Virtual Testing and Subjective Evaluation of Chassis ... · •Driving Simulator process for...

IVK – Institut für Verbrennungsmotoren und

Kraftfahrwesen

Virtual Testing and Subjective Evaluation of

Chassis Components in theStuttgart Driving Simulator

IPG Apply & Innovate, Karlsruhe

September 20 – 21, 2016

Dipl.-Ing. Minh-Tri Nguyen

I. Motivation and Purpose

II. Principle of Driving Dynamics Evaluation in the Simulator

III. Implementation of the Driving Scenario

IV. Human’s Perception of Vehicle Motion

V. Evaluation of Chassis Components

VI. Summary

9/21/2016University of Stuttgart 2

Overview

Motivation and Purpose

I.

• Integration of the driving simulator in the process of chassis development

and driving dynamics

Vision: Holistic approach for vehicle development



Stuttgart

Driving

Simulator

Vehicle

Aeroacoustics

Wind Tunnel

IVK Driving

Dynamics

Test Bench

• Improving system understanding in early stages of the development

process by subjective evaluation



Definition,

Concept Simulation

Prototype Building,

ValidationTuning,

Optimization

SOPSubjective

Evaluation

Objective

Data

TestingSimulation

http://www.autoplenum.de/Auto/Testberichte/bild-id109504

• Approach for driving dynamics evaluation in the driving simulator



Use Case,

Benefits,

Limits.

Customized

Modeling

and

Simulation

- Subjective

driving

impression

- Comparison to

Reality

Principle of Driving Dynamics Evaluation in the Simulator

II.

• Common process for subjective and objective evaluation of driving

dynamics



δ

ψ, ϑ, φ, …

Driver’s r

ea

ctio

n

Ve

hic

le’s

rea

ctio

n

Disturbances

Driver

Vehicle

Subj. Evaluation

Obj. Data

Correlation subj.- obj.

?

http://www.autoplenum.de/Auto/Testberichte/bild-id109504

• Driving Simulator process for subjective evaluation of driving dynamics



δ

Ψ‘, ϑ‘, φ‘

Disturbances

Driver

SimulatorModel Motion Cueing

On/Off

Ψmod, ϑmod, φmodModel’s reaction

Driver’s r

ea

ctio

n

Sim

ula

tor’s

rea

ctio

n

Subj. Evaluation

Correlation subj.- obj.

Implementation of the Driving Scenario

III.


Requirements for the Vehicle Model


Co

mp

uti

ng

Tim

e

Subjective improvement

due to model complexity

Limit of

Real Time

Capability

Accuracy of Modeling

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCIiP-rvj9sgCFQaWDgodSl4B3Q&url=http://www.techniklexikon.net/d/hysterese/hysterese.htm&psig=AFQjCNHb-cicyF_C-heR_J5bjl1PhcUChw&ust=1446726770372466


IPG CarMaker Vehicle Model for Driving Dynamics Evaluation


Parameterized

MF 5.2

Suspension Elements

Kin./ Elakin. (.skc)

Pfeffer Steering

0,0

0,2

0,4

0,6

-15,0 -5,0 5,0 15,0

Aerodynamic Coeff.

5-Mass Model

With Rigid Body

-30 -20 -10 0 10 20 30-1000

-500

0

500

1000

1500

2000Force-distance-graph damper

Da

mp

er

forc

e [

N]

Displacement x0 [mm]-1.5 -1 -0.5 0 0.5 1 1.5

-1000

-500

0

500

1000

1500

2000Force-velocity-graph damper

Da

mp

er

forc

e [

N]

Velocity v0 [m/s]-30 -20 -10 0 10 20 30

-1000

-500

0

500

1000

1500

2000Force-distance-graph damper

Da

mp

er

forc

e [

N]

Displacement x0 [mm]-1.5 -1 -0.5 0 0.5 1 1.5

-1000

-500

0

500

1000

1500

2000Force-velocity-graph damper

Da

mp

er

forc

e [

N]

Velocity v0 [m/s]

Enhanced Damper-

Topmount-Model

• Scenario

Driving on Autobahn with road impact,

e.g. bumps, bridge joints and road unevenness


Transferring On-Road Scenario to Virtual Reality


Focus on:

Exact reproduction of

vehicle’s body motion

Subjective driving impression

comparable to reality

Autobahn Test Run

VR in the Simulator

Superposition of synthetic road spectrum and impulses on vehicle body


Structure of Excitation


10-2

100

102

104

10-20

10-10

100

Frequency [Hz]

He

ave

(f)

[m

²/H

z]

Heave Motion CG

Synthetic Road Spectrum

Excitation

Measured

Vehicle’s Motion

after Vertical

Impact

𝐹𝑥𝐹𝑦𝐹𝑧CG

Forces and

Moments

Referred to CG

𝑎𝑥𝑎𝑦

𝑎𝑧 𝜑

𝜗 𝜙

𝑀𝑥

𝑀𝑦

𝑀𝑧

0 1000 2000 3000 4000 5000-0.1

-0.05

0

0.05

0.1

Length [m]

He

ave

[m

]

Human’s Perception of Vehicle Motion

IV.

