Technology Focus part 2:
Power Transmission and Motion Control

Link to Technology Focus part 1

Clean and Efficient

The European Union's voluntary Motor Challenge Program is a leader in encouraging electric motor manufacturers to increase efficiency. Originally formed to address emissions that may be causing climate change, the group picked up momentum with the dramatic rise in energy costs over the past few years.

Motor Challenge organizers estimate that all electric motors used in industry and buildings account for up to 30 percent of total energy consumption. The motors and the pumps, fans, compressors, and other equipment they power are already highly efficient. Yet Motor Challenge estimates that changes in system design, operation, and maintenance could improve efficiency by 20 to 50 percent.

Smarter motor controls, such as variable speed drives, could go a long way toward improving efficiency. Such drives automatically adjust motor power to keep applications running at optimal levels. For example, a drive could adjust pump speed control flow or pressure. This saves more energy than running the pump at high speeds and using valves to reduce pressure and flow. A recent survey estimates that about 35 percent of all motors in use in the European Union could be retrofitted with variable speed drives.

Emotron AB of Helsingborg, Sweden, is one of many companies that have jumped on the Motor Challenge bandwagon. Its new VSA/VSC variable speed drive is not only a good example of an energy-saving drive, but also shows how engineers can add value with advanced features.

The VSA/VSC series is optimized to match motor speed to load for pump, fan, compressor, mixer, and crane motors ranging in power from 0.18 to 7.5 kilowatts.

In pumps, its sleep function pauses the motor when it doesn't need to run to maintain pressure. It also improves efficiency by automatically rinsing the pump by running it at full speed to clear sludge from the impeller and pipes.

Flexible speed control also improves efficiency by handling dissimilar loads differently. VSA/VSC runs cranes and mixers at constant torque, while running pumps and fans at square torque.

The unit has eight preset speeds. This lets mixers change speeds with viscosity. Fans can bypass speeds that generate resonance frequencies that cause vibration damage, while pumps can avoid friction with double speed ramps.

VSA/VSC initiates protective starts and stops, which minimize mechanical stress and cycle times. Engineers can use this feature to eliminate water hammer damage in pumps without using motor-controlled valves, or to spin start a turned-off fan that is rotating in the wrong direction. The unit's torque boost feature enables it to stop mixers without mechanical brakes.

The compact VSA/VSC fits into DIN rail cabinets. It comes with an electrical interference filter that minimizes installation space. Options include serial, Modbus, and Profibus communications and an I/O expansion board.

Haptics for Fun and Profit

If you think force feedback is reserved only for jetliner controls, surgical training, and bombsights, think again. The new Falcon from Novint Technologies Inc. of Albuquerque, N.M., lists for $239 and has taken the gaming world by storm.

This isn't the first time game makers have attempted to add haptic feedback. Many games use vibrating wheels and guns to provide a more realistic experience. Nintendo Co. Ltd.'s new Wii video game console uses a wireless controller whose accelerometers and infrared detection system enable the system to locate it in virtual space.

The Falcon provides force feedback that Novint founder Tom Anderson compares to high-end haptic systems costing up to $10,000.

While many haptic devices use a single articulating arm, Falcon uses three arms attached to a single grip that moves up, down, left, right, and forward. The grip is interchangeable, so users can switch from one handle to the next (think pistols, swords, and light sabers), depending on the game. Each arm is driven by a small servomotor. Together, they produce up to two pounds of feedback within a 64-cubic-inch working space, 4 inches on a side.

Falcon recalculates feedback every millisecond for a smooth, realistic feel. Anderson opted for a parallel rather than serial communications connection, to speed data transfer cost effectively.

Novint plans to license its haptic technology to non-game software developers. Anderson said Novint has already worked with one medical devices company. Eventually, the Falcon may help engineers get a real handle on new designs before they ever leave the CAD drawing board.

home | features | breaking news | marketplace | departments | about ME back issues | ASME | site search

© 2007 by The American Society of Mechanical Engineers