AUSTIN, Texas—It’s not a magic bus. But a city bus being overhauled and modified by engineering wizards at The University of Texas at Austin may wind up cutting fuel use, improving air quality, reducing noise and greatly diminishing wear and tear on city streets. Like a magic bus, a certain amount of levitation is involved: the vehicle uses magnetic fields to float a key portion of the engine in mid-air.
The Houston Metropolitan Transportation Authority (Houston MTA) is collaborating with UT Austin’s Center for Electromechanics to develop the advanced technology urban transit bus. The goal is to produce a vehicle that works better for the cities of today and of the future. The new system has been designed using UT Austin computers and components that have been built and tested in UT Austin labs.
Houston MTA is providing the bus and funding the research. Additional funding is being provided by the Department of Transportation and the Defense Advanced Research Projects Agency through the Southern Coalition for Advanced Transportation.
Shirley DeLibreo, president and chief executive officer of Houston MTA, said: “By working with the staff at the University of Texas at Austin, who are doing leading-edge research on vehicles, we can help them put their research into practice and be sure that the people of Houston benefit from advances in technology.”
Dr. Joseph Beno, the UT Austin project manager, said: “It is exciting to be working with a research team to develop a set of advanced technologies that have a sporting chance to save fuel, save roads, reduce noise pollution and reduce air pollution.”
When completed, the vehicle will contain two special technologies used together for the first time to boost fuel efficiency and take the bounce out of the standard city bus. The new system includes advanced flywheel technology plus an electronically controlled suspension system. UT Austin researchers intend this package of technologies to work together to save transit authorities and cities millions of dollars.
Building and testing all of the new components added to the bus will take up to 18 months. The bus then will be returned to Houston for evaluation by transit staff. Here’s how the system works:
- Electronically controlled suspension system
A state-of-the-art, electronically controlled suspension system uses devices called “controlled electromechanical force actuators” to replace the shock absorbers that couple the wheels to the body of the bus. In the electronic system, computer-controlled actuators — sophisticated electromagnets — push wheels down or allow them to rise to provide a smoother ride. The UT Austin research team has successfully installed a similar suspension system on a “HUMVEE,” the military vehicle of Desert Storm fame. Military vehicles need the system to increase speed over rough terrain. In a bus, the benefit is a smoother ride, passenger comfort and an end to excessive force from swaying and bouncing that damages city streets.
- Advanced flywheel technology
When used with a gas or diesel engine in a hybrid electric drive vehicle, advanced flywheel technology allows the engine to operate more efficiently. Efficiency and fuel economy are gained because the engine runs at a more constant speed, rather than slowing or accelerating as all vehicles do in typical urban driving. Advanced flywheel technology allows the vehicle to speed up or slow down without actually changing the speed of the engine itself. This nearly constant engine speed also leads to reductions both in noise and in pollutants that may billow out of all types of vehicles as they make stops and starts.
The flywheel is a simple technology that people have used for thousands of years. It’s as old as the potter’s wheel and is the same technology used in the old phonograph record system. The flywheel used in the bus is 18 inches in diameter and 5.5 inches thick. The flywheel is made of composite material, like that used in the space shuttle or in modern military aircraft. It is mounted on a titanium shaft. The flywheel actually floats — “levitated” by magnetic fields — inside a containment vessel about the size of old-fashioned milk can located in the engine compartment.
As the flywheel floats, it can rotate at a rate of up to 40,000 revolutions per minute. The outermost surface of the wheel is moving at a speed of roughly 2,000 miles per hour. Suspension in a magnetic field in a vacuum means there is little friction involved, and that’s why the flywheel can move so fast.
This high-speed capability allows the flywheel to gather and hold energy that can be used to accelerate the bus without affecting the engine speed. The flywheel itself is accelerated using an electric motor that is powered from the engine — or by recovering energy while the vehicle is braking. The stored energy is taken out of the flywheel through an electric generator similar to the alternator in a car. But it spins much faster. Computer-controlled electronic switches manage the flow of energy into and out of the flywheel system.
For additional information, contact Dr. Joseph H. Beno, program manager of the Electric Vehicle Program at UT Austin’s Center for Electromechanics, (512) 471-4496.