EDL AB N ET
ELECTRIC DRIVES LABORATORIES NETWORK
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET
The seat of Electric Drives Laboratories is by EDLab Padova, located at the Department of Electrical
Engineering (DIE) in Padova. It works in tight collaboration with other the two Laboratories of the net,
located at the Department of Engineering and Management (DTG) in Vicenza, and the Department of
Electrical, Management and Mechanical Engineering (DIEGM) within the University of Udine.
EDLab net’s activity is mainly devoted to the design and development of advanced electrical
machines and drives. The Labs of the net shares high-level equipments and instrumentation, and they
work on twin test benches, for the sake of an easy and profitable exchange of information and results.
DIEGM
University of Padova
University of Padova
University of Udine
Dept. of Electrical Engineering
(DIE)
Dept. of Technology and
Management of Industrial Systems
(DTG)
Dept. of Electrical, Management
and Mechanical Engineering
(DIEGM)
via Gradenigo 6/a
Stradella S. Nicola, 3
Via delle Scienze, 208
35131 Padova - Italy
36100 Vicenza - Italy
33100 Udine - Italy
silverio.bolognani@unipd.it
mauro.zigliotto@unipd.it
roberto.petrella@uniud.it
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET ACTIVITY OUTLINE
BRIEF HISTORY
The first laboratory of the net was started during the 90’s in Padova, with the aim of
reinforcing the research activity on electric drives, until then theoretical, and to participate to
research projects proposed by industrial partners.
The early years’ research was oriented to innovative motor control techniques, such as fuzzy
logic control, sliding mode control and sensor-less control. Studies on the design of electric motors
was following, first regarding Surface Mounted PM (SPM) synchronous motors and then Interior
Permanent Magnet (IPM), pure reluctance (REL) synchronous motors and induction motors (IM).
For each case, both rotating and linear versions were considered. Many designs evolved to
industrial products, put on the market by the industrial partners of the laboratory.
In year 2000, in connection with the transfer of one of the senior researchers of EDLab to the
University of Udine, a new structure was started, i.e. EDLab-UD. Part of the research activities in
the field of electrical drives moved from EDLab-PD to EDLab-UD, further enriched by research on
drives and models for automotive, in particular for the steer-by-wire systems. In year 2006 a new
permanent researcher position was created at the University of Udine within the field of electrical
drives control, with the aim of extending the staff of EDLab Net, also gaining additional
competences in high-performance digital controllers and power electronics design for electrical
drives.
Also in year 2006 a brand new research structure has started in Vicenza, in connection with the
first-degree course in Mechatronics of the Faculty of Engineering of the University of Padova
(decentralised seat). The EDLab-VI is actually a part of the integrated laboratory on Mechatronics,
in Vicenza, and its start-up activity is on advanced control of ac drives.
The present EDLab Net’s research activities include research and development of advanced
electrical motor drives for industrial, commercial and residential applications. A part of the
activity is supported by Italian Ministry of Education, University and Research (MIUR), in the
frame of Research Projects of National Interest (PRIN/FIRST Programs). Also local Universities, the
European Community (by Craft or similar Projects) and, as a consistent quote, private contractors
(i.e. mainly local industries active in the field) provide financial support to the activities of EDLab
Net.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
KEYWORDS
EDLab NET activities and competences can be found by combining two or three
keywords, one for each of the following groups:
1) Object: PM synchronous motor, Surface-mounted PM synchronous motor, Interior PM
synchronous motor, Inset PM synchronous motor, Axial field PM synchronous motor, Reluctance
synchronous motor, Induction motor, Rotor-wound induction motor, Single-phase induction
motor, Linear PM motor, Tubular PM motor, Torque motor, Power electronic board, Digital
controller.
2) Topic: Electromagnetic design and optimization, Finite element analysis, Electronic HW design,
Torque ripple minimization, Efficiency Optimisation, Cogging torque minimization, Fault tolerant
motor and/or control, Fractional slot winding, High speed, High torque, Speed sensor-less control,
Position sensor-less control, Time-optimal current control, Time-optimal torque control, Random
PWM, Flux-weakening control, Motion control, Parameter identification, Parameter measurement,
Self-tuning.
3) Application: Industry, Machine tool, Hand tool, Light electric traction, Ship propulsion, Lift and
crane, Automotive, Steer-by-wire, Electric energy generation, Home appliance, Heating ventilation
and air conditioning (HVAC), Pump, Wind generator, Mini-hydraulic, Micro-turbine.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET’S PERMANENT STAFF
Silverio BOLOGNANI (EDLab-PD, Director)
bolognani@die.unipd.it
Silverio BOLOGNANI is a native of the Trento province, in the North of Italy. He received
the Laurea degree in Electrical Engineering from the University of Padova, Italy, in 1976. In
the same year, he joined the Department of Electrical Engineering at that University, where he was involved
in the analysis and design of thyristor converters and synchronous motor drives. After that, he started the
Electrical Drives Laboratory where a variety of researches on brushless and induction motor drives are
carried out in the frame of European and National research projects. He is presently engaged in researches
on advanced control techniques for motor drives and motion control and on design of ac electrical motors
for variable speed applications. He is author of more than 200 papers on electrical machines and drives. He
has been serving International Conferences as member of the Steering or Technical Committees. He was for a
long time Member of a Working Group of CPV (Centro Produttività Veneto, an Agency of the Chamber of
Commerce of Vicenza for continuous education and technology transfer), and President of an Association of
local Industries in the Power electronics and Electromechanical fields. At present he is Chairman of the IEEE
North Italy IA/IE/PELS Joint Chapter. His teaching activity was first devoted to Electrical Circuit Analysis
and Electromagnetic Field Theory and, later, to Electrical Drives and Electrical Machine Design. He is now
Full Professor of Electrical Converters, Machines and Drives and Head of the Department of Electrical
Engineering at the University of Padova.
