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SAE 2009 NVH Conference
           Structure Borne NVH Workshop
              Presenters:

              Alan Duncan      ...
Structure Borne NVH Workshop
           Workshop Objectives -
           1.       Review Basic Concepts of Automotive Stru...
Structure Borne NVH Workshop
           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basics...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Competing Vehicle Design Disciplines


                                  Ride         Impact
                             ...
Structure Borne Noise and Vibration


                      Vibrating
                       Source




                 F...
Automotive NVH Frequency Range

                           Structure Borne Noise
                                         ...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Structure Borne NVH Basics


                                      RECEIVER




                                  PATH



...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Single Degree of Freedom Vibration
                                        APPLIED FORCE

                                ...
Vibration Isolation Principle
                                    4
                                                      ...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
NVH Source Considerations




  Suspension
                                                               Powertrain




 ...
Typical NVH Pathways to the Passenger




                                      PATHS
                                    ...
Structure Borne NVH Sources




                                                                                Slide 18
A...
Structure Borne NVH Sources

       Primary Consideration:

       Reduce the Source first as much as
       possible beca...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Receiver Considerations
                 Subjective to Objective Conversions
         Subjective NVH Ratings are typically...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Symbolic Model of Unibody Passenger Car
                                    8 Degrees of Freedom




                     ...
8 Degree of Freedom Vehicle NVH Model
     Engine Mass
                                8
   Engine                        ...
8 Degree of Freedom Vehicle NVH Model
                       Force Applied to Powertrain Assembly
           Feng
        ...
Engine Isolation Example
                                                         Response at M id Car
                   ...
Concepts for Increased Isolation
        “Double” isolation is the typical strategy for
        further improving isolatio...
8 Degree of Freedom Vehicle NVH Model
                                Removed Double Isolation Effect

                   ...
Double Isolation Example
                                       Vertical Response at DOF3
                     6.0E+00

  ...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Mode Management Chart
  EXCITATION SOURCES
        Inherent Excitations (General Road Spectrum, Reciprocating Unbalance, G...
8 Degree of Freedom Vehicle NVH Model
                         Bending Mode Frequency Separation

                        ...
8 DOF Mode Separation Example
                                               Response at Mid Car                          ...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Mount at Nodal Point
                First Bending: Nodal Point Mounting Example




                                Front...
Mount at Nodal Point
               First Torsion: Nodal Point Mounting Examples




                                    S...
Powertrain Bending Mode Nodal Mounting



     1                          2          3                    4               ...
8 Degree of Freedom Vehicle NVH Model
              Bending Node Alignment with Wheel Centers
                            ...
First Bending Nodal Point Alignment
                                Response at Mid-Car
                4.0E+00

         ...
Low Frequency Basics
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
           • NVH S...
Dynamic Absorber Concept
                                      Auxiliary Spring-Mass-Damper
                              ...
Powertrain Example of Dynamic Absorber

             Anti-Node Identified
             at end of Powerplant




          ...
Baseline Sound Level
                       Baseline Sound Level
                      63 Hz Dynamic Absorber
            ...
Low Frequency Basics - Review
           • Source-Path-Receiver Concept
           • Single DOF System Vibration
         ...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Mid Frequency NVH Fundamentals




                          This looks familiar!
               Frequency Range of Intere...
Typical NVH Pathways to the Passenger




                                                            PATHS
              ...
Mid-Frequency Analysis Character
                         Structure Borne Noise
                                          ...
Mid-Frequency Analysis Character

            Control Measures for Mid Frequency Concerns


            Effective Isolatio...
Mid-Frequency Analysis Character

            Control Measures for Mid Frequency Concerns


            Effective Isolatio...
Isolation Effectiveness
                                           Classical SDOF: Rigid
                                 ...
Mobility
  • Mobility is the ratio of velocity response at the excitation point on structure
    where point force is appl...
Isolation
 • The isolation effectiveness can be quantified by a theoretical model based on
 analysis of mobilities of rece...
Isolation

                    Force from source with an isolator              Receiver                   Vm
       TR =
 ...
Designing Noise Paths
                                            1      1        1      1     1
                         ...
Body-to-Bushing Stiffness Ratio
                                     Relationship to Transmissibility

                   ...
Mid-Frequency Analysis Character

            Control Measures for Mid Frequency Concerns


            Effective Isolatio...
Identifying Key NVH Paths
    Key NVH paths are identified by Transfer Path Analysis (TPA)


