ODIN: A Retrospective on
Integrated System
Design for EV
Dr. Melanie Michon
15th September 2016
Contents
• Targets for ODIN
• Setting up the ODIN Consortium
• Design Challenges
• Lessons Learned
• Project Update
• Summary
Slide 2
CONFIDENTIAL
© Copyright 2016
Initial Targets for ODIN (2011)
• Focus subcompact/compact EV‘s with 65kW peak power (30s)
• Integration of e-machine, power electronics and gearbox into one
shared housing
• Validation of high speed concepts
o
Not just a “me-too” design
• Up to 50% cost reduction compared to reference powertrains
• Avoidance of rare earth metals
o
Switched Reluctance Motor
Slide 3
CONFIDENTIAL
© Copyright 2016
Romax work on EV’s prior to consortium selection
2007 2008 2009 2010 2011 2012 2013 2014
E-AWD Rear
Gearbox
Design
Support
HEV efficiency
optimisation
HEV APU control
optimisation
2015
2016
EV NVH opt. at
concept design x2
EV gearbox & motor noise, thermal & efficiency optimisation
EV gearbox
HEV gearbox
EV
design support
efficiency durability, NVH and HEV gearbox & motor AWD bearing EV FDU gear
EV concept selection
improvement efficiency opt.
analysis
whine analysis
design and control opt.
HEV concept, detail design
and system integration
PTU for
HEV
EV gearbox design
optimisation
HEV EDU design
assessment
EV gearbox
concept design
HEV NVH
optimisation
EV
Differential
Design and
Analysis
Off-road e- CVT noise
troubleshooting
Slide 4
EV gearbox
design process
EV gearbox design Hybrid Vehicle
Gearbox
assessment
Optimisation
EV NVH
troubleshooting
CONFIDENTIAL
© Copyright 2016
Consortium Set Up
system development
• Kick off September 2012
gear
e-components
lubricant
Slide 5
casting
sim mechanic
demo car
CONFIDENTIAL
© Copyright 2016
Design Challenges
• What layout is best? How many stages?
• What motor maximum speed/overall ratio?
• How efficient will the drivetrain be? How do we make it more
efficient?
• Can we integrate cooling of motor/gearbox?
• How do we design for low noise?
Slide 6
CONFIDENTIAL
© Copyright 2016
Which layout is best?
• Assessment qualitative rather than quantitative
Slide 7
CONFIDENTIAL
© Copyright 2016

Ratio limits

Packaging
Second stage ratio
Overall Ratio? Maximum Speed? Efficiency?
?
Innovation
?
Overall ratio
Smaller, lighter, cheaper
electrical machine
Higher gear ratio
Gearbox efficiency
validated at
conventional speeds
but not high speeds
Motor efficiency
calculations slow, esp.
SRM
Design decision: R&D cannot be “me-too”. The project needs to set a challenge, even at the risk of failure
Slide 8
CONFIDENTIAL
© Copyright 2016
Innovation Highlights
•
System Simulation
o
•
Power electronics
NVH simulation in early development stages
E-Motor
Cooling & Lubrication
o
•
One cooling and lubrication circuit (oil)
Switched Reluctance Motor (SRM)
o
•
High speed (22.5K RPM); NVH optimized design and control
Power Electronics
o
High switching frequency
o
Highly dynamic current sensing
•
Main cover
Gear Box
Gear set
o
High efficiency despite high speed (max ratio for 2 stages)
o
NVH optimized layout
•
Housing and integration
o
Synergies by high integration
Main housing
 Main focus: optimize efficiency, NVH, driveability, packaging and costs
Slide 9
CONFIDENTIAL
© Copyright 2016
Development of Integrated Cooling
• Thermal Simulation carried out by Romax
•
System Level: 1D system model study of layouts
•
Integrated Cooling: Through system heat sharing, enables efficiency gains for the gearbox achieved on cold
start performance
Non
Integrated
Slide 10
Integrated
Cooling
system
CONFIDENTIAL
© Copyright 2016
Shared cooling circuit development
Philosophy of dry sump topology:
•
The e-Motor cooling requirements dictate the major cooling flow demand
•
The power electronics require consistency of temperature for best reliability
•
Gearbox cold running performance can be improved, through use as an alternate heat dump to the radiator
Slide 11
CONFIDENTIAL
© Copyright 2016
Development of Lubricant
1. High load, low speed
Implementation of variable friction
coefficient over LoA, Mixed-EHL Model
2. Low load, high speed
“Designing the oil for the machine
and the machine for the oil”
Slide 12
CONFIDENTIAL
© Copyright 2016
Lubricant effect on efficiency in RomaxDESIGNER
• 2 lubricants with identical viscosities investigated for 2-stage EV gearbox
ISO standard (ISO TR14179-DE) suggests identical
performance
FVA345 method enables differentiation of lubricants
Slide 13
CONFIDENTIAL
© Copyright 2016
How to “Design for Low Noise”
• Predict noise at a time where it can be minimised
• Need for rapid design-analyse-assess-redesign iterations: new electrical machine NVH capability

No housing, but complete with
driveshaft and vehicle definition

System Concept
Sum total power through bearings
System test
System Detailing/
Sub-system design

