Contents
1.
Group Profile
3
2.
Industrial Collaboration 1996-2004
4
3.
Automotive
3.1
3.2
3.3
3.4
4.
5.
ICE Vehicles
5
Electromechanical Valve Actuation
5
Exhaust Gas Energy Recovery
6
Electrical Torque Booster for Down-Sized Engine
7
Free-Piston Energy Converter
8
Hybrid Vehicles
Mild Hybrid/Integrated Starter-Alternator System
9
Model Predictive Control Applied to Energy Management
10
36V VRLA Battery Module (Based on 2V Spiral-Wound Cells)
11
Installation and Safety Optimised Battery for 42V Application
12
Integrated Modular Drive for Parallel Hybrid Vehicle
13
Electric Vehicles
Zero-Emissions Down-Sized Vehicle
14
Auxiliary Power Unit
15
Flywheel Peak Power Buffer
16
Supercapacitor Peak Power Buffer
17
Anti-Lock Braking/Traction Control
18
Electric Vehicles for Media/Leisure Events
19
Thematic Networks
FABIAN
20
ELEDRIVE
21
Aerospace
Electrohydrostatic Flight Control Surface Actuation
22
Electromechanical Flight Control Surface Actuation
23
‘More-Electric’ Aircraft Engines
24
Fault tolerant drives
25
Healthcare
Reciprocating Air-Compressors
26
Electromagnetic Air-Flow Control Systems
27
Semi-Active Vibrating Isolation of Reciprocating Air-Compressor
28
6.
Consumer Products
Multi-Degree of Freedom Actuators
29
rd
7.
8.
Observer based feedback control of 3 order LCC resonant
converters
30
Low cost energy efficient compressors for refrigeration
31
Industrial
Electromechanical friction surfacing/welding
32
Pulsed field magneto-polariscope
33
Sensorless high-speed brushless DC motors
34
Direct force control of a novel two-phase tubular motor
36
Acoustic emissions from direct torque controlled induction machine
drives
37
EMC, measurements and modelling of power electronics/drive
systems
38
Silicon carbide power electronic devices
39
Marine
Sensorless control of matrix converters for thrusters on deep-sea
ROV’s
40
High speed permanent magnet generator
41
9.
Rolls-Royce University Technology Centre in Advanced Electrical
Machines and Drives
42
10.
Facilities
43
11.
Magnetic Systems Technology Ltd
45
2
1.
Group Profile
The Electrical Machines and Drives Group is based in the Department of Electronic and Electrical
Engineering, which achieved 5* ratings in the 1996 and 2000 Research Assessment Exercises.
The Group undertakes fundamental and applied research on enabling technologies which are likely
to be central to future developments in electrical power engineering. Its strategy, therefore, is to
maintain a balanced portfolio of projects on a broad range of research topics, and to promote pullthrough of its R&D to commercial exploitation and applications encompassing different market
sectors.
The current number and distribution of personnel in the Group is shown in Table 1, whilst Table 2
lists the present academics, Research Fellows and Visiting Researchers.
Academic
Academic-related
Research Fellows
Research Associates
Research Students
Secretarial
Technical
Visiting Researchers
Total
11
1
4
15
24
2
4
3
64
Table 1. Personnel
Academic Staff
Research Fellows/Visiting Researchers
D. Howe – Professor/Head of Group & Director of Rolls-Royce UTC in Advanced Electrical Machines & Drives
Z.Q. Zhu – Professor
G.W. Jewell – EPSRC Advanced Research Fellow
C.M. Johnson – Research Professor
R.E. Clark – RAEng Post-Doctoral Research Fellow
D.A. Stone – Senior Lecturer
S.D. Calverley – RAEng/EPSRC Post-Doctoral Research Fellow
J.B. Wang – Senior Lecturer
A. Turner – Royal Commission of 1851 Industrial Research Fellow
C.M. Bingham – Senior Lecturer
Mr Xu Chen (Zhejiang University)
K. Atallah – Senior Lecturer
Mr Zhigang Sun (Shanghai Jiao Tong University)
P. Stewart – Lecturer
Mr Hua Wei (Southeast University)
S. Long – Lecturer
K. Mitchell - Lecturer
Table 2. Academic staff, Research Fellows and visiting researchers
Figure 1 summarises the research funding which the Group has secured since 1996 together with
data on its journal/conference publications.
Research Funding 1996-2004
Research Publications 1996-2004
Total 1996-2003: £9.34M (2001-present: £4.40M)
45
Sources
40
5.8%
1.8
35
13.7%
1.6
30
1.2
25
6.1%
47.8%
1
20
0.8
15
10
0.6
26.6%
2004
2003
2002
2001
2000
EU
INDUSTRIAL
1999
2004
2003
2002
2001
2000
1999
1998
1997
1996
0
EPSRC
DTI
RS/RAEng
1998
5
0.2
1997
0.4
0
Journals
Conferences
1996
Value (£M)
1.4
Figure 1. Group Funding and Publication Data
In 1992, Professor D. Howe and M.K. Jenkins (then a lecturer in the Group) co-founded Magnetic
Systems Technology Ltd. The company manufactures electrical traction systems for hybrid and
pure-electric passenger cars, as well as systems for use in larger public service and industrial
vehicles.
During 2003, a Rolls-Royce University Technology Unit for Advanced Electrical Machines and
Drives was established in the Group, which also has a NATEC (Northern Aerospace Technology
Exploitation Centre) Agile Technology Unit for Electrical Machines and Drives.
3
2.
Industrial Collaboration 1996-2004
ABB
Linear Drives
Aerospatiale
Lombardini
Auxilec
Lotus
BAe Systems
Magnet Applications Ltd
Bluebird Electric
Mannesmann Sachs
BMW
MD Robotics
British Nuclear Fuels
Merloni Elettrodomestici UK
Carnaud Metalbox
Muirhead Aerospace
CASA
Mitsubishi Electric
Control Techniques
Permotor
Cosworth
Philips Research
Danfoss A/S
PML
DERA
Renault
DENSO
Ricardo
Dunlop Aviation
Rolls-Royce
Eclipse Magnetics
Sensor Technology
European Electrical Steel
SG Magnets
FEV
Shell Research
Fiat
SR Drives
Goodrich
SAFT
Hawker Energy
Slingsby Engineering
HIP
Traxis
Hoganas
TRW Aerospace
Holset Engineering
The Technology Partnership
Huntleigh Healthcare
Unilever
Hydromarine
Urenco
IMRA
VARTA
International Rectifier
Visteon UK Ltd
Johnson Controls
Volvo
Kawasaki Steel
VTT
Leibherr
Zytek Systems
4
3.
Automotive-Related Research Projects
3.1 ICE Vehicles
ELVAS
ELVAS – ‘Electronic Valve Actuation Systems’
EC Project No. GRD1-2000-25251 Contract No. G3RD-CT2000-00363
Partners
¾ JCAE - France (Co-ordinator)
¾ TRW Deutschland GmbH - Germany
¾ CETENASA Fundacion - Spain
¾ University of Sheffield - UK
Funding
Euro 2.7m over 3-years, 2001-2004
Objectives
¾ 15% decrease in CO2 emissions
¾ Substantial engine noise reduction
¾ Novel sensor and actuator topology, and robust control strategy for achieving demanding
dynamic performance requirements
¾ Optimised power consumption
¾ Validate performance on Renault F4R (Laguna/Megane) engine
There is a need to improve car engine efficiency and to reduce fuel consumption in order to
comply with the Kyoto agreement on CO2 emissions reduction. Electromagnetic valve actuation
has been identified as a key technology towards this objective.
Novel Electromagnetic
Actuator Topologies
On-Engine Demonstrator
Application of Multi-objective
Evolutionary Algorithms to Control Design
High Performance Velocity Control
Upper Actuator
Armature
Lower Actuator
Actuator spring
Valve spring
Poppet Valve
INLET
EXHAUST
The University of Sheffield
Electrical Machines & Drives
Research Group
5
6
Electric Starting Torque - with supercapacitor energy storage for boosting
performance of downsized ICE power-trains
EC Project No. NNE5-2001-00100 Contract No. ENK6-CT2001-00531
EST
Partners
¾ FEV Motorentechnik - Germany (Co-ordinator)
¾ SAFT - France
¾ University of Sheffield - UK
¾ Semelab - UK
¾ University of Aachen - Germany
¾ Valeo - France
¾ Renault - France
Funding
Euro 3.5m over 3.5-years, 2001-2004
Objectives
¾ To realise an electrical energy storage system and an electrical machine to boost the
performance of a down-sized internal combustion engine at low engine speeds, so as to
improve the drive-away behaviour
¾ To embody the torque boost system in a vehicle equipped with a down-sized, superboosted
1.8l gasoline engine with a supercapacitor energy storage system and an electrical torque
boost machine, so as to achieve drive-away and acceleration behaviour which is comparable
with that of a vehicle equipped with a 3l engine.
Small, lightweight (down-sized) internal combustion engines with a high specific power by
supercharging can improve fuel consumption by ~30% compared to standard engines with
~40% higher displacement. However, a major drawback is their low torque at low engine
speeds, which results in unacceptable drive-away and acceleration behaviour. By utilising
supercapacitors as a transient energy storage unit an an electrical machine as a short term
torque boost unit, the drive-away and acceleration performance can be improved significantly
and energy recovery is possible during regenerative braking to further improve the fuel
economy.
ICE and Electrical Machine
Power-Train Architecture
Torque-Speed Characteristics
IND1
Function Development Tool
CAN
300
250
I/O
Master Controller
CAN
WP 5+12
IND4
IND2
WP
3+8
Alternator
Power
Electronics
Torque (Nm)
ECU
DC/DC
Load Management
Supercapacitor unit
WP
2+7
IND4
WP 3+8
Torque 1.8l TC Nm
150
100
Electrical torque Nm
50
0
Clutch
WP
4+9
Torque 3.0l NA Nm
200
-50
0
1000
2000
3000
4000
5000
Battery
Starter
Speed (rpm)
Gearbox
IND1, HES5
WP
6+10
Electric
machine
HES3
End of boost
Regienov Proposal
Permanent Magnet Brushless Machine
End of regeneration
Simulated Duty Cycle
0.70
140
0.9
0.88
120
Boost area
0.86
-0.3 m/s² deceleration
(medium- high level)
Torque (Nm)
Vehicle
Speed
0.86
0.88
100
0.90
0.84
0.92
0.82
80
0.8
60
0.78
0.76
40
1
2
3
4
5
Engine speed
5
4
0.74
3
2
20
0.72
750 rpm
electric
machine
torque
Engine torque
0
500
1000
1500
2000
2500
3000
3500
4000
0.7
Speed (rpm)
regenerative
braking
7
FPEC
Free Piston Energy Converter
EC Project No. GRD2-2001-51813
Contract No. GR3D-CT-2002-00814
Partners
¾ AB Volvo Tech. Devel. Corp. (Co-ordinator) - Sweden
¾ Noax V.V. - Netherlands
¾ Institut Francais du Petrole - France
¾ ABB AB - Sweden
¾ Innas B.V. - Netherlands
¾ Chalmers University of Technology - Sweden
¾ Kungliga Tekniska Hoegskolan - Sweden
¾ University of Sheffield - UK
Funding
Euro 3.7m over 3-years, 2002-2005
Objectives
¾ To develop a clean and energy efficient technology for vehicle propulsion, based on the free
piston principle.