                             ...
Designing Noise Paths
                                                                Acoustic Transfer (P/F)i
           ...
“Downstream” Effects: Body Panels
    Recall for Acoustic Response Pt
                     Pt = Σ paths [Pi ] = Σ paths [ ...
Generic Noise Path Targets
                                  Primary: Minimize the Source Force
                          ...
Final Remarks on Mid Frequency Analysis

  • Effective isolation at dominant noise paths is critical

  • Reduced mobiliti...
Structure Borne NVH: Concepts Summary
        •           Source-Path-Receiver as a system
                       1.      ...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Tool Box Demo Test Results
                                                 Toolbox Demo Noise Test Results
              ...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Real World Application Example Introduction




                                                                          ...
Quietness during Idle and Electric-Vehicle Operation


                                                        Root Cause ...
Quietness during Idle and Electric-Vehicle Operation


                                                        Root Cause ...
Engine Start Vibration


                      Root Cause Diagnostics:
                      1. Engine torque fluctuations...
Engine Start Vibration


                      Root Cause Diagnostics:
                      1. Engine torque fluctuations...
2nd Order Engine Induced Boom


       Root Cause Diagnostics:
       1. 2nd order couple of the reciprocating inertia of ...
2nd Order Engine Induced Boom


       Root Cause Diagnostics:
       1. 2nd order couple of the reciprocating inertia of ...
Engine Radiated Noise


        Root Cause Diagnostics:
        1. 24th MG2 order excitation
        2. Lower MG2 reductio...
Engine Radiated Noise


        Root Cause Diagnostics:
        1. 24th MG2 order excitation
        2. Lower MG2 reductio...
Structure Borne NVH Workshop

           • Introduction
           • Low Frequency Basics
           • Mid Frequency Basic...
Structure Borne NVH: Concepts Summary
        •           Source-Path-Receiver as a system
                       1.      ...
SAE 2009 NVH Conference
           Structure Borne NVH Workshop


                  Thank You for Your Time!

            ...
Structure Borne NVH References
     Primary References (Workshop Basis: 4 Papers)
     1. A. E. Duncan, et. al., “Understa...
Structure Borne NVH References
   Supplemental Reference Recommendations
   5. T.D. Gillespie, Fundamentals of Vehicle Dyn...
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2009 SAE Structure Borne NVH Workshop

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2009 SAE Structure Borne NVH Workshop Presentation in Chicago by Alan Duncan, Greg Goetchius, and Jianmin Guan

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2009 SAE Structure Borne NVH Workshop

