1、Overview of NVH,Vehicle Dynamics,NVH,Durability,Crashworthiness,Vehicle Attributes,Weight$,Noise : Vibration perceived audibly and characterized as sensations of pressure by the earVibration : Perceived tactually at vehicle occupant interface points of steering column, seats, etc.Harshness : Related
2、 to transient nature of vibration and noise associated with abrupt transition in vehicle motion. It could be perceived both tactually and audibly,What is N, V, and H,Time Vs. Frequency Domains,Acoustic TactileTactile,ExcitationsExcitations,Excitations,Time (Sec),Tactile or Acoustic Response,Response
3、s vary with time as vehicle operates under loadsResponses are usually steady state and periodic in natureIt is convenient to consider responses in frequency domain while preserving the signal content,Time Vs. Frequency Domains,Frequency (Hz),5 Hz,(Vehicle Rigid,Body Mode),15 Hz,(Suspension,Mode),25
4、Hz,(Vehicle Flexible,Body Mode),40 Hz,(Column,Mode),Overall Response, X(t),Time (Sec),Phased Summation,X(f),Time Vs. Frequency Domains,X ( f ) = Fourier Transform of X ( t ),Time Vs. Frequency Domains,F ( t )X ( t )Vehicle System,Fourier Transform,X ( f ),Testing,X ( f ),CAE Simulation,Vehicle Syste
5、m,F ( f ),Fourier Transform,Total 2178.2 Kg,(4800LBS),Mass,Sprung Unsprung Powertrain,1996.7 Kg181.5 Kg181.5 Kg,(8.33% of Total),Tires KF KR,350.343.863.1,N/mm N/mm N /mm,Beam mass lumped on grids like a beam M2,3,4 =2 * M1,5,3,1,8,2,6,4,7,5,Model of Uni-body Vehicle,Profile of Excitation Bum p,0.0,
6、5.0,10.0,15.0,20.0,0,100,200300Distance(mm),Profile Height,(m m ),400 On to 100,380,Profile,Response in Time Domain,1.0E-048.0E-056.0E-054.0E-052.0E-050.0E+00-2.0E-05-4.0E-05-6.0E-05-8.0E-05-1.0E-04,0,1,2,3,Time (sec.),R o ta ti o n,- R a d ia n s,Base Model,Response in Frequency Domain,1.E-08,1.E-0
7、7,1.E-06,1.E-05,1.E-04,0.0,5.0,10.0FrequencyHz,15.0,20.0,Ro tat io n Ra d ian s,Base Model,Hz 45 MPH4.E-038.E-031.E-022.E-022.E-02Cycles / mm,FFT of the Input Bump,1.E-06,1.E-05,1.E-04,1.E-03,1.E-01Bump FFT1.E-02,0.E+00,Amplitude,mm,Input Force in Frequency Domain,20,0.0,20.0 Hz,1 .0 E-0 8,1 .0 E-0
8、7,1 .0 E-0 6,1 .0 E-0 5,1 .0 E-0 4,0,510 F re qu e n c yH z,15,20,Ro tatio n Rad ian s,Tim e D o m a in F F T,FFT o f In p u t,Subjective to Objective Conversions,Subjective NVH Ratings are typically based on a 10 Point Scale resulting from Ride TestingReceiver Sensitivity is a Key ConsiderationA2 1
9、/2A 1Represents 1.0 Rating ChangeTACTILE:50% reduction in motionSOUND:6.dB reduction in sound pressure level,m,APPLIED FORCEF = FO sin 2 f t,k,c,Transmitted ForceFT,TR = FT / F,Single Degree of Freedom Vibration,=,f 2fn 2,) 2,1 + ( 2 d f,fn,) 2,( 1-,+ ( 2 d f,fn,) 2,d = fraction of critical damping
10、fn = natural frequency (k/m) f = operating frequency,0,11.41423,4,5,0,Transmissibility Ratio,Frequency Ratio (f / fn),0.51.01Isolation Region,2,3,4,0.1,0.15,0.375,0.25,Vibration Isolation,m,APPLIED FORCEF = FO sin 2 f t,k,c,FT,TR = FT / F,Transmitted Force,Isolation Region,Excitation Force Coming fr
11、om Engine,F0,FT,Transmissibility Force Ratio is FT/F0,Isolation from an Applied Force,Support Forces Transmitted to Body,Example:A 4 Cyl. Excitation for Firing Pulse at 700 RPM has a second order gas pressure torque at23.3 Hz.Thus, to obtain isolation, the engine roll mode must be below 16.6 Hz.,Str
