Pneumatic Sampling in Extreme Terrain with the Axel Rover

Yifei Huang. 8.23.12Frank 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 LevelNozzle #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

89

0.286 0.536

7.97600000000001

Sand

cap

ture

d (g

ram

s)

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Round #2Design: Nozzle

Nozzle #4

Nozzle #5

Nozzle 4 Nozzle 50

0.5

1

1.5

2

2.5

3

3.5

SandDirt

Amou

nt o

f So

il 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

acqu

ired

(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

Sand

l acq

uire

d (g

ram

s)

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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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