  1. 1. SAE 2009 NVH Conference Structure Borne NVH Workshop Presenters: Alan Duncan Automotive Analytics Contact Email: aeduncan@autoanalytics.com Greg Goetchius Material Sciences Corp. Contact Email: greg.goetchius@matsci.com Jianmin Guan Altair Engineering Contact Email: jguan@altair.com Slide 1 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  2. 2. Structure Borne NVH Workshop Workshop Objectives - 1. Review Basic Concepts of Automotive Structure Borne Noise. 2. Propose Generic Targets. 3. Present Real World Application Example. Intended Audience – • New NVH Engineers. • “Acoustics” Engineers seeking new perspective. • “Seasoned Veterans” seeking to brush up skills. Slide 2 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  3. 3. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 3 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  4. 4. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 4 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  5. 5. Competing Vehicle Design Disciplines Ride Impact and CrashWorthiness Handling NVH Durability Slide 5 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  6. 6. Structure Borne Noise and Vibration Vibrating Source Frequency Range: up to 1000 Hz System Characterization • Source of Excitation • Transmission through Structural Paths • “Felt” as Vibration • “Heard” as Noise Slide 6 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  7. 7. Automotive NVH Frequency Range Structure Borne Noise Airborne Noise Response Absorption + Mass + Local Stiffness Sealing + + Global Stiffness Damping Damping “Low” “Mid” “High” ~ 150 Hz ~ 1000 Hz ~ 10,000 Hz Log Frequency Slide 7 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  8. 8. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 8 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  9. 9. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 9 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  10. 10. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 10 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  11. 11. Structure Borne NVH Basics RECEIVER PATH SOURCE Slide 11 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  12. 12. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 12 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  13. 13. Single Degree of Freedom Vibration APPLIED FORCE F = FO sin 2 π f t 1 + (2ζ f fn ) 2 TR = FT / F = (1 − f fn ) + (2ζ f fn ) 2 2 2 2 m Transmitted Force k c FT ζ = fraction of critical damping fn = natural frequency k m f = operating frequency Slide 13 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  14. 14. Vibration Isolation Principle 4 0.1 APPLIED FORCE Transmissibility Ratio 0.15 F = FO sin 2 π f t 3 m TR = FT / F 0.25 2 k c FT Transmitted 0.375 Force 0.5 1.0 1 Isolation Region Isolation Region 0 0 1 1.414 2 3 4 5 Frequency Ratio (f / fn) Slide 14 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  15. 15. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 15 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  16. 16. NVH Source Considerations Suspension Powertrain Two Main Sources Slide 16 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  17. 17. Typical NVH Pathways to the Passenger PATHS FOR STRUCTURE BORNE NVH Slide 17 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  18. 18. Structure Borne NVH Sources Slide 18 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  19. 19. Structure Borne NVH Sources Primary Consideration: Reduce the Source first as much as possible because whatever enters the structure is transmitted through multiple paths to the receiver. Transmission through multiple paths is more subject to variability. Slide 19 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  20. 20. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 20 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  21. 21. Receiver Considerations Subjective to Objective Conversions Subjective NVH Ratings are typically based on a 10 Point Scale resulting from Ride Testing Receiver Sensitivity is a Key Consideration A 2 ≈ 1/2 A 1 Represents 1.0 Rating Change TACTILE: 50% reduction in motion SOUND : 6.dB reduction in sound pressure level ( long standing rule of thumb ) Slide 21 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  22. 22. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 22 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  23. 23. Symbolic Model of Unibody Passenger Car 8 Degrees of Freedom 2 4 8 1 3 5 6 7 Total 2178.2 Kg (4800LBS) Tires 350.3 N/mm Mass Sprung 1996.7 Kg KF 43.8 N/mm Unsprung 181.5 Kg (8.33% of Total) KR 63.1 N /mm Powertrain 181.5 Kg Beam mass lumped on grids like a beam M2,3,4 =2 * M1,5 Slide 23 From Reference 6 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  24. 24. 8 Degree of Freedom Vehicle NVH Model Engine Mass 8 Engine Flexible Beam for Body Isolator 1 2 3 4 5 Suspension Springs 6 7 Wheels Tires Slide 24 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  25. 