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OFF-ROAD SOFT SOIL TIRE MODEL

DEVELOPMENT, VALIDATION, AND

INTERFACE TO COMERCIAL MULTIBODY

DYNAMICS SOFTWARE

Graduate Students: Mr. Shahyar Taheri (Jan 2012-present), Mr. Scott Naranjo (Jan. 2011-June 2013), Virginia Tech

Primary Investigator: Dr. Corina Sandu, Director AVDL, Dr. Saied Taheri, Director CenTIRe

• U.S. Army Quad Member: Dr. David Gorsich (Sept. 2013-present), Dr. Paramsothy Jayakumar (Jan. 2011-Sept. 2013), TARDEC

• Industry Quad Members: Dr. Brant Ross, MotionPort, Mr. Daniel Christ, Michelin Americas Research Co

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Agenda

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Introduction

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Methodology

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Tire Structure Modeling

Middle Layer Top view Side Layer

Three layer tire model

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Comparison: FTire and AS2TM

Belt Circumferential Torsion

and Twist Stiffness red: ‘torsion’

stiffness; blue: ‘twist’ stiffness

Out-of-Plane Bending

Stiffness

Belt Lateral Bending

Stiffness

Inplane-Plane Bending

Stiffness

FTire model structure AS2TM model structure

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Tire-soil interaction

Tire-soil

contact

3D soil

elevation map

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• Discretization of tire-soil interface and soil surface for contact search algorithm

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Tire-soil interaction

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• Tire element velocity vector components effect on soft soil

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Simplified Ground Model

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• Contact search (light blue), and contact interface (dark blue) algorithm

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Tire Parameterization

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• Model input parameters are measured through three main set of experiments

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Simulation Results

Tire deformation on a elliptic

shape cleat

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• Tire model is capable of enveloping cleats and negotiation uneven terrain

Uneven terrain simulation shows

how the contact patch deform

relative to the ground

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Simulation Results

Radial and tangential forces from an

integration point located at 0 degree

when tire starts moving on a flat surface

with 50 N.m torque

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• Real dynamic tire model behavior illustrated by cleat test and acceleration test

Vertical force at rim center

during running over a

rectangular cleat

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1000

-500

0

500

1000

Vert

ica

l fo

rce

at

rim

ce

nte

r (N

)

Horizontal Distance (m)

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

20

40

Cle

at H

eig

ht

(mm

)

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Simulation Results

Uneven Rigid Ground Simulation Video

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Simulation Results

Quasi–static soil deformation

under 2000 N loading

Vertical position of a dropping tire on soft

soil

0.1 0.2 0.3 0.4 0.5-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

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• Static deflection of tire on soft soil, and dynamic deflection of a dropping tire

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Simulation Results

Soft Soil Simulation Video

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Terramechanics Rig (Indoor Testing Platform)

• Simulates a quarter-car model that

focuses solely on tire dynamics

– Wheel slip control via two separate

drive motors

– Active normal load control

• Measures forces and moments caused by

the tire-soil interaction via wheel hub

Kistler P 650 sensor

Test Tire: Michelin LTX A/T2 235/85/R16

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Conclusion

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Modeling

Tire structure EOMs developed.

Pressure effect, adaptive contact patch, rotational DOF, contact model,

combined slip, uneven terrain, soil model included

Software developed in MATLAB, and optimized computationally

Communication interface developed for using in conjunction with other MBDS

Results validated with experiments

First version of the code (1.1.0) delivered to MotionPort for compatibility check

Tire parameterization document including all required parameters and test

procedures delivered

User manual for the code (Version 1.1.0) completed

Experimental

Tire instrumented with wireless real-time deflection system

Normal load controller hardware installed, and required software developed

Field scanners installed (used with other sensors for sinkage measurements)

Various tests from design of experiment performed