¾ Comprises an HCCI (Homogeneous Charge Compression Ignition) combustion system,
running on diesel fuel, and a power-dense linear electrical generator which converts the
piston mechanical energy directly to electrical energy.
¾ A 25kW FPEC technology demonstrator, with high power density >0.6kW/kg, is being
developed to meet Euro V emission limits.
The free piston energy converter converts chemical energy directly to electrical energy, and is a
potential power source for use in series hybrid vehicle drive-trains.
Free piston energy converter
Piston
Inlet
Port
Teeth Coils
¾ Floating piston--crankshaft eliminated
¾ Piston movement controlled by tubular
permanent magnet electrical machine.
¾ Piston motion profile controlled to
create variable compression ratio.
¾ Facilitates HCCI, leading to improved
fuel economy, and reduced NOx and
CO2 emissions.
Backiron
Translator
Shaft
Permanent
Magnet
Exhaust
Valve
Typical piston velocity and electromagnetic
force profiles for the FPEC system over two
strokes, when generating an output power of
≈25kW.
The force developed by the electrical machine
is maintained over approximately 95% of the
stroke.
Velocity (m/s), Force (KN)
The free piston principle offers unique possibilities to exploit the latest combustion research, HCCI
(Homogeneous Charge Compression Ignition), in which ignition of the air-fuel mixture takes place
when the gas pressure and temperature have attained values during the compression stroke. It is
possible to control the piston velocity on each stroke to achieve the correct timing for HCCI by
appropriate control of the electrical machine. The control requirements are very complex due to the
non-linear and unstable nature of the combustion process and safety considerations. dSPACE
micro-auto-box is being employed for fuel injection timing, and valve- and ignition-timing.
15
Piston velocity (m/s)
Electric force (KN)
10
5
0
-5
-10
-15
0
0.01
0.02
0.03
Time (s)
VOLVO
INNAS BV
8
3.2 Hybrid Vehicles
ELMAS
‘New high efficiency electrical machine solutions for mild hybrid applications’,
EC Project No. NNE5-1999-00675
Contract No. ENK6-CT1999-00017
Partners
¾ Centro Ricerche FIAT - Italy (Co-ordinator)
¾ AB Volvo - Sweden
¾ University of Sheffield - UK
¾ Politecnico di Torino - Italy
¾ Perm Motor GmbH - Germany
¾ Switched Reluctance Drives - UK
¾ University Politehnica of Bucarest - Romania
Funding
Euro 1,750,000 over 3-years, 2000-2003
Objectives
¾ To assess the feasibility for employing reluctance (ie. switched reluctance and synchronous
reluctance) machines in mild hybrid vehicles
¾ To quantify the operational benefits of mild hybrid vehicles, in terms of drive-train efficiency
and fuel economy
¾ To develop a control system to achieve the required functionality of the electrical machine
(viz. torque boost, regenerative braking, ICE starter, alternator, idle-stop mode) and the
various optimisation needs, whilst interacting with the ICE via the vehicle management unit
Mild hybrid vehicles are one possible solution for improving fuel economy and reducing
emissions. The engine in conventional ICE vehicles has to be sized to realise the vehicle peak
power requirement. Peak power operation is generally the most efficient operating area of the
engine. Hence, operation at a lower average output power results in the engine working less
efficiently. Hybrid vehicles offer an improvement in fuel economy, and, hence, reduced
emissions, due to load levelling of the vehicle tractive effort facilitated by an additional electrical
traction machine which is mechanically integrated with the ICE output. This electrical assist
allows the ICE to be downsized and operated around a higher efficiency window.
Mild Hybrid System
GEAR
BOX
ELECTRIC
MACHINE
INTERNAL
COMBUSTION
ENGINE
IC Engine and Electrical
Machine Torque-Speed Profiles
200
180
Minimal Hybrid
160
Torque [Nm]
140
Conventional
120 IC Engine
Downsized IC Engine
100
Conventional
Clutch
Additional
Clutch
80
60
¾ Additional clutch connects ICE and electrical
machine outputs to a standard vehicle transmission
with a manual or automatic gearbox
¾ Eliminates starter and alternator, and facilitates
idle-stop operation
40
Electric Machine
20
0
0
1000
2000
3000
4000
5000
6000
rpm
¾ Electrical machine rated to enable performance of
vehicle with down-sized ICE to exceed that of
standard ICE vehicle
¾ Electrical tractive effort alone available for parking,
queuing, and reversing
Electrical Machine Technologies
Switched Reluctance
The University of Sheffield
Electrical Machines &
Drives Research Group
VOLVO
Synchronous Reluctance
PermMotor Gmbh
9
10
11
ISOLAB42
Installation and Safety Optimised Battery for 42 Volt Applications
DTI Foresight Vehicle LINK project.
Partners
¾ Advanced Lead-Acid Battery Consortium (ALABC)
¾ Provector
¾ University of Sheffield
¾ FIAMM
¾ Warwick Manufacturing Group (Warwick University)
Funding
£250k to USH over 3-years,
Start date: 1st June 2003
Objectives
¾ To develop a optimised VRLA battery pack for 42V electric vehicles based around a double
ended, prismatic 2V distributed cells.
¾ To develop State of Charge monitoring and energy management methodologies compatible
with the needs of 42V vehicles.
¾ To investigate the life cycle of lead acid batteries under simulated hybrid vehicle driving
conditions.
¾ To embody the research findings in a demonstrator vehicle.
Several leading automotive manufacturers have announced their intention to move towards a 42V
system over the next few years because of the advantages gained by use of a higher system
voltage, within a vehicle where the ‘hotel’ and electric auxiliary load is high. Initial prototype 42V
batteries have been announced based on 3 × standard SLI batteries, which will significant increase
the battery size, and may cause problems for the installation of the battery within the vehicle. The
project aims to produce an optimised 42V battery based around a 20Ah prismatic cell, capable of
adopting a variable geometry, to utilise the most convenient space or spaces available within the
vehicle.
¾ Double ended prismatic cells facilitate optimised
usage of the cell volume, preventing sulphation of
the lower half of the cell, which is normally underutilised in a standard configuration, facilitate a
modular approach to the pack.
¾ The electronics within the pack can take one cell
out of the chain and condition it in isolation, whilst
the battery functions normally.
The University of Sheffield
Electrical Machines &
Drives Research Group
12
INMOVE
Integrated Modular Electric Propulsion System For Parallel Hybrid Vehicles
EC Project No. BE96-3186
Contract No. BRPR-CT97-0444
Partners
¾ Mannesmann & Sachs - Germany (Co-ordinator)
¾ Institut fur Kraftfahrwesen - Germany
Funding
¾ University of Sheffield - UK
Euro 5.2m over 3-years, 1998-2000
¾ SGS Thomson Microelectronics - France
¾ PSA Peugeot Citroen - France
¾ Ecole Superieure d’Ingenieurs de Marseille - France
Objectives
¾ To research enabling technologies which will facilitate the realisation of a low cost, parallel
hybrid propulsion system having an electrical power rating of up to 50kW
¾ To investigate the life cycle of lead acid and NiCd batteries under simulated hybrid vehicle
driving conditions
¾ To embody the research findings in a demonstrator vehicle
Both pure electric vehicle and hybrid vehicle operation are possible. When operating in the hybrid
mode, the ICE provides the mean tractive power, the peak power being provided by a permanent
magnet brushless ac machine and the battery pack. The electrical machine assists acceleration
and enables regenerative braking. It also acts as an alternator for charging the batteries, and as
a starter motor for the ICE. It has the full speed and torque capability of the ICE, viz. 6000rpm and
170Nm. Hybrid vehicles impose particularly punishing demands on the battery pack, which
operates within a restricted state-of-charge envelope, and must source and sink high powers
duringregenerative braking.
¾ Active synchronisation between the motor and
drive-train enables operation with a single clutch
and allows the motor to be integrated with the
clutch in a single housing between the ICE and the
gearbox.
¾ The high dynamic response facilitates active
synchronisation during gear changing, through
software control of the power electronic converter,
so that the machine can be coupled directly to the
input shaft of the gearbox.
The University of Sheffield
Electrical Machines &
Drives Research Group
13
3.3 Electric Vehicles
ZED
‘Innovative Electric Traction Module for Zero Emissions Down-Sized Urban Vehicle’,
EC Project No. PL97-0117
Contract No. JOE3-CT97-0067
Partners
• Piaggio - Italy (Co-ordinator)
• Centro Ricerche FIAT - Italy
• Cupex - France
• Varta - France
• Technical University of Berlin - Germany
• University of Sheffield - UK
Funding
ECU 1.9m over 3-year period, 1997-1999
Objectives
• Development of lightweight, 3-wheel, 1-person city car to complement more conventional
vehicles in context of environmentally friendlier transportation system
• To provide stability and comfort under all driving conditions
• To enhance safety through use of tilting body
- At low speeds, body and wheel traction system kept rigidly connected and vehicle
operated like a car
- At high speeds, tilting joint gradually released so that body can lean like a motorcycle
The vehicle concept aims to combine the safety and comfort of a small car with the mobility of an
electric scooter in city operation. It facilitates agile driving and easy parking, and has low energy
consumption, operational and lifecycle costs.
Specification
Basic Architecture
¾ Payload: 1 person + luggage
¾ Range in urban operation: over 80km
¾ Acceleration time: 6s
¾ Climbing ability: 22% at 40km/h
¾ Speed range ability: 45-75km/h
factory selected
¾ Enhanced operability by quick battery
recharging or quick battery substitution
¾ Self-standing body in vertical position at stop
¾ Light weight, multimaterial, fully recyclable
structure
¾ Optimized energy management through
vehicle management unit
¾ Comfort: protection against air and water
through aerodynamic profile
¾ High efficiency power-train with brushless dc
wheel motors
¾ Rigid spaceframe integrating aluminium and
composite materials
¾ Front impact and rollover withstand
¾ Collapsible element for absorption of impact
energy
¾ Safer driveability by tilting system
¾ Slip avoidance by powertrain control
¾ High specific energy and cycle life battery
¾ Easy battery substitution for charging and
intensive operation
Tilting System
Electric Power-train
¾ Automatic transition between low
speed and high speed driving modes
as function of vehicle dynamics
Wheel
Rotor
Brake
Stator
)
CENTRO
RICERCHE
FIAT
¾ Permanent magnet brushless dc
machine
¾ Peak torque: 70Nm
¾ Rated speed: 550rpm
¾ Cooling: air
¾ Peak motor efficiency: 91%
¾ Energy regeneration over full speed
range
The University of Sheffield
Electrical Machines &
Drives Research Group
14
15
FLYTECH/PEAKFLY
Partners
¾ Ansaldo Ricerche - Italy (Co-ordinator)
¾ BERTIN - France
¾ BMW AG - Germany
¾ Centro Ricerche FIAT - Italy
¾ Elettronica Santerno - Italy
¾ Renault - France
¾ University of Sheffield - UK
¾ VTT - Finland
Flywheel Peak Power Buffer for Electric
Vehicles
EC Project Nos. BE95-1616
PL95-0904
Contract Nos.