Nicola BIANCHI (EDLab-PD)
bianchi@die.unipd.it
Nicola BIANCHI is a native of Verona, Italy. He received the Laurea and Ph.D. degree in
Electrical Engineering from the University of Padova, Padova Italy, in 1991 and 1995
respectively. In 1998, he joined the Department of Electrical Engineering of the same University, as Assistant
Professor in Electrotechnics. Since 2005 he is an Associate Professor in Electrical Machines, Converters and
Drives. He is working by the Electric Drive Laboratory at the Department of Electrical Engineering of the
University of Padova, engaged in researches on the design of electrical machines, especially for drives
applications. In the same field, he is responsible for various projects for local and foreign industries. He is
member of IEEE IA and PES Societies and member of the Electrical Machines Committee and the Electrical
Drives Committee of the IEEE IA Society. He is author and co-author of several scientific papers on electrical
machines and drives, and of two international books on the same subject. His teaching activity deals with the
Design Methods of Electrical Machines, where he introduced the finite element analysis approach as part of
the course, and with Electromechanical Systems for Aerospace.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET’S PERMANENT STAFF
Mauro ZIGLIOTTO (EDLab-VI)
mauro.zigliotto@unipd.it
Mauro ZIGLIOTTO is a native of Vicenza, Italy. He received the Laurea degree in
Electronic Engineering from the University of Padova, in 1988. Later, he worked in industry,
as responsible of R&D in microcontroller-based control systems for electric drives. From 1992 to 1999, he was
a Senior Research Assistant in the Electric Drives Laboratory at the Department of Electrical Engineering of
the University of Padova. From 2000 to the end of 2005, he joined the Department of Electrical, Management
and Mechanical Engineering of the University of Udine, as Associate Professor of Electric Drives, and there
he started the Electric Drives Laboratory (EDLab-UD). Since 2006, he is with the Department of Technique
and Management of Industrial Systems (DTG) of the University of Padova, located in Vicenza. Innovative
control strategies for ac motors are Prof. Zigliotto’s main research interest, and he has published extensively
in this area. He serves International Conferences and Journals as reviewer and member of the Steering or
Technical Committees. He is the Secretary of the IEEE IAS-IES-PELS North Italy Joint Chapter.
Roberto PETRELLA (EDLab-UD)
roberto.petrella@uniud.it
Roberto PETRELLA was born in Pescara, Italy, in 1971. He received the M.S. degree in
electronic engineering, with honours, and the Ph.D. degree from the University of L’Aquila,
L’Aquila, Italy, in 1996 and 2001, respectively. He received praise from the evaluating commission of his
thesis final project for the excellent results obtained in the development of a research and industrial system.
He joined the Department of Electrical Engineering of the University of L’Aquila as a Research Fellow and a
Post-Doctoral Fellow from 2001 till 2005. Since 2006 he’s with the Department of Electrical, Management and
Mechanical Engineering of the University of Udine, as Researcher of Electrical Drives. His main research
interests include advanced control of electrical drives (including vector control, energy efficiency
optimisation techniques, estimation techniques, and sensor-less control), digital motion control, and highperformance DSP-based systems for real-time control. He has authored more than 45 technical papers on
these topics. The research activity has been developed both within the frame of University Research Projects
and in collaboration with local industries. He serves International Conferences and Journals as a reviewer
and he is an official lecturer for Texas Instruments’ motor control workshops in Italy.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET COMPONENTS AND COLLABORATORS
- Gabriele Marchesi
(Associate Professor in Electrical Material and Technology)
- Ernesto Benini
(Researcher in Mechanical Engineering)
- Branimir Ruzojcic
(Consultant, Tema o.o.d., Pula, Croatia)
- Luca Sgarbossa
(Research Assistant)
- Luca Peretti
(3nd year Ph.D. Student)
- Luigi Alberti
(3nd year Ph.D. Student)
- Diego Bon
(2nd year Ph.D. Student)
- Manuele Fornasiero
(2 nd year Ph.D. Student)
- Massimo Barcaro
(1 st year Ph.D. Student)
- Adriano Faggion
(1 st year Ph.D. Student)
- Mosè Castiello
(Technician)
- Marco Bullo
(Technician)
- Roberto Losco
(Technician)
- Elvio Castellarin
(Technician)
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UNIVERSITÀ DEGLI STUDI DI PADOVA
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EDLAB-PD ACKNOWLEDGMENTS
ISO 9001- VISION 2000 - For the sake of a qualified relationship with the
industrial partners, a competent body, according to the quality standard
UNI EN ISO 9001- Vision 2000, has recently certified the EDLab-PD.
DEPARTMENTAL EVALUATION - During 2006, the Department of Electrical Engineering of
the University of Padova has been submitted to an evaluation of the activities of its
Research Groups (Research Programmes). EDLab resulted in a clear leading position
among all the Departmental Research Groups. The following is extracted from the Final
Evaluation Report filled by the expert Panellists.
This report is the result of an evaluation exercise undertaken in Padova over the period 6th - 8th November
2006. The evaluation was carried out by a team of international experts having knowledge and expertise
relevant to the programmes of research being undertaken in the Department of Electrical Engineering
........