Basic housing design

Mount stiffnesses from
reference data
Sub-system test
Sub-system Detailing/
Component Selection
Component
Detailing
Component Test
Slide 14
CONFIDENTIAL
© Copyright 2016
NVH Step 1: Initial concept assessment for NVH performance
 Unique capability to assess NVH performance for concept design
System test
System
Concept
System
Detailing/ Subsystem design
Sub-system test
 Identify potential NVH issues early – Right First Time design
Sub-system Detailing/
Component Selection
Component
Detailing
Component Test
Gearbox (SOURCE)
Bearing 2
Bearing j
 Acoustic power transmitted through bearings
 Powertrain definition, no housing definition
 Representative model of generic housing is used
Bearing 1
Bearing n
Sound pressure at
a given location
Slide 15
CONFIDENTIAL
© Copyright 2016
Method Validation
Vibratory force (N)
Vibration velocity (m/s)
No Housing
Acoustic Power Transmitted Through
Bearings in 0-5000 Hz band (mW)
21.6 mW
Significantly
off
4.8 mW
Generic
Housing
Transmitted acoustic
powers are very close
Full Model
4.5 mW
Slide 16
CONFIDENTIAL
© Copyright 2016
NVH Step 2: Concept Housing and unit excitations give indication of
dominant response frequencies for gear and e-machine excitations
System test
System
Concept
System
Detailing/ Subsystem design
Sub-system test
Sub-system Detailing/
Component Selection
Component
Detailing
Component Test
Front Mounts
Rear Mounts
Slide 17
CONFIDENTIAL
© Copyright 2016
Identify potential design actions from the simulation:
“Breathing” Mode at 13000 RPM
• Frequency and noise radiation through
motor end plate matches with
experience
• Design Action:
o
Design rib patterns to reduce
response
Slide 18
CONFIDENTIAL
© Copyright 2016
NVH Step 3: Detailed Housing and calculated excitations
System test
System
Concept
System
Detailing/ Subsystem design
Sub-system test
Sub-system Detailing/
Component Selection
Component
Detailing
Component Test
• Housing designed based on guidance from concept simulation
• Further guidance based on detailed simulation
Slide 19
CONFIDENTIAL
© Copyright 2016
6 Mode, 12Cycle – 1400N
6 Mode
16
1
Detailed housing at 4761 Hz (23808RPM)
17
18
2
3
15 14
5 6
4
13
12
11
8
9
7
10
Radial Force- 6 Mode_12cycle Frequency (Hz)
800 1600 2400 3200 4000 4800
0
5.0E-03
Reduction Factor = 0.36=8.81dB
4.0E-03
Velocity (m/s)
Radial Forces
3.0E-03
2.0E-03
1.0E-03
0.0E+00
0
0
4000
25
8000
16000
Input Shaft (RPM)
20000
75
100
125
50
Vehicle Speed (km/h)
Air-6Lobe_12Cycle
Slide 20
12000
24000
150
Old_Air-6Lobe_12Cycle
CONFIDENTIAL
© Copyright 2016
0 Mode, 36Cycle – 190N
0 Mode
17
18
2
Concept housing at
8236Hz (13728RPM)
Radial Force- 0 Mode_36cycle Frequency (Hz)
10
1
3
Detailed housing at
7373Hz (12288RPM)
0
2.5E-02
2400
4800
7200
9600 12000 14400
Reduction Factor = 0.22=13.22dB
2.0E-02
Velocity (m/s)
Radial Forces
1.5E-02
1.0E-02
5.0E-03
0.0E+00
0
4000
0
25
8000
Input Shaft (RPM)
16000
20000
75
100
125
50
Vehicle Speed (km/h)
Structure-0Lobe_36Cycle
Slide 21
12000
24000
150
Old_Structure-0Lobe_36Cycle
CONFIDENTIAL
© Copyright 2016
Significant reduction in response achieved for gear and e-machine
excitations
Response to transmission error
Response to radial force
Slide 22
CONFIDENTIAL
© Copyright 2016
Test Results: Impact of Lubricants on Efficiency
• Extensive testing of lubricants to confirm the process
“Designing the oil for
the machine and the
machine for the oil”
Slide 23
CONFIDENTIAL
© Copyright 2016
Test Results: Efficiency
• ODIN gearbox showed better efficiency than baseline gearbox
(a current EV gearbox) at all speeds and loads
Slide 24
CONFIDENTIAL
© Copyright 2016
Other test results
…. and design decision
• Gearbox design for efficiency successful
• NVH test run with very different model set up and boundary conditions,
so no correlation possible
• Switched Reluctance Motor efficiency did not meet design targets,
despite novel control strategy development
• By the end of Loop 2 the price of rare earth metals less problematic
o
Economic justification for SRM had reduced
• Decision for Loop 2:
Go with Induction Motor, similar gearbox to Loop 1
Slide 25
CONFIDENTIAL
© Copyright 2016
Lessons Learned
• Design of integrated electro-mechanical drivetrains brings new
uncertainties
• Difficult to develop new design/simulation process and new design at
the same time. Check the “technological building blocks” are in place
• However, use of up-front simulation (e.g. NVH) can yield great benefits
• Close collaboration between motor and gearbox design activities
essential
• Engineering decisions still subject to economic influences
Slide 26
CONFIDENTIAL
© Copyright 2016
Project Update
• Motor changed to Induction Motor by Bosch
• Maximum motor speed changed to 15,500 RPM
• Gearbox design process from Loop 1 replicated, made use of
successes for efficiency, lubricant design
• Methods for design for noise, thermal in an integrated system
carried over
• Testing started in the last couple of weeks… watch this space!
Slide 27
CONFIDENTIAL
© Copyright 2016
Summary
• Romax has seen at first hand the challenges in a design project,
with cross-industry collaboration (motor, gearbox, vehicle)
• Much R&D work has been kicked off based on limitations of
the current state-of-the-art for design of EV drivetrains
• Understanding of the interactions across the electromechanical drivetrain is essential for design success
Slide 28
CONFIDENTIAL
© Copyright 2016