Automotive NVH Research
Instrumentation and
Infrastructure at UC-SDRL
Teik C. Lim, Jay Kim, Randall Allemang
Structural Dynamics Research Laboratory
Mechanical, Industrial & Nuclear Engineering
University of Cincinnati
Long-term Objectives
Integrated experimental, analytical & computational
research laboratories
y Drivetrain
and propulsion noise & vibrations
y Vehicle system dynamics and control
y NVH and acoustic noise quality
Discovery, research and education-centered facility
y Training
of next generation engineers
y Partnerships with industry and government
y Conception & deployment of new technologies
(new challenges: wider use of alternative fuels/systems)
2003-01-1689
Research Focus
FEM/modal
analysis
Study of
forces/motions
Spectral
techniques
Vehicle Structures
Drivetrain Systems
(Body, Chassis, Interior Acoustics)
(Gears, Bearings, Trans., Engines)
Nonlinear
response/stability
Active control
/ smart systems
Vibro-acoustic
design/analysis
Noise path
analysis
Noise/Vib
Control
Hybrid
models
Structure-borne
contributions
NVH & Sound Quality
Audio-visual
simulations
(Actuators, Brakes, Rotating Machines)
Jury Evaluation /
statistical models
Signal analysis
Target setting
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Major Research Infrastructure
4-axis nonlinear road simulator
Advanced modal/spectral analysis
Gear dynamics/acoustics
Isolating Belt/Pulleys
Drive
Motor
Clutch
Coupling
Test
Gearbox
Torque & Speed
Transducers
tion
nda
u
o
st F
Te
Slave Gearbox
for Torque Application
12 in.
Anechoic chamber
Acoustic noise quality studio
Computational Vibro-acoustics
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4-Axis Road Simulator
Application Areas:
Squeak & Rattle
Nonlinear Response
Ride quality
Software:
MTS Ideas
LMS
Matlab
MTS Series 320
Data Acquisition Equipment:
HP-356X Modules
224-ch (12.5 kHz) & 24-ch (25 kHz)
HP-VXI Modules
96-ch (25 kHz)
Larsen Davis Network System
64-ch (2500 Hz)
Computers:
HP-UX workstations
Windows NT/2000
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4-Axis Road Simulator (Results)
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Inverse Sub-structuring (Spectral Domain)
{xo(a)}
Free sub-structure A
{fc(a)}
{xo(b)}
{xc(b)}
Free sub-structure B
{Rc(b)}
{Rc(a)}
{fc}=[DA]{xc}
{fi(a)}
[K]
{xc(a)}
Inversion
{fc}=[DB]{xc}
{fi(b)}
{fc(b)}
{xc}=[Hc]{fc}
Frequency-dependent Nonlinear Algebraic Solutions
(express free sub-structure FRFs in term of system response)
H o ( a )c ( a )
(
H
=
One-dimensional case
K=
s ,c( a )c( a ) H s ,c( b )c( b )
)
− H s2,c(a )c(b ) H s ,o(a )c(a )
(H s,c(b)c(b) − H s,c(a)c(b) )H s,c(a)c(a)
H s,c(a )c(b )
H s,c(a )c(a ) H s,c(b )c(b ) − H s2,c(a )c(b )
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Vehicle Structure (Chassis Force Transmissibility)
Spindle excitation test
Data Acquisition
System
Accelerometer
Modal Hammer
Test vehicle
Air mount
support
VXI
frontend
Impact
hammer
sub-structure A
mic, o(a)
Road Noise/Vib
Body structural-acoustic
Sensitivity response
Chassis force
input to body
c(a)
Frame/suspension dynamics
(Transmissibility and
Resonance Effects)
Spindle Loads
Tire patch
excitation
accel
o(a)
mount
c(b)
i(b)
sub-structure B
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Vehicle Structure (Validation Results)
Rear left mount stiffness
Driver's ear SPL due to spindle force
Measured (Elastomeric test)
15
Predicted
10
5
0
80
Sound Pressure (dB)
Stiffness (kN/mm)
20
50
100
150 200 250 300
Frequency (Hz)
350
400
Predicted
60
Measured
40
20
50
100
150 200 250 300
Frequency (Hz)
350
400
Method to dissect system response into free sub-structure characteristics
Modular viewpoint to study dynamic response of complex structures
Readily provides force transmissibility and path contribution functions
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Crank Rumble (Nature of Problem)
Transient, rough sound due to combustion-induced crankshaft vibration
Most severe in 4-cylinder, manual transmission powertrains
Correlation between the annoyance level and main journal clearance
Ramp-up
Neutral
no-load
snap test
Ramp-down
Rumble contains several
modulated, constant,
narrow-band signals
Spectrogram Function
(time-frequency analysis)
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Periodicity of Rumble (Engine speed effect)
Specific loudness & moving average filters
SPL
Modulation Freq (Hz)
25
rumble
period
Time scale
Frequency band: 870 – 950 Hz
slope = p/60
p=0.5
(half-order effect)
20
15
2100
2200
2300
2400
2500
2600
2700
2800
Engine rpm
Half-order effect implies sensitivity to a specific cyl. or main journal brg.
