| What's Really Happening With The ODU Maglev? | |
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General Maglev Technology: (1)
Magnetic levitation (maglev) is a relatively new, train-like, transportation technology (since the 1930s) in which vehicles are levitated slightly above the ground by large electromagnets. The vehicles are then guided and propelled forward, again, usually by electromagnetic means. Instead of rails, as in a conventional system, the cars travel slightly above a guideway, which is the physical structure along which maglev vehicles move. Various guideway configurations, e.g., T-shaped, U-shaped, Y-shaped, and box-beam, made of steel, concrete, or aluminum, have been constructed. The maglev cars do not physically touch the guideway surface, thus there is no rolling friction, and very high speeds are possible (about 300 mph) in long runs.
Figure 1
Figure 1 depicts the three primary functions basic to maglev technology: (1) levitation or suspension; (2) propulsion; and (3) guidance. In most current designs, electromagnetic forces are used to perform all three functions, although a nonmagnetic source of propulsion could be used. No consensus exists on an optimum design to perform each of the primary functions.Suspension Systems
The two principal means of levitation are illustrated in Figures 2 and 3. Electromagnetic suspension (EMS, Figure 2) is an attractive force levitation system whereby electromagnets on the vehicle interact with and are attracted to ferromagnetic rails (permanent magnets) on the guideway. EMS was made practical by advances in electronic control systems that maintain the air gap between vehicle and guideway, thus preventing contact.
Variations in payload weight, dynamic loads, and guideway irregularities are compensated for by changing the strength of the electromagnetic field in response to vehicle/guideway air gap measurements.Electrodynamic suspension (EDS, Figure 3) employs electromagnets on the moving vehicle to induce currents in the metal part of the guideway. Resulting repulsive force produces inherently stable vehicle support and guidance because the electromagnetic repulsion increases as the vehicle/guideway gap decreases. However, the vehicle must be equipped with wheels or other forms of support for "takeoff" and "landing" because the EDS will not levitate at speeds below approximately 25 mph. EDS has progressed with advances in cryogenics and superconducting magnet technology.
Figure 2
Figure 3
Figure 4: Lift coils off; EMS maglev car rests on guideway
Figure 5: Lift coils on; EMS maglev car floats above guideway
The ODU Maglev is an EMS (Attractive) system (see Figures 2 and 5).
Propulsion Systems
A conventional rotary electric motor consists of a stator and a rotor. The stator is the stationary outer cylindrical shell containing wire coils that are electrically energized to produce magnetic fields (see Figure 6 to the right).
Figure 6: The stator
A synchronous electric motor consists of a stator comprised of coils energized by three-phase AC current. This arrangement causes the magnetic fields produced by the current flow to rotate around the stator (see Figure 7 below).
Figure 7: The rotating stator fields
If a permanent magnet is placed inside the stator at the center, then the magnet will begin to rotate also, matching the rotation speed of rotating magnetic fields in the stator (synchronous rotation, ie., happening at precisely the same time as the stator rotation). The magnet is called the rotor.
If we replace the magnet with a coil of wire wound around an iron core with the ends of the coil connected together in ashort-circuit, the rotating magnetic fields in the stator will induce an alternating current flow in the coil. The current flow will produce a magnetic field, which will, in turn, interact with the rotating magnetic fields in the stator, just like the permanent magnet did; the coil will synchronously rotate with the stator fields. An AC motor with a coil instead of a magnet for a rotor is called an induction motor, although it is also a synchronous motor.
Thus, all 3-phase AC motors are synchronous motors. The rotor is either a permanent magnet or a coil wound around an iron core. If the motor uses a coil, it is also called an induction motor because electric current is induced in the rotor coil by the rotating stator fields.