(a) Programmes in which the research is of a leading international standard
Electrical Drives - The evaluation panel considered this research program to be of international quality and
to compare very favourably with leading electric drives groups elsewhere. In reaching this conclusion, the
panel considered the projects being undertaken, the number of students being educated, the interaction with
both Italian industry as well as the broader international research community, and the dissemination of the
research results in terms of conference and archival journal publications. The current projects within the
group were found to be of significant research and economic interest, both with respect to local Italian
industry and in terms of attracting students. As specific examples, the panel noted the projects relating to
drives for automotive power steering applications, systems for direct drive applications and the high
efficiency drive for an inner city electric scooter. In all instances, the projects incorporated the essential
characteristics of theory, design and experimental validation. The level of activity in the program was found
to be very high, the students were enthusiastic, and overall research direction had focus and coherence.
The panel was impressed with the level of research funding that has been available to the group, both from
national competitions and from local industry. The panel noted, in particular, the success that has been
achieved in reaching out to local industry for support. The funding has obviously resulted in the
development of excellent research facilities for design and testing. The panel specifically noted the availability
of several experimental test benches for motor parameter extraction and drive system testing. The research
output of the program, as measured by the quality and number of publications, was found to be excellent.
The work is published regularly in strong archival journals and is presented regularly at leading
international conferences. Additionally, there are strong contacts with most of the leading international
electric drives groups. The panel was also impressed with the regular symposia that have been organized to
present the research in the program to local industry. The panel is confident that the group will continue to
attract strong funding and significant numbers of students.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
EDLAB NET EQUIPMENTS
EDLab NET is equipped with the following test facilities.
Automatic Motor Test Bench for Static Measurements – It has been specifically designed and realized for
automatic tests of synchronous motors. The motor under test is supplied by means of a dedicated currentcontrolled inverter while the braking motor is supplied by means of a standard inverter. The first inverter is
commanded by a current hysteresis control, so
that any current waveform can be forced in the
motor phases. The standard inverter-fed motor
drags the motor under test at a very low and
constant speed through a high ratio gear. Both
motor drives are commanded by a DSP-based
board programmed by a PC. A torque-meter is
used to measure the shaft torque; an encoder and
three Hall current sensors measure position and
currents. Possible programmed measurements
are the following:







cogging torque vs. rotor position;
automatic detection of the d-axis and q-axis of the rotor;
current vector angle to carry out the maximum torque at given current;
torque vs. rotor position at given dc stator current;
torque ripple under load;
torque for different combinations of d- and q-axis currents;
differential inductances, by injecting high-frequency voltages.
Automatic Motor Test Bench for Dynamic Measurements – It has a similar structure of the previous test
bench, but without gear coupling. The motor under test is driven at an appropriate speed. Voltages applied
to the motor are also measured. Possible programmed measurements are:



detection of the d-axis and q-axis of the rotor,
flux-current characteristics;
motor efficiency.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
Fast Control Prototyping (FCP) test benches – They have been specifically designed for the fast test and tuning of
advanced control algorithms for electrical drives. They are based on well-known dSpace FCP boards
(www.dspace.de) combined with Matlab/Simulink®
software. The dSpace cards are plugged into a host PC
and connected via a self-designed interface to a
standard voltage inverter. Novel PWM techniques
and/or current and speed controls are first simulated,
then rapidly compiled and downloaded to the dSpace
card, exploiting a user-friendly PC-based humanmachine interface. The high quality software trace
utility reduces the development time with respect to
the standard hardware prototype based solutions,
which also suffer of dependence to the adopted
processor. Sensor-less speed control for surface
mounted PM synchronous motors and induction
motors, flux-weakening algorithms for IPM motor
drives, novel PWM techniques have already been
developed up to a pre-industrialised level. The motors
framework can be adapted to lodge a torque-meter
for mechanical power measurements at the shaft.
Steer-by-wire test bench, with virtual load capability – It commands a couple of brush-less motor drives
(one plays the role of motor and one implements the virtual load, with programmable load torque profile).
They are axially connected a by elastic joint. Joint
elasticity, motor and load inertia and backlash
can be adjusted for experiments of motion
control. In particular, experimental comparison of
different speed controllers for two-mass systems
has been extensively investigated. Slowresonance ratio controllers, full and augmentedorder state controllers, fuzzy logic controllers are
among the implemented control strategies.
The laboratories are also equipped with high accuracy, full-optional oscilloscopes (Tektronix TDS 5054),
torque meters (MAGTROL TMB 308), wide-bandwidth power meter (POWERTECH PPA 2500), several
industrial and custom voltage inverters and motors.
EDLab NET uses proprietary and commercial software packages for motor and drives analysis and
simulation: finite element field analysis (ANSYS, ANSOFT, FEMM), time domain dynamic analysis,
controller design tools, simulation and analytical analysis tools (MATLAB-SIMULINK) for motor
performance prediction. There are ten complete positions for motor and drive control simulations.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
SEMINARS AND WORKSHOPS
EDLab research activities have been hardly promoted within the industrial framework and many
times they are carried out by a friendly support of industrial partners.
Technical-scientific workshops (AC Motor Drive Technolgy Workshop) were organized in the
industrial district of Vicenza to meet industrial people and to stimulate common projects.
S.Bolognani was for a long time Member of a Working Group of CPV (Centro Produttività Veneto,
an Agency of the Chamber of Commerce of Vicenza for continuous education and technology
transfer), and President of an Association of local Industries in the Power electronics and
Electromechanical fields.
