MIT
Reports to the President 1994-95
The mission of the Laboratory for Electromagnetic and Electronic Systems (LEES)
is to be the focus for research and teaching in electric energy from its
production through its processing to its utilization, and in electromechanics
from the macroscopic through the microscopic to the molecular levels. Electric
energy and electromechanics are defined broadly to include power systems
monitoring and operation; automatic control; power electronics; high voltage
engineering; and conventional, continuum and biological electromechanics. Much
of the work of the laboratory is experimental, and industrial sponsorship
represents a large fraction of the laboratory's support. The laboratory's
professional staff consists of 11 faculty from EECS, 2 Senior Research
Engineers, 8 research staff, and approximately 50 graduate students. The
laboratory faculty and most of the staff are heavily involved in both
undergraduate and graduate teaching. Faculty from the departments of ME, CE,
MS&E and NE are collaborators in many of the laboratory's programs, and
there are extensive joint activities with the Microsystems Technology
Laboratory (MTL) and the Energy Laboratory. LEES is also an active participant
in the Leaders for Manufacturing Program, the New Products Program, and the
Program in Technology Management and Policy. During the past year the
laboratory has experienced an expansion of its automotive related research,
very positive results from its research on performance based monitoring and
control, and the creation of a new program on the use of silicon carbide for
power semiconductor devices.
The past year has seen dramatic changes in the electric power industry. Within
the US these changes have been seen in the regulatory, economic and financial
environment within which the sector operates, and with it the engineering and
systems requirements of the industry as a whole. LEES has contributed
significantly in both the engineering and the institutional developments of the
industry. Drs. Marija Ilic and Richard Tabors have taken leading roles in the
national debate on the questions surrounding the new industry environment,
providing written and oral testimony before both federal and state regulatory
commissions on the process and realities of industry restructuring.
Dr. Ilic and her students have participated in the discussions of the General
Agreements on Parallel Paths (GAPP), an effort by east coast utilities to
develop new technical and economic logics for system operations. Dr. Ilic and
graduate students Xiaojin Liu, Assef Zobian, Brian Eidson and Jeffrey Chapman
have developed the first generation of a range of algorithms for systems
control in a more competitive, less cooperative electric utility industry
environment. Dr. Ilic and Mr. Chapman were awarded a patent on a nonlinear
control technique for large synchronous generators, and Dr. Ilic and Mr. Liu
were awarded a patent on a technique for directly controlling power flows on
transmission lines using Flexible AC Transmission Systems (FACTS) devices. Dr.
Ilic was the editor of a special issue of the International Journal of Electric
Energy Systems dedicated to FACTS technology.
Professor George Verghese, working with Professor Bernard Lesieutre and
students from LEES, as well as with collaborators at Electricité de
France, leads a research effort that has, in the past year, introduced a
powerful new framework for reduced-order dynamic modeling (or dynamic
equivalencing) in power systems. The approach, dubbed Synchronic Modal
Equivalencing (SME) and described in the recent doctoral thesis of Ganesh
Ramaswamy, extends the conceptual basis of earlier paradigms, and provides
sound algorithms for each of the steps involved in the equivalencing process.
SME holds promise of evolving into the preferred approach for dynamic
equivalencing. Current work is centered around intermediate-sized models,
involving on the order of fifty generators. Future work will deal with much
larger models.
Professor Verghese has also been working over the past year in the area of
fault-tolerant signal processing. An algebraic approach to the topic (for
computations in semigroups and semirings) was pursued in the Masters thesis of
Christoforos Hadjicostis, and the work was recently awarded the EECS
Department's Guillemin Prize.
During the past year, Professor Lesieutre has been involved with several
projects related to the study of nonlinear dynamics in power systems. He has
been awarded a Research Initiation Award by the National Science Foundation to
develop new models to describe the dynamics of loads in the power grid. Also,
as a part of this project, he is studying occurrences of nonlinear oscillations
and has developed a method for identifying the variables that contribute
significantly to this phenomenon. It is expected that this result will further
the basic understanding, and enable more precise control of this dynamic
behavior.
LEES will be hosting the North American Power Symposium in September 1996.
This conference has a twenty-year history, and has traditionally had high
academic participation, with a strongly student-oriented focus. Professors
Lesieutre and Verghese, and Dr. Ilic, comprise the organizing committee of
the conference.
With funding by a consortium of electric utilities and EPRI, Dr. Tabors, Mr.
Wayne Hagman and Professor Lesieutre, with Professors James Kirtley and George
Verghese and a team of graduate and undergraduate students, are working to
develop smart, responsive monitoring and control hardware and software systems
for large power equipment (today transformers, in the future both breakers and
transmission lines). This work has led to research and development sponsored
by Boston Edison for on-line monitoring of four critical at-risk transformers.
