Transcript weaverjm.faculty.udmercy.edu

Design For NVH
MPD575 DFX
Jonathan Weaver
*
Development History
• Originally developed by Cohort 1
students: Jeff Dumler, Dave
McCreadie, David Tao
• Revised by Cohort 1 students: T.
Bertcher, L. Brod, P. Lee, M. Wehr
• Revised by : D. Gaines, E.
Donabedian, R. Hall, E. Sheppard, J.
Randazzo, J. Torres, B. Dhruna, J.
Stevens, D. Kammerzell
*
Design For NVH (DFNVH)
•
•
•
•
•
•
•
•
Introduction to NVH
DFNVH Heuristics
DFNVH Process Flow and Target Cascade
DFNVH Design Process Fundamentals
Key DFNVH Principles
– Airborne NVH
• Radiated/Shell Noise
• Tube Inlet/Outlet Noise
• Impactive Noise
• Air Impingement Noise
– Structure-Borne NVH
Wind Noise Example
2002 Mercury Mountaineer Case Study
Summary
*
Introduction to NVH What is
NVH?
● Vibration is movement, and vibration that reaches the
passenger compartment at the right frequency is
noise.
● The science of managing the vibration frequencies in
automobile design is called NVH - Noise, Vibration,
and Harshness.
● It is relatively easy to reduce noise and vibration by
adding weight thereby changing the natural frequency,
but in an era when fuel economy demands are forcing
designers to lighten the car, NVH engineers must try
to make the same parts stiffer, quieter, and lighter. *
Introduction to NVH What is
Noise:
NVH?
•Typically denotes unwanted sound, hence treatments
are normally implemented to eliminate or reduce it
•Variations are detected by ear
•Characterized by frequency, level & quality
•May be Undesirable (Airborne)
•May be Desirable (Powerful Sounding Engine)
*
Introduction to NVH What is NVH?
Vibration
– An oscillating motion about a reference point
which occurs at some frequency or set of
frequencies
• Motion sensed by the body (structure-borne)
– mainly in 0.5 Hz - 50 Hz range
• Characterized by frequency, magnitude and direction
• Customer Sensitivity Locations are steering column, seat
track, toe board, and mirrors (visible vibrations)
*
Introduction to NVH What is NVH?
• Harshness
– Low-frequency (25 -100 Hz) vibration of the
vehicle structure and/or components
– Frequency range overlaps with the vibration
frequencies but human perception of it is different.
• Perceived tactilely and/or audibly
• Rough, grating or discordant sensation
• Unpleasant
*
Introduction to NVH
What is NVH
Airborne Noise:
● Sound most people interpret as noise, and travels
through gaseous mediums like air.
● Some people classify human voice as airborne noise, a
better example is the hum of your computer, or an air
conditioner.
● Detected by the human ear and most likely impossible
to detect with the sense of touch.
● Treatment/Countermeasures: Elimination of the
source if possible; Barriers or Absorbers if not.
*
Introduction to NVH What is NVH?
Structureborne:
• Vibration that you predominately “feel”, like the deep
booming bass sound from the car radio next to you at a
stoplight.
• These are typically low frequency vibrations that your ear
may be able to hear, but you primarily “feel”
• Treatment / Countermeasure: Damping or Isolation
*
Introduction to NVH What is NVH?
Barriers:
•Performs a blocking function to the path of the airborne
noise. Examples: A closed door, backing on automotive
carpet.
•Barrier performance is strongly correlated to the openings
or air gaps that exist after the barrier is installed. A
partially open door is a less effective barrier than a totally
closed door.
•Barrier performance is dependent on frequency, and is
best used to treat high frequencies.
•If no gaps exist when the barrier is employed, then weight
becomes the dominant factor in comparing barriers.
*
Introduction to NVH What is NVH?
Barriers: Design Parameters
•
•
•
•
•
Location (close to source)
Material (cost/weight)
Mass per Unit Area
Number, Direction and Thickness of Layers
Number and Size of Holes
Note: Active Noise Cancellation (ANC) is a recent method discussed in
this DFX. For airborne noise it can work between 30 and 1000 Hz to
change the noise heard. ANC units offset unwanted sound by emitting
opposing frequencies that “cancel” the unwanted sound. ANC
technology is available in cars like the Lincoln MKS, Honda Odyssey,
and Infiniti Q50
*
Introduction to NVH What is NVH?
Absorbers:
•Reduces sound by absorbing the energy of the sound
waves, and dissipating it as heat. Examples: headliner
and hood insulator
•Absorbers are ranked by the ability to absorb
sound that otherwise would be reflected off its surface
•Good absorber design contains complex geometries
that trap sound waves and prevent reflection back into
the air
•Absorber performance varies with frequency
*
Introduction to NVH What is NVH?
Absorbers: Design Parameters
•Area of absorbing material (large as possible)
•Type of material (cost/weight)
•Thickness (package/installation)
*
Introduction to NVH What is NVH?
Damping:
•Defined as a treatment of vibration to reduce the
magnitude of targeted vibrations
•Damping is important because it decreases the
sensitivity of the body at resonant frequencies
•Vehicle Sources of Damping are: Mastics, sound
deadening materials, weather-strips/seals, tuned
dampers, and body/engine mounts and location
specific added mass
*
Introduction to NVH What is NVH?
Damping: Design Parameters
•Density (low as possible)
•Stiffness (high as possible)
•Thickness (damping increases with the square of thickness)
•Free surface versus constrained layer
Constrained layer damping is more efficient than free surface damping on
a weight and package basis, but is expensive, and raises assembly
issues.
Note: Temperature range of interest is very important because stiffness
and damping properties are very temperature sensitive
*
Introduction to NVH What is NVH?
Isolation:
•Method of detaching or separating the vibration from
another system or body.
•By definition: does nothing to reduce the magnitude of
vibration, simply uncouples the vibration from the
system you are protecting.
•All isolation materials perform differently at different
frequencies, and if engineered incorrectly, may make
NVH problems worse instead of better.
*
Introduction to NVH What is NVH?
Isolation by Bushings and Mounts:
•Excitations are generally applied to or by components
such as engine or road wheels.
