Computer Automation of a
Tribometer
Michael Eng, TJHSST
With Nimel Theodore, Kathy Wahl
NRL Code 6176
Objective
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Main goal- integrate positional data w/
friction collection
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Using LabVIEW program
Can be applied to microscopic or
spectroscopic analysis of frictional events
http://www.rpi.edu/dept/materials/COURSES/NANO/oja/nanocrys.gif
Outline
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Reciprocating stage
Tribometer
Circuit board
Program structure
Sample output
Applications
Stage and Controller
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Aerotech ALS 130150 stage
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Moves tribo arm
Soloist motion
controller
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Stage sends voltage
signal to controller
Processes stage’s
digital voltage
signal into position
Controller transforms
signal into position
value
Computer receives
position value via USB
Tribometer
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Arm + probe
4 strain gauges
Moving stage/platform- 1-D motion
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Motion controller sends position to computer as +V
M
Signal Conditioning Board
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Powers strain
gauges,
receives strain
signal from
strain gauges
Excitation
voltage (Vin)
controlled via
potentiometers
(1.25-2.5 V)
Output voltage
(Vg) nulled via
potentiometers
Figure 2-1. SC-2043-SG Parts Locator Diagram- NI manual
Int/ext excitation jumpers
Vin potentiometer
+Vin
+Vg
Cable to PCI
Vg Potentiometer
M
Bending  ΔR
Computer- LabVIEW
program
Signal boardWheatstone
bridge
ΔR  ΔV
Microsoft ClipArt
ΔV  Ff
Ff / FN = μ
http://sine.ni.com/images/products/us/1sc567a1m.jpg
LabVIEW
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Programming environment
Data acquisition/analysis focus
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Logging, graphing, etc.
Graphical programming language
Human-Machine Interface
http://www.mathworks.com/company/newsletters/news_notes/dec04/images/mlint_srccode_wl.gif
http://www.mezintel.com/LVCode01.png
Data structure
Input voltage signals
stage and
signal conditioning board
Position data
Friction data
Converted by
motion controller
Convert w/ calibration
Program Structure
Run
Stage/controller:
Oscillate
DAQ card:
Collect
Receive, convert
friction data
Calculate position data
w/ # data points collected, start point
Record as (x, y) pts, graph
Re-sync every half-cycle
Calibration
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Arm turned on
side
Multiple loads
applied
Linear regression
Y-intercept, slope
convert voltage to
friction
Calibration 8/7/08
Voltage (mV)
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10.000
9.000
8.000
7.000
6.000
5.000
4.000
3.000
2.000
1.000
0.000
0.000
y = 0.0169x + 0.2866
R2 = 0.999
100.000
200.000
300.000
Load (g)
400.000
500.000
600.000
Friction vs. cycle
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Friction (y) vs.
cycle (x)
Allows analysis over
many cycles
Account for debris,
reactions, etc.
Friction vs. position
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Friction (y) vs.
position (x)
Updates real-time
Provides
coordinates of
friction anomalies
Intensity plot
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Pseudo-3D
Friction (color)
vs. position (y)
vs. cycle (x)
Combines
previous two
graphs
Conclusion
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LabVIEW program
Integrates positional and frictional data
Extracts data as CSV and TXT files
Graphs friction vs. cycle, friction vs.
position, friction vs. position vs. cycle
Future Applications
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Integrate with microscopy or spectroscopy
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Use coordinates of frictional event in other
analysis instrument
Example- FTIR of nanocrystalline diamond
films
Acknowledgements
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Nimel Theodore
Kathy Wahl
Irwin Singer
Jeffrey Weimer
SEAP
ONR