25. 8 Degree of Freedom Vehicle NVH Model Force Applied to Powertrain Assembly Feng 8 1 2 3 4 5 6 7 Forces at Powertrain could represent a First Order Rotating Imbalance Slide 25 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  26. 26. Engine Isolation Example Response at M id Car 1.0000 Constant Force Load; F~A 15.9 Hz 8.5 Hz Velocity (mm/sec) 0.1000 7.0 Hz 0.0100 0.0010 2 4 8 1 3 5 6 7 700 Min. RPM First Order Unbalance 0.0001 Operation Range of Interest 5.0 10.0 15.0 20.0 Frequency Hz Slide 26 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  27. 27. Concepts for Increased Isolation “Double” isolation is the typical strategy for further improving isolation of a given vehicle design. Second Level of Isolation is at Subframe to Body Mount Subframe is Intermediate Structure Suspension Bushing is first level Slide 27 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  28. 28. 8 Degree of Freedom Vehicle NVH Model Removed Double Isolation Effect 8 1 2 3 4 5 Wheel 6 Mass 7 Removed Slide 28 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  29. 29. Double Isolation Example Vertical Response at DOF3 6.0E+00 Base Model 5.0E+00 (mm/sec) Without Double_ISO 4.0E+00 2 4 8 1 3 5 6 7 3.0E+00 Velocity 1.414*fn 2.0E+00 1.0E+00 0.0E+00 5.0 10.0 15.0 20.0 Frequency Hz Slide 29 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  30. 30. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 30 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  31. 31. Mode Management Chart EXCITATION SOURCES Inherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.) Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances) 0 5 10 15 20 25 30 35 40 45 50 First Order Wheel/Tire Unbalance Hz V8 Idle Hot - Cold CHASSIS/POWERTRAIN MODES Suspension Hop and Tramp Modes Ride Modes Suspension Longitudinal Modes Powertrain Modes Exhaust Modes 0 5 10 15 20 25 30 35 40 45 50 Hz BODY/ACOUSTIC MODES Body First Torsion Steering Column First Vertical Bending Body First Bending First Acoustic Mode 0 5 10 15 20 25 30 35 40 45 50 Hz (See Ref. 1) Automotive Analytics LLC 2009 Slide 31 2009 SAE NVC Structure Borne Noise Workshop
  32. 32. 8 Degree of Freedom Vehicle NVH Model Bending Mode Frequency Separation 8 1 2 3 4 5 Beam Stiffness was adjusted to align Bending Frequency with Suspension 6 7 Modes and then progressively separated back to Baseline. Slide 32 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  33. 33. 8 DOF Mode Separation Example Response at Mid Car 18.2 Hz Bending 13.Hz Bending 100.00 10.6 Bending 2 4 8 1 3 5 Velocity (mm/sec) 6 7 10.6 Hz 10.00 13.0 Hz 18.2 Hz 1.00 0.10 5 10 15 20 Frequency Hz Slide 33 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  34. 34. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 34 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  35. 35. Mount at Nodal Point First Bending: Nodal Point Mounting Example Front input forces Rear input forces Locate wheel centers at node points of the first bending modeshape to prevent excitation coming from suspension input motion. Slide 35 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  36. 36. Mount at Nodal Point First Torsion: Nodal Point Mounting Examples Side View Rear View Passenger sits at Engine node point for First Torsion. Transmission Mount of a 3 Mount N-S P/T is near the Torsion Node. Slide 36 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  37. 37. Powertrain Bending Mode Nodal Mounting 1 2 3 4 5 6 7 Mount system is placed to support Powertrain at the Nodal Locations of the First order Bending Mode. Best compromise with Plan View nodes should also be considered. Slide 37 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  38. 38. 8 Degree of Freedom Vehicle NVH Model Bending Node Alignment with Wheel Centers Redistribute Beam Masses 8 to move Node Points to Align with points 2 and 4 1 2 3 4 5 6 7 Slide 38 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  39. 39. First Bending Nodal Point Alignment Response at Mid-Car 4.0E+00 Node Shifted 4 Base Model 8 2 (m m/sec) 1 3 5 6 7 3.0E+00 2.0E+00 Velocity 1.0E+00 0.0E+00 5.0 10.0 15.0 20.0 Frequency Hz Slide 39 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  40. 40. Low Frequency Basics • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 40 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  41. 41. Dynamic Absorber Concept Auxiliary Spring-Mass-Damper m = M / 10 x x SDOF 2DOF M M YO YO Slide 41 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  42. 42. Powertrain Example of Dynamic Absorber Anti-Node Identified at end of Powerplant k c m Absorber attached at anti-node acting in the Vertical and Lateral plane. Tuning Frequency = √ k/m Slide 42 [Figure Courtesy of DaimlerChrysler Corporation] Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  43. 43. Baseline Sound Level Baseline Sound Level 63 Hz Dynamic Absorber 63 Hz Dynamic Absorber 63 + 110 Hz Absorbers 63 + 110 Hz Absorbers 10 dB Slide 43 [Figure Courtesy of DaimlerChrysler Corporation] Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  44. 