BRPR-CT95-0053
JOE3-CT95-0042
Funding
3.3m over 4-years, 1996-1999
2.3m over 3-years, 1996-1998
Objectives
¾ To research enabling technologies which will facilitate the realisation of a flywheel peak
power buffer for electric vehicles
¾ To produce and test a demonstrator kinetic energy storage/supply unit, having a ‘continuous’
power rating of 28kW and a peak power capability of 40kW
The main benefit of incorporating a peak power buffer in the power-train of an electric vehicle is
that the energy and power requirements are decoupled. This leads to a significant improvement
in the vehicle performance, in that:
¾ Response of vehicle is more consistent - independent of state-of-charge of batteries environmental conditions
¾ Lifetime of batteries is extended - since they are independent of transient high power demands
¾ Vehicle range is extended - due to combined effect of load-levelling of batteries and improved
energy recovery during regenerative braking
A high-speed flywheel is an alternative to the use of supercapacitors for a peak power buffer.
Flywheel Peak Power Buffer
Flywheel
Unit
Flywheel Concept
Vehicle Management
Unit
Power
Electronics
Energy Store
Inverter
Traction
Motor
¾ Mounting on Vehicle
• Annular carbon fibre composite flywheel rim
• Integral magnetic bearing system
• Integral permanent magnet brushless dc machine
¾ Demonstrator Unit
½ Testing of Demonstrator
EAST
16
OPTELEC
OPTELEC - ‘Energy Optimized Traction System for Electric Vehicles’
EC Brite/Euram Project No. BE97-4502 Contract No. BRPR-CT97-0499
Partners
¾ University of Sheffield - UK (Co-ordinator)
Funding
¾ Centro Ricerche FIAT - Italy
Euro 2m over 3-years, 1998-2001
¾ Magnetic Systems Technology Ltd - UK
¾ SAFT- France
¾ Centro Nacional de Microelectrónica - Spain
Objectives
¾ Optimise power-train configuration equipped with dual energy and power sources
¾ Optimise energy management strategy
¾ Develop power dense traction machine/gear stage
¾ Develop integrated power electronic module
¾ Validate performance on brassboard demonstrator
Batteries have a relatively poor efficiency and a limited lifetime when subjected to large transient
charge and discharge (regenerative) currents, during urban driving. A super-capacitor peakpower buffer significantly reduces transients on the battery, and makes the vehicle response
(acceleration) much less dependent on the state-of-charge of the battery.
Designated Urban and Extra-Urban Driving
Cycle, Based on ECE15
Vehicle
y, ms-1
Velocity,
Brassboard Demonstrator
Battery Pack 1
DC:DC
Traction
Inverter
Battery Pack 2
DC:DC
SAFT
Supercapacitor Bank
DSP
DSP-Based Digital Control Platform
• TMS320C32 DSP
• 8 x Analogue input channels
• 4 x Analogue output channels
• Fibre-optic link to drive
• 32 bit digital input/output
DSP
Custom Super-Capacitor Bank
• 50 x Maxwell Powercache
• 2500µF capacitance per cell
Traction
Machine
20
10
0
0
Traction Drive
Vehicle
Current, A Acceleration, ms-2
MAXWELL
Supercapacitor Bank
30
200
400
600
Time,
3
2
1
0
-1
-2
-3
0
200
400
800
1000
1200
800
1000
1200
800
1000
1200
800
1000
1200
s
600
300
200
100
0
-100
Time,
0
200
400
s
600
Time,
Supercapacitor
Current, A
DSP
40
300
200
100
0
-100
-200
Battery
Current, A
Battery Pack
• 18x12V, Hawker GenesisTM
70Ah Pb-acid monoblocks
Integrated Traction Machine
and gear stage
• Epicyclic gearstage
• 6500 rpm max. motor speed
• In-line output shafts and
differential
• 30kW continuous
• 45kW peak (2000 to 6500rpm
• 200Nm peak torque @ 500rpm
50
300
200
100
0
-100
-200
0
0
200
200
400
400
s
600
600
Time,
800
1000
1200
s
In the preferred drive-train format, the supercapacitor peak power buffer is interfaced directly to
the dc link, whose voltage is allowed to vary over a 2:1 range, and the battery is interfaced via a
bi-directional dc/dc converter. The inclusion of a peak power buffer and the adoption of an
appropriate energy management strategy can extend the vehicle range by ~25% during urban
driving and leads to a very low transient load on the battery.
The University of Sheffield
Electrical Machines &
Drives Research Group
MST
17
Novel Topologies of Electric Vehicle Antilock
Braking/Traction Control System
Overview
The alleviation of environmental problems associated
with personal, public and commercial transport in urban
areas has become an important issue for both policy
makers and the automotive industry. Future legislation
in Europe and the USA is expected to introduce strict
limits on vehicle emissions, and both electric and hybrid
vehicles are considered to be strong contenders for
meeting low/zero emissions targets.
Specific Benefits of Electric / Hybrid
Vehicles
Environment:
• reduction in air pollution,
acid rain and global warming
Main advantages offered by Electric and Hybrid
Vehicles compared to Internal Combustion Engine
Vehicles include:
Component
Suppliers:
• power electronics (e.g.
semiconductors)
• materials development
• Significant reduction
in emissions
Specific Benefits of
electric / hybrid
vehicles
Customer:
• extended range (e.g.
hybrid vehicles)
• improved performance
and handling of vehicle
• greater safety (e.g.
sophisticated control
systems)
•motor technology
development
• Increased operational
efficiency & flexibility
Automotive
manufacturers:
• meet legislative
emissions targets
Concept Electric Vehicle with
ABS / TCS system for the 21st
century.
Research Overview
The research aims to develop and apply modern
Antilock Braking / Traction Control System (ABS
/ TC) control concepts to electrically propelled
vehicles. To facilitate the realisation of the
developed techniques, a laboratory based
custom state-of-the-art DSP hardware platform
has been designed to integrate the system
control algorithms and simulate various tyre/
road m - slip characteristics.
ABS / TC problems encountered by automotive manufacturers:
• Major problem in the availability of appropriate
test-tracks/skid pans or experimental rolling road
facilities for evaluating proposed control algorithms.
C o n tro l R e g io n
Adhesion coefficient (µ)
1 .0
µ m ax
0 .8
60V
Torque
(Nm)
Torque (Nm)
Adhesion coefficient (µ)
• Great difficulty in the determining
the real-time µ-slip characteristics,
i.e. µmax and slip.
D ry R o ad
0 .6
0 .4
W et R oad
40V
20V
0 .2
S now y R oad
λ0
0 .3
0 .6
P.U.Slip
0 .9
SS lliipp ((σσ ))
S lip ( p .u .)
Induction motor torque - slip
characteristic operated in the
generator region
Classical µ - slip characteristic
curves for various road conditions
Research objectives:
Tdemand
Interface
k
+-
1
J
1
s
ω
σ=
ωs −ωr
ωs
• Develop performance metrics using modern control strategies in order to:
- Determine real time µ - slip characteristics for different road/ tire surface,
- Eliminate the use of ‘look - up’ tables derived from experimental trials.
slip
• Reduce development cost, by utilising DSP based test facility to develop&
evaluate ABS / TCS control algorithms for electrically powered vehicles.
Tload
Torque
Inverter
PM BLDC
Motor for
electric vehicles
Speed
sensor
Induction
Motor
Board
Variable
3 phase
voltage
supply
Torque (Nm)
Analogue
Host computer
DSP boards
Shaft speed
Slip (p.u.)
τ ind =
(
3V 2 R2 / s
ω s ync ( R1 + R2 / s )2 + ( X 1 + X 2 )2
)
Results to date:
Online graphical
display
0 .2
slip (p.u)
0
- 0 .2
- 0 .4
- 0 .6
- 0 .8
0
0 .2
0 .4
0. 6
ti m e ( s e c )
Electric traction drive
Road load
DSP based experimental test facility
Simulation model of
traction control test
facility
Experimental results of the traction control schemes are used to demonstrate the
test facility mimics the stable and unstable regions of the classical µ-slip characteristics.
0.2
0.2
M easured
A high performance
electric racing kart will
be used as a primary
test platform.
Power
controller
0
Slip>-0.3 p.u.
slip (p.u)
12 kW peak
rated brushless
permanent magnet
traction motor
(behind seat)
slip (p.u)
0
-0.2
-0.4
Unstable
-0.6
-0.2
Predicted
Stable
-0.4
Limited Slip at
-0.1 p.u.
-0.6
-0.8
-0.8
0
0.2
0.4
0.6
0.8
1
time(sec)
Test facility results with no
traction control scheme:
1.2
1.4
0
0.2
0.4
0.6
0.8
1
1.2
1.4
time(sec)
Test facility results with ‘bang-bang’
traction control scheme:
Test facility results with discrete-time based
optimal ‘bang-bang’ traction control strategy:
18
Electric Vehicles for Media/Leisure Events
Electric Land Speed Record Attempt
The current international land speed record for an
electrically powered vehicle stands at 215mph and is held by
Lightning Rod, which was designed and built in the USA.
The Bluebird Electric project aims to develop a battery
powered electric vehicle which ultimately will have a
capability of over 300mph.
The initial aim was to develop a technology demonstrator
vehicle capable of speeds of ~150mph. During a high speed
test run at Pendine Sands in South Wales, where Sir Malcolm
Campbell secured a world landspeed record in 1927, a new
official UK electric landspeed record of 116.4mph was
achieved and the largest maximum vehicle speed of 150 mph was reached, although it was not possible to
ratify this as a record. The landspeed record attempt is required to take place over a a measured mile, with a
return run over the same course to be completed within one hour. The power source needs to be capable of
providing a maximum power of approximately 150kW over a very short discharge, of only a few minutes
duration. Ideally, it should not be necessary to charge the batteries during a record attempt, however,
carrying excess battery weight will impair the vehicle performance. For the initial phase of testing a 600V, 16
AH high specific power lead acid battery was used, which had a total weight of 340kg.
2000
120
1800
100
1400
1200
60
1000
800
40
600
20
1
279 557 835 11131391166919472225
Time
Typical power-cycle/lap
6002
450
500
550
350
400
0
250
300
50
400
00
Speed (rpm)
1600
80
100
150
200
Battery power (kW)
Electric F3000 Racing Car
80.0-85.0
75.0-80.0
70.0-75.0
65.0-70.0
60.0-65.0
55.0-60.0
50.0-55.0
Torque (Nm)
Efficiency map from battery to wheel
Gearbox
Traction motor
Power controller
60 Nm and 75 kW rating
20,000 rpm maximum speed
Brushless d.c., 8 pole
NdFeB permanent magnets
Direct oil cooled
12 kg weight
3 phase, 6 switch full bridge
12 x 400 Amp IGBTs
Water cooled
35 kg weight for two controllers
Electric Kart
A high performance electric
kart with a 12kW peak rated
brushless pm traction motor
Epicyclic, splash lubricated
Up to 10:1 ratio
13 kg weight
Shell Solar Marathon Vehicle
The aim of the Solar ECO Marathon Challenge is to
promote enabling technologies for solar powered
mechanical systems, through competition. The
electric drive comprises a 200W nominal, 800W peak,
high efficiency, brushless ac traction motor and a
MOSFET based power electronic controller. The
efficiency of the combined traction motor and controller
exceeds 95% for the majority of the working envelope. A very
lightweight vehicle structure was employed to give a total
vehicle weight of 65kg, which included the traction drive, a
small battery, which acted as a buffer energy store, and two ~80W solar panels.
