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 10 faculty from EECS, 2 Senior Research Engineers, 7 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 a continued expansion of its automotive related research, very positive results from its research on gel polymer actuators and sensors, and major advances in power system control and modeling.
Professor John G. Kassakian, Dr. Richard D. Tabors, and graduate students Khurram Afridi and Vahe Caliskan, with funding from Mercedes-Benz, have enhanced the multi-attribute trade-off analysis tool, MAESTrO, and made it available to 9 automotive supplier and OEM companies. They have also developed a computer based tool for simulating the energetic performance of automobile electrical systems.
Professor Steven B. Leeb, with graduate students Deron Jackson, Aaron Schultz and Ahmed Mitwalli, has developed a 2800 W electric vehicle battery charging system employing a non-contacting magnetically coupled connector system. Field testing of the prototype will begin this year. A bidirectional version of the system is under development. Its ability to discharge as well as charge a battery is essential for insuring maximum battery life.
Professor Jeffrey Lang and graduate student John Ofori have continued their development of high torque, low mass motors for automotive applications. The direct drive wheel motor and its controlling electronics have been constructed and tested separately. They are now undergoing combined system tests. A new project started this year is the design and evaluation of a combined starter/alternator/drive-assist motor to operate in parallel with a diesel engine. The new motor/engine system is expected to offer a propulsion system that is smoother and quieter than the conventional gasoline engine.
Under the direction of Professor Kassakian, the laboratory has initiated a Consortium on Advanced Automotive Electrical and Electronic Systems. The purpose of the consortium is to support high-risk research on advanced concepts, provide members access to the laboratory's research results, and to make available to members the trade-off analysis tool MAESTrO and support its continued development. It presently has 9 members from the US, Europe and Japan. The consortium is an outgrowth of the workshops on automotive electrical systems that the laboratory has hosted for the past two years. The work of this group has been completed, and its results will be presented in both Detroit and Germany in the fall.
Utility industry restructuring has placed an intense focus on achieving economically optimal system operation by employing new and more sophisticated control and monitoring strategies. LEES has been making significant contributions to the solutions of problems of economic control, modeling, and apparatus monitoring.
Professor Bernard Lesieutre and his students have been encouraged by their theoretical results in developing load models for use in power system studies. They are now pursuing methods by which to estimate power system load composition in an on-line environment. With Professor Leeb, they are analyzing harmonic components of current waveforms to identify certain load components. The results of this research, funded by the National Science Foundation, will allow a greater understanding and enable more precise control of power system dynamics.
Professor George C. Verghese, with Professor Lesieutre and researchers from Electricité de France, have continued their work on large-scale power system model reduction using the Synchronic Modal Equivalencing framework. Tests over the past year have resulted in a well defined procedure for accurate model reduction of intermediate size power systems. They are now pursuing the expansion to very large power system models.
Dr. Marija Ilic and her students have continued their investigation of power system operation and planning problems created by the deregulation of the electric utility industry. Dr. Ilic and former Ph.D. student Shell Liu have recently published a research monograph, Hierarchical Power Systems Control: Its Value in a Changing Industry, summarizing the results of this work. Under sponsorship of the U.S. Department of Energy, Dr. Ilic is studying the operating fundamentals of the distributed utility of the future - a power system that is comprised of many distributed small-scale, potentially clean, electric energy sources.
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.
Under funding from the Boston Edison Company, Professor James L. Kirtley, Professor Lesieutre, Mr. Wayne Hagman and Mr. Paul Warren have developed a system of monitors for continuous real-time surveillance of operating power transformers. Five transformers on the Boston Edison system are now being monitored. The ability of this system to provide detailed information about transformer operation has allowed the system to be operated closer to its real capacity. An evaluation by Boston Edison indicates operational savings in excess of $2.5 million in the first year of monitoring activity.
As part of the transformer monitoring project, Professors Lesieutre and Kirtley, Mr. Hagman and students have developed new nonlinear models to describe important thermal and dissolved-gas-in-oil dynamics in large power transformers. These physically based models are essential components of the adaptive on-line monitoring and diagnostic system. Their studies have resulted in a significantly improved transformer thermal model that facilitates the detection and diagnosis of certain transformer problems and allows better evaluation of the present condition for purposes of dynamic loading.
Professor Leeb, in collaboration with Professor Leslie K. Norford of the Department of Architecture, and with graduate student Steven R. Shaw, has been developing techniques to permit the parallel processing Non Intrusive Load Monitor (NILM) demonstrated last year to serve as a platform for performing critical load diagnostics and power quality monitoring. Preliminary experiments conducted in LEES and in MIT buildings E25 and E40 have indicated that it is possible to non-intrusively diagnose the condition of critical motors in building ventilation systems and industrial manufacturing facilities. This ability provides an inexpensive means to schedule preventive maintenance in critical path electrical loads. An early version of the NILM intended for residential monitoring has been commercialized and is under beta test with 10 utilities around the country.
Professor Lang, Professor Martin A. Schmidt of the MTL, and graduate student Jo-Ey Wong have continued their development of the micromechanical relay for power switching in automotive applications. This work has been performed in parallel with a fundamental study of micromechanical relay contacts. To date, the study has demonstrated that micromechanical relay contacts can stand off hundreds of volts when open, and appear capable of exhibiting contact resistance as low as several milliohms when closed. Based on the results of the study, a fully functional relay has been designed, and its fabrication is now in progress.
