Massively Parallel Discrete Element Modeling of Legged Mobility on Granular Terrain

2013 ◽  
Author(s):  
Rudranarayan Mukherjee ◽  
Isaac Kim
Keyword(s):  
First Principles ◽  
Granular Media ◽  
Discrete Element ◽  
Massively Parallel ◽  
High Fidelity ◽  
Discrete Element Modeling ◽  
Ground Vehicle ◽  
Ground Reactions ◽  
Natural Terrain ◽  
Time Frames

Legged mobility of robotic systems is an active area of research. Quantitatively understanding mobility of these systems on natural terrain is critical for design and operations of these systems. In this paper, we present results of computational simulations of legged mobility on granular terrain using massively parallel Discrete Element Method. We model the interactions of a leg from a micro ground vehicle with sandy terrain made of polydispersed granular media. In these simulations, we model the interactions between millions of granules and the leg to quantify ground reactions and associated qualitative behaviors. The simulations are run on parallel computers to overcome the severe computational complexity of simulating these large problems in physically feasible time-frames. We are using high fidelity first-principles approaches to model emergent complex behavior that cannot otherwise be modeled. We present results from a parametric sweep where different leg speeds and penetrations are used to understand differences in ground reaction.

Massively Parallel Discrete Element Modeling of Wheeled Mobility on Granular Terrain

2013 ◽  
Author(s):  
Ryan Houlihan ◽  
Rudranarayan Mukherjee
Keyword(s):  
Granular Media ◽  
Discrete Element ◽  
Emergent Behavior ◽  
Massively Parallel ◽  
Discrete Element Modeling ◽  
Ground Vehicles ◽  
Element Modeling ◽  
Dynamic Mobility ◽  
Parametric Studies ◽  
Wheeled Mobility

Quantitatively understanding wheeled mobility on granular terrain such as sand or gravel is critical for design and operations of ground vehicles for terrestrial or extra-terrestrial applications. While the Bekker-Wong theory of wheeled mobility and its derivatives have been used in many applications, the static nature of these formulations are limiting in understanding mobility in deformable terrain under dynamic mobility conditions. Single wheel hardware experiments in laboratory settings and detailed modeling of wheel-terrain interactions are two avenues currently being actively pursued to develop quantitative understanding of wheeled mobility. In this paper, we present findings of massively parallel discrete element modeling of wheeled mobility on granular media such as sand. We present a brief overview of the underlying methodology and then focus on the results of the simulation. In these simulations, we model the inter-granular interactions and interactions between the wheel and the granules with an objective of using high fidelity first-principles approach to capture emergent behavior in these complex and highly dynamic phenomena. These simulations typically model millions of granules and use highly scalable software and parallel computing resources to overcome the severe complexity of the problem. We present results of parametric studies with varying levels of both wheel penetration and mobility conditions. These have been modeled to present a quantitative perspective of the diverse behaviors encountered in wheeled mobility on granular terrain. We have retained the full complexity of the problem by simulating granules of the size encountered in real terrain to overcome the fidelity limited issues of other comparable methods that use much larger granules.

Massively Parallel Granular Media Modeling of Robot-Terrain Interactions

2012 ◽  
Author(s):  
Rudranarayan M. Mukherjee ◽  
Ryan Houlihan
Keyword(s):  
Force Field ◽  
Granular Media ◽  
Robotic Systems ◽  
Massively Parallel ◽  
Discrete Element Modeling ◽  
Damping Force ◽  
Computing Systems ◽  
Massively Parallel Computing ◽  
Micro Gravity ◽  
Robotic Tools

This paper presents select results that demonstrate the feasibility of modeling the interactions of robotic systems with granular terrain through Discrete Element Modeling (DEM) using massively parallel computing systems. We report numerical simulation results of full 3D DEM simulations with the granular material modeled as a deformable bed of spherical granules. The mobility systems of the robots retain their CAD geometry and are represented as triangular meshes. The inter-granular interactions and the interactions between the CAD mesh triangles with the granules are modeled explicitly using a deformation-damping force field. The parameters of the force field are derived from physically measurable properties. We model friction, cohesion, and shearing and other interactions among the granules, and between the CAD mesh and the granules. The simulations involve granular beds with number of granules in the order of several hundred thousand to several millions. Temporally, we report simulations in the order of several seconds. These simulations were run on parallel clusters with number of processors ranging from 100 to 256. We present the findings from a number of simulations ranging including wheeled and legged mobility systems, and robotic tools in micro-gravity environments.