Through considered aerodynamic design and the use of ultra low rolling
resistance tyres, vehicle drag losses were minimised. On test with a 450kg
driver the vehicle achieved speeds of over 30mph whilst drawing less than
150W from the solar panels.
19
3.4
Thematic Networks
FABIAN
EPSRC Network: FABIAN – Fuel Cell and Battery Powered Vehicles Industry and Academic Network (GR/R51322/01)
Objectives
The Network has the following three primary objectives
¾ To bring together academic, industrial and government organisations in order
to identify key issues for further research and to encourage collaborative
investigations, and thereby contribute to the setting of the strategic research Funding
£62,554 over 3-years,
direction nationally.
2002-2004
¾ To provide a forum for technology dissemination, from state-of-the-art
information gathered world-wide, and to provide a link with other relevant
networks within the UK and Europe.
¾ To provide an educational role, by the organisation of colloquia, workshop
and specific training initiatives, and by facilitating secondments of personnel
between participating organisations and with external bodies.
July 2003
Start up mtg
Establish
other Network
contacts
Thematic
Group
Workshop
July 2004
Steering
Group
Steering
Group
Network
Workshop
Network
Workshop
Thematic
Group
Workshop
Thematic
Group
Workshop
Sept 2005
Motor
Drives
Power
Inverter
Control
Electronics
Steering
Group
Thematic
Group
Workshop
Thematic
Group
Workshop
Other network contacts and information dissemination
Prepare & issue R&D Strategic Plan
Set up process for training initiatives
Prepare web
-site &
newsletter
July
Conference
Sept 2002
Establish funding arrangements for continuation
>3yrs of network
Issue quarterly Newsletters. Update web-site on monthly basis.
Vehicle Electrical
Propulsion Systems
Traction
Battery
Systems
Fuel
Cell
Systems
Safety systems.
Ancillary vehicle systems
(heating, aircon, braking,
steering, 12/24 volt power).
Other
energy
sources
Network Operation
Co-ordinated by the University of Sheffield with funding for administration for 3-years from the EPSRC, the
Network will provide the following:
¾ Organisation of general workshops on overall issues, and discussion meetings on specific enabling
technologies.
¾ Web-site for information from the Co-ordinator and contributions from participants, with access to site
password controlled.
¾ A general web-site with open access.
¾ A quarterly newsletter for participants, summarising the most recent activities and developments
worldwide and giving information on future events.
¾ Details of other relevant networks and EC/world-wide projects, and reports on conferences/seminars.
¾ Formal links with professional and trade bodies.
¾ Support to government and other strategic bodies concerned with transport, the environment and fuels.
Log on and visit the NETWORK web-site
http://www.shef.ac.uk/fabian/
Register for the Network
workshops
20
ELEDRIVE
Thematic Network on Fuel Cell, Electric and Hybrid Vehicles
EC Project No. NNE5-1999-20036 Contract No. ENK6-CT-2000-20057/4
Partners
¾ AVERE (Co-ordinator)
¾ CITELEC
¾ ENGVA
¾ World Fuel Cell Council
¾ AEA Technology (UK)
¾ CEST (UK)
¾ ECN (Netherlands)
¾ EIVD (Switzerland)
¾ EMD (UK)
¾ ENEA (Italy)
¾ FKA (Germany)
¾ IKA (Germany)
¾ TNO (Netherlands)
¾ VKA (Germany)
¾ VUB (Belgium)
¾ Alstom Transport (France)
¾ Centro Ricerche FIAT (Italy)
¾ Electrabel (Belgium)
¾ Institut Français du Pétrole (France) ¾ PSA (France)
¾ Renault (France)
¾ Saft (France)
¾ Volvo (Sweden)
¾ ZEVCO (UK/Belgium)
Objectives
¾ To create synergies at the European level so
as to accelerate the development and
introduction on the market of fuel cell,
electric and hybrid vehicles
¾To help select the most promising technology options for prototype bench and
field testing of components and complete
vehicles
¾ To facilitate the exchange of expertise and
the transfer of knowledge to ensure a global
discussion and foster research and development, and to help identify cost-effective
solutions
Funding
¾ To contribute to the integration of nextEuros 721,326
generation vehicles which are fully in line
over 3-years, 2001-2003
with the objectives of the key action “
Economic and Efficiency Energy for a
The ELEDRIVE network brings together:
Competitive Europe”
¾ Representatives of relevant industries, viz. vehicle
manufacturers, component suppliers, infrastructure and fuel development
¾ Key research organisations who are working on European transport innovation projects, national and locally
funded projects
¾ National representatives and members of international bodies, who have the capability of integrating
environmentally friendlier vehicle concepts
¾ Market and user representatives, who are aware of market and consumer requirements
The introduction of fuel cell, electric and hybrid vehicles is a complex issue, and substantial
progress can only be made by collaborating at the European, or even the world-wide, level.
The Network will:
¾ Identify future propulsion requirements for road transport, in genera
¾ Establish criteria for cost-effective analysis of technology options which take EU policy goals into
consideration
¾ Consider the expectations of the various stake-holders connected with the introduction of a new
generation of vehicles
¾ Identify technology gaps and future commercial opportunities
¾ Simulate fuel cell, electric and hybrid drive-lines to predict optimal drive-line architectures for given
applications
¾ Perform in-depth analysis of fuelling options for fuel cells, including comprehensive environmental, energy
and safety audits of the complete fuel chain
¾ Establish test procedures and performance criteria to ensure a consistent and coherent input to
technology assessment
¾ Contribute to the development of standards for vehicle equipment, its installation, use and maintenance,
fuelling, fuel handling, and general operational aspects of fuel cell, electric and hybrid vehicles
NETWORK STRUCTURE
European
Commission
No.
Title
Leader
WP1
Common interest matrix and action plan
ENEA, ENGVA
WP2
Review of state-of-the-art and world-wide
developments
EMD, VUB
WP3
Database of results, components and testing
methods
CRF
WP4
Comparative assessment
Renault
WP5
Legislation and standardisation trends
CITELEC
WP6
Techo-economic analysis and recommendations
for future work
PSA
WP7
Dissemination of information and training
AVERE
Co-ordinator
Extended Steering
Committee
Country Representatives
Steering Committee
WP Leaders
Members
21
4.
Aerospace
22
23
Enabling Technologies for More-Electric Aircraft Engines
(EPSRC Platform Grant)
Research outline
z
z
z
z
Fundamental research on the technology
options for embedded machines in civil aircraft
high by-pass turbo-fan aero-engines
To develop high power density / high efficiency
machines and magnetic bearings in parallel
with power electronics capable of operating in
the extreme environment
Integrated Starter/Generator for the High
Pressure spool of a large civil aero-engine
Identification / assessment of magnetic material
(hard and soft) and conductor/insulation
materials capable of operating at high
temperatures
Current technology
z
Turbo-fan engine
Complex gear System
- Extremely heavy
- Requires oil lubrication
- Very high maintenance schedule
- High losses
z
Gearbox assembly
Radial take-off shaft
- Interrupts airflow through engine
Radial take-off shaft
Rotor Stress Analysis
z
- Increased Copper Loss (~2.5 times room temp)
- Reduced Iron loss
- Reduced mechanical strength of lamination steel
- Precludes use of permanent magnets
(Sm2Co17 - Br < 0.6T at 400°C)
- Precludes use of carbon fibre over-wrap
z
z
‘Fir-tree’ arrangement, as shown in Figure 2.
This is widely used to retain turbine blades
z
Dovetailing of the rotor modules with an
appropriate degree of pre-compression
z
Linear Friction Welding - directly attaching
the laminations onto the high-strength ring as
shown in Figure 3. A stress plot of one pole of
a modular rotor is shown in Figure 4
High temperature environment ~350°C
Machine specification
Topology: Switched reluctance
Figure 1. 248mm conventional rotor - 15000rpm
Power:
>100kW @13000rpm (Generating)
Speed:
7800-13500 (Generating)
15000 (over-speed)
Maximum Torque:
z
200Nm (start-up)
Figure 2. Fir-tree shape turbine blade roots
Conventional SR rotor design
High speed and high temperature, together with
maximum stress limitations due to fatigue
concerns, limit the conventional SR rotor diameter
to 248mm. A finite element stress plot of one pole
of a conventional rotor is shown in Figure 1
z
Figure 4. 300mm modular rotor - 15000rpm
G
Cobalt Iron single
piece stator
F
E
H
D
C
Phase B
Winding
Modular SR rotor design
B
A modular rotor design has been proposed
where hoop stress is borne by the high strength
hub, thus achieving a larger diameter and
higher power for a given speed. A number of
approaches have been considered for retaining
the rotor tooth modules:
Non-magnetic rotor
hub, e.g. Inconel 718
Phase A
Winding
A
Cobalt Iron rotor
pole modules
Figure 3. Friction-welded modular rotor design
Electromagnetic analysis
z
A 300mm modular rotor machine has been
compared with the maximum safe rotor diameter
conventional rotor machine (248mm) on a
magnetostatic basis using 3D finite elements
z
Figures 5 and 6 show unaligned and aligned flux
linkages respectively, from 2D magnetostatic
finite element solutions for the modular machine
z
Greater average torque is achieved in the
modular rotor machine at the expense of inverter
complexity - 8 phases compared to 4 for the
conventional rotor - although the total amount of
silicon is the same for each inverter
z
2D Look-up tables have been created from 3D
finite element data for i-Ψ-θ and i-T-θ, and
interpolated surfaces for each table form the
basis of the non-linear model for the machines,
solving the governing equation:
ψ =
∫ (v − iR ). dt
3D finite
element
results
Figure 5. Unaligned flux
Figure 6. Aligned flux
2D look-up
tables
Single phase non-linear dynamic model of SR machine
24
Optimal torque control of fault-tolerant
permanent magnet brushless drives
Fault-tolerant permanent magnet brushless machine and drives are emerging as a key
enabling technology for safety critical applications, in the aerospace and automotive sectors,
for example, due to their high power density relative to other competing machine technologies.
¾ Coils wound on alternate teeth
¾ Phases are magnetically, thermally and
physically isolated.
¾ Phase winding designed to have ~1 p.u.
phase inductance to limit short-circuit
current to rated full load value
¾ Each phase supplied from a separate H bridge
H-bridges
5 phase, 10-pole fault-tolerant
PM Machine
Conventional control strategy, which maintains
sinusoidal current waveforms in the healthy phases
results in a large torque pulsation under fault
conditions, such as an open-circuited or a shortcircuited phase.
Optimal torque control strategy eliminates torque ripple under various fault conditions as
well as eliminating the influence of cogging. The developed control strategy operates in both
the constant torque and constant power operational modes while minimising the copper loss
under voltage and current constraints.
Closed-loop speed control system
Td
ωd
Speed
controller
ω
Optimal
torque
controller
i1d
i2d, …,
ind
Current
controller
Fault-tolerant
PM machine
ω θ
i1 , i2, …, in
ω
⎡
a j (t ) ⎢Td − T f (t ) + w
L
⎢
⎣
i j (t ) =
m
⎤
( )∑ a (t )ψ ⎥⎥
θ
∑ [a (t)]
m
j
j≠k
j
⎦
2
j
Fault detector
j≠k
w
− ψj
L
Optimal current waveforms
Optimal current waveforms
Phase 5 open-circuit
Phase 5 short-circuit
5 phase fault-tolerant PM machine
25
5.