During the last year, LEES developed the software and hardware systems for
monitoring, analysis and communications, and maintains 24 hour surveillance of
these transformers. Significant results have included the automatic detection
and manual diagnosis of dissolved-gas anomalies and problems with
previously-installed sensors, and the provision to Boston Edison of detailed
abstracted information concerning the operation, state and condition of their
transformers, and the provision to MIT of on-line large power transformer test
beds for models, software, and diagnostic systems.
Professor Steven B. Leeb, in collaboration with Professor James L. Kirtley,
was awarded a patent for the prototype Nonintrusive Load Monitor demonstrated
in the laboratory last year. With graduate student Umair Kahn, Professor Leeb
has completed a full-scale prototype with recently fabricated printed circuit
boards. This prototype will be tested in buildings on the MIT campus during
the 1995-96 academic year.
With funding from Mercedes-Benz, Professor John G. Kassakian, Dr. Tabors, and
graduate students Khurram Afridi and Vahe Caliskan, have been designing new
architectures for automotive electrical systems. They have developed a powerful
tool using multi-attribute trade-off analysis that permits comparison of a
large number of different complex designs. The tool and initial results have
been presented in both Stuttgart, Germany and Detroit. LEES has, as part of
this activity, organized a series of workshops with participants from
automobile manufacturers and suppliers to explore the forces driving changes in
the automotive electrical systems of the future, and to generate a consensus
regarding the parameters of a new system.
Professors Lang and Kirtley, with graduate student Mary Tolikas, have
constructed and tested a large variable-reluctance motor suitable for driving
an electric automobile. It appears that the motor will perform nearly to
specification, and full power tests are to be performed very soon.
Professor Lang and graduate student John Ofori have designed an electric drive,
comprising a motor and its power electronics, for passenger vehicle propulsion.
The important feature of the drive is that the motor exhibits a very high ratio
of torque to mass, nearly a factor of two greater than previous designs. It is
thus suitable for direct wheel drive. Placing the motor directly in the wheel
of a vehicle eliminates the conventional gearing and power transmission, and
the associated losses, mass and cost. Construction and testing is planned for
the near future.
With graduate students Aaron Schultz and Ahmed Mitwalli, and funding from AMP
Incorporated, Professor Leeb has developed a 500 watt prototype of a battery
charging system for electric vehicles employing a non-ohmic,
magnetically-coupled connector system. A patent application has been filed for
the battery charging control scheme and prototype described in last years
report.
Professor Lang and graduate student Eckart Jansen, in collaboration with
Professor Stephen Senturia of the MTL, have fabricated a new generation of
planar micron scale electric motors, or micromotors, out of silicon. These
micromotors have optical rotor position sensors beneath the rotor, and are
designed to permit the first closed-loop precision control of a micromotor.
The sensors have been tested and found to work well. Experiments are now
underway to implement closed-loop control. Ultimately, these motors will be
used to explore the limits of precision motion control which can be achieved
with microelectromechanical mechanisms.
Professors Lang and Schlecht and graduate student Jo-Ey Wong, in collaboration
with Professor Martin A. Schmidt of the MTL, have begun a new project to apply
silicon microfabrication technologies to the development of millimeter-scale
power relays. Their potential advantages include low cost, small size, low
power dissipation and fast switching. To date they have fabricated structures
to measure the electrical breakdown of miniature relay contacts, and have found
the breakdown voltage to be more than satisfactory for a variety of commercial
applications. They are now fabricating structures to measure the electrical
and mechanical behavior of those contacts during closing, conduction and
opening.
The Novice Design Assistant, a computer aided tool for designing induction
motors developed by Professor Kirtley and graduate student Ujjwal Sinha, has
been delivered to Magnetek. They are looking for ways of applying the concepts
embodied in the Novice to other important design issues, perhaps involving
electric power system design.
Professor Kirtley and forner graduate student Dr. Timothy McCoy have
demonstrated a centrifugally assisted thermosyphon for cooling the rotors of
very large, low speed synchronous motors. The technique is particularly
applicable to electric motors for ship propulsion.
Professor Leeb, in collaboration with Professor Toyoichi Tanaka of the Center
for Materials Science and Engineering, and with graduate students Ahmed
Mitwalli and Deron Jackson, are the first to have demonstrated magnetically
triggered gels. Gels have been synthesized which employ ferrofluids as
solvents. High frequency magnetic fields can be used to develop localized
heating in the gel solvent, causing the gel to exhibit a radical, reversible
volume change. Work is in progress to develop a variety of actuators with this
material, including magnetically triggered synthetic muscles and an in
vivo, magnetically triggered drug release system.
Professor Martha Gray and her group continue their work in understanding and
monitoring cartilage diseases. One major finding has been that interleukin-1, a
cytokine thought to be involved in cartilage degradation, appears to minimally
influence chondrocytes (the cells of cartilage), but rather acts through other
cells (e.g., synovial and endothelial cells) inducing them to produce and/or
activate enzymes which, in turn, degrade the cartilage tissue. This finding has
important implications regarding how cytokine-mediated degradation could be
slowed or prevented.
