connor o’leary, micah uzuh, brandon zimmerman, matthew howard advisor: dr. dyer harris
TRANSCRIPT
Connor O’Leary, Micah Uzuh, Brandon Zimmerman, Matthew HowardAdvisor: Dr. Dyer Harris
Laser Tracker Vantage• Dimensional metrology device• Retail Price: Approx. $100,000
In-House Testing• Drop test laser system before
installation• Test identifies unstable opto-
mechanics• Current test has large variability,
poor repeatability
Project Scope• Design a system to allow accurate,
repeatable drop testing of laser subsystem.
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Current Drop Test
3Shim enlarged for clarity. Actual thickness ~0.03 in
4
Current Drop Test Simulation
Questions?
5
Ranked Wants, Metrics, & Target Values
Want/Need Associated Metrics Initial Testing Values
Target Values
Repeatable Shock
Percent Error (%)ANOVA w/Tukey Test
15%p=1.3E-8
5%p> .05
Specified Shock Magnitude
Acceleration (g) 80g 80g
Range of Shock Acceleration Range (g) 60-90g 50-200g
Quick Time to Run 3 Tests (s) 15s ≤ 60s
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Must Have
Want to Have
Constraints: Space on optics bench
Background Science: Shock
Shock is the measurable acceleration of two bodies at impact
Mechanics Involved (1) Energy Equations(2) Linear Motion
Energy EquationAt Impact
Linear Motion Equation
Dire
ction
of
Mo
tion
Drop Height (h)
Top Block
Bottom Block
a=√2 gh∆ t
A simple simulation of Faro’s current set up with shim removed
Shock
Initial Testing– Variability Between Users
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Micah Connor Matt Brandon0
10
20
30
40
50
60
70
80
90
Acce
lera
tion
(g's)
Micah Connor Matt Brandon0
10
20
30
40
50
60
70
80
90
Acce
lera
tion
(g's)
Micah Connor Matt Brandon0
10
20
30
40
50
60
70
80
90
Acce
lera
tion
(g's)
Slow
Fast
Conclusion1) Error between operators2) Error within each operator
Benchmarking
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Dynatup 8200 Drop Tower
– Guiding rods to restrict and aid vertical motion
– Lever system to release weight at certain height
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Concept Generation
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Rubber Pads
• Rubber pads are added to design to aid in the absorption of impacts thus giving more refined and measurable drop heights to corresponding shock values
• Pads used– Viton– Ultra Strength Neoprene– Neoprene Spring– Butyl Rubber
12𝑚𝑣 𝑖
2=𝑚𝑔𝛿+ 𝐸𝐴𝛿2
2𝑑𝑝𝑎𝑑
𝑎𝑔
=−1±√1+ 4h𝐸𝐴𝑚𝑑𝑝𝑎𝑑𝑔
Rubber Pads
Drop Tower Prototype Model
• The model shown (right) is the design as built
• Note the changes mentioned:– Latch (red)– Bottom V-block (black)
Effects• Using purchased V-Blocks
removes capability to handle certain orientations.
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Prototype Cost Summary
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Part Qty $/Part Final Cost
2" x 6" x 12" Aluminum Plate 1 $ 67.02 $ 67.02 1/2" x 5" x 24" Steel Plate 1 $ 23.36 $ 23.36 2” x 4” x 24” Steel Plate 1 $ 117.92 $ 117.92
48" Steel Round Bar, 3/8" D 4 $ 4.20 $ 16.80
3" x 4" legs x 1/4" thick x 12" long 90 Degree Angle Steel 1 $ 13.72 $ 13.72
Linear Ball Bearing for 3/8" Shaft Diameter 4 $ 30.52 $ 122.08
Steel Slide Bolt 1 $ 12.86 $ 12.86
Stainless Steel Spring Loaded Latch 1 $ 44.80 $ 44.80
Various Rubber Pads Package 1 $ 87.03 $ 87.03
TOTAL COST: $ 505.59
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Drop Tower Simulation
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Prototype Testing Procedure
1. Attach accelerometer to laser subsystem2. Each operator performed 5 drop tests with
constant height and material to establish operator error
3. Single operator performed 5 drop tests for each material at various drop heights to evaluate the model
Example:Ultra Strength Neoprene
Neoprene SpringButyl Rubber
Viton
1.5 in (5x)1.0 in (5x)
.
.
.
Initial Testing Revisited – FARO Device
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0
20
40
60
80
100 **
**
Ac
ce
lera
tio
n (
G's
)
*
0
20
40
60
80
100
Ac
ce
lera
tio
n (
G's
)
**
*
Slow Shim Withdrawal Fast Shim Withdrawal
Analysis: One-way ANOVA with Tukey post-hoc * p<0.05( )
Statistical significance between users
Validation Testing – Designed Prototype
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0
100
200
300
400
500A
ccel
erat
ion
(G
's)
Analysis: One-way ANOVA with Tukey post-hoc * p<0.05( )
NO STATISTICAL SIGNIFICANCE BETWEEN USERS
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Material Modeling
5 10 15 20 25 30 35 400
50
100
150
200
250
300
DataModel 2Model 1
Drop height h (mm)
Acce
lera
tion
(g's
)
𝑎𝑔
=−1±√1+ 4h𝐸𝐴𝑚𝑑𝑝𝑎𝑑𝑔
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Curve Fitting
5 10 15 20 25 30 35 400
50
100
150
200
250
300
350
DataPower
Drop height h (mm)
Acce
lera
tion
(g's
)
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Previous Shock Pulse
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Optimized Shock Pulse
-0.000999999999999999 0.001 0.003 0.005-100
-50
0
50
100
150
200
250
Test 1Test 2Test 3
Time (s)
Acce
lera
tion
(G's
)
Wants, Metrics, and Target Values Revisited
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Want/Need Associated Metrics
Initial Testing Values
Target Values Achieved Values
Repeatable Shock
Percent Error (%)
15% 5% 8%
ANOVA w/ Tukey Test
p=1.3E-8 p>.05 p>.19
Specified Shock Magnitude
Acceleration (g) 80g 80g 80g
Range Adjustable Shock
Acceleration Range (g)
60-90g 50-200g 50-800g
Quick Time to Run 3 Tests (s)
15s ≤ 60s 15s
Purchased latch did not perform as expected, weakening prototype performance. Refinement with original designed latch should exceed target value for repeatable shock.
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Path Forward
• Suggestions for the design– Different latch– Thicker Threaded Rod– Modified Positioner Plate*These changes should even further remove variability and improve the percent error to more acceptable values.
• More testing for calibration to tighten up the model.
• Recommend a more stable testing surface to minimize outside vibrations.
Questions?
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