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TRANSCRIPT
Romax electrical machine
NVH analysis
A workshop
Dr. Melanie Michon
September 2016
Slide 2CONFIDENTIAL
© Copyright 2016
Agenda
• System approach to NVH analysis in electrified drivelines
• Overview of new electrical machine NVH software capabilities
o Electrical machine structural modeller
o Electrical machine dynamic analysis
• Demo of new electrical machine NVH software capabilities
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SYSTEM APPROACH TO NVH
ANALYSIS
For electrified drivelines
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Background
• Electrical machines are a critical part of many rotating machines
• Electrical machines are the future (and present) of automotive technology
• Electrical machines also appearing in many other applications, e.g.
o Wind turbines
o Marine
o Rail
o Aerospace
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NVH simulation of the complete electro-mechanical driveline to identify
system interactions from the start
Motor in isolation is okGearbox in isolation is ok
Put them together: there is a problem!!
PE E-motor
Gearbox
Experience shows that is it critical to
consider the electric machine and
gearbox together as part of the same
system
In this way electro-mechanical
interactions can be captured from the
start – target Right First Time design
This is particularly true for NVH
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Simulating NVH in an E-Powertrain
Radiated Noise = Excitation x Dynamic Response
MotorsEM Simulation -> Torque ripple
and radial forces
Simulation -> Reduction
System Response: Design
recommendations
Romax method for electromechanical system: True design for low noise
Conventional method: Design for low noise is “Design for Minimum Excitation”
System Response:
Simulation -> Reduction
Romax method for gears: Reduce system response
GearsLTCA -> TE
Simulation -> Reduction
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Motor noise mechanisms
• 1) Torque ripple
o Equal and opposite torque on rotor and stator
• 2) Radial forces
o Act between rotor and stator
o Forces on rotor cancel out
o Forces on stator generate complex force
shapes
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eNVH analysis – motor simulation
EM simulation of motor
in 3rd party FEA package
Obtain excitation
for stator forces …
.. and for torque ripple
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Frequency domain analysis of excitation data
8th harmonic 16th harmonic 24th harmonic
Harmonic
analysis
Complex stator radial force shape
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System response including mechanical and electrical
components
• Motor and gearbox in a single system
model
o Transfer path of torque ripple through
gearbox
• All shafts, bearings, gears, housing in
a single model
• Frequency domain solution for speed
and insight
PE
E-motor
Gearbox
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Unique analysis of electro-mechanical system interactions
H=48, 8472 rpmH=48, 936 rpm
1st stage, 8208rpm2nd stage, 6516rpm
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0 Mode
1
2
18
10
17
3
0.0E+00
5.0E-03
1.0E-02
1.5E-02
2.0E-02
2.5E-02
0 4000 8000 12000 16000 20000 24000
Velo
cit
y (
m/s
)
Input Shaft (RPM)
Structure-0Lobe_36Cycle Old_Structure-0Lobe_36Cycle
0 2400 4800 7200 9600 12000 14400
Radial Force- 0 Mode_36cycle Frequency (Hz)
0 25 50 75 100 125 150Vehicle Speed (km/h)
Reduction Factor = 0.22=13.22dB
Detailed design based on guidance from NVH simulation:
Noise Simulation becomes Noise Reduction
• Radial force excitation on electrical machine
• NVH analysis during concept design was used
to guide the detailed design
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NVH Simulation within the Design Process
• Predict noise at a time where it can be minimised
System Concept
Component
Detailing
Component Test
System Detailing/
Sub-system design
System test
Sub-system Detailing/
Component Selection
Sub-system test
No housing, but complete with
driveshaft and vehicle definition
Sum total power through bearings
Basic housing design
Mount stiffnesses from
reference data
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• Simulation of complete E-Powertrain
• Excitation from motor and gearbox sources
Simulation used in the design process to AVOID problems and
not just SOLVE them when they have occurred
Summary on eNVH analysis
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ELECTRICAL MACHINE NVH
New software capabilities
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What do the new modules do
• You can
o Create an electric machine assembly
o Create a concept stator component
o Import motor excitation data from 3rd party tools
o Define imbalance excitations
o Calculate whole system response to those excitations alongside usual
gear excitations
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Two New Modules
Electrical Machine Structural Modeller Electrical Machine Dynamic Analysis
Allows you to:
• Add “Electrical Machine” assemblies in the
model
• Create “Concept Stator” components and link
them to Electrical Machine assemblies
• Mesh a stator structure and conformally mesh
it to an FE shaft representing a stator housing
• Apply static forces and torques to stator and
rotor
Allows you to:
• Pre-process externally defined excitation data
• Define electrical machine dynamic excitations
• Have excitations that vary with speed
• View and export vibration response to these
excitations
Pre-reqs: Structural Flex, FE Solve Pre-reqs: Electrical Machine Structural
Modeller, System Dynamic Analysis
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Workflow
• Create Romax model of rotating parts and housing
• Create electrical machine assembly
• Mount rotor and stator to shaft and single axis housing as appropriate
• [Define and mesh concept stator] optional
• Define stator node connections
