Towards Automated Soil Preparation for Planetary Rovers Methods for Reproducible Measurements in Regolith Simulants Roy Lichtenheldt, Jean-Yves Burlet, Fabian Buse and Bernhard Rebele > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017 DLR.de • Chart 1
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Towards Automated Soil Preparation for Planetary Rovers · •Especially homogeneity benefits from automated preparation Outlook •Implementation on the robotic testbed •Full automation
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Towards Automated Soil Preparation for Planetary Rovers
Methods for Reproducible Measurements in Regolith Simulants
Roy Lichtenheldt, Jean-Yves Burlet, Fabian Buse and Bernhard Rebele
> Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017 DLR.de • Chart 1
Needs for Soil Preparation
• Full System Tests
• Hardware evaluation
• System model validation
• Component tests (e.g Single wheel):
• Wheel design and optimization
• Hardware evaluation
• Validation of terramechanics models
> Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017 DLR.de • Chart 2
Conventional Single Wheel Testbed
• Parallel kinematics suspension
• 5,5 m sandbox (~ 3.5 m test length)
• Multiple lanes
• Different operation modes:
• Fixed slip
• Free slip
DLR.de • Chart 3 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
Soil simulant: RMCS-13
• Based on Carbonates
• Very fine grained material (µm to sub µm scale)
• Clodding on grain scale Aggregation of grains
• Wide range of possible properties:
• Extremely soft
• Moderate strength
• Highly compacted
• Allows for tests of different conditions with one soil
• Highly sensitive to preparation
DLR.de • Chart 4 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
Manual Soil Preparation
DLR.de • Chart 5 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
Loosening Method
DLR.de • Chart 6 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
• Three pronged rake
• Trade-off between loosening
and load
• 45° angled prongs
• Parameters:
• Number of passes
• Depth of passes
• Lateral position
• Compared to manual preparation
- Higher density
+ More homogeneous
Compression Method
DLR.de • Chart 7 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
• Compression sled
• Fixed and free version
• Deformable contact surface
• Parameters:
• Number of passes
• Direction of passes
• Depth of passes
• Vertical load
• Results
+ Equal compression
+ More homogeneous
DLR.de • Chart 8
Terramechanics Robotics Locomotion Lab (TROLL)
Single wheel test facility based on an industrial robot • holonomic or force constraint independently selectable for each
DOF
Automated functions • Soil preparation (planned)
• Soil characterization (planned)
• Testing
Test capabilities • conventional or extended single wheel tests
(curves, tilting, etc.)
• Subsystem and Hardware-in-the-Loop tests
(e.g. half rover in simulation, half in hardware)
• Durability tests
Technical data • Wheel dimensions up to ~ 0.5m diameter
• Normal loads up to ~ 2.5kN
> Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
TROLL – Single Wheel Experiment
DLR.de • Chart 9 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
TROLL – Planned Soil Preparation
• Method
• Based on shown method
• Extended by overlayed motions
• Utilizes same functionality as testing
• Hardware
• Separate robot tool
• Compaction and loosening side
• Expected loads within range of robot and sensor
DLR.de • Chart 10 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
Tool changer
Force torque sensor
Compression Tool
Loosening Tool
Conclusion
• Proposed a method for automated soil preparation including:
• Tools to loosen and compress soil
• A method and parameters to prepare the highly sensitive RMCS-13
• Results are similar or better than manual preparation
• Especially homogeneity benefits from automated preparation
Outlook
• Implementation on the robotic testbed
• Full automation
• Broader range of parameters and tools
• Tests in different soils
DLR.de • Chart 11 > Towards Automated Soil Preparation for Planetary Rovers > Lichtenheldt > 21.06.2017
Thank you for your attention!
Questions?
DLR.de • Chart 12
Roy Lichtenheldt, Jean-Yves Burlet, Fabian Buse and Bernhard Rebele