12、ucture Borne NoiseAirborne Noise,Response,Log Frequency,“Low”,Global Stiffness,“Mid”,Local Stiffness,+Damping,“High”,AbsorptionMass+Sealing, 150 Hz, 1000 Hz, 10,000 Hz,Automotive NVH Frequency Range,Sources of Noise and Vibration,Suspension,Powertrain,NVH Pathways to the Passenger,PATHS FORSTRUCTURE
13、 BORNENVH,Powertrain Induced,RECEIVER,PATHSOURCE,Low Frequency NVH,Attenuation Approaches,Attenuation StrategiesReduce the Input Forces from the SourceProvide IsolationModal ManagementNodal Point MountingDynamic Absorbers,8 DOF Vehicle NVH Model,1,2,4,5,6,7,8,3,Suspension SpringsWheels Tires,Engine
14、Mass,Engine Isolator,Flexible Beam for Body,Reduction of Input Forces from the Source,Road ExcitationUse Bigger / Softer TiresReduce Tire Force VariationDrive on Smoother RoadsPowertrain ExcitationReduce Driveshaft Unbalance ToleranceUse a Smaller Output EngineMove Idle Speed to Avoid Excitation Ali
15、gnmentModify Reciprocating Imbalance to alter Amplitude or Plane of Action of the Force.,Vibration and Noise Attenuation Methods,Main Attenuation StrategiesReduce the Input Forces from the SourceProvide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers,8 Degree of Freedom Vehicl
16、eNVH Model,Force Applied to Powertrain AssemblyFeng8,Powertrain Excitation (First Order Rotating Imbalance),1,2,4,5,6,7,3,Engine Isolation,Response at Point 3,0.0001,0.0010,0.0100,0.1000,1.0000,5.0,10.0,15.0,20.0,FrequencyHz,Velocity (mm/sec),Constant Force Load; F A,15.9 Hz,8.5 Hz,7.0 Hz,700 Min. R
17、PM First Order Unbalance Operation Range of Interest,Increased Isolation,Second Level of Isolation is at Subframe to Body MountSubframe is Intermediate StructureSuspension Bushing is first level,8 DOF Vehicle NVH ModelRemoved Double Isolation Effect,1,2,4,5,6,7,8,3,Wheel Mass Removed,Double Isolatio
18、n Example,Vertical Response at DOF3,20.0,Velocity,(mm/sec),6.0E+00Base Model5.0E+00Without Double_ISO4.0E+003.0E+001.414*fn2.0E+001.0E+000.0E+00,5.0,10.015.0FrequencyHz,Vibration and Noise Attenuation Methods,Main Attenuation StrategiesReduce the Input Forces from the SourceProvide IsolationMode Man
19、agementNodal Point MountingDynamic Absorbers,Modal Alignment,Provide Separation between:Critical modes of Sub-systems in Vehicle (e.g. Body, Suspension, Powertrain, etc.)Critical modes of Sub-systems and Excitation,1,2,Baseline Suspension10.6 HzFlexible Beam for Body345,6,7,8,Beam Stiffness which re
20、presents the body stiffness was adjusted to align Bending Frequency with Suspension Modes and then progressively separated back to Baseline.Baseline Bending18.2 Hz,Modal Alignment,Suspension SpringsWheels Tires,8 DOF Mode Separation Example,Response at Mid Car,Suspension Mode0.10,1.00,10.00,100.00,5
21、,10FrequencyHz,15,20,Velocity (mm/sec),18.2 Hz Bending,13.Hz Bending,18.2 Hz,13.0 Hz,10.6 Bending10.6 Hz,Progressive reduction in the,“vehicle” bending mode,Modal Alignment Chart,EXCITATION SOURCESInherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.) Process Variati
22、on Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances)05101520253035404550First Order Wheel/Tire UnbalanceV8 IdleHzHot - ColdCHASSIS/POWERTRAIN MODESSuspension Hop and Tramp Modes,Hz,Exhaust Modes4550Hz,Ride Modes05,Powertrain Modes1015,Suspension Longitudinal Modes20253035,40,0,Body F
