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Systems Realization Laboratory Modeling and Simulation in Engineering Chris Paredis G.W. Woodruff School of Mechanical Engineering Georgia Institute of Technology
Systems Realization Laboratory
Modeling and Simulationin Engineering
Chris Paredis
G.W. Woodruff School of Mechanical EngineeringGeorgia Institute of Technology
Systems Realization Laboratory
Lecture Overview
Objective:• Define what a model is• Illustrate why models are important in engineering
Topics:• What is a model?• What are some properties of models?• How does one create a new model?• How are models used in engineering?
Systems Realization Laboratory
What is a Model?
Examples of Models…
What do these examples have in common?
Systems Realization Laboratory
Examples of Models in Vehicle Design
Computational Fluid DynamicsNoise, Vibration,and Harshness
Crash TestingThermalStress Analysis
Systems Realization Laboratory
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
All models are 'wrong'.Some are useful.
Attributed to George Box
Who has created a new model today?
Systems Realization Laboratory
How Do We Create Models?
1. Gather data about real system2. Postulate hypotheses about the relationships in the
data3. Formalize these hypotheses in models4. Validate models by performing simulations5. If necessary, modify the hypotheses and models until
valid
(Adapted from F. Cellier)
Systems Realization Laboratory
A Quick Aside:When is a Model Valid?
Is this model valid?f(x)
x
Models can never be proven correct –
only falsified.(Adapted from Karl Popper)
Systems Realization Laboratory
Unanticipated Phenomena May Invalidate Model
Tacoma Narrows Bridge,Nov 7, 1940.
Systems Realization Laboratory
Simulator
SystemModel
Simulator
SystemModel
Simulator
SystemModel
Simulator
SystemModel
Why are Models Important in Engineering?
DecisionSolver
SatisficingSolution
InitialGuess
Evaluation ofDesign Alternative
DesignAlternative
Predict theOutcome of
Engineering Design Decisions
Systems Realization Laboratory
When are Models 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)
Systems Realization Laboratory
Examples of Models in Engineering
Computational Fluid DynamicsNoise, Vibration,and Harshness
Crash TestingThermalStress Analysis
Systems Realization Laboratory
Manufacturing Simulation
DFM – DFA – DFX
Take life cycle cost into account at the design stage
Systems Realization Laboratory
Training Simulators
Use the previously developed simulation models for training
Train operators before prototypes are built
Test whether user interface is user-friendly
Systems Realization Laboratory
Immersive Environments
Allow user to interact with models through• 3-dimensional vision• Touch (tactile interface)
Complete virtual prototype
Systems Realization Laboratory
If a picture is worth 1000 words,how about a simulation?
Summary We all create and use
models all the time Models should be validated In engineering, models are
used for predicting the outcome of decisions, but also for training or documentation.
In this class you will use models to solve engineering problems
Crash Testing