EDLab competences are recognized at international level:
- In 2001 N.Bianchi and S.Bolognani were invited as lecturers for a Post-graduated Seminar
at the Helsinki University of Technology. Notes were prepared and distributed to the
students.
- In 2004, N.Bianchi co-organized with T.Jahns the Tutorial Course "Design, Analysis, and
Control of Interior PM Synchronous Machines" during the 2004 IEEE Industry Applications
Society Annual Meeting, Seattle, USA.
- EDlab team components were invited as speaker in special sessions, tutorials or panels in
high ranking international conferences (IEEE-IECON, IEEE-PESC, IEEE-IAS, EPE, EPEPEMC, IEEE-VPPC, ...).
- Several seminars were organized in Padova, Vicenza and Udine in collaboration with CPV,
IEEE, AEIT and other, inviting also international speakers (Williamnson, Rajashekara,
Jansson, Boldea, Bose, Holtz, De Doncker ....)
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
RESEARCH PROJECTS
Application of Synchronous Motor Drives to High Efficiency City-Scooters – The project was
carried out during years 2001 and 2002 in collaboration with other Italian Universities. The research
aimed to the study and development of PM synchronous motor drives for electrical scooters in the
urban cycle. The project yielded the development of innovative
interior permanent magnet synchronous motors, with a patented rotor
configurations that exhibit Ld>Lq. The advantages came in terms of
overload and flux-weakening capability. In addition to the motor
design, EDLab have been involved in other topics such as the design of
the flux-weakening control of the drive. For the presentation of both
scientific results and prototypes of the whole national project, the 2003
Workshop “AC motor drive technology” was organized in collaboration with CPV and held in
Vicenza. Invited speaker was Prof. B. K. Bose. More recently the responsible of EDLab UD was
involved in a research project in collaboration with another Italian University and a Company for the
development of a prototype of an electric scooter, both the power electronics and control subsystems
and firmware. The control board is based on the last generation microcontroller DSP from Texas
Instruments, an 84V dc power bus and a MOSFET based high-current three-phase inverter.
Energy efficiency improvement in electric drives for home and civil appliance – It was oriented to
the study of new design criteria for both the electrical machines and drives, aiming at
increasing power efficiency, particularly for home appliance systems, such as
refrigerators and wash-machines, with rated power below 1 kW. The project was
carried out in 2002-2003 in collaboration with other Italian Universities. The use of
Soft Magnetic Composite materials and new configuration of the stator of PM motors
were investigated in EDLab-PD. An industrial partner realized a prototype of the
motor. The scientific results and the prototypes of the whole national project were
presented at the 2004 Workshop “AC motor drive technology”, organized in
collaboration with CPV and held in Vicenza.
Innovative electric drive for power steering – The main purpose is studying, designing and realising
electric motors and drives for the automotive scenario. The project was carried out during years 2004
and 2005 in collaboration with other Italian Universities, focusing in particular on EPS (Electric Power
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UNIVERSITÀ DEGLI STUDI DI UDINE
Steering) and SBW (Steer-by-Wire) applications. The final design of the steer-by-wire system foresees
two electric drives: the first performs the steering action, controlling the wheels by means of the
steering rack and two motors which work in hot redundancy for the sake of reliability. IPM
synchronous motors with innovative rotor configurations have been specifically designed for the
steering actuator. The second drive is
responsible of the torque feedback through
the steering wheel; in this case, a SPM
synchronous motor with fractional-slot
windings has been used. Major features of
the proposed IPM motor drives were the
following:

smooth torque with minimum ripple;
high efficiency;
 fault-tolerance,
which
is
an
imperative requirement in electric motors
for steering application. In particular,
each IPM motor must exhibit very low
braking torque in case of a short-circuit
fault, allowing the second motor to temporarily manoeuvre the vehicle. Precise criteria have
been determined and experimentally verified to design the IPM motor for a limited shortcircuit current and low braking torque.
minimum package size and weight (for that purpose, a rotating motor with gearbox has been
preferred in comparison with a direct drive system).


As regards to the control strategy, the algorithm for the simultaneous control of both drives has
been developed and tested. The IPM motor drive requires an accurate position control to achieve the
desired steering angle, while at the same time the feedback motor must be controlled by a suitable
torque feedback signal that guarantees an appropriate steering feel. An intensive work is still in
progress with the purpose of obtaining a more precise model for the mechanical dynamics of the
steering system. Results of this analysis will be included in the Human-In-the-Loop (HIL) simulator
that is already present at EDLab premises. Such HIL simulator is composed by a third electric drive
and a SPM motor, mechanically coupled with the IPM motor, which reproduces the behaviour of the
mechanical steering system. At this time, the HIL simulator works with a reduced mechanical model of
the steering system. A continuation of the project, supported by surplus funds, has been planned in
EDLab-PD premises. The purpose is to complete motor tests installing the real mechanical steering
system designed by the partners of the University of Bologna. Tests will also include electric motor
drives and control strategies final evaluation.
Permanent magnet synchronous motor drives for ship propulsion – It pertains the study, design and
testing of electric and mechanical components for a naval propulsion unit, making use of synchronous
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permanent magnet motors. The aim of the project is also to define an electro-mechanical design
methodology, strongly integrated with both the control and the dynamics of the driven load. The
project has been proposed and financed during 2005, in collaboration with researchers of the Dept. of
Mechanical Engineering in Padova and researchers of the University of Helsinki (Finland). Direct drive
sub-jet propulsion system for high-speed crafts is the solution that has been examined. Industrial
partners stated their interest for prototyping the drive. The first application is going to be the electrical
propulsion of the Vis (2 motors of 1000 HP each). Afterwards, the electrical propulsion will be applied
to high performance hybrid catamaran (2 motors of 25 kW each).