Healthcare
Reciprocating Air-Compressors
(In collaboration with Huntleigh Technology plc.)
¾ For healthcare products such as pressure area care flotation mattresses
Flotation mattresses prevent bedridden patients from contracting
decubitus ulcers, commonly known
as bed-sores. They consist of a
series of air-cells which are
sequentially inflated and deflated in
order to reduce the interface
pressure between the patient and
support surface.
Static pillow
section
The mattress is supplied from an air-compressor, the
prime-mover of which is a mains powered linear actuator.
In order to achieve maximum efficiency, the moving mass
of the prime-mover is matched to the diaphragm
compliance, so that the mechanical resonant frequency is
the same as the electrical supply frequency (50Hz). This
results in maximum displacement of the diaphragm, and,
hence, maximum airflow. The non-linear stiffening spring
characteristic of the diaphragm, coupled with the pressure
dependant gas spring rate of the compressor, make the
prediction of the dynamic performance both complicated
and highly dependant on the mechanical and pneumatic
systems.
Inlet
filter
Mattres s /
overlay
C ell group 'A'
C ell group 'B'
Reciprocating
prime-mover
Losil500 (Si-Fe)
E-core stator
Diaphragm
A
B
Air dis tribution
to cell group 'A'
A
Excitaion
coil
Com pres s or
B
0 m in
Compression
chamber
Air dis tribution
to cell group 'B'
10m in
0 m in
Pres s ure
regulator
10m in
Injection-Moulded
Strontium Ferrite
shuttle
Inlet port
and valve
Plenum
cham ber
Outlet
Flow control
valve
0 m in
Exhaust port
and valve
10m in
PRESSURE AREA CARE MATTRESS SYSTEM
Plenum chamber
RECIPROCATING AIR-COMPRESSOR
MOVING-MAGNET LINEAR ACTUATOR
SYSTEM SIMULATION
In order to accurately predict the dynamic performance, a detailed electromagnetic
model of the actuator is coupled to non-linear models of the mechanical system and the
compressor.
i
5
Measured
4
L
-60 mA
-40 mA
3
MAGNETIC
ELECTRICAL
Variable clearance
volume
-20 mA
0 mA
2
20 mA
dψ
dt
exhaust
Displacement
GAS COMPRESSION
1
40 mA
60 mA
0
-0.006
-0.004
-0.002
3d-FEA
0
0.002
0.004
-1
0.006
-60 mA
-40 mA
-2
-20 mA
-3
20 mA
0 mA
x&
Piston
(surface area Ap)
inlet
Force (N)
Vo
x
40 mA
Fact
-4
60 mA
-5
Displacement (m)
V3
Pc ham ber
Pchamber <Pamb
(suction)
Cylinder
x
Pamb
Fc (x, p plenum ) = (Pchamber (x, p plenum ) − Patmos ). Ap
MASS-FLOW RATE THROUGH VALVE
ELECTROMAGNETIC MODEL
F fluid
Compression
volume
MECHANICAL
FLUID
REACTION FORCE ON SHUTTLE
0.0050
Measured
Displacement (m) .
0.0045
10mmHg
0.0040
40mmHg
0.0035
80mmHg
0.0030
120mmHg
Simulated
0.0025
10 mmHg
0.0020
40 mmHg
0.0015
80 mmHg
0.0010
120 mmHg
0.0005
0.0000
40
45
50
55
Frequency (Hz)
60
Simulation and measurements in time and frequency domains
TUBULAR MOVING-MAGNET ACTUATOR
CAD software has been developed to optimise new topologies of actuator for use in next-generation air-compressors, whose supply frequency can be varied to match the shift in the mechanical resonant
frequency which occurs due to changes in delivery pressure with patients of different weight, and to satisfy the specification demands for battery-operated equipment such as wheelchair seating. A number
of patents have been granted, in collaboration with Huntleigh Healthcare plc.
Advantages of tubular actuator
;No leakage flux
Mild steel outer
shell
;Allows for rotation of shuttle
;Low saliency force
Bobbin wound
excitation coils
;No end-effects
;Compact
;No radial force
Permanent
magnet/mild steel
2-pole shuttle
FEA model accounting for
non-ideal magnetization
PROTOTYPE ACTUATOR
26
Air-Flow Control Valve Actuators
(In collaboration with Huntleigh Technology plc.)
OBJECTIVES
Advances in both actuator and drive technologies, coupled with the need for products which
offer greater flexibility and commercial competitiveness, are promoting the development of
improved air-flow control systems. Next-generation systems which are more compact and offer
greater operational flexibility. Various novel permanent magnet latching actuator-driven valve
designs have been developed, which have increased functionality over motor-driven valve
systems, consume significantly less over their operating cycle, and which are capable of
latching in a number of stable positions with zero energy input.
Typical multi-position motor-driven
rotary valve
Five-position rotary latching actuator
COIL4
Exhaust to
atmosphere
COIL3
F low
divertor
lso lcu
βr/2
COIL5
COIL2
T o cell group 'B'
βs.
lg2
COIL1
ROTOR
ri
T o cell group 'A
Air flow from
compressor
r1
lsi
Rotating valve
assembly
Sliding face
seal
lg1 lm
COIL6
Exhaust port
(to cell group)
WOUND
STATOR
NON-WOUND
STATOR
BRIDGE
MAGNET
Static port
assembly
Compression
spring
Inlet port
(from compressor
Synchronous
motor and
gearbox
Typical field distribution
Prototype actuator on torque
measurement rig
Torque-angle characteristics
Two-position valve with bi-stable linear actuator
Bi-stable actuator
3-d Finite element analysis
Measured dynamic performance
27
SEMI-ACTIVE VIBRATION ISOLATION OF
RECIPROCATING AIR-COMPRESSOR
Tubular reciprocating air-compressor
•Reciprocating compressors, driven by short-stroke linear actuators, are
operated at their mechanical resonant frequency in order to maximize
efficiency and air flow. The resonant reciprocating motion results in
considerable vibrations being transmitted to the supporting structure.
•Currently, rubber anti-vibration mounts are employed to isolate the
vibrating air-compressor from its surroundings. However, these may not
be adequate, and a more effective means of cancelling the transmitted
vibration energy between the compressor and the supporting structure
must be employed.
•The vibration level of a tubular, moving-magnet, reciprocating aircompressor (3W, 5.5lpm, 40mmHg) is being investigated.
Principle of semi-active vibration isolation with flexure bearings
Micro
controller
•Semi-active vibration isolation, in which an additional actuator is positioned
Armature
M1
c1
k1
Drive
in between the stator mass and the support panel, in parallel with passive
isolators, has been identified as a preferred arrangement. The additional
‘isolation’ actuator is controlled such as to cancel the force that is transmitted
through the passive isolators. As a result, the stator will move in anti-phase
with the shuttle.
F
•Flexure bearings, which consist of flat metal discs in which spiral grooves
are cut, are conveniently employed to mount the tubular air-compressor. Since
they exhibit a high ratio of radial to axial stiffness, they are ideally suited to
mount tubular, reciprocating devices.
Stator
M2
k2
F
c2
•The additional isolation actuator must be tubular, lightweight and have a
minimal axial length.
Isolation
actuator
Position
sensor
Outer clamp
Rco
Inner clamp
Rci
Micro controller
and drive
Semi-active vibration isolation
•An additional sensor will be required to measure the instantaneous force
through the bearings, and a control algorithm must be implemented to drive the
isolation actuator
Design of flexure bearing and additional ‘isolation’ actuator
•The
dimensions of
a suitable pair
of stainless
steel flexure
bearings have
been
designed
using
‘ANSYS’
structural FE
software
t
•The tubular ‘isolation’ actuator consists of an axially magnetised,
bonded rare-earth magnet, sandwiched between two mild-steel
pole pieces in order to produce an essentially radial flux density in
the region occupied by the two stator coils.
•An analytical modelling technique, which assumes cylindrical pole
pieces and an infinite length of the outer shell, is employed to
derive optimal actuator dimensions. FE software (MEGA) has
subsequently been employed to optimize the shape of the pole
pieces, in order to optimally employ the flux-carrying capability of
the steel and reduce the overall weight of the shuttle.
Construction of test rig and results
Auxiliary masses
Isolation
actuator
Connecting
rod
Shuttle
Compressor
F
Stator
F
Additional
mass
•In order to measure the effectiveness of the semi-active
vibration isolation arrangement, a test rig has been
constructed in which an auxiliary mass is mounted in
between the compressor and the supporting structure.
Therefore, the force which is transmitted from the
compressor can be estimated through a measurement of
the motion of the auxiliary mass
•The action of the isolation actuator results in a reduction
of the motion of the auxiliary mass by 99%. Therefore, the
isolation actuator achieves a cancellation of the force
which is transmitted between the air-compressor and its
support, i.e. the auxiliary mass.
•The merits of different control strategies and the use of a
number of candidate sensor arrangments to drive the
isolation actuator will be compared using a dSPACE, realtime control implementation.
28
6.
Consumer Products
Spherical Actuators With MultipleDegrees-of-Freedom
¾ Facilitate controlled motion with two and three degrees-of-freedom
¾ Provide high bandwidth dynamic performance and tracking accuracy
¾ Simplify mechanical structures and alleviate problems associated with
inertia, non-linear friction and elastic deformation of gears
¾ Potential applications include:
- Force-feedback joysticks
- Robotic wrist joints
Two degree-of-freedom version
Prototype
z
stator
windings
•
•
•
•
•
y
spherical
rotor
x
48mm diameter sintered NdFeB rotor
oil-lubricated nylon stator
±45° pan and tilt excursions
0.15Nm continuous torque (0.4Nm peak)
400 rad/s2 angular acceleration with payload
stator
Three degree-of-freedom version
Prototype
y
A
x
D’
C’
A’
B’
B
D
C
Iron-cored 3 DOF version
• Detent torque due to aperture in addition to
excitation torque
• Eddy currents induced in stator core
29
OBSERVER BASED FEEDBACK CONTROL OF
3RD ORDER LCC RESONANT CONVERTERS
rds
iL
rcs
Cs
L
rl
iR
n:1
Cp
v cs
Vi
v cp
rcp
Fast sub-system
|iR|
Higher converter switching frequencies promote:
¾ Smaller capacitors and inductors, reduced volume envelope
¾Higher switching losses for hard-switched converters (e.g. buck, boost).
Resonant Converters (ZVS) with high-order tank circuits promote:
¾ Reduced switching loss and, hence, can operate at much higher frequencies
(100kHz-10Mhz).
¾ Safe operation under open and/or short circuit load conditions.