If the stator coils of a synchronous motor are laid out flat, the "rotor" will now move linearly along the flat stator. This configuration is called a linear motor, and the "rotor" is called the reaction plate. As with a rotary motor, the reaction plate can be either a permanent magnet, or a coil of copper or aluminum. If the reaction plate is a coil, the motor is called a linear induction motor (LIM). The motors in maglev systems are LIMs. Of course, LIMs are also linear synchronous motors (LSMs).
In the case of a maglev system, the passive reaction plates can be mounted on the car, and the stator coils placed along the guideway (long-stator system), or, the passive reaction plates can be mounted along the guideway with the stator coils placed on the car (short-stator system).
"Long-stator" propulsion, using electrically-powered stator coils along the guideway, appears to be the favored option for high-speed maglev systems. An advantage of this configuration is that no power transfer to the vehicle is necessary, which can be difficult at high speeds. Another advantage is that because the car is passive, it can be lighter, since there are no heavy stator coils on board. Disadvantages are that the stator coils have to extend for the entire length of the guideway. This makes stator costs and the guideway construction costs very high.
"Short-stator" propulsion places the powered stator coils on the car, while the guideway stays passive and simple. Advantages of this configuration are that stator costs are low because the stator doesn't have to extend for the entire length of the guideway, and guideway costs stay low because it is passive. Disadvantages are that power has to supplied to a high-speed, moving vehicle, and the onboard stator increases the vehicle weight which will increase the operating costs of the system.
There is also a third propulsion alternative, which is to use a nonmagnetic energy source (gas turbine or turboprop) to propel the car. There are no stator costs, and both the car and the guideway are passive, but the car would have to carry a jet engine, as well as supplies of fuel. This too, results in a heavy vehicle and reduced operating efficiency.
The ODU Maglev is the less-expensive short-stator system.Guidance Systems
Guidance or steering refers to the sideward forces that are required to make the vehicle follow the guideway. The necessary forces are supplied in an exactly analogous fashion to the suspension forces, either attractive or repulsive. The same electromagnets on board the vehicle, which supply lift, can be used concurrently for guidance, or separate guidance electromagnets can be used.Maglev and U.S. Transportation
Maglev systems could offer an attractive transportation alternative for many time sensitive trips of 100 to 600 miles in length, thereby reducing air and highway congestion, air pollution, and energy use, and releasing slots for more efficient long-haul service at crowded airports. The potential value of maglev technology was recognized in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA).
Before the passage of the ISTEA, Congress had appropriated $26.2 million to identify maglev system concepts for use in the United States and to assess the technical and economic feasibility of these systems. Studies were also directed toward determining the role of maglev in improving intercity transportation in the United States. Subsequently, an additional $9.8 million were appropriated to complete the NMI Studies.Why Maglev?
What are the attributes of maglev that commend its consideration by transportation planners?
Faster trips - high peak speed and high acceleration/braking enable average speeds three to four times the national highway speed limit of 65 mph (30 m/s) and lower door-to-door trip time than high-speed rail or air (for trips under about 300 miles or 500 km). Still higher speeds are feasible. Maglev takes up where high-speed rail leaves off, permitting speeds of 250 to 300 mph (112 to 134 m/s) and higher.
Maglev has high reliability and less susceptible to congestion and weather conditions than air or highway travel. Variance from schedule can average less than one minute based on foreign high-speed rail experience. This means intra and intermodal connecting times can be reduced to a few minutes (rather than the half-hour or more required with airlines and Amtrak at present) and that appointments can safely be scheduled without having to consider delays.
Maglev gives petroleum independence - with respect to air and auto because of Maglev being electrically powered. Petroleum is unnecessary for the production of electricity. In 1990, less than 5 percent of the Nation's electricity was derived from petroleum whereas the petroleum used by both the air and automobile modes comes primarily from foreign sources.
Maglev is less polluting - with respect to air and auto, again because of being electrically powered. Emissions can be controlled more effectively at the source of electric power generation than at the many points of consumption, such as with air and automobile usage
(1) Adapted from "ABOUT: What Is Maglev?",
(http://inventors.about.com/library/inventors/blrailroad3.htm?terms=maglev);
"Locally Commutated Linear Synchronous Motor (LCLSM)", Foster-Miller Corp.