The admiral ship the Vis was constructed in 1956 at the Uljanik shipyard as the
elite staff officer ship of the Yugoslav Navy. Together with the renowned and
larger the Galeb, the Vis was the only ship with such purpose, and, opposed to the
Galeb, it was designed exclusively for that function. The ship is unique, designed
and manufactured as a luxury yacht, meeting the extremely high standards of final
elaboration. It is 58 metres long, the width of the widest part is 8,7 metres, with
the draught of 3 metres and the displacement of 670 tons. It was ran by two
motors of 1000 horsepower each, with three additional supporting aggregates.
Innovative motors and controls for electrical drives – The project was initiated by the Department
and financed by surplus funds of the EDLab-PD, resulting from concluded Research Contracts.
The aim of the project is twofold: to support both basic researches and preliminary start-up
studies, which will be possibly proposed for subsequent applied research. The following topics
were examined:
Sensor-less control of SPM synchronous drives – It addresses the problem of the tuning of the Extended
Kalman Filter algorithm, as well its extension to non-sinusoidal back-emf motors and IPM motors, for both the
constant power region and the flux-weakening region. The sensor-less strategy has been experimentally
evaluated with pull-in and pullout curves, and the laboratory prototype is now ready for industrialisation.
Some industrial partners have already purchased the non-exclusive use of the results.
Sensor-less position control of IPM motor drives – The drive uses the injection of a high-frequency
voltage signal superimposed to the steady-state voltage. The accuracy of the rotor position detection depends
strongly on the rotor saliency that is affected by the rotor geometry, saturation and cross coupling. As an
original contribution, it has been found that the inset motor is a very suitable machine for this control
technique. The rotor saliency is not very high, but it features low rotor saturation, so that a rotor saliency can be
detected even at high currents. This implies that the sensor-less technique can be effective even under overload
operating conditions. An inset motor prototype has been manufactured to confirm the predicted performances
and to compare them with those of an IPM motor using the same stator. This research attracts the attention of
prof. Seung-Ki Sul of National University of Seoul, with whom EDLab-PD is now collaborating.
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PM linear motors design – Several studies on PM linear motors have been carried out
in collaboration also with Prof. J.Corda (University of Leeds, UK). A new configuration
of a tubular PM motor has been designed with windings and PM excitation on the
same side, while the other side is passive (patented).
FPGA-based Intellectual Properties development – The major
weakness of all modern microprocessor-based electric drives is the
lack of software portability towards any product upgrade.
Application Specific Integrated Circuit (ASIC) technology provides a
rapid and low-cost solution for special applications with large
market. However, the longer development time and higher set-up
cost makes it improper for industrial drives, which are characterised
by rapid evolution and diversified applications. Field-programmable
gate array (FPGA) components are drawing much attention due to
shorter design cycles, lower cost, and higher density. EDLab NET
efforts are directed towards the creation of a library of optimised
VHDL modules that incorporates the best expertise on each part of
the drive. Implementation of a random SVM with dead time
compensation is the first successful example.
Time optimal control of current and torque in IPM synchronous motor drives – The Time Optimal Control,
well explained by Pontryagin’s theorem in System Theory, can be successfully used in electric drives to
realise a high dynamic electric drive with the fastest transitions between two torque levels. Among different
motor types, the most suitable one for a Time Optimal Control strategy is the IPM, since both the direct and
quadrature currents produce torque (two degrees of freedom). Different versions of the algorithm with
increasing performance have been developed and implemented both in DSP and FPGA devices.
Experimental tests confirm the theoretical predictions that a keen choice of voltage reference during large
torque transients can minimise the duration of the transient itself. Test bed for endothermic motors, in which
high-dynamic electric drives are used to reproduce disturbances on the motor itself, are suitable applications
for the Time Optimal Control strategy.
For the presentation of some of the
results
of
Workshop
this
project,
“AC
the
motor
2005
drive
technology” (focused on Linear motors
for
industry
applications)
was
organized in collaboration with CPV
and held in Vicenza. Invited speakers
were Prof. I. Boldea and N. Schofield
(University of Timisoara, Romania).
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
PM Motors with Fractional-Slot Windings – In the last years, stators with fractional-slot winding
for PM machines are becoming more and more attractive. This is due to two main reasons. The
first one is that a fractional-slot winding allows very short end windings to be achieved, especially
by the solutions of coils wound around a single tooth. The second one is that the effect of the
increase of MMF harmonics introduced by the fractional slot winding is mitigated by the low
magnetic permeability of the PMs in the airgap. The activity includes:




development of a suitable theory for the study of the fractional-slot windings;
criteria to investigate the winding feasibility;
criteria to find the MMF harmonics;
tests on fractional-slot winding motor prototypes.
The theory of fractional-slot winding based on the classical theory of the star of slots, as
originally proposed by Richter to study the back EMF of the first harmonics, has been extended to
study also the back EMF harmonics of various order as well as the harmonics of the MMF
distribution. An original contribution is the extension to single-layer winding. Special windings
(and the rules for their design) are under study. In particular, the focus is on windings committed
to get:



the lowest torque ripple: it is a key-point in many applications, especially in home
appliances, to reduce the acoustic noise;
null mutual coupling among the phases, required in fault-tolerant motors;
minimum stress on the rotor PMs.