44. Low Frequency Basics - Review • Source-Path-Receiver Concept • Single DOF System Vibration • NVH Source Considerations • Receiver Considerations • Vibration Attenuation Strategies Provide Improved Isolation Mode Management Nodal Point Mounting Dynamic Absorbers Slide 44 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  45. 45. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics Greg Goetchius • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 45 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  46. 46. Mid Frequency NVH Fundamentals This looks familiar! Frequency Range of Interest has changed to 150 Hz to 1000 Hz Slide 46 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  47. 47. Typical NVH Pathways to the Passenger PATHS FOR STRUCTURE Noise Paths are the BORNE Noise Paths are the same as Low same as Low NVH Frequency Region Frequency Region Slide 47 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  48. 48. Mid-Frequency Analysis Character Structure Borne Noise Airborne Noise • Mode separation is less practical in • Mode separation is less practical in High modal density mid-frequency mid-frequency and coupling in source, path and • New Strategy is Effective Isolation: • New Strategy is Effective Isolation: receiver Achieved by reducing energy transfer Achieved by reducing energy transfer locally between source and receiver at locally between source and receiver at key paths. key paths. Response Absorption + Local Stiffness Mass + + Global Stiffness Damping Sealing “Low” “Mid” “High” ~ 150 Hz ~ 1000 Hz Log Frequency ~ 10,000 Hz Slide 48 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  49. 49. Mid-Frequency Analysis Character Control Measures for Mid Frequency Concerns Effective Isolation Attenuation along Key Noise Paths Slide 49 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  50. 50. Mid-Frequency Analysis Character Control Measures for Mid Frequency Concerns Effective Isolation Attenuation along Key Noise Paths Slide 50 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  51. 51. Isolation Effectiveness Classical SDOF: Rigid Source and Receiver “Real Structure” Flexible (Mobile) 1.0 Source and Receiver Transmissibility Ratio Isolation Region Isolation Region f/fn 1.0 1.414 10.0 Effectiveness deviates from the classical development as resonances occur in the receiver structure and in the foundation of the source. Slide 51 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  52. 52. Mobility • Mobility is the ratio of velocity response at the excitation point on structure where point force is applied Velocity Mobility = Force • Mobility, related to Admittance, characterizes Dynamic Stiffness of the structure at load application point Frequency * Displacement Mobility = Force Frequency = Dynamic Stiffness Slide 52 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  53. 53. Isolation • The isolation effectiveness can be quantified by a theoretical model based on analysis of mobilities of receiver, isolator and source • Transmissibility ratio is used to objectively define measure of isolation Force from source with isolator TR = Force from source without isolator V Receiver Vr V Receiver Vr V Fr Fr Fs = Yi + Y r + Y s F ir V ir Fs Vs Isolator V is Source F is V F s= Fs Yr +Ys Vs Source Slide 53 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  54. 54. Isolation Force from source with an isolator Receiver Vm TR = Force from source without an isolator Fm TR =  ( Y r + Y s ) / ( Y i + Y r + Y s )  F im V im Isolator V if Y r : Receiver mobility F if Y i : Isolator mobility Y s : Source mobility Ff Vf Source • For Effective Isolation (Low TR) the Isolator Mobility must exceed the sum of the Source and Receiver Mobilities. Recall that Y ∝1 K Slide 54 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  55. 55. Designing Noise Paths 1 1 1 1 1 TR =  ( + ) / ( + + ) K body K source K body K iso K source K source K body K iso K iso 1.0 5.0 20.0 1.0 0.67 0.55 0.51 5.0 0.55 0.29 0.20 20.0 0.51 0.20 0.09 Generic targets: body to bushing stiffness ratio of at least 5.0 source to bushing stiffness ratio of at least 20.0 Slide 55 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  56. 56. Body-to-Bushing Stiffness Ratio Relationship to Transmissibility 0.6 For a source ratio of 20 Transmissibility Ratio TR 0.5 0.4 Target Min. = 5 0.3 gives TR = .20 0.2 0.1 0 1 2 3 4 5 6 7 8 9 10 Stiffness Ratio; K body / K iso Slide 56 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  57. 57. Mid-Frequency Analysis Character Control Measures for Mid Frequency Concerns Effective Isolation Attenuation along Key Noise Paths Slide 57 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  58. 