(http://www.foster-miller.com/projectexamples/t_robotics/lclsm.htm);
"Electric Voodoo: It's Done with Magnets!", Dave Althoff, Jr.
(http://capital2.capital.edu/admin-staff/dalthoff/lim.html)
The ODU Maglev Project:
Figure 6
It started about a dozen years ago: engineer Tony Morris envisioned a maglev design that would be less expensive and more efficient than the projects that the Germans and the Japanese were building. He incorporated American Maglev Technology (AMT), Inc., and, with the help the Commonwealth of Virginia Transportation Board, along with Lockheed Martin and Dominion Virginia Power, built a system that was unique in that it was controlled by equipment in the car instead of in the guideway.
This "smart car, dumb guideway" engineering principle resulted in a system that Morris estimated would cost only 15 to 20 million dollars per mile, while the competing German and Japanese designs cost 40 to 100 million dollars per mile. In fact, the existing German, Japanese, and Shanghai trains were actually "showpieces"; they ran well and were impressive, but it was known that they could never be the basis for public transportation systems. Like the Concorde, they were simply too expensive.
The AMT car and guideway were initially developed in Edgewater, Florida. ODU then agreed to host the project to develop the work done to date into a functioning, practical transportation system. The arrangement was that ODU would provide not money, but space on campus; administrative staff, engineering faculty, and graduate student assistance; a one-kilometer elevated maglev guideway on campus, and would also administer the $7 million Commonwealth Transportation Board grant. Much later, ODU faculty became involved in direct, hands-on engineering support.
The car was trucked to ODU in 2002, where it was lifted onto a new guideway 3,200 feet in length, built across the campus, starting near Powhatan Avenue and crossing over Elkhorn Avenue and Hampton Blvd. The guideway in Florida was installed on solid ground, but the ODU guideway was elevated on concrete columns like the rubber-tired conventional monorails in Seattle, WA and Disneyland, FL.
Like any new technology, there were problems. The car elevated properly, but when the propulsion magnets were energized, instead of a smooth ride, the car bumped, rattled, and vibrated. New sensors and control systems were designed and installed. These improved performance somewhat, but didn't totally solve all the vibration problems. It was eventually found that the elevated guideway complicated the system: it vibrated (similar to a violin string) between the vertical columns, adding to the natural vibrations of the car. This didn't happen in Florida because, in that design, the guideway rested on solid ground.
These setbacks, as is to be expected, brought out the usual "I-told-you-so critics" and "experts", carping from the sidelines. Rosanne Runte, President of ODU, finally issued a sharp rebuke, pointing out that all R&D projects are characterized by early efforts that are not fruitful. That is part of the trial-and-error that is the very essence of research science:"If we stopped all research at every university because it did not appear successful initially, many important discoveries that have improved our lives would never have been made. One day, that list just might include magnetic levitation."ODU has administered the Maglev project, but had to provide very little development money of its own. Virtually all of that was supplied by Virginia Dominion Power, the Commonwealth of Virginia, and the Federal Government. In reality, this project is mostly all upside for ODU and the ODU faculty working on the AMT Maglev. If they are successful, it will be a huge advance in maglev technology: a less expensive system that really can provide public transporatation worldwide, and pefected here at ODU. If they are not successful, then they will have done no worse than everybody else, but haven't chewed up the decades of research and billions of dollars that all the other projects have cost.
Professor Thomas Alberts, ODU Aerospace
Engineering Dept: a good chance for a Maglev fix.
Dr. Thomas Alberts, whose team is now directing the ODU Maglev effort, has a unique background for solving the current problems: his specialty is the measurement and computer control of flexible structures. He has edited several books and authored numerous papers on the dynamics and control of flexible spacecraft while performing contract research for NASA as an ODU university professor. Apparently, flexability and resultant vibration is at the root of the troubles with the Maglev. The car itself is flexible, and the interaction between the car and the elevated guideway, which is also flexible in itself, gives rise to complex vibration and flutter of the entire system.