Fault-Tolerant Motors and Drives – Fault-tolerant capability is a key issue in several emerging
applications in which a complete stop is a critical situation, as for example in automotive and naval
propulsion. The fault-tolerant systems have to satisfy two requirements:
1. capability to confine the fault to the damaged component and to isolate
it without propagation of the fault to the entire system;
2. capability to be operated even under faulty conditions.
It has been found that to satisfy the first requirement, the motor has to be
conveniently designed with a large leakage inductance to limit the shortcircuit current below a given threshold. Some motors have been
designed and prototyped. To this aim, the results obtained from the
analysis of the fractional-slot windings have been used, since these windings naturally exhibit a high
leakage inductance. As far as the second requirement is concerned, the designs of the motor and the
inverter cannot be kept distinct, and different solutions can be adopted. A multi-phase motor drive
can be designed, e.g. a six-phase or a five-phase motor without significant increase of the motor cost
and with a limited increase of the converter cost. Further drive design issues include:

an electrical separation among the phases: each motor phase fed by a full-bridge converter;
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE



a physical separation of phases, in order to prevent a phase-to-phase fault: each phase coil is
wound around a single tooth, with a single coil side per slot; this is possible only with a
fractional-slot winding motor;
a low mutual inductance among the phases, to prevent those healthy phases energize the fault;
re-configurable converter topology and control, in order to adapt them to the different faulty
situations.
Four motor prototypes have been designed and built in the Laboratory. Two of them are induction
motors, designed with six-phase windings. In case of fault of one of the windings, the other can
continue to operate, at reduced power. The other two motor prototypes are five-phase PM
machines, with fractional-slot winding, and they use a double-layer and a single-layer winding
respectively. The windings have been designed with a proper leakage inductances to reduce the
short-circuit current to 1.5 times the nominal current, and with no mutual inductance. A five-phase
full-bridge converter has been constructed.
Reduction of the Torque Ripple in Synchronous IPM and Reluctance Machines – A common
problem of synchronous machines with anisotropic rotor is their high content of torque ripple. The
interaction between spatial harmonics of the electrical loading and the rotor anisotropy causes a
high torque ripple that is intolerable in the most of applications. Classical remedies are:



stepped-skewing in PM motors with the rotor split in two or more parts, each of them skewed with
respect to the others;
a suitable choice of the number of flux-barriers with respect to the number of stator slots per pole;
the pole shifting: the flux-barriers are shifted from their symmetrical position, to get a sort of
compensation of the torque harmonics.
As an EDLab-PD’s original contribution, a novel strategy for synchronous motors with fluxbarriers in the rotor has been developed. It is based on a two-step design procedure: At first the
flux-barrier geometries that cancel the torque harmonic of one order are
identified. Then, couples of flux-barriers of different geometry are combined
together so as to put the remaining torque harmonics in opposition. This
second step is achieved in two ways: (i) by adopting laminations of different
kind; (ii) by adopting different flux-barrier geometries in the same
lamination. The first solution has been called "Romeo and Juliet" configuration; the second one is
called "Machaon" configuration, the name of the butterfly with two large wings and two small
wings. Promising results have been reached analytically and by simulations. Five motors have
been then prototyped to verify the analytical predictions (Patent pending).
High Torque-to-Inertia Ratio – This research was promoted by an industrial company that asked
the design of a motor exhibiting high dynamic performance, required in many applications, such
as machine tools, packaging machines, positioning machines and so on. The motor has been
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
designed for a high ratio between the torque and the rotor inertia. PM motors are suitable
solutions to meet such a requirement. A SPM motor has been chosen, even if an IPM motor with
tangential magnetization has been also considered for its higher air-gap flux density.
A stator with separated teeth was adopted: each single tooth was separated from the other,
allowing the coil to be wound around it with a very high filling factor. Then, the teeth were
assembled together to form the final stator.
An analytical model of the SPM motor is used to find the best configuration in term of the
maximum torque-to-inertia ratio on the constraint of given stator outer diameter.
After the design optimisation, two prototypes have been built (one is shown in the first figure of
this report). The first one was an SPM motor, while the second one was an IPM motor with
tangential magnetization. The two prototypes were tested both in EDLab and in the company
laboratory. The results were really satisfactory. Both the prototypes reach a torque-to-inertia ratio
about two to three times that of the standard brush-less PM motors. The maximum acceleration
(without load) with a stator current three times higher the rated one reaches a value equal to
87000 rad/s2 by the IPM motor, a little lower than the SPM motor that reaches a maximum
acceleration of 91000 rad/s2.
High Torque Direct-Drive PM Motors and Drives – High torque, direct-drive systems, used for lift,
hoist, winch and crane, yield lower plant cost, reduced spaces and negligible maintenance. In
addition, the machine room in elevator system can be eliminated. Two different types of surfacemounted permanent-magnet motor for direct-drive elevator systems were designed: the first one
with external stator and the second one with external rotor. The SPM motor is adequate for the
application. It exhibits a very high torque-to-stator joule losses ratio, which is suitable for the
intermittent duty required by the application. In addition, the high magnetic air-gap allows a
linear torque vs. current curve up to very high currents. The key characteristics and the design
criteria have been studied analytically to the aim of achieving general results. Afterward, FEM
simulations have been carried out to improve the design, considering torque ripple and local
saturations, which are not considered in the analytical study. The companies have manufactured
the two motors.
