virtual vehicle systems simulation - university of...

$: Virtual Vehicle Systems Simulation - University of …arc.engin.umich.edu/events/archive/annual/conf00/smid.pdfVirtual Vehicle Systems Simulation †1 =_Te\Qb 1‘‘b_QSX Y^ BUQ\˛DY]U$
AUTOMOTIVE RESEARCH CENTER

Intelligent Vehicle Dynamics and Control

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Oakland UniversitySlide 1

Virtual Vehicle Virtual Vehicle Systems SimulationSystems Simulation

²1=_Te\Qb1``b_QSXY^BUQ\²1=_Te\Qb1``b_QSXY^BUQ\DY]U³DY]U³

G. Edzko Smid, Ph.D.G. Edzko Smid, Ph.D.



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Introduction to VVSSIntroduction to VVSS

Computer technology adds tools to engineering.

Virtual reality for arcade, movie and as a design tool in engineering.

Imagine driving in a virtual realistic vehicle with full feedback.

An engineer can design and modify a subsystem, and analyze the vehicle ride performance immediately.

No knowledge or expertise is required for evaluating vehicle subsystems on full-vehicle simulation.

Implementing a vehicle ride control systems must be a drag and drop exercise.

Networked simulation environment allows for remote simulation subsystems and hardware in the loop

Modularity provides capability for distributed simulation and improved computational performance.



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ContentsContents

• Objective and Applications

• Vehicle Model & Tire Model

• Modularity and Real-Time

• Implementation of UI in MATLAB/Simulink

• Conclusions



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Back groundBack ground

• Many industry activities involve design and testing of automotive systems.

• ITT : ABS, TACOM : Leader-following, suspension, collision warning

• Simulation could be used to replace certain test-track experiments.

• Many simulation packages have black-box dynamics models, are expensive and are not flexible to fit any specific purpose.

• Collaborative online simulation exploit capabilities of internet



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ApplicationsApplications

• Design of vehicle sub-systems (interactive)

• Analysis of vehicle sub-systems (state-access)

• Subjective validation of concept designs

• Facilitate testing of prototype systems

• Benchmark hazardous scenarios

• Education for drivers and customers

• Instrumentation for in-the-loop mechatronics studies



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Laborator y SetupLaborator y Setup



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Virtual Vehicle S ystem Virtual Vehicle S ystem

( )( )uxDuCxy

uxBuAxx

,

,

ς++=η++=State Space Formulation:



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Vehicle Model Vehicle Model -- Free Bod yFree Bod y

Sum of Forces:

( ) windirollideflislipi

FFFFF +++∑==

,,,

4

1

Integration

( )( )kkkk

kkvkk

vvtxx

FFMtvv

+∆+=+∆+=

−−

−−

−

121

1

11

21

1



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Vehicle Model Vehicle Model -- Free Bod yFree Bod y

Sum of Torques:

Angular Body Accelerations:

Roll, Pitch, Yaw :

( )irollio

ideflio

islipio

iFAFAFCT ,,,

4

1×+×+×∑=

=

( )( ) 1−Ω×Ω−=Ω IIT cccc

Ω

θφθφθ−φ

θφθφ=Θ cc

seccossecsin0

sincos0

tancostansin1



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Vehicle Model Vehicle Model -- SuspensionSuspension

( )sFss

KDss

KDzsM zSSSTTTww −=δ

++δ

+σ+ 11

cos2

( )

SSw

ic

ic

SS

ioo

io

TT

Lz

ABL

BIsectBL

δ−=

−−=δ

σ−−=δ ,

Suspension and Tire deflection spoke model

Equation of motion:



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Tire Dynamics ModelTire Dynamics Model

• Existing tire models are either- not related to physical parameters- based on lookup tables

- derived from velocities; requires minimum velocity

• New tire model is introduced, based on two analytical models and physical parameters.

• Fuzzy logic is used for supervisory decision on the actuation of the models, based on the state of the vehicle.



