set up of an automotive test rig in simpack

Volker Sing, Idriz Krajcin, DaimlerChrysler-AG, Analysis Commercial Vehicles, PBE/DAD

Set up of an Automotive Test Rig inSIMPACK

Analysis Commercial Vehicles, PBE/DAD

PBE/DAD - DC-POS A4 W 2001-10-24 Page 1 Analysis Commercial Vehicles

Overview

� 1. Introduction� Durability Testing� Calculation of Cutting Forces� Problem Clarification

� 2. Set Up of the Virtual Test Rig

� 3. Parameter Variation

� 4. Results

� 5. Outlook


Durability Testing

� Proving Ground Test

� Hydraulic Test Rig


Calculationof Cutting Forces

Excitation at the tire contactpoint by the road profile

(Displacement Excitation)

Vehicle M

odel

Axle

Chassis

FEMFatigue Analysis

Excitation forHydraulic Test Rig

Cutting Forces(Time Domain)

Cutting Forces(Time Domain)

Excitation at the centreof the wheel by

wheel hub forces(Force Excitation)


SIMPACK-Modell of the Vaneo

Model drifts after a short time�

SIMPACK model excited with wheel hub forceswithout feedback control


Causes of Drift:� Inaccuracies in the wheel hub forces

� Missing initial states (position, velocity, acceleration)

� Inaccuracies in the model parameters (mass, inertia, stiffness,damping)

Stabilization Methods:� Restraining the vehicle body using spring and damper elements

� Vehicle stabilization using feedback control (control input: Positionof the car body)


Control Layout

β

2 FREG

2 FREG

R

0222 23 =⋅⋅+⋅⋅⋅+⋅⋅⋅+YY

IR

YY

PR

YY

DRJ

cRsJ

cRsJ

cRschar. polynomial:

REGYY FRdtdJ ⋅⋅⋅−=⋅ )cos(22

2ββ

conservation of angular momentum:

� ⋅+⋅+⋅= βββdtdccdtcF DRPRIRREG control law (PID-control):

�

Position of vehicle body for control input


321 and , λλλ

Eigenvalues in the s-plane: 1λ

ϕ

σ

ωj

0ω

2λ

3λ

Choice of eigenvalues:

D=0,71

natural frequency: 22,1

22,10 )Im()Re(2 λλπω +=⋅= f

with cos( )=Dϕ Re( )=Im( )2,1λ 2,1λ�

Eigenvalues:


Restraining the Vehicle Body with Spring andDamper Elements:

)(2

2z

dtddzcz

dtdmF ⋅+⋅−=⋅

)(2

2ααα

dtddc

dtdJ DrehDrehXX ⋅+⋅−=⋅

Translation:

Rotation:

� Coupling of the vehicle body to a stationary reference system

� The spring and damper elements are attached to the c.g. of thevehicle body.


PositionEncoder

Accelerometer

� Vertical hub acceleration of the right hand side (az_VA_r,az_HA_r)

� Distance between wheel and vehicle body (sz_VA_r, sz_VA_l,sz_Ha_r, sz_HA_l)

Reference Measurements (empirical Data)


Reference Measurements (empirical Data)� Vehicle accelerations

(ax_AUF_vor, ay_AUF_vor, az_AUF_vor, ay_AUF_hro,az_AUF_hro)

D-Pillar A-Pillar

Accelerometer AUF_hroAccelerometer AUF_vor


Quality Criteria:Standard deviation of the difference between the measuredand simulated data

� Variation by a batch file(*.bat). The variables in the parameter fileare changed. A SIMPACK simulation is carried out and the qualitycriteria are stored in a result file.

� Variation of the real part of the eigenvalue and

� 15 seconds realtime simulation

Standard deviation for n function values xi:

1λ 3λ

��==

=��

��

� −−

=n

j

n

ii x

nxxx

ns

1j1

2 1 with)(1

1

Parameter Variation


74,03 −=λi9,19,12 −−=λ

equivalent to 0,43 Hz

22

23

24

25

26

27

28

-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2

-2,2-2,1-2,0-1,9-1,8-1,7

74,0)Re( 3 −=λ

][ 2sm

:)Re( 1λQuality Criteria

3λRe( )2350=IRc

4464=DRc2020=PRc�

Results of the Parameter Variation� Feedback control delivers a better overall result

� Choice of control parameters for the example of the accelerationaz_VA_r:

i9,19,11 +−=λChosen eigenvalues:


Results of the Quality Criteria of the x-Axis Rotation

13579

1113151719

-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2

-2,2-2,1-2,0-1,9-1,8-1,7

:)Re( 1λ

][°

3λRe( )

Quality Criteria


without feedbackcontrol

�Model drifts

with feedback control� no drift

SIMPACK- Model excited by Wheel Forces


Comparison of the relativedisplacement sz_VA_r

sz_VA_r[mm]

time [s]sz_VA_r

[mm]

frequency [Hz]

Fast-Fourier-Transformationof the signals

Results

-100-80-60-40-20

020406080

100

4 5 6 7 8

simuliertgemessenSimulationMeasurement

0

5

10

15

20

0 5 10 15 20 25

simuliertgemessenSimulationMeasurement


Level crossing counting(30 classes)

Range pair counting(30 classes)

Results

020406080

100120140160

0 50 100 150 200

simuliertgemessen

cumulative cycle count

sz_VA_r[mm]

SimulationMeasurement

-80-60-40-20

020406080

0 20 40 60 80 100 120

simuliertgemessensz_VA_r

[mm]

rate of level crossings

SimulationMeasurement


3D measured proving ground surface (Africa):

Simulation with RMOD-K:

Modelling of the elastic vehicle body

Outlook

set up of an automotive test rig in simpack

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