ultrasonically assisted blade for lunar excavation
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Ultrasonically Assisted Blade Technologies for Lunar Excavation
Granular Dynamics Session
Erin Rezich1, Kerri Harrigan2, Fransua Thomas1, Damian Ludwiczak11NASA Glenn Research Center, Materials and Structures Division,
Cleveland, OH 441352Washington College, Chestertown, Maryland, 21620
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Introduction• Lunar gravity poses an enormous challenge for
designing excavation technologies and methods• Terrestrial excavation methods rely heavily
massive machinery and use of the vehicle’s own weight to react large excavation forces
• The design challenge for lunar excavation is to develop an excavation tool that reduces the required reaction force such that mass and power can be minimized
• The purpose of this study was to examine the potential usefulness of resonant ultrasonic vibrations in lunar digging implements
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https://www.popsci.com/bagger‐288‐facts/
Szabo, B., Barnes, F., Sture, S. and Ko, H. (1998). EFFECTIVENESS OF VIBRATING BULLDOZER AND PLOW BLADES ON DRAFT FORCE REDUCTION. Transactions of the ASAE, 41(2), pp.283‐290.
BackgroundUsing vibration to decrease excavation forces exists in three primary categories which are important to define:
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• Resonant vibration tools: In most cases, a piezoelectric transducer ultrasonically excites a metal “horn” or probe, usually a Ti‐Al‐4V alloy, which vibrates in the resonant, longitudinal mode.
• Percussive tools: A free mass is excited, often with an ultrasonic probe, which impacts a tool periodically to create a pressure wave within the tool.
• Rigid body reciprocation tools: The whole tool experiences oscillatory, rigid‐body motion driven by an actuator with no intentional resonant vibration present.
Longitudinal vibration
MethodologyExperimental Setup• VCS500 ultrasonic processor• 50 lbf uniaxial load cell• Actuator controls driven by custom Arduino set up• Actuator and load cell data collected by Arduino• All tests were conducted in GRC‐3 under a
repeatable, compacted soil condition• Soil tubes were sized appropriately with boundary
effects taken into consideration
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MethodologyParameters tested:• Vibration frequency is fixed to 20 kHz nominally,
and the VCX500 unit has feedback control• Vibration amplitude was changed as a percent of
the max amplitude for each horn• Downward velocity was changed incrementally
with the actual average velocities calculated for each run
• Penetration depth was a fixed value• Two separate probe geometries were tested to
give broad understanding of the effect of geometry 5
Nominal Range or Value Tested
Increments Tested
Downward velocity 2.0 – 6.9 mm/sec 2.0, 3.3, 3.9, 5.7, 6.9 mm/secFrequency of vibration 20 kHz -
Cylinder probe vibration amplitude
0 – 114 µm 28.5µm
Arrowhead probe vibration amplitude
0 – 120 µm 30 µm
Penetration depth 47 mm -
Results
0102030405060708090
100
0 30 60 120
Forc
e (N
)
Amplitude (µm)
Arrowhead ProbeAverage Max Force vs Amplitude
2.0 mm/sec3.3 mm/sec3.9 mm/sec5.7 mm/sec6.9 mm/sec
0
50
100
150
200
250
0 28.5 57 114
Forc
e (N
)
Amplitude (µm)
Cylinder ProbeAverage Max Force vs Amplitude
2.0 mm/sec3.3 mm/sec3.9 mm/sec5.7 mm/sec6.9 mm/sec
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Results
% 𝑓𝑜𝑟𝑐𝑒 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 1𝑓𝑓
• 𝑓 : average maximum force for a given vibration amplitude, 𝑛 [µm], and penetration velocity, 𝑚 [mm/sec]
• 𝑓 : average maximum force vibration for 0 µm amplitude and penetration velocity of 𝑚 mm/sec.
0%
20%
40%
60%
80%
30 60 120
Perc
ent
Forc
e R
educ
tion
Amplitude (µm)
Arrowhead ProbeReduction of Max Force vs Amplitude
2.0 mm/sec3.3 mm/sec3.9 mm/sec5.7 mm/sec6.9 mm/sec
0%
20%
40%
60%
80%
28.5 57 114
Perc
ent F
orce
Red
uctio
n
Amplitude (µm)
Cylinder ProbeReduction of Max Force vs Amplitude
2.0 mm/sec3.3 mm/sec3.9 mm/sec5.7 mm/sec6.9 mm/sec
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Conclusions• Results generated suggest 20 kHz, longitudinal vibrations in the probe significantly
reduce penetration force in compacted, granular, lunar soil simulant• Cylinder geometry saw max force reductions upwards of 70%• Arrowhead geometry saw max force reductions of about 50% with a larger error band
• Geometry of the probe has a pronounced and interesting effect• The cylindrical probe saw much higher forces but also much higher force reductions• The arrowhead probe saw lower forces and reductions, but larger error bands
• Velocity and vibration amplitude are loosely coupled to the overall force in this regime• These effects could be directional and might have more profound impact at different angles of
attack
• Overall, the results were very positive and warrant further investigation as to how this technology could be incorporated into the leading edge of excavation tools
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AcknowledgementsThe authors would like to extend their gratitude to Richard Manco of HX5 Sierra LLC at NASA Glenn Research Center.
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