• Calculate electric machine excitations in 3rd party software
• Import excitation data
• Define any imbalances
• Run analysis
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STRUCTURAL MODELLER
For Electrical Machines
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Electric machine definition
• Comprises rotor and stator definition
• Both must be mounted before they can be edited
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Creating the rotor assembly
• The rotor is mounted on the input shaft
• The rotor is represented by its mass and
inertia
• Acts as Power Load for static analysis,
and excitation node for Dynamic Analysis
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Dynamic unbalance
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Creating and meshing a concept stator
• If the structure of the stator is not already
included in the housing mesh, a parametric
concept stator can be defined
• This can be meshed inside RxD and automatically
connected to the housing by a conformal mesh
• The housing should have a cylindrical bore where
the stator will fit
• The mesh from the inside of the housing bore is mapped on to the outer diameter of
the concept stator so that the meshes can be joined
• The benefit of this is that different machines can easily be analysed in the same
housing (although the housing must be re-condensed)
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Concept stator wizard
• Define stator
parameters:
o Diameters
o Slot/tooth
dimensions
o Number of slots
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Concept stator wizard
• Find housing nodes
at stator outer
diameter
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Concept stator wizard
• Mesh stator with
conformal nodes on
outer diameter
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Concept stator wizard
• Stator conformally meshed
with housing into single FE
component
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Connecting stator to FE housing
• Stator tooth connections
defined in node connection
dialog
• These RBE3 connections are
where the reaction torque
and motor excitations are
applied
• This step needs to be done
even if a concept stator is
not used
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Static Force analysis
• Static forces from the electrical machine, i.e. DC torque and radial force,
can be defined manually, or populated from excitation data
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DEMO
Electrical Machine Structural Modeller
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NVH ANALYSIS
For Electrical Machines
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Importing excitations
• Motor excitations are calculated by 3rd party tools
• Torque ripple and radial force excitations are
imported into RomaxDesigner
• These are pre-processed into individual harmonics so
that the NVH behaviour can be analysed
• Excitations are calculated at different torque levels, for discrete speeds – typically 2-3
torque levels in drive and in coast
• The harmonics are interpolated across the speed range to give sufficient speed
resolution for the analysis
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Electromagnetic FEA software packages
• Motor excitation data is calculated by 3rd party tools
• Any electromagnetic FEA software can be used to calculate the excitation data
• For example:
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Example: Workflow of calculating the excitations in
Ansys Maxwell
• Draw e-machine in Ansys Maxwell
• Add appropriate boundary
conditions, magnet orientations,
phase windings and turns
• Define rotor band for torque
calculation
• Define tooth sections as separate
entities to calculate excitations
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Select each tooth and assign force individually
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Define current excitation
• Define phase current excitation
for given torque/ speed
condition
• Analyse transient model
𝐼𝑎 𝑡 = 𝐼𝑝𝑒𝑎𝑘 sin ω. t + θ
𝐼𝑏 𝑡 = 𝐼𝑝𝑒𝑎𝑘 sin ω. t + θ −2π
3
𝐼𝑐 𝑡 = 𝐼𝑝𝑒𝑎𝑘 sin ω. t + θ +2π
3
ω = 𝑟𝑝𝑚360
60𝑝𝑜𝑙𝑒 𝑝𝑎𝑖𝑟𝑠 ∗
𝜋
180
Θ= gamma angle for given torque/speed condition
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Plot motor torque and export to csv
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Plot forces on each tooth
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Export tooth forces to csv file
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Importing excitations
• Excitation data is imported through the pre-processor in the electrical
machine assembly
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Importing excitations
• In this example 4 speeds are defined
• The excitation data exported from external FEA can be copied directly from spreadsheet if excitation data is
provided for all teeth, for one rotation
o Where periodicity has been used to speed up the FEA analysis, it is up to the user to pre-process the data
to create a full data set
• This process will be more automated in future releases
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Importing excitations
• Imported excitations can be visualised
• Dominant harmonics are extracted
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Unbalance excitations
• A shaft that is not balanced exerts a rotating radial force on
the shaft proportional to the square of the rotation speed
• Electric machines can run at very high speeds and these
forces can be large and also be at frequencies which are
audible
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Speed-dependent general excitationsRequired for electrical machines
• The electric machine excitations have an amplitude which varies with frequency or
speed
• Users can now define general excitations that vary with speed
• Electric machine excitations are a special case of general excitation that are grouped
together for convenience
• Speed dependent general excitations are available in the Advanced Whine module.