For the lift application, torque, speed and position
control has been also faced. Vector control is used and the
critical specification of controlling the cabin position
when the brake action is removed at any door closing in
under study. The activity on this topic is now moved to
the study of a PM motor for a direct drive wind
synchronous PM generator. Iron losses estimation and
thermal analysis are the main task of this work.
High Speed PM Machines – The research has been carried in order to design two PM machines, a
two-pole motor for a hand tool and a four-pole generator for local energy generation on trucks.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
As regards the first application, the required speed was 30,000 rpm and
the motor power about 1 kW. Different topologies were investigated, including
slotted and slot-less stator, laminated and sinterized stator, Ferrite and NdFeB
magnets. The geometry of each topology has been optimised taking into
account thermal, mechanical and magnetic limitations of the materials. After
this research, the most promising solutions have prototyped: a slotted machine
and a slot-less machine, both of them with NdFeB magnet rotor. Flux density
in various parts of the machine has been measured and compared with the analytically computed
one, obtaining a good agreement. The slotted stator-laminated solution has been chosen and
industrialized by the industrial customer.
The second application requires a flux-weakening capability. The maximum speed was
fixed to 12,000 rpm. The maximum-to-base speed range is about 3.5. The maximum back-EMF at
the maximum speed fixes a further constraint, in order to prevent excessive voltage. The external
dimensions were also fixed, so that an optimisation of the rotor structure was necessary to satisfy
the requirements. The machine rotor was optimised so as to achieve a high torque density, but
with a limited torque ripple, to avoid vibration and acoustic noise. A first prototype of the
electrical generator was manufactured and tested. The activity on this topic is now moved to the
design of a 60-100,000 rpm PM generator to be applied in a micro turbine system for electric
energy generation.
Inverter Control With Low Electromagnetic and Acoustic Noise – This research was originally
carried out with the purpose of reducing the acoustic noise levels in electric drives by means of
Random PWM (RPWM) techniques.
The subject has been recently
revitalized in relation with the
electromagnetic
compatibility
directives imposed by the EU, since it
has been demonstrated that a RPWM
inverter lowers the electromagnetic
conducted noise levels measured by the
standard operating procedures described in the directives. Some results have been achieved and published in collaboration with prof.
Andrzej M. Trzynadlowski (University of Nevada, USA). More recently, applications of RPWM
techniques for Power Line Communications (PLC) applications have been firstly proposed by EDLabVI, as a method for obtaining lower ground noise in a FSK power cable signal transmission. Such a
solution should be of interest for PLC applications in the harsh and noisy environment of industrial
electrical drives, in which several inverters, each with its own switching frequency, share a common
DC bus and harmonics can be predicted neither in amplitude nor in frequency.
From a technical point of view, efforts have been made to simulate and realize a low-medium
complexity RPWM suitable for fully digital industrial applications. Simple implementations with a
selection of pool frequencies have been studied, as well as methods for optimal selection of the
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
frequencies, and evaluated by experimental evidence, including EMC measurements. As a matter
of fact, it has been demonstrated that a simple algorithm with a limited pool of only two randomly
used frequencies can achieve important results in terms of EMC issues.
Industrial and Civil Applications of Magnetorheological Fluids – This research has been carried out
with the purpose of obtaining a comparison between magnetorheological fluids and electric drives for
industrial and civil applications, in which both of them can be a suitable solution (that is, for example,
suspension and brake systems). Magnetorheological fluids are a suspension of
iron particles, with a diameter of few microns, in a mixture of low-viscosity oils
and greases, which inhibit the sedimentation. In normal conditions, the mixture
behaves almost like a
Newtonian fluid, with
an inherent viscosity.
With the application
of an external magnetic field, iron particles
tend to form chain-like structures which
direction follows the magnetic field lines,
changing fluid's viscosity. In particular, the
fluid is no longer Newtonian and tends to
be viscoplastic, with a viscosity that
changes proportionally as function of the
magnetic
field
magnitude.
Magnetorheological fluid’s features are
interesting in particular for controlled brake applications, in which the total amount of braking torque
can be controlled by means of a variable external magnetic field supplied by a proper coil and a DC
converter. Two "home-made" magnetorheological fluids have been prepared at EDLab-VI premises.
They have been studied from both a magnetic (magnetic permeability and electric resistivity) and a
rheological (viscosity change as function of applied magnetic field) point of view. Also a self-designed
magnetorheological fluid-based brake has been manufactured, aiming at evaluating experimentally
fluids’ properties. Static braking torque characteristics (i.e. braking torque as function of applied
magnetic field) show to be of relevant interest, while more studies should be conducted to enhance
dynamic properties of the fluid-based brake, focusing in particular on electrical design of the excitation
coil and brake mechanical structure.
Speed Sensor-less IM Drives – The project comprises the design and implementation of a speed
sensor-less control for an induction motor (IM) drive to be used in washing machines, refining the
pre-existent sensored control implemented by the industry contractor and improving it with a
speed estimation algorithm. Such IM drive exhibits a large constant power region and a maximum
speed of 18000 rpm. A comprehensive study and simulation comparisons among different
sensor-less control strategies have been performed in the last months of 2005, in order to point out
potentials and pitfalls of the solutions proposed in literature. Major concerns were about
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
robustness against parameter variations, joined to cost and implementation issues due to the limits
imposed by the already existing hardware. Finally a novel scheme, obtained by improving existing
solutions and which comprises the required robustness and implementation easiness, has been
realized and simulated. Such solution has been subsequently implemented in one of the
Laboratory FCP stations and extensive tests have been performed to evaluate the algorithm in
terms of the required specifications.
