Lecture 1: Modeling and Simulation in Engineering

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Lecture 1 Modeling and Simulation in Engineering

• Chris Paredis
• G.W. Woodruff School of Mechanical Engineering
• Georgia Institute of Technology

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Lecture Overview

• Objective
• Create a framework for the rest of this course
• Frame numerical methods in the context of
  engineering design
• Topics
• The engineering design process
• The importance of modeling in design
• The importance of numerical methods in creating
  and solving models
• The use of Matlab in numerical methods

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Setting the Context
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What is a Model?

• Examples of types of Models

• Physical (scale) models
• Mental models
• Mathematical models

What do these examples have in common?

• They are abstractions they approximate reality
  to some extent
• They are surrogates for some other system
• Although they are abstractions, they can convey
  some important insight into the physical system
  they are modeling

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Examples of Models in Vehicle Design
Computational Fluid Dynamics
Stress Analysis
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What is a Model?

• Definition (based on Marvin Minsky's definition)
  
• A model (M) for a system (S) and an experiment
  (E) is anything to which E can be applied in
  order to answer questions about S
• A model is an abstraction of reality

Who has create a new model today?
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How Does Modeling Relate to Knowledge?
A Model is Knowledge!

• "Modeling means the process of organizing
  knowledge about a given system" (Bernard Zeigler)
• Models allow us to
• Predict
• Infer new information

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A Quick AsideWhen is a Model Valid?

• Is this model valid?

f(x)
x
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Unanticipated Phenomena May Invalidate Model
Tacoma Narrows Bridge, Nov 7, 1940.
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Overview of Presentation

• What is a Model?
• Creating Models Scientific Research
• Some Model Characteristics
• Using Models in Engineering

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Using Models Simulation?

• Definition of Simulation
• A simulation is an experiment performed on a
  model
• (Korn and Wait)
• Simulation requires
• A model description
• An experiment description
• Most often, simulation refers to mathematical
  models evaluated (exercised) on a computer

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Why is Simulation Important in Engineering?
Satisficing Solution
Initial Guess
Decision Solver
Predict theOutcome of Engineering Design
Decisions
DesignAlternative
Evaluation ofDesign Alternative
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When is Simulation most useful?

• When the system is not available
• When the physical experiments cannot be performed
• When the cost of experimentation is too high
• When the time scale of the system is not
  compatible with those of the experimenter
• Under controlled circumstance (e.g. no
  disturbances)

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Examples of Models in Vehicle Design
Computational Fluid Dynamics
Stress Analysis
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Manufacturing Simulation

• DFM DFA DFX
• Take life cycle cost into account at the design
  stage

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Training Simulators

• Use the previously developed simulation models
  for training
• Train operators before prototypes are built
• Test whether user interface is user-friendly

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Immersive Environments

• Allow user to interact with models through
• 3-dimensional vision
• Touch (tactile interface)
• Complete virtual prototype

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If a picture is worth 1000 words,how about a
simulation?

• Summary
• We all create and use models all the time
• In science, models are formalized and validated
• In engineering, models are used for evaluation,
  training, documentation.