Professor Lang and graduate student Steven Nagle, in collaboration with other faculty in the School of Engineering, are developing a micromechanical compressor/combuster/turbine/generator which promises to produce electric power with a power density near 100 W/cm3. The LEES work has focused on the design of the generator and its power electronics, and a proof-of-concept model is now under construction. When successful, the overall project will represent a major advancement in portable electric power supplies.
The Novice Design Assistant, a computer aided tool for designing three-phase induction motors developed by Professor Kirtley and graduate student Ujjwal Sinha, has been extended by Professor Kirtley and graduate student Mark Thomas to the design of large, multi-disk wound field and permanent magnet machines for ship propulsion. The tool is being modified to make it applicable to the design of ac generators and single-phase induction motors.
Professor Lang and graduate student Ed Lovelace have completed the design, construction and testing of a controller for the variable-reluctance motor which operates without the usual rotor position sensor and shaft encoder. Instead, the controller estimates rotor position from the information contained in sparse measurements of phase voltages and currents, thus making a more economical and rugged system.
Professor Leeb, in collaboration with Professor Toyoichi Tanaka of the Center for Materials Science and Engineering, and with graduate students Ahmed Mitwalli, Deron Jackson and Changnan Wang, have developed a technique for incorporating 10 to 100 micron diameter metal flakes in aqueous solvent polymer gels. The presence of transition metals was found, in general, to inhibit the free-radical polymerization process through which gels are formed. It has been found that the process will occur if the metal particles are first coated with high molecular weight polyvinyl alcohol before the assembly of the pre-gel solution. The resulting interpenetrating polymer network (IPN) permanently entrains the metal flakes. This gel can be triggered to exhibit a volume phase transition by applying an ac magnetic field which induction heats the flakes. Because solvent can leave and enter IPN gels without removing the induction targets (unlike the ferrofluid solvent gels developed last year), the IPN gels could serve as the basis for the development of a variety of non-invasively triggered industrial and medical chemical release applications.
Also demonstrated this year by Professor Leeb and his students was a thermo-optical sensor employing a gel formed from an interpenetrating polymer network of polyvinyl alcohol and a copolymer of N-isopropylacrylamide and acrylic acid. This gel exhibits a continuous volume-phase transition that is strongly dependent on the presence of polyvalent metal ions in the gel solvent. A sensor apparatus has been constructed that estimates the transition temperature of a gel. When this sensor is loaded with a gel sensitive to metal ions, it can be used to detect the presence and identity of those ions in solutions. Any thermally responsive gel whose transition characteristics are affected by an environmental parameter of interest could be used in this sensor. Work is underway to develop gels whose phase transition characteristics are strongly affected by the presence or absence of specific target molecules.
Professor Martha Gray and her group continue their work on the use of magnetic resonance (NMR) for measuring composition and functional integrity of cartilage. The fixed charge density of cartilage is one of the most important factors in reflecting the mechanical integrity of cartilage. They have used NMR methods to exploit the fact that there is a quantitative relationship between the concentration of fixed and mobile charges. With this approach they have been able to identify focal lesions in intact joints and small explants of cartilage, and to obtain near histological three-dimensional resolutions of fixed charge density. Recent pilot studies suggest that this method may be feasible clinically and in animal models.
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. A low-power prototype system has been built to evaluate the current sharing control schemes developed last year. Results have been excellent, and new funding from the Office of Naval Research has been obtained to support continued development of the concept.
Professor Anantha Chandrakasan and his students have been developing strategies for energy efficient computing to minimize the energy dissipated per data sample in systems where the computational workload varies with time. They are using a technique that adaptively minimizes the power supply voltage for each sample. The idea is to lower the supply voltage and clock frequency during reduced computational workload periods instead of working at a fixed high voltage and allowing the processor to idle. A factor of 5 improvement is expected in some applications. A chip has been fabricated and tested to verify stability and the functionality of static and dynamic logic circuits. They are currently building an MPEG-2 video decoder with an embedded power supply to test the idea in a large system.
Professor Markus Zahn and graduate student Afsin Üstündag have developed a mathematical formulation that allows reconstruction of an applied electric field from light intensity measurements using electric field induced birefringence (Kerr effect) even when the magnitude and direction of the electric field varies along the light path. Graduate student Tza-Jing Gung has performed confirming experiments using needle/plane electrodes stressed by high voltages.
Graduate student Darrell Schlicker, working with Professor Zahn, has greatly improved the MIT Couette Facility used to study the electrification of oil due to flow in power transformers. The beneficial effects of lowering flow electrification using the anti-static additive benzotriazole (BTA) has been confirmed and continuing experiments are comparing the behavior of new oils with used oils taken from operating transformers.
As part of a new NSF/EPRI supported research program on sensors for power systems, graduate student Alexander Mamishev, working with Professors Zahn and Lesieutre, has greatly improved the MIT developed three-wavelength dielectrometry sensor to maximize signal to noise and to minimize cross-coupling effects between wavelengths. Such sensors are being applied by graduate student Yanqing Du to study the absorption and diffusion of moisture and anti-static additives, particularly in power transformers.
John G. Kassakian
MIT Reports to the President 1995-96