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

4-Axis Road Simulator (Results)

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