•The force to the body is the product of the mount
stiffness and the mount deflection, therefore strongly
dependent on the mount spring rates
•Compliant (softer) mounts are usually desirable for NVH
and ride, but are undesirable for handling, durability and
packaging (more travel/displacement space required).
•Typically, the isolation rates (body mount/engine mount
stiffness) that are finally selected, is a result of the
reconciliation (trade-off) of many factors.
*
Introduction to NVH How is NVH
Measured?
One of the challenges of measuring and analyzing
powertrain NVH is the large range in the absolute levels of
sounds and vibrations that occur. Measurement and
analysis require observation of small (low-level) signals in
the presence of large (high-level) signals. This is required
due to the capability of the human ear to process signals at
a wide range of levels.
Introduction to NVH How is NVH
Measured?
Amplitude Scales:
The ratio between the largest and smallest signals that we can analyze is the
dynamic range. Using a linear amplitude measurement scale limits our ability to
display a wide dynamic range simultaneously as shown on Graph A. However, as
shown on Graph B of the same sound, a logarithmic amplitude scale compresses
large amplitude signals and expands small ones so that we can display a wide
dynamic range simultaneously for analysis. This is why we use the logarithmic
decibel (dB) scale to measure sounds and vibrations
Introduction to NVH How is NVH
Measured?
Amplitude Scales:
The decibel (dB) is a logarithmic representation of an amplitude ratio. It is 20 times the
base 10 logarithm of the ratio of the measured amplitude to a reference. In the case of
sound, the units of measure are pressure and the reference is typically the threshold of
hearing. On the dB scale, 0 dB approximately corresponds to the normal threshold of
human hearing and 140 dB approximately corresponds to the threshold of pain. Each 1
dB step approximately represents the smallest change in sound level that normal human
hearing can detect 50% of the time. The table compares dB levels for various sounds at
1 meter and 10 meters. To become more familiar with dB levels.
Introduction to NVH How is NVH
Measured?
Amplitude Scales:
The formula for calculating sound pressure level (SPL) in decibel (dB) is:
Adding decibel (dB): Because the dB scale is a logarithmic ratio, we cannot add dB
levels directly. To add two dB values, we must apply the rules of logarithms as follows:
Introduction to NVHWhy Design
for NVH?
“NVH is overwhelmingly important to
customers. You never, ever get lucky
with NVH. The difference between
good cars and great cars is fanatical
attention to detail.”
Richard Parry-Jones, 11/99
*
Introduction to NVHWhy Design
for NVH?
• NVH impacts Customer Satisfaction
• NVH impacts Warranty
• NVH has financial impact
*
Introduction to NVHWhy Design
for NVH?
Corporate Leverage vs. Customer Satisfaction
NVH Customer Satisfaction Needs Improvement at 3 MIS
9
IMPROVE
SUSTAIN / BUILD
NVH
Relative
Leverage
*
6.
9
Overall
Handling
Cup holders
Exterior Styling
5
*
65
%
REVIEW
*
MAINTAIN
77
%
85
%
*
Introduction to NVHWhy Design for
NVH?
NVH Can Both Dissatisfy and Delight
+ Customer
Satisfaction
KANO Model
Sound Quality
TGR
Harley
Mustang
Lexus
Performance
Exciting Quality
(Surprise & Delight)
Performance Quality
(Attributes)
+ Degree of
+
Achievement
Performance
Dissatisfier
s
Axle Whine Unusual Noises
Wind Noise
TGW
Basic Quality
(Inhibitors)
- Customer
Satisfaction
*
Introduction to NVHWhy Design
for NVH?
• Customers place a high value on NVH
performance in vehicles
• About 1/3 of all Product / Quality
Complaints are NVH-related
*
NVH: Cost & Weight
Considerations
•
Often times, cost and weight targets prevent avoidance of NVH issues An example is a 2pc driveshaft, which is less expensive, lighter, and has fewer joints than a 3-pc driveshaft,
but has boom at a certain RPM. The 3-pc driveshaft does not demonstrate the boom.
What do you do???
• NVH countermeasures CAN work harmoniously within the system as long as they are
DESIGNED INTO the system from the beginning.
How do I go about doing it?
– Get management buy-in. Costs for NVH countermeasures are never put into
programs early enough. This needs to change to ensure success.
– Run CAE early, using the best simulations available. Determine the frequency range
and driving mode. Trust your CAE.
– Develop NVH countermeasures and make sure they are on the first phase of
prototype vehicles (NOT the last)
– In this case, a torsional damper on the rear of the driveshaft solves the issue, but
interferes with the fuel tank
– Since packaging studies were run early, the fuel tank was modified prior to hard
tooling to provide clearance for the damper.
• Result
– A well-packaged driveshaft which is lighter, less expensive, and more durable than
the alternate design, which fully satisfies all customer and corporate requirements.
Heuristic: NVH is always a late guest to the party. Plan
countermeasures ahead to ensure you have enough energy,
time and tools to entertain your guest!
Introduction to NVHWhy Design for NVH?
• About 1/5 of all Warranty costs are NVHrelated
– Dealers may spend many hours to determine
source of NVH problem
– Dealers may have to repair or rebuild parts that
have not lost function but have become source of
NVH issue.
• NVH can provide both dissatisfaction and
delight
*
Design For NVH (DFNVH)
•
•
•
•
•
Introduction to NVH
DFNVH Heuristics
DFNVH Process Flow and Target Cascade
DFNVH Design Process Fundamentals
Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
Design For NVH
Heuristics
• Design the structure with good "bones"
– If the NVH problem is inherent to the architecture,
it will be very difficult to tune it out.
• To remain competitive, determine and
control the keys to the architecture from
the very beginning.
– Set aggressive NVH targets, select the best
possible architecture from the beginning, and stick
with it (additional upfront NVH resources are
valuable investments that will return a high yield)
*
Design For NVH
Heuristics
•
• Cost rules
– Once the architecture is selected, it will be
very costly to re-select another
architecture. Therefore, any bad design will
stay for a long time
*
Design For NVH
Heuristics
• Don't confuse the functioning of the parts
with the functioning of the system (Jerry
Olivieri, 1992).
– We need to follow Systems Engineering principles
to design for NVH. Customers will see functions
from the system, but sound vehicle designs
require the ability to develop requirements for the
parts by cascading functional requirements from
the system.
