Pneumatic Sampling in Extreme Terrain with the Axel Rover

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Pneumatic Sampling in Extreme Terrain with the Axel Rover
Yifei Huang Frank W. Wood SURF Fellow

Overview Motivation Pneumatic Sampling Design & Testing Conclusions
Concept, and feasibility Design & Testing Nozzle Cyclone Sample Container Pressure Container Instrument Deployment Conclusions

Sampling in Extreme Terrain
Satellite images suggest liquid brine flow Spectroscopy images – negative results for water Difficulties in sampling Newton Crater: degree slopes MER:15 degree slopes Curiosity: 30 degree slopes Solution Axel rover: vertical slopes Figure: Sources:

The Axel rover Goal: Develop a sampling system on Axel DuAxel rover
Traversing cliffs Instrument deploy Goal: Develop a sampling system on Axel

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 Dirt in tube Figure: Zacny et al. (2010)

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

Design: Nozzle Round #1 Nozzle #2 Soil Level Nozzle #3 Nozzle #1

Design: Nozzle Nozzles built on the 3D printer (ABS plastic)
Tests with loose sand (400um size) 25psi air was released for 2 sec

Design: Nozzle Round #2 Sand: Dirt: Nozzle #4 Nozzle #5

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 Vortex Finder Cylindrical portion Conical portion Small Particle Large Particle Design by Honeybee Robotics Figure: DB Ingham and L Ma, “Predicting the performance of air cyclones”

Design: Sample Container
Objective: Minimize actuation with springs Concept: Design: Cyclone Sample Container Spring

Design: Instrument Deployment
Second 4-bar linkage attached to original 4-bar Motion of 2 4-bars are coupled Advantages: No actuator on deployed plate Nozzle is attached here

Benchtop test stands Instrument deploy Sample Caching

Design: Pressure Container

Benchtop Test Tests with loose sand (400um size)
25psi air was released for 2 sec

Contamination In sand In dirt
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: % of lifted mass Nozzle: % of lifted mass

Effects of Pressure Tests with loose sand (400um size)
Air from wall was released for 2 sec

Conclusions Pneumatics is feasible Improvements needed:
Successfully acquired 2g of soil Improvements needed: Acquiring moist soils (dirt) Taking multiple samples Placing system inside Axel

Acknowledgements Kristen Holtz, co-worker Funding: Mentoring:
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

Initial Calculations for Earth conditions
Estimate velocity of air: Estimate the mass that can be lifted Assume dirt is inert, ρ=2000kg/m3 Mass = ~12g/s Mars conditions: Requires less canister pressure