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Disadvantages
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Robots are expensive to buy.
Robots may not be able to adapt to unexpected
situations, because they are preprogrammed.
The use of robots has created unemployment to a
certain level
There is a need, to employ expert technicians to
service the machines, programmers to program every
task that they need to undertake.
Robots break down due to extensive use and require
periodic maintenance.
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THE USE OF SIMULATIONS
Simulation is the use of a computer program to
predict the likely behavior of a real-life system.
 Simulations involve constructing mathematical
models of a system and testing them, usually
under controlled conditions.
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By changing different variables in the model, many
different situations can be tested and experienced.
 Interactive simulations allow the user to ‘interact’
with the simulation by accepting live input and
responding to it in real-time.
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REASONS FOR SIMULATION
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Simulation can help to speed up a process in
order to give results in a more reasonable time
scale.
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For example simulating a car’s reaction to imminent
crash without necessarily crashing a car.
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Simulation can be used to predict the results of
actions, or model situations, that would be
otherwise too dangerous.
For example, simulating the growth of a crop which
could otherwise take months to grow
They can be used to create virtual reality
worlds where impossible things seem possible,
e.g flying through the rings of planet saturn
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REASONS FOR SIMULATION
Production of a test prototype would be very
expensive
 -Time taken to produce and test a prototype may
be too long/immediate need
 Need to test in circumstances unable to be
reproduced
 May be too dangerous to test in reality
 Situations can be reproduced which may never
arise in ordinary testing
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EXAMPLE QUESTIONS
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1. Describe the real time application of a
computer used to control a burglar alarm system.
(4)
2. Explain why some applications require parallel
architecture to carry out their processing and
describe what is meant by parallel processing.
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