The Alberts team has already reported substantial improvements in the Maglev performance. They can routinely levitate a two-ton test bogie smoothly (the bogie is the undercarriage of the Maglev car that supports the body of the vehicle and also contains the suspension and propulsion magnets; two bogies are used for each car). The nature of short-stator maglev propulsion is that the gap between the stator on the car and the reaction plate on the guideway must be constantly monitored and adjusted to provide a smooth and stable "floating-on-air ride" (2). Adjustments are effected by increasing or decreasing the current flowing through the stator coils. The faster and more precise the adjustments, the smoother and more vibration-free the performance. The original AMT design had six magnets per bogie with a centralized control system. Adjustment and control of the gap have now been improved by letting each individual magnet have its own sensors and controller. The number of sensors have been increased, and the sensors themselves have been upgraded. Finally, Maglev performance has also been improved by reducing the effects of environmental electrical and magnetic noise on the sensors and controllers.
(2) "Maglev Approach Shows Promise", Jim Raper, The Courier, News for ODU Facuty, Staff,
Students, & Friends, August 25, 2006.
The ODU Maglev Project In Pictures:
AMT Maglev on the move
in Florida (click on image
to view video)
ODU visitors at the AMT facility
Guideway beam being lowered into
place near ODU Webb Center
Finished guideway near Webb Center
Pulling out by flatbed from Florida
Arrival at ODU in Virginia
Settling in
Maglev sleeping at ODU
Hard at work at ODU: Dr. Alberts taps the
magnets on the maglev model in the lab
Hard at work at ODU: Professor Alberts and Technical
Assistant Jeremy Roadcap run a simulator test
The ODU Maglev In The News:
1) Virginian Pilot, March 10, 2002: Maglev Train Bound For ODU Takes Shape In Florida
2) Virginian Pilot, June 1, 2004: Special Report: The Maglev Mess
3) Virginian Pilot, June 5, 2004: Maglev Train Hits Bumps With Station Demolition
4) Virginian Pilot, June 14, 2004, Op-Ed by Roseanne Runte, President of ODU: Objection!
Maglev Is Still On Course; Doomsayers Are Premature
5) Virginian Pilot, November 11, 2004: New Technology Puts ODU's Maglev In Line For Test Runs
6) Virginian Pilot, April 15, 2005: Progress On ODU Maglev Still Bumpy
7) Virginian Pilot, Sept. 26, 2005: On A New Track With Maglev, article about Dr. Thomas Alberts
taking over ODU's Maglev project
8) Virginian Pilot, October 25, 2005: ODU Asks For More Time For Its Maglev Program.
9) Virginian Pilot, June 23, 2006: ODU And Its Scientists Kick In Money And Time To Keep ODU
Maglev Afloat
10) Virginian Pilot, August 14, 2006: Trial Run Of ODU Maglev Gets It Off The Ground
11) Virginian Pilot, November 10, 2006: ODU's Maglev Train Passes An Unscheduled Test
12) Virginian Pilot, April 11, 2007: Doesn't Run In Florida.... Stalled At ODU.... Now Maglev Maven
Is In Georgia
About Science and Reason in Hampton Roads (SRHR):
Science and Reason in Hampton Roads (www.ScienceAndReason.org) is an organization devoted to the critical examination of dubious or extraordinary claims. It has organized haunted house investigations, Superstition Celebrations, and talks on topics from UFOs to alternative medicine. SRHR has also advised local officials when pseudoscientific equipment such as "infinite energy" machines and the "human (terrorist) heartbeat detecter" was offered for sale in the Norfolk area.
For more information, contact Larry Weinstein, Professor of Physics and SRHR President, at 757-683-5803 or at weinstei@physics.odu.edu.
