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Computer Automation of a Tribometer Michael Eng, TJHSST With Nimel Theodore, Kathy Wahl NRL Code 6176

Objective 

Main goal- integrate positional data w/ friction collection 



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      

Reciprocating stage Tribometer Circuit board Program structure Sample output Applications

Stage and Controller 

Aerotech ALS 130150 stage 



Moves tribo arm

Soloist motion controller 

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   

Arm + probe 4 strain gauges Moving stage/platform- 1-D motion 

Motion controller sends position to computer as +V M

Signal Conditioning Board 





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  

Programming environment Data acquisition/analysis focus 

 

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



 

Arm turned on side Multiple loads applied Linear regression Y-intercept, slope convert voltage to friction

Calibration 8/7/08

Voltage (mV)



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 





Friction (y) vs. cycle (x) Allows analysis over many cycles Account for debris, reactions, etc.

Friction vs. position 

 

Friction (y) vs. position (x) Updates real-time Provides coordinates of friction anomalies

Intensity plot  



Pseudo-3D Friction (color) vs. position (y) vs. cycle (x) Combines previous two graphs

Conclusion    

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 

Integrate with microscopy or spectroscopy 



Use coordinates of frictional event in other analysis instrument

Example- FTIR of nanocrystalline diamond films

Acknowledgements     



Nimel Theodore Kathy Wahl Irwin Singer Jeffrey Weimer SEAP ONR