*
Design For NVH (DFNVH)
•
•
•
•
•
Introduction to NVH
DFNVH Heuristics
DFNVH Process Flow and Target Cascade
DFNVH Design Process Fundamentals
Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
DFNVH
Process Flow and Target Cascade
• During the early stages of a vehicle program, many
design trade-offs must be made quickly without detailed
information.
• For example, on the basis of economics and timing,
power plants (engines) which are known to be noisy are
chosen. The program should realize that extra weight
and cost will be required in the sound package.
(Historical Data)
• If a convertible is to be offered, it should be realized
that a number of measures must be taken to stiffen the
body in torsion, and most likely will include stiffening the
rockers. (Program Assumptions)
*
DFNVH
Process Flow and Target Cascade
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DFNVH
Process Flow and Target Cascade
Noise Reduction Strategy: Targets are set for the noise
reduction capability of the sound package.
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DFNVH
Process Flow and Target Cascade
Systems Engineering “V” and PD Process Timing
KO
PS
O
Customer
Wants/Needs
Define Req’s
S
PA
P
C
J1
C
R
P
Vehicle (VDS - P/T NVH etc)
Customer
Satisfaction
Confirm
System (SDS - Force, Sensitivity,...)
Cascade Targets &
Iterate
Subsystem (Stiffness,...)
Components SDS
Verify & Optimize
Optimize
*
DFNVH
Process Flow and Target Cascade
Trade-Offs Flow Chart
Program Specific Wants
PALS (QFD, VOC, etc.)
Vehicle Assumptions Fixed
SLA or MacPherson Strut Suspension
Functional Images for Segment
- R202
Vehicle Level Target Ranges
Subjective (1-10) and Objective
Preliminary Target Ranges
Future Functional Attribute
Targets
Objective Target Ranges VDS
Affordable Business Structure
(ABS)
Trade-Off Loop
Perform Iterations Until
Assumptions Comparable
SI
System & Sub-System
Targets
Force or P/F Targets
Determined with
Parametric Models
Component End Item
Targets
Component Resonant
Frequencies, etc.
PA
System/Sub-System Assumptions
McPherson vs. SLA, etc.
Requires Hardware Parametric
Model
Is Gross Architecture Feasible?
Design Optimization
CAE Optimization
Hardware Development
Development
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DFNVH
Process Flow and Target Cascade
NVH Functional Attribute
Sub -Attributes
Road
Wind
P/T
Brake
Comp. S.Q.
S&R
Pass-by Noise (Reg.)
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DFNVH
Process Flow and Target Cascade
Convert attribute target strategy to objective targets
POWERTRAIN
NV
H
IDLE NVH
CRUISE NVH
ACCELERATION
NV
H
ACCELERATION
WO
T
DECELERATION
NV
H
TRANSIENTS
NV
H
TAKE-OFF
DRIVEAWAY
NV
H
TIP-IN / TIP OUT
NV
H
STEERING
NVH
ENGINE START
UP / SHUT OFF
NV
H
AUTOMATIC
TRANS. SHIFT
NV
H
*
DFNVH
Process Flow and Target Cascade
Acceleration NVH Target Cascade
CUSTOMER
PERCEIVED P/T
NVH
AIRBORNE NOISE
P/T RADIATED
NOISE
AIRBORNE
NOISE
REDUCTION
STRUCTURE-BORNE
NOIS
E
BODY ACOUSTIC
SENSITIVIT
Y
P/T VIBRATION
MOUNT
FORCES
MOUNT
DYNAMIC
STIFFNES
S
*
DFNVH
Process Flow and Target Cascade
NVH Classification Parameters
•Operating Condition (idle, acceleration, cruise on a
rough road, braking, wind…)
•Phenomenon (boom, shake, noise…) this is strongly
affected by the frequency of the noise and vibration or
input.
•Source (powertrain, road, wind ..etc)
•Classifying NVH problems provides a guidance for
design, for example: low frequency problems such as
shake historically involve major structural
components such as cross members and joints.
*
DFNVH
Process Flow and Target Cascade
Operating Condition
NVH Concerns
Idle
Shake and boom due to engine torque.
Lugging
Shake and boom due to engine torque.
Wide Open Throttle
(WOT)
Noise and vibration due to engine, driveline,
exhaust vibration, and radiated noise.
Cruise (smooth road)
Shake, roughness, and boom due to tire and
powertrain imbalance and tire force variation,
wind noise, and tire noise. Transmission and Axle
whine.
Cruise (rough road)
Road noise and shake
Tip-in
"Moan" due to powertrain bending.
Braking
Squeal, grind, moan and shudder.
DFNVH
Process Flow and Target Cascade
•The customer’s experience of NVH problems
involves two factors, 1) the vehicle operating
conditions, such as braking or WOT, and 2) the
very subjective responses such as boom, growl,
and groan.
•It is critical that objective and subjective ratings be
correlated so the customer concerns can be
directly related to objective measures. This
requires subjective-objective correlation studies
comparing customer ratings and objective
vibration measurements.
*
DFNVH
Process Flow and Target Cascade
NVH Aspect
Subjective Response
Boom
Low frequency sound 20 - 100 hz.
Drone
Large amplitude pure tone in the region 100-200 hz
Growl
Modulated low/medium frequency broad band noise
100-1000 hz
Groan
Transient broadband noise with noticeable time
variation and tone content, 50-250 hz
Moan
A sound in the 80 to 200 Hz range, frequently
consisting of one or two tones
Squeak
High pitched broadband transient noise.
Whine
Mid-frequency to high frequency pure tone (possibly
with harmonics), 200-2000 hz
*
DFNVH
Process Flow and Target Cascade
Summary
•Noise reduction targets should be set for important
operating conditions such as WOT (wide open throttle).
•Noise reduction targets must be set for the radiated
sound from various sources.
•The sound package must be optimized for barrier
transmissibility and interior absorption.
•Classifying NVH problems provides guidance for design
and a means to communication among engineers.
•NVH from audio system interaction is also important with
pulse width modulated signals for loads that couple with
audio speakers.
