Embodying the Concept Models and Prototypes

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Embodying the Concept(Models and Prototypes)

• BE20-Engineering Design w/ Comp. Apps
• Week 9 10-March-2004

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Todays Journey

• Review course schedule
• Thursday Friday St. Pats Break!
• Next Monday and Friday AutoCAD Exam 1
• AutoCAD help sessions
• Sunday, March 14, 2004 _at_ 700pm RM 105
• Thursday, March 18, 2004 _at_ 700pm RM 105
• Team memo 7 DUE today
• Team memo 8 assigned (Due 17-Mar-2004)
• Embodiment of your design
• Types of models
• Prototypes
• Project specific mathematical models

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Model Types

• Analytical
• Physical Prototypes

Do some physics. What combination of a, q, r,
and dliquid will cause a spill?
(a/g horizontal acceleration / gravity)
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Analytical Models

• Mathematical models of
• Product performance
• Use to predict how well a given concept will
  perform, what to tweak
• Constraints/attributes
• Use to select values of design variables
• Tennis ball server examples
• FOM calculations (your memo due today)
• Initial velocity and launch angle of tennis ball
• Energy storage-Kinetic energy calculations
• Later in slide show will give calculations

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Types of Analytical Models

• Simulation
• Predict how product will perform under certain
  test conditions
• Optimization
• Select values for design variables that optimize
  some performance attribute

Local minimum
Global minimum
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Analytical Example

• Vibration device for persons with disabilities

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Physical Prototypes

• Physical prototype an object or set of objects
  that is fabricated from a variety of materials to
  approximate an aspect(s) of how a product concept
  will perform

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Types of Prototypes

• Proof of concept (POC) models
• Answer specific questions of feasibility about a
  product
• Focus on a specific subsystem or component
• Answers the question Does the imagined physics
  work?

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Types of Prototypes (2)

• Industrial design prototypes
• Demonstrate the look and feel of the product
• Often constructed of simple materials such as
  foam or foam core - not necessarily functional

Concept car
Wheel chair
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Types of Prototypes (3)

• DOE/experimental prototypesNote DOE Design
  of Experiment(s)
• Empirical data is sought to parameterize, lay out
  or shape the product
• Prototypes are constructed from similar
  materials/components as the actual product
• Focus use experiments on a subsystem to develop
  a mathematical model or to converge to a target
  performance
• Your tennis ball server examples
• Proper release of stored energy
• Correlation between predicted motion and actual

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Types of Prototypes (4)

• Alpha prototypes
• Answer questions regarding overall product layout
• Use materials, geometry and layout that team
  believes the final product will take
• Includes all subsystems of the product
• Can also be used for further DOE testing

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Types of Prototypes (5)

• Beta prototypes
• First full-scale functional prototypes
• Constructed from actual materials
• Not necessarily the same manufacturing process
• Vibration device Beta

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Smart Marker Example Balloon CV

• Initial selected concept
• Balloon inflated inside FOX vehicle
• Highly visible
• Simple base design
• Proof of concept to test
• Possibility of field damage
• Balloon deflation

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Proof of Concept (POC) Test
Smart Marker Example

• POC test
• Balloon protected with kevlar fabric covering
• Resulting knowledge
• Fabric too heavy to lift
• Larger balloon required
• Balloon must be inflated after deployment

Pre-deployment
Deployed
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Design Modification and 2nd POC
Smart Marker Example

• Back-up mast system
• Simple counter weight
• Balloon lifts mast into position
• No springs to fail
• No fabric covering (less weight)
• Second POC
• Smaller balloon required
• Higher reliability

Deployed
Pre-deployment
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Balloon Concept Prototypes
Smart Marker Example

• Following the POCs, the marker design continued
  to evolve
• Balloon element was abandoned
• Spring loaded mast was added

Beta prototype
Alpha prototype
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Tripod Concept Prototypes
Smart Marker Example
Alpha Prototype
Beta Prototype
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Smart Marker Prototypes Compared
Smart Marker Example
Concept
Alpha
Beta
Concept
Alpha
Beta
Balloon Concept
Folding Post Concept
Concept
Alpha
Beta
Tripod Concept
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Assignments