Using defined excitation to generate criteria of perception:

• General statements about the “Threshold of Perception” regarding to the

Autobahn scenario

• Evaluating the “Just Noticeable Difference” due to impulses


“Threshold of Perception” and the “Just Noticeable Difference”


DriverVirtual Vehicle Model

Excitation

Threshold of Perception

Noticeable Difference

• Experimental measuring of detected impulses

• Correlation between the intensity of impulses and the stochastic road

excitation


Driver’s Task to Evaluate the Threshold of Perception (ToP)


ToP

200 205 210 215 220 225 230-5

-4

-3

-2

-1

0

1

2

3

4

5Body's Reaction Due to Excitation

Time [s]

Vert

ical A

cc. [m

/s²]

0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.650

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

RMS of Vertical Excitation [m/s²]

Am

plitu

de Im

pu

lse [

m/s

²]

Correlation - Impulse - Excitation

Bo

dy A

cc.

in m

/s²

Time in s

RMS Vertical Road Excitation

AM

P I

mp

uls

e

Correlation AMP / RMS

𝑎𝐼𝑚𝑝 = 𝒑 ∗ 𝑎𝑟𝑜𝑎𝑑 + 𝒒

Linear correlation between impulse amplitudes and RMS of vehicle’s

vertical acceleration due to road disturbances.


Results of the ToP


0 0.2 0.4 0.6 0.8 10

1

2

3

4

5

RMS of vehicle`s vertical acc. due to road disturbance in m/s²

Am

plitu

de o

f V

ert

ical im

pacts

in

m/s

²


0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7


Am

plitu

de o

f L

on

git

ud

inal im

pacts

in

m/s

² Threshold of Perception

0 0.2 0.4 0.6 0.8 10

0.5

1

1.5

2

2.5


Am

plitu

de o

f R

ollin

g im

pacts

in

rad

/s²


0 0.2 0.4 0.6 0.8 10

1

2

3

4

5


Am

plitu

de o

f V

ert

ical im

pacts

in

m/s

²


0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7


Am

plitu

de o

f L

on

git

ud

inal im

pacts

in

m/s

² Threshold of Perception

0 0.2 0.4 0.6 0.8 10

0.5

1

1.5

2

2.5


Am

plitu

de o

f R

ollin

g im

pacts

in

rad

/s²


0 0.2 0.4 0.6 0.8 10

1

2

3

4

5


Am

plitu

de o

f V

ert

ical im

pacts

in

m/s

²


● detected

● non-detectedSeparation of

Vehicle Motion

• Experimental measuring of three impulses in a row (3AFC-Method)

• Probability of detecting a difference between two impulses


Driver’s Task to Evaluate the Just Noticeable Difference (JND)


JND

0 0.5 1 1.5 2 2.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

540 541 542 543 544 545 546 547 548 549 550-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

Bo

dy A

cc.

in m

/s²

Time in s

AMP Impulse

Pro

ba

bili

ty in

%

Psychometric Function

𝑃(𝑥) =1

1 + 𝑒𝑥−𝒄𝒔𝒂𝒔

1st 2nd 3rd

𝒂𝒔 = JND

𝒄𝒔 = x(P50%)

>

<


Results of the JND


• Fitting the psychometric function based on the probability of perceived

impulses

• Calculation the JND by evaluating the impulse intensity at the probability

of 50% and 75%

0 0.5 1 1.5 2 2.50

0.2

0.4

0.6

0.8

1

Relative Stimulus Intensity

Pro

ba

bilit

y o

f P

erc

ep

tio

n in

10

0%

Psychometric Function - Vertical Dynamics Impulse

50% JND

* measured impulse

- Fitted sigmoid fun.

75%

Evaluation of Chassis Components

V.


Comparison of Vehicle Variants by the Perception of Road Impacts


ToP and JND of vertical impulses

60 62 64 66-4

-3

-2

-1

0

1

2

3

4

Time in s

Bo

dy

Ac

c.z

in

m/s

2

60 62 64 66-4

-3

-2

-1

0

1

2

3

4

Time in s

Bo

dy

Ac

c.z

in

m/s

2


Perceptible as impulse

● Vehicle 1 (orig.)

● Vehicle 1

• + 20 % Stiffness

• + 20 % Damping


Comparison of Vehicle Variants by the Perception of Road Impacts


ToP and JND of vertical impulses

60 62 64 66-4

-3

-2

-1

0

1

2

3

4

Time in s

Bo

dy

Ac

c.z

in

m/s

2

60 62 64 66-4

-3

-2

-1

0

1

2

3

4

Time in s

Bo

dy

Ac

c.z

in

m/s

2

61.75 61.8 61.85 61.9 61.951.7

1.8

1.9

2

Time in s

Bo

dy A

cc.z

in

m/s

2

Noticeable as difference

> JND

SummaryVI.

• Improved system understanding by subjective evaluation of driving

dynamics in early stages of the development process.

• Thresholds of perceptions can be used to evaluate driving dynamics

topics to get additional objective data and better correlations.

• Compared to real on-road tests new approaches and analysis can be

implemented.

• With this simulation environment the evaluation of driving dynamics can

be more experienced.


Summary

Thank you!

e-mail

phone +49 (0) 711 685-

fax +49 (0) 711 685-

University of Stuttgart

Pfaffenwaldring 12

D-70569 Stuttgart

Dipl.-Ing. Minh-Tri Nguyen

65889

65710

IVK – Institute of Internal Combustion Engines and Automotive Engineering

[email protected]

Virtual Testing and Subjective Evaluation of Chassis ... · •Driving Simulator process for...

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