Carnegie Mellon | 13 December 20071 Testing and Characterization 13-14 December 2007 Carnegie Mellon.

Carnegie Mellon | 13 December 2007 1

Testing and Characterization

13-14 December 2007Carnegie Mellon

Scarab Testing & CharacterizationCarnegie Mellon13-14 December 2007

Scott Moreland

Carnegie Mellon | 13 December 2007 3

Characterization

• Mobility– CG xyz, Static tip-over angles– Drawbar Pull– Side slope lean (level) vs. baseline– Straight incline ascent, lowering CG– Obstacles: trenching, boulders, etc..

• Drilling– Gravity off-load Can enough thrust be produced? Resist torques?– Drill thrust/torque extremes simulation– Slopes

Carnegie Mellon | 13 December 2007 4

Vehicle Center of Gravity• X-Y CG

Total Weight: 280 kg• Drill system

mass/CG stand-in• ASRG used to center

vehicle CG

• Z CG Pose Dependent

*nominal

*low

*high

Carnegie Mellon | 13 December 2007 5

Static Tip-Over Angles

*low

*nominal

*high

(values from tilt-table testing)

Carnegie Mellon | 13 December 2007 6

Side Slope

• Side Slopes– Significant increase in traction while

body leveling on side slopes– 25° cross slope results

• 52% decrease in downhill slip

• Important sources of beneficial effects (side hill lean)– Edging of wheels– Equalize wheel pressure distribution

• Actively centering CG over track-base center

• Traction and control

Carnegie Mellon | 13 December 2007 7

Side Slope

• Side Slopes– Significant increase in traction while

body leveling on side slopes– 25° cross slope results

• 52% decrease in downhill slip

• Important sources of beneficial effects (side hill lean)– Edging of wheels– Equalize wheel pressure distribution

• Actively centering CG over track-base center

• Traction and control

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Carnegie Mellon | 13 December 2007 8

Straight Hill Ascent

• Straight Ascent (pose vs. angle of refusal)– 25° incline tests:

• refuse at high pose, ascends at nominal/low pose

– Lowering CG through pose change promotes equal normal force distribution in wheels increases angle of refusal

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Carnegie Mellon | 13 December 2007 9

Drawbar Pull

•Tested at full vehicle weight, 280 kg

•XY-CG centered

•Rubber skid loader tires

•60 cm diameter

•17 cm tread width

•Coarse Sand:

•160 kg pull

•0.57 vehicle weight

•High Traction Cement

•240 kg pull

•0.85 vehicle weight

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• Trenching– 50 cm Trench capability– Wheel Diameter, 60 cm

• Boulders

• Periodic obstacles

Obstacles

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Carnegie Mellon | 13 December 2007 11

Drilling• Nominal Drilling Test

– Support 1 m drilling into OB-1 lunar regolith simulant with NORCAT system

• Gravity Off-loading– Drill reaction forces simulated while under lunar g

• Drill reaction forces– 350 N max. thrust– 30 Nm torque

• 250 kg Earth 42 kg Lunar (gravity off-loaded)• 42 kg weight – 350 N thrust 6.0 kg Mass Reserve

– Capabilities• Expanded wheel base resists high drill torques

– Failures• Combined loading: Lunar gravity while drilling on

slopes > 15°, leads to downhill slippage• Down hill force rapidly increasing with slope angle

Carnegie Mellon | 13 December 2007 12

Specifications

Drill tower (upright): 2.2 m high stance, 1.6 m low stanceMass: 280 kg Weight: 460 N 2750 N Nominal power: 200 W (driving), 380 W (pose change) Idle power: 78 WLocomotion speed: 5.0 – 6.0 cm/sTrack width: 1.4 mWheelbase: 0.8 - 1.3 m Aspect ratio (track/wheelbase): 1:1 low stance, 1:2 nominal, 1:7 highCG height: 0.64m nominal stance, 0.60m low, 0.72m

highStatic pitchover: 42° nominal stance, 29° high, 45° low Static rollover: 53° nominal stance, 48° high, 55° lowMaximum / minimum straddle: 57 cm, Belly contactApproach / departure angle: 105° nominal stanceWheel diameter: 60 cmRim pull (single wheel): 2500 NDrawbar pull: 1560 N (medium-coarse grain sand)

} with full drill

system payload