23、irst Bending51015(See Ref. 1),NVH Workshop,20,25,30,First Acoustic Mode354045,50,BODY/ACOUSTIC MODES,Steering Column First Vertical Bending,Body First Torsion,Campbell Diagram,Frequency (Hz),Engine RPM,1st Harmonic,2nd Harmonic,3rd Harmonic,Global Body Torsion,Steering Column Vertical,30Hz,32Hz,600
24、RPM,Campbell Diagram simultaneously represents excitations and vehicle system modes on a RPM vs. Frequency axis systemA more convenient way (compared to mode management charts) of understanding the interaction among modes and excitation and mapping onto ERPM and vehicle speed,Vibration and Noise Att
25、enuation Methods,Main Attenuation StrategiesReduce the Input Forces from the SourceProvide IsolationMode ManagementNodal Point MountingDynamic Absorbers,Front input forces,Rear input forces,MountatNodalPointFirst Bending: Nodal Point Mounting Example,Locate wheel centers at node points of the first
26、bending modeshape to prevent excitation coming from suspension input motion.,MountatNodalPointNodal Point Mounting Examples,Transmission Mount of a 3 Mount N-S P/T is near the Torsion Node.,Rear View,Engine,1,2,6,7,Mount system is placed to support Powertrain at the Nodal Locations of the First orde
27、r Bending Mode.345,Passenger sits at node point for First Torsion.,8 Degree of Freedom Vehicle NVH Model,Bending Node Alignment with Wheel Centers,1,2,4,5,6,7,8,3,Redistribute Beam Masses to move Node Points to Align with points 2 and 4,Response at Mid-Car,0.0E+00,1.0E+00,2.0E+00,4.0E+00Node Shifted
28、 Base Model3.0E+00,5.0,10.015.0FrequencyHz,20.0,Velocity,(m m /sec),First Bending Nodal Point Alignment,Vibration and Noise Attenuation Methods,Main Attenuation StrategiesReduce the Input Forces from the SourceProvide IsolationMode ManagementNodal Point MountingDynamic Absorbers,3.53.02.52.01.51.00.
29、50.0,4.0,0.0,0.5,1.0Frequency Hz,1.5,2.0,Displacement,mm,YO,x,SDOF,Dynamic Absorber Concept,M,YO,x,Auxiliary Spring-Mass-Damper,m = M / 10,2DOF,M,Powertrain Example of Dynamic Absorber,Anti-Node Identified at end of Powerplant,k,c,mAbsorber attached at anti-node acting in the Vertical and Lateral pl
30、ane.,Tuning Frequency =, k/m,Baseline Sound Level63 Hz Dynamic Absorber 63 + 110 Hz Absorbers,Baseline Sound Level63 Hz Dynamic Absorber63 + 110 Hz Absorbers,Vibration and Noise Attenuation Methods,Main Attenuation StrategiesReduce the Input Forces from the SourceProvide IsolationMode ManagementNoda
31、l Point MountingDynamic AbsorbersThe above attenuation concepts have been demonstrated using simulation model results.A similar demonstration using physical hardware would have required more cost and time. Hardware testing in low frequency range could be used as a final verification tool,RECEIVER,PA
32、THSOURCEThis looks familiar!Frequency Range of Interest has changed to 150 Hz to 500 Hz,Mid Frequency NVH Fundamentals,Typical NVH Pathways to the Passenger,PATHS FORSTRUCTUREBORNE NVH,Noise Paths are the same as Low Frequency Region,Noise Paths are the same as Low Frequency Region,Mid-Frequency Analysis Character,Structure Borne Noise,Airborne Noise,Response,Log Frequency,“Low”,Global Stiffness,“Mid”,Local Stiffness+Damping,“High”,Absorption+Mass+Sealing, 150 Hz,