¾ Use of parasitic inductances/capacitances as circuit components.
v cf
Cf
RL
V out
rcf
Slow sub-system
⎡
⎢ 0
⎡v&Cp ⎤ ⎢⎢
⎢ v& ⎥ ⎢ 0
Cs
⎢ ⎥=⎢
⎢ i&L ⎥ ⎢ 1
⎢ ⎥ ⎢−
⎣⎢v&Cf ⎦⎥ ⎢ L
⎢ 0
⎣⎢
Power supply requirements:
¾Smaller size, increased power density:
¾Smaller reactive components
¾Low profile
¾Higher efficiency
¾Longer battery life
¾ Smaller heatsink, reduced mass
Typical applications:
¾Plasma TV’s, PDA’s,
¾X-Ray, medical imaging
0
−
1
L
⎤
i
⎤
⎡
⎥
− R
⎥
⎥ ⎡v ⎤ ⎢
Cp
⎥
⎥ ⎢ Cp ⎥ ⎢
0
0
⎥
⎥ ⎢ vCs ⎥ ⎢
⎥ ⎢ ⎥ + ⎢ Vi + iR rCp n ⎥
iL
⎥
⎢ L
⎥
L
0
⎥
⎥ ⎢⎣⎢vCf ⎥⎦⎥ ⎢
iR RL
⎥
⎢
⎥
1
−
⎢⎣ C f (RL + rCf )⎥⎦
⎥
C f (RL + rCf )⎦⎥
n
Cp
1
Cs
rds + rCs + n 2 rCp + rL
0
−
0
L
0
0
Cp
⎧ Cf n
iL + sgn (iL )
vCf
⎪
RL (C f + C p )
iR = ⎨ C f + C p
⎪
0
⎩
vcp > vCf + 2Vd
vcp ≤ vCf + 2Vd
State-variable model
[iR]
From
-KGain
[iR]
From1
-KGain6
1/L
Gain7
Input
Voltage
1
s
Integrator
vcp
Goto5
-KGain2
1
s
Integrator1
-KGain1
1
s
Integrator2
il
Goto3
-KGain5
1/L
Gain3
¾ Specific issues related to the design and realisation of observer-based
feedback of isolated output voltage for resonant power converters are:
¾Appropriate pre-conditioning of the non-isolated resonant-tank voltages and
currents, in order that the resulting observer can be implemented at relatively low
sampling frequencies.
¾Advantage of low-cost digital hardware.
¾A 3rd order LCC voltage-output resonant converter is a candidate topology.
3rd Order LCC (Series-Parallel) Voltage-Output Converter
¾ A drawback of a capacitor output filter is that it introduces additional
operating modes, since the voltage across the parallel resonant capacitor is
clamped at the output voltage when the rectifier conducts, and it cannot,
therefore, be considered to be sinusoidal.
[iR]
From2
|u|
Abs
1/L
Gain4
1
s
Integrator3
-KGain9
Rectifier Model
vcf
Goto6
-KGain8
[il]
From3
-KGain10
-KGain
12
[rect]
From5
Switch
-KGain13
Output
Voltage
iR
Goto2
Sign
-KProduct Gain11
[vcf]
From4
0
Constant
Simulink implementation of state- variable model
Circuit Operation
¾ For efficient operation the converter is assumed to be
operating above resonance
¾ 6 distinct operating modes (M1 to M6) exist in each switching
cycle of the input voltage, defined w.r.t. the polarity of the
input voltage and the state of the rectifier current.
20
1
iR
Vi
Cs
rcs
L
rl
iR
0.5
M1
M2
M3
M4
M5
M6
0
0
n:1
Vdc
vcs
Vi
Cp
rcp
vcp
-10
Cf
vcf
RL
Current (A)
iL rds
Voltage (V)
10
-0.5
vcp
Mode 1: iV
>0, Ri < 0- (M1)
>0, Ri = 0- (M2)
Mode 2: iV
>0, Ri >0- (M3)
Mode 3: iV
<0, Ri > 0- (M4)
Mode 4: iV
Mode 5: iV
<0, Ri = 0- (M5)
<0, Ri < 0- (M6)
Mode 6: iV
-1
Vout
-20
4.963 4.964 4.965 4.9
4.966
66 4.967 4.968 4.969
Time (ms)
rcf
4.97
4.971
Operating modes of converter
3rd
Order LCC Voltage-Output Converter
Modelling the
To obtain the state-variable equations that describe the converter operation,
the circuit is partitioned into two sub-systems:
1. The output filter (capacitor and load) represented by a ‘slow’ subsystem.
2. The resonant circuit represented by a ‘fast’ sub-system.
The interaction between the two is related through a rectifier coupling equation.
Experimental Results
The benchmark converter is designed to
the following specification:
Vout=350V
Vdc=150V
fs=160kHz
Component values are:
180
140
120
100
L=485µH
80
Cs=3nF
Cp=680pF
60
Cf=47µF
40
150
RL=180Ω
180Ω s-s
160Ω s-s
140Ω s-s
180Ω exp
160Ω exp
140Ω exp
160
Outputvoltage (V)
3rd-order LCC (Series- Parallel) voltage- output converter
155 160
165
170 175 180 185
Frequency (kHz)
190
195
200
Comparison of output voltage obtained from state
variable model and benchmark converter
30
LOW COST ENERGY EFFICIENT COMPRESSORS
FOR REFRIGERATION
Carbon Trust Project No. 2003-3-51
Partners
¾ University of Sheffield - UK
¾ Merloni Elettrodomestici Ltd - UK
¾ Magnet Applications Ltd - UK
¾ Hoganas AB - Sweden
Funding
£394,516 over 2-years, 2004-2005
Objectives
¾ To develop low cost, energy efficient linear oscillatory compressors for use in refrigeration systems.
¾ This will be achieved by exploring established and novel linear motor designs and their production
techniques, undertaking a detailed evaluation of candidate motors in conjunction with compressor
dynamic characteristics, and addressing aspects related to system integration.
This project proposes to develop a novel and much
simpler design of direct-drive linear motor compressor
with a significantly higher overall efficiency (~85-95%)
and at a competitive cost.
Low cost linear compressors for
refrigeration
It is estimated that adoption in the UK of the proposed energy
efficient compressor technology would reduce energy
consumption in this product area by up to 50%.
Refrigeration represents a significant and growing electrical
load, currently accounting for ~14% of the total electrical
energy consumption in the UK. Conventional refrigerator
compressors comprise of a rotary electric motor that in turn
drives a reciprocating pump through a crank-piston. Their
overall efficiency is low (~60%) due to the inherently low
efficiency of induction motors and the mechanical friction of
the crank-driven piston movement.
5
2.5
6.0
4
2.0
3
1.5
2
1.0
200
4.0
100
2.0
0
0
Piston velocity (m/s)
8.0
Current (A)
volta ge
curre nt
300
0.5
1
0
0
-1
-0.5
-100
-2.0
-200
-4.0
-300
-6.
-3
-8.0
-4
0.5
-400
0.5
0.505
0.51
0.515
0.52
Time (s)
0.525
0.53
Voltage and current waveforms
15
-1.0
-2
dis pla ce me nt
ve locity
0.505
0.51
0.515
0.52
Time (s)
Piston displacement( x10-2 m)
Time-domain linear compressor system model
400
Voltage (V)
The main technical tasks can be summarised as:
Comparative trade-off studies on various linear motor
topologies in terms of efficiency, costs and suitability for
integration with linear compressor technology.
Dynamic
modelling
and
evaluation
of
complete
electromechanical/thermodynamic system.
Design synthesis and optimisation of complete compressor
system.
Prototyping of demonstrator linear motors/ compressors and
establishment of facilities to measure static and dynamic
performance characteristics.
Development of low cost motor controller to adaptively
match the cooling capacity of the compressor to heat loads
so as to minimise energy consumption.
Performance and energy audits on current and proposed
refrigeration compressor technologies.
The research will consider the merits of different motor
technologies in terms of achievable operating
frequencies and strokes, system efficiency, costeffectiveness and ease of integration. It will cover all
areas related to the manufacture of techno-economically
viable refrigeration systems for use in domestic/
commercial products. The findings will be embodied in
technology demonstrators having appropriate ratings
and operational characteristics.
-1.5
0.525
-2.0
0.53
Piston displacement and velocity
x 10 5
10
5
0
0.5
0.505
0.51
0.515
0.52
0.525
0.53
Gas pressure waveform
Steady-state response of linear compressor at 60Hz and 220 (Vrms)
31
7.
Industrial
ELECTROMECHANICAL FRICTION SURFACING/
WELDING SYSTEM
There is significant interest in developing portable friction welding and friction surfacing units, for use in environments such as underwater,
high radiation and explosive atmospheres. Thus far, however, lightweight units have employed pneumatic and hydraulic actuation systems.
However, these require specialised power sources (high volume/pressure pneumatic compressors or hydraulic power supplies) whilst the use
of oil for drive and/or lubrication prevents their use in “clean” environments.
An electrically actuated system has been developed to enable programmable friction surfacing and friction stud welding in clean environments.
Friction welding profiles
Friction welding
Friction
force
It involves the generation of heat
by the rotational or oscillatory
motion of two components relative
to each other under an applied load
(friction
force).
Once
the
components have reached the
necessary
temperature
and
deformation, the motion is stopped
and the load increased to create a
solid phase bond (forge force).
Rotary friction stud welding is by
far the most common form, and
accounts for the majority of friction
welding
machines
currently
employed in industry.
Forge
force
Friction surfacing
Rotational speed
Axial Force
Burn off
As with the welding process, two
components are rotated relative to each
other under an applied load to generate
heat. However, as the components
reach the necessary temperature and
deformation begins, the consumable
component traverses over the substrate
to produce a welded layer, typically 24mm thick. Friction surfacing can be
used to deposit a wide range of wear
and corrosion resistant coatings onto
many different substrate materials,
including steel and aluminium alloys.
Friction surfacing profiles
Rotational speed
Axial Force
Burn off
Friction force
Requirements for linear/rotary actuators
To friction weld a 10mm mild steel stud, it is required to rotate the stud at a maximum rotational speed of 3800rpm at power of 8.5kW and to
apply a maximum axial force of 9kN over a linear displacement of up to 100mm.
370mm
Roller screw linear actuator
(Integrated BLAC motor + multiple threaded helical
roller )
Air cooled
8.5kW PM brushless ac motor
9kN linear actuator
12
200
10
Torque Nm
Efficiency %
160
Torque, efficiency.
Output force KN
180
140
Rated operating
point.
120
100
80
8
2 Amps
6
3 Amps
4
5 Amps
4 Amps
6 Amps
60
2
40
20
7 Amps
0
0
0
1000
2000
3000
4000
0
5000
1
2
3
4
5
6
7
Slider displacement mm.
Speed rpm
Predicted performance characteristics and open-circuit flux plot of
air-cooled motor
Measured static force/current displacement
characteristics of -40 roller screw actuator
Integrated
rotary/
linear
actuators
Drive unit
System under test
LabView-based
control unit
32
PULSED FIELD MAGNETO-POLARISCOPE
Photoelastic effect
Toughened glass
Transparent materials become birefringent or doubly
refracting when deformed
This photoelastic effect can be used to measure strain in
transparent components
Useful for non-destructive testing of glass and
evaluation of epoxy models
zStrain through thickness can be
close to equilibrium
zTraditional photoelastic
techniques produce little or no net
retardation or rotation of the light
Conventional magneto-photoelastic
measurements
Magnetic field applied parallel to incident light
- Faraday effect changes polarisation plane
Allows through thickness strain distribution to be determined
- critical for optimising and controlling performance of high
performance toughened glass, e.g. automotive glass
Existing systems based on DC electromagnets
-Limited magnetic field capability ( ~2.5T)
-Very small sampling area ( ~2mm)
-Slow and tedious measurement procedure
Pulsed-field magneto-photoelasticity
Basic configuration
High intensity pulsed magnetic fields (up to ~10T) can be
readily produced using capacitor discharge technology
Solenoid coil can have a large bore which gives
unhindered view of a large test-piece
Provides a rapid means for taking a sequence of images
at different magnetic field intensities
- scope for practicably extending technique to 3D
epoxy models
Prototype measurement system
High-speed
camera
Sample
z 10kJ, 3KV capacitor discharge magnetiser
z 70mm sample diameter
z Maximum flux density 4.1T
z Rise time of 2.5ms
z 40,500 frame per second high-speed camera
Measured intensity variation in one region
Solenoid
coil
Motorised
polariser
Beam
expander
Green
Laser
Capacitor
Discharge
magnetiser
33
SENSORLESS HIGH-SPEED BRUSHLESS DC
MOTORS
Why high-speed?
