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Automotive NVH Research Instrumentation and
Infrastructure at UC-SDRL
Teik C. Lim, Jay Kim, Randall AllemangStructural Dynamics Research Laboratory
Mechanical, Industrial & Nuclear EngineeringUniversity of Cincinnati
2003-01-1689
Long-term Objectives
Integrated experimental, analytical & computational research laboratoriesyDrivetrain and propulsion noise & vibrationsy Vehicle system dynamics and controlyNVH and acoustic noise quality
Discovery, research and education-centered facilityy Training of next generation engineersy Partnerships with industry and governmenty Conception & deployment of new technologies
(new challenges: wider use of alternative fuels/systems)
2003-01-1689
Research Focus
Nonlinear response/stability
FEM/modal analysis
Drivetrain Systems(Gears, Bearings, Trans., Engines)
Active control / smart systems
Study of forces/motions
Noise/Noise/VibVibControlControl
Jury Evaluation / statistical models
NVH & Sound Quality(Actuators, Brakes, Rotating Machines)
Audio-visual simulations
Target setting
Vibro-acoustic design/analysis
Signal analysis
Vehicle Structures(Body, Chassis, Interior Acoustics)
Noise path analysis
Hybrid models
Spectral techniques
Structure-borne contributions
2003-01-1689
Major Research Infrastructure4-axis nonlinear road simulatorAdvanced modal/spectral analysisGear dynamics/acoustics
Anechoic chamberAcoustic noise quality studioComputational Vibro-acoustics
ClutchCoupling
TestGearbox
Slave Gearboxfor Torque Application
Torque & Speed Transducers
DriveMotor
12 in.
Isolating Belt/Pulleys
Test Foundation
ClutchCoupling
TestGearbox
Slave Gearboxfor Torque Application
Torque & Speed Transducers
DriveMotor
12 in.12 in.
Isolating Belt/Pulleys
Test Foundation
2003-01-1689
4-Axis Road Simulator
MTS Series 320
Application Areas:Squeak & RattleNonlinear ResponseRide quality
Software:MTS IdeasLMSMatlab
Computers:HP-UX workstationsWindows NT/2000
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)
2003-01-1689
InversionInversion{{xxcc}=[}=[HHcc]{]{ffcc}}
Frequency-dependent Nonlinear Algebraic Solutions(express free sub-structure FRFs in term of system response)
Free subFree sub--structure Bstructure B{{ffcc}=[D}=[DBB]{]{xxcc}}
Free subFree sub--structure Astructure A{{ffcc}=[D}=[DAA]{]{xxcc}}
{Rc(a)} {Rc(b)}
{fc(a)} {fc(b)}{fi(a)} {fi(b)}
{xo(a)} {xc(a)} {xc(b)} {xo(b)}[K]
( )( )
2)b(c)a(c,s)b(c)b(c,s)a(c)a(c,s
)b(c)a(c,s
)a(c)a(c,s)b(c)a(c,s)b(c)b(c,s
)a(c)a(o,s2
)b(c)a(c,s)b(c)b(c,s)a(c)a(c,s)a(c)a(o
HHH
HK
HHHHHHH
H
−=
−
−=
One-dimensional case
Inverse Sub-structuring (Spectral Domain)
2003-01-1689
Modal Hammer
Spindle excitation test
Air mount support
VXI frontend
Test vehicle
Data AcquisitionSystem
Accelerometer
Impact hammer
c(a)
c(b)
mic, o(a)
accelo(a)
i(b)
mount
sub-structure A
sub-structure B
Vehicle Structure (Chassis Force Transmissibility)
Road Noise/Vib
Frame/suspension dynamics(Transmissibility and
Resonance Effects)
Spindle Loads
Chassis forceinput to body
Body structural-acousticSensitivity response
Tire patchexcitation
2003-01-1689
50 100 150 200 250 300 350 4000
5
10
15
20
Frequency (Hz)
Stiff
ness
(kN
/mm
)
Predicted
Measured (Elastomeric test)
Rear left mount stiffness Driver's ear SPL due to spindle force
Frequency (Hz)
Soun
d Pr
essu
re (d
B) Predicted
Measured
50 100 150 200 250 300 350 400
20
40
60
80
Method to dissect system response into free sub-structure characteristicsModular viewpoint to study dynamic response of complex structuresReadily provides force transmissibility and path contribution functions
Vehicle Structure (Validation Results)
2003-01-1689
Crank Rumble (Nature of Problem)
Rumble contains several modulated, constant, narrow-band signals
Spectrogram Function(time-frequency analysis)
Ramp-up Ramp-down Neutral no-load
snap test
Transient, rough sound due to combustion-induced crankshaft vibrationMost severe in 4-cylinder, manual transmission powertrainsCorrelation between the annoyance level and main journal clearance
2003-01-1689
Specific loudness & moving average filters
Engine rpm
15
20
25
2100 2200 2300 2400 2500 2600 2700 2800M
odul
atio
n Fr
eq (H
z) Frequency band: 870 – 950 Hz
slope = p/60p=0.5
(half-order effect)rumble period
Time scale
SPL
Half-order effect implies sensitivity to a specific cyl. or main journal brg.Speed-invariant frequencies suggest effects of structural modes.
Periodicity of Rumble (Engine speed effect)
2003-01-1689
Sound Quality Playback System
DAT Recorder
Input SignalsNo-load snap2nd gear rampRandom noise
Baffled Speaker
Mic
TL
Rumble Transmission (Simulated Air-borne)
Operating Data
Simulated Data
Bark 8770-920 Hz
Structure-borne dominance
Operating Data
Simulated Data
Bark 101080-1270 Hz
Air-borne dominance
Specific Loudness Reduction
Same effect for Barks 5 thru 7(400-510, 510-630, 630-770 Hz)
2003-01-1689
Damping Identification (Hybrid Modeling)
Direct damping identification from measured dynamic stiffness matrixImaginary([H(ω)]-1) = [C(ω)]Represent true loss mechanism & spatial distribution in freq. domainUse with analytical mass and stiffness matrices to form a hybrid model
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
0 1000-10
-5
0
5
x 109
Freq (Hz)
0 1000
-2
-1
0
1
2
x 109
Freq (Hz)
Typical results:Diagonal elements of experimentally identified damping matrix
Real
Imag
2003-01-1689
Sound Transmission (Anechoic Facility)
101
102
103
104
-10
0
10
20
30
40
50
Fre que ncy (Hz)
TL (d
B)
C a lcula te dMe a s ure d
Cylindrical structure
101
102
103
104
0
5
10
15
20
25
30
35
40
Fre que ncy (Hz)
TL (d
B)
W/ S tiffe ne r W/O S tiffe ne r
101
102
103
104
20
30
40
50
60
70
80
90
100
Fre que ncy (Hz)
TL (d
B)
W/O s tiffe ne rW/ s tiffe ne r
Cylindrical-stiffenedFlat-stiffened
2003-01-1689
Concluding Remarks
New challenges requiring integrated test & analysis facility for research, education and servicesyNonlinear & time-varying problemsyMore stringent NVH requirementsy Combined design & NVH analysis/testing approachy Alternative vehicle, propulsion and fuel systems
Center for discovery, research and educationyRepository for basic and applied NVH technologiesy Partnerships between academia, industry and govt.y Combined research & education activities
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