set up of an automotive test rig in simpack
TRANSCRIPT
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
PBE/DAD - DC-POS A4 W 2001-10-24 Page 2 Analysis Commercial Vehicles
Durability Testing
� Proving Ground Test
� Hydraulic Test Rig
PBE/DAD - DC-POS A4 W 2001-10-24 Page 3 Analysis Commercial Vehicles
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)
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SIMPACK-Modell of the Vaneo
Model drifts after a short time�
SIMPACK model excited with wheel hub forceswithout feedback control
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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)
PBE/DAD - DC-POS A4 W 2001-10-24 Page 6 Analysis Commercial Vehicles
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
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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:
PBE/DAD - DC-POS A4 W 2001-10-24 Page 8 Analysis Commercial Vehicles
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.
PBE/DAD - DC-POS A4 W 2001-10-24 Page 9 Analysis Commercial Vehicles
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)
PBE/DAD - DC-POS A4 W 2001-10-24 Page 10 Analysis Commercial Vehicles
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
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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
PBE/DAD - DC-POS A4 W 2001-10-24 Page 12 Analysis Commercial Vehicles
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:
PBE/DAD - DC-POS A4 W 2001-10-24 Page 13 Analysis Commercial Vehicles
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
PBE/DAD - DC-POS A4 W 2001-10-24 Page 14 Analysis Commercial Vehicles
without feedbackcontrol
�Model drifts
with feedback control� no drift
SIMPACK- Model excited by Wheel Forces
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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
PBE/DAD - DC-POS A4 W 2001-10-24 Page 16 Analysis Commercial Vehicles
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
PBE/DAD - DC-POS A4 W 2001-10-24 Page 17 Analysis Commercial Vehicles
3D measured proving ground surface (Africa):
Simulation with RMOD-K:
Modelling of the elastic vehicle body
Outlook