pneumatic sampling in extreme terrain with the axel rover yifei huang. 8.23.12 frank w. wood surf...
TRANSCRIPT
Pneumatic Sampling in Extreme Terrain with the Axel Rover
Yifei Huang. 8.23.12
Frank W. Wood SURF Fellow
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Overview Motivation Pneumatic Sampling
Concept, and feasibility Design & Testing
Nozzle Cyclone Sample Container Pressure Container Instrument Deployment
Conclusions
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Sampling in Extreme Terrain Satellite images suggest liquid brine flow
Spectroscopy images – negative results for water Difficulties in sampling
Newton Crater: 25-40 degree slopes MER:15 degree slopes Curiosity: 30 degree slopes
Solution Axel rover: vertical slopes
Figure: http://mars.jpl.nasa.gov/. Sources: http://ssed.gsfc.nasa.gov/sam/curiosity.html,
http://usrp.usra.edu/technicalPapers/jpl/HooverMay11.pdf
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The Axel roverDuAxel rover
Instrument deploy
Traversing cliffs
Goal: Develop a sampling system on Axel 4
What is pneumatic sampling? 1. Release pressurized air
Actuator opens and closes a cylinder of pressurized air 2. Air flows down the outer tube of the nozzle 3. Air enters inner tube, carrying soil with it
Nozzle is already embedded in dirt Up is the path of least resistance
4. Soil and air flow up into sample container
Figure: Zacny et al. (2010)
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Why Pneumatics? Fewer moving components, low number of
actuators, less risk for failure Closed tubing: low instrument contamination Energy efficient
A small amount of air can lift a large amount of dirt
1 g of gas lifted 5000g of soil [Zacny and Bar-Cohen, 2009]
Easier soil transportation
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Design: Nozzle Round #1
Nozzle #1
Soil Level
Nozzle #2
Nozzle #3
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Design: Nozzle Nozzles built on the 3D printer (ABS plastic) Tests with loose sand (400um size)
25psi air was released for 2 sec
Nozzle 1 Nozzle 2 Nozzle 30
1
2
3
4
5
6
7
8
9
0.286 0.536
7.97600000000001
Sand c
aptu
red (
gra
ms)
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Round #2
Design: Nozzle
Nozzle #4
Nozzle #5
Nozzle 4 Nozzle 50
0.5
1
1.5
2
2.5
3
3.5
SandDirt
Am
ount
of
Soil lif
ted (
gra
ms)
Sand:
Dirt:
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Design: Cyclone Separator Used to separate air and soil Dusty air will enter tangential to
cyclone Larger particles have too much
inertia Hit the side of cyclone and fall
down Smaller particles remain in the
cyclone Pushed up into the Vortex Finder
by pressure gradient
10 Figure: DB Ingham and L Ma, “Predicting the performance of air cyclones”
Vortex Finder
Cylindrical portion
Conical portion
Small Particle Large Particle
Design by Honeybee Robotics
Design: Sample Container Objective: Minimize actuation with springs
Cyclone
Sample Container
Spring
Concept: Design:
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Second 4-bar linkage attached to original 4-bar
Motion of 2 4-bars are coupled Advantages: No actuator on deployed plate
Design: Instrument Deployment
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Nozzle is attached here
Benchtop test stands Instrument deploy Sample Caching
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Design: Pressure Container
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Benchtop Test
Wall air CO2 Canister air (benchtop)0
0.5
1
1.5
2
2.5
3
3.5
4
Soil a
cquir
ed (
gra
ms)
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Tests with loose sand (400um size) 25psi air was released for 2 sec
Contamination In sand
Weighed cyclone, tubing, and nozzle before and after tests
Negligible mass: ~0.2% of lifted mass remained in cyclone/tubing/nozzle
In dirt Soil is stuck inside nozzle and cyclone Cyclone: 50-300% of lifted mass Nozzle: 50-150% of lifted mass
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Effects of Pressure
15psi 25psi 35psi0
0.5
1
1.5
2
2.5
3
3.5
4
Pressure
Sandl acquir
ed (
gra
ms)
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Tests with loose sand (400um size) Air from wall was released for 2 sec
Conclusions Pneumatics is feasible
Successfully acquired 2g of soil
Improvements needed: Acquiring moist soils (dirt) Taking multiple samples Placing system inside Axel
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Acknowledgements Kristen Holtz, co-worker Funding:
Keck Institute for Space Studies Caltech Summer Undergraduate Research
Fellowship (SURF) Mentoring:
Melissa Tanner, Professor Joel Burdick, Caltech JPL Axel Team Kris Zacny, Honeybee Robotics Prof. Melany Hunt, Prof. Bethany Elhmann Paul Backes, Paulo Younse, JPL
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