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Speed-dependent general excitations
Required for electrical machines
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DEMO
Importing and Pre-processing the Excitations
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Calculating NVH performance
• Once the electric machine and
excitations are defined then the
vibration response can be calculated
using the advanced whine analysis
• Motor excitations are passed
automatically to the Dynamic
Analysis Results window and are
automatically applied to the rotor
and to each stator tooth
• Motor excitations and imbalance are
shown alongside gear transmission
error
Gear transmission error
Motor excitations
Imbalance
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Calculating the system response
• System response can be calculated in
different ways:
o Response at the mounts
• Assess structure-borne noise
o Response at virtual accelerometer
locations
• Correlate with test data
o Calculation of the Mean Square
Velocity of the housing
• Initial indication of air-borne
noise
o Export to acoustic analysis software
for more detailed analysis
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Response at housing mounts
Differential
mount
Motor mount
Gearbox mount
Select mount
locations
Select excitations
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ODS generation at key frequenciesFor the mount velocity response to 48th Harmonic Radial force & Torque ripple
• Identify most significant excitation
mechanisms and speeds
• Generate ODS (Operating Deflection
Shape) animations at each mechanism
and speed
• Identify locations with greatest response
Peak in response on
motor-end mount
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Define virtual accelerometer locations
• Response nodes are chosen to correspond to accelerometer locations
474710157
9008
19049
8788
1862463816851
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Response at virtual accelerometers
• Response to gear or motor
excitations at virtual
accelerometers
o Correlate to test data
o Identify locations with
highest response
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Dominant response identified in peaksVirtual accelerometer velocity – motor excitation
• Examination of individual virtual accelerometers
• Response to 48th excitation is dominated by motion
at B-end bearing cover
• ODS confirms significant response at this location
H=48, 10 440 rpm
4747
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Calculate Mean Square Velocity on the housing
• Calculate Mean Square
Velocity across all surface
nodes, or a selection of nodes
• Response to e-machine
excitations, imbalance and
gear TE
• Apply A-weighting to
represent non-linearity in
perceived loudness
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Calculate Mean Square Velocity on the housing
• Overlaying Mean Square
Velocity for each excitation
shows relative importance of
each excitation
• Most significant excitations
here are 1st and 2nd stage TE,
and motor 48th order
excitations
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Design recommendationsReducing the excitations: Machine design
• Motor excitations
o 48th harmonic of radial force and torque ripple is most
significant contributor to structure-born and air-born
response
o Electrical Machine pre-processor provides insight in where
to focus electrical machine design improvements to
reduce excitations:
• The amplitude of 48th harmonic of radial force is relatively low
compared to lower harmonics
• The amplitude of 48th harmonic of the torque ripple is high
compared to other harmonics
o Analysis module provides insight in how to reduce system
response to electrical machine AND gear excitations
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System response to e-machine AND gear excitationsAnalysis provides unique insight which allow for reducing system response
• Peaks are identified in system response to e-machine AND gear excitations
• ODS gives great insight in system deflections – allows for design recommendations
H=48, 8472 rpm
H=48, 936 rpm
H=48, 50 rpm
H=40, 10224 rpm
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• Peaks are identified in system response to e-machine AND gear excitations
• ODS gives great insight in system deflections – allows for design recommendations
1st stage, 8208rpm
Unbalance, 12000 rpm1st stage, 6516rpm
Unbalance, 864 rpm
System response to e-machine AND gear excitationsAnalysis provides unique insight which allow for reducing system response
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DEMO
Analysis results
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Benefits
• This unique capability allows engineers to analyse the NVH performance
of the complete electric machine and gearbox system quickly and easily
• Experience has shown that analysing electric machine and gearbox
separately can lead to incorrect design decisions
• This new capability allows problems to be identified and fixed early in
the development phase as part of a Right First Time development
process
• Expect to see much more electric machine capability in Romax software
over the coming months and years