58. Identifying Key NVH Paths Key NVH paths are identified by Transfer Path Analysis (TPA) Tactile Tactile Acoustic Acoustic Transfer Transfer Transfer Transfer Fi Break the system at the points where the forces enter the body (Receiver) Operating loads Operating loads Total Acoustic Response is summation of partial responses over all noise paths Pt = Σ paths [Pi ] = Σ paths [ (P/F) i * Fi ] Slide 58 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  59. 59. Designing Noise Paths Acoustic Transfer (P/F)i Acoustic Transfer (P/F)i P/V V/F P/F (Kbody) F F F F F F Fi F Operating loads create Forces (Fi) into body at All noise paths Pt = Σ paths [Pi ] = Σ paths [ Fi * (P/F) i ] = Σ paths [ Fi * (P/V) i * (V/F)i] Measurement Parameters Generic Targets P/F Acoustic Sensitivity 50 - 60 dBL/N V/F Structural Point Mobility 0.2 to 0.3 (Receiver Side) mm/sec/N Slide 59 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  60. 60. “Downstream” Effects: Body Panels Recall for Acoustic Response Pt Pt = Σ paths [Pi ] = Σ paths [ Fi * (P/V) i * (V/F)i] (P/V)i ! “Downstream” (Body Panel) System Dynamics: Three Main Effects: 1. Panel Damping Increased Damping 3. Panel Acoustic Contribution 2. Panel Stiffness Increased Stiffness Slide 60 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  61. 61. Generic Noise Path Targets Primary: Minimize the Source Force < 1.0 N K body K source > 5.0 > 20.0 K iso K iso Structural Mobility < 0.2 to 0.3 mm/sec/N Acoustic 50 - 60 < Sensitivity dBL/N Panel Damping Loss Factor > .10 Slide 61 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  62. 62. Final Remarks on Mid Frequency Analysis • Effective isolation at dominant noise paths is critical • Reduced mobilities at body & source and softened bushing are key for effective isolation • Mode Separation remains a valid strategy as modes in the source structure start to participate • Other means of dealing with high levels of response (Tuned dampers, damping treatments, isolator placement at nodal locations) are also effective Slide 62 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  63. 63. Structure Borne NVH: Concepts Summary • Source-Path-Receiver as a system 1. Reduce Source 2. Rank and Manage Paths 3. Consider Subjective Response • Effective Isolation • Mode Management • Nodal Point Placement • Attachment Stiffness • “Downstream” (Body Panel) Considerations Slide 63 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  64. 64. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 64 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  65. 65. Tool Box Demo Test Results Toolbox Demo Noise Test Results 90 85 80 70 68 SPL (dBA) 63 61 60 55 50 47 40 39 30 1) Baseline: 2) Imbalance + 3) No Imbalance, 4) No Imbalance, 5) No Imbalance + 6) #5 + Absorption 7) #6 + Insulator Imbalance, No Isolation No Isolation No Isolation + Isolation + Mat Isolation Damping Damping Slide 65 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  66. 66. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Jianmin Guan Slide 66 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  67. 67. Real World Application Example Introduction Slide 67 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  68. 68. Quietness during Idle and Electric-Vehicle Operation Root Cause Diagnostics: 1. Water pump in the inverter cooling system 2. Electromagnetic noise of the motor, the inverter, and other units Reduce Inverter Water Pump Loads: 1. Reduce pump impeller imbalance 2. Redesign bearing structure 3. Changing motor structure Improve Isolation from Body: 1. Install rubber isolator 2. Increase mounting bracket rigidity 3. Improve Inverter case Slide 68 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  69. 69. Quietness during Idle and Electric-Vehicle Operation Root Cause Diagnostics: 1. Water pump in the inverter cooling system 2. Electromagnetic noise of the motor, the inverter, and other units Reduce Inverter Water Pump Loads: 1. Reduce pump impeller imbalance 2. Redesign bearing structure Reduce 3. Changing motor structure Source Effective Isolation Improve Isolation from Body: 1. Install rubber isolator Attach. Stiffness 2. Increase mounting bracket rigidity 3. Improve Inverter case Downstream Slide 69 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  70. 70. Engine Start Vibration Root Cause Diagnostics: 1. Engine torque fluctuations 2. Engine torque reaction forces Reduce Torque Fluctuation: 1. Change intake valve closing timing 2. Control piston stop position 3. Adjust injected fuel volume and ignition timing Reduce Effect of Engine Loads: 1. Operating MG1 at high torque during engine start 2. Implement vibration-reducing motor control 3. Use two stage hysteretic torsional damper 4. Shorten distance between principal elastic axis and center of gravity of power plant Slide 70 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  71. 