Speed-invariant frequencies suggest effects of structural modes.
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Rumble Transmission (Simulated Air-borne)
Specific Loudness Reduction
Input Signals
Sound Quality
Playback System
No-load snap
2nd gear ramp
Random noise
Operating
Data
Simulated
Data
DAT Recorder
Bark 10
1080-1270 Hz
Mic
TL
Air-borne dominance
Simulated
Data
Baffled
Speaker
Same effect for Barks 5 thru 7
(400-510, 510-630, 630-770 Hz)
Bark 8
770-920 Hz
Operating
Data
Structure-borne dominance
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Damping Identification (Hybrid Modeling)
Direct damping identification from measured dynamic stiffness matrix
Imaginary([H(ω)]-1) = [C(ω)]
Represent true loss mechanism & spatial distribution in freq. domain
Use with analytical mass and stiffness matrices to form a hybrid model
x 10
9
Real
5
x 10
9
x 10
9
x 10
9
x 10
9
x 10
5
5
5
5
5
0
0
0
0
0
0
-5
-5
-5
-5
-5
-5
-10
0
1000
Fre q (Hz )
x 10
9
Imag
2
-10
0
1000
Fre q (Hz )
x 10
-10
9
0
1000
Fre q (Hz )
x 10
-10
9
0
1000
Fre q (Hz )
x 10
-10
9
0
1000
Fre q (Hz )
x 10
-10
9
2
2
2
2
1
1
1
1
1
1
0
0
0
0
0
0
-1
-1
-1
-1
-1
-1
-2
-2
-2
-2
-2
-2
1000
Fre q (Hz )
0
1000
Fre q (Hz )
0
1000
Fre q (Hz )
0
1000
Fre q (Hz )
0
1000
Fre q (Hz )
1000
Fre q (Hz )
x 10
2
0
0
0
9
Typical results:
Diagonal elements
of experimentally
identified damping
matrix
9
1000
Fre q (Hz )
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Sound Transmission (Anechoic Facility)
50
C a lcula te d
Me a s ure d
40
TL (dB)
30
20
10
0
Cylindrical structure
40
35
-1 0
1
10
Flat-stiffened
100
W/ S tiffe ne r
W/O S tiffe ne r
10
3
10
4
Cylindrical-stiffened
W/O s tiffe ne r
W/ s tiffe ne r
90
80
25
70
TL (dB)
TL (dB)
2
F re que ncy (Hz)
30
20
60
15
50
10
40
5
30
0
1
10
10
10
2
10
F re que ncy (Hz)
3
10
4
20
1
10
10
2
10
3
10
4
F re que ncy (Hz)
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Concluding Remarks
New challenges requiring integrated test & analysis
facility for research, education and services
y Nonlinear
& time-varying problems
y More stringent NVH requirements
y Combined design & NVH analysis/testing approach
y Alternative vehicle, propulsion and fuel systems
Center for discovery, research and education
y Repository
for basic and applied NVH technologies
y Partnerships between academia, industry and govt.
y Combined research & education activities
2003-01-1689
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