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Tire Dynamics Tire Dynamics -- DugoffDugoff

µ

wheel

vehiclewheelsυ

υ−υ=

Slip coefficient:

Slip ratio:



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Tire Dynamics Tire Dynamics -- DugoffDugoff

−µ

+µ



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Tire Dynamics Tire Dynamics -- Stick FrictionStick Friction

Problem : Dugoff model does not incorporate stick frictionSolution : Introduce additional friction component, based on

Fuzzy logic supervisory control.

M

1

s

1

s

1

Friction

Spring



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Tire Stick Friction ModelTire Stick Friction Model

( ) ( )

+

−+−

=0

1

,,

,,

yvstickyvstick

wxvstickwxvstick

St uKvD

uus

KvvD

FStick Friction Force:



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Tire Model Tire Model -- Fuzzy SwitchFuzzy Switch

0λ− λvw vv −=δ



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Tire Dynamics ModelTire Dynamics Model



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Hardware Im plementationHardware Im plementation

Simulation Platform Integrated Network Environment (SPINE)



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Modularit y Modularit y -- MultiMulti --CPUCPU

SPINE is the communication backbone for the VVSS. The simulation software for each module communicates through a DLL with the VVSS. The VVSS serves a pool of shared memory to the modules through SPINE.



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Modularit y Modularit y -- State Indexin gState Indexin g

( )

( )

( )n

i

1

xL

xL

xL

ix&

ix 1~i

x 2~i

x

Implicit Bilinear Approximation:

( )

( )kkkk

kkkk

kkk

xxh

cxx

xxh

bxx

ahuxx

,21,2,31,3

,11,1,21,2

,11,1

2

2&&&

&&&

&

++=

++=

+=

++

++

+



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kkkkk

kkk

kkk

uh

abcxh

bcxchxx

uh

abxbhxx

ahuxx

k

42

2~

3

,1

2

,2,31,3

2

,1,21

,11,1

1,2

+++=

++=

+=

+

+

+

&&&

&&

&

Modularit y Modularit y -- IntegrationIntegration

Implicit Bilinear Approximation:

Explicit Bilinear Approximation:

s

a

s

b

s

c

Forward Euler Approximation:

kkk

kk

kkk

xchxx

xbhxx

ahuxx

k

,2,31,3

,1,21

,11,1

1,2

~

&&

&&

&

+=

+=

+=

+

+

+

kht =At Some:u

1x12

~x 3x

( )

( )kkkk

kkk

kkk

xxh

cxx

xxh

bxx

ahuxx

k

,21,2,31,3

,11,1,21

,11,1

2

2~

1,2

&&&

&&&

&

++=

++=

+=

++

+

+

+



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Modularit y Modularit y -- Timin gTimin g

of a subsystem

of a subsystem



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Real time Real time -- Simulation timeSimulation time

n

ntth s

s

+> 0

fs Tntt <+0

Time to compute overhead and n integration steps must be smaller than frame size:

The time that is simulated per framemust match the real time laps of the frame:

n

Th f

s =

The minimum sub-sample integration time must meet the requirement:



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Real timin gReal timin g



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Implementation in MATLABImplementation in MATLAB



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Real Timin gReal Timin g



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Driver EnvironmentDriver Environment



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ConclusionsConclusions

Developed a Vehicle Simulation Environment (VVSS) and a real-time based simulation network (SPINE).

Facilitate a plug-and-play ready to use simulation environment in familiar popular Matlab/Simulink

Fully interactive audio/motion feedback stereo-vision human driver environment

Easily configure any driving scenario and terrain configuration through separate datafile

Still unsolved problem for P&P calibration ...



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Virtual Vehicle Virtual Vehicle Systems SimulationSystems Simulation

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Fine.Fine.



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Systems En gineerin gSystems En gineerin g

=QdX

CSYU^SU

5^WY^UUbY^W

DUSX^_\_Wi

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