MIT Reports to the President 1994-95

Laboratory for Electromagnetic and Electronic Systems

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.

Adaptive Monitoring Of Transformers
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.

Non-Intrusive Load Monitoring
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.

Electrical Machines
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.

Gel Polymer Actuators
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.

Biological Electromechanics
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