A general introduction to simulation modelling

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A general introduction tosimulation modelling
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Aims and Objectives

• To understand the terms simulation and
  model
• To be able to differentiate between different
  model categories

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Introduction
A dictionary definition of the verb simulate
To mimic
To take the form of something
In this context it is used to mean a form of
deceit
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Computer Simulation

• A powerful tool
• Applied to the design and analysis of complex
  systems
• Decisions can be made about the system by
  constructing computer models of it and conducting
  experiments on the model

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What is the Purpose of Simulation ?
Reasons why it may be preferable to carry out
experiments on a model rather than directly on
the real system

• Results of the experiment may be unpredictable or
  dangerous
• Experiments may unacceptably disrupt the
  operational requirements of the system
• New systems may require design decisions - prior
  to construction

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What is the Purpose of Simulation ?

• A simulation experiment may be precisely repeated
  any number of times
• Confidentiality is easier to maintain with a
  computer simulation
• Time scale of the real system may be too long or
  too short
• evolution of a galaxy
• impact between vehicles
• Training

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Simulation Models
Three categories

• 1. Iconic physical models
• physical models usually at a reduced scale
• e.g. wooden models of cars or an aircraft wing
  for wind tunnel testing
• 2. Abstract models
• mathematical equations
• e.g. equations describing physical laws of nature
  and scientific laws
• 3. Visual models
• graphical representations
• schematic diagrams of electronic equipment

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Simulation Models
A Model

A Description
The form that the model takes is very dependent
on the purpose of the model
The purpose of the model must be discussed and
agreed before the system can be constructed
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Example
A company may be wishing to expand
production e.g. x more toys per week
To do this they will need to purchase one or
more additional machines
Low throughput Low cost
High throughput High Cost
The purpose of the simulation may be to
ascertain the number of machines of each type
that would be needed to achieve target production
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Example - A Flight Simulator
Used to train novice pilots to fly modern jet
aircraft realistically but without the danger to
life that could occur flying a real aircraft.
Flight simulators also allow experienced pilots
to gain experience with unfamiliar aircraft.
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Example - A Flight Simulator
WITHOUT
An exact replica of an aircraft cockpit with all
of the controls and meters
fuselage
wings
engines
passengers !
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Example - A Flight Simulator
Output from pilots controls passed to a computer
Feedback to reflect a real flight
e.g. engine noise, movement of the cockpit to
simulate banking of the aircraft, changing
cockpit meters
Thus the pilot's senses of touch, sight, hearing
and physical orientation receive the same sort
of stimuli that they would receive flying a real
aircraft.
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Example - A Flight Simulator
Benefits

• Immediate access to a specific part of the
  training programme
• to practice landing, the simulator doesn't have
  to take-off first
• Changeover time between students is low
• No need to refuel a flight simulator !
• Fault situations (random or specific) can be
  programmed into a training session

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Level of Realism

• In the flight simulator a high degree of
  correspondence is need between the the simulator
  and a real aircraft
• In other situations such a high level of realism
  is both unnecessary and undesirable
• e.g. the simulation model should contain
  sufficient detail for the system to be understood
  without unnecessary complexity that clouds
  understanding