*
Design For NVH (DFNVH)
• Introduction to NVH
• DFNVH Heuristics
• Process Flow and Target Cascade
• DFNVH Design Process Fundamentals
• Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
DFNVH Process
FundamentalsSource-PathResponder
Excitation
Sensitivity
Excitation Source Examples:
Response
•
•
•
•
•
•
•
Engine Firing Pulses
Driveshaft Imbalance
Rough Road
Tire Imbalance
Speed Bump
Gear Meshing
Body-Shape Induced
Vortices
• Brake Roughness
*
DFNVH Process
FundamentalsSource-PathResponder
Excitation
Sensitivity
Response
Sensitivity:
Tendency of the path to transmit energy from the source to the
responder, commonly referred to as the transfer function of the
system
*
DFNVH Process
FundamentalsSource-PathResponder
Example:
Body Sensitivity
Interior
Sound
Pressure
Tactile
∙ Point mobility (v/F)
STRUCTURE
p (dB)
(Structural velocity / induced by force)
Force Input
at Driving
Point
Acoustic
V (mm/s) Vibration
F (N)
∙ Airborne (p/p)
(Airborne sound pressure induced / by pressure waves)
STRUCTURE
∙ Structure-borne (p/F)
Velocity
at Driving Point
Interior
Sound
Pressure
p (dB)
(Airborne sound pressure / induced by force)
p (dB)
Airborne
Noise
*
DFNVH Process
FundamentalsSource-PathResponder
Body Sensitivity Demonstration
Typical Point Mobility Spectrum for Compliant and Stiff Structures
More
Compliant
Point Mobility (V/F)
Point Mobility
Less
Compliant
50
Frequency ( f )
140
*
DFNVH Process
FundamentalsSource-PathResponder
Excitation
Response:
Sensitivity
Response
Objective
(measurable)
Subjective
(customer perception)
• S/W Shake
• S/W Nibble
• Seat Track (Triax)
• Spindle Fore/Aft
• Tie Rod Lateral
• S/W Shake (vertical)
• S/W Nibble (rotational)
• Seat Track (non-specific)
*
S/W = Steering Wheel
Tailpipe
Responder
Body Acoustic
Attenuation (dB)
Intake Orifice
Engine Radiated
Sound
Airborne NVH
Airborne P/T NVH
DFNVH Process
FundamentalsSource-PathPowertrain
Noise Model
Body Acoustic
Attenuation (dB)
Active Engine
Vibration
(X, Y, Z)
Mount
Stiffness (N/mm)
Body Acoustic
Sensitivity
Active Exhaust
Vibration
(X, Y, Z)
Mount
Stiffness (N/mm)
Body Acoustic
Sensitivity
Structure-borne NVH
Structure-borne P/T NVH
Driver Right Ear
(dBA)
*
DFNVH Process
FundamentalsSource-PathResponder
Road Noise (P)
NPA
+
Chassis Forces
to Body (F)
Body/Frame
Sensitivity (P/F)
Sub-structuring
Tire/Wheel
Forces
Road Profile
+
Road Noise
Model
Suspension
Force Isolation
MA
Tire/Road Force
Transfer Function
Suspension/Frame
Modes
Tire/Wheel Modes &
Design Parameters
Suspension/Frame
Design Parameters
Modal Analysis
(MA)
Body Modes
Body Design
Parameters
*
DFNVH Process
FundamentalsSource-PathResponder
Driveline
Model
*
DFNVH Process
FundamentalsSound Quality
What is Sound Quality?
• Historically, Noise Control meant reducing sound level
• Focus was on major contributors (P/T, Road, Wind Noise)
• Sound has multiple attributes that affect customer perception
• All vehicle sounds can influence customer satisfaction
(e.g., component Sound Quality)
• Noise Control no longer means simply reducing dB levels
*
DFNVH Process
FundamentalsSound Quality
Why Sound Quality?
• Generally not tied to any warranty issue
• Important to Customer Satisfaction
- Purchase experience (door closing)
- Ownership experience (powertrain/exhaust)
• A strong indicator of vehicle craftsmanship
- Brand image (powertrain)
*
DFNVH Process
FundamentalsSound Quality
The Sound Quality Process
1. Measurement (recording)
2. Subjective evaluation (listening studies)
• Actual or surrogate customers
3. Objective analysis
• Sound quality Metrics
4. Subjective/Objective correlation
5. Component design for sound quality
*
DFNVH Process
FundamentalsSound Quality
Binaural Acoustic “Achen Heads”
Stereo Sound
Recording
representing
sound wave
interaction
with a partial
human torso
*
DFNVH Process
FundamentalsSound Quality
Sound Quality Listening Room
Used for
Customer
Listening
Clinics.
*
DFNVH Process
FundamentalsSound Quality
Poor Sound Quality
Good Sound Quality
*
DFNVH Process
FundamentalsSound Quality
Quantifying Door Closing Sound
Quality
1. Sound Level (Loudness)
2. Frequency Content (Sharpness)
3. Temporal Behavior
*
DFNVH Process
FundamentalsSound Quality
What Makes A Good Door Closing Sound?
Good Sound
Quiet
Low Frequency
(Solid)
One Impact
No Extraneous Noise
Poor Sound
Loud
High Frequency
(Tinny, Cheap)
Rings On (Bell)
Rattles, Chirps, etc.
*
DFNVH Process
FundamentalsSound Quality
Good
Level (dBa) (color)
Bad
Time (sec.) (x-axis)
Frequency (Hz) (y-axis)
Example: Qualifying Door Closing Sound Quality
DFNVH Process
FundamentalsSound Quality
Design for Sound Quality
Door Closing Example
Perceived Sound
Structure-borne
Radiated Snd.
Latch Forces
Inertia
Spring Rates
Airborne
Seal Trans Loss
Str. Compliance
Material
*
DFNVH Process
FundamentalsSound Quality
Conclusions
•
•
•
•
•
Sound Quality is critical to Customer Satisfaction
Understand sound characteristics that govern perception
Upfront implementation is the biggest challenge
Use commodity approach to component sound quality
Generic targets, supplier awareness, bench tests
Design For NVH (DFNVH)
• Introduction to NVH
• DFNVH Heuristics
• Process Flow and Target Cascade
• DFNVH Design Process Fundamentals
• Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
NVH Design Principles
• Dynamic System NVH Model:
Source x Path = Response
• Always work on sources first
– Reduce the level of ALL sources by using quiet
commodities
• Path is affected by system architecture. Need to select
the best architecture in the early design phase.