Modeling of Granular Flow and Combined Heat Transfer in Hoppers by the Discrete Element Method (DEM)

2005 ◽  
Vol 128 (3) ◽  
pp. 439-444 ◽  
Author(s):  
Harald Kruggel-Emden ◽  
Siegmar Wirtz ◽  
Erdem Simsek ◽  
Viktor Scherer
Keyword(s):  
Discrete Element Method ◽  
Heat Transport ◽  
Granular Flow ◽  
Granular Media ◽  
Element Model ◽  
Discrete Element ◽  
Waste Utilization ◽  
Discrete Element Modeling ◽  
Particle Assemblies ◽  
Element Method

The discrete element method can be used for modeling moving granular media in which heat and mass transport takes place. In this paper the concept of discrete element modeling with special emphasis on applicable force laws is introduced and the necessary equations for heat transport within particle assemblies are derived. Possible flow regimes in moving granular media are discussed. The developed discrete element model is applied to a new staged reforming process for biomass and waste utilization which employs a solid heat carrier. Results are presented for the flow regime and heat transport in substantial vessels of the process.

Discrete Element Simulation (DEM) for Coupled Description of Material and Energy Flow Within Moving Granular Media

2005 ◽  
Author(s):  
Harald Kruggel-Emden ◽  
Siegmar Wirtz ◽  
Erdem Simsek ◽  
Viktor Scherer
Keyword(s):  
Heat Transport ◽  
Energy Flow ◽  
Granular Media ◽  
Element Model ◽  
Discrete Element ◽  
Waste Utilization ◽  
Discrete Element Modeling ◽  
Discrete Element Simulation ◽  
Element Simulation ◽  
Particle Assemblies

The discrete element method (DEM) can be used for modeling moving granular media in which heat and mass transport takes place. In this paper the concept of discrete element modeling with special emphasize on applicable force laws is introduced and the necessary equations for heat transport within particle assemblies are derived. Possible flow regimes in moving granular media are discussed. The developed discrete element model is applied to a new staged reforming process for biomass and waste utilization which employs a solid heat carrier. Results are presented for the flow regime and heat transport in substantial vessels of the process.

scholarly journals Three-dimensional discrete element modeling of triggered slip in sheared granular media

2014 ◽  
Vol 89 (4) ◽  
Author(s):  
Behrooz Ferdowsi ◽  
Michele Griffa ◽  
Robert A. Guyer ◽  
Paul A. Johnson ◽  
Chris Marone ◽  
...  
Keyword(s):  
Granular Media ◽  
Three Dimensional ◽  
Discrete Element ◽  
Discrete Element Modeling ◽  
Element Modeling

scholarly journals An Energy-Based Discrete Element Modeling Method Coupled with Time-Series Analysis for Investigating Deformations and Failures of Jointed Rock Slopes

2021 ◽  
Vol 11 (12) ◽  
pp. 5447
Author(s):  
Xiaona Zhang ◽  
Gang Mei ◽  
Ning Xi ◽  
Ziyang Liu ◽  
Ruoshen Lin
Keyword(s):  
Time Series ◽  
Iterative Process ◽  
Discrete Element ◽  
Jointed Rock ◽  
Modeling Method ◽  
Discrete Element Modeling ◽  
Rock Slopes ◽  
Sliding Surface ◽  
Element Modeling ◽  
Displacement Based

The discrete element method (DEM) can be effectively used in investigations of the deformations and failures of jointed rock slopes. However, when to appropriately terminate the DEM iterative process is not clear. Recently, a displacement-based discrete element modeling method for jointed rock slopes was proposed to determine when the DEM iterative process is terminated, and it considers displacements that come from rock blocks located near the potential sliding surface that needs to be determined before the DEM modeling. In this paper, an energy-based discrete element modeling method combined with time-series analysis is proposed to investigate the deformations and failures of jointed rock slopes. The proposed method defines an energy-based criterion to determine when to terminate the DEM iterative process in analyzing the deformations and failures of jointed rock slopes. The novelty of the proposed energy-based method is that, it is more applicable than the displacement-based method because it does not need to determine the position of the potential sliding surface before DEM modeling. The proposed energy-based method is a generalized form of the displacement-based discrete element modeling method, and the proposed method considers not only the displacement of each block but also the weight of each block. Moreover, the computational cost of the proposed method is approximately the same as that of the displacement-based discrete element modeling method. To validate that the proposed energy-based method is effective, the proposed method is used to analyze a simple jointed rock slope; the result is compared to that achieved by using the displacement-based method, and the comparative results are basically consistent. The proposed energy-based method can be commonly used to analyze the deformations and failures of general rock slopes where it is difficult to determine the obvious potential sliding surface.

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