towards automated soil preparation for planetary rovers · •especially homogeneity benefits from...

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


Manual Soil Preparation


Loosening Method


• 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


• 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


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


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


Thank you for your attention!

Questions?

DLR.de • Chart 12

Roy Lichtenheldt, Jean-Yves Burlet, Fabian Buse and Bernhard Rebele

German Aerospace Center (DLR)

Institute of System Dynamics and Control

Robotics and Mechatronics Center

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