One other of Professor Gray's major research activities has been the
development of magnetic resonance methods for measuring the composition and
functional integrity of (1) initiating animal studies to monitor cartilage
degeneration and (2) extending the techniques for use in more cellular, less
dense tissues with an initial focus on monitoring wound healing.
Professor Alan Grodzinsky and his students have continued their study of the
effects of mechanical, chemical and electrical forces on the degradation,
synthesis and repair of cartilage. Recent results have shown that a family of
enzymes made by cartilage and joint lining cells can damage the collagen and
proteoglycan molecules of cartilage and lead to specific deterioration of
tissue electromechanical properties. Working with colleagues from Brigham and
Women's Hospital and Lund Hospital, Sweden, they have shown that a
nondestructive diagnostic surface probe may be able to detect and image the
presence of focal defects in cartilage similar to those in early stages of
osteoarthritis. This electromechanical spectroscopy technique has been patented
and is being adapted for use in arthroscopic examination. Experimental results
have shown that synthesis of new cartilage tissue by chondrocytes can be
enhanced by applied cyclic compression similar to that encountered in moderate
exercise. Experiments in collaboration with Genzyme Tissue Repair are focusing
on the ability of mechanical forces to alter the genetic expression of cells to
favor cartilage development.
Professor Kassakian, with graduate students David Perreault and Robert Selders,
have further demonstrated the practicality and advantages of the cellular
architecture for power electronic systems. In this architecture, a converter
system is composed of autonomous converter cells designed for a fraction of the
total system rating. Control techniques have been developed that force equal
currents in the cells without the use of intercell communication, thus
considerably enhancing system reliability. Two patent disclosures have been
filed on the technique.
Professor Schlecht, in collaboration with Drs. George Kenney and John Haggerty
of the Materials Processing Center, and Mr. Dennis Rathman of the Lincoln
Laboratory, is pursuing an important new approach to making power semiconductor
devices using silicon carbide. Such devices have the potential to reduce
on-state resistance by a factor of 300 relative to silicon based devices, and
they can operate at much higher temperatures. The work includes new high
temperature packaging techniques.
In work sponsored by North American Philips, Professor Schlecht and his
students have created a new power circuit topology for electronic ballasts that
should reduce the part cost by 20%, compared to existing designs.
Professors Schlecht and Anantha Chandrakasan, with Professors Charles Sodini
and Harry Lee of the MTL, and Professor Mitchell Trott of the Laboratory for
Information and Decision Systems (LIDS), have put together an ARPA funded
program to investigate low power consuming electronic circuit technologies for
wireless applications.
With grants from internal sources including the James H. Ferry, Jr. Fund, the
Soderberg Chair, and a curriculum development grant, along with nearly $500,000
in donated new equipment from Tektronix and Intel, Professor Leeb has
established an electronics prototyping laboratory in LEES. This facility is
becoming a premier facility for the assembly of analog, digital, and power
electronic circuits, and was used this year to support a new class, the
Advanced Mechatronics Project Laboratory.
Professor Verghese has contributed a chapter on dynamic modeling and control
in power electronics to a forthcoming CRC Handbook of Control.
Dr. Chathan Cooke has developed and applied new methods to determine the status
and condition of insulating materials and electric power apparatus. The
methods enable internal measurements of materials and equipment and are being
used for inspection tests and while energized. In cooperation with utility
industry sponsors, initial tests on power cables and power transformers were
begun on full-size apparatus, some in-service. Test results with large
cross-linked-polyethylene cables have shown that true internal stresses can be
much greater than the applied average stress due to stress-localization
phenomena. Measurements on large power transformers have demonstrated the
detection of important prebreakdown events.
Professor Markus Zahn and graduate student Afsin Ustundag have successfully
made measurements of the electric field distribution along the ground plane and
along the axis of symmetry in transformer oil using point/plane electrodes and
the Kerr electro-optic technique developed by Professor Zahn. These
measurements agreed with past analyses that were limited to cases in which the
direction of the electric field in the plane transverse to the direction of
light propagation was constant along the light path. A new analysis has been
completed for axisymmetric geometries that allow measurements to be taken for
arbitrary directions of electric field along the light path.
Professor Zahn and graduate students Alexander Mamimishev and Yanqin Du have
developed an experimental facility and methodology for measuring the time and
space distributions of moisture in oil/pressboard insulation systems.
Preliminary measurements have shown the capability of the MIT developed three
wavelength dielectrometry sensor to relate permittivity and conductivity
distributions to moisture distributions.
Professor Chandrakasan, a recent addition to the EECS faculty, has joined LEES
and is working with Professor Schlecht in newly refurbished LEES facilities in
building 38.
On July 1, 1994 Professor Zahn became the Director of the EECS VI-A
Internship Program.
Mr. Eliot Frank was promoted from Research Engineer to Principle Research
Engineer.
Professor Grodzinsky has left LEES to join the new MIT Center for Biomedical
Engineering as Associate Director for Facilities. He and his group won an NIH
Merit Award for their work on cartilage metabolism.
John G. Kassakian
MIT
Reports to the President 1994-95