Speed Sensor-less Control of IPM Motors – The project addresses the problem of speed sensor-less
control of Interior Permanent Magnet motors by means of generalised back-EMF estimation. IPM
motors are in fact still far from a large diffusion, one of
the reasons being certainly the difficult implementation
of a controller able to fully exploit its peculiarities, a
task strictly related to the specific motor design. The
saliency gives rise to quite strong non-linear operating
characteristics, often increased by saturation and
mutual axes interaction. To take advantage of the motor
features, the controller (either sensored or sensor-less)
must fit the motor characteristics as close as possible
and all over the whole operating range. Sensor-less
control of IPM motors in the low-speed region is
normally achieved by means of signal-injection based
techniques and high-speed operation with different
types of dynamical observers. The solution developed
in the project is based on the estimation of a fictitious back-EMF space vector by means of a
cascaded Sliding-Mode and extended Kalman filter state and disturbance observer. The estimated
rotor position and speed are then employed inside an optimised vector control scheme of direct
and quadrature motor currents trajectories. The control allows to fully exploiting the torque-speed
characteristic of the motor, also in the de
t*
sgn
R
ω*
fluxing region. Experimental validation of
ω̂
iq*
ω̂ ω̂
Vector
the solution was achieved by means of a
Fq
Ft
ω̂ ω̂
iq*
Controlled
self-designed control board (both power
abs
*
id
IPM Drive
electronics and processing). The controller
Fd
is based on a standard C DSP architecture
and a three-phase MOSFET inverter. The
vα* ,β iα,β
design of the system is fully compliant to
Extended
θ̂r
iq*
iq*
automotive specification, as asked by the
back-EMF
ω̂
Italian company who supported this
observer
ω̂
research.
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UNIVERSITÀ DEGLI STUDI DI PADOVA
UNIVERSITÀ DEGLI STUDI DI UDINE
Initial Rotor Position Estimation for PM Motors – This project was carried out to provide a mean
to start incremental-encoder-equipped PM motor drives without any absolute position transducer.
The application refers to packaging machines and has been developed for an important Italian
industry, within the frame of a regional research and innovation grant. The developed estimation
algorithm is based on the demodulation of induced oscillation of the rotor and virtually works
with any kind of PM motors (experimental tests have been carried out with “torque motors”). A
test signal is added to reference d-axis current and its effect on the movement of the rotor is
demodulated by a PLL based method in order to identify rotor position. The test signal is
dimensioned such that the rotor is only moved slightly from its
neutral position; in locked rotor conditions joint elasticity (i.e. some
encoder pulses) is enough to provide the oscillation of the rotor
needed to assure convergence of the estimation algorithm. The
method has been extensively tested both on a test-bench and in the
actual prototype of the packaging machine. Lot of comparisons with
high-performance commercial drive systems on same motors and
mechanical set-up have been carried out showing that, in some cases
(especially with high load-to-motor inertia ratio and/or varying
inertia of the load), those systems systematically failed to start the
motor. The proposed methodology can be easily tuned up and seems
to be insensitive to any variation of motor parameters. Only load
inertia affects the sensitivity of the method and some research is still
being developed in this direction. Also the re-design of the control
board (power electronics and processing) is going to be performed in
order to provide a custom made drive for those kind of applications.
Low-cost high-performance drive for automated doors – This project was carried out in
collaboration with an Italian company developing automated doors (e.g. sliding, etc.). The aim of
the project was to provide an higher-performance
alternative solution to commercial drives for automated
doors and gates. The drive system is based on a dc
actuator, a low-voltage four-quadrant converter and an
extremely low-cost low-performance C. Some
innovative functions were introduced at the behavioural
level of the door, such as the collision detection algorithm
and movement trajectory control. The system has been
extensively tested, both on a commercial brake and on a
laboratory test-bench emulating the behaviour of the
automated door.
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UNIVERSITÀ DEGLI STUDI DI UDINE
EUROPEAN RESEARCH PROJECTS
EDLab was involved in some European Research Projects. Two Craft projects have been recently
concluded successfully in collaboration with European Universities and Industrial Companies.
Self-commissioning of electrical drives with identification of mechanical load – The project was
dedicated to develop control structures for the speed and position control of mechanical load
connected to electrical drives by non ideal joints. Joint elasticity, backlash and friction were
considered. In addition different motor to load inertia ratios have been assumed. Identification
algorithms were developed to determine load parameters. According to them and to the control
specification the most suited speed and position controllers are chosen by a Fuzzy Knowledgebased System and their gains automatically tuned.
Submersible electrical motor – The project was aimed to develop a 6 inches, high efficiency squirrel
cage submersible asynchronous motor, designed for 45 kW (50% higher than the maximum rating
power of the motors manufactured by the industrial proposer of the project) to be used in
connection with pumps within 6 inches wells, improving at the same time characteristics of
reliability, environmental compatibility and reduced maintenance which are even more important
for systems operating at high depths. The project started on June 2002 was concluded successfully
in 2004 by testing a prototype of the motor with positive results. Finite element magnetic and
thermal analysis, combined with an optimization procedure was used to design the motor in
cooperation with mechanical designers of the Department of Mechanical Engineering.
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EDL A B N E T
ELECTRIC DRIVES LABORATORIES NETWORK