– Engineer the paths in each application to tailor the
sound level
• Only resort to tuning in the late stage of design
*
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Airborne NVH
Radiated/Shell Noise
Mechanism:
• Structural surface vibration imparts mechanical
energy into an adjacent acoustic fluid in the form of
pressure waves at same frequency as the surface
vibration. These waves propagate through the fluid
medium to the listener. Examples: powertrain
radiated noise, exhaust pipe/muffler radiated noise
Design principle(s):
• Minimize the vibration level on the surface of the
structure
*
Design Principles – Airborne NVH
Radiated/Shell Noise
Design Action(s):
• Stiffen: Add ribbing, increase gage thickness,
change material to one with higher elastic modulus,
and add internal structural supports
• Minimize surface area: Try to avoid round surfaces
• Damping: Apply mastic adhesives to surface, make
surfaces out of heavy rubber
• Mass loading: Add non-structural mass to reduce
vibration amplitude --- (Only as a last resort)
*
Design Principles – Airborne
NVHTube Inlet/Outlet Airflow Noise
Mechanism:
• Pressure waves are produced in a tube filled with
moving fluid by oscillating (open/closed) orifices.
These waves propagate down tube and emanate
from the inlet or outlet to the listener. Examples:
induction inlet noise, exhaust tailpipe noise
Design principle(s):
• Reduce the resistance in the fluid flow
*
Design Principles – Airborne
NVHTube Inlet/Outlet Airflow Noise
Design action(s):
• Make tubes as straight as possible
• Include an in-line silencer element with sufficient
volume (muffler)
• Locate inlet/outlet as far away from customer as
possible
• Design for symmetrical (equal length) branches
*
Design Principles – Airborne
NVHTube Inlet/Outlet Airflow Noise
V6 Intake Manifolds
*
Design Principles – Airborne
NVHImpactive Noise
Mechanism:
•
Two mechanical surfaces coming into contact with each
other causes vibration in each surface, which imparts
mechanical energy into adjacent acoustic fluid in the form
of pressure waves at the same frequency as the surface
vibration. These waves propagate through the fluid
medium to the listener.
- Examples: Tire impact noise, door closing sound, power door lock
sound
• Pressures waves caused by air pumping in and out of
voids between contacting surfaces
- Examples: Tire impact noise
*
Design Principles – Airborne
NVHImpactive Noise
Air Pumping
Air forced in and out of voids is called “air pumping”
*
Design Principles – Airborne
NVHImpactive Noise
Design principle(s):
• Reduce the stiffness of the impacting surfaces
• Increase damping of impacting surfaces
Design action(s):
• Change material to one with more compliance, higher
damping
• Management of modal frequencies, mode shapes of
impacting surfaces (tire tread pattern, tire cavity
resonance)
*
Design Principles – Airborne
NVHAir Impingement Noise
Mechanism:
• When an object moves through a fluid, turbulence is
created which causes the fluid particles to impact
each other. These impacts produce pressure waves
in the fluid which propagate to the listener.
Examples: engine cooling fan, heater blower, hair
dryer
Design principle(s):
• Reduce the turbulence in the fluid flow
*
Design Principles – Airborne
NVHAir Impingement Noise
Design action(s):
• Design fan blades asymmetrically, with
circumferential ring
• Optimize fan diameter and flow to achieve lowest
broad band noise
• Use fan shroud to guide the incoming and outgoing
airflow
*
NVH Design Principles
Structure-borne
NVH
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Airborne
NVHAirborne Noise Path Treatment
Noise
Reduction
Engine
Compartment
Absorption
Interior
Absorption
Body &
Insulator
Blocking
(Panels)
Pass-Thru
Sealing
(Components)
*
Design Principles – Airborne
NVHAirborne Noise Path Treatment
Design principle(s):
•
•
•
•
Eliminate noise source
Absorb noise from the source
Block the source noise from coming in
Absorb the noise after it is in
Design action(s):
•
•
•
•
•
Surround source with absorbing materials
Minimize number and size of pass-through holes
Use High-quality seals for pass-through holes
Add layers of absorption and barrier materials in noise path
Adopt target setting/cascading strategy
*
Design Principles – Airborne
NVHAirborne Noise Path Treatment
air absorption materials
• Barrier performance is
controlled mainly by mass
– 3 dB improvement requires
41% increase in weight
• Mastic or laminated steel
improves low frequency
sound quality
• Soft decoupled layers (1030 mm) absorb sound
• Pass-thru penetration
seals are weaker than
*
steel
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Airborne
NVHAirborne Noise Responder
Treatment
Design principle(s):
• Absorb noise at listener
• Block noise at listener
• Breakup of acoustic wave pattern
Design action(s):
•
•
•
•
Surround listener with absorbing materials
Ear plugs
Design the surrounding geometry to avoid standing waves
Add active noise cancellation/control devices
*
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Structureborne NVH
• Structureborne NVH is created due to
interaction between source, path,and
responder.
• Frequency separation strategy for
excitation forces, path resonance and
structural modes needs to be achieved
to avoid NVH issues.
*
Design Principles – Structureborne NVH
• What happens if frequencies align?
• If a structural element having a natural
frequency of f is excited by a coupled
source at many frequencies, including f,
it will resonate, and could cause a
concern depending on the path.
(This is exactly like a tuning fork.)
*
Design Principles – Structureborne NVH
The steering column vibration will have an extra large peak if the
steering column mode coincides with the overall bending mode.
*
Design Principles – Structureborne NVH
Natural frequencies of major structures need to be
separated to avoid magnification.
● Powertrain modes need to be separated from the 1st
and 2nd body bending and torsion modes by at least
2Hz.
● Cowl and cross car beam modes must be separated
from steering column modes by as much as possible
(minimum of 1Hz)
*
Design Principles – Structureborne NVH
In addition to adopting modal
separation strategies, other principles are
listed below:
• Reduce excitation sources
• Increase isolation as much as possible
• Reduce sensitivity of structural response.
*
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Structureborne NVH
Excitation Source
Mechanism:
• Excitation source can be shown in the form of forces
or vibrations. They are created by the movement of
mass due to mechanical, chemical, or other forms of
interactions.