71. Engine Start Vibration Root Cause Diagnostics: 1. Engine torque fluctuations 2. Engine torque reaction forces Reduce Torque Fluctuation: 1. Change intake valve closing timing 2. Control piston stop position 3. Adjust injected fuel volume and ignition timing Reduce Source Mode Manage. Reduce Effect of Engine Loads: 1. Operating MG1 at high torque during engine start Damper 2. Implement vibration-reducing motor control 3. Use two stage hysteretic torsional damper 4. Shorten distance between principal elastic axis and center of gravity of power plant Effective Isolation Slide 71 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  72. 72. 2nd Order Engine Induced Boom Root Cause Diagnostics: 1. 2nd order couple of the reciprocating inertia of piston 2. THS II Trans 50 mm longer and 35 kg heavier 3. Lower power plant bending mode 4. Requires 1.5X higher mount rates Reduce Effect of 2nd order Couple: 1. Increase power plant bending mode 2. Move mount to a nodal point 3. Embed mounts inside cross member 4. Reduces distance from principle elastic axis to CG 5. Optimized vertical to lateral rate ratio Slide 72 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  73. 73. 2nd Order Engine Induced Boom Root Cause Diagnostics: 1. 2nd order couple of the reciprocating inertia of piston 2. THS II Trans 50 mm longer and 35 kg heavier 3. Lower power plant bending mode 4. Requires 1.5X higher mount rates Mode Manage. Reduce Effect of 2nd order Couple: 1. Increase power plant bending mode Nodal 2. Move mount to a nodal point Mounting 3. Embed mounts inside cross member Effective 4. Reduces distance from principle Isolation elastic axis to CG 5. Optimized vertical to lateral rate ratio Slide 73 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  74. 74. Engine Radiated Noise Root Cause Diagnostics: 1. 24th MG2 order excitation 2. Lower MG2 reduction gear ratio 3. Lower transmission bending mode - two key modes identified Reduce 24th order Loads: Arranged permanent magnets in V shape with optimized angle Reduce Effect of 24th order Loads: 1. Modified Trans case to improve modes 2. Added dynamic damper at a high amp. point on Trans case 3. Added ribs in high radiating area of Trans case Slide 74 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  75. 75. Engine Radiated Noise Root Cause Diagnostics: 1. 24th MG2 order excitation 2. Lower MG2 reduction gear ratio 3. Lower transmission bending mode - two key modes identified Reduce Reduce 24th order Loads: Source Arranged permanent magnets in V shape with optimized angle Mode Reduce Effect of 24th order Loads: Manage. 1. Modified Trans case to improve modes Damper 2. Added dynamic damper at a high amp. point on Trans case 3. Added ribs in high radiating area of Trans case Downstream Slide 75 Automotive Analytics LLC International Copyright © 2009 SAE 2009 2009 SAE NVC Structure Borne Noise Workshop
  76. 76. Structure Borne NVH Workshop • Introduction • Low Frequency Basics • Mid Frequency Basics • Live Noise Attenuation Demo • Real World Application Example • Closing Remarks Slide 76 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  77. 77. Structure Borne NVH: Concepts Summary • Source-Path-Receiver as a system 1. Reduce Source 2. Rank and Manage Paths 3. Consider Subjective Response • Effective Isolation • Mode Management • Nodal Point Placement • Attachment Stiffness • “Downstream” (Body Panel) Considerations Slide 77 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  78. 78. SAE 2009 NVH Conference Structure Borne NVH Workshop Thank You for Your Time! Q&A Slide 78 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  79. 79. Structure Borne NVH References Primary References (Workshop Basis: 4 Papers) 1. A. E. Duncan, et. al., “Understanding NVH Basics”, IBEC, 1996 2. A. E. Duncan, et. al., “MSC/NVH_Manager Helps Chrysler Make Quieter Vibration-free Vehicles”, Chrysler PR Article, March 1998. 3. B. Dong, et. al., “Process to Achieve NVH Goals: Subsystem Targets via ‘Digital Prototype’ Simulations”, SAE 1999-01-1692, NVH Conference Proceedings, May 1999. 4. S. D. Gogate, et. al., “’Digital Prototype’ Simulations to Achieve Vehicle Level NVH Targets in the Presence of Uncertainties’”, SAE 2001-01-1529, NVH Conference Proceedings, May 2001 Structure Borne NVH Workshop - on Internet At SAE www.sae.org/events/nvc/specialevents.htm WS + Refs. at www.AutoAnalytics.com/papers.html Slide 79 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop
  80. 80. Structure Borne NVH References Supplemental Reference Recommendations 5. T.D. Gillespie, Fundamentals of Vehicle Dynamics, SAE 1992 (Also see SAE Video Lectures Series, same topic and author) 6. D. E. Cole, Elementary Vehicle Dynamics, Dept. of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, Sept. 1972 7. J. Y. Wong, Theory of Ground Vehicles, John Wiley & Sons, New York, 1978 8. N. Takata, et.al. (1986), “An Analysis of Ride Harshness” Int. Journal of Vehicle Design, Special Issue on Vehicle Safety, pp. 291-303. 9. T. Ushijima, et.al. “Objective Harshness Evaluation” SAE Paper No. 951374, (1995). Slide 80 Automotive Analytics LLC 2009 2009 SAE NVC Structure Borne Noise Workshop

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