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Special Report:
ECEs and Biomedicine

April 2004


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For more information, visit the Motion Control Systems Research Group.

A team of undergraduates
is working with ECE researchers to apply a ground-based linear propulsion technology to home elevators. The switched reluctance linear motor system would require just two tracks and a linear motor, eliminating the need for cables, gears, and counter weights. Current would only be excited along the path where the elevator is at any moment. Directly above is a diagram of the flux characteristics.

Designing a $1000 switched-reluctance home elevator

A research team that includes more than 15 undergraduate students is applying Virginia Tech’s PERTS linear propulsion technology to vertical travel – in home elevators, shipboard elevators, and high-rise elevators.

The electric propulsion system using a switched reluctance linear actuator was first developed for a prototype maglev personal transport system.

Space savings from switched reluctance
The application to elevators is very promising because of the space savings that a switched reluctance system could provide, according to Krishnan Ramu, director of the Motion Control Systems Research Group. Linear propulsion elevators would require a small track on two sides and a linear motor, eliminating space-consuming cables, counter weights, and gears.

Small elevators for domestic, shipboard use
Space saving elevators would be of particular benefit for homes, ships, and high-rise buildings, where space becomes a greater premium on higher floors.

“This technology has great potential in the housing market as the baby boomers age and want to adapt their houses,” said Ramu. “Most houses were not built to accommodate the space a conventional elevator would take. With our technology, the required space would be little more than the elevator box itself.”

15x cost reduction goal
His team is currently designing a prototype home elevator system that would cost just $1,000, compared to current home elevator prices of $15,000-$25,000. “The undergraduates in the Virtual Corporation started the project,” Ramu said, “and they are now working with graduate students to build the prototype. They are comfortable with the technology because they have access to earlier switched reluctance prototypes and databases,” he said. “If they don’t understand how it would work, they just go over and look at the functional prototypes.”

Control & technical issues
The team faces technical challenges in adapting the horizontal propulsion to a vertical system, including safety, assembly constraints, and control. “The control issues are critical,” Ramu said, explaining that smooth operation of the elevator and door are more noticeable in elevators than heavy transit systems.

Safety challenges
Safety is also a concern. “Backup operation in case of power failure is a much bigger issue than with the transit system. With the transit system, the vehicles are only a half inch off the ground, but in an elevator, the drop can be dangerous,” Ramu said. “No mishap is acceptable.” Other challenges involve construction and assembly in a tight space.

The team is also exploring elevator technology for the all-electric ship, where a heavier load would be lifted under more rigorous use.

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Last updated: Wed, Jun 9, 2004