Design principle(s):
• Reduce the level of interactions as much as possible.
• Take additional actions when it is impossible to
reduce interactions.
*
Design Principles – Structureborne NVH
Excitation Source
Design action(s):
• Achieve high overall structural rigidity
• Minimize unbalance
• Achieve high stiffness at attachment points of
the excitation objects (shock towers, frame
mounting points, or subframe mounting
points)
*
Design Principles – Structureborne NVH
Excitation Source
A/C Compressor – Bad Example
Cantilever
Effect →
Less Rigid
*
Design Principles – Structureborne NVH
Excitation Source
A/C Compressor - Good Example
*
Design Principles – Structureborne NVH
Excitation Source
Example: Axle Whine
Characteristics:
- Tonal noise 300 - 800 Hz
- Occurs between 40 - 70 mph in drive or coast modes under moderate to
wide open throttle.
- Frequency = # Pinion teeth x Driveshaft Speed in RPM / 60.
- Caused by gear transmission error (TE), which is the difference between
the actual position of the output gear and the position of a theoretical or
“perfect gear”, measured in “arc-second”.
Design Principles – Structureborne NVH
Excitation Source
Requirement Cascade
- Vehicle level: Driver audible target in dB(A) and 0.5 micron pinion nose vibration.
- System level: 12 arc-sec.
- Component level: 7 arc-sec at nominal mesh position (single flank).
Noise factors:
- Manufacturing: gear cutting, heat treat and lapping variation.
- Assembly: Pinion and differential shiming
- Gear mesh deflection, gear wear
- Driveline modal response (torsional and bending modes)
Development Flow
- <Program Target Confirmed> Define “health chart” Axle whine cascade
(CAE).
- <M1 Design Judgment> Verify targets are compatible (CAE)
- <Final Design Judgment> Single Flank TE, Axle TE and Vehicle NVH
measurements
Design Principles – Structureborne NVH
Excitation Source
Options to reduce whine at the source
- Increase contact ratio.
- Fine tooth combination
- Long tooth face width
- More spiral angle
- Reduce gear mesh deflection
- Increase component stiffness (bearings, differential case, carrier).
-
Reduce gear wear
- Reduce input torque, sliding velocity
- Improve lubrication
- Reduce gear manufacturing tolerance.
- 3D hypoid gear hobbing is industry standard for high volume automotive
applications.
- Reduce tolerance on hard finishing (lapping).
- Reduce assembly tolerances for pinion and ring gear mounting distances.
- Measure gap and shim to compensate (build to pattern).
- Use threaded adjuster to position ring gear in proper mesh
- Measure all components critical dimensions prior to assembly and shim to
achieve proper stack (build to position).
-
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Structureborne NVH
Path - Isolation Strategy
Mechanism:
• Path transfers mechanical energy in the form of
forces or vibration. Normally path is
mathematically simulated by spring or damper.
Design principle(s):
• Force or Vibration is normally controlled through
maximizing transmission loss.
– In the frequency range of system resonance, controlling
damping is more effective for maximizing transmission loss.
– In the frequency range outside of the system resonance,
controlling stiffness or mass is more effective for maximizing
transmission loss.
*
Design Principles – Structureborne NVH
Path - Isolation Strategy
Design action(s):
• Maximize damping in the frequency range of
system resonance by using higher damped
materials, (e.g. hydraulic engine mounts).
Tuned damper can also be used.
• Adjust spring rate (e.g. flexible coupler or
rubber mount) to avoid getting into resonant
region and maximize transmission loss
• If nothing else works or is available, use dead
mass as tuning mechanism.
*
Design Principles – Structureborne NVH
Path - Isolation Strategy
Tuning and Degree of Isolation
By moving
natural frequency
down for this
system it
increased
damping at 100
Hz
*
NVH Design Principles
Airborne NVH
Source
Path
Radiated/Shell Noise
Acoustic Attenuation
Tube Inlet/Outlet Noise
Acoustic Attenuation
Impactive Noise
Acoustic Attenuation
Air Impingement Noise
Acoustic Attenuation
Responder
Environment
Sensitivity
Structure-borne
NVH
Customer
Excitation
Source, Energy
Input
Isolation
Stiffness
Structure
Sensitivity
Isolation
Damping
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Mechanism:
• Structural motion that results when input force
causes the structure to respond at its natural modes
of vibration.
Design principle(s):
• Reduce the amplitude of structural motions by
– controlling stiffness and mass (quantity and
distribution),
– managing excitation input locations
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Design action(s):
• Select architecture that can provide the maximum
structural stiffness by properly placing and
connecting structure members.
• Use damping materials to absorb mechanical energy
at selected frequencies.
• Distribute structural mass to alter vibration frequency
or mode shape.
• Locate excitation source at nodal points of structural
modes.
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Body Modes and Body Architecture
How Does Architecture Influence Body NVH?
● Governs the way external loads are reacted to and distributed throughout the
vehicle
● Affects Stiffness, Mass Distribution & Modes
What Controls Body Architecture?
● Mechanical Package
● Interior Package
● Styling
● Customer Requirements
● Manufacturing
○ Fixturing
○ Assembly Sequence
○ Stamping
○ Welding
○ Material Selection
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Body Modes and Body Architecture
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Body Modes and Body Architecture
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Body Modes and Mass Distribution
Effect of Mass Placement on Body Modes
• Adding mass to the body lowers the mode frequency
• Location of the mass determines how much the mode frequency
changes.
*
Design Principles – Structureborne NVHStructure
Sensitivity Strategy
l
Metrics used to quantify
body structure vibration
modes :
● Global dynamic and static
response for vertical / lateral
bending and torsion
● Local dynamic response (point
mobility – V/F) at body
interfaces with major
subsystems
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Guideline: Body Modes & Force Input
Locations
Where
Possible Locate Suspension & Powertrain
Attachment Points to Minimize Excitation:
– Forces applied to the body should be located near nodal
points.
– Moments applied to the body should be located near
anti-nodes.
*
Design Principles – Structureborne NVH
Structure Sensitivity Strategy
Conclusions:
• The body structure is highly interactive with other
subsystems from both design and functional
perspective. Trade-offs between NVH and other
functions should be conducted as soon as possible.