Why sensorless?
Typical applications:
•
•
•
•
•
•
•
•
•
High power density
Small size
High system efficiency
Reduced component count
Improved reliability
No mechanical/hysteresis problems of discrete sensors
Machine tool spindle drives
Compressors
Pumps
Sensorless commutation by detection of zero-crossing of back-emf waveform
em f
T1
T2
T3
D1
Vdc
D3
D2
eB
D4
d e te c tio n
p o in t
id eal c u r ren t
w a v efor m
eC
0
T6
T5
T4
eA
p h as e v olta g e
30
60
90
1 20
150
18 0
210
24 0
270
300
330
3 60
c u rren t
w a v efor m
D5
D6
D io d e c on d u c tion
a n g le
Stator laminations
Key Design Considerations
Overall length
Rotor back-iron
Endwindings
Diametrically
magnetised magnet
Windings
Design requirements:
• High efficiency
• Low diode conduction angle, <30o
– Use sensorless commutation IC based on detection of zero-crossing of
back-emf waveform
Stator outer
diameter
Containment
Key design parameters:
• Iron and copper losses
• Diode conduction angle
• Split ratio - rotor to stator outer diameter
• Aspect ratio - stator core length to outer diameter
• Stator flux density
Active length
Rotor
diameter
Influence of Design Parameters on Diode Conduction Angle
• Motors designed to same specified torque & speed, and
– fixed overall space envelope, magnet thickness & airgap length,
– variable rotor diameter and stator flux density
60
60
B
40
30
Rotor diameter
16 mm
18 mm
20 mm
22 mm
24 mm
26 mm
28 mm
20
10
Increasing rotor diameter
A
0
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
16 mm
18 mm
20 mm
22 mm
24 mm
26 mm
B
50
Diode conduction angle (deg)
Diode conduction angle (deg)
Rotor diameter
50
40
28 mm
30
20
10
0
0.15
1.2
Stator flux density (T)
A
Increasing rotor diameter
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
Lamination axial length to diameter ratio
Effect of stator flux density
B
A
95.4
95.2
95
95.6
95.4
A
B
95.2
95
94.8
0.4
0.5
0.6
0.7
0.8
Stator flux density (T)
0.9
1
94.8
0.01
0.015
0.02
0.025
0.03
0.035
Lamination axial length (m)
0.04
60
96
55
B
50
95.8
45
Efficiency (%)
96
95.8
Influence of Winding Inductance
Diode conduction angle (deg)
96
95.8
Efficiency (%)
Efficiency (%)
Influence of Design Parameters on Efficiency
95.6
Variation of efficiency with rotor-to-stator diameter
ratio, and airgap length
Effect of active length-to-diameter ratio
40
35
30
25
20
A
95.6
A
95.4
B
95.2
95
15
10
0.15
94.8
0.2
0.25
0.3
Phase self inductance (mH)
0.35
10
20
30
40
50
60
Diode conduction angle (deg)
34
SENSORLESS HIGH-SPEED BRUSHLESS DC
MOTORS
Comparison of Alternative Motor Designs
Motor A
• More iron, less copper
• Low stator flux density
• Long stator core length, same motor
length
• Less turns/coil, lower winding
inductance
• Low diode conduction angle
• Narrow stator teeth and back-iron
• Short end winding
• High unbalanced magnetic pull
• Suitable for sensorless control
Prototype 120,000rpm Sensorless HighSpeed PM Brushless Motors
Motor B
• Less iron, more copper
• High stator flux density
• Short stator core length, same motor
length
• More turns/coil, high winding
inductance
• High diode conduction angle
• Wide stator teeth and back-iron
• Long end winding
• Low unbalanced magnetic pull
• Unsuitable for sensorless control
A
Measured and Predicted Voltage and Current Waveforms
100
80
60
M e a s u re d
P r e d ic t e d
40
Voltage (V)
20
0
0
0 .0 0 0 1
0 .0 0 0 2
0 .0 0 0 3
0 .0 0 0 4
0 .0 0 0 5
0 .0 0 0 6
-2 0
-4 0
-6 0
-8 0
-1 0 0
T im e ( s )
Sinusoidal back-emf waveform
Phase Back-emf
2
Measured
Simulated
1.5
Low diode conduction angle
Current (A)
1
High conduction angle, almost
continuous current waveform
0.5
0
-0.5
0
0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007
-1
emf
emf
-1.5
-2
Zero-crossing
No zero-crossing
Time (s)
Phase current, 125krpm
Phase terminal voltage
Phase terminal voltage
emf
emf
Zero-crossing
Line terminal voltage
No zero-crossing
Line terminal voltage
Spin
pot
Buffer
Vessel
Prototype motors A and B (120krpm, 1.25kW)
Diffusion
pump
Vacuum
pump
Test Rig for High-Speed Brushless Permanent Magnet Machines
35
DIRECT FORCE CONTROL OF A NOVEL TWOPHASE TUBULAR MOTOR
Motor Parameters
Quantity
Magnitude
Number of turns per phase
101
S
Pole-pitch, [mm]
18
N
ID of armature bore, [mm]
N
90
°
S
vb
44.8
OD of armature bore, [mm]
88
Active armature length, [mm]
112
S
Magnet thickness, [mm]
10
Mass of armature assembly, [kg]
4.1
N
Payload, [kg]
2
S
Phase resistance, [Ω]
N
b)
0.51
Synchronous inductance, [mH]
3.7
Mutual inductance, [mH]
0.23
Nominal current (rms), [A]
Electromagnetic force, Fe [N]
174
Back emf, e [V]
45
Mechanical power, P [W]
314
140
Forcem [N]
1.8
Fr
Fa
Velocity
160
Faster force control can be achieved by employing direct force
control (DFC), which is highly effective in compensating for the
cogging force.
1.44
1.08
120
0.72
100
0.36
80
0
60
-0.36
40
-0.72
20
-1.08
0
-1.44
-20
-1.8
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time, [s]
7
Two-phase
tubular PM motor
Iab
Icd
5
Current, [A]
Encoder
Optimum
switching
voltage
vector
table
0.140
180
Although it is widely acknowledged that vector control (VC) is a
well-advanced technique for achieving fast motor control, it can
be rather ineffective when the motor has a significant cogging
force, since this makes precise electromagnetic force control
difficult at low speeds.
Two-phase full H-bridge inverter
5
Permanent magnet flux, Ψm [Wb]
Electrical model of two-phase
tubular PM motor
Velocity, [m/s]
va
3
1
-1
-3
-5
-7
Active
/
Reactive
0
Direct force control structure for two-phase tubular PM motor
The key advantage of employing a two-phase full-H-bridge
inverter for the direct force control of the two-phase tubular
motor is that it yields eight, rather than six, basic space
voltage vectors. An increased number of voltage vectors is
desirable since, both the motor currents and the
electromagnetic thrust force are then smoother.
V2[1010 ]
iii
Im
Fr ↓, Fa ↑
Fr ↑, Fa ↑
V4
ii
i
V6
V8
Fr ↓, Fa ↓
Fr ↑, Fa ↓
viii
vii
V7[ 0001]
V8[1001]
0.6
0.7
0.8
0.9
1
Iab
Icd
5
Re
sector i
V6[ 0101]
0.5
7
clockwise
rotation
V1[1000 ]
vi
0.4
Despite the presence of cogging force, the feedback
velocity is maintained constant at low speeds. The
distorted motor currents reflect the nature of the
cogging force, which can fluctuate randomly. For
comparison, the motor currents under rated load are
shown below.
V2
ψa
V5[ 0100 ] v
0.3
Performance of direct force control on no-load
when only cogging force component exists
(Velocity demand equal to 0.36 m/s)
b)
a)
a) Active voltage vectors of full-H-bridge inverter
b) Flux and force control in sector one
Current, [A]
V3[0010 ]
iv
0.2
Time, [s]
Force Estimator
V4[0110 ]
0.1
3
1
-1
-3
-5
-7
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time, [s]
36
ACOUSTIC EMISSIONS FROM DIRECT TORQUE
CONTROLLED INDUCTION MACHINE DRIVES
Space vector PWM results in a concentrated current
harmonic spectrum and tonal acoustic noise
emissions, whilst both random PWM and direct
torque control result in wideband a harmonic spectra
and less irritating atonal acoustic noise.
Deterministic PWM
Random PWM
Time Domain
3-phase, 6-pole, 1.5kW
induction motor
36 stator slots/32 rotor slots
Current Spectra
Noise spectra
Space Vector Domain
(a) SVPWM, fs = 2.25kHz
Converter
Torque Ref.
Hysteresis
bandwidths
Flux Ref.
Torque & Flux status
Switching states:
Optimal Sa, Sb, Sc
DC
flux
switching
hysteresis Torque status
table
controller
AC
(b) RPWM, fs = 1-4kHz
Optimal
flux
controller
ωr T
(c) DTC, fs = 1.7-2.4kHz
Comparison of current and acoustic noise spectra with SVPWM,
RPWM and DTC, (span=12.5kHz, RBW=32Hz)
Flux position
Motor flux
Motor torque
Sa, Sb, Sc
Flux &
torque
estimator
DC link voltage
Current
M
Rotor speed
Direct Torque Controlled Induction Machine Drive
37
EMC, MEASUREMENTS AND MODELLING OF
POWER ELECTRONICS / DRIVE SYSTEMS
Amplitude (dBuV/m)
EMC test facility
The EMD group has an EMC pre-compliance test facility, consisting of a
broadband receiving antenna, a Farnell SSA1000A, 150kHz to 1GHz spectrum
analyser, and near field test probes for measuring radiated emissions, and a
single-phase 6A line impedance stabilisation network (LISN) for the
measurement of conducted emissions.
Equipment Under Test
80
60
40
20
Broadband Antenna
0
0
3m
400
600
800
1000
Frequency (MHz)
Open Area Test Site (OATS)
The Group has access to an antenna test site in
Buxton, where far-field measurements may be
taken with relatively low background emissions
Ground Plane
Broadband receiving
antenna and tripod
200
Typical EMC test result taken at 3m.
Spectrum
Analyser
3m
Layout of a 3m open area test site.
EMC Near field measurement
The EMD group has both H-field and E-field probes for near-field measurements within systems. They provide a useful tool for locating ‘hotspots’ for radiation, and allow mapping of the EMC performance of a given circuit geometry. Detailed investigations can highlight individual
harmonics of the fundamental circuit operating frequency.
Near Field Probe
Noise Amplitude (dB µV)
70
Controlling Chip
Transformer
Output stage.