• Memo 8 Proof of concept and projectile motion
  calculations
• Identify a critical element of your design and
  construct a proof of concept (physical prototype)
• Set up and carry out projectile calculations (see
  next slides)
• Identify range of angles necessary to hit targets
• Identify initial velocities necessary to hit
  targets
• Sketch your final design
• Sketch rules Neat, clean, label key design
  components, give other explanatory notes
• Provide a cover memo describing your proof of
  concept (what it tests, results of the test,
  lessons learned), projectile motion calculations
  and their implications on your design, and
  description of your final design
• Proof of concept presentations
• Bring your physical POC to class next Wednesday,
  17-Mar-2004
• Give a 2-3 minute talk about key issues of POC
  and results

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Modeling the Tennis Ball Server

• Definition of a Projectile
• A projectile is a fired, thrown, or otherwise
  projected object, such as a bullet, having no
  capacity for self propulsion
• In the absence of a propulsion force, the only
  force acting on an idealized projectile is
  gravity
• Additional forces due to drag, lift and wind
  will also be present and may or may not be
  significant

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Modeling the Tennis Ball Server (2)

• Choice of Projectile
• For typical projectile, neglecting drag, lift and
  wind should work well unless the problem involves
  a low mass, high cross-sectional area projectile
• Consider the drag force on a ping pong ball
  (immediately after launch assuming a launch
  velocity of 9.5 m/s)
• Fd CdrAv2
• Fd (1/2)(1.21 kg/m3)p(.038/2)2(9.5 m/s)2
• 0.062 kgm/s2 0.062 Newton
• Consider the force in light of the mass
  (0.0025 kg 2.5 g) of a ping pong ball
• Using F ma 0.062 N 0.0025a
• a 24.8 m/s2 !! gt 9.81 m/s2

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Basic Projectile Motion Equations
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Projectile Motion Calculations
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Projectile Motion Calculations (2)
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Projectile Example
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Projectile Example (2)
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Projectile Example (3)
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Projectile Example (4)

• Launch velocities vs. launch angles for selected
  target distances

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Work-Energy to Produce Desired V0
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Work-Energy Example
Example Calculation Experimentally determine
spring stiffness, k Also determine deflection
needed to strike an 8m target with a 2 oz
projectile. Neglect friction and kinetic energy
imparted to mechanism.
(1) Spring Stiffness Spring from hardware
store 11 lbs compresses spring 11/16 inch
0.688 inch. Therefore, ksp 11 lb/.688 in 16
lb/in 192 lb/ft 2.83 kN/m (Used 4.45 N/lb
0.3048 m/ft) (2) From previous chart (v0
9.2 m/s, ? 56?) to strike 8 m target (3) Unit
Conversions (a) Convert 2 oz to lb 2 oz
(lb/16 oz) 0.125 lb (b) Mass 0.125
lb/32.2 fps2 mass in slugs (c) Velocity
9.2 m/s (ft/0.3048 m) 30.2 fps
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Work-Energy Example (2)
(4) Write work-energy equation T1 ?U1-2
T2 1/2 k d2 - m g(d sin ?) 1/2 m
v2 1/2 (192 lb/ft)?d2 - (0.125 lb)(sin 56?)?d -
1/2 (0.125/32.2 slug)(30.2 fps)2 0 This is a
quadratic equation in d 96?d2 - 0.1036?d -
1.77 0, of the form a?d2 b?d c
0 Use the quadratic equation yields roots d
0.1363 ft, - .1352 ft (discard) (5) Result
You must compress the launcher spring 0.136 ft
1.64 inches in order to propel a 2 oz projectile
out of your launcher with a velocity of 9.2 m/s
(30.2 fps). This is for a spring with ksp 16
lb/in 192 lb/ft.
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Work-Energy Example (3)
(5) Result You must compress the launcher
spring 0.136 ft 1.64 inches in order to propel
a 2 oz projectile out of your launcher with a
velocity of 9.2 m/s (30.2 fps). This is for a
spring with ksp 16 lb/in 192 lb/ft. (6)
Caution This is only a ballpark figure because
we neglected friction and kinetic energy of the
launch mechanism. But this should give you an
idea of how to select a spring or whatever for
your launcher. (7) Velocity Precision Of even
more importance, lets say you want to hit a 8.5
m target. At same launch angle (56?) the
required velocity is 9.48 m/s (31.1 fps). The
calculation yields a spring deflection of 1.69
inonly .05 inches more than needed for the
first example. Note This kind of precision is
difficult to achieve.
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Summary

• For modeling purposes
• Find range of velocities and angles necessary to
  get tennis ball to the targets
• Next, depending on your chosen design, determine
  how you will supply the necessary initial
  velocity
• Consider drag effects as well