• Once the basic architecture has been developed, the
design alternatives to improve functions become
limited.
Guiding Heuristic - Know what to get right first and what can
be tuned later
Design For NVH (DFNVH)
•
•
•
•
•
Introduction to NVH
DFNVH Heuristics
DFNVH Process Flow and Target Cascade
DFNVH Design Process Fundamentals
Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
Wind Noise Example
• Any noise discernible by the human ear
which is caused by air movement around the
vehicle.
• Sources: aerodynamic turbulence, cavity
resonance, and aspiration leaks.
• Paths: unsealed holes or openings and
transmission through components.
*
Wind Noise Example
Wind Noise Target Cascade Diagram
Vehicle level
Wind
Noise
Transmission
Los
s
Excitation
Source
s
Seal
s
Antenna /
Accessorie
s
Open
Windows /
Sunroo
f
Mirror
Shap
e
Green
House
Shap
e
Dynamic
Sealin
g
Aspiration
Leak
s
Door
Syste
m
Stiffnes
s
Glass /
Panels
Static
Sealin
g
*
Wind Noise Example
*
Wind Noise Example
Aerodynamic excitation
•
•
•
•
•
•
•
A-pillar vortex
Mirror wake
Antenna vortex
Wiper turbulence
Windshield turbulence
Leaf screen turbulence
Windshield molding
turbulence
• Exterior ornamentation
turbulence
• Cavity resonances
• Air flow induced panel
resonances
• Air extractor noise ingress
• Door seal gaps, margins
and offsets
*
Wind Noise Example
Aspiration leakage
• Dynamic sealing
– Closures
• Dynamic weatherstrip
• Glass runs
• Beltline seals
• Drain holes
– Moon roof
• Glass runs
– Back-lite slider
• Glass runs
• Latch
• Static sealing
– Fixed backlite
– Exterior mirror seal
– Air extractor seal
– Moon roof
– Door handle & lock
– Exterior door handles
– Windshield
– Trim panel & watershield
– Floor panel
– Rocker
*
Design For NVH (DFNVH)
• Introduction to NVH
• DFNVH Design Process Fundamentals
• Key DFNVH Principles
– Airborne NVH
•
•
•
•
Radiated/Shell Noise
Tube Inlet/Outlet Noise
Impactive Noise
Air Impingement Noise
– Structure-Borne NVH
• Wind Noise Example
• 2002 Mercury Mountaineer Case Study
• Summary
*
Design For NVH
2002 Mercury Mountaineer
SUV –Case Study
•Creating a quieter and more pleasant cabin
environment, as well as reducing overall noise,
vibration, and harshness levels, were major drivers
when developing the 2002 Mercury Mountaineer.
“The vehicle had more than 1,000 NVH targets, that fell
into three main categories: road noise, wind noise, and
powertrain noise. No area of the vehicle was immune
from scrutiny”– Ray Nicosia, Veh. Eng. Mgr.
*
Design For NVH
2002 Mercury Mountaineer
SUV
The body structure is 31% stiffer than previous model, and exhibits a 61%
improvement in lateral bending. Laminated steel dash panel, and magnesium
cross beam were added.
*
Design For NVH
2002 Mercury
Mountaineer SUV
• Improved chassis rigidity via a fully boxed frame with a 350%
increase in torsional stiffness and a 26% increase in vertical and
lateral bending.
*
Design For NVH
2002 Mercury
Mountaineer
“Aachen Head” was used to improve Mountaineer’s Speech Intelligibility Rating to a
85%. A rating of 85% means passengers would hear and understand 85% of
interior conversation. Industry % average for Luxury SUV is upper 70s.
*
Design For NVH
2002 Mercury
Mountaineer
Body sculpted for less wind resistance with glass and door edges
shifted out of airflow.
*
NVH in EVs
• NVH perceived quality and characteristics inherent to vehicle
branding have been well defined and tuned over the years,
based on combustion engine sound sources.
• With the evolution of electric vehicles, however, this applied
NVH knowledge has unfortunately not translated well to electric
vehicles.
➢ Customer expectations for electric vehicle sound quality
have not been well defined.
➢ The lack of refined requirements, coupled with more
stringent environmental and federal regulations, has made it
difficult for NVH engineers to tune to their system attribute.
➢ Is NO pass-by noise acceptable? What about pedestrians,
who may inadvertently step in front of an oncoming EV?
*
NVH in Evs (Cont.)
•
Based on new sound sources, it is necessary to
➢ Review the foundation diagrams to understand system
interactions, and external factors
➢ Conduct customer research to determine customer
expectations for sound quality and powertrain NVH
➢ Develop targets based on customer feedback.
*
Electrical Noise Prevention for
Internal Combustion and emerging
Electric Vehicles
AEV 5070 Class Presentation
M. Lunn
Customer Expectation of Vehicles – SE
Requirements – Quiet, Green with features
• Requirement of customer for any vehicle is quiet
and no “unassociated” noises or undesirable
noises
• Fuel Economy for IC engines and Effective Range
for EV’s wants efficient use of power, rule of
thumb is 0.04 mpg/A.
• Features to heat interior, operate lighting, cool
engine area(EV’s have cooling fans and liquid
cooled electronics also), blow air in interior,
pump fuel and control suspension use electrical
power.
Electrical power control – Pulse Width
Modulation challenges no noise!
• Inefficient power control is a A/C blower motor
with variable motor control. DC current to a
motor sinks voltage in a MOSFET load(waste).
Excess energy is sunk to limit speed, heat is
excess from engine for IC.
• Efficient power control is Pulse Width modulated
heater(PTC heating elements like toaster) with no
wasted energy and PWM motor control.
• Pulse Wi is a square wave signal for power with
variable duty cycle(positive time/ period), allows
variable control. Try an example on next slide!
Example of Electrical control – DC and
AC simulation – Sine waves shown.
Packaging diagram of PWM signals
with audio noise issue on heated seats
Note corouting of PWM heated seats with audio
Single ended PWM
Load on the heated seats
Is issue.
Prior to schematics or
Package any single circuit
With PWM current over
___ Amps is suspect
For noise to audio.