Output leads, 275V
Input leads, 12V
Noise Amplitude
(dBµV)
70
8.5
Switching Transistors and Rectifier Diode
Mounted on Heatsink Below Circuit Board
Layout of small, 20W SMPS showing
main features.
z
42.5 mm
35 mm
2 mm
x
y
35 mm
100 mm
5mm
120 mm
Typical heatsink used in small power
electronic systems.
0
0
5
15
Frequency (MHz)
11.5
Frequency (MHz)
H-field from SMPS showing
switching harmonics.
Finite difference time domain (fdtd) modelling
Power switching devices form the major source of
noise in power electronic systems, since they are
mounted on a metallic heatsink, which will become a
resonant structure at some frequency. Resonance of
the heatsink will affect the overall system EMC
performance, and the location of the device on the
heatsink will affect the relative field strengths across
the structure.
65-70
60-65
55-60
50-55
45-50
40-45
35-40
EMI 30-35
dBµ V 25-30
20-25
70
60
50
40
30
20
1 2 3
1
3
9
5
7
cm
11
4
5
6
7
cm
8
9
13
10 11 12
Map of 4.1 MHz harmonic from small SMPS,
5cm from circuit board.
Modelled Data
Measured Data
z
10 dB
0
-10
-20
x
Radiation pattern prediction
The time evolved field strengths over the surface of the heatsink
may be converted into a radiation pattern, which may be
compared to measurements made in a screened anechoic
chamber.
Modelled near-field radiation from the heatsink due to excitation of resonances
by power device mounted in central channel.
38
SILICON CARBIDE POWER ELECTRONIC
DEVICES
Wide band-gap semiconductors offer:
Applications
•
Higher temperature operation: potential for
junction temperatures over 600 C
•
Higher electric field at breakdown: potential to
overcome voltage blocking limitations of Si
•
Greatly increased power densities
High Temperature Applications
SiC
Si
GaAs Derived Benefits
Band-gap
(eV)
3.26
1.1
1.43
Breakdown
Electric Field
(x 106 V/cm)
Thermal
Conductivity
(W/cm.K)
2.2
0.25
0.3
4.0
1.5
0.5
•
•
•
•
•
High Power Density Applications
Higher temperaure
operation
Lower leakage
Thinner active
region, lower onresistance
Higher power density
•
•
•
•
•
•
For a majority carrier device, SiC gives 53 times greater
power switching capability per unit area compared to Si
Si
SiC
2.2
3.2
1.1
Layer thickness
2
On resistance
R~ d
µN
~ 1
µE
Low loss power electronics
Transmission and distribution systems
Electric vehicles
Rail, marine traction
Power conversion
Integrated motor drive systems
Improved switching performance of SiC
Schottky diodes
180
EC
Doping density N ~ EC
0.25
Bandgap (eV)
d~ 1
Jet engine sensors, actuators, control electronics
Spacecraft power conditioning
Deep well drilling
Industrial process control
Automotive engine sensors
Clamped inductive load switching at 25C.
Red trace SiC, blue trace 1200V hyperfast Si pin diode
1
3
C
25
Critical Field (MV/cm)
0
20
-100
Max Tj (K)
Power switching capabilty
5
0
-5
53
1.5
-200
10
Vd (V)
4.0
Pmax = Vbr J on ~ λ (TJ max − TC )µεEC3
Id (A)
1000
500
15
-10
-300
-400
-500
-15
Thermal Conductivity W/(cm K)
-600
1
-20
-700
-25
0
100
200
300
400
500
0
100
Time (ns)
SiC bipolar devices can operate at much higher voltages
and higher switching frequencies than their Si
counterparts:
• Eliminate/reduce series device connection
• Higher electrical efficiency
300
400
500
Time (ns)
current
Bipolar SiC devices for transmission and distribution
applications
200
voltage
Si PiN SiC
SiC vs Si
Peak reverse current
Ipr (A)
17.5
3
17%
Reverse recovery time
Trr (ns)
51
19
37%
Recovered charge
Qrr (nC)
446
28
6%
Diode loss
Eoff Diode (µJ)
139
9
6%
IGBT loss
Eon IGBT (µJ)
198
149
75%
35000
30000
SiC Packaging Technology
25000
Poff, diode
20000
Pcond, diode
Poff, switch
15000
Pcond, switch
10000
Pon, switch
5000
0
1000A,
10kV Si
IGBT/Si
diode
10kV Si 2x(5kV Si 2x(5kV Si 3x(3.3kV 4x(2.5kV 1000A,
IGBT/SiC IGBT/Si IGBT/SiC Si IGBT/Si Si IGBT/Si 10kV SiC
diode
diode)
diode)
diod e)
diode) IGBT/SiC
diode
Predicted losses (W) for various 10MVA switch element
configurations operating from a 5 kV dc bus at a switching frequency
of 500 Hz. Using a SiC diode reduces losses to 70% of those for 10
kV Si devices. A full SiC solution reduces losses to 16% of those
with 10 kV Si devices
Issues:
•
High junction temperature
•
Deep thermal cycles
•
Die attach (solder?)
•
Interconnect (wire bond?)
?
300 C pressure contact
package (Kansai/Hitachi)
Solutions:
•
High MP solder, TLP bonding,
pressure contacts
•
Careful Tc matching,
mechanical design
39
8.
Marine
SENSORLESS CONTROL OF MATRIX CONVERTER
FOR THRUSTERS ON DEEP-SEA ROV’S
Introduction
• Manufacturers of work-class deep-sea Remotely Operated Vehicles (ROVs) are
looking towards replacing traditional drive systems viz: hydraulic thruster
actuators, by electrically-driven counterparts.
• The perceived advantages are: higher reliability, mass reduction, improved control,
higher efficiency (leading to reduced umbilical diameter & drag) .
• Operation of the thruster power converters at high pressure (300-bar) eliminates
the need for local 1-bar pressure chambers, and additional ballast.
• Sensorless operation of permanent magnet brushless ac thruster motors eliminates
the need for discrete rotor position sensors and associated conditioning electronics
and signal connections (between motor and inverter).
In addition the
machine/thruster design is simplified since specialist seals are not necessary, and
the overall reliability is improved.
Work-Class ROV
(Photograph courtesy of Perry Slingsby Systems)
3φ –3φ matrix converter
•Provides direct conversion between the AC supply and the thruster motor, with
amplitude and frequency control.
•Accommodates 4-quadrant operation.
n
Input filter
A
L
B
L
swAu
swAv
swAw
C
L
swBu
swBv
swBw
swCu
swCv
u
swCw
v
C
(a)
C
C
(b)
Electrolytic capacitor (a) Before pressure cycling.
(b) After pressure cycling at 300bar
swXxR
•Eliminates conventional two-stage conversion and the need
for no pressure-sensitive dc-link capacitor.
•Facilitates pressure tolerant drive at expense of additional
power switching devices.
w
Matrix converter
PM brushless ac machine
swXxF
Bi-directional switch
Observer-based rotor position estimation
•Feedback linearisation controller employed to present observer with linear motor
dynamics.
•Allows linear observer-based design techniques to be employed for estimating state.
•Unobservability of rotor position in ‘linearised’ d-q coordinates countered using
correction scheme to accommodate offset, drift and divergence.
•An additional state variable readily included into structure for load torque estimation.
Va ref
Vb ref
Vc ref
Matrix
converter
Observed rotor position and rotor position error
under steady-state condition
PMSM
abc
dq
[vd
abc
vq
[i
]T
[ud
+
dq
uq
motor model
f(x,u)
+
d
iq
]T
Luenberger
observer
]
T
[iˆ
d
iˆq
]
+
Feedback
Linearization
-
T
ω̂
∆ω
∫
θˆ
vd
[i
d
iq
]
T
calculate v d'
Correction
Feedback linearisation followed by application of linear state-estimator
Observer under transient load operation: 0.2Nm applied at ≈0s
40
HIGH SPEED PERMANENT MAGNET
GENERATOR
1.5MW gas-turbine generator set for
‘more-electric’ ship applications
20,000rpm direct-drive permanent magnet
generator
Permanent magnet rotor with carbon-fibre
over-wrap
300mm diameter rotor - subjected to high
levels of mechanical stress
Finite element predicted stress
in magnet and carbon-fibre
Standstill
20,000rpm
Large pre-compression applied at standstill
to strain-match components at 20,000rpm
Design synthesis
Mechanical
FEA
Magnetostatic FEA
Viable rotor
dimensions
Open-circuit emf
Phase inductances
Saber
circuit
simulation
Current
waveform
Rotor loss
Magnetodynamic
FEA
(transient)
Thermal
model
Stator iron loss
Magnetostatic FE +
iron loss
prediction
Scaled demonstrator
120kW, 20,000 rpm
2 rotors manufactured - with and without
copper screen
Comprehensively instrumented for validating
loss models
Copper screen rotor prior to banding
41
9.
Rolls-Royce University Technology Centre in Advanced Electrical Machines
and Drives
42
10.
Facilities
EMD
Facilities
Surface-Mounted PCB
Manufacture
CNC Wire Eroder
Ic
Battery
Bidirectional
DC/DC
converter
SuperCapacitor
VDC
Traction
Motor
Inverter
CNC Lathe
IB
140
Traction Machine
ENHANCED
ECE CYCLE
120
speed [km/h]
Supercapacitors
100
80
60
40
20
0
200
400
600
800
1000
1200
V DC
240
140
Ic (A)
250
0
-150
I B (A)
400
0
‘Brass-Board’ Electric Vehicle
Power-Train
Environmental Test Chamber
CNC Milling Machine
Capacitor-Discharge Magnetisers
43
EMD
Facilities
High-Speed Test Rig
Calorimeters
Environmental Test Chamber
Acoustic Noise & EMC Measurements
Dynamometers
Magnetic Materials Characterisation
High Power Machine (±120kW, ±20krpm)
Test Cell
44
11.
Magnetic Systems Technology Ltd
MST
Magnetic Systems Technology Ltd
¾ Co-founded in 1992 by Professor David Howe and Mr Marcus Jenkins, under the auspices of
UniShef Ventures.
¾ Manufactures high performance permanent magnet brushless machines/drives for private,
public service and industrial vehicles.
¾ Hybrid technology is finding applications in military vehicles for both combat and logistical
roles. The high power generally demands a series hybrid configuration in which an IC
engine-driven generator provides electrical power to drive a directly coupled electrical drive.
High mobility, 18-tonne, 6x6 load carrier
Compact electrical generator comprising
a close-coupled engine/generator, power
dump and power electronic controller
¾ MST’s hub-mounted electrical drive comprises a brushless machine, 2-speed gearbox and
mechanical braking system.
Each drive has a peak power output of 100kW and a continuous
power of 50kW, with a maximum output torque of 20kNm – which
allows the vehicle to operate in skid steer mode.
¾ Lower power applications favour a parallel hybrid configuration in which the conventional
clutch housing is replaced with a custom-designed unit which integrates the clutch with a
permanent magnet brushless machine. This facilitates both hybrid and pure-electric modes,
and enables the machine to operate as a generator to charge the batteries.
Military land rover
Parallel hybrid power-train
Parallel hybrid drive
Magnetic Systems Technology Ltd
60 Shirland Lane
Sheffield S9 3SP, UK
Tel. +44 114 2448416; Fax. +44 114 2448417
E-mail: info@magtech.co.uk
45