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www.DLR.de Slide 1 <ASTRA 2013> < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt 17.05.2013 Locomotion on soft granular Soils A Discrete Element based Approach for

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SLIDE 1

www.DLR.de • Slide 1

Locomotion on soft granular Soils

A Discrete Element based Approach for Simulations in Planetary Exploration

Roy Lichtenheldt1, Bernd Schäfer2

German Aerospace Center (DLR)

1Institute of System Dynamics and Control 2Institute of Robotics and Mechatronics

Robotics and Mechatronics Center

<ASTRA 2013> < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 2
  • 1. Introduction
  • 2. Contact models
  • 3. Parameter estimation
  • 4. Models & Results
  • 5. Conclusion &

Further steps Outline

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013 www.DLR.de • Slide 2

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SLIDE 3

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

  • 1. Introduction

State of the art models

Empirical – Bekker/Reece/Wong Finite Element Method Smoothed Particles Hydrodynamics Continuum based methods

www.DLR.de • Slide 3 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

[6] [5] [4]

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SLIDE 4

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

  • 1. Introduction

State of the art models

Empirical – Bekker/Reece/Wong Finite Element Method Discrete Element Method Smoothed Particles Hydrodynamics Continuum based methods Particle based methods (discrete, meshfree)

www.DLR.de • Slide 4 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 5

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

  • 1. Introduction

Discrete Element Method

 Particle based meshless method  No fixed neighbours  Contact driven force/torque calculation  Capable of covering high plastic deformation www.DLR.de • Slide 5 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 6

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

  • 1. Introduction

Discrete Element Method

 Particle based meshless method  No fixed neighbours  Contact driven force/torque calculation  Capable of covering high plastic deformation www.DLR.de • Slide 6 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 7

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

 Simulation domain consists of discrete particles  Particle interaction based on contacts  Forces and torques derived from contact models  New position calculated from integration of the principles of linear and

angular momentum

Discrete Element Modeling

  • 2. Contact models

www.DLR.de • Slide 7 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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  • 2. Tilting contact model

Resistance torque

 Resistance torque due to tilting  Torque from tangential as well as normal forces  1 additional parameter: aspect ratio www.DLR.de • Slide 8 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 9
  • 2. Tilting contact model

Resistance torque

 Resistance torque due to tilting  Torque from tangential as well as normal forces  1 additional parameter: aspect ratio www.DLR.de • Slide 9 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 10
  • 2. Tilting contact model

Resistance torque

 Resistance torque due to tilting  Torque from tangential as well as normal forces  1 additional parameter: aspect ratio www.DLR.de • Slide 10 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 11

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Determining the contact parameters

  • 3. Parameter estimation

 Stiffness calculation dependent on the overlap www.DLR.de • Slide 11 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 12

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Determining the contact parameters

  • 3. Parameter estimation

 Stiffness calculation dependent on the overlap  Damping is derived as a fraction of critical damping  Tangential stiffness and damping derived from normal direction  Particle size determined by min. resolution  Particle shape approximated by torque law www.DLR.de • Slide 12 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 13

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Determining the contact parameters

  • 3. Parameter estimation

 Stiffness calculation dependent on the overlap  Damping is derived as a fraction of critical damping  Tangential stiffness and damping derived from normal direction  Particle size determined by min. resolution  Particle shape approximated by torque law www.DLR.de • Slide 13 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 14

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Determining the contact parameters

  • 3. Parameter estimation

 Stiffness calculation dependent on the overlap  Damping is derived as a fraction of critical damping  Tangential stiffness and damping derived from normal direction  Particle size determined by min. resolution  Particle shape approximated by torque law  Friction and rolling parameters stored in look-up tables www.DLR.de • Slide 14 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 15

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Verification: Bevameter pressure sinkage test

  • 4. Models & Results

www.DLR.de • Slide 15 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

  • Pressure sinkage test

performed in simulation and measurement

  • RMC-Soil_03  milled

lava soil

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SLIDE 16

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Simulations for planetary rover wheels

  • 4. Models & Results

 Wheel modeled as fully dynamic triangulated surface  Symmetry conditions used to decrease computation time  Covering macroscopic soil deformation by grain relocation www.DLR.de • Slide 16 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 17

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

Simulations for planetary rover wheels

  • 4. Models & Results

 Wheel modeled as fully dynamic triangulated surface  Symmetry conditions used to decrease computation time  Covering macroscopic soil deformation by grain relocation www.DLR.de • Slide 17 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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  • 4. Models & Results

Parametric wheel development

  • Usage of simulations for virtual prototyping
  • Better understanding of the influence of the design parameters on

the wheel’s performance

  • First example: steady state slip for different grouser numbers

www.DLR.de • Slide 18 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 19
  • 4. Models & Results

Parametric wheel development

www.DLR.de • Slide 19 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 20

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013 www.DLR.de • Slide 20

co-simulation mechanism behaviour is soil dependent find design optimum suitable for a variety of soils + better understanding of the interaction

  • 4. Models & Results

HP³-Mole Analysis & Optimization

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SLIDE 21

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013 www.DLR.de • Slide 21

co-simulation mechanism behaviour is soil dependent find design optimum suitable for a variety of soils + better understanding of the interaction

  • 4. Models & Results

HP³-Mole Analysis & Optimization

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  • 5. Conclusion & Further steps

DEM

Rover wheels

  • Discrete Element Method applied to rover wheels
  • Efficient modeling of interparticle contact and rolling behaviour
  • Parameter estimation strategy
  • First verification using the bevameter test
  • Parametric wheel development

HP3-Mole

  • Multibody Simulation & Optimization of the hammering

mechanism

  • Modeling of the soil interaction using Discrete Element

Method

www.DLR.de • Slide 22 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 23
  • 5. Conclusion & Further steps

DEM

Rover wheels

  • Computational efficiency
  • Validation  Single Wheel Testbed
  • Influences & wheel development
  • New analytical & empirical models

HP3-Mole

  • Co-simulation MBS-DEM
  • Further optimization

www.DLR.de • Slide 23 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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SLIDE 24

Thank you for your attention!

< Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

www.DLR.de • Slide 24 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013

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Quellen:

[1] InSight Homepage, http://insight.jpl.nasa.gov/, 13.02.2013 [2] The Heat Flow and Physical Properties Package HP³, DLR Institute of Space Systems [3] Grzesik, A.: Konstruktion eines Schlagmechanismus für einen instrumentierten Penetrator zur Bodenerkundung bei Planetenmissionen (Mercury Surface Element), Diplomarbeit, Fachhochschule Aachen, 2004 [4] Krenn, R.; Hirzinger, G. - SCM – A soil contact model for multi-body system

  • simulations. 11th European Regional Conference of the International Society for

Terrain-Vehicle Systems - ISTVS 2009 , 2009 , Bremen [5] Pruiksma, J.P. et.al. - Tractive performance modelling of the ExoMars Rover wheel design on loosely packed soil using the Coupled Eulerian Lagrangian Finite Element Technique, 2011 [6] Orr, M.K. – Development of a Finite Element Model to predict the behavior of a prototype wheel on lunar soil, Dissertation, Clemson University, 2010

www.DLR.de • Slide 25 < Locomotion on soft granular soils - A DEM based approach for planetary exploration > Roy Lichtenheldt • 17.05.2013