Analysis is easy, if PWM
Enters the body with
Audio then its possible to
Have noise
How noise is induced on a device or
wires by a PWM or time varying signal
As built route to right side, separate
power and and ground, noise heard
Top Yellow signal is
current probe on
the heated seats at
10 mV/A and range
of 9.3 A, Delta time
is 200 HZ, 5 ms.
Bottom is LH front
speaker wires with
noise pulse on rise
and falls of the
current. This is on
line level output,
through the ANC,
then on speaker
amplified by AMP.
As built route to right side, separate
power and ground, noise heard
• Heated seat current is on the audio speaker as shown.
PWM square waves are sum of Sine
waves – these make noise!
Systems Engineering V – how to
prevent noise issues?
• These noise issues are usually detected late in vehicle testing,
how to do early in development?
• The single V
does not use the
analysis early to
find noises from
experience, fixed
in late changes
Is pattern.
Better to prevent
In design left side
vs. V&V on right side!
How to Prevent noise issues – how to
implement?
• A double V approach is a solution – requires the CAE
analytical modeling tools be used, time provided and
staffing supported to allow application and prevent.
– This is not a practice I see in the industry but electrical CAE
and EMC tools are capable! (Mentor, Dassault, etc.
• Why not adopt these tools?
– Data for circuits, components and loads in the
environment of in house, regional and supplier designs
does with staffing, time provided does not allow these
tools to be used.
• Most solutions are fast to implement if program
supports cost/vehicle needed.
– Cost less overall than the analytical approach???
Package Diagram of PWM signals with
prevent action – no noise heard
• The PWM load is twisted with power to get
out of the audio circuit path and cancel fields.
LH routing and twisted power and
ground – no noise heard
Same top yellow trace
for current probe at
10mV/A and 10.8 A,
200 Hz.
LH speaker shows
almost no noise on the
speaker circuits! No
noise heard by
customer.
LH routing and twisted power and
ground – no noise heard
• CHB purple LH speaker is very low, not following current.
Overlay on engine compartment – no
no noise heard and heated seats on
• CHA yellow is seat current, CHB purple is not used.
Overlay on engine compartment – no
no noise heard and heated seats on
- First(200), third(600) and fifth(1000)
harmonics shown.
Why is this significant to EV’s in
future!
• PWM Loads are increasing for EV’s from IC vehicles!
IC engine
EV future
Frequency
Cooling fans – relay power 600W
PWM 200 W20kHz above audio
Power Steering- 1000 W peak
1000 W peak
20KHz above audio
(audible harmonic in the AM and FM band on any car I know of!)
Heated seats - 120 W
120 W
200 Hz audio and AM
Heated interior – 900 W constant
900W constant
100 Hz in Audio and AM
(within 12 inches of audio unit for inverse squared 1/r^2 relationship of fields !!)
Active Suspension - 9A/108W)
9A/108W) 1000 Hz
(TBD as of yet)
Fuel Pump(ERHV) - 10A
10A
9600 Hz in audio, AM, FM
Start/Stop on Engine – large changes large changes
pulse but spikes heard
A/C load - 10 A for comp clutch
50 A for compressor
(TBD)
• Not using PWM will increase loads and decrease range of batteries or fuel
economy! Approximately 0.04 MPG per A and range anxiety.
• Have you been in an EV or start/stop IC vehicle, noticed the only sound can be
a tire noise on surface and brake caliper release! Switch travel is noise!
Transition to rolling or start and you have pulse of current, potential noise.
Requirements of Vehicle designs on noise
and EMC with Fuel Economy increases
• Vehicles for IC engines have been mostly sheet metal for
cost and forming, assembly.
– Also provides ground plane and E field shielding!!
– Works until fuel economy goes to 54.5 MPG
• To support future MPG rules the weight and structure may
change to alternatives
– Aluminum is not as good a ground or shield in a body
construction.
– Plastic or carbon fiber is not conductive or a shield.
All the alternatives make electrical interactions harder to
prevent and more expensive!!
http://www.bloomberg.com/news/2011-06-14/bmw-carbonlets-vehicles-follow-bicycle-road-to-lightness-cars.html
Questions & References and links
• PHET AC and DC circuits:
http://phet.colorado.edu/en/simulation/circuitconstruction-kit-ac-virtual-lab
• PHET Faradays Electromagnetic lab:
http://phet.colorado.edu/en/simulation/faraday
• PHET Fourier: making waves:
http://phet.colorado.edu/en/simulation/fourier
• All PHET Simulations, these are very useful and free http://phet.colorado.edu/
• Also of interest for general knowledge and explainations http://www.khanacademy.orgAlso of interest for general
knowledge and explainations http://www.khanacademy.org/
• I use these to explain ideas and issues vs. lots of words and
“you don’t understand this”. Try with your kids!
DFNVH Summary
• Preventing NVH issues up front through
proper design is the best approach –
downstream find-and-fix is usually very
expensive and ineffective
• Follow systems engineering approach – use
cascade diagram to guide development target
setting. Cascade objective vehicle level
targets to objective system and component
targets
*
DFNVH Summary
• Use NVH health chart to track design
status
• Always address sources first
• Avoid alignment of major modes
• Use the Source-Path-Responder
approach
*
References
• Ford-Intranet web site:
– http://www.nvh.ford.com/vehicle/services/training
•
•
•
•
•
General NVH
NVH Awareness
NVH Jumpstart
NVH Literacy
Wind Noise
• Handbook of Noise Measurement by Arnold P.G.
Peterson, Ninth Edition, 1980
• Sound and Structural Vibration by Frank Fahy,
Academic Press, 1998
• http://www.needs.org - Free NVH courseware
*
References
• "Body Structures Noise and Vibration Design Guidance",
Paul Geck and David Tao, Second International Conference in
Vehicle Comfort, October 14-16, 1992, Bologna, Italy.
• "Pre-program Vehicle Powertrain NVH Process", David Tao,
Vehicle Powertrain NVH Department, Ford Advanced Vehicle
Technology, September, 1995.
• Fundamentals of Noise and Vibration Analysis for
Engineers, M.P. Norton, Cambridge University Press, 1989
• Modern Automotive Structural Analysis, M. Kamal,J. Wolf Jr.,
Van Nostrand Reinhold Co., 1982
• http://www.nvhmaterial.com
• http://www.truckworld.com
• http://www.canadiandriver.com
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