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.

2

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

6

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

8

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

9

Dynatup 8200 Drop Tower

– Guiding rods to restrict and aid vertical motion

– Lever system to release weight at certain height

10

Concept Generation

11

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.

12

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

16

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

17

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

18

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

19

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

)

20

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

22

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.

23

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?

24